text: /*--------------------------------------------------------------------
   * guc.c
   *
   * Support for grand unified configuration scheme, including SET
   * command, configuration file, and command line options.
   * See src/backend/utils/misc/README for more information.
   *
   *
   * Copyright (c) 2000-2021, PostgreSQL Global Development Group
   * Written by Peter Eisentraut <peter_e@gmx.net>.
   *
   * IDENTIFICATION
   *	  src/backend/utils/misc/guc.c
   *
   *--------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include <ctype.h>
  #include <float.h>
  #include <math.h>
  #include <limits.h>
  #ifdef HAVE_POLL_H
  #include <poll.h>
  #endif
  #ifndef WIN32
  #include <sys/mman.h>
  #endif
  #include <sys/stat.h>
  #ifdef HAVE_SYSLOG
  #include <syslog.h>
  #endif
  #include <unistd.h>
  
  #include "access/commit_ts.h"
  #include "access/gin.h"
  #include "access/rmgr.h"
  #include "access/tableam.h"
  #include "access/toast_compression.h"
  #include "access/transam.h"
  #include "access/twophase.h"
  #include "access/xact.h"
  #include "access/xlog_internal.h"
  #include "catalog/namespace.h"
  #include "catalog/pg_authid.h"
  #include "catalog/storage.h"
  #include "commands/async.h"
  #include "commands/prepare.h"
  #include "commands/trigger.h"
  #include "commands/user.h"
  #include "commands/vacuum.h"
  #include "commands/variable.h"
  #include "common/string.h"
  #include "funcapi.h"
  #include "jit/jit.h"
  #include "libpq/auth.h"
  #include "libpq/libpq.h"
  #include "libpq/pqformat.h"
  #include "miscadmin.h"
  #include "optimizer/cost.h"
  #include "optimizer/geqo.h"
  #include "optimizer/optimizer.h"
  #include "optimizer/paths.h"
  #include "optimizer/planmain.h"
  #include "parser/parse_expr.h"
  #include "parser/parse_type.h"
  #include "parser/parser.h"
  #include "parser/scansup.h"
  #include "pgstat.h"
  #include "postmaster/autovacuum.h"
  #include "postmaster/bgworker_internals.h"
  #include "postmaster/bgwriter.h"
  #include "postmaster/postmaster.h"
  #include "postmaster/syslogger.h"
  #include "postmaster/walwriter.h"
  #include "replication/logicallauncher.h"
  #include "replication/reorderbuffer.h"
  #include "replication/slot.h"
  #include "replication/syncrep.h"
  #include "replication/walreceiver.h"
  #include "replication/walsender.h"
  #include "storage/bufmgr.h"
  #include "storage/dsm_impl.h"
  #include "storage/fd.h"
  #include "storage/large_object.h"
  #include "storage/pg_shmem.h"
  #include "storage/predicate.h"
  #include "storage/proc.h"
  #include "storage/standby.h"
  #include "tcop/tcopprot.h"
  #include "tsearch/ts_cache.h"
  #include "utils/acl.h"
  #include "utils/backend_status.h"
  #include "utils/builtins.h"
  #include "utils/bytea.h"
  #include "utils/float.h"
  #include "utils/guc_tables.h"
  #include "utils/memutils.h"
  #include "utils/pg_locale.h"
  #include "utils/pg_lsn.h"
  #include "utils/plancache.h"
  #include "utils/portal.h"
  #include "utils/ps_status.h"
  #include "utils/queryjumble.h"
  #include "utils/rls.h"
  #include "utils/snapmgr.h"
  #include "utils/tzparser.h"
  #include "utils/inval.h"
  #include "utils/varlena.h"
  #include "utils/xml.h"
  
  #ifndef PG_KRB_SRVTAB
  #define PG_KRB_SRVTAB ""
  #endif
  
  #define CONFIG_FILENAME "postgresql.conf"
  #define HBA_FILENAME	"pg_hba.conf"
  #define IDENT_FILENAME	"pg_ident.conf"
  
  #ifdef EXEC_BACKEND
  #define CONFIG_EXEC_PARAMS "global/config_exec_params"
  #define CONFIG_EXEC_PARAMS_NEW "global/config_exec_params.new"
  #endif
  
  /*
   * Precision with which REAL type guc values are to be printed for GUC
   * serialization.
   */
  #define REALTYPE_PRECISION 17
  
  /* XXX these should appear in other modules' header files */
  extern bool Log_disconnections;
  extern int	CommitDelay;
  extern int	CommitSiblings;
  extern char *default_tablespace;
  extern char *temp_tablespaces;
  extern bool ignore_checksum_failure;
  extern bool ignore_invalid_pages;
  extern bool synchronize_seqscans;
  
  #ifdef TRACE_SYNCSCAN
  extern bool trace_syncscan;
  #endif
  #ifdef DEBUG_BOUNDED_SORT
  extern bool optimize_bounded_sort;
  #endif
  
  static int	GUC_check_errcode_value;
  
  /* global variables for check hook support */
  char	   *GUC_check_errmsg_string;
  char	   *GUC_check_errdetail_string;
  char	   *GUC_check_errhint_string;
  
  static void do_serialize(char **destptr, Size *maxbytes, const char *fmt,...) pg_attribute_printf(3, 4);
  
  static void set_config_sourcefile(const char *name, char *sourcefile,
  								  int sourceline);
  static bool call_bool_check_hook(struct config_bool *conf, bool *newval,
  								 void **extra, GucSource source, int elevel);
  static bool call_int_check_hook(struct config_int *conf, int *newval,
  								void **extra, GucSource source, int elevel);
  static bool call_real_check_hook(struct config_real *conf, double *newval,
  								 void **extra, GucSource source, int elevel);
  static bool call_string_check_hook(struct config_string *conf, char **newval,
  								   void **extra, GucSource source, int elevel);
  static bool call_enum_check_hook(struct config_enum *conf, int *newval,
  								 void **extra, GucSource source, int elevel);
  
  static bool check_log_destination(char **newval, void **extra, GucSource source);
  static void assign_log_destination(const char *newval, void *extra);
  
  static bool check_wal_consistency_checking(char **newval, void **extra,
  										   GucSource source);
  static void assign_wal_consistency_checking(const char *newval, void *extra);
  
  #ifdef HAVE_SYSLOG
  static int	syslog_facility = LOG_LOCAL0;
  #else
  static int	syslog_facility = 0;
  #endif
  
  static void assign_syslog_facility(int newval, void *extra);
  static void assign_syslog_ident(const char *newval, void *extra);
  static void assign_session_replication_role(int newval, void *extra);
  static bool check_temp_buffers(int *newval, void **extra, GucSource source);
  static bool check_bonjour(bool *newval, void **extra, GucSource source);
  static bool check_ssl(bool *newval, void **extra, GucSource source);
  static bool check_stage_log_stats(bool *newval, void **extra, GucSource source);
  static bool check_log_stats(bool *newval, void **extra, GucSource source);
  static bool check_canonical_path(char **newval, void **extra, GucSource source);
  static bool check_timezone_abbreviations(char **newval, void **extra, GucSource source);
  static void assign_timezone_abbreviations(const char *newval, void *extra);
  static void pg_timezone_abbrev_initialize(void);
  static const char *show_archive_command(void);
  static void assign_tcp_keepalives_idle(int newval, void *extra);
  static void assign_tcp_keepalives_interval(int newval, void *extra);
  static void assign_tcp_keepalives_count(int newval, void *extra);
  static void assign_tcp_user_timeout(int newval, void *extra);
  static const char *show_tcp_keepalives_idle(void);
  static const char *show_tcp_keepalives_interval(void);
  static const char *show_tcp_keepalives_count(void);
  static const char *show_tcp_user_timeout(void);
  static bool check_maxconnections(int *newval, void **extra, GucSource source);
  static bool check_max_worker_processes(int *newval, void **extra, GucSource source);
  static bool check_autovacuum_max_workers(int *newval, void **extra, GucSource source);
  static bool check_max_wal_senders(int *newval, void **extra, GucSource source);
  static bool check_autovacuum_work_mem(int *newval, void **extra, GucSource source);
  static bool check_effective_io_concurrency(int *newval, void **extra, GucSource source);
  static bool check_maintenance_io_concurrency(int *newval, void **extra, GucSource source);
  static bool check_huge_page_size(int *newval, void **extra, GucSource source);
  static bool check_client_connection_check_interval(int *newval, void **extra, GucSource source);
  static void assign_pgstat_temp_directory(const char *newval, void *extra);
  static bool check_application_name(char **newval, void **extra, GucSource source);
  static void assign_application_name(const char *newval, void *extra);
  static bool check_cluster_name(char **newval, void **extra, GucSource source);
  static const char *show_unix_socket_permissions(void);
  static const char *show_log_file_mode(void);
  static const char *show_data_directory_mode(void);
  static const char *show_in_hot_standby(void);
  static bool check_backtrace_functions(char **newval, void **extra, GucSource source);
  static void assign_backtrace_functions(const char *newval, void *extra);
  static bool check_recovery_target_timeline(char **newval, void **extra, GucSource source);
  static void assign_recovery_target_timeline(const char *newval, void *extra);
  static bool check_recovery_target(char **newval, void **extra, GucSource source);
  static void assign_recovery_target(const char *newval, void *extra);
  static bool check_recovery_target_xid(char **newval, void **extra, GucSource source);
  static void assign_recovery_target_xid(const char *newval, void *extra);
  static bool check_recovery_target_time(char **newval, void **extra, GucSource source);
  static void assign_recovery_target_time(const char *newval, void *extra);
  static bool check_recovery_target_name(char **newval, void **extra, GucSource source);
  static void assign_recovery_target_name(const char *newval, void *extra);
  static bool check_recovery_target_lsn(char **newval, void **extra, GucSource source);
  static void assign_recovery_target_lsn(const char *newval, void *extra);
  static bool check_primary_slot_name(char **newval, void **extra, GucSource source);
  static bool check_default_with_oids(bool *newval, void **extra, GucSource source);
  
  /* Private functions in guc-file.l that need to be called from guc.c */
  static ConfigVariable *ProcessConfigFileInternal(GucContext context,
  												 bool applySettings, int elevel);
  
  
  /*
   * Options for enum values defined in this module.
   *
   * NOTE! Option values may not contain double quotes!
   */
  
  static const struct config_enum_entry bytea_output_options[] = {
  	{"escape", BYTEA_OUTPUT_ESCAPE, false},
  	{"hex", BYTEA_OUTPUT_HEX, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(bytea_output_options) == (BYTEA_OUTPUT_HEX + 2),
  				 "array length mismatch");
  
  /*
   * We have different sets for client and server message level options because
   * they sort slightly different (see "log" level), and because "fatal"/"panic"
   * aren't sensible for client_min_messages.
   */
  static const struct config_enum_entry client_message_level_options[] = {
  	{"debug5", DEBUG5, false},
  	{"debug4", DEBUG4, false},
  	{"debug3", DEBUG3, false},
  	{"debug2", DEBUG2, false},
  	{"debug1", DEBUG1, false},
  	{"debug", DEBUG2, true},
  	{"log", LOG, false},
  	{"info", INFO, true},
  	{"notice", NOTICE, false},
  	{"warning", WARNING, false},
  	{"error", ERROR, false},
  	{NULL, 0, false}
  };
  
  static const struct config_enum_entry server_message_level_options[] = {
  	{"debug5", DEBUG5, false},
  	{"debug4", DEBUG4, false},
  	{"debug3", DEBUG3, false},
  	{"debug2", DEBUG2, false},
  	{"debug1", DEBUG1, false},
  	{"debug", DEBUG2, true},
  	{"info", INFO, false},
  	{"notice", NOTICE, false},
  	{"warning", WARNING, false},
  	{"error", ERROR, false},
  	{"log", LOG, false},
  	{"fatal", FATAL, false},
  	{"panic", PANIC, false},
  	{NULL, 0, false}
  };
  
  static const struct config_enum_entry intervalstyle_options[] = {
  	{"postgres", INTSTYLE_POSTGRES, false},
  	{"postgres_verbose", INTSTYLE_POSTGRES_VERBOSE, false},
  	{"sql_standard", INTSTYLE_SQL_STANDARD, false},
  	{"iso_8601", INTSTYLE_ISO_8601, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(intervalstyle_options) == (INTSTYLE_ISO_8601 + 2),
  				 "array length mismatch");
  
  static const struct config_enum_entry log_error_verbosity_options[] = {
  	{"terse", PGERROR_TERSE, false},
  	{"default", PGERROR_DEFAULT, false},
  	{"verbose", PGERROR_VERBOSE, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(log_error_verbosity_options) == (PGERROR_VERBOSE + 2),
  				 "array length mismatch");
  
  static const struct config_enum_entry log_statement_options[] = {
  	{"none", LOGSTMT_NONE, false},
  	{"ddl", LOGSTMT_DDL, false},
  	{"mod", LOGSTMT_MOD, false},
  	{"all", LOGSTMT_ALL, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(log_statement_options) == (LOGSTMT_ALL + 2),
  				 "array length mismatch");
  
  static const struct config_enum_entry isolation_level_options[] = {
  	{"serializable", XACT_SERIALIZABLE, false},
  	{"repeatable read", XACT_REPEATABLE_READ, false},
  	{"read committed", XACT_READ_COMMITTED, false},
  	{"read uncommitted", XACT_READ_UNCOMMITTED, false},
  	{NULL, 0}
  };
  
  static const struct config_enum_entry session_replication_role_options[] = {
  	{"origin", SESSION_REPLICATION_ROLE_ORIGIN, false},
  	{"replica", SESSION_REPLICATION_ROLE_REPLICA, false},
  	{"local", SESSION_REPLICATION_ROLE_LOCAL, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(session_replication_role_options) == (SESSION_REPLICATION_ROLE_LOCAL + 2),
  				 "array length mismatch");
  
  static const struct config_enum_entry syslog_facility_options[] = {
  #ifdef HAVE_SYSLOG
  	{"local0", LOG_LOCAL0, false},
  	{"local1", LOG_LOCAL1, false},
  	{"local2", LOG_LOCAL2, false},
  	{"local3", LOG_LOCAL3, false},
  	{"local4", LOG_LOCAL4, false},
  	{"local5", LOG_LOCAL5, false},
  	{"local6", LOG_LOCAL6, false},
  	{"local7", LOG_LOCAL7, false},
  #else
  	{"none", 0, false},
  #endif
  	{NULL, 0}
  };
  
  static const struct config_enum_entry track_function_options[] = {
  	{"none", TRACK_FUNC_OFF, false},
  	{"pl", TRACK_FUNC_PL, false},
  	{"all", TRACK_FUNC_ALL, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(track_function_options) == (TRACK_FUNC_ALL + 2),
  				 "array length mismatch");
  
  static const struct config_enum_entry xmlbinary_options[] = {
  	{"base64", XMLBINARY_BASE64, false},
  	{"hex", XMLBINARY_HEX, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(xmlbinary_options) == (XMLBINARY_HEX + 2),
  				 "array length mismatch");
  
  static const struct config_enum_entry xmloption_options[] = {
  	{"content", XMLOPTION_CONTENT, false},
  	{"document", XMLOPTION_DOCUMENT, false},
  	{NULL, 0, false}
  };
  
  static const struct config_enum_entry nlslength_options[] = {
  	{"none", NLSLENGTH_NONE, false},
  	{"byte", NLSLENGTH_BYTE, false},
  	{"char", NLSLENGTH_CHAR, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(xmloption_options) == (XMLOPTION_CONTENT + 2),
  				 "array length mismatch");
  
  /*
   * Although only "on", "off", and "safe_encoding" are documented, we
   * accept all the likely variants of "on" and "off".
   */
  static const struct config_enum_entry backslash_quote_options[] = {
  	{"safe_encoding", BACKSLASH_QUOTE_SAFE_ENCODING, false},
  	{"on", BACKSLASH_QUOTE_ON, false},
  	{"off", BACKSLASH_QUOTE_OFF, false},
  	{"true", BACKSLASH_QUOTE_ON, true},
  	{"false", BACKSLASH_QUOTE_OFF, true},
  	{"yes", BACKSLASH_QUOTE_ON, true},
  	{"no", BACKSLASH_QUOTE_OFF, true},
  	{"1", BACKSLASH_QUOTE_ON, true},
  	{"0", BACKSLASH_QUOTE_OFF, true},
  	{NULL, 0, false}
  };
  
  /*
   * Although only "on", "off", and "auto" are documented, we accept
   * all the likely variants of "on" and "off".
   */
  static const struct config_enum_entry compute_query_id_options[] = {
  	{"auto", COMPUTE_QUERY_ID_AUTO, false},
  	{"on", COMPUTE_QUERY_ID_ON, false},
  	{"off", COMPUTE_QUERY_ID_OFF, false},
  	{"true", COMPUTE_QUERY_ID_ON, true},
  	{"false", COMPUTE_QUERY_ID_OFF, true},
  	{"yes", COMPUTE_QUERY_ID_ON, true},
  	{"no", COMPUTE_QUERY_ID_OFF, true},
  	{"1", COMPUTE_QUERY_ID_ON, true},
  	{"0", COMPUTE_QUERY_ID_OFF, true},
  	{NULL, 0, false}
  };
  
  /*
   * Although only "on", "off", and "partition" are documented, we
   * accept all the likely variants of "on" and "off".
   */
  static const struct config_enum_entry constraint_exclusion_options[] = {
  	{"partition", CONSTRAINT_EXCLUSION_PARTITION, false},
  	{"on", CONSTRAINT_EXCLUSION_ON, false},
  	{"off", CONSTRAINT_EXCLUSION_OFF, false},
  	{"true", CONSTRAINT_EXCLUSION_ON, true},
  	{"false", CONSTRAINT_EXCLUSION_OFF, true},
  	{"yes", CONSTRAINT_EXCLUSION_ON, true},
  	{"no", CONSTRAINT_EXCLUSION_OFF, true},
  	{"1", CONSTRAINT_EXCLUSION_ON, true},
  	{"0", CONSTRAINT_EXCLUSION_OFF, true},
  	{NULL, 0, false}
  };
  
  /*
   * Although only "on", "off", "remote_apply", "remote_write", and "local" are
   * documented, we accept all the likely variants of "on" and "off".
   */
  static const struct config_enum_entry synchronous_commit_options[] = {
  	{"local", SYNCHRONOUS_COMMIT_LOCAL_FLUSH, false},
  	{"remote_write", SYNCHRONOUS_COMMIT_REMOTE_WRITE, false},
  	{"remote_apply", SYNCHRONOUS_COMMIT_REMOTE_APPLY, false},
  	{"on", SYNCHRONOUS_COMMIT_ON, false},
  	{"off", SYNCHRONOUS_COMMIT_OFF, false},
  	{"true", SYNCHRONOUS_COMMIT_ON, true},
  	{"false", SYNCHRONOUS_COMMIT_OFF, true},
  	{"yes", SYNCHRONOUS_COMMIT_ON, true},
  	{"no", SYNCHRONOUS_COMMIT_OFF, true},
  	{"1", SYNCHRONOUS_COMMIT_ON, true},
  	{"0", SYNCHRONOUS_COMMIT_OFF, true},
  	{NULL, 0, false}
  };
  
  /*
   * Although only "on", "off", "try" are documented, we accept all the likely
   * variants of "on" and "off".
   */
  static const struct config_enum_entry huge_pages_options[] = {
  	{"off", HUGE_PAGES_OFF, false},
  	{"on", HUGE_PAGES_ON, false},
  	{"try", HUGE_PAGES_TRY, false},
  	{"true", HUGE_PAGES_ON, true},
  	{"false", HUGE_PAGES_OFF, true},
  	{"yes", HUGE_PAGES_ON, true},
  	{"no", HUGE_PAGES_OFF, true},
  	{"1", HUGE_PAGES_ON, true},
  	{"0", HUGE_PAGES_OFF, true},
  	{NULL, 0, false}
  };
  
  static const struct config_enum_entry force_parallel_mode_options[] = {
  	{"off", FORCE_PARALLEL_OFF, false},
  	{"on", FORCE_PARALLEL_ON, false},
  	{"regress", FORCE_PARALLEL_REGRESS, false},
  	{"true", FORCE_PARALLEL_ON, true},
  	{"false", FORCE_PARALLEL_OFF, true},
  	{"yes", FORCE_PARALLEL_ON, true},
  	{"no", FORCE_PARALLEL_OFF, true},
  	{"1", FORCE_PARALLEL_ON, true},
  	{"0", FORCE_PARALLEL_OFF, true},
  	{NULL, 0, false}
  };
  
  static const struct config_enum_entry plan_cache_mode_options[] = {
  	{"auto", PLAN_CACHE_MODE_AUTO, false},
  	{"force_generic_plan", PLAN_CACHE_MODE_FORCE_GENERIC_PLAN, false},
  	{"force_custom_plan", PLAN_CACHE_MODE_FORCE_CUSTOM_PLAN, false},
  	{NULL, 0, false}
  };
  
  static const struct config_enum_entry password_encryption_options[] = {
  	{"md5", PASSWORD_TYPE_MD5, false},
  	{"scram-sha-256", PASSWORD_TYPE_SCRAM_SHA_256, false},
  	{NULL, 0, false}
  };
  
  const struct config_enum_entry ssl_protocol_versions_info[] = {
  	{"", PG_TLS_ANY, false},
  	{"TLSv1", PG_TLS1_VERSION, false},
  	{"TLSv1.1", PG_TLS1_1_VERSION, false},
  	{"TLSv1.2", PG_TLS1_2_VERSION, false},
  	{"TLSv1.3", PG_TLS1_3_VERSION, false},
  	{NULL, 0, false}
  };
  
  StaticAssertDecl(lengthof(ssl_protocol_versions_info) == (PG_TLS1_3_VERSION + 2),
  				 "array length mismatch");
  
  static struct config_enum_entry recovery_init_sync_method_options[] = {
  	{"fsync", RECOVERY_INIT_SYNC_METHOD_FSYNC, false},
  #ifdef HAVE_SYNCFS
  	{"syncfs", RECOVERY_INIT_SYNC_METHOD_SYNCFS, false},
  #endif
  	{NULL, 0, false}
  };
  
  static struct config_enum_entry shared_memory_options[] = {
  #ifndef WIN32
  	{"sysv", SHMEM_TYPE_SYSV, false},
  #endif
  #ifndef EXEC_BACKEND
  	{"mmap", SHMEM_TYPE_MMAP, false},
  #endif
  #ifdef WIN32
  	{"windows", SHMEM_TYPE_WINDOWS, false},
  #endif
  	{NULL, 0, false}
  };
  
  static struct config_enum_entry default_toast_compression_options[] = {
  	{"pglz", TOAST_PGLZ_COMPRESSION, false},
  #ifdef  USE_LZ4
  	{"lz4", TOAST_LZ4_COMPRESSION, false},
  #endif
  	{NULL, 0, false}
  };
  
  /*
   * Options for enum values stored in other modules
   */
  extern const struct config_enum_entry wal_level_options[];
  extern const struct config_enum_entry archive_mode_options[];
  extern const struct config_enum_entry recovery_target_action_options[];
  extern const struct config_enum_entry sync_method_options[];
  extern const struct config_enum_entry dynamic_shared_memory_options[];
  
  /*
   * GUC option variables that are exported from this module
   */
  bool		log_duration = false;
  bool		Debug_print_plan = false;
  bool		Debug_print_parse = false;
  bool		Debug_print_rewritten = false;
  bool		Debug_pretty_print = true;
  
  bool		log_parser_stats = false;
  bool		log_planner_stats = false;
  bool		log_executor_stats = false;
  bool		log_statement_stats = false;	/* this is sort of all three above
  											 * together */
  bool		log_btree_build_stats = false;
  char	   *event_source;
  
  bool		row_security;
  bool		check_function_bodies = true;
  
  /*
   * This GUC exists solely for backward compatibility, check its definition for
   * details.
   */
  bool		default_with_oids = false;
  bool		session_auth_is_superuser;
  
  int			log_min_error_statement = ERROR;
  int			log_min_messages = WARNING;
  int			client_min_messages = NOTICE;
  int			log_min_duration_sample = -1;
  int			log_min_duration_statement = -1;
  int			log_parameter_max_length = -1;
  int			log_parameter_max_length_on_error = 0;
  int			log_temp_files = -1;
  double		log_statement_sample_rate = 1.0;
  double		log_xact_sample_rate = 0;
  int			trace_recovery_messages = LOG;
  char	   *backtrace_functions;
  char	   *backtrace_symbol_list;
  
  int			temp_file_limit = -1;
  
  int			num_temp_buffers = 1024;
  
  char	   *cluster_name = "";
  char	   *ConfigFileName;
  char	   *HbaFileName;
  char	   *IdentFileName;
  char	   *external_pid_file;
  
  char	   *pgstat_temp_directory;
  
  char	   *application_name;
  
  int			tcp_keepalives_idle;
  int			tcp_keepalives_interval;
  int			tcp_keepalives_count;
  int			tcp_user_timeout;
  
  /*
   * SSL renegotiation was been removed in PostgreSQL 9.5, but we tolerate it
   * being set to zero (meaning never renegotiate) for backward compatibility.
   * This avoids breaking compatibility with clients that have never supported
   * renegotiation and therefore always try to zero it.
   */
  int			ssl_renegotiation_limit;
  
  /*
   * This really belongs in pg_shmem.c, but is defined here so that it doesn't
   * need to be duplicated in all the different implementations of pg_shmem.c.
   */
  int			huge_pages;
  int			huge_page_size;
  
  /*
   * These variables are all dummies that don't do anything, except in some
   * cases provide the value for SHOW to display.  The real state is elsewhere
   * and is kept in sync by assign_hooks.
   */
  static char *syslog_ident_str;
  static double phony_random_seed;
  static char *client_encoding_string;
  static char *datestyle_string;
  static char *locale_collate;
  static char *locale_ctype;
  static char *server_encoding_string;
  static char *server_version_string;
  static int	server_version_num;
  static char *timezone_string;
  static char *log_timezone_string;
  static char *timezone_abbreviations_string;
  static char *data_directory;
  static char *session_authorization_string;
  static int	max_function_args;
  static int	max_index_keys;
  static int	max_identifier_length;
  static int	block_size;
  static int	segment_size;
  static int	wal_block_size;
  static bool data_checksums;
  static bool integer_datetimes;
  static bool assert_enabled;
  static bool in_hot_standby;
  static char *recovery_target_timeline_string;
  static char *recovery_target_string;
  static char *recovery_target_xid_string;
  static char *recovery_target_name_string;
  static char *recovery_target_lsn_string;
  
  
  /* should be static, but commands/variable.c needs to get at this */
  char	   *role_string;
  
  int nls_length_semantics;
  int		compatible_db;
  
  
  static struct config_enum_entry compat_options[] = {
  	{"postgres", COMPATIBLE_NONE, false},
  	{"oracle", COMPATIBLE_ORA, false},
  	{NULL, 0, false}
  };
  
  /*
   * Displayable names for context types (enum GucContext)
   *
   * Note: these strings are deliberately not localized.
   */
  const char *const GucContext_Names[] =
  {
  	 /* PGC_INTERNAL */ "internal",
  	 /* PGC_POSTMASTER */ "postmaster",
  	 /* PGC_SIGHUP */ "sighup",
  	 /* PGC_SU_BACKEND */ "superuser-backend",
  	 /* PGC_BACKEND */ "backend",
  	 /* PGC_SUSET */ "superuser",
  	 /* PGC_USERSET */ "user"
  };
  
  StaticAssertDecl(lengthof(GucContext_Names) == (PGC_USERSET + 1),
  				 "array length mismatch");
  
  /*
   * Displayable names for source types (enum GucSource)
   *
   * Note: these strings are deliberately not localized.
   */
  const char *const GucSource_Names[] =
  {
  	 /* PGC_S_DEFAULT */ "default",
  	 /* PGC_S_DYNAMIC_DEFAULT */ "default",
  	 /* PGC_S_ENV_VAR */ "environment variable",
  	 /* PGC_S_FILE */ "configuration file",
  	 /* PGC_S_ARGV */ "command line",
  	 /* PGC_S_GLOBAL */ "global",
  	 /* PGC_S_DATABASE */ "database",
  	 /* PGC_S_USER */ "user",
  	 /* PGC_S_DATABASE_USER */ "database user",
  	 /* PGC_S_CLIENT */ "client",
  	 /* PGC_S_OVERRIDE */ "override",
  	 /* PGC_S_INTERACTIVE */ "interactive",
  	 /* PGC_S_TEST */ "test",
  	 /* PGC_S_SESSION */ "session"
  };
  
  StaticAssertDecl(lengthof(GucSource_Names) == (PGC_S_SESSION + 1),
  				 "array length mismatch");
  
  /*
   * Displayable names for the groupings defined in enum config_group
   */
  const char *const config_group_names[] =
  {
  	/* UNGROUPED */
  	gettext_noop("Ungrouped"),
  	/* FILE_LOCATIONS */
  	gettext_noop("File Locations"),
  	/* CONN_AUTH_SETTINGS */
  	gettext_noop("Connections and Authentication / Connection Settings"),
  	/* CONN_AUTH_AUTH */
  	gettext_noop("Connections and Authentication / Authentication"),
  	/* CONN_AUTH_SSL */
  	gettext_noop("Connections and Authentication / SSL"),
  	/* RESOURCES_MEM */
  	gettext_noop("Resource Usage / Memory"),
  	/* RESOURCES_DISK */
  	gettext_noop("Resource Usage / Disk"),
  	/* RESOURCES_KERNEL */
  	gettext_noop("Resource Usage / Kernel Resources"),
  	/* RESOURCES_VACUUM_DELAY */
  	gettext_noop("Resource Usage / Cost-Based Vacuum Delay"),
  	/* RESOURCES_BGWRITER */
  	gettext_noop("Resource Usage / Background Writer"),
  	/* RESOURCES_ASYNCHRONOUS */
  	gettext_noop("Resource Usage / Asynchronous Behavior"),
  	/* WAL_SETTINGS */
  	gettext_noop("Write-Ahead Log / Settings"),
  	/* WAL_CHECKPOINTS */
  	gettext_noop("Write-Ahead Log / Checkpoints"),
  	/* WAL_ARCHIVING */
  	gettext_noop("Write-Ahead Log / Archiving"),
  	/* WAL_ARCHIVE_RECOVERY */
  	gettext_noop("Write-Ahead Log / Archive Recovery"),
  	/* WAL_RECOVERY_TARGET */
  	gettext_noop("Write-Ahead Log / Recovery Target"),
  	/* REPLICATION_SENDING */
  	gettext_noop("Replication / Sending Servers"),
  	/* REPLICATION_PRIMARY */
  	gettext_noop("Replication / Primary Server"),
  	/* REPLICATION_STANDBY */
  	gettext_noop("Replication / Standby Servers"),
  	/* REPLICATION_SUBSCRIBERS */
  	gettext_noop("Replication / Subscribers"),
  	/* QUERY_TUNING_METHOD */
  	gettext_noop("Query Tuning / Planner Method Configuration"),
  	/* QUERY_TUNING_COST */
  	gettext_noop("Query Tuning / Planner Cost Constants"),
  	/* QUERY_TUNING_GEQO */
  	gettext_noop("Query Tuning / Genetic Query Optimizer"),
  	/* QUERY_TUNING_OTHER */
  	gettext_noop("Query Tuning / Other Planner Options"),
  	/* LOGGING_WHERE */
  	gettext_noop("Reporting and Logging / Where to Log"),
  	/* LOGGING_WHEN */
  	gettext_noop("Reporting and Logging / When to Log"),
  	/* LOGGING_WHAT */
  	gettext_noop("Reporting and Logging / What to Log"),
  	/* PROCESS_TITLE */
  	gettext_noop("Reporting and Logging / Process Title"),
  	/* STATS_MONITORING */
  	gettext_noop("Statistics / Monitoring"),
  	/* STATS_COLLECTOR */
  	gettext_noop("Statistics / Query and Index Statistics Collector"),
  	/* AUTOVACUUM */
  	gettext_noop("Autovacuum"),
  	/* CLIENT_CONN_STATEMENT */
  	gettext_noop("Client Connection Defaults / Statement Behavior"),
  	/* CLIENT_CONN_LOCALE */
  	gettext_noop("Client Connection Defaults / Locale and Formatting"),
  	/* CLIENT_CONN_PRELOAD */
  	gettext_noop("Client Connection Defaults / Shared Library Preloading"),
  	/* CLIENT_CONN_OTHER */
  	gettext_noop("Client Connection Defaults / Other Defaults"),
  	/* LOCK_MANAGEMENT */
  	gettext_noop("Lock Management"),
  	/* COMPAT_OPTIONS_PREVIOUS */
  	gettext_noop("Version and Platform Compatibility / Previous PostgreSQL Versions"),
  	/* COMPAT_OPTIONS_CLIENT */
  	gettext_noop("Version and Platform Compatibility / Other Platforms and Clients"),
  	/* ERROR_HANDLING */
  	gettext_noop("Error Handling"),
  	/* PRESET_OPTIONS */
  	gettext_noop("Preset Options"),
  	/* CUSTOM_OPTIONS */
  	gettext_noop("Customized Options"),
  	/* DEVELOPER_OPTIONS */
  	gettext_noop("Developer Options"),
  	/* help_config wants this array to be null-terminated */
  	NULL
  };
  
  StaticAssertDecl(lengthof(config_group_names) == (DEVELOPER_OPTIONS + 2),
  				 "array length mismatch");
  
  /*
   * Displayable names for GUC variable types (enum config_type)
   *
   * Note: these strings are deliberately not localized.
   */
  const char *const config_type_names[] =
  {
  	 /* PGC_BOOL */ "bool",
  	 /* PGC_INT */ "integer",
  	 /* PGC_REAL */ "real",
  	 /* PGC_STRING */ "string",
  	 /* PGC_ENUM */ "enum"
  };
  
  StaticAssertDecl(lengthof(config_type_names) == (PGC_ENUM + 1),
  				 "array length mismatch");
  
  /*
   * Unit conversion tables.
   *
   * There are two tables, one for memory units, and another for time units.
   * For each supported conversion from one unit to another, we have an entry
   * in the table.
   *
   * To keep things simple, and to avoid possible roundoff error,
   * conversions are never chained.  There needs to be a direct conversion
   * between all units (of the same type).
   *
   * The conversions for each base unit must be kept in order from greatest to
   * smallest human-friendly unit; convert_xxx_from_base_unit() rely on that.
   * (The order of the base-unit groups does not matter.)
   */
  #define MAX_UNIT_LEN		3	/* length of longest recognized unit string */
  
  typedef struct
  {
  	char		unit[MAX_UNIT_LEN + 1]; /* unit, as a string, like "kB" or
  										 * "min" */
  	int			base_unit;		/* GUC_UNIT_XXX */
  	double		multiplier;		/* Factor for converting unit -> base_unit */
  } unit_conversion;
  
  /* Ensure that the constants in the tables don't overflow or underflow */
  #if BLCKSZ < 1024 || BLCKSZ > (1024*1024)
  #error BLCKSZ must be between 1KB and 1MB
  #endif
  #if XLOG_BLCKSZ < 1024 || XLOG_BLCKSZ > (1024*1024)
  #error XLOG_BLCKSZ must be between 1KB and 1MB
  #endif
  
  static const char *memory_units_hint = gettext_noop("Valid units for this parameter are \"B\", \"kB\", \"MB\", \"GB\", and \"TB\".");
  
  static const unit_conversion memory_unit_conversion_table[] =
  {
  	{"TB", GUC_UNIT_BYTE, 1024.0 * 1024.0 * 1024.0 * 1024.0},
  	{"GB", GUC_UNIT_BYTE, 1024.0 * 1024.0 * 1024.0},
  	{"MB", GUC_UNIT_BYTE, 1024.0 * 1024.0},
  	{"kB", GUC_UNIT_BYTE, 1024.0},
  	{"B", GUC_UNIT_BYTE, 1.0},
  
  	{"TB", GUC_UNIT_KB, 1024.0 * 1024.0 * 1024.0},
  	{"GB", GUC_UNIT_KB, 1024.0 * 1024.0},
  	{"MB", GUC_UNIT_KB, 1024.0},
  	{"kB", GUC_UNIT_KB, 1.0},
  	{"B", GUC_UNIT_KB, 1.0 / 1024.0},
  
  	{"TB", GUC_UNIT_MB, 1024.0 * 1024.0},
  	{"GB", GUC_UNIT_MB, 1024.0},
  	{"MB", GUC_UNIT_MB, 1.0},
  	{"kB", GUC_UNIT_MB, 1.0 / 1024.0},
  	{"B", GUC_UNIT_MB, 1.0 / (1024.0 * 1024.0)},
  
  	{"TB", GUC_UNIT_BLOCKS, (1024.0 * 1024.0 * 1024.0) / (BLCKSZ / 1024)},
  	{"GB", GUC_UNIT_BLOCKS, (1024.0 * 1024.0) / (BLCKSZ / 1024)},
  	{"MB", GUC_UNIT_BLOCKS, 1024.0 / (BLCKSZ / 1024)},
  	{"kB", GUC_UNIT_BLOCKS, 1.0 / (BLCKSZ / 1024)},
  	{"B", GUC_UNIT_BLOCKS, 1.0 / BLCKSZ},
  
  	{"TB", GUC_UNIT_XBLOCKS, (1024.0 * 1024.0 * 1024.0) / (XLOG_BLCKSZ / 1024)},
  	{"GB", GUC_UNIT_XBLOCKS, (1024.0 * 1024.0) / (XLOG_BLCKSZ / 1024)},
  	{"MB", GUC_UNIT_XBLOCKS, 1024.0 / (XLOG_BLCKSZ / 1024)},
  	{"kB", GUC_UNIT_XBLOCKS, 1.0 / (XLOG_BLCKSZ / 1024)},
  	{"B", GUC_UNIT_XBLOCKS, 1.0 / XLOG_BLCKSZ},
  
  	{""}						/* end of table marker */
  };
  
  static const char *time_units_hint = gettext_noop("Valid units for this parameter are \"us\", \"ms\", \"s\", \"min\", \"h\", and \"d\".");
  
  static const unit_conversion time_unit_conversion_table[] =
  {
  	{"d", GUC_UNIT_MS, 1000 * 60 * 60 * 24},
  	{"h", GUC_UNIT_MS, 1000 * 60 * 60},
  	{"min", GUC_UNIT_MS, 1000 * 60},
  	{"s", GUC_UNIT_MS, 1000},
  	{"ms", GUC_UNIT_MS, 1},
  	{"us", GUC_UNIT_MS, 1.0 / 1000},
  
  	{"d", GUC_UNIT_S, 60 * 60 * 24},
  	{"h", GUC_UNIT_S, 60 * 60},
  	{"min", GUC_UNIT_S, 60},
  	{"s", GUC_UNIT_S, 1},
  	{"ms", GUC_UNIT_S, 1.0 / 1000},
  	{"us", GUC_UNIT_S, 1.0 / (1000 * 1000)},
  
  	{"d", GUC_UNIT_MIN, 60 * 24},
  	{"h", GUC_UNIT_MIN, 60},
  	{"min", GUC_UNIT_MIN, 1},
  	{"s", GUC_UNIT_MIN, 1.0 / 60},
  	{"ms", GUC_UNIT_MIN, 1.0 / (1000 * 60)},
  	{"us", GUC_UNIT_MIN, 1.0 / (1000 * 1000 * 60)},
  
  	{""}						/* end of table marker */
  };
  
  /*
   * Contents of GUC tables
   *
   * See src/backend/utils/misc/README for design notes.
   *
   * TO ADD AN OPTION:
   *
   * 1. Declare a global variable of type bool, int, double, or char*
   *	  and make use of it.
   *
   * 2. Decide at what times it's safe to set the option. See guc.h for
   *	  details.
   *
   * 3. Decide on a name, a default value, upper and lower bounds (if
   *	  applicable), etc.
   *
   * 4. Add a record below.
   *
   * 5. Add it to src/backend/utils/misc/postgresql.conf.sample, if
   *	  appropriate.
   *
   * 6. Don't forget to document the option (at least in config.sgml).
   *
   * 7. If it's a new GUC_LIST_QUOTE option, you must add it to
   *	  variable_is_guc_list_quote() in src/bin/pg_dump/dumputils.c.
   */
  
  
  /******** option records follow ********/
  
  static struct config_bool ConfigureNamesBool[] =
  {
  	{
  		{"enable_seqscan", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of sequential-scan plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_seqscan,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_indexscan", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of index-scan plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_indexscan,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_indexonlyscan", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of index-only-scan plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_indexonlyscan,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_bitmapscan", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of bitmap-scan plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_bitmapscan,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_tidscan", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of TID scan plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_tidscan,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_sort", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of explicit sort steps."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_sort,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_incremental_sort", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of incremental sort steps."),
  			NULL
  		},
  		&enable_incremental_sort,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_hashagg", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of hashed aggregation plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_hashagg,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_material", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of materialization."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_material,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_memoize", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of memoization."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_memoize,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_nestloop", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of nested-loop join plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_nestloop,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_mergejoin", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of merge join plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_mergejoin,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_hashjoin", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of hash join plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_hashjoin,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_gathermerge", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of gather merge plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_gathermerge,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_partitionwise_join", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables partitionwise join."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_partitionwise_join,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_partitionwise_aggregate", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables partitionwise aggregation and grouping."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_partitionwise_aggregate,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_parallel_append", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of parallel append plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_parallel_append,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_parallel_hash", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of parallel hash plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_parallel_hash,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_partition_pruning", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables plan-time and execution-time partition pruning."),
  			gettext_noop("Allows the query planner and executor to compare partition "
  						 "bounds to conditions in the query to determine which "
  						 "partitions must be scanned."),
  			GUC_EXPLAIN
  		},
  		&enable_partition_pruning,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"enable_async_append", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enables the planner's use of async append plans."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&enable_async_append,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"geqo", PGC_USERSET, QUERY_TUNING_GEQO,
  			gettext_noop("Enables genetic query optimization."),
  			gettext_noop("This algorithm attempts to do planning without "
  						 "exhaustive searching."),
  			GUC_EXPLAIN
  		},
  		&enable_geqo,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		/* Not for general use --- used by SET SESSION AUTHORIZATION */
  		{"is_superuser", PGC_INTERNAL, UNGROUPED,
  			gettext_noop("Shows whether the current user is a superuser."),
  			NULL,
  			GUC_REPORT | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&session_auth_is_superuser,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"bonjour", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Enables advertising the server via Bonjour."),
  			NULL
  		},
  		&enable_bonjour,
  		false,
  		check_bonjour, NULL, NULL
  	},
  	{
  		{"track_commit_timestamp", PGC_POSTMASTER, REPLICATION_SENDING,
  			gettext_noop("Collects transaction commit time."),
  			NULL
  		},
  		&track_commit_timestamp,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"ssl", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Enables SSL connections."),
  			NULL
  		},
  		&EnableSSL,
  		false,
  		check_ssl, NULL, NULL
  	},
  	{
  		{"ssl_passphrase_command_supports_reload", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Also use ssl_passphrase_command during server reload."),
  			NULL
  		},
  		&ssl_passphrase_command_supports_reload,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"ssl_prefer_server_ciphers", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Give priority to server ciphersuite order."),
  			NULL
  		},
  		&SSLPreferServerCiphers,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"fsync", PGC_SIGHUP, WAL_SETTINGS,
  			gettext_noop("Forces synchronization of updates to disk."),
  			gettext_noop("The server will use the fsync() system call in several places to make "
  						 "sure that updates are physically written to disk. This insures "
  						 "that a database cluster will recover to a consistent state after "
  						 "an operating system or hardware crash.")
  		},
  		&enableFsync,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"ignore_checksum_failure", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Continues processing after a checksum failure."),
  			gettext_noop("Detection of a checksum failure normally causes PostgreSQL to "
  						 "report an error, aborting the current transaction. Setting "
  						 "ignore_checksum_failure to true causes the system to ignore the failure "
  						 "(but still report a warning), and continue processing. This "
  						 "behavior could cause crashes or other serious problems. Only "
  						 "has an effect if checksums are enabled."),
  			GUC_NOT_IN_SAMPLE
  		},
  		&ignore_checksum_failure,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"zero_damaged_pages", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Continues processing past damaged page headers."),
  			gettext_noop("Detection of a damaged page header normally causes PostgreSQL to "
  						 "report an error, aborting the current transaction. Setting "
  						 "zero_damaged_pages to true causes the system to instead report a "
  						 "warning, zero out the damaged page, and continue processing. This "
  						 "behavior will destroy data, namely all the rows on the damaged page."),
  			GUC_NOT_IN_SAMPLE
  		},
  		&zero_damaged_pages,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"ignore_invalid_pages", PGC_POSTMASTER, DEVELOPER_OPTIONS,
  			gettext_noop("Continues recovery after an invalid pages failure."),
  			gettext_noop("Detection of WAL records having references to "
  						 "invalid pages during recovery causes PostgreSQL to "
  						 "raise a PANIC-level error, aborting the recovery. "
  						 "Setting ignore_invalid_pages to true causes "
  						 "the system to ignore invalid page references "
  						 "in WAL records (but still report a warning), "
  						 "and continue recovery. This behavior may cause "
  						 "crashes, data loss, propagate or hide corruption, "
  						 "or other serious problems. Only has an effect "
  						 "during recovery or in standby mode."),
  			GUC_NOT_IN_SAMPLE
  		},
  		&ignore_invalid_pages,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"full_page_writes", PGC_SIGHUP, WAL_SETTINGS,
  			gettext_noop("Writes full pages to WAL when first modified after a checkpoint."),
  			gettext_noop("A page write in process during an operating system crash might be "
  						 "only partially written to disk.  During recovery, the row changes "
  						 "stored in WAL are not enough to recover.  This option writes "
  						 "pages when first modified after a checkpoint to WAL so full recovery "
  						 "is possible.")
  		},
  		&fullPageWrites,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_log_hints", PGC_POSTMASTER, WAL_SETTINGS,
  			gettext_noop("Writes full pages to WAL when first modified after a checkpoint, even for a non-critical modification."),
  			NULL
  		},
  		&wal_log_hints,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_compression", PGC_SUSET, WAL_SETTINGS,
  			gettext_noop("Compresses full-page writes written in WAL file."),
  			NULL
  		},
  		&wal_compression,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_init_zero", PGC_SUSET, WAL_SETTINGS,
  			gettext_noop("Writes zeroes to new WAL files before first use."),
  			NULL
  		},
  		&wal_init_zero,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_recycle", PGC_SUSET, WAL_SETTINGS,
  			gettext_noop("Recycles WAL files by renaming them."),
  			NULL
  		},
  		&wal_recycle,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_checkpoints", PGC_SIGHUP, LOGGING_WHAT,
  			gettext_noop("Logs each checkpoint."),
  			NULL
  		},
  		&log_checkpoints,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"log_connections", PGC_SU_BACKEND, LOGGING_WHAT,
  			gettext_noop("Logs each successful connection."),
  			NULL
  		},
  		&Log_connections,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"log_disconnections", PGC_SU_BACKEND, LOGGING_WHAT,
  			gettext_noop("Logs end of a session, including duration."),
  			NULL
  		},
  		&Log_disconnections,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"log_replication_commands", PGC_SUSET, LOGGING_WHAT,
  			gettext_noop("Logs each replication command."),
  			NULL
  		},
  		&log_replication_commands,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"debug_assertions", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows whether the running server has assertion checks enabled."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&assert_enabled,
  #ifdef USE_ASSERT_CHECKING
  		true,
  #else
  		false,
  #endif
  		NULL, NULL, NULL
  	},
  
  	{
  		{"exit_on_error", PGC_USERSET, ERROR_HANDLING_OPTIONS,
  			gettext_noop("Terminate session on any error."),
  			NULL
  		},
  		&ExitOnAnyError,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"restart_after_crash", PGC_SIGHUP, ERROR_HANDLING_OPTIONS,
  			gettext_noop("Reinitialize server after backend crash."),
  			NULL
  		},
  		&restart_after_crash,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"remove_temp_files_after_crash", PGC_SIGHUP, DEVELOPER_OPTIONS,
  			gettext_noop("Remove temporary files after backend crash."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&remove_temp_files_after_crash,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_duration", PGC_SUSET, LOGGING_WHAT,
  			gettext_noop("Logs the duration of each completed SQL statement."),
  			NULL
  		},
  		&log_duration,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"debug_print_parse", PGC_USERSET, LOGGING_WHAT,
  			gettext_noop("Logs each query's parse tree."),
  			NULL
  		},
  		&Debug_print_parse,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"debug_print_rewritten", PGC_USERSET, LOGGING_WHAT,
  			gettext_noop("Logs each query's rewritten parse tree."),
  			NULL
  		},
  		&Debug_print_rewritten,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"debug_print_plan", PGC_USERSET, LOGGING_WHAT,
  			gettext_noop("Logs each query's execution plan."),
  			NULL
  		},
  		&Debug_print_plan,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"debug_pretty_print", PGC_USERSET, LOGGING_WHAT,
  			gettext_noop("Indents parse and plan tree displays."),
  			NULL
  		},
  		&Debug_pretty_print,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"log_parser_stats", PGC_SUSET, STATS_MONITORING,
  			gettext_noop("Writes parser performance statistics to the server log."),
  			NULL
  		},
  		&log_parser_stats,
  		false,
  		check_stage_log_stats, NULL, NULL
  	},
  	{
  		{"log_planner_stats", PGC_SUSET, STATS_MONITORING,
  			gettext_noop("Writes planner performance statistics to the server log."),
  			NULL
  		},
  		&log_planner_stats,
  		false,
  		check_stage_log_stats, NULL, NULL
  	},
  	{
  		{"log_executor_stats", PGC_SUSET, STATS_MONITORING,
  			gettext_noop("Writes executor performance statistics to the server log."),
  			NULL
  		},
  		&log_executor_stats,
  		false,
  		check_stage_log_stats, NULL, NULL
  	},
  	{
  		{"log_statement_stats", PGC_SUSET, STATS_MONITORING,
  			gettext_noop("Writes cumulative performance statistics to the server log."),
  			NULL
  		},
  		&log_statement_stats,
  		false,
  		check_log_stats, NULL, NULL
  	},
  #ifdef BTREE_BUILD_STATS
  	{
  		{"log_btree_build_stats", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Logs system resource usage statistics (memory and CPU) on various B-tree operations."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&log_btree_build_stats,
  		false,
  		NULL, NULL, NULL
  	},
  #endif
  
  	{
  		{"track_activities", PGC_SUSET, STATS_COLLECTOR,
  			gettext_noop("Collects information about executing commands."),
  			gettext_noop("Enables the collection of information on the currently "
  						 "executing command of each session, along with "
  						 "the time at which that command began execution.")
  		},
  		&pgstat_track_activities,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"track_counts", PGC_SUSET, STATS_COLLECTOR,
  			gettext_noop("Collects statistics on database activity."),
  			NULL
  		},
  		&pgstat_track_counts,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"track_io_timing", PGC_SUSET, STATS_COLLECTOR,
  			gettext_noop("Collects timing statistics for database I/O activity."),
  			NULL
  		},
  		&track_io_timing,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"track_wal_io_timing", PGC_SUSET, STATS_COLLECTOR,
  			gettext_noop("Collects timing statistics for WAL I/O activity."),
  			NULL
  		},
  		&track_wal_io_timing,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"update_process_title", PGC_SUSET, PROCESS_TITLE,
  			gettext_noop("Updates the process title to show the active SQL command."),
  			gettext_noop("Enables updating of the process title every time a new SQL command is received by the server.")
  		},
  		&update_process_title,
  #ifdef WIN32
  		false,
  #else
  		true,
  #endif
  		NULL, NULL, NULL
  	},
  
  	{
  		{"autovacuum", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Starts the autovacuum subprocess."),
  			NULL
  		},
  		&autovacuum_start_daemon,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"trace_notify", PGC_USERSET, DEVELOPER_OPTIONS,
  			gettext_noop("Generates debugging output for LISTEN and NOTIFY."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&Trace_notify,
  		false,
  		NULL, NULL, NULL
  	},
  
  #ifdef LOCK_DEBUG
  	{
  		{"trace_locks", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Emits information about lock usage."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&Trace_locks,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"trace_userlocks", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Emits information about user lock usage."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&Trace_userlocks,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"trace_lwlocks", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Emits information about lightweight lock usage."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&Trace_lwlocks,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"debug_deadlocks", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Dumps information about all current locks when a deadlock timeout occurs."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&Debug_deadlocks,
  		false,
  		NULL, NULL, NULL
  	},
  #endif
  
  	{
  		{"log_lock_waits", PGC_SUSET, LOGGING_WHAT,
  			gettext_noop("Logs long lock waits."),
  			NULL
  		},
  		&log_lock_waits,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"log_recovery_conflict_waits", PGC_SIGHUP, LOGGING_WHAT,
  			gettext_noop("Logs standby recovery conflict waits."),
  			NULL
  		},
  		&log_recovery_conflict_waits,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"log_hostname", PGC_SIGHUP, LOGGING_WHAT,
  			gettext_noop("Logs the host name in the connection logs."),
  			gettext_noop("By default, connection logs only show the IP address "
  						 "of the connecting host. If you want them to show the host name you "
  						 "can turn this on, but depending on your host name resolution "
  						 "setup it might impose a non-negligible performance penalty.")
  		},
  		&log_hostname,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"transform_null_equals", PGC_USERSET, COMPAT_OPTIONS_CLIENT,
  			gettext_noop("Treats \"expr=NULL\" as \"expr IS NULL\"."),
  			gettext_noop("When turned on, expressions of the form expr = NULL "
  						 "(or NULL = expr) are treated as expr IS NULL, that is, they "
  						 "return true if expr evaluates to the null value, and false "
  						 "otherwise. The correct behavior of expr = NULL is to always "
  						 "return null (unknown).")
  		},
  		&Transform_null_equals,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"db_user_namespace", PGC_SIGHUP, CONN_AUTH_AUTH,
  			gettext_noop("Enables per-database user names."),
  			NULL
  		},
  		&Db_user_namespace,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"default_transaction_read_only", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the default read-only status of new transactions."),
  			NULL,
  			GUC_REPORT
  		},
  		&DefaultXactReadOnly,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"transaction_read_only", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the current transaction's read-only status."),
  			NULL,
  			GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&XactReadOnly,
  		false,
  		check_transaction_read_only, NULL, NULL
  	},
  	{
  		{"default_transaction_deferrable", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the default deferrable status of new transactions."),
  			NULL
  		},
  		&DefaultXactDeferrable,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"transaction_deferrable", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Whether to defer a read-only serializable transaction until it can be executed with no possible serialization failures."),
  			NULL,
  			GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&XactDeferrable,
  		false,
  		check_transaction_deferrable, NULL, NULL
  	},
  	{
  		{"row_security", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Enable row security."),
  			gettext_noop("When enabled, row security will be applied to all users.")
  		},
  		&row_security,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"check_function_bodies", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Check routine bodies during CREATE FUNCTION and CREATE PROCEDURE."),
  			NULL
  		},
  		&check_function_bodies,
  		true,
  		NULL, NULL, NULL
  	},
  	{
  		{"array_nulls", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("Enable input of NULL elements in arrays."),
  			gettext_noop("When turned on, unquoted NULL in an array input "
  						 "value means a null value; "
  						 "otherwise it is taken literally.")
  		},
  		&Array_nulls,
  		true,
  		NULL, NULL, NULL
  	},
  
  	/*
  	 * WITH OIDS support, and consequently default_with_oids, was removed in
  	 * PostgreSQL 12, but we tolerate the parameter being set to false to
  	 * avoid unnecessarily breaking older dump files.
  	 */
  	{
  		{"default_with_oids", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("WITH OIDS is no longer supported; this can only be false."),
  			NULL,
  			GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE
  		},
  		&default_with_oids,
  		false,
  		check_default_with_oids, NULL, NULL
  	},
  	{
  		{"logging_collector", PGC_POSTMASTER, LOGGING_WHERE,
  			gettext_noop("Start a subprocess to capture stderr output and/or csvlogs into log files."),
  			NULL
  		},
  		&Logging_collector,
  		false,
  		NULL, NULL, NULL
  	},
  	{
  		{"log_truncate_on_rotation", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Truncate existing log files of same name during log rotation."),
  			NULL
  		},
  		&Log_truncate_on_rotation,
  		false,
  		NULL, NULL, NULL
  	},
  
  #ifdef TRACE_SORT
  	{
  		{"trace_sort", PGC_USERSET, DEVELOPER_OPTIONS,
  			gettext_noop("Emit information about resource usage in sorting."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&trace_sort,
  		false,
  		NULL, NULL, NULL
  	},
  #endif
  
  #ifdef TRACE_SYNCSCAN
  	/* this is undocumented because not exposed in a standard build */
  	{
  		{"trace_syncscan", PGC_USERSET, DEVELOPER_OPTIONS,
  			gettext_noop("Generate debugging output for synchronized scanning."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&trace_syncscan,
  		false,
  		NULL, NULL, NULL
  	},
  #endif
  
  #ifdef DEBUG_BOUNDED_SORT
  	/* this is undocumented because not exposed in a standard build */
  	{
  		{
  			"optimize_bounded_sort", PGC_USERSET, QUERY_TUNING_METHOD,
  			gettext_noop("Enable bounded sorting using heap sort."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_EXPLAIN
  		},
  		&optimize_bounded_sort,
  		true,
  		NULL, NULL, NULL
  	},
  #endif
  
  #ifdef WAL_DEBUG
  	{
  		{"wal_debug", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Emit WAL-related debugging output."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&XLOG_DEBUG,
  		false,
  		NULL, NULL, NULL
  	},
  #endif
  
  	{
  		{"integer_datetimes", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows whether datetimes are integer based."),
  			NULL,
  			GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&integer_datetimes,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"krb_caseins_users", PGC_SIGHUP, CONN_AUTH_AUTH,
  			gettext_noop("Sets whether Kerberos and GSSAPI user names should be treated as case-insensitive."),
  			NULL
  		},
  		&pg_krb_caseins_users,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"escape_string_warning", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("Warn about backslash escapes in ordinary string literals."),
  			NULL
  		},
  		&escape_string_warning,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"standard_conforming_strings", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("Causes '...' strings to treat backslashes literally."),
  			NULL,
  			GUC_REPORT
  		},
  		&standard_conforming_strings,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"synchronize_seqscans", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("Enable synchronized sequential scans."),
  			NULL
  		},
  		&synchronize_seqscans,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"recovery_target_inclusive", PGC_POSTMASTER, WAL_RECOVERY_TARGET,
  			gettext_noop("Sets whether to include or exclude transaction with recovery target."),
  			NULL
  		},
  		&recoveryTargetInclusive,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"hot_standby", PGC_POSTMASTER, REPLICATION_STANDBY,
  			gettext_noop("Allows connections and queries during recovery."),
  			NULL
  		},
  		&EnableHotStandby,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"hot_standby_feedback", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Allows feedback from a hot standby to the primary that will avoid query conflicts."),
  			NULL
  		},
  		&hot_standby_feedback,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"in_hot_standby", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows whether hot standby is currently active."),
  			NULL,
  			GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&in_hot_standby,
  		false,
  		NULL, NULL, show_in_hot_standby
  	},
  
  	{
  		{"allow_system_table_mods", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Allows modifications of the structure of system tables."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&allowSystemTableMods,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ignore_system_indexes", PGC_BACKEND, DEVELOPER_OPTIONS,
  			gettext_noop("Disables reading from system indexes."),
  			gettext_noop("It does not prevent updating the indexes, so it is safe "
  						 "to use.  The worst consequence is slowness."),
  			GUC_NOT_IN_SAMPLE
  		},
  		&IgnoreSystemIndexes,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"lo_compat_privileges", PGC_SUSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("Enables backward compatibility mode for privilege checks on large objects."),
  			gettext_noop("Skips privilege checks when reading or modifying large objects, "
  						 "for compatibility with PostgreSQL releases prior to 9.0.")
  		},
  		&lo_compat_privileges,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"quote_all_identifiers", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("When generating SQL fragments, quote all identifiers."),
  			NULL,
  		},
  		&quote_all_identifiers,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"data_checksums", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows whether data checksums are turned on for this cluster."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&data_checksums,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"syslog_sequence_numbers", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Add sequence number to syslog messages to avoid duplicate suppression."),
  			NULL
  		},
  		&syslog_sequence_numbers,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"syslog_split_messages", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Split messages sent to syslog by lines and to fit into 1024 bytes."),
  			NULL
  		},
  		&syslog_split_messages,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"parallel_leader_participation", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
  			gettext_noop("Controls whether Gather and Gather Merge also run subplans."),
  			gettext_noop("Should gather nodes also run subplans or just gather tuples?"),
  			GUC_EXPLAIN
  		},
  		&parallel_leader_participation,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit", PGC_USERSET, QUERY_TUNING_OTHER,
  			gettext_noop("Allow JIT compilation."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&jit_enabled,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit_debugging_support", PGC_SU_BACKEND, DEVELOPER_OPTIONS,
  			gettext_noop("Register JIT-compiled functions with debugger."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&jit_debugging_support,
  		false,
  
  		/*
  		 * This is not guaranteed to be available, but given it's a developer
  		 * oriented option, it doesn't seem worth adding code checking
  		 * availability.
  		 */
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit_dump_bitcode", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Write out LLVM bitcode to facilitate JIT debugging."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&jit_dump_bitcode,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit_expressions", PGC_USERSET, DEVELOPER_OPTIONS,
  			gettext_noop("Allow JIT compilation of expressions."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&jit_expressions,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit_profiling_support", PGC_SU_BACKEND, DEVELOPER_OPTIONS,
  			gettext_noop("Register JIT-compiled functions with perf profiler."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&jit_profiling_support,
  		false,
  
  		/*
  		 * This is not guaranteed to be available, but given it's a developer
  		 * oriented option, it doesn't seem worth adding code checking
  		 * availability.
  		 */
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit_tuple_deforming", PGC_USERSET, DEVELOPER_OPTIONS,
  			gettext_noop("Allow JIT compilation of tuple deforming."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&jit_tuple_deforming,
  		true,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"data_sync_retry", PGC_POSTMASTER, ERROR_HANDLING_OPTIONS,
  			gettext_noop("Whether to continue running after a failure to sync data files."),
  		},
  		&data_sync_retry,
  		false,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_receiver_create_temp_slot", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets whether a WAL receiver should create a temporary replication slot if no permanent slot is configured."),
  		},
  		&wal_receiver_create_temp_slot,
  		false,
  		NULL, NULL, NULL
  	},
  
  	/* End-of-list marker */
  	{
  		{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL
  	}
  };
  
  
  static struct config_int ConfigureNamesInt[] =
  {
  	{
  		{"archive_timeout", PGC_SIGHUP, WAL_ARCHIVING,
  			gettext_noop("Forces a switch to the next WAL file if a "
  						 "new file has not been started within N seconds."),
  			NULL,
  			GUC_UNIT_S
  		},
  		&XLogArchiveTimeout,
  		0, 0, INT_MAX / 2,
  		NULL, NULL, NULL
  	},
  	{
  		{"post_auth_delay", PGC_BACKEND, DEVELOPER_OPTIONS,
  			gettext_noop("Waits N seconds on connection startup after authentication."),
  			gettext_noop("This allows attaching a debugger to the process."),
  			GUC_NOT_IN_SAMPLE | GUC_UNIT_S
  		},
  		&PostAuthDelay,
  		0, 0, INT_MAX / 1000000,
  		NULL, NULL, NULL
  	},
  	{
  		{"default_statistics_target", PGC_USERSET, QUERY_TUNING_OTHER,
  			gettext_noop("Sets the default statistics target."),
  			gettext_noop("This applies to table columns that have not had a "
  						 "column-specific target set via ALTER TABLE SET STATISTICS.")
  		},
  		&default_statistics_target,
  		100, 1, 10000,
  		NULL, NULL, NULL
  	},
  	{
  		{"from_collapse_limit", PGC_USERSET, QUERY_TUNING_OTHER,
  			gettext_noop("Sets the FROM-list size beyond which subqueries "
  						 "are not collapsed."),
  			gettext_noop("The planner will merge subqueries into upper "
  						 "queries if the resulting FROM list would have no more than "
  						 "this many items."),
  			GUC_EXPLAIN
  		},
  		&from_collapse_limit,
  		8, 1, INT_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"join_collapse_limit", PGC_USERSET, QUERY_TUNING_OTHER,
  			gettext_noop("Sets the FROM-list size beyond which JOIN "
  						 "constructs are not flattened."),
  			gettext_noop("The planner will flatten explicit JOIN "
  						 "constructs into lists of FROM items whenever a "
  						 "list of no more than this many items would result."),
  			GUC_EXPLAIN
  		},
  		&join_collapse_limit,
  		8, 1, INT_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"geqo_threshold", PGC_USERSET, QUERY_TUNING_GEQO,
  			gettext_noop("Sets the threshold of FROM items beyond which GEQO is used."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&geqo_threshold,
  		12, 2, INT_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"geqo_effort", PGC_USERSET, QUERY_TUNING_GEQO,
  			gettext_noop("GEQO: effort is used to set the default for other GEQO parameters."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&Geqo_effort,
  		DEFAULT_GEQO_EFFORT, MIN_GEQO_EFFORT, MAX_GEQO_EFFORT,
  		NULL, NULL, NULL
  	},
  	{
  		{"geqo_pool_size", PGC_USERSET, QUERY_TUNING_GEQO,
  			gettext_noop("GEQO: number of individuals in the population."),
  			gettext_noop("Zero selects a suitable default value."),
  			GUC_EXPLAIN
  		},
  		&Geqo_pool_size,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"geqo_generations", PGC_USERSET, QUERY_TUNING_GEQO,
  			gettext_noop("GEQO: number of iterations of the algorithm."),
  			gettext_noop("Zero selects a suitable default value."),
  			GUC_EXPLAIN
  		},
  		&Geqo_generations,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		/* This is PGC_SUSET to prevent hiding from log_lock_waits. */
  		{"deadlock_timeout", PGC_SUSET, LOCK_MANAGEMENT,
  			gettext_noop("Sets the time to wait on a lock before checking for deadlock."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&DeadlockTimeout,
  		1000, 1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_standby_archive_delay", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets the maximum delay before canceling queries when a hot standby server is processing archived WAL data."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&max_standby_archive_delay,
  		30 * 1000, -1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_standby_streaming_delay", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets the maximum delay before canceling queries when a hot standby server is processing streamed WAL data."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&max_standby_streaming_delay,
  		30 * 1000, -1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"recovery_min_apply_delay", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets the minimum delay for applying changes during recovery."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&recovery_min_apply_delay,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_receiver_status_interval", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets the maximum interval between WAL receiver status reports to the sending server."),
  			NULL,
  			GUC_UNIT_S
  		},
  		&wal_receiver_status_interval,
  		10, 0, INT_MAX / 1000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_receiver_timeout", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets the maximum wait time to receive data from the sending server."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&wal_receiver_timeout,
  		60 * 1000, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the maximum number of concurrent connections."),
  			NULL
  		},
  		&MaxConnections,
  		100, 1, MAX_BACKENDS,
  		check_maxconnections, NULL, NULL
  	},
  
  	{
  		/* see max_connections */
  		{"superuser_reserved_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the number of connection slots reserved for superusers."),
  			NULL
  		},
  		&ReservedBackends,
  		3, 0, MAX_BACKENDS,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"min_dynamic_shared_memory", PGC_POSTMASTER, RESOURCES_MEM,
  			gettext_noop("Amount of dynamic shared memory reserved at startup."),
  			NULL,
  			GUC_UNIT_MB
  		},
  		&min_dynamic_shared_memory,
  		0, 0, (int) Min((size_t) INT_MAX, SIZE_MAX / (1024 * 1024)),
  		NULL, NULL, NULL
  	},
  
  	/*
  	 * We sometimes multiply the number of shared buffers by two without
  	 * checking for overflow, so we mustn't allow more than INT_MAX / 2.
  	 */
  	{
  		{"shared_buffers", PGC_POSTMASTER, RESOURCES_MEM,
  			gettext_noop("Sets the number of shared memory buffers used by the server."),
  			NULL,
  			GUC_UNIT_BLOCKS
  		},
  		&NBuffers,
  		1024, 16, INT_MAX / 2,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"temp_buffers", PGC_USERSET, RESOURCES_MEM,
  			gettext_noop("Sets the maximum number of temporary buffers used by each session."),
  			NULL,
  			GUC_UNIT_BLOCKS | GUC_EXPLAIN
  		},
  		&num_temp_buffers,
  		1024, 100, INT_MAX / 2,
  		check_temp_buffers, NULL, NULL
  	},
  
  	{
  		{"port", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the TCP port the server listens on."),
  			NULL
  		},
  		&PostPortNumber,
  		DEF_PGPORT, 1, 65535,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"unix_socket_permissions", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the access permissions of the Unix-domain socket."),
  			gettext_noop("Unix-domain sockets use the usual Unix file system "
  						 "permission set. The parameter value is expected "
  						 "to be a numeric mode specification in the form "
  						 "accepted by the chmod and umask system calls. "
  						 "(To use the customary octal format the number must "
  						 "start with a 0 (zero).)")
  		},
  		&Unix_socket_permissions,
  		0777, 0000, 0777,
  		NULL, NULL, show_unix_socket_permissions
  	},
  
  	{
  		{"log_file_mode", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Sets the file permissions for log files."),
  			gettext_noop("The parameter value is expected "
  						 "to be a numeric mode specification in the form "
  						 "accepted by the chmod and umask system calls. "
  						 "(To use the customary octal format the number must "
  						 "start with a 0 (zero).)")
  		},
  		&Log_file_mode,
  		0600, 0000, 0777,
  		NULL, NULL, show_log_file_mode
  	},
  
  
  	{
  		{"data_directory_mode", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the mode of the data directory."),
  			gettext_noop("The parameter value is a numeric mode specification "
  						 "in the form accepted by the chmod and umask system "
  						 "calls. (To use the customary octal format the number "
  						 "must start with a 0 (zero).)"),
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&data_directory_mode,
  		0700, 0000, 0777,
  		NULL, NULL, show_data_directory_mode
  	},
  
  	{
  		{"work_mem", PGC_USERSET, RESOURCES_MEM,
  			gettext_noop("Sets the maximum memory to be used for query workspaces."),
  			gettext_noop("This much memory can be used by each internal "
  						 "sort operation and hash table before switching to "
  						 "temporary disk files."),
  			GUC_UNIT_KB | GUC_EXPLAIN
  		},
  		&work_mem,
  		4096, 64, MAX_KILOBYTES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"maintenance_work_mem", PGC_USERSET, RESOURCES_MEM,
  			gettext_noop("Sets the maximum memory to be used for maintenance operations."),
  			gettext_noop("This includes operations such as VACUUM and CREATE INDEX."),
  			GUC_UNIT_KB
  		},
  		&maintenance_work_mem,
  		65536, 1024, MAX_KILOBYTES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"logical_decoding_work_mem", PGC_USERSET, RESOURCES_MEM,
  			gettext_noop("Sets the maximum memory to be used for logical decoding."),
  			gettext_noop("This much memory can be used by each internal "
  						 "reorder buffer before spilling to disk."),
  			GUC_UNIT_KB
  		},
  		&logical_decoding_work_mem,
  		65536, 64, MAX_KILOBYTES,
  		NULL, NULL, NULL
  	},
  
  	/*
  	 * We use the hopefully-safely-small value of 100kB as the compiled-in
  	 * default for max_stack_depth.  InitializeGUCOptions will increase it if
  	 * possible, depending on the actual platform-specific stack limit.
  	 */
  	{
  		{"max_stack_depth", PGC_SUSET, RESOURCES_MEM,
  			gettext_noop("Sets the maximum stack depth, in kilobytes."),
  			NULL,
  			GUC_UNIT_KB
  		},
  		&max_stack_depth,
  		100, 100, MAX_KILOBYTES,
  		check_max_stack_depth, assign_max_stack_depth, NULL
  	},
  
  	{
  		{"temp_file_limit", PGC_SUSET, RESOURCES_DISK,
  			gettext_noop("Limits the total size of all temporary files used by each process."),
  			gettext_noop("-1 means no limit."),
  			GUC_UNIT_KB
  		},
  		&temp_file_limit,
  		-1, -1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_cost_page_hit", PGC_USERSET, RESOURCES_VACUUM_DELAY,
  			gettext_noop("Vacuum cost for a page found in the buffer cache."),
  			NULL
  		},
  		&VacuumCostPageHit,
  		1, 0, 10000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_cost_page_miss", PGC_USERSET, RESOURCES_VACUUM_DELAY,
  			gettext_noop("Vacuum cost for a page not found in the buffer cache."),
  			NULL
  		},
  		&VacuumCostPageMiss,
  		2, 0, 10000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_cost_page_dirty", PGC_USERSET, RESOURCES_VACUUM_DELAY,
  			gettext_noop("Vacuum cost for a page dirtied by vacuum."),
  			NULL
  		},
  		&VacuumCostPageDirty,
  		20, 0, 10000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_cost_limit", PGC_USERSET, RESOURCES_VACUUM_DELAY,
  			gettext_noop("Vacuum cost amount available before napping."),
  			NULL
  		},
  		&VacuumCostLimit,
  		200, 1, 10000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"autovacuum_vacuum_cost_limit", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Vacuum cost amount available before napping, for autovacuum."),
  			NULL
  		},
  		&autovacuum_vac_cost_limit,
  		-1, -1, 10000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_files_per_process", PGC_POSTMASTER, RESOURCES_KERNEL,
  			gettext_noop("Sets the maximum number of simultaneously open files for each server process."),
  			NULL
  		},
  		&max_files_per_process,
  		1000, 64, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	/*
  	 * See also CheckRequiredParameterValues() if this parameter changes
  	 */
  	{
  		{"max_prepared_transactions", PGC_POSTMASTER, RESOURCES_MEM,
  			gettext_noop("Sets the maximum number of simultaneously prepared transactions."),
  			NULL
  		},
  		&max_prepared_xacts,
  		0, 0, MAX_BACKENDS,
  		NULL, NULL, NULL
  	},
  
  #ifdef LOCK_DEBUG
  	{
  		{"trace_lock_oidmin", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Sets the minimum OID of tables for tracking locks."),
  			gettext_noop("Is used to avoid output on system tables."),
  			GUC_NOT_IN_SAMPLE
  		},
  		&Trace_lock_oidmin,
  		FirstNormalObjectId, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"trace_lock_table", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Sets the OID of the table with unconditionally lock tracing."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&Trace_lock_table,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  #endif
  
  	{
  		{"statement_timeout", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the maximum allowed duration of any statement."),
  			gettext_noop("A value of 0 turns off the timeout."),
  			GUC_UNIT_MS
  		},
  		&StatementTimeout,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"lock_timeout", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the maximum allowed duration of any wait for a lock."),
  			gettext_noop("A value of 0 turns off the timeout."),
  			GUC_UNIT_MS
  		},
  		&LockTimeout,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"idle_in_transaction_session_timeout", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the maximum allowed idle time between queries, when in a transaction."),
  			gettext_noop("A value of 0 turns off the timeout."),
  			GUC_UNIT_MS
  		},
  		&IdleInTransactionSessionTimeout,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"idle_session_timeout", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the maximum allowed idle time between queries, when not in a transaction."),
  			gettext_noop("A value of 0 turns off the timeout."),
  			GUC_UNIT_MS
  		},
  		&IdleSessionTimeout,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_freeze_min_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Minimum age at which VACUUM should freeze a table row."),
  			NULL
  		},
  		&vacuum_freeze_min_age,
  		50000000, 0, 1000000000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_freeze_table_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Age at which VACUUM should scan whole table to freeze tuples."),
  			NULL
  		},
  		&vacuum_freeze_table_age,
  		150000000, 0, 2000000000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_multixact_freeze_min_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Minimum age at which VACUUM should freeze a MultiXactId in a table row."),
  			NULL
  		},
  		&vacuum_multixact_freeze_min_age,
  		5000000, 0, 1000000000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_multixact_freeze_table_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Multixact age at which VACUUM should scan whole table to freeze tuples."),
  			NULL
  		},
  		&vacuum_multixact_freeze_table_age,
  		150000000, 0, 2000000000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"vacuum_defer_cleanup_age", PGC_SIGHUP, REPLICATION_PRIMARY,
  			gettext_noop("Number of transactions by which VACUUM and HOT cleanup should be deferred, if any."),
  			NULL
  		},
  		&vacuum_defer_cleanup_age,
  		0, 0, 1000000,			/* see ComputeXidHorizons */
  		NULL, NULL, NULL
  	},
  	{
  		{"vacuum_failsafe_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Age at which VACUUM should trigger failsafe to avoid a wraparound outage."),
  			NULL
  		},
  		&vacuum_failsafe_age,
  		1600000000, 0, 2100000000,
  		NULL, NULL, NULL
  	},
  	{
  		{"vacuum_multixact_failsafe_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Multixact age at which VACUUM should trigger failsafe to avoid a wraparound outage."),
  			NULL
  		},
  		&vacuum_multixact_failsafe_age,
  		1600000000, 0, 2100000000,
  		NULL, NULL, NULL
  	},
  
  	/*
  	 * See also CheckRequiredParameterValues() if this parameter changes
  	 */
  	{
  		{"max_locks_per_transaction", PGC_POSTMASTER, LOCK_MANAGEMENT,
  			gettext_noop("Sets the maximum number of locks per transaction."),
  			gettext_noop("The shared lock table is sized on the assumption that "
  						 "at most max_locks_per_transaction * max_connections distinct "
  						 "objects will need to be locked at any one time.")
  		},
  		&max_locks_per_xact,
  		64, 10, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_pred_locks_per_transaction", PGC_POSTMASTER, LOCK_MANAGEMENT,
  			gettext_noop("Sets the maximum number of predicate locks per transaction."),
  			gettext_noop("The shared predicate lock table is sized on the assumption that "
  						 "at most max_pred_locks_per_transaction * max_connections distinct "
  						 "objects will need to be locked at any one time.")
  		},
  		&max_predicate_locks_per_xact,
  		64, 10, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_pred_locks_per_relation", PGC_SIGHUP, LOCK_MANAGEMENT,
  			gettext_noop("Sets the maximum number of predicate-locked pages and tuples per relation."),
  			gettext_noop("If more than this total of pages and tuples in the same relation are locked "
  						 "by a connection, those locks are replaced by a relation-level lock.")
  		},
  		&max_predicate_locks_per_relation,
  		-2, INT_MIN, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_pred_locks_per_page", PGC_SIGHUP, LOCK_MANAGEMENT,
  			gettext_noop("Sets the maximum number of predicate-locked tuples per page."),
  			gettext_noop("If more than this number of tuples on the same page are locked "
  						 "by a connection, those locks are replaced by a page-level lock.")
  		},
  		&max_predicate_locks_per_page,
  		2, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"authentication_timeout", PGC_SIGHUP, CONN_AUTH_AUTH,
  			gettext_noop("Sets the maximum allowed time to complete client authentication."),
  			NULL,
  			GUC_UNIT_S
  		},
  		&AuthenticationTimeout,
  		60, 1, 600,
  		NULL, NULL, NULL
  	},
  
  	{
  		/* Not for general use */
  		{"pre_auth_delay", PGC_SIGHUP, DEVELOPER_OPTIONS,
  			gettext_noop("Waits N seconds on connection startup before authentication."),
  			gettext_noop("This allows attaching a debugger to the process."),
  			GUC_NOT_IN_SAMPLE | GUC_UNIT_S
  		},
  		&PreAuthDelay,
  		0, 0, 60,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_keep_size", PGC_SIGHUP, REPLICATION_SENDING,
  			gettext_noop("Sets the size of WAL files held for standby servers."),
  			NULL,
  			GUC_UNIT_MB
  		},
  		&wal_keep_size_mb,
  		0, 0, MAX_KILOBYTES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"min_wal_size", PGC_SIGHUP, WAL_CHECKPOINTS,
  			gettext_noop("Sets the minimum size to shrink the WAL to."),
  			NULL,
  			GUC_UNIT_MB
  		},
  		&min_wal_size_mb,
  		DEFAULT_MIN_WAL_SEGS * (DEFAULT_XLOG_SEG_SIZE / (1024 * 1024)),
  		2, MAX_KILOBYTES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_wal_size", PGC_SIGHUP, WAL_CHECKPOINTS,
  			gettext_noop("Sets the WAL size that triggers a checkpoint."),
  			NULL,
  			GUC_UNIT_MB
  		},
  		&max_wal_size_mb,
  		DEFAULT_MAX_WAL_SEGS * (DEFAULT_XLOG_SEG_SIZE / (1024 * 1024)),
  		2, MAX_KILOBYTES,
  		NULL, assign_max_wal_size, NULL
  	},
  
  	{
  		{"checkpoint_timeout", PGC_SIGHUP, WAL_CHECKPOINTS,
  			gettext_noop("Sets the maximum time between automatic WAL checkpoints."),
  			NULL,
  			GUC_UNIT_S
  		},
  		&CheckPointTimeout,
  		300, 30, 86400,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"checkpoint_warning", PGC_SIGHUP, WAL_CHECKPOINTS,
  			gettext_noop("Enables warnings if checkpoint segments are filled more "
  						 "frequently than this."),
  			gettext_noop("Write a message to the server log if checkpoints "
  						 "caused by the filling of checkpoint segment files happens more "
  						 "frequently than this number of seconds. Zero turns off the warning."),
  			GUC_UNIT_S
  		},
  		&CheckPointWarning,
  		30, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"checkpoint_flush_after", PGC_SIGHUP, WAL_CHECKPOINTS,
  			gettext_noop("Number of pages after which previously performed writes are flushed to disk."),
  			NULL,
  			GUC_UNIT_BLOCKS
  		},
  		&checkpoint_flush_after,
  		DEFAULT_CHECKPOINT_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_buffers", PGC_POSTMASTER, WAL_SETTINGS,
  			gettext_noop("Sets the number of disk-page buffers in shared memory for WAL."),
  			NULL,
  			GUC_UNIT_XBLOCKS
  		},
  		&XLOGbuffers,
  		-1, -1, (INT_MAX / XLOG_BLCKSZ),
  		check_wal_buffers, NULL, NULL
  	},
  
  	{
  		{"wal_writer_delay", PGC_SIGHUP, WAL_SETTINGS,
  			gettext_noop("Time between WAL flushes performed in the WAL writer."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&WalWriterDelay,
  		200, 1, 10000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_writer_flush_after", PGC_SIGHUP, WAL_SETTINGS,
  			gettext_noop("Amount of WAL written out by WAL writer that triggers a flush."),
  			NULL,
  			GUC_UNIT_XBLOCKS
  		},
  		&WalWriterFlushAfter,
  		(1024 * 1024) / XLOG_BLCKSZ, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_skip_threshold", PGC_USERSET, WAL_SETTINGS,
  			gettext_noop("Minimum size of new file to fsync instead of writing WAL."),
  			NULL,
  			GUC_UNIT_KB
  		},
  		&wal_skip_threshold,
  		2048, 0, MAX_KILOBYTES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_wal_senders", PGC_POSTMASTER, REPLICATION_SENDING,
  			gettext_noop("Sets the maximum number of simultaneously running WAL sender processes."),
  			NULL
  		},
  		&max_wal_senders,
  		10, 0, MAX_BACKENDS,
  		check_max_wal_senders, NULL, NULL
  	},
  
  	{
  		/* see max_wal_senders */
  		{"max_replication_slots", PGC_POSTMASTER, REPLICATION_SENDING,
  			gettext_noop("Sets the maximum number of simultaneously defined replication slots."),
  			NULL
  		},
  		&max_replication_slots,
  		10, 0, MAX_BACKENDS /* XXX? */ ,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_slot_wal_keep_size", PGC_SIGHUP, REPLICATION_SENDING,
  			gettext_noop("Sets the maximum WAL size that can be reserved by replication slots."),
  			gettext_noop("Replication slots will be marked as failed, and segments released "
  						 "for deletion or recycling, if this much space is occupied by WAL "
  						 "on disk."),
  			GUC_UNIT_MB
  		},
  		&max_slot_wal_keep_size_mb,
  		-1, -1, MAX_KILOBYTES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_sender_timeout", PGC_USERSET, REPLICATION_SENDING,
  			gettext_noop("Sets the maximum time to wait for WAL replication."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&wal_sender_timeout,
  		60 * 1000, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"commit_delay", PGC_SUSET, WAL_SETTINGS,
  			gettext_noop("Sets the delay in microseconds between transaction commit and "
  						 "flushing WAL to disk."),
  			NULL
  			/* we have no microseconds designation, so can't supply units here */
  		},
  		&CommitDelay,
  		0, 0, 100000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"commit_siblings", PGC_USERSET, WAL_SETTINGS,
  			gettext_noop("Sets the minimum concurrent open transactions before performing "
  						 "commit_delay."),
  			NULL
  		},
  		&CommitSiblings,
  		5, 0, 1000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"extra_float_digits", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the number of digits displayed for floating-point values."),
  			gettext_noop("This affects real, double precision, and geometric data types. "
  						 "A zero or negative parameter value is added to the standard "
  						 "number of digits (FLT_DIG or DBL_DIG as appropriate). "
  						 "Any value greater than zero selects precise output mode.")
  		},
  		&extra_float_digits,
  		1, -15, 3,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_min_duration_sample", PGC_SUSET, LOGGING_WHEN,
  			gettext_noop("Sets the minimum execution time above which "
  						 "a sample of statements will be logged."
  						 " Sampling is determined by log_statement_sample_rate."),
  			gettext_noop("Zero logs a sample of all queries. -1 turns this feature off."),
  			GUC_UNIT_MS
  		},
  		&log_min_duration_sample,
  		-1, -1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_min_duration_statement", PGC_SUSET, LOGGING_WHEN,
  			gettext_noop("Sets the minimum execution time above which "
  						 "all statements will be logged."),
  			gettext_noop("Zero prints all queries. -1 turns this feature off."),
  			GUC_UNIT_MS
  		},
  		&log_min_duration_statement,
  		-1, -1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_autovacuum_min_duration", PGC_SIGHUP, LOGGING_WHAT,
  			gettext_noop("Sets the minimum execution time above which "
  						 "autovacuum actions will be logged."),
  			gettext_noop("Zero prints all actions. -1 turns autovacuum logging off."),
  			GUC_UNIT_MS
  		},
  		&Log_autovacuum_min_duration,
  		-1, -1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_parameter_max_length", PGC_SUSET, LOGGING_WHAT,
  			gettext_noop("When logging statements, limit logged parameter values to first N bytes."),
  			gettext_noop("-1 to print values in full."),
  			GUC_UNIT_BYTE
  		},
  		&log_parameter_max_length,
  		-1, -1, INT_MAX / 2,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_parameter_max_length_on_error", PGC_USERSET, LOGGING_WHAT,
  			gettext_noop("When reporting an error, limit logged parameter values to first N bytes."),
  			gettext_noop("-1 to print values in full."),
  			GUC_UNIT_BYTE
  		},
  		&log_parameter_max_length_on_error,
  		0, -1, INT_MAX / 2,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"bgwriter_delay", PGC_SIGHUP, RESOURCES_BGWRITER,
  			gettext_noop("Background writer sleep time between rounds."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&BgWriterDelay,
  		200, 10, 10000,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"bgwriter_lru_maxpages", PGC_SIGHUP, RESOURCES_BGWRITER,
  			gettext_noop("Background writer maximum number of LRU pages to flush per round."),
  			NULL
  		},
  		&bgwriter_lru_maxpages,
  		100, 0, INT_MAX / 2,	/* Same upper limit as shared_buffers */
  		NULL, NULL, NULL
  	},
  
  	{
  		{"bgwriter_flush_after", PGC_SIGHUP, RESOURCES_BGWRITER,
  			gettext_noop("Number of pages after which previously performed writes are flushed to disk."),
  			NULL,
  			GUC_UNIT_BLOCKS
  		},
  		&bgwriter_flush_after,
  		DEFAULT_BGWRITER_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"effective_io_concurrency",
  			PGC_USERSET,
  			RESOURCES_ASYNCHRONOUS,
  			gettext_noop("Number of simultaneous requests that can be handled efficiently by the disk subsystem."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&effective_io_concurrency,
  #ifdef USE_PREFETCH
  		1,
  #else
  		0,
  #endif
  		0, MAX_IO_CONCURRENCY,
  		check_effective_io_concurrency, NULL, NULL
  	},
  
  	{
  		{"maintenance_io_concurrency",
  			PGC_USERSET,
  			RESOURCES_ASYNCHRONOUS,
  			gettext_noop("A variant of effective_io_concurrency that is used for maintenance work."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&maintenance_io_concurrency,
  #ifdef USE_PREFETCH
  		10,
  #else
  		0,
  #endif
  		0, MAX_IO_CONCURRENCY,
  		check_maintenance_io_concurrency, NULL, NULL
  	},
  
  	{
  		{"backend_flush_after", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
  			gettext_noop("Number of pages after which previously performed writes are flushed to disk."),
  			NULL,
  			GUC_UNIT_BLOCKS
  		},
  		&backend_flush_after,
  		DEFAULT_BACKEND_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_worker_processes",
  			PGC_POSTMASTER,
  			RESOURCES_ASYNCHRONOUS,
  			gettext_noop("Maximum number of concurrent worker processes."),
  			NULL,
  		},
  		&max_worker_processes,
  		8, 0, MAX_BACKENDS,
  		check_max_worker_processes, NULL, NULL
  	},
  
  	{
  		{"max_logical_replication_workers",
  			PGC_POSTMASTER,
  			REPLICATION_SUBSCRIBERS,
  			gettext_noop("Maximum number of logical replication worker processes."),
  			NULL,
  		},
  		&max_logical_replication_workers,
  		4, 0, MAX_BACKENDS,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_sync_workers_per_subscription",
  			PGC_SIGHUP,
  			REPLICATION_SUBSCRIBERS,
  			gettext_noop("Maximum number of table synchronization workers per subscription."),
  			NULL,
  		},
  		&max_sync_workers_per_subscription,
  		2, 0, MAX_BACKENDS,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Automatic log file rotation will occur after N minutes."),
  			NULL,
  			GUC_UNIT_MIN
  		},
  		&Log_RotationAge,
  		HOURS_PER_DAY * MINS_PER_HOUR, 0, INT_MAX / SECS_PER_MINUTE,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_rotation_size", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Automatic log file rotation will occur after N kilobytes."),
  			NULL,
  			GUC_UNIT_KB
  		},
  		&Log_RotationSize,
  		10 * 1024, 0, INT_MAX / 1024,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_function_args", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the maximum number of function arguments."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&max_function_args,
  		FUNC_MAX_ARGS, FUNC_MAX_ARGS, FUNC_MAX_ARGS,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_index_keys", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the maximum number of index keys."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&max_index_keys,
  		INDEX_MAX_KEYS, INDEX_MAX_KEYS, INDEX_MAX_KEYS,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_identifier_length", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the maximum identifier length."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&max_identifier_length,
  		NAMEDATALEN - 1, NAMEDATALEN - 1, NAMEDATALEN - 1,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"block_size", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the size of a disk block."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&block_size,
  		BLCKSZ, BLCKSZ, BLCKSZ,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"segment_size", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the number of pages per disk file."),
  			NULL,
  			GUC_UNIT_BLOCKS | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&segment_size,
  		RELSEG_SIZE, RELSEG_SIZE, RELSEG_SIZE,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_block_size", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the block size in the write ahead log."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&wal_block_size,
  		XLOG_BLCKSZ, XLOG_BLCKSZ, XLOG_BLCKSZ,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_retrieve_retry_interval", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets the time to wait before retrying to retrieve WAL "
  						 "after a failed attempt."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&wal_retrieve_retry_interval,
  		5000, 1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_segment_size", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the size of write ahead log segments."),
  			NULL,
  			GUC_UNIT_BYTE | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&wal_segment_size,
  		DEFAULT_XLOG_SEG_SIZE,
  		WalSegMinSize,
  		WalSegMaxSize,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"autovacuum_naptime", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Time to sleep between autovacuum runs."),
  			NULL,
  			GUC_UNIT_S
  		},
  		&autovacuum_naptime,
  		60, 1, INT_MAX / 1000,
  		NULL, NULL, NULL
  	},
  	{
  		{"autovacuum_vacuum_threshold", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Minimum number of tuple updates or deletes prior to vacuum."),
  			NULL
  		},
  		&autovacuum_vac_thresh,
  		50, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"autovacuum_vacuum_insert_threshold", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Minimum number of tuple inserts prior to vacuum, or -1 to disable insert vacuums."),
  			NULL
  		},
  		&autovacuum_vac_ins_thresh,
  		1000, -1, INT_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"autovacuum_analyze_threshold", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Minimum number of tuple inserts, updates, or deletes prior to analyze."),
  			NULL
  		},
  		&autovacuum_anl_thresh,
  		50, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		/* see varsup.c for why this is PGC_POSTMASTER not PGC_SIGHUP */
  		{"autovacuum_freeze_max_age", PGC_POSTMASTER, AUTOVACUUM,
  			gettext_noop("Age at which to autovacuum a table to prevent transaction ID wraparound."),
  			NULL
  		},
  		&autovacuum_freeze_max_age,
  
  		/*
  		 * see pg_resetwal and vacuum_failsafe_age if you change the
  		 * upper-limit value.
  		 */
  		200000000, 100000, 2000000000,
  		NULL, NULL, NULL
  	},
  	{
  		/* see multixact.c for why this is PGC_POSTMASTER not PGC_SIGHUP */
  		{"autovacuum_multixact_freeze_max_age", PGC_POSTMASTER, AUTOVACUUM,
  			gettext_noop("Multixact age at which to autovacuum a table to prevent multixact wraparound."),
  			NULL
  		},
  		&autovacuum_multixact_freeze_max_age,
  		400000000, 10000, 2000000000,
  		NULL, NULL, NULL
  	},
  	{
  		/* see max_connections */
  		{"autovacuum_max_workers", PGC_POSTMASTER, AUTOVACUUM,
  			gettext_noop("Sets the maximum number of simultaneously running autovacuum worker processes."),
  			NULL
  		},
  		&autovacuum_max_workers,
  		3, 1, MAX_BACKENDS,
  		check_autovacuum_max_workers, NULL, NULL
  	},
  
  	{
  		{"max_parallel_maintenance_workers", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
  			gettext_noop("Sets the maximum number of parallel processes per maintenance operation."),
  			NULL
  		},
  		&max_parallel_maintenance_workers,
  		2, 0, 1024,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_parallel_workers_per_gather", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
  			gettext_noop("Sets the maximum number of parallel processes per executor node."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&max_parallel_workers_per_gather,
  		2, 0, MAX_PARALLEL_WORKER_LIMIT,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"max_parallel_workers", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
  			gettext_noop("Sets the maximum number of parallel workers that can be active at one time."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&max_parallel_workers,
  		8, 0, MAX_PARALLEL_WORKER_LIMIT,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"autovacuum_work_mem", PGC_SIGHUP, RESOURCES_MEM,
  			gettext_noop("Sets the maximum memory to be used by each autovacuum worker process."),
  			NULL,
  			GUC_UNIT_KB
  		},
  		&autovacuum_work_mem,
  		-1, -1, MAX_KILOBYTES,
  		check_autovacuum_work_mem, NULL, NULL
  	},
  
  	{
  		{"old_snapshot_threshold", PGC_POSTMASTER, RESOURCES_ASYNCHRONOUS,
  			gettext_noop("Time before a snapshot is too old to read pages changed after the snapshot was taken."),
  			gettext_noop("A value of -1 disables this feature."),
  			GUC_UNIT_MIN
  		},
  		&old_snapshot_threshold,
  		-1, -1, MINS_PER_HOUR * HOURS_PER_DAY * 60,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"tcp_keepalives_idle", PGC_USERSET, CONN_AUTH_SETTINGS,
  			gettext_noop("Time between issuing TCP keepalives."),
  			gettext_noop("A value of 0 uses the system default."),
  			GUC_UNIT_S
  		},
  		&tcp_keepalives_idle,
  		0, 0, INT_MAX,
  		NULL, assign_tcp_keepalives_idle, show_tcp_keepalives_idle
  	},
  
  	{
  		{"tcp_keepalives_interval", PGC_USERSET, CONN_AUTH_SETTINGS,
  			gettext_noop("Time between TCP keepalive retransmits."),
  			gettext_noop("A value of 0 uses the system default."),
  			GUC_UNIT_S
  		},
  		&tcp_keepalives_interval,
  		0, 0, INT_MAX,
  		NULL, assign_tcp_keepalives_interval, show_tcp_keepalives_interval
  	},
  
  	{
  		{"ssl_renegotiation_limit", PGC_USERSET, CONN_AUTH_SSL,
  			gettext_noop("SSL renegotiation is no longer supported; this can only be 0."),
  			NULL,
  			GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE,
  		},
  		&ssl_renegotiation_limit,
  		0, 0, 0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"tcp_keepalives_count", PGC_USERSET, CONN_AUTH_SETTINGS,
  			gettext_noop("Maximum number of TCP keepalive retransmits."),
  			gettext_noop("This controls the number of consecutive keepalive retransmits that can be "
  						 "lost before a connection is considered dead. A value of 0 uses the "
  						 "system default."),
  		},
  		&tcp_keepalives_count,
  		0, 0, INT_MAX,
  		NULL, assign_tcp_keepalives_count, show_tcp_keepalives_count
  	},
  
  	{
  		{"gin_fuzzy_search_limit", PGC_USERSET, CLIENT_CONN_OTHER,
  			gettext_noop("Sets the maximum allowed result for exact search by GIN."),
  			NULL,
  			0
  		},
  		&GinFuzzySearchLimit,
  		0, 0, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"effective_cache_size", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the planner's assumption about the total size of the data caches."),
  			gettext_noop("That is, the total size of the caches (kernel cache and shared buffers) used for PostgreSQL data files. "
  						 "This is measured in disk pages, which are normally 8 kB each."),
  			GUC_UNIT_BLOCKS | GUC_EXPLAIN,
  		},
  		&effective_cache_size,
  		DEFAULT_EFFECTIVE_CACHE_SIZE, 1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"min_parallel_table_scan_size", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the minimum amount of table data for a parallel scan."),
  			gettext_noop("If the planner estimates that it will read a number of table pages too small to reach this limit, a parallel scan will not be considered."),
  			GUC_UNIT_BLOCKS | GUC_EXPLAIN,
  		},
  		&min_parallel_table_scan_size,
  		(8 * 1024 * 1024) / BLCKSZ, 0, INT_MAX / 3,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"min_parallel_index_scan_size", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the minimum amount of index data for a parallel scan."),
  			gettext_noop("If the planner estimates that it will read a number of index pages too small to reach this limit, a parallel scan will not be considered."),
  			GUC_UNIT_BLOCKS | GUC_EXPLAIN,
  		},
  		&min_parallel_index_scan_size,
  		(512 * 1024) / BLCKSZ, 0, INT_MAX / 3,
  		NULL, NULL, NULL
  	},
  
  	{
  		/* Can't be set in postgresql.conf */
  		{"server_version_num", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the server version as an integer."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&server_version_num,
  		PG_VERSION_NUM, PG_VERSION_NUM, PG_VERSION_NUM,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_temp_files", PGC_SUSET, LOGGING_WHAT,
  			gettext_noop("Log the use of temporary files larger than this number of kilobytes."),
  			gettext_noop("Zero logs all files. The default is -1 (turning this feature off)."),
  			GUC_UNIT_KB
  		},
  		&log_temp_files,
  		-1, -1, INT_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"track_activity_query_size", PGC_POSTMASTER, STATS_COLLECTOR,
  			gettext_noop("Sets the size reserved for pg_stat_activity.query, in bytes."),
  			NULL,
  			GUC_UNIT_BYTE
  		},
  		&pgstat_track_activity_query_size,
  		1024, 100, 1048576,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"gin_pending_list_limit", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the maximum size of the pending list for GIN index."),
  			NULL,
  			GUC_UNIT_KB
  		},
  		&gin_pending_list_limit,
  		4096, 64, MAX_KILOBYTES,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"tcp_user_timeout", PGC_USERSET, CONN_AUTH_SETTINGS,
  			gettext_noop("TCP user timeout."),
  			gettext_noop("A value of 0 uses the system default."),
  			GUC_UNIT_MS
  		},
  		&tcp_user_timeout,
  		0, 0, INT_MAX,
  		NULL, assign_tcp_user_timeout, show_tcp_user_timeout
  	},
  
  	{
  		{"huge_page_size", PGC_POSTMASTER, RESOURCES_MEM,
  			gettext_noop("The size of huge page that should be requested."),
  			NULL,
  			GUC_UNIT_KB
  		},
  		&huge_page_size,
  		0, 0, INT_MAX,
  		check_huge_page_size, NULL, NULL
  	},
  
  	{
  		{"debug_discard_caches", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Aggressively flush system caches for debugging purposes."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&debug_discard_caches,
  #ifdef DISCARD_CACHES_ENABLED
  		/* Set default based on older compile-time-only cache clobber macros */
  #if defined(CLOBBER_CACHE_RECURSIVELY)
  		3,
  #elif defined(CLOBBER_CACHE_ALWAYS)
  		1,
  #else
  		0,
  #endif
  		0, 5,
  #else							/* not DISCARD_CACHES_ENABLED */
  		0, 0, 0,
  #endif							/* not DISCARD_CACHES_ENABLED */
  		NULL, NULL, NULL
  	},
  
  	{
  		{"client_connection_check_interval", PGC_USERSET, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the time interval between checks for disconnection while running queries."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&client_connection_check_interval,
  		0, 0, INT_MAX,
  		check_client_connection_check_interval, NULL, NULL
  	},
  
  	/* End-of-list marker */
  	{
  		{NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL, NULL
  	}
  };
  
  
  static struct config_real ConfigureNamesReal[] =
  {
  	{
  		{"seq_page_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the planner's estimate of the cost of a "
  						 "sequentially fetched disk page."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&seq_page_cost,
  		DEFAULT_SEQ_PAGE_COST, 0, DBL_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"random_page_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the planner's estimate of the cost of a "
  						 "nonsequentially fetched disk page."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&random_page_cost,
  		DEFAULT_RANDOM_PAGE_COST, 0, DBL_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"cpu_tuple_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the planner's estimate of the cost of "
  						 "processing each tuple (row)."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&cpu_tuple_cost,
  		DEFAULT_CPU_TUPLE_COST, 0, DBL_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"cpu_index_tuple_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the planner's estimate of the cost of "
  						 "processing each index entry during an index scan."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&cpu_index_tuple_cost,
  		DEFAULT_CPU_INDEX_TUPLE_COST, 0, DBL_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"cpu_operator_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the planner's estimate of the cost of "
  						 "processing each operator or function call."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&cpu_operator_cost,
  		DEFAULT_CPU_OPERATOR_COST, 0, DBL_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"parallel_tuple_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the planner's estimate of the cost of "
  						 "passing each tuple (row) from worker to leader backend."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&parallel_tuple_cost,
  		DEFAULT_PARALLEL_TUPLE_COST, 0, DBL_MAX,
  		NULL, NULL, NULL
  	},
  	{
  		{"parallel_setup_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Sets the planner's estimate of the cost of "
  						 "starting up worker processes for parallel query."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&parallel_setup_cost,
  		DEFAULT_PARALLEL_SETUP_COST, 0, DBL_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit_above_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Perform JIT compilation if query is more expensive."),
  			gettext_noop("-1 disables JIT compilation."),
  			GUC_EXPLAIN
  		},
  		&jit_above_cost,
  		100000, -1, DBL_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit_optimize_above_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Optimize JIT-compiled functions if query is more expensive."),
  			gettext_noop("-1 disables optimization."),
  			GUC_EXPLAIN
  		},
  		&jit_optimize_above_cost,
  		500000, -1, DBL_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"jit_inline_above_cost", PGC_USERSET, QUERY_TUNING_COST,
  			gettext_noop("Perform JIT inlining if query is more expensive."),
  			gettext_noop("-1 disables inlining."),
  			GUC_EXPLAIN
  		},
  		&jit_inline_above_cost,
  		500000, -1, DBL_MAX,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"cursor_tuple_fraction", PGC_USERSET, QUERY_TUNING_OTHER,
  			gettext_noop("Sets the planner's estimate of the fraction of "
  						 "a cursor's rows that will be retrieved."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&cursor_tuple_fraction,
  		DEFAULT_CURSOR_TUPLE_FRACTION, 0.0, 1.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"geqo_selection_bias", PGC_USERSET, QUERY_TUNING_GEQO,
  			gettext_noop("GEQO: selective pressure within the population."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&Geqo_selection_bias,
  		DEFAULT_GEQO_SELECTION_BIAS,
  		MIN_GEQO_SELECTION_BIAS, MAX_GEQO_SELECTION_BIAS,
  		NULL, NULL, NULL
  	},
  	{
  		{"geqo_seed", PGC_USERSET, QUERY_TUNING_GEQO,
  			gettext_noop("GEQO: seed for random path selection."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&Geqo_seed,
  		0.0, 0.0, 1.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"hash_mem_multiplier", PGC_USERSET, RESOURCES_MEM,
  			gettext_noop("Multiple of work_mem to use for hash tables."),
  			NULL,
  			GUC_EXPLAIN
  		},
  		&hash_mem_multiplier,
  		1.0, 1.0, 1000.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"bgwriter_lru_multiplier", PGC_SIGHUP, RESOURCES_BGWRITER,
  			gettext_noop("Multiple of the average buffer usage to free per round."),
  			NULL
  		},
  		&bgwriter_lru_multiplier,
  		2.0, 0.0, 10.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"seed", PGC_USERSET, UNGROUPED,
  			gettext_noop("Sets the seed for random-number generation."),
  			NULL,
  			GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&phony_random_seed,
  		0.0, -1.0, 1.0,
  		check_random_seed, assign_random_seed, show_random_seed
  	},
  
  	{
  		{"vacuum_cost_delay", PGC_USERSET, RESOURCES_VACUUM_DELAY,
  			gettext_noop("Vacuum cost delay in milliseconds."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&VacuumCostDelay,
  		0, 0, 100,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"autovacuum_vacuum_cost_delay", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Vacuum cost delay in milliseconds, for autovacuum."),
  			NULL,
  			GUC_UNIT_MS
  		},
  		&autovacuum_vac_cost_delay,
  		2, -1, 100,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"autovacuum_vacuum_scale_factor", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Number of tuple updates or deletes prior to vacuum as a fraction of reltuples."),
  			NULL
  		},
  		&autovacuum_vac_scale,
  		0.2, 0.0, 100.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"autovacuum_vacuum_insert_scale_factor", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Number of tuple inserts prior to vacuum as a fraction of reltuples."),
  			NULL
  		},
  		&autovacuum_vac_ins_scale,
  		0.2, 0.0, 100.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"autovacuum_analyze_scale_factor", PGC_SIGHUP, AUTOVACUUM,
  			gettext_noop("Number of tuple inserts, updates, or deletes prior to analyze as a fraction of reltuples."),
  			NULL
  		},
  		&autovacuum_anl_scale,
  		0.1, 0.0, 100.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"checkpoint_completion_target", PGC_SIGHUP, WAL_CHECKPOINTS,
  			gettext_noop("Time spent flushing dirty buffers during checkpoint, as fraction of checkpoint interval."),
  			NULL
  		},
  		&CheckPointCompletionTarget,
  		0.9, 0.0, 1.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_statement_sample_rate", PGC_SUSET, LOGGING_WHEN,
  			gettext_noop("Fraction of statements exceeding log_min_duration_sample to be logged."),
  			gettext_noop("Use a value between 0.0 (never log) and 1.0 (always log).")
  		},
  		&log_statement_sample_rate,
  		1.0, 0.0, 1.0,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_transaction_sample_rate", PGC_SUSET, LOGGING_WHEN,
  			gettext_noop("Sets the fraction of transactions from which to log all statements."),
  			gettext_noop("Use a value between 0.0 (never log) and 1.0 (log all "
  						 "statements for all transactions).")
  		},
  		&log_xact_sample_rate,
  		0.0, 0.0, 1.0,
  		NULL, NULL, NULL
  	},
  
  	/* End-of-list marker */
  	{
  		{NULL, 0, 0, NULL, NULL}, NULL, 0.0, 0.0, 0.0, NULL, NULL, NULL
  	}
  };
  
  
  static struct config_string ConfigureNamesString[] =
  {
  	{
  		{"archive_command", PGC_SIGHUP, WAL_ARCHIVING,
  			gettext_noop("Sets the shell command that will be called to archive a WAL file."),
  			NULL
  		},
  		&XLogArchiveCommand,
  		"",
  		NULL, NULL, show_archive_command
  	},
  
  	{
  		{"restore_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,
  			gettext_noop("Sets the shell command that will be called to retrieve an archived WAL file."),
  			NULL
  		},
  		&recoveryRestoreCommand,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"archive_cleanup_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,
  			gettext_noop("Sets the shell command that will be executed at every restart point."),
  			NULL
  		},
  		&archiveCleanupCommand,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"recovery_end_command", PGC_SIGHUP, WAL_ARCHIVE_RECOVERY,
  			gettext_noop("Sets the shell command that will be executed once at the end of recovery."),
  			NULL
  		},
  		&recoveryEndCommand,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"recovery_target_timeline", PGC_POSTMASTER, WAL_RECOVERY_TARGET,
  			gettext_noop("Specifies the timeline to recover into."),
  			NULL
  		},
  		&recovery_target_timeline_string,
  		"latest",
  		check_recovery_target_timeline, assign_recovery_target_timeline, NULL
  	},
  
  	{
  		{"recovery_target", PGC_POSTMASTER, WAL_RECOVERY_TARGET,
  			gettext_noop("Set to \"immediate\" to end recovery as soon as a consistent state is reached."),
  			NULL
  		},
  		&recovery_target_string,
  		"",
  		check_recovery_target, assign_recovery_target, NULL
  	},
  	{
  		{"recovery_target_xid", PGC_POSTMASTER, WAL_RECOVERY_TARGET,
  			gettext_noop("Sets the transaction ID up to which recovery will proceed."),
  			NULL
  		},
  		&recovery_target_xid_string,
  		"",
  		check_recovery_target_xid, assign_recovery_target_xid, NULL
  	},
  	{
  		{"recovery_target_time", PGC_POSTMASTER, WAL_RECOVERY_TARGET,
  			gettext_noop("Sets the time stamp up to which recovery will proceed."),
  			NULL
  		},
  		&recovery_target_time_string,
  		"",
  		check_recovery_target_time, assign_recovery_target_time, NULL
  	},
  	{
  		{"recovery_target_name", PGC_POSTMASTER, WAL_RECOVERY_TARGET,
  			gettext_noop("Sets the named restore point up to which recovery will proceed."),
  			NULL
  		},
  		&recovery_target_name_string,
  		"",
  		check_recovery_target_name, assign_recovery_target_name, NULL
  	},
  	{
  		{"recovery_target_lsn", PGC_POSTMASTER, WAL_RECOVERY_TARGET,
  			gettext_noop("Sets the LSN of the write-ahead log location up to which recovery will proceed."),
  			NULL
  		},
  		&recovery_target_lsn_string,
  		"",
  		check_recovery_target_lsn, assign_recovery_target_lsn, NULL
  	},
  
  	{
  		{"promote_trigger_file", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Specifies a file name whose presence ends recovery in the standby."),
  			NULL
  		},
  		&PromoteTriggerFile,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"primary_conninfo", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets the connection string to be used to connect to the sending server."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&PrimaryConnInfo,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"primary_slot_name", PGC_SIGHUP, REPLICATION_STANDBY,
  			gettext_noop("Sets the name of the replication slot to use on the sending server."),
  			NULL
  		},
  		&PrimarySlotName,
  		"",
  		check_primary_slot_name, NULL, NULL
  	},
  
  	{
  		{"client_encoding", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the client's character set encoding."),
  			NULL,
  			GUC_IS_NAME | GUC_REPORT
  		},
  		&client_encoding_string,
  		"SQL_ASCII",
  		check_client_encoding, assign_client_encoding, NULL
  	},
  
  	{
  		{"log_line_prefix", PGC_SIGHUP, LOGGING_WHAT,
  			gettext_noop("Controls information prefixed to each log line."),
  			gettext_noop("If blank, no prefix is used.")
  		},
  		&Log_line_prefix,
  		"%m [%p] ",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_timezone", PGC_SIGHUP, LOGGING_WHAT,
  			gettext_noop("Sets the time zone to use in log messages."),
  			NULL
  		},
  		&log_timezone_string,
  		"GMT",
  		check_log_timezone, assign_log_timezone, show_log_timezone
  	},
  
  	{
  		{"DateStyle", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the display format for date and time values."),
  			gettext_noop("Also controls interpretation of ambiguous "
  						 "date inputs."),
  			GUC_LIST_INPUT | GUC_REPORT
  		},
  		&datestyle_string,
  		"ISO, MDY",
  		check_datestyle, assign_datestyle, NULL
  	},
  
  	{
  		{"default_table_access_method", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the default table access method for new tables."),
  			NULL,
  			GUC_IS_NAME
  		},
  		&default_table_access_method,
  		DEFAULT_TABLE_ACCESS_METHOD,
  		check_default_table_access_method, NULL, NULL
  	},
  
  	{
  		{"default_tablespace", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the default tablespace to create tables and indexes in."),
  			gettext_noop("An empty string selects the database's default tablespace."),
  			GUC_IS_NAME
  		},
  		&default_tablespace,
  		"",
  		check_default_tablespace, NULL, NULL
  	},
  
  	{
  		{"temp_tablespaces", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the tablespace(s) to use for temporary tables and sort files."),
  			NULL,
  			GUC_LIST_INPUT | GUC_LIST_QUOTE
  		},
  		&temp_tablespaces,
  		"",
  		check_temp_tablespaces, assign_temp_tablespaces, NULL
  	},
  
  	{
  		{"dynamic_library_path", PGC_SUSET, CLIENT_CONN_OTHER,
  			gettext_noop("Sets the path for dynamically loadable modules."),
  			gettext_noop("If a dynamically loadable module needs to be opened and "
  						 "the specified name does not have a directory component (i.e., the "
  						 "name does not contain a slash), the system will search this path for "
  						 "the specified file."),
  			GUC_SUPERUSER_ONLY
  		},
  		&Dynamic_library_path,
  		"$libdir",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"krb_server_keyfile", PGC_SIGHUP, CONN_AUTH_AUTH,
  			gettext_noop("Sets the location of the Kerberos server key file."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&pg_krb_server_keyfile,
  		PG_KRB_SRVTAB,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"bonjour_name", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the Bonjour service name."),
  			NULL
  		},
  		&bonjour_name,
  		"",
  		NULL, NULL, NULL
  	},
  
  	/* See main.c about why defaults for LC_foo are not all alike */
  
  	{
  		{"lc_collate", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the collation order locale."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&locale_collate,
  		"C",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"lc_ctype", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the character classification and case conversion locale."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&locale_ctype,
  		"C",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"lc_messages", PGC_SUSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the language in which messages are displayed."),
  			NULL
  		},
  		&locale_messages,
  		"",
  		check_locale_messages, assign_locale_messages, NULL
  	},
  
  	{
  		{"lc_monetary", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the locale for formatting monetary amounts."),
  			NULL
  		},
  		&locale_monetary,
  		"C",
  		check_locale_monetary, assign_locale_monetary, NULL
  	},
  
  	{
  		{"lc_numeric", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the locale for formatting numbers."),
  			NULL
  		},
  		&locale_numeric,
  		"C",
  		check_locale_numeric, assign_locale_numeric, NULL
  	},
  
  	{
  		{"lc_time", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the locale for formatting date and time values."),
  			NULL
  		},
  		&locale_time,
  		"C",
  		check_locale_time, assign_locale_time, NULL
  	},
  
  	{
  		{"session_preload_libraries", PGC_SUSET, CLIENT_CONN_PRELOAD,
  			gettext_noop("Lists shared libraries to preload into each backend."),
  			NULL,
  			GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_SUPERUSER_ONLY
  		},
  		&session_preload_libraries_string,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"shared_preload_libraries", PGC_POSTMASTER, CLIENT_CONN_PRELOAD,
  			gettext_noop("Lists shared libraries to preload into server."),
  			NULL,
  			GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_SUPERUSER_ONLY
  		},
  		&shared_preload_libraries_string,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"local_preload_libraries", PGC_USERSET, CLIENT_CONN_PRELOAD,
  			gettext_noop("Lists unprivileged shared libraries to preload into each backend."),
  			NULL,
  			GUC_LIST_INPUT | GUC_LIST_QUOTE
  		},
  		&local_preload_libraries_string,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"search_path", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the schema search order for names that are not schema-qualified."),
  			NULL,
  			GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_EXPLAIN
  		},
  		&namespace_search_path,
  		"\"$user\", public",
  		check_search_path, assign_search_path, NULL
  	},
  
  	{
  		/* Can't be set in postgresql.conf */
  		{"server_encoding", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the server (database) character set encoding."),
  			NULL,
  			GUC_IS_NAME | GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&server_encoding_string,
  		"SQL_ASCII",
  		NULL, NULL, NULL
  	},
  
  	{
  		/* Can't be set in postgresql.conf */
  		{"server_version", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the server version."),
  			NULL,
  			GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&server_version_string,
  		PG_VERSION,
  		NULL, NULL, NULL
  	},
  
  	{
  		/* Not for general use --- used by SET ROLE */
  		{"role", PGC_USERSET, UNGROUPED,
  			gettext_noop("Sets the current role."),
  			NULL,
  			GUC_IS_NAME | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE | GUC_NOT_WHILE_SEC_REST
  		},
  		&role_string,
  		"none",
  		check_role, assign_role, show_role
  	},
  
  	{
  		/* Not for general use --- used by SET SESSION AUTHORIZATION */
  		{"session_authorization", PGC_USERSET, UNGROUPED,
  			gettext_noop("Sets the session user name."),
  			NULL,
  			GUC_IS_NAME | GUC_REPORT | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE | GUC_NOT_WHILE_SEC_REST
  		},
  		&session_authorization_string,
  		NULL,
  		check_session_authorization, assign_session_authorization, NULL
  	},
  
  	{
  		{"log_destination", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Sets the destination for server log output."),
  			gettext_noop("Valid values are combinations of \"stderr\", "
  						 "\"syslog\", \"csvlog\", and \"eventlog\", "
  						 "depending on the platform."),
  			GUC_LIST_INPUT
  		},
  		&Log_destination_string,
  		"stderr",
  		check_log_destination, assign_log_destination, NULL
  	},
  	{
  		{"log_directory", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Sets the destination directory for log files."),
  			gettext_noop("Can be specified as relative to the data directory "
  						 "or as absolute path."),
  			GUC_SUPERUSER_ONLY
  		},
  		&Log_directory,
  		"log",
  		check_canonical_path, NULL, NULL
  	},
  	{
  		{"log_filename", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Sets the file name pattern for log files."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&Log_filename,
  		"postgresql-%Y-%m-%d_%H%M%S.log",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"syslog_ident", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Sets the program name used to identify PostgreSQL "
  						 "messages in syslog."),
  			NULL
  		},
  		&syslog_ident_str,
  		"postgres",
  		NULL, assign_syslog_ident, NULL
  	},
  
  	{
  		{"event_source", PGC_POSTMASTER, LOGGING_WHERE,
  			gettext_noop("Sets the application name used to identify "
  						 "PostgreSQL messages in the event log."),
  			NULL
  		},
  		&event_source,
  		DEFAULT_EVENT_SOURCE,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"TimeZone", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the time zone for displaying and interpreting time stamps."),
  			NULL,
  			GUC_REPORT
  		},
  		&timezone_string,
  		"GMT",
  		check_timezone, assign_timezone, show_timezone
  	},
  	{
  		{"timezone_abbreviations", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Selects a file of time zone abbreviations."),
  			NULL
  		},
  		&timezone_abbreviations_string,
  		NULL,
  		check_timezone_abbreviations, assign_timezone_abbreviations, NULL
  	},
  
  	{
  		{"unix_socket_group", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the owning group of the Unix-domain socket."),
  			gettext_noop("The owning user of the socket is always the user "
  						 "that starts the server.")
  		},
  		&Unix_socket_group,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"unix_socket_directories", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the directories where Unix-domain sockets will be created."),
  			NULL,
  			GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_SUPERUSER_ONLY
  		},
  		&Unix_socket_directories,
  #ifdef HAVE_UNIX_SOCKETS
  		DEFAULT_PGSOCKET_DIR,
  #else
  		"",
  #endif
  		NULL, NULL, NULL
  	},
  
  	{
  		{"listen_addresses", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
  			gettext_noop("Sets the host name or IP address(es) to listen to."),
  			NULL,
  			GUC_LIST_INPUT
  		},
  		&ListenAddresses,
  		"localhost",
  		NULL, NULL, NULL
  	},
  
  	{
  		/*
  		 * Can't be set by ALTER SYSTEM as it can lead to recursive definition
  		 * of data_directory.
  		 */
  		{"data_directory", PGC_POSTMASTER, FILE_LOCATIONS,
  			gettext_noop("Sets the server's data directory."),
  			NULL,
  			GUC_SUPERUSER_ONLY | GUC_DISALLOW_IN_AUTO_FILE
  		},
  		&data_directory,
  		NULL,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"config_file", PGC_POSTMASTER, FILE_LOCATIONS,
  			gettext_noop("Sets the server's main configuration file."),
  			NULL,
  			GUC_DISALLOW_IN_FILE | GUC_SUPERUSER_ONLY
  		},
  		&ConfigFileName,
  		NULL,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"hba_file", PGC_POSTMASTER, FILE_LOCATIONS,
  			gettext_noop("Sets the server's \"hba\" configuration file."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&HbaFileName,
  		NULL,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ident_file", PGC_POSTMASTER, FILE_LOCATIONS,
  			gettext_noop("Sets the server's \"ident\" configuration file."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&IdentFileName,
  		NULL,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"external_pid_file", PGC_POSTMASTER, FILE_LOCATIONS,
  			gettext_noop("Writes the postmaster PID to the specified file."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&external_pid_file,
  		NULL,
  		check_canonical_path, NULL, NULL
  	},
  
  	{
  		{"ssl_library", PGC_INTERNAL, PRESET_OPTIONS,
  			gettext_noop("Shows the name of the SSL library."),
  			NULL,
  			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&ssl_library,
  #ifdef USE_SSL
  		"OpenSSL",
  #else
  		"",
  #endif
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_cert_file", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Location of the SSL server certificate file."),
  			NULL
  		},
  		&ssl_cert_file,
  		"server.crt",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_key_file", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Location of the SSL server private key file."),
  			NULL
  		},
  		&ssl_key_file,
  		"server.key",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_ca_file", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Location of the SSL certificate authority file."),
  			NULL
  		},
  		&ssl_ca_file,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_crl_file", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Location of the SSL certificate revocation list file."),
  			NULL
  		},
  		&ssl_crl_file,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_crl_dir", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Location of the SSL certificate revocation list directory."),
  			NULL
  		},
  		&ssl_crl_dir,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"stats_temp_directory", PGC_SIGHUP, STATS_COLLECTOR,
  			gettext_noop("Writes temporary statistics files to the specified directory."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&pgstat_temp_directory,
  		PG_STAT_TMP_DIR,
  		check_canonical_path, assign_pgstat_temp_directory, NULL
  	},
  
  	{
  		{"synchronous_standby_names", PGC_SIGHUP, REPLICATION_PRIMARY,
  			gettext_noop("Number of synchronous standbys and list of names of potential synchronous ones."),
  			NULL,
  			GUC_LIST_INPUT
  		},
  		&SyncRepStandbyNames,
  		"",
  		check_synchronous_standby_names, assign_synchronous_standby_names, NULL
  	},
  
  	{
  		{"default_text_search_config", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets default text search configuration."),
  			NULL
  		},
  		&TSCurrentConfig,
  		"pg_catalog.simple",
  		check_TSCurrentConfig, assign_TSCurrentConfig, NULL
  	},
  
  	{
  		{"ssl_ciphers", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Sets the list of allowed SSL ciphers."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&SSLCipherSuites,
  #ifdef USE_OPENSSL
  		"HIGH:MEDIUM:+3DES:!aNULL",
  #else
  		"none",
  #endif
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_ecdh_curve", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Sets the curve to use for ECDH."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&SSLECDHCurve,
  #ifdef USE_SSL
  		"prime256v1",
  #else
  		"none",
  #endif
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_dh_params_file", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Location of the SSL DH parameters file."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&ssl_dh_params_file,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_passphrase_command", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Command to obtain passphrases for SSL."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&ssl_passphrase_command,
  		"",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"application_name", PGC_USERSET, LOGGING_WHAT,
  			gettext_noop("Sets the application name to be reported in statistics and logs."),
  			NULL,
  			GUC_IS_NAME | GUC_REPORT | GUC_NOT_IN_SAMPLE
  		},
  		&application_name,
  		"",
  		check_application_name, assign_application_name, NULL
  	},
  
  	{
  		{"cluster_name", PGC_POSTMASTER, PROCESS_TITLE,
  			gettext_noop("Sets the name of the cluster, which is included in the process title."),
  			NULL,
  			GUC_IS_NAME
  		},
  		&cluster_name,
  		"",
  		check_cluster_name, NULL, NULL
  	},
  
  	{
  		{"wal_consistency_checking", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Sets the WAL resource managers for which WAL consistency checks are done."),
  			gettext_noop("Full-page images will be logged for all data blocks and cross-checked against the results of WAL replay."),
  			GUC_LIST_INPUT | GUC_NOT_IN_SAMPLE
  		},
  		&wal_consistency_checking_string,
  		"",
  		check_wal_consistency_checking, assign_wal_consistency_checking, NULL
  	},
  
  	{
  		{"jit_provider", PGC_POSTMASTER, CLIENT_CONN_PRELOAD,
  			gettext_noop("JIT provider to use."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&jit_provider,
  		"llvmjit",
  		NULL, NULL, NULL
  	},
  
  	{
  		{"backtrace_functions", PGC_SUSET, DEVELOPER_OPTIONS,
  			gettext_noop("Log backtrace for errors in these functions."),
  			NULL,
  			GUC_NOT_IN_SAMPLE
  		},
  		&backtrace_functions,
  		"",
  		check_backtrace_functions, assign_backtrace_functions, NULL
  	},
  
  	/* End-of-list marker */
  	{
  		{NULL, 0, 0, NULL, NULL}, NULL, NULL, NULL, NULL, NULL
  	}
  };
  
  
  static struct config_enum ConfigureNamesEnum[] =
  {
  	{
  		{"backslash_quote", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("Sets whether \"\\'\" is allowed in string literals."),
  			NULL
  		},
  		&backslash_quote,
  		BACKSLASH_QUOTE_SAFE_ENCODING, backslash_quote_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"bytea_output", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the output format for bytea."),
  			NULL
  		},
  		&bytea_output,
  		BYTEA_OUTPUT_HEX, bytea_output_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"client_min_messages", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the message levels that are sent to the client."),
  			gettext_noop("Each level includes all the levels that follow it. The later"
  						 " the level, the fewer messages are sent.")
  		},
  		&client_min_messages,
  		NOTICE, client_message_level_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"compute_query_id", PGC_SUSET, STATS_MONITORING,
  			gettext_noop("Compute query identifiers."),
  			NULL
  		},
  		&compute_query_id,
  		COMPUTE_QUERY_ID_AUTO, compute_query_id_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"constraint_exclusion", PGC_USERSET, QUERY_TUNING_OTHER,
  			gettext_noop("Enables the planner to use constraints to optimize queries."),
  			gettext_noop("Table scans will be skipped if their constraints"
  						 " guarantee that no rows match the query."),
  			GUC_EXPLAIN
  		},
  		&constraint_exclusion,
  		CONSTRAINT_EXCLUSION_PARTITION, constraint_exclusion_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"default_toast_compression", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the default compression method for compressible values."),
  			NULL
  		},
  		&default_toast_compression,
  		TOAST_PGLZ_COMPRESSION,
  		default_toast_compression_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"default_transaction_isolation", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the transaction isolation level of each new transaction."),
  			NULL
  		},
  		&DefaultXactIsoLevel,
  		XACT_READ_COMMITTED, isolation_level_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"transaction_isolation", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the current transaction's isolation level."),
  			NULL,
  			GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
  		},
  		&XactIsoLevel,
  		XACT_READ_COMMITTED, isolation_level_options,
  		check_XactIsoLevel, NULL, NULL
  	},
  
  	{
  		{"IntervalStyle", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the display format for interval values."),
  			NULL,
  			GUC_REPORT
  		},
  		&IntervalStyle,
  		INTSTYLE_POSTGRES, intervalstyle_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_error_verbosity", PGC_SUSET, LOGGING_WHAT,
  			gettext_noop("Sets the verbosity of logged messages."),
  			NULL
  		},
  		&Log_error_verbosity,
  		PGERROR_DEFAULT, log_error_verbosity_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_min_messages", PGC_SUSET, LOGGING_WHEN,
  			gettext_noop("Sets the message levels that are logged."),
  			gettext_noop("Each level includes all the levels that follow it. The later"
  						 " the level, the fewer messages are sent.")
  		},
  		&log_min_messages,
  		WARNING, server_message_level_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_min_error_statement", PGC_SUSET, LOGGING_WHEN,
  			gettext_noop("Causes all statements generating error at or above this level to be logged."),
  			gettext_noop("Each level includes all the levels that follow it. The later"
  						 " the level, the fewer messages are sent.")
  		},
  		&log_min_error_statement,
  		ERROR, server_message_level_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"log_statement", PGC_SUSET, LOGGING_WHAT,
  			gettext_noop("Sets the type of statements logged."),
  			NULL
  		},
  		&log_statement,
  		LOGSTMT_NONE, log_statement_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"syslog_facility", PGC_SIGHUP, LOGGING_WHERE,
  			gettext_noop("Sets the syslog \"facility\" to be used when syslog enabled."),
  			NULL
  		},
  		&syslog_facility,
  #ifdef HAVE_SYSLOG
  		LOG_LOCAL0,
  #else
  		0,
  #endif
  		syslog_facility_options,
  		NULL, assign_syslog_facility, NULL
  	},
  
  	{
  		{"session_replication_role", PGC_SUSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the session's behavior for triggers and rewrite rules."),
  			NULL
  		},
  		&SessionReplicationRole,
  		SESSION_REPLICATION_ROLE_ORIGIN, session_replication_role_options,
  		NULL, assign_session_replication_role, NULL
  	},
  
  	{
  		{"synchronous_commit", PGC_USERSET, WAL_SETTINGS,
  			gettext_noop("Sets the current transaction's synchronization level."),
  			NULL
  		},
  		&synchronous_commit,
  		SYNCHRONOUS_COMMIT_ON, synchronous_commit_options,
  		NULL, assign_synchronous_commit, NULL
  	},
  
  	{
  		{"archive_mode", PGC_POSTMASTER, WAL_ARCHIVING,
  			gettext_noop("Allows archiving of WAL files using archive_command."),
  			NULL
  		},
  		&XLogArchiveMode,
  		ARCHIVE_MODE_OFF, archive_mode_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"recovery_target_action", PGC_POSTMASTER, WAL_RECOVERY_TARGET,
  			gettext_noop("Sets the action to perform upon reaching the recovery target."),
  			NULL
  		},
  		&recoveryTargetAction,
  		RECOVERY_TARGET_ACTION_PAUSE, recovery_target_action_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"trace_recovery_messages", PGC_SIGHUP, DEVELOPER_OPTIONS,
  			gettext_noop("Enables logging of recovery-related debugging information."),
  			gettext_noop("Each level includes all the levels that follow it. The later"
  						 " the level, the fewer messages are sent.")
  		},
  		&trace_recovery_messages,
  
  		/*
  		 * client_message_level_options allows too many values, really, but
  		 * it's not worth having a separate options array for this.
  		 */
  		LOG, client_message_level_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"track_functions", PGC_SUSET, STATS_COLLECTOR,
  			gettext_noop("Collects function-level statistics on database activity."),
  			NULL
  		},
  		&pgstat_track_functions,
  		TRACK_FUNC_OFF, track_function_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_level", PGC_POSTMASTER, WAL_SETTINGS,
  			gettext_noop("Sets the level of information written to the WAL."),
  			NULL
  		},
  		&wal_level,
  		WAL_LEVEL_REPLICA, wal_level_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
  			gettext_noop("Selects the dynamic shared memory implementation used."),
  			NULL
  		},
  		&dynamic_shared_memory_type,
  		DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE, dynamic_shared_memory_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
  			gettext_noop("Selects the shared memory implementation used for the main shared memory region."),
  			NULL
  		},
  		&shared_memory_type,
  		DEFAULT_SHARED_MEMORY_TYPE, shared_memory_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"wal_sync_method", PGC_SIGHUP, WAL_SETTINGS,
  			gettext_noop("Selects the method used for forcing WAL updates to disk."),
  			NULL
  		},
  		&sync_method,
  		DEFAULT_SYNC_METHOD, sync_method_options,
  		NULL, assign_xlog_sync_method, NULL
  	},
  
  	{
  		{"xmlbinary", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets how binary values are to be encoded in XML."),
  			NULL
  		},
  		&xmlbinary,
  		XMLBINARY_BASE64, xmlbinary_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"xmloption", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets whether XML data in implicit parsing and serialization "
  						 "operations is to be considered as documents or content fragments."),
  			NULL
  		},
  		&xmloption,
  		XMLOPTION_CONTENT, xmloption_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"huge_pages", PGC_POSTMASTER, RESOURCES_MEM,
  			gettext_noop("Use of huge pages on Linux or Windows."),
  			NULL
  		},
  		&huge_pages,
  		HUGE_PAGES_TRY, huge_pages_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"force_parallel_mode", PGC_USERSET, DEVELOPER_OPTIONS,
  			gettext_noop("Forces use of parallel query facilities."),
  			gettext_noop("If possible, run query using a parallel worker and with parallel restrictions."),
  			GUC_NOT_IN_SAMPLE | GUC_EXPLAIN
  		},
  		&force_parallel_mode,
  		FORCE_PARALLEL_OFF, force_parallel_mode_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"password_encryption", PGC_USERSET, CONN_AUTH_AUTH,
  			gettext_noop("Chooses the algorithm for encrypting passwords."),
  			NULL
  		},
  		&Password_encryption,
  		PASSWORD_TYPE_SCRAM_SHA_256, password_encryption_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"plan_cache_mode", PGC_USERSET, QUERY_TUNING_OTHER,
  			gettext_noop("Controls the planner's selection of custom or generic plan."),
  			gettext_noop("Prepared statements can have custom and generic plans, and the planner "
  						 "will attempt to choose which is better.  This can be set to override "
  						 "the default behavior."),
  			GUC_EXPLAIN
  		},
  		&plan_cache_mode,
  		PLAN_CACHE_MODE_AUTO, plan_cache_mode_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_min_protocol_version", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Sets the minimum SSL/TLS protocol version to use."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&ssl_min_protocol_version,
  		PG_TLS1_2_VERSION,
  		ssl_protocol_versions_info + 1, /* don't allow PG_TLS_ANY */
  		NULL, NULL, NULL
  	},
  
  	{
  		{"ssl_max_protocol_version", PGC_SIGHUP, CONN_AUTH_SSL,
  			gettext_noop("Sets the maximum SSL/TLS protocol version to use."),
  			NULL,
  			GUC_SUPERUSER_ONLY
  		},
  		&ssl_max_protocol_version,
  		PG_TLS_ANY,
  		ssl_protocol_versions_info,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"recovery_init_sync_method", PGC_SIGHUP, ERROR_HANDLING_OPTIONS,
  			gettext_noop("Sets the method for synchronizing the data directory before crash recovery."),
  		},
  		&recovery_init_sync_method,
  		RECOVERY_INIT_SYNC_METHOD_FSYNC, recovery_init_sync_method_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"nls_length_semantics", PGC_USERSET, DEVELOPER_OPTIONS,
  			gettext_noop("create CHAR and VARCHAR2 columns using either byte or character length semantics."),
  			NULL,
  			GUC_REPORT
  		},
  		&nls_length_semantics,
  		NLSLENGTH_NONE, nlslength_options,
  		NULL, NULL, NULL
  	},
  
  	{
  		{"compatible_mode", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
  			gettext_noop("database compatible options."),
  			NULL,
  			GUC_REPORT
  		},
  		&compatible_db,
  		COMPATIBLE_NONE,
  		compat_options,
  		NULL, assign_compatible_db, NULL
  	},
  
  	/* End-of-list marker */
  	{
  		{NULL, 0, 0, NULL, NULL}, NULL, 0, NULL, NULL, NULL, NULL
  	}
  };
  
  /******** end of options list ********/
  
  
  /*
   * To allow continued support of obsolete names for GUC variables, we apply
   * the following mappings to any unrecognized name.  Note that an old name
   * should be mapped to a new one only if the new variable has very similar
   * semantics to the old.
   */
  static const char *const map_old_guc_names[] = {
  	"sort_mem", "work_mem",
  	"vacuum_mem", "maintenance_work_mem",
  	NULL
  };
  
  
  /*
   * Actual lookup of variables is done through this single, sorted array.
   */
  static struct config_generic **guc_variables;
  
  /* Current number of variables contained in the vector */
  static int	num_guc_variables;
  
  /* Vector capacity */
  static int	size_guc_variables;
  
  
  static bool guc_dirty;			/* true if need to do commit/abort work */
  
  static bool reporting_enabled;	/* true to enable GUC_REPORT */
  
  static bool report_needed;		/* true if any GUC_REPORT reports are needed */
  
  static int	GUCNestLevel = 0;	/* 1 when in main transaction */
  
  
  static int	guc_var_compare(const void *a, const void *b);
  static int	guc_name_compare(const char *namea, const char *nameb);
  static void InitializeGUCOptionsFromEnvironment(void);
  static void InitializeOneGUCOption(struct config_generic *gconf);
  static void push_old_value(struct config_generic *gconf, GucAction action);
  static void ReportGUCOption(struct config_generic *record);
  static void reapply_stacked_values(struct config_generic *variable,
  								   struct config_string *pHolder,
  								   GucStack *stack,
  								   const char *curvalue,
  								   GucContext curscontext, GucSource cursource);
  static void ShowGUCConfigOption(const char *name, DestReceiver *dest);
  static void ShowAllGUCConfig(DestReceiver *dest);
  static char *_ShowOption(struct config_generic *record, bool use_units);
  static bool validate_option_array_item(const char *name, const char *value,
  									   bool skipIfNoPermissions);
  static void write_auto_conf_file(int fd, const char *filename, ConfigVariable *head_p);
  static void replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
  									  const char *name, const char *value);
  
  
  /*
   * Some infrastructure for checking malloc/strdup/realloc calls
   */
  static void *
  guc_malloc(int elevel, size_t size)
  {
  	void	   *data;
  
  	/* Avoid unportable behavior of malloc(0) */
  	if (size == 0)
  		size = 1;
  	data = malloc(size);
  	if (data == NULL)
  		ereport(elevel,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  	return data;
  }
  
  static void *
  guc_realloc(int elevel, void *old, size_t size)
  {
  	void	   *data;
  
  	/* Avoid unportable behavior of realloc(NULL, 0) */
  	if (old == NULL && size == 0)
  		size = 1;
  	data = realloc(old, size);
  	if (data == NULL)
  		ereport(elevel,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  	return data;
  }
  
  static char *
  guc_strdup(int elevel, const char *src)
  {
  	char	   *data;
  
  	data = strdup(src);
  	if (data == NULL)
  		ereport(elevel,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  	return data;
  }
  
  
  /*
   * Detect whether strval is referenced anywhere in a GUC string item
   */
  static bool
  string_field_used(struct config_string *conf, char *strval)
  {
  	GucStack   *stack;
  
  	if (strval == *(conf->variable) ||
  		strval == conf->reset_val ||
  		strval == conf->boot_val)
  		return true;
  	for (stack = conf->gen.stack; stack; stack = stack->prev)
  	{
  		if (strval == stack->prior.val.stringval ||
  			strval == stack->masked.val.stringval)
  			return true;
  	}
  	return false;
  }
  
  /*
   * Support for assigning to a field of a string GUC item.  Free the prior
   * value if it's not referenced anywhere else in the item (including stacked
   * states).
   */
  static void
  set_string_field(struct config_string *conf, char **field, char *newval)
  {
  	char	   *oldval = *field;
  
  	/* Do the assignment */
  	*field = newval;
  
  	/* Free old value if it's not NULL and isn't referenced anymore */
  	if (oldval && !string_field_used(conf, oldval))
  		free(oldval);
  }
  
  /*
   * Detect whether an "extra" struct is referenced anywhere in a GUC item
   */
  static bool
  extra_field_used(struct config_generic *gconf, void *extra)
  {
  	GucStack   *stack;
  
  	if (extra == gconf->extra)
  		return true;
  	switch (gconf->vartype)
  	{
  		case PGC_BOOL:
  			if (extra == ((struct config_bool *) gconf)->reset_extra)
  				return true;
  			break;
  		case PGC_INT:
  			if (extra == ((struct config_int *) gconf)->reset_extra)
  				return true;
  			break;
  		case PGC_REAL:
  			if (extra == ((struct config_real *) gconf)->reset_extra)
  				return true;
  			break;
  		case PGC_STRING:
  			if (extra == ((struct config_string *) gconf)->reset_extra)
  				return true;
  			break;
  		case PGC_ENUM:
  			if (extra == ((struct config_enum *) gconf)->reset_extra)
  				return true;
  			break;
  	}
  	for (stack = gconf->stack; stack; stack = stack->prev)
  	{
  		if (extra == stack->prior.extra ||
  			extra == stack->masked.extra)
  			return true;
  	}
  
  	return false;
  }
  
  /*
   * Support for assigning to an "extra" field of a GUC item.  Free the prior
   * value if it's not referenced anywhere else in the item (including stacked
   * states).
   */
  static void
  set_extra_field(struct config_generic *gconf, void **field, void *newval)
  {
  	void	   *oldval = *field;
  
  	/* Do the assignment */
  	*field = newval;
  
  	/* Free old value if it's not NULL and isn't referenced anymore */
  	if (oldval && !extra_field_used(gconf, oldval))
  		free(oldval);
  }
  
  /*
   * Support for copying a variable's active value into a stack entry.
   * The "extra" field associated with the active value is copied, too.
   *
   * NB: be sure stringval and extra fields of a new stack entry are
   * initialized to NULL before this is used, else we'll try to free() them.
   */
  static void
  set_stack_value(struct config_generic *gconf, config_var_value *val)
  {
  	switch (gconf->vartype)
  	{
  		case PGC_BOOL:
  			val->val.boolval =
  				*((struct config_bool *) gconf)->variable;
  			break;
  		case PGC_INT:
  			val->val.intval =
  				*((struct config_int *) gconf)->variable;
  			break;
  		case PGC_REAL:
  			val->val.realval =
  				*((struct config_real *) gconf)->variable;
  			break;
  		case PGC_STRING:
  			set_string_field((struct config_string *) gconf,
  							 &(val->val.stringval),
  							 *((struct config_string *) gconf)->variable);
  			break;
  		case PGC_ENUM:
  			val->val.enumval =
  				*((struct config_enum *) gconf)->variable;
  			break;
  	}
  	set_extra_field(gconf, &(val->extra), gconf->extra);
  }
  
  /*
   * Support for discarding a no-longer-needed value in a stack entry.
   * The "extra" field associated with the stack entry is cleared, too.
   */
  static void
  discard_stack_value(struct config_generic *gconf, config_var_value *val)
  {
  	switch (gconf->vartype)
  	{
  		case PGC_BOOL:
  		case PGC_INT:
  		case PGC_REAL:
  		case PGC_ENUM:
  			/* no need to do anything */
  			break;
  		case PGC_STRING:
  			set_string_field((struct config_string *) gconf,
  							 &(val->val.stringval),
  							 NULL);
  			break;
  	}
  	set_extra_field(gconf, &(val->extra), NULL);
  }
  
  
  /*
   * Fetch the sorted array pointer (exported for help_config.c's use ONLY)
   */
  struct config_generic **
  get_guc_variables(void)
  {
  	return guc_variables;
  }
  
  
  /*
   * Build the sorted array.  This is split out so that it could be
   * re-executed after startup (e.g., we could allow loadable modules to
   * add vars, and then we'd need to re-sort).
   */
  void
  build_guc_variables(void)
  {
  	int			size_vars;
  	int			num_vars = 0;
  	struct config_generic **guc_vars;
  	int			i;
  
  	for (i = 0; ConfigureNamesBool[i].gen.name; i++)
  	{
  		struct config_bool *conf = &ConfigureNamesBool[i];
  
  		/* Rather than requiring vartype to be filled in by hand, do this: */
  		conf->gen.vartype = PGC_BOOL;
  		num_vars++;
  	}
  
  	for (i = 0; ConfigureNamesInt[i].gen.name; i++)
  	{
  		struct config_int *conf = &ConfigureNamesInt[i];
  
  		conf->gen.vartype = PGC_INT;
  		num_vars++;
  	}
  
  	for (i = 0; ConfigureNamesReal[i].gen.name; i++)
  	{
  		struct config_real *conf = &ConfigureNamesReal[i];
  
  		conf->gen.vartype = PGC_REAL;
  		num_vars++;
  	}
  
  	for (i = 0; ConfigureNamesString[i].gen.name; i++)
  	{
  		struct config_string *conf = &ConfigureNamesString[i];
  
  		conf->gen.vartype = PGC_STRING;
  		num_vars++;
  	}
  
  	for (i = 0; ConfigureNamesEnum[i].gen.name; i++)
  	{
  		struct config_enum *conf = &ConfigureNamesEnum[i];
  
  		conf->gen.vartype = PGC_ENUM;
  		num_vars++;
  	}
  
  	/*
  	 * Create table with 20% slack
  	 */
  	size_vars = num_vars + num_vars / 4;
  
  	guc_vars = (struct config_generic **)
  		guc_malloc(FATAL, size_vars * sizeof(struct config_generic *));
  
  	num_vars = 0;
  
  	for (i = 0; ConfigureNamesBool[i].gen.name; i++)
  		guc_vars[num_vars++] = &ConfigureNamesBool[i].gen;
  
  	for (i = 0; ConfigureNamesInt[i].gen.name; i++)
  		guc_vars[num_vars++] = &ConfigureNamesInt[i].gen;
  
  	for (i = 0; ConfigureNamesReal[i].gen.name; i++)
  		guc_vars[num_vars++] = &ConfigureNamesReal[i].gen;
  
  	for (i = 0; ConfigureNamesString[i].gen.name; i++)
  		guc_vars[num_vars++] = &ConfigureNamesString[i].gen;
  
  	for (i = 0; ConfigureNamesEnum[i].gen.name; i++)
  		guc_vars[num_vars++] = &ConfigureNamesEnum[i].gen;
  
  	if (guc_variables)
  		free(guc_variables);
  	guc_variables = guc_vars;
  	num_guc_variables = num_vars;
  	size_guc_variables = size_vars;
  	qsort((void *) guc_variables, num_guc_variables,
  		  sizeof(struct config_generic *), guc_var_compare);
  }
  
  /*
   * Add a new GUC variable to the list of known variables. The
   * list is expanded if needed.
   */
  static bool
  add_guc_variable(struct config_generic *var, int elevel)
  {
  	if (num_guc_variables + 1 >= size_guc_variables)
  	{
  		/*
  		 * Increase the vector by 25%
  		 */
  		int			size_vars = size_guc_variables + size_guc_variables / 4;
  		struct config_generic **guc_vars;
  
  		if (size_vars == 0)
  		{
  			size_vars = 100;
  			guc_vars = (struct config_generic **)
  				guc_malloc(elevel, size_vars * sizeof(struct config_generic *));
  		}
  		else
  		{
  			guc_vars = (struct config_generic **)
  				guc_realloc(elevel, guc_variables, size_vars * sizeof(struct config_generic *));
  		}
  
  		if (guc_vars == NULL)
  			return false;		/* out of memory */
  
  		guc_variables = guc_vars;
  		size_guc_variables = size_vars;
  	}
  	guc_variables[num_guc_variables++] = var;
  	qsort((void *) guc_variables, num_guc_variables,
  		  sizeof(struct config_generic *), guc_var_compare);
  	return true;
  }
  
  /*
   * Decide whether a proposed custom variable name is allowed.
   *
   * It must be two or more identifiers separated by dots, where the rules
   * for what is an identifier agree with scan.l.  (If you change this rule,
   * adjust the errdetail in find_option().)
   */
  static bool
  valid_custom_variable_name(const char *name)
  {
  	bool		saw_sep = false;
  	bool		name_start = true;
  
  	for (const char *p = name; *p; p++)
  	{
  		if (*p == GUC_QUALIFIER_SEPARATOR)
  		{
  			if (name_start)
  				return false;	/* empty name component */
  			saw_sep = true;
  			name_start = true;
  		}
  		else if (strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  						"abcdefghijklmnopqrstuvwxyz", *p) != NULL ||
  				 IS_HIGHBIT_SET(*p))
  		{
  			/* okay as first or non-first character */
  			name_start = false;
  		}
  		else if (!name_start && strchr("0123456789_$", *p) != NULL)
  			 /* okay as non-first character */ ;
  		else
  			return false;
  	}
  	if (name_start)
  		return false;			/* empty name component */
  	/* OK if we found at least one separator */
  	return saw_sep;
  }
  
  /*
   * Create and add a placeholder variable for a custom variable name.
   */
  static struct config_generic *
  add_placeholder_variable(const char *name, int elevel)
  {
  	size_t		sz = sizeof(struct config_string) + sizeof(char *);
  	struct config_string *var;
  	struct config_generic *gen;
  
  	var = (struct config_string *) guc_malloc(elevel, sz);
  	if (var == NULL)
  		return NULL;
  	memset(var, 0, sz);
  	gen = &var->gen;
  
  	gen->name = guc_strdup(elevel, name);
  	if (gen->name == NULL)
  	{
  		free(var);
  		return NULL;
  	}
  
  	gen->context = PGC_USERSET;
  	gen->group = CUSTOM_OPTIONS;
  	gen->short_desc = "GUC placeholder variable";
  	gen->flags = GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE | GUC_CUSTOM_PLACEHOLDER;
  	gen->vartype = PGC_STRING;
  
  	/*
  	 * The char* is allocated at the end of the struct since we have no
  	 * 'static' place to point to.  Note that the current value, as well as
  	 * the boot and reset values, start out NULL.
  	 */
  	var->variable = (char **) (var + 1);
  
  	if (!add_guc_variable((struct config_generic *) var, elevel))
  	{
  		free(unconstify(char *, gen->name));
  		free(var);
  		return NULL;
  	}
  
  	return gen;
  }
  
  /*
   * Look up option "name".  If it exists, return a pointer to its record.
   * Otherwise, if create_placeholders is true and name is a valid-looking
   * custom variable name, we'll create and return a placeholder record.
   * Otherwise, if skip_errors is true, then we silently return NULL for
   * an unrecognized or invalid name.  Otherwise, the error is reported at
   * error level elevel (and we return NULL if that's less than ERROR).
   *
   * Note: internal errors, primarily out-of-memory, draw an elevel-level
   * report and NULL return regardless of skip_errors.  Hence, callers must
   * handle a NULL return whenever elevel < ERROR, but they should not need
   * to emit any additional error message.  (In practice, internal errors
   * can only happen when create_placeholders is true, so callers passing
   * false need not think terribly hard about this.)
   */
  static struct config_generic *
  find_option(const char *name, bool create_placeholders, bool skip_errors,
  			int elevel)
  {
  	const char **key = &name;
  	struct config_generic **res;
  	int			i;
  
  	Assert(name);
  
  	/*
  	 * By equating const char ** with struct config_generic *, we are assuming
  	 * the name field is first in config_generic.
  	 */
  	res = (struct config_generic **) bsearch((void *) &key,
  											 (void *) guc_variables,
  											 num_guc_variables,
  											 sizeof(struct config_generic *),
  											 guc_var_compare);
  	if (res)
  		return *res;
  
  	/*
  	 * See if the name is an obsolete name for a variable.  We assume that the
  	 * set of supported old names is short enough that a brute-force search is
  	 * the best way.
  	 */
  	for (i = 0; map_old_guc_names[i] != NULL; i += 2)
  	{
  		if (guc_name_compare(name, map_old_guc_names[i]) == 0)
  			return find_option(map_old_guc_names[i + 1], false,
  							   skip_errors, elevel);
  	}
  
  	if (create_placeholders)
  	{
  		/*
  		 * Check if the name is valid, and if so, add a placeholder.  If it
  		 * doesn't contain a separator, don't assume that it was meant to be a
  		 * placeholder.
  		 */
  		if (strchr(name, GUC_QUALIFIER_SEPARATOR) != NULL)
  		{
  			if (valid_custom_variable_name(name))
  				return add_placeholder_variable(name, elevel);
  			/* A special error message seems desirable here */
  			if (!skip_errors)
  				ereport(elevel,
  						(errcode(ERRCODE_INVALID_NAME),
  						 errmsg("invalid configuration parameter name \"%s\"",
  								name),
  						 errdetail("Custom parameter names must be two or more simple identifiers separated by dots.")));
  			return NULL;
  		}
  	}
  
  	/* Unknown name */
  	if (!skip_errors)
  		ereport(elevel,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("unrecognized configuration parameter \"%s\"",
  						name)));
  	return NULL;
  }
  
  
  /*
   * comparator for qsorting and bsearching guc_variables array
   */
  static int
  guc_var_compare(const void *a, const void *b)
  {
  	const struct config_generic *confa = *(struct config_generic *const *) a;
  	const struct config_generic *confb = *(struct config_generic *const *) b;
  
  	return guc_name_compare(confa->name, confb->name);
  }
  
  /*
   * the bare comparison function for GUC names
   */
  static int
  guc_name_compare(const char *namea, const char *nameb)
  {
  	/*
  	 * The temptation to use strcasecmp() here must be resisted, because the
  	 * array ordering has to remain stable across setlocale() calls. So, build
  	 * our own with a simple ASCII-only downcasing.
  	 */
  	while (*namea && *nameb)
  	{
  		char		cha = *namea++;
  		char		chb = *nameb++;
  
  		if (cha >= 'A' && cha <= 'Z')
  			cha += 'a' - 'A';
  		if (chb >= 'A' && chb <= 'Z')
  			chb += 'a' - 'A';
  		if (cha != chb)
  			return cha - chb;
  	}
  	if (*namea)
  		return 1;				/* a is longer */
  	if (*nameb)
  		return -1;				/* b is longer */
  	return 0;
  }
  
  
  /*
   * Initialize GUC options during program startup.
   *
   * Note that we cannot read the config file yet, since we have not yet
   * processed command-line switches.
   */
  void
  InitializeGUCOptions(void)
  {
  	int			i;
  
  	/*
  	 * Before log_line_prefix could possibly receive a nonempty setting, make
  	 * sure that timezone processing is minimally alive (see elog.c).
  	 */
  	pg_timezone_initialize();
  
  	/*
  	 * Build sorted array of all GUC variables.
  	 */
  	build_guc_variables();
  
  	/*
  	 * Load all variables with their compiled-in defaults, and initialize
  	 * status fields as needed.
  	 */
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		InitializeOneGUCOption(guc_variables[i]);
  	}
  
  	guc_dirty = false;
  
  	reporting_enabled = false;
  
  	/*
  	 * Prevent any attempt to override the transaction modes from
  	 * non-interactive sources.
  	 */
  	SetConfigOption("transaction_isolation", "read committed",
  					PGC_POSTMASTER, PGC_S_OVERRIDE);
  	SetConfigOption("transaction_read_only", "no",
  					PGC_POSTMASTER, PGC_S_OVERRIDE);
  	SetConfigOption("transaction_deferrable", "no",
  					PGC_POSTMASTER, PGC_S_OVERRIDE);
  
  	/*
  	 * For historical reasons, some GUC parameters can receive defaults from
  	 * environment variables.  Process those settings.
  	 */
  	InitializeGUCOptionsFromEnvironment();
  }
  
  /*
   * Assign any GUC values that can come from the server's environment.
   *
   * This is called from InitializeGUCOptions, and also from ProcessConfigFile
   * to deal with the possibility that a setting has been removed from
   * postgresql.conf and should now get a value from the environment.
   * (The latter is a kludge that should probably go away someday; if so,
   * fold this back into InitializeGUCOptions.)
   */
  static void
  InitializeGUCOptionsFromEnvironment(void)
  {
  	char	   *env;
  	long		stack_rlimit;
  
  	env = getenv("PGPORT");
  	if (env != NULL)
  		SetConfigOption("port", env, PGC_POSTMASTER, PGC_S_ENV_VAR);
  
  	env = getenv("PGDATESTYLE");
  	if (env != NULL)
  		SetConfigOption("datestyle", env, PGC_POSTMASTER, PGC_S_ENV_VAR);
  
  	env = getenv("PGCLIENTENCODING");
  	if (env != NULL)
  		SetConfigOption("client_encoding", env, PGC_POSTMASTER, PGC_S_ENV_VAR);
  
  	/*
  	 * rlimit isn't exactly an "environment variable", but it behaves about
  	 * the same.  If we can identify the platform stack depth rlimit, increase
  	 * default stack depth setting up to whatever is safe (but at most 2MB).
  	 */
  	stack_rlimit = get_stack_depth_rlimit();
  	if (stack_rlimit > 0)
  	{
  		long		new_limit = (stack_rlimit - STACK_DEPTH_SLOP) / 1024L;
  
  		if (new_limit > 100)
  		{
  			char		limbuf[16];
  
  			new_limit = Min(new_limit, 2048);
  			sprintf(limbuf, "%ld", new_limit);
  			SetConfigOption("max_stack_depth", limbuf,
  							PGC_POSTMASTER, PGC_S_ENV_VAR);
  		}
  	}
  }
  
  /*
   * Initialize one GUC option variable to its compiled-in default.
   *
   * Note: the reason for calling check_hooks is not that we think the boot_val
   * might fail, but that the hooks might wish to compute an "extra" struct.
   */
  static void
  InitializeOneGUCOption(struct config_generic *gconf)
  {
  	gconf->status = 0;
  	gconf->source = PGC_S_DEFAULT;
  	gconf->reset_source = PGC_S_DEFAULT;
  	gconf->scontext = PGC_INTERNAL;
  	gconf->reset_scontext = PGC_INTERNAL;
  	gconf->stack = NULL;
  	gconf->extra = NULL;
  	gconf->last_reported = NULL;
  	gconf->sourcefile = NULL;
  	gconf->sourceline = 0;
  
  	switch (gconf->vartype)
  	{
  		case PGC_BOOL:
  			{
  				struct config_bool *conf = (struct config_bool *) gconf;
  				bool		newval = conf->boot_val;
  				void	   *extra = NULL;
  
  				if (!call_bool_check_hook(conf, &newval, &extra,
  										  PGC_S_DEFAULT, LOG))
  					elog(FATAL, "failed to initialize %s to %d",
  						 conf->gen.name, (int) newval);
  				if (conf->assign_hook)
  					conf->assign_hook(newval, extra);
  				*conf->variable = conf->reset_val = newval;
  				conf->gen.extra = conf->reset_extra = extra;
  				break;
  			}
  		case PGC_INT:
  			{
  				struct config_int *conf = (struct config_int *) gconf;
  				int			newval = conf->boot_val;
  				void	   *extra = NULL;
  
  				Assert(newval >= conf->min);
  				Assert(newval <= conf->max);
  				if (!call_int_check_hook(conf, &newval, &extra,
  										 PGC_S_DEFAULT, LOG))
  					elog(FATAL, "failed to initialize %s to %d",
  						 conf->gen.name, newval);
  				if (conf->assign_hook)
  					conf->assign_hook(newval, extra);
  				*conf->variable = conf->reset_val = newval;
  				conf->gen.extra = conf->reset_extra = extra;
  				break;
  			}
  		case PGC_REAL:
  			{
  				struct config_real *conf = (struct config_real *) gconf;
  				double		newval = conf->boot_val;
  				void	   *extra = NULL;
  
  				Assert(newval >= conf->min);
  				Assert(newval <= conf->max);
  				if (!call_real_check_hook(conf, &newval, &extra,
  										  PGC_S_DEFAULT, LOG))
  					elog(FATAL, "failed to initialize %s to %g",
  						 conf->gen.name, newval);
  				if (conf->assign_hook)
  					conf->assign_hook(newval, extra);
  				*conf->variable = conf->reset_val = newval;
  				conf->gen.extra = conf->reset_extra = extra;
  				break;
  			}
  		case PGC_STRING:
  			{
  				struct config_string *conf = (struct config_string *) gconf;
  				char	   *newval;
  				void	   *extra = NULL;
  
  				/* non-NULL boot_val must always get strdup'd */
  				if (conf->boot_val != NULL)
  					newval = guc_strdup(FATAL, conf->boot_val);
  				else
  					newval = NULL;
  
  				if (!call_string_check_hook(conf, &newval, &extra,
  											PGC_S_DEFAULT, LOG))
  					elog(FATAL, "failed to initialize %s to \"%s\"",
  						 conf->gen.name, newval ? newval : "");
  				if (conf->assign_hook)
  					conf->assign_hook(newval, extra);
  				*conf->variable = conf->reset_val = newval;
  				conf->gen.extra = conf->reset_extra = extra;
  				break;
  			}
  		case PGC_ENUM:
  			{
  				struct config_enum *conf = (struct config_enum *) gconf;
  				int			newval = conf->boot_val;
  				void	   *extra = NULL;
  
  				if (!call_enum_check_hook(conf, &newval, &extra,
  										  PGC_S_DEFAULT, LOG))
  					elog(FATAL, "failed to initialize %s to %d",
  						 conf->gen.name, newval);
  				if (conf->assign_hook)
  					conf->assign_hook(newval, extra);
  				*conf->variable = conf->reset_val = newval;
  				conf->gen.extra = conf->reset_extra = extra;
  				break;
  			}
  	}
  }
  
  
  /*
   * Select the configuration files and data directory to be used, and
   * do the initial read of postgresql.conf.
   *
   * This is called after processing command-line switches.
   *		userDoption is the -D switch value if any (NULL if unspecified).
   *		progname is just for use in error messages.
   *
   * Returns true on success; on failure, prints a suitable error message
   * to stderr and returns false.
   */
  bool
  SelectConfigFiles(const char *userDoption, const char *progname)
  {
  	char	   *configdir;
  	char	   *fname;
  	struct stat stat_buf;
  
  	/* configdir is -D option, or $PGDATA if no -D */
  	if (userDoption)
  		configdir = make_absolute_path(userDoption);
  	else
  		configdir = make_absolute_path(getenv("PGDATA"));
  
  	if (configdir && stat(configdir, &stat_buf) != 0)
  	{
  		write_stderr("%s: could not access directory \"%s\": %s\n",
  					 progname,
  					 configdir,
  					 strerror(errno));
  		if (errno == ENOENT)
  			write_stderr("Run initdb or pg_basebackup to initialize a PostgreSQL data directory.\n");
  		return false;
  	}
  
  	/*
  	 * Find the configuration file: if config_file was specified on the
  	 * command line, use it, else use configdir/postgresql.conf.  In any case
  	 * ensure the result is an absolute path, so that it will be interpreted
  	 * the same way by future backends.
  	 */
  	if (ConfigFileName)
  		fname = make_absolute_path(ConfigFileName);
  	else if (configdir)
  	{
  		fname = guc_malloc(FATAL,
  						   strlen(configdir) + strlen(CONFIG_FILENAME) + 2);
  		sprintf(fname, "%s/%s", configdir, CONFIG_FILENAME);
  	}
  	else
  	{
  		write_stderr("%s does not know where to find the server configuration file.\n"
  					 "You must specify the --config-file or -D invocation "
  					 "option or set the PGDATA environment variable.\n",
  					 progname);
  		return false;
  	}
  
  	/*
  	 * Set the ConfigFileName GUC variable to its final value, ensuring that
  	 * it can't be overridden later.
  	 */
  	SetConfigOption("config_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
  	free(fname);
  
  	/*
  	 * Now read the config file for the first time.
  	 */
  	if (stat(ConfigFileName, &stat_buf) != 0)
  	{
  		write_stderr("%s: could not access the server configuration file \"%s\": %s\n",
  					 progname, ConfigFileName, strerror(errno));
  		free(configdir);
  		return false;
  	}
  
  	/*
  	 * Read the configuration file for the first time.  This time only the
  	 * data_directory parameter is picked up to determine the data directory,
  	 * so that we can read the PG_AUTOCONF_FILENAME file next time.
  	 */
  	ProcessConfigFile(PGC_POSTMASTER);
  
  	/*
  	 * If the data_directory GUC variable has been set, use that as DataDir;
  	 * otherwise use configdir if set; else punt.
  	 *
  	 * Note: SetDataDir will copy and absolute-ize its argument, so we don't
  	 * have to.
  	 */
  	if (data_directory)
  		SetDataDir(data_directory);
  	else if (configdir)
  		SetDataDir(configdir);
  	else
  	{
  		write_stderr("%s does not know where to find the database system data.\n"
  					 "This can be specified as \"data_directory\" in \"%s\", "
  					 "or by the -D invocation option, or by the "
  					 "PGDATA environment variable.\n",
  					 progname, ConfigFileName);
  		return false;
  	}
  
  	/*
  	 * Reflect the final DataDir value back into the data_directory GUC var.
  	 * (If you are wondering why we don't just make them a single variable,
  	 * it's because the EXEC_BACKEND case needs DataDir to be transmitted to
  	 * child backends specially.  XXX is that still true?  Given that we now
  	 * chdir to DataDir, EXEC_BACKEND can read the config file without knowing
  	 * DataDir in advance.)
  	 */
  	SetConfigOption("data_directory", DataDir, PGC_POSTMASTER, PGC_S_OVERRIDE);
  
  	/*
  	 * Now read the config file a second time, allowing any settings in the
  	 * PG_AUTOCONF_FILENAME file to take effect.  (This is pretty ugly, but
  	 * since we have to determine the DataDir before we can find the autoconf
  	 * file, the alternatives seem worse.)
  	 */
  	ProcessConfigFile(PGC_POSTMASTER);
  
  	/*
  	 * If timezone_abbreviations wasn't set in the configuration file, install
  	 * the default value.  We do it this way because we can't safely install a
  	 * "real" value until my_exec_path is set, which may not have happened
  	 * when InitializeGUCOptions runs, so the bootstrap default value cannot
  	 * be the real desired default.
  	 */
  	pg_timezone_abbrev_initialize();
  
  	/*
  	 * Figure out where pg_hba.conf is, and make sure the path is absolute.
  	 */
  	if (HbaFileName)
  		fname = make_absolute_path(HbaFileName);
  	else if (configdir)
  	{
  		fname = guc_malloc(FATAL,
  						   strlen(configdir) + strlen(HBA_FILENAME) + 2);
  		sprintf(fname, "%s/%s", configdir, HBA_FILENAME);
  	}
  	else
  	{
  		write_stderr("%s does not know where to find the \"hba\" configuration file.\n"
  					 "This can be specified as \"hba_file\" in \"%s\", "
  					 "or by the -D invocation option, or by the "
  					 "PGDATA environment variable.\n",
  					 progname, ConfigFileName);
  		return false;
  	}
  	SetConfigOption("hba_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
  	free(fname);
  
  	/*
  	 * Likewise for pg_ident.conf.
  	 */
  	if (IdentFileName)
  		fname = make_absolute_path(IdentFileName);
  	else if (configdir)
  	{
  		fname = guc_malloc(FATAL,
  						   strlen(configdir) + strlen(IDENT_FILENAME) + 2);
  		sprintf(fname, "%s/%s", configdir, IDENT_FILENAME);
  	}
  	else
  	{
  		write_stderr("%s does not know where to find the \"ident\" configuration file.\n"
  					 "This can be specified as \"ident_file\" in \"%s\", "
  					 "or by the -D invocation option, or by the "
  					 "PGDATA environment variable.\n",
  					 progname, ConfigFileName);
  		return false;
  	}
  	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
  	free(fname);
  
  	free(configdir);
  
  	return true;
  }
  
  
  /*
   * Reset all options to their saved default values (implements RESET ALL)
   */
  void
  ResetAllOptions(void)
  {
  	int			i;
  
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *gconf = guc_variables[i];
  
  		/* Don't reset non-SET-able values */
  		if (gconf->context != PGC_SUSET &&
  			gconf->context != PGC_USERSET)
  			continue;
  		/* Don't reset if special exclusion from RESET ALL */
  		if (gconf->flags & GUC_NO_RESET_ALL)
  			continue;
  		/* No need to reset if wasn't SET */
  		if (gconf->source <= PGC_S_OVERRIDE)
  			continue;
  
  		/* Save old value to support transaction abort */
  		push_old_value(gconf, GUC_ACTION_SET);
  
  		switch (gconf->vartype)
  		{
  			case PGC_BOOL:
  				{
  					struct config_bool *conf = (struct config_bool *) gconf;
  
  					if (conf->assign_hook)
  						conf->assign_hook(conf->reset_val,
  										  conf->reset_extra);
  					*conf->variable = conf->reset_val;
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									conf->reset_extra);
  					break;
  				}
  			case PGC_INT:
  				{
  					struct config_int *conf = (struct config_int *) gconf;
  
  					if (conf->assign_hook)
  						conf->assign_hook(conf->reset_val,
  										  conf->reset_extra);
  					*conf->variable = conf->reset_val;
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									conf->reset_extra);
  					break;
  				}
  			case PGC_REAL:
  				{
  					struct config_real *conf = (struct config_real *) gconf;
  
  					if (conf->assign_hook)
  						conf->assign_hook(conf->reset_val,
  										  conf->reset_extra);
  					*conf->variable = conf->reset_val;
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									conf->reset_extra);
  					break;
  				}
  			case PGC_STRING:
  				{
  					struct config_string *conf = (struct config_string *) gconf;
  
  					if (conf->assign_hook)
  						conf->assign_hook(conf->reset_val,
  										  conf->reset_extra);
  					set_string_field(conf, conf->variable, conf->reset_val);
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									conf->reset_extra);
  					break;
  				}
  			case PGC_ENUM:
  				{
  					struct config_enum *conf = (struct config_enum *) gconf;
  
  					if (conf->assign_hook)
  						conf->assign_hook(conf->reset_val,
  										  conf->reset_extra);
  					*conf->variable = conf->reset_val;
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									conf->reset_extra);
  					break;
  				}
  		}
  
  		gconf->source = gconf->reset_source;
  		gconf->scontext = gconf->reset_scontext;
  
  		if (gconf->flags & GUC_REPORT)
  		{
  			gconf->status |= GUC_NEEDS_REPORT;
  			report_needed = true;
  		}
  	}
  }
  
  
  /*
   * push_old_value
   *		Push previous state during transactional assignment to a GUC variable.
   */
  static void
  push_old_value(struct config_generic *gconf, GucAction action)
  {
  	GucStack   *stack;
  
  	/* If we're not inside a nest level, do nothing */
  	if (GUCNestLevel == 0)
  		return;
  
  	/* Do we already have a stack entry of the current nest level? */
  	stack = gconf->stack;
  	if (stack && stack->nest_level >= GUCNestLevel)
  	{
  		/* Yes, so adjust its state if necessary */
  		Assert(stack->nest_level == GUCNestLevel);
  		switch (action)
  		{
  			case GUC_ACTION_SET:
  				/* SET overrides any prior action at same nest level */
  				if (stack->state == GUC_SET_LOCAL)
  				{
  					/* must discard old masked value */
  					discard_stack_value(gconf, &stack->masked);
  				}
  				stack->state = GUC_SET;
  				break;
  			case GUC_ACTION_LOCAL:
  				if (stack->state == GUC_SET)
  				{
  					/* SET followed by SET LOCAL, remember SET's value */
  					stack->masked_scontext = gconf->scontext;
  					set_stack_value(gconf, &stack->masked);
  					stack->state = GUC_SET_LOCAL;
  				}
  				/* in all other cases, no change to stack entry */
  				break;
  			case GUC_ACTION_SAVE:
  				/* Could only have a prior SAVE of same variable */
  				Assert(stack->state == GUC_SAVE);
  				break;
  		}
  		Assert(guc_dirty);		/* must be set already */
  		return;
  	}
  
  	/*
  	 * Push a new stack entry
  	 *
  	 * We keep all the stack entries in TopTransactionContext for simplicity.
  	 */
  	stack = (GucStack *) MemoryContextAllocZero(TopTransactionContext,
  												sizeof(GucStack));
  
  	stack->prev = gconf->stack;
  	stack->nest_level = GUCNestLevel;
  	switch (action)
  	{
  		case GUC_ACTION_SET:
  			stack->state = GUC_SET;
  			break;
  		case GUC_ACTION_LOCAL:
  			stack->state = GUC_LOCAL;
  			break;
  		case GUC_ACTION_SAVE:
  			stack->state = GUC_SAVE;
  			break;
  	}
  	stack->source = gconf->source;
  	stack->scontext = gconf->scontext;
  	set_stack_value(gconf, &stack->prior);
  
  	gconf->stack = stack;
  
  	/* Ensure we remember to pop at end of xact */
  	guc_dirty = true;
  }
  
  
  /*
   * Do GUC processing at main transaction start.
   */
  void
  AtStart_GUC(void)
  {
  	/*
  	 * The nest level should be 0 between transactions; if it isn't, somebody
  	 * didn't call AtEOXact_GUC, or called it with the wrong nestLevel.  We
  	 * throw a warning but make no other effort to clean up.
  	 */
  	if (GUCNestLevel != 0)
  		elog(WARNING, "GUC nest level = %d at transaction start",
  			 GUCNestLevel);
  	GUCNestLevel = 1;
  }
  
  /*
   * Enter a new nesting level for GUC values.  This is called at subtransaction
   * start, and when entering a function that has proconfig settings, and in
   * some other places where we want to set GUC variables transiently.
   * NOTE we must not risk error here, else subtransaction start will be unhappy.
   */
  int
  NewGUCNestLevel(void)
  {
  	return ++GUCNestLevel;
  }
  
  /*
   * Do GUC processing at transaction or subtransaction commit or abort, or
   * when exiting a function that has proconfig settings, or when undoing a
   * transient assignment to some GUC variables.  (The name is thus a bit of
   * a misnomer; perhaps it should be ExitGUCNestLevel or some such.)
   * During abort, we discard all GUC settings that were applied at nesting
   * levels >= nestLevel.  nestLevel == 1 corresponds to the main transaction.
   */
  void
  AtEOXact_GUC(bool isCommit, int nestLevel)
  {
  	bool		still_dirty;
  	int			i;
  
  	/*
  	 * Note: it's possible to get here with GUCNestLevel == nestLevel-1 during
  	 * abort, if there is a failure during transaction start before
  	 * AtStart_GUC is called.
  	 */
  	Assert(nestLevel > 0 &&
  		   (nestLevel <= GUCNestLevel ||
  			(nestLevel == GUCNestLevel + 1 && !isCommit)));
  
  	/* Quick exit if nothing's changed in this transaction */
  	if (!guc_dirty)
  	{
  		GUCNestLevel = nestLevel - 1;
  		return;
  	}
  
  	still_dirty = false;
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *gconf = guc_variables[i];
  		GucStack   *stack;
  
  		/*
  		 * Process and pop each stack entry within the nest level. To simplify
  		 * fmgr_security_definer() and other places that use GUC_ACTION_SAVE,
  		 * we allow failure exit from code that uses a local nest level to be
  		 * recovered at the surrounding transaction or subtransaction abort;
  		 * so there could be more than one stack entry to pop.
  		 */
  		while ((stack = gconf->stack) != NULL &&
  			   stack->nest_level >= nestLevel)
  		{
  			GucStack   *prev = stack->prev;
  			bool		restorePrior = false;
  			bool		restoreMasked = false;
  			bool		changed;
  
  			/*
  			 * In this next bit, if we don't set either restorePrior or
  			 * restoreMasked, we must "discard" any unwanted fields of the
  			 * stack entries to avoid leaking memory.  If we do set one of
  			 * those flags, unused fields will be cleaned up after restoring.
  			 */
  			if (!isCommit)		/* if abort, always restore prior value */
  				restorePrior = true;
  			else if (stack->state == GUC_SAVE)
  				restorePrior = true;
  			else if (stack->nest_level == 1)
  			{
  				/* transaction commit */
  				if (stack->state == GUC_SET_LOCAL)
  					restoreMasked = true;
  				else if (stack->state == GUC_SET)
  				{
  					/* we keep the current active value */
  					discard_stack_value(gconf, &stack->prior);
  				}
  				else			/* must be GUC_LOCAL */
  					restorePrior = true;
  			}
  			else if (prev == NULL ||
  					 prev->nest_level < stack->nest_level - 1)
  			{
  				/* decrement entry's level and do not pop it */
  				stack->nest_level--;
  				continue;
  			}
  			else
  			{
  				/*
  				 * We have to merge this stack entry into prev. See README for
  				 * discussion of this bit.
  				 */
  				switch (stack->state)
  				{
  					case GUC_SAVE:
  						Assert(false);	/* can't get here */
  						break;
  
  					case GUC_SET:
  						/* next level always becomes SET */
  						discard_stack_value(gconf, &stack->prior);
  						if (prev->state == GUC_SET_LOCAL)
  							discard_stack_value(gconf, &prev->masked);
  						prev->state = GUC_SET;
  						break;
  
  					case GUC_LOCAL:
  						if (prev->state == GUC_SET)
  						{
  							/* LOCAL migrates down */
  							prev->masked_scontext = stack->scontext;
  							prev->masked = stack->prior;
  							prev->state = GUC_SET_LOCAL;
  						}
  						else
  						{
  							/* else just forget this stack level */
  							discard_stack_value(gconf, &stack->prior);
  						}
  						break;
  
  					case GUC_SET_LOCAL:
  						/* prior state at this level no longer wanted */
  						discard_stack_value(gconf, &stack->prior);
  						/* copy down the masked state */
  						prev->masked_scontext = stack->masked_scontext;
  						if (prev->state == GUC_SET_LOCAL)
  							discard_stack_value(gconf, &prev->masked);
  						prev->masked = stack->masked;
  						prev->state = GUC_SET_LOCAL;
  						break;
  				}
  			}
  
  			changed = false;
  
  			if (restorePrior || restoreMasked)
  			{
  				/* Perform appropriate restoration of the stacked value */
  				config_var_value newvalue;
  				GucSource	newsource;
  				GucContext	newscontext;
  
  				if (restoreMasked)
  				{
  					newvalue = stack->masked;
  					newsource = PGC_S_SESSION;
  					newscontext = stack->masked_scontext;
  				}
  				else
  				{
  					newvalue = stack->prior;
  					newsource = stack->source;
  					newscontext = stack->scontext;
  				}
  
  				switch (gconf->vartype)
  				{
  					case PGC_BOOL:
  						{
  							struct config_bool *conf = (struct config_bool *) gconf;
  							bool		newval = newvalue.val.boolval;
  							void	   *newextra = newvalue.extra;
  
  							if (*conf->variable != newval ||
  								conf->gen.extra != newextra)
  							{
  								if (conf->assign_hook)
  									conf->assign_hook(newval, newextra);
  								*conf->variable = newval;
  								set_extra_field(&conf->gen, &conf->gen.extra,
  												newextra);
  								changed = true;
  							}
  							break;
  						}
  					case PGC_INT:
  						{
  							struct config_int *conf = (struct config_int *) gconf;
  							int			newval = newvalue.val.intval;
  							void	   *newextra = newvalue.extra;
  
  							if (*conf->variable != newval ||
  								conf->gen.extra != newextra)
  							{
  								if (conf->assign_hook)
  									conf->assign_hook(newval, newextra);
  								*conf->variable = newval;
  								set_extra_field(&conf->gen, &conf->gen.extra,
  												newextra);
  								changed = true;
  							}
  							break;
  						}
  					case PGC_REAL:
  						{
  							struct config_real *conf = (struct config_real *) gconf;
  							double		newval = newvalue.val.realval;
  							void	   *newextra = newvalue.extra;
  
  							if (*conf->variable != newval ||
  								conf->gen.extra != newextra)
  							{
  								if (conf->assign_hook)
  									conf->assign_hook(newval, newextra);
  								*conf->variable = newval;
  								set_extra_field(&conf->gen, &conf->gen.extra,
  												newextra);
  								changed = true;
  							}
  							break;
  						}
  					case PGC_STRING:
  						{
  							struct config_string *conf = (struct config_string *) gconf;
  							char	   *newval = newvalue.val.stringval;
  							void	   *newextra = newvalue.extra;
  
  							if (*conf->variable != newval ||
  								conf->gen.extra != newextra)
  							{
  								if (conf->assign_hook)
  									conf->assign_hook(newval, newextra);
  								set_string_field(conf, conf->variable, newval);
  								set_extra_field(&conf->gen, &conf->gen.extra,
  												newextra);
  								changed = true;
  							}
  
  							/*
  							 * Release stacked values if not used anymore. We
  							 * could use discard_stack_value() here, but since
  							 * we have type-specific code anyway, might as
  							 * well inline it.
  							 */
  							set_string_field(conf, &stack->prior.val.stringval, NULL);
  							set_string_field(conf, &stack->masked.val.stringval, NULL);
  							break;
  						}
  					case PGC_ENUM:
  						{
  							struct config_enum *conf = (struct config_enum *) gconf;
  							int			newval = newvalue.val.enumval;
  							void	   *newextra = newvalue.extra;
  
  							if (*conf->variable != newval ||
  								conf->gen.extra != newextra)
  							{
  								if (conf->assign_hook)
  									conf->assign_hook(newval, newextra);
  								*conf->variable = newval;
  								set_extra_field(&conf->gen, &conf->gen.extra,
  												newextra);
  								changed = true;
  							}
  							break;
  						}
  				}
  
  				/*
  				 * Release stacked extra values if not used anymore.
  				 */
  				set_extra_field(gconf, &(stack->prior.extra), NULL);
  				set_extra_field(gconf, &(stack->masked.extra), NULL);
  
  				/* And restore source information */
  				gconf->source = newsource;
  				gconf->scontext = newscontext;
  			}
  
  			/* Finish popping the state stack */
  			gconf->stack = prev;
  			pfree(stack);
  
  			/* Report new value if we changed it */
  			if (changed && (gconf->flags & GUC_REPORT))
  			{
  				gconf->status |= GUC_NEEDS_REPORT;
  				report_needed = true;
  			}
  		}						/* end of stack-popping loop */
  
  		if (stack != NULL)
  			still_dirty = true;
  	}
  
  	/* If there are no remaining stack entries, we can reset guc_dirty */
  	guc_dirty = still_dirty;
  
  	/* Update nesting level */
  	GUCNestLevel = nestLevel - 1;
  }
  
  
  /*
   * Start up automatic reporting of changes to variables marked GUC_REPORT.
   * This is executed at completion of backend startup.
   */
  void
  BeginReportingGUCOptions(void)
  {
  	int			i;
  
  	/*
  	 * Don't do anything unless talking to an interactive frontend.
  	 */
  	if (whereToSendOutput != DestRemote)
  		return;
  
  	reporting_enabled = true;
  
  	/*
  	 * Hack for in_hot_standby: initialize with the value we're about to send.
  	 * (This could be out of date by the time we actually send it, in which
  	 * case the next ReportChangedGUCOptions call will send a duplicate
  	 * report.)
  	 */
  	in_hot_standby = RecoveryInProgress();
  
  	/* Transmit initial values of interesting variables */
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *conf = guc_variables[i];
  
  		if (conf->flags & GUC_REPORT)
  			ReportGUCOption(conf);
  	}
  
  	report_needed = false;
  }
  
  /*
   * ReportChangedGUCOptions: report recently-changed GUC_REPORT variables
   *
   * This is called just before we wait for a new client query.
   *
   * By handling things this way, we ensure that a ParameterStatus message
   * is sent at most once per variable per query, even if the variable
   * changed multiple times within the query.  That's quite possible when
   * using features such as function SET clauses.  Function SET clauses
   * also tend to cause values to change intraquery but eventually revert
   * to their prevailing values; ReportGUCOption is responsible for avoiding
   * redundant reports in such cases.
   */
  void
  ReportChangedGUCOptions(void)
  {
  	/* Quick exit if not (yet) enabled */
  	if (!reporting_enabled)
  		return;
  
  	/*
  	 * Since in_hot_standby isn't actually changed by normal GUC actions, we
  	 * need a hack to check whether a new value needs to be reported to the
  	 * client.  For speed, we rely on the assumption that it can never
  	 * transition from false to true.
  	 */
  	if (in_hot_standby && !RecoveryInProgress())
  	{
  		struct config_generic *record;
  
  		record = find_option("in_hot_standby", false, false, ERROR);
  		Assert(record != NULL);
  		record->status |= GUC_NEEDS_REPORT;
  		report_needed = true;
  		in_hot_standby = false;
  	}
  
  	/* Quick exit if no values have been changed */
  	if (!report_needed)
  		return;
  
  	/* Transmit new values of interesting variables */
  	for (int i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *conf = guc_variables[i];
  
  		if ((conf->flags & GUC_REPORT) && (conf->status & GUC_NEEDS_REPORT))
  			ReportGUCOption(conf);
  	}
  
  	report_needed = false;
  }
  
  /*
   * ReportGUCOption: if appropriate, transmit option value to frontend
   *
   * We need not transmit the value if it's the same as what we last
   * transmitted.  However, clear the NEEDS_REPORT flag in any case.
   */
  static void
  ReportGUCOption(struct config_generic *record)
  {
  	char	   *val = _ShowOption(record, false);
  
  	if (record->last_reported == NULL ||
  		strcmp(val, record->last_reported) != 0)
  	{
  		StringInfoData msgbuf;
  
  		pq_beginmessage(&msgbuf, 'S');
  		pq_sendstring(&msgbuf, record->name);
  		pq_sendstring(&msgbuf, val);
  		pq_endmessage(&msgbuf);
  
  		/*
  		 * We need a long-lifespan copy.  If strdup() fails due to OOM, we'll
  		 * set last_reported to NULL and thereby possibly make a duplicate
  		 * report later.
  		 */
  		if (record->last_reported)
  			free(record->last_reported);
  		record->last_reported = strdup(val);
  	}
  
  	pfree(val);
  
  	record->status &= ~GUC_NEEDS_REPORT;
  }
  
  /*
   * Convert a value from one of the human-friendly units ("kB", "min" etc.)
   * to the given base unit.  'value' and 'unit' are the input value and unit
   * to convert from (there can be trailing spaces in the unit string).
   * The converted value is stored in *base_value.
   * It's caller's responsibility to round off the converted value as necessary
   * and check for out-of-range.
   *
   * Returns true on success, false if the input unit is not recognized.
   */
  static bool
  convert_to_base_unit(double value, const char *unit,
  					 int base_unit, double *base_value)
  {
  	char		unitstr[MAX_UNIT_LEN + 1];
  	int			unitlen;
  	const unit_conversion *table;
  	int			i;
  
  	/* extract unit string to compare to table entries */
  	unitlen = 0;
  	while (*unit != '\0' && !isspace((unsigned char) *unit) &&
  		   unitlen < MAX_UNIT_LEN)
  		unitstr[unitlen++] = *(unit++);
  	unitstr[unitlen] = '\0';
  	/* allow whitespace after unit */
  	while (isspace((unsigned char) *unit))
  		unit++;
  	if (*unit != '\0')
  		return false;			/* unit too long, or garbage after it */
  
  	/* now search the appropriate table */
  	if (base_unit & GUC_UNIT_MEMORY)
  		table = memory_unit_conversion_table;
  	else
  		table = time_unit_conversion_table;
  
  	for (i = 0; *table[i].unit; i++)
  	{
  		if (base_unit == table[i].base_unit &&
  			strcmp(unitstr, table[i].unit) == 0)
  		{
  			double		cvalue = value * table[i].multiplier;
  
  			/*
  			 * If the user gave a fractional value such as "30.1GB", round it
  			 * off to the nearest multiple of the next smaller unit, if there
  			 * is one.
  			 */
  			if (*table[i + 1].unit &&
  				base_unit == table[i + 1].base_unit)
  				cvalue = rint(cvalue / table[i + 1].multiplier) *
  					table[i + 1].multiplier;
  
  			*base_value = cvalue;
  			return true;
  		}
  	}
  	return false;
  }
  
  /*
   * Convert an integer value in some base unit to a human-friendly unit.
   *
   * The output unit is chosen so that it's the greatest unit that can represent
   * the value without loss.  For example, if the base unit is GUC_UNIT_KB, 1024
   * is converted to 1 MB, but 1025 is represented as 1025 kB.
   */
  static void
  convert_int_from_base_unit(int64 base_value, int base_unit,
  						   int64 *value, const char **unit)
  {
  	const unit_conversion *table;
  	int			i;
  
  	*unit = NULL;
  
  	if (base_unit & GUC_UNIT_MEMORY)
  		table = memory_unit_conversion_table;
  	else
  		table = time_unit_conversion_table;
  
  	for (i = 0; *table[i].unit; i++)
  	{
  		if (base_unit == table[i].base_unit)
  		{
  			/*
  			 * Accept the first conversion that divides the value evenly.  We
  			 * assume that the conversions for each base unit are ordered from
  			 * greatest unit to the smallest!
  			 */
  			if (table[i].multiplier <= 1.0 ||
  				base_value % (int64) table[i].multiplier == 0)
  			{
  				*value = (int64) rint(base_value / table[i].multiplier);
  				*unit = table[i].unit;
  				break;
  			}
  		}
  	}
  
  	Assert(*unit != NULL);
  }
  
  /*
   * Convert a floating-point value in some base unit to a human-friendly unit.
   *
   * Same as above, except we have to do the math a bit differently, and
   * there's a possibility that we don't find any exact divisor.
   */
  static void
  convert_real_from_base_unit(double base_value, int base_unit,
  							double *value, const char **unit)
  {
  	const unit_conversion *table;
  	int			i;
  
  	*unit = NULL;
  
  	if (base_unit & GUC_UNIT_MEMORY)
  		table = memory_unit_conversion_table;
  	else
  		table = time_unit_conversion_table;
  
  	for (i = 0; *table[i].unit; i++)
  	{
  		if (base_unit == table[i].base_unit)
  		{
  			/*
  			 * Accept the first conversion that divides the value evenly; or
  			 * if there is none, use the smallest (last) target unit.
  			 *
  			 * What we actually care about here is whether snprintf with "%g"
  			 * will print the value as an integer, so the obvious test of
  			 * "*value == rint(*value)" is too strict; roundoff error might
  			 * make us choose an unreasonably small unit.  As a compromise,
  			 * accept a divisor that is within 1e-8 of producing an integer.
  			 */
  			*value = base_value / table[i].multiplier;
  			*unit = table[i].unit;
  			if (*value > 0 &&
  				fabs((rint(*value) / *value) - 1.0) <= 1e-8)
  				break;
  		}
  	}
  
  	Assert(*unit != NULL);
  }
  
  /*
   * Return the name of a GUC's base unit (e.g. "ms") given its flags.
   * Return NULL if the GUC is unitless.
   */
  static const char *
  get_config_unit_name(int flags)
  {
  	switch (flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME))
  	{
  		case 0:
  			return NULL;		/* GUC has no units */
  		case GUC_UNIT_BYTE:
  			return "B";
  		case GUC_UNIT_KB:
  			return "kB";
  		case GUC_UNIT_MB:
  			return "MB";
  		case GUC_UNIT_BLOCKS:
  			{
  				static char bbuf[8];
  
  				/* initialize if first time through */
  				if (bbuf[0] == '\0')
  					snprintf(bbuf, sizeof(bbuf), "%dkB", BLCKSZ / 1024);
  				return bbuf;
  			}
  		case GUC_UNIT_XBLOCKS:
  			{
  				static char xbuf[8];
  
  				/* initialize if first time through */
  				if (xbuf[0] == '\0')
  					snprintf(xbuf, sizeof(xbuf), "%dkB", XLOG_BLCKSZ / 1024);
  				return xbuf;
  			}
  		case GUC_UNIT_MS:
  			return "ms";
  		case GUC_UNIT_S:
  			return "s";
  		case GUC_UNIT_MIN:
  			return "min";
  		default:
  			elog(ERROR, "unrecognized GUC units value: %d",
  				 flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME));
  			return NULL;
  	}
  }
  
  
  /*
   * Try to parse value as an integer.  The accepted formats are the
   * usual decimal, octal, or hexadecimal formats, as well as floating-point
   * formats (which will be rounded to integer after any units conversion).
   * Optionally, the value can be followed by a unit name if "flags" indicates
   * a unit is allowed.
   *
   * If the string parses okay, return true, else false.
   * If okay and result is not NULL, return the value in *result.
   * If not okay and hintmsg is not NULL, *hintmsg is set to a suitable
   * HINT message, or NULL if no hint provided.
   */
  bool
  parse_int(const char *value, int *result, int flags, const char **hintmsg)
  {
  	/*
  	 * We assume here that double is wide enough to represent any integer
  	 * value with adequate precision.
  	 */
  	double		val;
  	char	   *endptr;
  
  	/* To suppress compiler warnings, always set output params */
  	if (result)
  		*result = 0;
  	if (hintmsg)
  		*hintmsg = NULL;
  
  	/*
  	 * Try to parse as an integer (allowing octal or hex input).  If the
  	 * conversion stops at a decimal point or 'e', or overflows, re-parse as
  	 * float.  This should work fine as long as we have no unit names starting
  	 * with 'e'.  If we ever do, the test could be extended to check for a
  	 * sign or digit after 'e', but for now that's unnecessary.
  	 */
  	errno = 0;
  	val = strtol(value, &endptr, 0);
  	if (*endptr == '.' || *endptr == 'e' || *endptr == 'E' ||
  		errno == ERANGE)
  	{
  		errno = 0;
  		val = strtod(value, &endptr);
  	}
  
  	if (endptr == value || errno == ERANGE)
  		return false;			/* no HINT for these cases */
  
  	/* reject NaN (infinities will fail range check below) */
  	if (isnan(val))
  		return false;			/* treat same as syntax error; no HINT */
  
  	/* allow whitespace between number and unit */
  	while (isspace((unsigned char) *endptr))
  		endptr++;
  
  	/* Handle possible unit */
  	if (*endptr != '\0')
  	{
  		if ((flags & GUC_UNIT) == 0)
  			return false;		/* this setting does not accept a unit */
  
  		if (!convert_to_base_unit(val,
  								  endptr, (flags & GUC_UNIT),
  								  &val))
  		{
  			/* invalid unit, or garbage after the unit; set hint and fail. */
  			if (hintmsg)
  			{
  				if (flags & GUC_UNIT_MEMORY)
  					*hintmsg = memory_units_hint;
  				else
  					*hintmsg = time_units_hint;
  			}
  			return false;
  		}
  	}
  
  	/* Round to int, then check for overflow */
  	val = rint(val);
  
  	if (val > INT_MAX || val < INT_MIN)
  	{
  		if (hintmsg)
  			*hintmsg = gettext_noop("Value exceeds integer range.");
  		return false;
  	}
  
  	if (result)
  		*result = (int) val;
  	return true;
  }
  
  /*
   * Try to parse value as a floating point number in the usual format.
   * Optionally, the value can be followed by a unit name if "flags" indicates
   * a unit is allowed.
   *
   * If the string parses okay, return true, else false.
   * If okay and result is not NULL, return the value in *result.
   * If not okay and hintmsg is not NULL, *hintmsg is set to a suitable
   * HINT message, or NULL if no hint provided.
   */
  bool
  parse_real(const char *value, double *result, int flags, const char **hintmsg)
  {
  	double		val;
  	char	   *endptr;
  
  	/* To suppress compiler warnings, always set output params */
  	if (result)
  		*result = 0;
  	if (hintmsg)
  		*hintmsg = NULL;
  
  	errno = 0;
  	val = strtod(value, &endptr);
  
  	if (endptr == value || errno == ERANGE)
  		return false;			/* no HINT for these cases */
  
  	/* reject NaN (infinities will fail range checks later) */
  	if (isnan(val))
  		return false;			/* treat same as syntax error; no HINT */
  
  	/* allow whitespace between number and unit */
  	while (isspace((unsigned char) *endptr))
  		endptr++;
  
  	/* Handle possible unit */
  	if (*endptr != '\0')
  	{
  		if ((flags & GUC_UNIT) == 0)
  			return false;		/* this setting does not accept a unit */
  
  		if (!convert_to_base_unit(val,
  								  endptr, (flags & GUC_UNIT),
  								  &val))
  		{
  			/* invalid unit, or garbage after the unit; set hint and fail. */
  			if (hintmsg)
  			{
  				if (flags & GUC_UNIT_MEMORY)
  					*hintmsg = memory_units_hint;
  				else
  					*hintmsg = time_units_hint;
  			}
  			return false;
  		}
  	}
  
  	if (result)
  		*result = val;
  	return true;
  }
  
  
  /*
   * Lookup the name for an enum option with the selected value.
   * Should only ever be called with known-valid values, so throws
   * an elog(ERROR) if the enum option is not found.
   *
   * The returned string is a pointer to static data and not
   * allocated for modification.
   */
  const char *
  config_enum_lookup_by_value(struct config_enum *record, int val)
  {
  	const struct config_enum_entry *entry;
  
  	for (entry = record->options; entry && entry->name; entry++)
  	{
  		if (entry->val == val)
  			return entry->name;
  	}
  
  	elog(ERROR, "could not find enum option %d for %s",
  		 val, record->gen.name);
  	return NULL;				/* silence compiler */
  }
  
  
  /*
   * Lookup the value for an enum option with the selected name
   * (case-insensitive).
   * If the enum option is found, sets the retval value and returns
   * true. If it's not found, return false and retval is set to 0.
   */
  bool
  config_enum_lookup_by_name(struct config_enum *record, const char *value,
  						   int *retval)
  {
  	const struct config_enum_entry *entry;
  
  	for (entry = record->options; entry && entry->name; entry++)
  	{
  		if (pg_strcasecmp(value, entry->name) == 0)
  		{
  			*retval = entry->val;
  			return true;
  		}
  	}
  
  	*retval = 0;
  	return false;
  }
  
  
  /*
   * Return a list of all available options for an enum, excluding
   * hidden ones, separated by the given separator.
   * If prefix is non-NULL, it is added before the first enum value.
   * If suffix is non-NULL, it is added to the end of the string.
   */
  static char *
  config_enum_get_options(struct config_enum *record, const char *prefix,
  						const char *suffix, const char *separator)
  {
  	const struct config_enum_entry *entry;
  	StringInfoData retstr;
  	int			seplen;
  
  	initStringInfo(&retstr);
  	appendStringInfoString(&retstr, prefix);
  
  	seplen = strlen(separator);
  	for (entry = record->options; entry && entry->name; entry++)
  	{
  		if (!entry->hidden)
  		{
  			appendStringInfoString(&retstr, entry->name);
  			appendBinaryStringInfo(&retstr, separator, seplen);
  		}
  	}
  
  	/*
  	 * All the entries may have been hidden, leaving the string empty if no
  	 * prefix was given. This indicates a broken GUC setup, since there is no
  	 * use for an enum without any values, so we just check to make sure we
  	 * don't write to invalid memory instead of actually trying to do
  	 * something smart with it.
  	 */
  	if (retstr.len >= seplen)
  	{
  		/* Replace final separator */
  		retstr.data[retstr.len - seplen] = '\0';
  		retstr.len -= seplen;
  	}
  
  	appendStringInfoString(&retstr, suffix);
  
  	return retstr.data;
  }
  
  /*
   * Parse and validate a proposed value for the specified configuration
   * parameter.
   *
   * This does built-in checks (such as range limits for an integer parameter)
   * and also calls any check hook the parameter may have.
   *
   * record: GUC variable's info record
   * name: variable name (should match the record of course)
   * value: proposed value, as a string
   * source: identifies source of value (check hooks may need this)
   * elevel: level to log any error reports at
   * newval: on success, converted parameter value is returned here
   * newextra: on success, receives any "extra" data returned by check hook
   *	(caller must initialize *newextra to NULL)
   *
   * Returns true if OK, false if not (or throws error, if elevel >= ERROR)
   */
  static bool
  parse_and_validate_value(struct config_generic *record,
  						 const char *name, const char *value,
  						 GucSource source, int elevel,
  						 union config_var_val *newval, void **newextra)
  {
  	switch (record->vartype)
  	{
  		case PGC_BOOL:
  			{
  				struct config_bool *conf = (struct config_bool *) record;
  
  				if (!parse_bool(value, &newval->boolval))
  				{
  					ereport(elevel,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("parameter \"%s\" requires a Boolean value",
  									name)));
  					return false;
  				}
  
  				if (!call_bool_check_hook(conf, &newval->boolval, newextra,
  										  source, elevel))
  					return false;
  			}
  			break;
  		case PGC_INT:
  			{
  				struct config_int *conf = (struct config_int *) record;
  				const char *hintmsg;
  
  				if (!parse_int(value, &newval->intval,
  							   conf->gen.flags, &hintmsg))
  				{
  					ereport(elevel,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("invalid value for parameter \"%s\": \"%s\"",
  									name, value),
  							 hintmsg ? errhint("%s", _(hintmsg)) : 0));
  					return false;
  				}
  
  				if (newval->intval < conf->min || newval->intval > conf->max)
  				{
  					const char *unit = get_config_unit_name(conf->gen.flags);
  
  					ereport(elevel,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("%d%s%s is outside the valid range for parameter \"%s\" (%d .. %d)",
  									newval->intval,
  									unit ? " " : "",
  									unit ? unit : "",
  									name,
  									conf->min, conf->max)));
  					return false;
  				}
  
  				if (!call_int_check_hook(conf, &newval->intval, newextra,
  										 source, elevel))
  					return false;
  			}
  			break;
  		case PGC_REAL:
  			{
  				struct config_real *conf = (struct config_real *) record;
  				const char *hintmsg;
  
  				if (!parse_real(value, &newval->realval,
  								conf->gen.flags, &hintmsg))
  				{
  					ereport(elevel,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("invalid value for parameter \"%s\": \"%s\"",
  									name, value),
  							 hintmsg ? errhint("%s", _(hintmsg)) : 0));
  					return false;
  				}
  
  				if (newval->realval < conf->min || newval->realval > conf->max)
  				{
  					const char *unit = get_config_unit_name(conf->gen.flags);
  
  					ereport(elevel,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("%g%s%s is outside the valid range for parameter \"%s\" (%g .. %g)",
  									newval->realval,
  									unit ? " " : "",
  									unit ? unit : "",
  									name,
  									conf->min, conf->max)));
  					return false;
  				}
  
  				if (!call_real_check_hook(conf, &newval->realval, newextra,
  										  source, elevel))
  					return false;
  			}
  			break;
  		case PGC_STRING:
  			{
  				struct config_string *conf = (struct config_string *) record;
  
  				/*
  				 * The value passed by the caller could be transient, so we
  				 * always strdup it.
  				 */
  				newval->stringval = guc_strdup(elevel, value);
  				if (newval->stringval == NULL)
  					return false;
  
  				/*
  				 * The only built-in "parsing" check we have is to apply
  				 * truncation if GUC_IS_NAME.
  				 */
  				if (conf->gen.flags & GUC_IS_NAME)
  					truncate_identifier(newval->stringval,
  										strlen(newval->stringval),
  										true);
  
  				if (!call_string_check_hook(conf, &newval->stringval, newextra,
  											source, elevel))
  				{
  					free(newval->stringval);
  					newval->stringval = NULL;
  					return false;
  				}
  			}
  			break;
  		case PGC_ENUM:
  			{
  				struct config_enum *conf = (struct config_enum *) record;
  
  				if (!config_enum_lookup_by_name(conf, value, &newval->enumval))
  				{
  					char	   *hintmsg;
  
  					hintmsg = config_enum_get_options(conf,
  													  "Available values: ",
  													  ".", ", ");
  
  					ereport(elevel,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("invalid value for parameter \"%s\": \"%s\"",
  									name, value),
  							 hintmsg ? errhint("%s", _(hintmsg)) : 0));
  
  					if (hintmsg)
  						pfree(hintmsg);
  					return false;
  				}
  
  				if (!call_enum_check_hook(conf, &newval->enumval, newextra,
  										  source, elevel))
  					return false;
  			}
  			break;
  	}
  
  	return true;
  }
  
  
  /*
   * Sets option `name' to given value.
   *
   * The value should be a string, which will be parsed and converted to
   * the appropriate data type.  The context and source parameters indicate
   * in which context this function is being called, so that it can apply the
   * access restrictions properly.
   *
   * If value is NULL, set the option to its default value (normally the
   * reset_val, but if source == PGC_S_DEFAULT we instead use the boot_val).
   *
   * action indicates whether to set the value globally in the session, locally
   * to the current top transaction, or just for the duration of a function call.
   *
   * If changeVal is false then don't really set the option but do all
   * the checks to see if it would work.
   *
   * elevel should normally be passed as zero, allowing this function to make
   * its standard choice of ereport level.  However some callers need to be
   * able to override that choice; they should pass the ereport level to use.
   *
   * is_reload should be true only when called from read_nondefault_variables()
   * or RestoreGUCState(), where we are trying to load some other process's
   * GUC settings into a new process.
   *
   * Return value:
   *	+1: the value is valid and was successfully applied.
   *	0:	the name or value is invalid (but see below).
   *	-1: the value was not applied because of context, priority, or changeVal.
   *
   * If there is an error (non-existing option, invalid value) then an
   * ereport(ERROR) is thrown *unless* this is called for a source for which
   * we don't want an ERROR (currently, those are defaults, the config file,
   * and per-database or per-user settings, as well as callers who specify
   * a less-than-ERROR elevel).  In those cases we write a suitable error
   * message via ereport() and return 0.
   *
   * See also SetConfigOption for an external interface.
   */
  int
  set_config_option(const char *name, const char *value,
  				  GucContext context, GucSource source,
  				  GucAction action, bool changeVal, int elevel,
  				  bool is_reload)
  {
  	struct config_generic *record;
  	union config_var_val newval_union;
  	void	   *newextra = NULL;
  	bool		prohibitValueChange = false;
  	bool		makeDefault;
  
  	if (elevel == 0)
  	{
  		if (source == PGC_S_DEFAULT || source == PGC_S_FILE)
  		{
  			/*
  			 * To avoid cluttering the log, only the postmaster bleats loudly
  			 * about problems with the config file.
  			 */
  			elevel = IsUnderPostmaster ? DEBUG3 : LOG;
  		}
  		else if (source == PGC_S_GLOBAL ||
  				 source == PGC_S_DATABASE ||
  				 source == PGC_S_USER ||
  				 source == PGC_S_DATABASE_USER)
  			elevel = WARNING;
  		else
  			elevel = ERROR;
  	}
  
  	/*
  	 * GUC_ACTION_SAVE changes are acceptable during a parallel operation,
  	 * because the current worker will also pop the change.  We're probably
  	 * dealing with a function having a proconfig entry.  Only the function's
  	 * body should observe the change, and peer workers do not share in the
  	 * execution of a function call started by this worker.
  	 *
  	 * Other changes might need to affect other workers, so forbid them.
  	 */
  	if (IsInParallelMode() && changeVal && action != GUC_ACTION_SAVE)
  		ereport(elevel,
  				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
  				 errmsg("cannot set parameters during a parallel operation")));
  
  	record = find_option(name, true, false, elevel);
  	if (record == NULL)
  		return 0;
  
  	/*
  	 * Check if the option can be set at this time. See guc.h for the precise
  	 * rules.
  	 */
  	switch (record->context)
  	{
  		case PGC_INTERNAL:
  			if (context != PGC_INTERNAL)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed",
  								name)));
  				return 0;
  			}
  			break;
  		case PGC_POSTMASTER:
  			if (context == PGC_SIGHUP)
  			{
  				/*
  				 * We are re-reading a PGC_POSTMASTER variable from
  				 * postgresql.conf.  We can't change the setting, so we should
  				 * give a warning if the DBA tries to change it.  However,
  				 * because of variant formats, canonicalization by check
  				 * hooks, etc, we can't just compare the given string directly
  				 * to what's stored.  Set a flag to check below after we have
  				 * the final storable value.
  				 */
  				prohibitValueChange = true;
  			}
  			else if (context != PGC_POSTMASTER)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed without restarting the server",
  								name)));
  				return 0;
  			}
  			break;
  		case PGC_SIGHUP:
  			if (context != PGC_SIGHUP && context != PGC_POSTMASTER)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed now",
  								name)));
  				return 0;
  			}
  
  			/*
  			 * Hmm, the idea of the SIGHUP context is "ought to be global, but
  			 * can be changed after postmaster start". But there's nothing
  			 * that prevents a crafty administrator from sending SIGHUP
  			 * signals to individual backends only.
  			 */
  			break;
  		case PGC_SU_BACKEND:
  			/* Reject if we're connecting but user is not superuser */
  			if (context == PGC_BACKEND)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  						 errmsg("permission denied to set parameter \"%s\"",
  								name)));
  				return 0;
  			}
  			/* fall through to process the same as PGC_BACKEND */
  			/* FALLTHROUGH */
  		case PGC_BACKEND:
  			if (context == PGC_SIGHUP)
  			{
  				/*
  				 * If a PGC_BACKEND or PGC_SU_BACKEND parameter is changed in
  				 * the config file, we want to accept the new value in the
  				 * postmaster (whence it will propagate to
  				 * subsequently-started backends), but ignore it in existing
  				 * backends.  This is a tad klugy, but necessary because we
  				 * don't re-read the config file during backend start.
  				 *
  				 * In EXEC_BACKEND builds, this works differently: we load all
  				 * non-default settings from the CONFIG_EXEC_PARAMS file
  				 * during backend start.  In that case we must accept
  				 * PGC_SIGHUP settings, so as to have the same value as if
  				 * we'd forked from the postmaster.  This can also happen when
  				 * using RestoreGUCState() within a background worker that
  				 * needs to have the same settings as the user backend that
  				 * started it. is_reload will be true when either situation
  				 * applies.
  				 */
  				if (IsUnderPostmaster && !is_reload)
  					return -1;
  			}
  			else if (context != PGC_POSTMASTER &&
  					 context != PGC_BACKEND &&
  					 context != PGC_SU_BACKEND &&
  					 source != PGC_S_CLIENT)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be set after connection start",
  								name)));
  				return 0;
  			}
  			break;
  		case PGC_SUSET:
  			if (context == PGC_USERSET || context == PGC_BACKEND)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  						 errmsg("permission denied to set parameter \"%s\"",
  								name)));
  				return 0;
  			}
  			break;
  		case PGC_USERSET:
  			/* always okay */
  			break;
  	}
  
  	/*
  	 * Disallow changing GUC_NOT_WHILE_SEC_REST values if we are inside a
  	 * security restriction context.  We can reject this regardless of the GUC
  	 * context or source, mainly because sources that it might be reasonable
  	 * to override for won't be seen while inside a function.
  	 *
  	 * Note: variables marked GUC_NOT_WHILE_SEC_REST should usually be marked
  	 * GUC_NO_RESET_ALL as well, because ResetAllOptions() doesn't check this.
  	 * An exception might be made if the reset value is assumed to be "safe".
  	 *
  	 * Note: this flag is currently used for "session_authorization" and
  	 * "role".  We need to prohibit changing these inside a local userid
  	 * context because when we exit it, GUC won't be notified, leaving things
  	 * out of sync.  (This could be fixed by forcing a new GUC nesting level,
  	 * but that would change behavior in possibly-undesirable ways.)  Also, we
  	 * prohibit changing these in a security-restricted operation because
  	 * otherwise RESET could be used to regain the session user's privileges.
  	 */
  	if (record->flags & GUC_NOT_WHILE_SEC_REST)
  	{
  		if (InLocalUserIdChange())
  		{
  			/*
  			 * Phrasing of this error message is historical, but it's the most
  			 * common case.
  			 */
  			ereport(elevel,
  					(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  					 errmsg("cannot set parameter \"%s\" within security-definer function",
  							name)));
  			return 0;
  		}
  		if (InSecurityRestrictedOperation())
  		{
  			ereport(elevel,
  					(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  					 errmsg("cannot set parameter \"%s\" within security-restricted operation",
  							name)));
  			return 0;
  		}
  	}
  
  	/*
  	 * Should we set reset/stacked values?	(If so, the behavior is not
  	 * transactional.)	This is done either when we get a default value from
  	 * the database's/user's/client's default settings or when we reset a
  	 * value to its default.
  	 */
  	makeDefault = changeVal && (source <= PGC_S_OVERRIDE) &&
  		((value != NULL) || source == PGC_S_DEFAULT);
  
  	/*
  	 * Ignore attempted set if overridden by previously processed setting.
  	 * However, if changeVal is false then plow ahead anyway since we are
  	 * trying to find out if the value is potentially good, not actually use
  	 * it. Also keep going if makeDefault is true, since we may want to set
  	 * the reset/stacked values even if we can't set the variable itself.
  	 */
  	if (record->source > source)
  	{
  		if (changeVal && !makeDefault)
  		{
  			elog(DEBUG3, "\"%s\": setting ignored because previous source is higher priority",
  				 name);
  			return -1;
  		}
  		changeVal = false;
  	}
  
  	/*
  	 * Evaluate value and set variable.
  	 */
  	switch (record->vartype)
  	{
  		case PGC_BOOL:
  			{
  				struct config_bool *conf = (struct config_bool *) record;
  
  #define newval (newval_union.boolval)
  
  				if (value)
  				{
  					if (!parse_and_validate_value(record, name, value,
  												  source, elevel,
  												  &newval_union, &newextra))
  						return 0;
  				}
  				else if (source == PGC_S_DEFAULT)
  				{
  					newval = conf->boot_val;
  					if (!call_bool_check_hook(conf, &newval, &newextra,
  											  source, elevel))
  						return 0;
  				}
  				else
  				{
  					newval = conf->reset_val;
  					newextra = conf->reset_extra;
  					source = conf->gen.reset_source;
  					context = conf->gen.reset_scontext;
  				}
  
  				if (prohibitValueChange)
  				{
  					/* Release newextra, unless it's reset_extra */
  					if (newextra && !extra_field_used(&conf->gen, newextra))
  						free(newextra);
  
  					if (*conf->variable != newval)
  					{
  						record->status |= GUC_PENDING_RESTART;
  						ereport(elevel,
  								(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  								 errmsg("parameter \"%s\" cannot be changed without restarting the server",
  										name)));
  						return 0;
  					}
  					record->status &= ~GUC_PENDING_RESTART;
  					return -1;
  				}
  
  				if (changeVal)
  				{
  					/* Save old value to support transaction abort */
  					if (!makeDefault)
  						push_old_value(&conf->gen, action);
  
  					if (conf->assign_hook)
  						conf->assign_hook(newval, newextra);
  					*conf->variable = newval;
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									newextra);
  					conf->gen.source = source;
  					conf->gen.scontext = context;
  				}
  				if (makeDefault)
  				{
  					GucStack   *stack;
  
  					if (conf->gen.reset_source <= source)
  					{
  						conf->reset_val = newval;
  						set_extra_field(&conf->gen, &conf->reset_extra,
  										newextra);
  						conf->gen.reset_source = source;
  						conf->gen.reset_scontext = context;
  					}
  					for (stack = conf->gen.stack; stack; stack = stack->prev)
  					{
  						if (stack->source <= source)
  						{
  							stack->prior.val.boolval = newval;
  							set_extra_field(&conf->gen, &stack->prior.extra,
  											newextra);
  							stack->source = source;
  							stack->scontext = context;
  						}
  					}
  				}
  
  				/* Perhaps we didn't install newextra anywhere */
  				if (newextra && !extra_field_used(&conf->gen, newextra))
  					free(newextra);
  				break;
  
  #undef newval
  			}
  
  		case PGC_INT:
  			{
  				struct config_int *conf = (struct config_int *) record;
  
  #define newval (newval_union.intval)
  
  				if (value)
  				{
  					if (!parse_and_validate_value(record, name, value,
  												  source, elevel,
  												  &newval_union, &newextra))
  						return 0;
  				}
  				else if (source == PGC_S_DEFAULT)
  				{
  					newval = conf->boot_val;
  					if (!call_int_check_hook(conf, &newval, &newextra,
  											 source, elevel))
  						return 0;
  				}
  				else
  				{
  					newval = conf->reset_val;
  					newextra = conf->reset_extra;
  					source = conf->gen.reset_source;
  					context = conf->gen.reset_scontext;
  				}
  
  				if (prohibitValueChange)
  				{
  					/* Release newextra, unless it's reset_extra */
  					if (newextra && !extra_field_used(&conf->gen, newextra))
  						free(newextra);
  
  					if (*conf->variable != newval)
  					{
  						record->status |= GUC_PENDING_RESTART;
  						ereport(elevel,
  								(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  								 errmsg("parameter \"%s\" cannot be changed without restarting the server",
  										name)));
  						return 0;
  					}
  					record->status &= ~GUC_PENDING_RESTART;
  					return -1;
  				}
  
  				if (changeVal)
  				{
  					/* Save old value to support transaction abort */
  					if (!makeDefault)
  						push_old_value(&conf->gen, action);
  
  					if (conf->assign_hook)
  						conf->assign_hook(newval, newextra);
  					*conf->variable = newval;
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									newextra);
  					conf->gen.source = source;
  					conf->gen.scontext = context;
  				}
  				if (makeDefault)
  				{
  					GucStack   *stack;
  
  					if (conf->gen.reset_source <= source)
  					{
  						conf->reset_val = newval;
  						set_extra_field(&conf->gen, &conf->reset_extra,
  										newextra);
  						conf->gen.reset_source = source;
  						conf->gen.reset_scontext = context;
  					}
  					for (stack = conf->gen.stack; stack; stack = stack->prev)
  					{
  						if (stack->source <= source)
  						{
  							stack->prior.val.intval = newval;
  							set_extra_field(&conf->gen, &stack->prior.extra,
  											newextra);
  							stack->source = source;
  							stack->scontext = context;
  						}
  					}
  				}
  
  				/* Perhaps we didn't install newextra anywhere */
  				if (newextra && !extra_field_used(&conf->gen, newextra))
  					free(newextra);
  				break;
  
  #undef newval
  			}
  
  		case PGC_REAL:
  			{
  				struct config_real *conf = (struct config_real *) record;
  
  #define newval (newval_union.realval)
  
  				if (value)
  				{
  					if (!parse_and_validate_value(record, name, value,
  												  source, elevel,
  												  &newval_union, &newextra))
  						return 0;
  				}
  				else if (source == PGC_S_DEFAULT)
  				{
  					newval = conf->boot_val;
  					if (!call_real_check_hook(conf, &newval, &newextra,
  											  source, elevel))
  						return 0;
  				}
  				else
  				{
  					newval = conf->reset_val;
  					newextra = conf->reset_extra;
  					source = conf->gen.reset_source;
  					context = conf->gen.reset_scontext;
  				}
  
  				if (prohibitValueChange)
  				{
  					/* Release newextra, unless it's reset_extra */
  					if (newextra && !extra_field_used(&conf->gen, newextra))
  						free(newextra);
  
  					if (*conf->variable != newval)
  					{
  						record->status |= GUC_PENDING_RESTART;
  						ereport(elevel,
  								(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  								 errmsg("parameter \"%s\" cannot be changed without restarting the server",
  										name)));
  						return 0;
  					}
  					record->status &= ~GUC_PENDING_RESTART;
  					return -1;
  				}
  
  				if (changeVal)
  				{
  					/* Save old value to support transaction abort */
  					if (!makeDefault)
  						push_old_value(&conf->gen, action);
  
  					if (conf->assign_hook)
  						conf->assign_hook(newval, newextra);
  					*conf->variable = newval;
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									newextra);
  					conf->gen.source = source;
  					conf->gen.scontext = context;
  				}
  				if (makeDefault)
  				{
  					GucStack   *stack;
  
  					if (conf->gen.reset_source <= source)
  					{
  						conf->reset_val = newval;
  						set_extra_field(&conf->gen, &conf->reset_extra,
  										newextra);
  						conf->gen.reset_source = source;
  						conf->gen.reset_scontext = context;
  					}
  					for (stack = conf->gen.stack; stack; stack = stack->prev)
  					{
  						if (stack->source <= source)
  						{
  							stack->prior.val.realval = newval;
  							set_extra_field(&conf->gen, &stack->prior.extra,
  											newextra);
  							stack->source = source;
  							stack->scontext = context;
  						}
  					}
  				}
  
  				/* Perhaps we didn't install newextra anywhere */
  				if (newextra && !extra_field_used(&conf->gen, newextra))
  					free(newextra);
  				break;
  
  #undef newval
  			}
  
  		case PGC_STRING:
  			{
  				struct config_string *conf = (struct config_string *) record;
  
  #define newval (newval_union.stringval)
  
  				if (value)
  				{
  					if (!parse_and_validate_value(record, name, value,
  												  source, elevel,
  												  &newval_union, &newextra))
  						return 0;
  				}
  				else if (source == PGC_S_DEFAULT)
  				{
  					/* non-NULL boot_val must always get strdup'd */
  					if (conf->boot_val != NULL)
  					{
  						newval = guc_strdup(elevel, conf->boot_val);
  						if (newval == NULL)
  							return 0;
  					}
  					else
  						newval = NULL;
  
  					if (!call_string_check_hook(conf, &newval, &newextra,
  												source, elevel))
  					{
  						free(newval);
  						return 0;
  					}
  				}
  				else
  				{
  					/*
  					 * strdup not needed, since reset_val is already under
  					 * guc.c's control
  					 */
  					newval = conf->reset_val;
  					newextra = conf->reset_extra;
  					source = conf->gen.reset_source;
  					context = conf->gen.reset_scontext;
  				}
  
  				if (prohibitValueChange)
  				{
  					bool		newval_different;
  
  					/* newval shouldn't be NULL, so we're a bit sloppy here */
  					newval_different = (*conf->variable == NULL ||
  										newval == NULL ||
  										strcmp(*conf->variable, newval) != 0);
  
  					/* Release newval, unless it's reset_val */
  					if (newval && !string_field_used(conf, newval))
  						free(newval);
  					/* Release newextra, unless it's reset_extra */
  					if (newextra && !extra_field_used(&conf->gen, newextra))
  						free(newextra);
  
  					if (newval_different)
  					{
  						record->status |= GUC_PENDING_RESTART;
  						ereport(elevel,
  								(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  								 errmsg("parameter \"%s\" cannot be changed without restarting the server",
  										name)));
  						return 0;
  					}
  					record->status &= ~GUC_PENDING_RESTART;
  					return -1;
  				}
  
  				if (changeVal)
  				{
  					/* Save old value to support transaction abort */
  					if (!makeDefault)
  						push_old_value(&conf->gen, action);
  
  					if (conf->assign_hook)
  						conf->assign_hook(newval, newextra);
  					set_string_field(conf, conf->variable, newval);
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									newextra);
  					conf->gen.source = source;
  					conf->gen.scontext = context;
  				}
  
  				if (makeDefault)
  				{
  					GucStack   *stack;
  
  					if (conf->gen.reset_source <= source)
  					{
  						set_string_field(conf, &conf->reset_val, newval);
  						set_extra_field(&conf->gen, &conf->reset_extra,
  										newextra);
  						conf->gen.reset_source = source;
  						conf->gen.reset_scontext = context;
  					}
  					for (stack = conf->gen.stack; stack; stack = stack->prev)
  					{
  						if (stack->source <= source)
  						{
  							set_string_field(conf, &stack->prior.val.stringval,
  											 newval);
  							set_extra_field(&conf->gen, &stack->prior.extra,
  											newextra);
  							stack->source = source;
  							stack->scontext = context;
  						}
  					}
  				}
  
  				/* Perhaps we didn't install newval anywhere */
  				if (newval && !string_field_used(conf, newval))
  					free(newval);
  				/* Perhaps we didn't install newextra anywhere */
  				if (newextra && !extra_field_used(&conf->gen, newextra))
  					free(newextra);
  				break;
  
  #undef newval
  			}
  
  		case PGC_ENUM:
  			{
  				struct config_enum *conf = (struct config_enum *) record;
  
  #define newval (newval_union.enumval)
  
  				if (value)
  				{
  					if (!parse_and_validate_value(record, name, value,
  												  source, elevel,
  												  &newval_union, &newextra))
  						return 0;
  				}
  				else if (source == PGC_S_DEFAULT)
  				{
  					newval = conf->boot_val;
  					if (!call_enum_check_hook(conf, &newval, &newextra,
  											  source, elevel))
  						return 0;
  				}
  				else
  				{
  					newval = conf->reset_val;
  					newextra = conf->reset_extra;
  					source = conf->gen.reset_source;
  					context = conf->gen.reset_scontext;
  				}
  
  				if (prohibitValueChange)
  				{
  					/* Release newextra, unless it's reset_extra */
  					if (newextra && !extra_field_used(&conf->gen, newextra))
  						free(newextra);
  
  					if (*conf->variable != newval)
  					{
  						record->status |= GUC_PENDING_RESTART;
  						ereport(elevel,
  								(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  								 errmsg("parameter \"%s\" cannot be changed without restarting the server",
  										name)));
  						return 0;
  					}
  					record->status &= ~GUC_PENDING_RESTART;
  					return -1;
  				}
  
  				if (changeVal)
  				{
  					/* Save old value to support transaction abort */
  					if (!makeDefault)
  						push_old_value(&conf->gen, action);
  
  					if (conf->assign_hook)
  						conf->assign_hook(newval, newextra);
  					*conf->variable = newval;
  					set_extra_field(&conf->gen, &conf->gen.extra,
  									newextra);
  					conf->gen.source = source;
  					conf->gen.scontext = context;
  				}
  				if (makeDefault)
  				{
  					GucStack   *stack;
  
  					if (conf->gen.reset_source <= source)
  					{
  						conf->reset_val = newval;
  						set_extra_field(&conf->gen, &conf->reset_extra,
  										newextra);
  						conf->gen.reset_source = source;
  						conf->gen.reset_scontext = context;
  					}
  					for (stack = conf->gen.stack; stack; stack = stack->prev)
  					{
  						if (stack->source <= source)
  						{
  							stack->prior.val.enumval = newval;
  							set_extra_field(&conf->gen, &stack->prior.extra,
  											newextra);
  							stack->source = source;
  							stack->scontext = context;
  						}
  					}
  				}
  
  				/* Perhaps we didn't install newextra anywhere */
  				if (newextra && !extra_field_used(&conf->gen, newextra))
  					free(newextra);
  				break;
  
  #undef newval
  			}
  	}
  
  	if (changeVal && (record->flags & GUC_REPORT))
  	{
  		record->status |= GUC_NEEDS_REPORT;
  		report_needed = true;
  	}
  
  	return changeVal ? 1 : -1;
  }
  
  
  /*
   * Set the fields for source file and line number the setting came from.
   */
  static void
  set_config_sourcefile(const char *name, char *sourcefile, int sourceline)
  {
  	struct config_generic *record;
  	int			elevel;
  
  	/*
  	 * To avoid cluttering the log, only the postmaster bleats loudly about
  	 * problems with the config file.
  	 */
  	elevel = IsUnderPostmaster ? DEBUG3 : LOG;
  
  	record = find_option(name, true, false, elevel);
  	/* should not happen */
  	if (record == NULL)
  		return;
  
  	sourcefile = guc_strdup(elevel, sourcefile);
  	if (record->sourcefile)
  		free(record->sourcefile);
  	record->sourcefile = sourcefile;
  	record->sourceline = sourceline;
  }
  
  /*
   * Set a config option to the given value.
   *
   * See also set_config_option; this is just the wrapper to be called from
   * outside GUC.  (This function should be used when possible, because its API
   * is more stable than set_config_option's.)
   *
   * Note: there is no support here for setting source file/line, as it
   * is currently not needed.
   */
  void
  SetConfigOption(const char *name, const char *value,
  				GucContext context, GucSource source)
  {
  	(void) set_config_option(name, value, context, source,
  							 GUC_ACTION_SET, true, 0, false);
  }
  
  
  
  /*
   * Fetch the current value of the option `name', as a string.
   *
   * If the option doesn't exist, return NULL if missing_ok is true (NOTE that
   * this cannot be distinguished from a string variable with a NULL value!),
   * otherwise throw an ereport and don't return.
   *
   * If restrict_privileged is true, we also enforce that only superusers and
   * members of the pg_read_all_settings role can see GUC_SUPERUSER_ONLY
   * variables.  This should only be passed as true in user-driven calls.
   *
   * The string is *not* allocated for modification and is really only
   * valid until the next call to configuration related functions.
   */
  const char *
  GetConfigOption(const char *name, bool missing_ok, bool restrict_privileged)
  {
  	struct config_generic *record;
  	static char buffer[256];
  
  	record = find_option(name, false, missing_ok, ERROR);
  	if (record == NULL)
  		return NULL;
  	if (restrict_privileged &&
  		(record->flags & GUC_SUPERUSER_ONLY) &&
  		!is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_SETTINGS))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("must be superuser or a member of pg_read_all_settings to examine \"%s\"",
  						name)));
  
  	switch (record->vartype)
  	{
  		case PGC_BOOL:
  			return *((struct config_bool *) record)->variable ? "on" : "off";
  
  		case PGC_INT:
  			snprintf(buffer, sizeof(buffer), "%d",
  					 *((struct config_int *) record)->variable);
  			return buffer;
  
  		case PGC_REAL:
  			snprintf(buffer, sizeof(buffer), "%g",
  					 *((struct config_real *) record)->variable);
  			return buffer;
  
  		case PGC_STRING:
  			return *((struct config_string *) record)->variable;
  
  		case PGC_ENUM:
  			return config_enum_lookup_by_value((struct config_enum *) record,
  											   *((struct config_enum *) record)->variable);
  	}
  	return NULL;
  }
  
  /*
   * Get the RESET value associated with the given option.
   *
   * Note: this is not re-entrant, due to use of static result buffer;
   * not to mention that a string variable could have its reset_val changed.
   * Beware of assuming the result value is good for very long.
   */
  const char *
  GetConfigOptionResetString(const char *name)
  {
  	struct config_generic *record;
  	static char buffer[256];
  
  	record = find_option(name, false, false, ERROR);
  	Assert(record != NULL);
  	if ((record->flags & GUC_SUPERUSER_ONLY) &&
  		!is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_SETTINGS))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("must be superuser or a member of pg_read_all_settings to examine \"%s\"",
  						name)));
  
  	switch (record->vartype)
  	{
  		case PGC_BOOL:
  			return ((struct config_bool *) record)->reset_val ? "on" : "off";
  
  		case PGC_INT:
  			snprintf(buffer, sizeof(buffer), "%d",
  					 ((struct config_int *) record)->reset_val);
  			return buffer;
  
  		case PGC_REAL:
  			snprintf(buffer, sizeof(buffer), "%g",
  					 ((struct config_real *) record)->reset_val);
  			return buffer;
  
  		case PGC_STRING:
  			return ((struct config_string *) record)->reset_val;
  
  		case PGC_ENUM:
  			return config_enum_lookup_by_value((struct config_enum *) record,
  											   ((struct config_enum *) record)->reset_val);
  	}
  	return NULL;
  }
  
  /*
   * Get the GUC flags associated with the given option.
   *
   * If the option doesn't exist, return 0 if missing_ok is true,
   * otherwise throw an ereport and don't return.
   */
  int
  GetConfigOptionFlags(const char *name, bool missing_ok)
  {
  	struct config_generic *record;
  
  	record = find_option(name, false, missing_ok, ERROR);
  	if (record == NULL)
  		return 0;
  	return record->flags;
  }
  
  
  /*
   * flatten_set_variable_args
   *		Given a parsenode List as emitted by the grammar for SET,
   *		convert to the flat string representation used by GUC.
   *
   * We need to be told the name of the variable the args are for, because
   * the flattening rules vary (ugh).
   *
   * The result is NULL if args is NIL (i.e., SET ... TO DEFAULT), otherwise
   * a palloc'd string.
   */
  static char *
  flatten_set_variable_args(const char *name, List *args)
  {
  	struct config_generic *record;
  	int			flags;
  	StringInfoData buf;
  	ListCell   *l;
  
  	/* Fast path if just DEFAULT */
  	if (args == NIL)
  		return NULL;
  
  	/*
  	 * Get flags for the variable; if it's not known, use default flags.
  	 * (Caller might throw error later, but not our business to do so here.)
  	 */
  	record = find_option(name, false, true, WARNING);
  	if (record)
  		flags = record->flags;
  	else
  		flags = 0;
  
  	/* Complain if list input and non-list variable */
  	if ((flags & GUC_LIST_INPUT) == 0 &&
  		list_length(args) != 1)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("SET %s takes only one argument", name)));
  
  	initStringInfo(&buf);
  
  	/*
  	 * Each list member may be a plain A_Const node, or an A_Const within a
  	 * TypeCast; the latter case is supported only for ConstInterval arguments
  	 * (for SET TIME ZONE).
  	 */
  	foreach(l, args)
  	{
  		Node	   *arg = (Node *) lfirst(l);
  		char	   *val;
  		TypeName   *typeName = NULL;
  		A_Const    *con;
  
  		if (l != list_head(args))
  			appendStringInfoString(&buf, ", ");
  
  		if (IsA(arg, TypeCast))
  		{
  			TypeCast   *tc = (TypeCast *) arg;
  
  			arg = tc->arg;
  			typeName = tc->typeName;
  		}
  
  		if (!IsA(arg, A_Const))
  			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(arg));
  		con = (A_Const *) arg;
  
  		switch (nodeTag(&con->val))
  		{
  			case T_Integer:
  				appendStringInfo(&buf, "%d", intVal(&con->val));
  				break;
  			case T_Float:
  				/* represented as a string, so just copy it */
  				appendStringInfoString(&buf, strVal(&con->val));
  				break;
  			case T_String:
  				val = strVal(&con->val);
  				if (typeName != NULL)
  				{
  					/*
  					 * Must be a ConstInterval argument for TIME ZONE. Coerce
  					 * to interval and back to normalize the value and account
  					 * for any typmod.
  					 */
  					Oid			typoid;
  					int32		typmod;
  					Datum		interval;
  					char	   *intervalout;
  
  					typenameTypeIdAndMod(NULL, typeName, &typoid, &typmod);
  					Assert(typoid == INTERVALOID);
  
  					interval =
  						DirectFunctionCall3(interval_in,
  											CStringGetDatum(val),
  											ObjectIdGetDatum(InvalidOid),
  											Int32GetDatum(typmod));
  
  					intervalout =
  						DatumGetCString(DirectFunctionCall1(interval_out,
  															interval));
  					appendStringInfo(&buf, "INTERVAL '%s'", intervalout);
  				}
  				else
  				{
  					/*
  					 * Plain string literal or identifier.  For quote mode,
  					 * quote it if it's not a vanilla identifier.
  					 */
  					if (flags & GUC_LIST_QUOTE)
  						appendStringInfoString(&buf, quote_identifier(val));
  					else
  						appendStringInfoString(&buf, val);
  				}
  				break;
  			default:
  				elog(ERROR, "unrecognized node type: %d",
  					 (int) nodeTag(&con->val));
  				break;
  		}
  	}
  
  	return buf.data;
  }
  
  /*
   * Write updated configuration parameter values into a temporary file.
   * This function traverses the list of parameters and quotes the string
   * values before writing them.
   */
  static void
  write_auto_conf_file(int fd, const char *filename, ConfigVariable *head)
  {
  	StringInfoData buf;
  	ConfigVariable *item;
  
  	initStringInfo(&buf);
  
  	/* Emit file header containing warning comment */
  	appendStringInfoString(&buf, "# Do not edit this file manually!\n");
  	appendStringInfoString(&buf, "# It will be overwritten by the ALTER SYSTEM command.\n");
  
  	errno = 0;
  	if (write(fd, buf.data, buf.len) != buf.len)
  	{
  		/* if write didn't set errno, assume problem is no disk space */
  		if (errno == 0)
  			errno = ENOSPC;
  		ereport(ERROR,
  				(errcode_for_file_access(),
  				 errmsg("could not write to file \"%s\": %m", filename)));
  	}
  
  	/* Emit each parameter, properly quoting the value */
  	for (item = head; item != NULL; item = item->next)
  	{
  		char	   *escaped;
  
  		resetStringInfo(&buf);
  
  		appendStringInfoString(&buf, item->name);
  		appendStringInfoString(&buf, " = '");
  
  		escaped = escape_single_quotes_ascii(item->value);
  		if (!escaped)
  			ereport(ERROR,
  					(errcode(ERRCODE_OUT_OF_MEMORY),
  					 errmsg("out of memory")));
  		appendStringInfoString(&buf, escaped);
  		free(escaped);
  
  		appendStringInfoString(&buf, "'\n");
  
  		errno = 0;
  		if (write(fd, buf.data, buf.len) != buf.len)
  		{
  			/* if write didn't set errno, assume problem is no disk space */
  			if (errno == 0)
  				errno = ENOSPC;
  			ereport(ERROR,
  					(errcode_for_file_access(),
  					 errmsg("could not write to file \"%s\": %m", filename)));
  		}
  	}
  
  	/* fsync before considering the write to be successful */
  	if (pg_fsync(fd) != 0)
  		ereport(ERROR,
  				(errcode_for_file_access(),
  				 errmsg("could not fsync file \"%s\": %m", filename)));
  
  	pfree(buf.data);
  }
  
  /*
   * Update the given list of configuration parameters, adding, replacing
   * or deleting the entry for item "name" (delete if "value" == NULL).
   */
  static void
  replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
  						  const char *name, const char *value)
  {
  	ConfigVariable *item,
  			   *next,
  			   *prev = NULL;
  
  	/*
  	 * Remove any existing match(es) for "name".  Normally there'd be at most
  	 * one, but if external tools have modified the config file, there could
  	 * be more.
  	 */
  	for (item = *head_p; item != NULL; item = next)
  	{
  		next = item->next;
  		if (guc_name_compare(item->name, name) == 0)
  		{
  			/* found a match, delete it */
  			if (prev)
  				prev->next = next;
  			else
  				*head_p = next;
  			if (next == NULL)
  				*tail_p = prev;
  
  			pfree(item->name);
  			pfree(item->value);
  			pfree(item->filename);
  			pfree(item);
  		}
  		else
  			prev = item;
  	}
  
  	/* Done if we're trying to delete it */
  	if (value == NULL)
  		return;
  
  	/* OK, append a new entry */
  	item = palloc(sizeof *item);
  	item->name = pstrdup(name);
  	item->value = pstrdup(value);
  	item->errmsg = NULL;
  	item->filename = pstrdup("");	/* new item has no location */
  	item->sourceline = 0;
  	item->ignore = false;
  	item->applied = false;
  	item->next = NULL;
  
  	if (*head_p == NULL)
  		*head_p = item;
  	else
  		(*tail_p)->next = item;
  	*tail_p = item;
  }
  
  
  /*
   * Execute ALTER SYSTEM statement.
   *
   * Read the old PG_AUTOCONF_FILENAME file, merge in the new variable value,
   * and write out an updated file.  If the command is ALTER SYSTEM RESET ALL,
   * we can skip reading the old file and just write an empty file.
   *
   * An LWLock is used to serialize updates of the configuration file.
   *
   * In case of an error, we leave the original automatic
   * configuration file (PG_AUTOCONF_FILENAME) intact.
   */
  void
  AlterSystemSetConfigFile(AlterSystemStmt *altersysstmt)
  {
  	char	   *name;
  	char	   *value;
  	bool		resetall = false;
  	ConfigVariable *head = NULL;
  	ConfigVariable *tail = NULL;
  	volatile int Tmpfd;
  	char		AutoConfFileName[MAXPGPATH];
  	char		AutoConfTmpFileName[MAXPGPATH];
  
  	if (!superuser())
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("must be superuser to execute ALTER SYSTEM command")));
  
  	/*
  	 * Extract statement arguments
  	 */
  	name = altersysstmt->setstmt->name;
  
  	switch (altersysstmt->setstmt->kind)
  	{
  		case VAR_SET_VALUE:
  			value = ExtractSetVariableArgs(altersysstmt->setstmt);
  			break;
  
  		case VAR_SET_DEFAULT:
  		case VAR_RESET:
  			value = NULL;
  			break;
  
  		case VAR_RESET_ALL:
  			value = NULL;
  			resetall = true;
  			break;
  
  		default:
  			elog(ERROR, "unrecognized alter system stmt type: %d",
  				 altersysstmt->setstmt->kind);
  			break;
  	}
  
  	/*
  	 * Unless it's RESET_ALL, validate the target variable and value
  	 */
  	if (!resetall)
  	{
  		struct config_generic *record;
  
  		record = find_option(name, false, false, ERROR);
  		Assert(record != NULL);
  
  		/*
  		 * Don't allow parameters that can't be set in configuration files to
  		 * be set in PG_AUTOCONF_FILENAME file.
  		 */
  		if ((record->context == PGC_INTERNAL) ||
  			(record->flags & GUC_DISALLOW_IN_FILE) ||
  			(record->flags & GUC_DISALLOW_IN_AUTO_FILE))
  			ereport(ERROR,
  					(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  					 errmsg("parameter \"%s\" cannot be changed",
  							name)));
  
  		/*
  		 * If a value is specified, verify that it's sane.
  		 */
  		if (value)
  		{
  			union config_var_val newval;
  			void	   *newextra = NULL;
  
  			/* Check that it's acceptable for the indicated parameter */
  			if (!parse_and_validate_value(record, name, value,
  										  PGC_S_FILE, ERROR,
  										  &newval, &newextra))
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  						 errmsg("invalid value for parameter \"%s\": \"%s\"",
  								name, value)));
  
  			if (record->vartype == PGC_STRING && newval.stringval != NULL)
  				free(newval.stringval);
  			if (newextra)
  				free(newextra);
  
  			/*
  			 * We must also reject values containing newlines, because the
  			 * grammar for config files doesn't support embedded newlines in
  			 * string literals.
  			 */
  			if (strchr(value, '\n'))
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  						 errmsg("parameter value for ALTER SYSTEM must not contain a newline")));
  		}
  	}
  
  	/*
  	 * PG_AUTOCONF_FILENAME and its corresponding temporary file are always in
  	 * the data directory, so we can reference them by simple relative paths.
  	 */
  	snprintf(AutoConfFileName, sizeof(AutoConfFileName), "%s",
  			 PG_AUTOCONF_FILENAME);
  	snprintf(AutoConfTmpFileName, sizeof(AutoConfTmpFileName), "%s.%s",
  			 AutoConfFileName,
  			 "tmp");
  
  	/*
  	 * Only one backend is allowed to operate on PG_AUTOCONF_FILENAME at a
  	 * time.  Use AutoFileLock to ensure that.  We must hold the lock while
  	 * reading the old file contents.
  	 */
  	LWLockAcquire(AutoFileLock, LW_EXCLUSIVE);
  
  	/*
  	 * If we're going to reset everything, then no need to open or parse the
  	 * old file.  We'll just write out an empty list.
  	 */
  	if (!resetall)
  	{
  		struct stat st;
  
  		if (stat(AutoConfFileName, &st) == 0)
  		{
  			/* open old file PG_AUTOCONF_FILENAME */
  			FILE	   *infile;
  
  			infile = AllocateFile(AutoConfFileName, "r");
  			if (infile == NULL)
  				ereport(ERROR,
  						(errcode_for_file_access(),
  						 errmsg("could not open file \"%s\": %m",
  								AutoConfFileName)));
  
  			/* parse it */
  			if (!ParseConfigFp(infile, AutoConfFileName, 0, LOG, &head, &tail))
  				ereport(ERROR,
  						(errcode(ERRCODE_CONFIG_FILE_ERROR),
  						 errmsg("could not parse contents of file \"%s\"",
  								AutoConfFileName)));
  
  			FreeFile(infile);
  		}
  
  		/*
  		 * Now, replace any existing entry with the new value, or add it if
  		 * not present.
  		 */
  		replace_auto_config_value(&head, &tail, name, value);
  	}
  
  	/*
  	 * To ensure crash safety, first write the new file data to a temp file,
  	 * then atomically rename it into place.
  	 *
  	 * If there is a temp file left over due to a previous crash, it's okay to
  	 * truncate and reuse it.
  	 */
  	Tmpfd = BasicOpenFile(AutoConfTmpFileName,
  						  O_CREAT | O_RDWR | O_TRUNC);
  	if (Tmpfd < 0)
  		ereport(ERROR,
  				(errcode_for_file_access(),
  				 errmsg("could not open file \"%s\": %m",
  						AutoConfTmpFileName)));
  
  	/*
  	 * Use a TRY block to clean up the file if we fail.  Since we need a TRY
  	 * block anyway, OK to use BasicOpenFile rather than OpenTransientFile.
  	 */
  	PG_TRY();
  	{
  		/* Write and sync the new contents to the temporary file */
  		write_auto_conf_file(Tmpfd, AutoConfTmpFileName, head);
  
  		/* Close before renaming; may be required on some platforms */
  		close(Tmpfd);
  		Tmpfd = -1;
  
  		/*
  		 * As the rename is atomic operation, if any problem occurs after this
  		 * at worst it can lose the parameters set by last ALTER SYSTEM
  		 * command.
  		 */
  		durable_rename(AutoConfTmpFileName, AutoConfFileName, ERROR);
  	}
  	PG_CATCH();
  	{
  		/* Close file first, else unlink might fail on some platforms */
  		if (Tmpfd >= 0)
  			close(Tmpfd);
  
  		/* Unlink, but ignore any error */
  		(void) unlink(AutoConfTmpFileName);
  
  		PG_RE_THROW();
  	}
  	PG_END_TRY();
  
  	FreeConfigVariables(head);
  
  	LWLockRelease(AutoFileLock);
  }
  
  /*
   * SET command
   */
  void
  ExecSetVariableStmt(VariableSetStmt *stmt, bool isTopLevel)
  {
  	GucAction	action = stmt->is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET;
  
  	/*
  	 * Workers synchronize these parameters at the start of the parallel
  	 * operation; then, we block SET during the operation.
  	 */
  	if (IsInParallelMode())
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
  				 errmsg("cannot set parameters during a parallel operation")));
  
  	switch (stmt->kind)
  	{
  		case VAR_SET_VALUE:
  		case VAR_SET_CURRENT:
  			if (stmt->is_local)
  				WarnNoTransactionBlock(isTopLevel, "SET LOCAL");
  			(void) set_config_option(stmt->name,
  									 ExtractSetVariableArgs(stmt),
  									 (superuser() ? PGC_SUSET : PGC_USERSET),
  									 PGC_S_SESSION,
  									 action, true, 0, false);
  			break;
  		case VAR_SET_MULTI:
  
  			/*
  			 * Special-case SQL syntaxes.  The TRANSACTION and SESSION
  			 * CHARACTERISTICS cases effectively set more than one variable
  			 * per statement.  TRANSACTION SNAPSHOT only takes one argument,
  			 * but we put it here anyway since it's a special case and not
  			 * related to any GUC variable.
  			 */
  			if (strcmp(stmt->name, "TRANSACTION") == 0)
  			{
  				ListCell   *head;
  
  				WarnNoTransactionBlock(isTopLevel, "SET TRANSACTION");
  
  				foreach(head, stmt->args)
  				{
  					DefElem    *item = (DefElem *) lfirst(head);
  
  					if (strcmp(item->defname, "transaction_isolation") == 0)
  						SetPGVariable("transaction_isolation",
  									  list_make1(item->arg), stmt->is_local);
  					else if (strcmp(item->defname, "transaction_read_only") == 0)
  						SetPGVariable("transaction_read_only",
  									  list_make1(item->arg), stmt->is_local);
  					else if (strcmp(item->defname, "transaction_deferrable") == 0)
  						SetPGVariable("transaction_deferrable",
  									  list_make1(item->arg), stmt->is_local);
  					else
  						elog(ERROR, "unexpected SET TRANSACTION element: %s",
  							 item->defname);
  				}
  			}
  			else if (strcmp(stmt->name, "SESSION CHARACTERISTICS") == 0)
  			{
  				ListCell   *head;
  
  				foreach(head, stmt->args)
  				{
  					DefElem    *item = (DefElem *) lfirst(head);
  
  					if (strcmp(item->defname, "transaction_isolation") == 0)
  						SetPGVariable("default_transaction_isolation",
  									  list_make1(item->arg), stmt->is_local);
  					else if (strcmp(item->defname, "transaction_read_only") == 0)
  						SetPGVariable("default_transaction_read_only",
  									  list_make1(item->arg), stmt->is_local);
  					else if (strcmp(item->defname, "transaction_deferrable") == 0)
  						SetPGVariable("default_transaction_deferrable",
  									  list_make1(item->arg), stmt->is_local);
  					else
  						elog(ERROR, "unexpected SET SESSION element: %s",
  							 item->defname);
  				}
  			}
  			else if (strcmp(stmt->name, "TRANSACTION SNAPSHOT") == 0)
  			{
  				A_Const    *con = linitial_node(A_Const, stmt->args);
  
  				if (stmt->is_local)
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("SET LOCAL TRANSACTION SNAPSHOT is not implemented")));
  
  				WarnNoTransactionBlock(isTopLevel, "SET TRANSACTION");
  				Assert(nodeTag(&con->val) == T_String);
  				ImportSnapshot(strVal(&con->val));
  			}
  			else
  				elog(ERROR, "unexpected SET MULTI element: %s",
  					 stmt->name);
  			break;
  		case VAR_SET_DEFAULT:
  			if (stmt->is_local)
  				WarnNoTransactionBlock(isTopLevel, "SET LOCAL");
  			/* fall through */
  		case VAR_RESET:
  			if (strcmp(stmt->name, "transaction_isolation") == 0)
  				WarnNoTransactionBlock(isTopLevel, "RESET TRANSACTION");
  
  			(void) set_config_option(stmt->name,
  									 NULL,
  									 (superuser() ? PGC_SUSET : PGC_USERSET),
  									 PGC_S_SESSION,
  									 action, true, 0, false);
  			break;
  		case VAR_RESET_ALL:
  			ResetAllOptions();
  			break;
  	}
  }
  
  /*
   * Get the value to assign for a VariableSetStmt, or NULL if it's RESET.
   * The result is palloc'd.
   *
   * This is exported for use by actions such as ALTER ROLE SET.
   */
  char *
  ExtractSetVariableArgs(VariableSetStmt *stmt)
  {
  	switch (stmt->kind)
  	{
  		case VAR_SET_VALUE:
  			return flatten_set_variable_args(stmt->name, stmt->args);
  		case VAR_SET_CURRENT:
  			return GetConfigOptionByName(stmt->name, NULL, false);
  		default:
  			return NULL;
  	}
  }
  
  /*
   * SetPGVariable - SET command exported as an easily-C-callable function.
   *
   * This provides access to SET TO value, as well as SET TO DEFAULT (expressed
   * by passing args == NIL), but not SET FROM CURRENT functionality.
   */
  void
  SetPGVariable(const char *name, List *args, bool is_local)
  {
  	char	   *argstring = flatten_set_variable_args(name, args);
  
  	/* Note SET DEFAULT (argstring == NULL) is equivalent to RESET */
  	(void) set_config_option(name,
  							 argstring,
  							 (superuser() ? PGC_SUSET : PGC_USERSET),
  							 PGC_S_SESSION,
  							 is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET,
  							 true, 0, false);
  }
  
  /*
   * SET command wrapped as a SQL callable function.
   */
  Datum
  set_config_by_name(PG_FUNCTION_ARGS)
  {
  	char	   *name;
  	char	   *value;
  	char	   *new_value;
  	bool		is_local;
  
  	if (PG_ARGISNULL(0))
  		ereport(ERROR,
  				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
  				 errmsg("SET requires parameter name")));
  
  	/* Get the GUC variable name */
  	name = TextDatumGetCString(PG_GETARG_DATUM(0));
  
  	/* Get the desired value or set to NULL for a reset request */
  	if (PG_ARGISNULL(1))
  		value = NULL;
  	else
  		value = TextDatumGetCString(PG_GETARG_DATUM(1));
  
  	/*
  	 * Get the desired state of is_local. Default to false if provided value
  	 * is NULL
  	 */
  	if (PG_ARGISNULL(2))
  		is_local = false;
  	else
  		is_local = PG_GETARG_BOOL(2);
  
  	/* Note SET DEFAULT (argstring == NULL) is equivalent to RESET */
  	(void) set_config_option(name,
  							 value,
  							 (superuser() ? PGC_SUSET : PGC_USERSET),
  							 PGC_S_SESSION,
  							 is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET,
  							 true, 0, false);
  
  	/* get the new current value */
  	new_value = GetConfigOptionByName(name, NULL, false);
  
  	/* Convert return string to text */
  	PG_RETURN_TEXT_P(cstring_to_text(new_value));
  }
  
  
  /*
   * Common code for DefineCustomXXXVariable subroutines: allocate the
   * new variable's config struct and fill in generic fields.
   */
  static struct config_generic *
  init_custom_variable(const char *name,
  					 const char *short_desc,
  					 const char *long_desc,
  					 GucContext context,
  					 int flags,
  					 enum config_type type,
  					 size_t sz)
  {
  	struct config_generic *gen;
  
  	/*
  	 * Only allow custom PGC_POSTMASTER variables to be created during shared
  	 * library preload; any later than that, we can't ensure that the value
  	 * doesn't change after startup.  This is a fatal elog if it happens; just
  	 * erroring out isn't safe because we don't know what the calling loadable
  	 * module might already have hooked into.
  	 */
  	if (context == PGC_POSTMASTER &&
  		!process_shared_preload_libraries_in_progress)
  		elog(FATAL, "cannot create PGC_POSTMASTER variables after startup");
  
  	/*
  	 * We can't support custom GUC_LIST_QUOTE variables, because the wrong
  	 * things would happen if such a variable were set or pg_dump'd when the
  	 * defining extension isn't loaded.  Again, treat this as fatal because
  	 * the loadable module may be partly initialized already.
  	 */
  	if (flags & GUC_LIST_QUOTE)
  		elog(FATAL, "extensions cannot define GUC_LIST_QUOTE variables");
  
  	/*
  	 * Before pljava commit 398f3b876ed402bdaec8bc804f29e2be95c75139
  	 * (2015-12-15), two of that module's PGC_USERSET variables facilitated
  	 * trivial escalation to superuser privileges.  Restrict the variables to
  	 * protect sites that have yet to upgrade pljava.
  	 */
  	if (context == PGC_USERSET &&
  		(strcmp(name, "pljava.classpath") == 0 ||
  		 strcmp(name, "pljava.vmoptions") == 0))
  		context = PGC_SUSET;
  
  	gen = (struct config_generic *) guc_malloc(ERROR, sz);
  	memset(gen, 0, sz);
  
  	gen->name = guc_strdup(ERROR, name);
  	gen->context = context;
  	gen->group = CUSTOM_OPTIONS;
  	gen->short_desc = short_desc;
  	gen->long_desc = long_desc;
  	gen->flags = flags;
  	gen->vartype = type;
  
  	return gen;
  }
  
  /*
   * Common code for DefineCustomXXXVariable subroutines: insert the new
   * variable into the GUC variable array, replacing any placeholder.
   */
  static void
  define_custom_variable(struct config_generic *variable)
  {
  	const char *name = variable->name;
  	const char **nameAddr = &name;
  	struct config_string *pHolder;
  	struct config_generic **res;
  
  	/*
  	 * See if there's a placeholder by the same name.
  	 */
  	res = (struct config_generic **) bsearch((void *) &nameAddr,
  											 (void *) guc_variables,
  											 num_guc_variables,
  											 sizeof(struct config_generic *),
  											 guc_var_compare);
  	if (res == NULL)
  	{
  		/*
  		 * No placeholder to replace, so we can just add it ... but first,
  		 * make sure it's initialized to its default value.
  		 */
  		InitializeOneGUCOption(variable);
  		add_guc_variable(variable, ERROR);
  		return;
  	}
  
  	/*
  	 * This better be a placeholder
  	 */
  	if (((*res)->flags & GUC_CUSTOM_PLACEHOLDER) == 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_INTERNAL_ERROR),
  				 errmsg("attempt to redefine parameter \"%s\"", name)));
  
  	Assert((*res)->vartype == PGC_STRING);
  	pHolder = (struct config_string *) (*res);
  
  	/*
  	 * First, set the variable to its default value.  We must do this even
  	 * though we intend to immediately apply a new value, since it's possible
  	 * that the new value is invalid.
  	 */
  	InitializeOneGUCOption(variable);
  
  	/*
  	 * Replace the placeholder. We aren't changing the name, so no re-sorting
  	 * is necessary
  	 */
  	*res = variable;
  
  	/*
  	 * Assign the string value(s) stored in the placeholder to the real
  	 * variable.  Essentially, we need to duplicate all the active and stacked
  	 * values, but with appropriate validation and datatype adjustment.
  	 *
  	 * If an assignment fails, we report a WARNING and keep going.  We don't
  	 * want to throw ERROR for bad values, because it'd bollix the add-on
  	 * module that's presumably halfway through getting loaded.  In such cases
  	 * the default or previous state will become active instead.
  	 */
  
  	/* First, apply the reset value if any */
  	if (pHolder->reset_val)
  		(void) set_config_option(name, pHolder->reset_val,
  								 pHolder->gen.reset_scontext,
  								 pHolder->gen.reset_source,
  								 GUC_ACTION_SET, true, WARNING, false);
  	/* That should not have resulted in stacking anything */
  	Assert(variable->stack == NULL);
  
  	/* Now, apply current and stacked values, in the order they were stacked */
  	reapply_stacked_values(variable, pHolder, pHolder->gen.stack,
  						   *(pHolder->variable),
  						   pHolder->gen.scontext, pHolder->gen.source);
  
  	/* Also copy over any saved source-location information */
  	if (pHolder->gen.sourcefile)
  		set_config_sourcefile(name, pHolder->gen.sourcefile,
  							  pHolder->gen.sourceline);
  
  	/*
  	 * Free up as much as we conveniently can of the placeholder structure.
  	 * (This neglects any stack items, so it's possible for some memory to be
  	 * leaked.  Since this can only happen once per session per variable, it
  	 * doesn't seem worth spending much code on.)
  	 */
  	set_string_field(pHolder, pHolder->variable, NULL);
  	set_string_field(pHolder, &pHolder->reset_val, NULL);
  
  	free(pHolder);
  }
  
  /*
   * Recursive subroutine for define_custom_variable: reapply non-reset values
   *
   * We recurse so that the values are applied in the same order as originally.
   * At each recursion level, apply the upper-level value (passed in) in the
   * fashion implied by the stack entry.
   */
  static void
  reapply_stacked_values(struct config_generic *variable,
  					   struct config_string *pHolder,
  					   GucStack *stack,
  					   const char *curvalue,
  					   GucContext curscontext, GucSource cursource)
  {
  	const char *name = variable->name;
  	GucStack   *oldvarstack = variable->stack;
  
  	if (stack != NULL)
  	{
  		/* First, recurse, so that stack items are processed bottom to top */
  		reapply_stacked_values(variable, pHolder, stack->prev,
  							   stack->prior.val.stringval,
  							   stack->scontext, stack->source);
  
  		/* See how to apply the passed-in value */
  		switch (stack->state)
  		{
  			case GUC_SAVE:
  				(void) set_config_option(name, curvalue,
  										 curscontext, cursource,
  										 GUC_ACTION_SAVE, true,
  										 WARNING, false);
  				break;
  
  			case GUC_SET:
  				(void) set_config_option(name, curvalue,
  										 curscontext, cursource,
  										 GUC_ACTION_SET, true,
  										 WARNING, false);
  				break;
  
  			case GUC_LOCAL:
  				(void) set_config_option(name, curvalue,
  										 curscontext, cursource,
  										 GUC_ACTION_LOCAL, true,
  										 WARNING, false);
  				break;
  
  			case GUC_SET_LOCAL:
  				/* first, apply the masked value as SET */
  				(void) set_config_option(name, stack->masked.val.stringval,
  										 stack->masked_scontext, PGC_S_SESSION,
  										 GUC_ACTION_SET, true,
  										 WARNING, false);
  				/* then apply the current value as LOCAL */
  				(void) set_config_option(name, curvalue,
  										 curscontext, cursource,
  										 GUC_ACTION_LOCAL, true,
  										 WARNING, false);
  				break;
  		}
  
  		/* If we successfully made a stack entry, adjust its nest level */
  		if (variable->stack != oldvarstack)
  			variable->stack->nest_level = stack->nest_level;
  	}
  	else
  	{
  		/*
  		 * We are at the end of the stack.  If the active/previous value is
  		 * different from the reset value, it must represent a previously
  		 * committed session value.  Apply it, and then drop the stack entry
  		 * that set_config_option will have created under the impression that
  		 * this is to be just a transactional assignment.  (We leak the stack
  		 * entry.)
  		 */
  		if (curvalue != pHolder->reset_val ||
  			curscontext != pHolder->gen.reset_scontext ||
  			cursource != pHolder->gen.reset_source)
  		{
  			(void) set_config_option(name, curvalue,
  									 curscontext, cursource,
  									 GUC_ACTION_SET, true, WARNING, false);
  			variable->stack = NULL;
  		}
  	}
  }
  
  void
  DefineCustomBoolVariable(const char *name,
  						 const char *short_desc,
  						 const char *long_desc,
  						 bool *valueAddr,
  						 bool bootValue,
  						 GucContext context,
  						 int flags,
  						 GucBoolCheckHook check_hook,
  						 GucBoolAssignHook assign_hook,
  						 GucShowHook show_hook)
  {
  	struct config_bool *var;
  
  	var = (struct config_bool *)
  		init_custom_variable(name, short_desc, long_desc, context, flags,
  							 PGC_BOOL, sizeof(struct config_bool));
  	var->variable = valueAddr;
  	var->boot_val = bootValue;
  	var->reset_val = bootValue;
  	var->check_hook = check_hook;
  	var->assign_hook = assign_hook;
  	var->show_hook = show_hook;
  	define_custom_variable(&var->gen);
  }
  
  void
  DefineCustomIntVariable(const char *name,
  						const char *short_desc,
  						const char *long_desc,
  						int *valueAddr,
  						int bootValue,
  						int minValue,
  						int maxValue,
  						GucContext context,
  						int flags,
  						GucIntCheckHook check_hook,
  						GucIntAssignHook assign_hook,
  						GucShowHook show_hook)
  {
  	struct config_int *var;
  
  	var = (struct config_int *)
  		init_custom_variable(name, short_desc, long_desc, context, flags,
  							 PGC_INT, sizeof(struct config_int));
  	var->variable = valueAddr;
  	var->boot_val = bootValue;
  	var->reset_val = bootValue;
  	var->min = minValue;
  	var->max = maxValue;
  	var->check_hook = check_hook;
  	var->assign_hook = assign_hook;
  	var->show_hook = show_hook;
  	define_custom_variable(&var->gen);
  }
  
  void
  DefineCustomRealVariable(const char *name,
  						 const char *short_desc,
  						 const char *long_desc,
  						 double *valueAddr,
  						 double bootValue,
  						 double minValue,
  						 double maxValue,
  						 GucContext context,
  						 int flags,
  						 GucRealCheckHook check_hook,
  						 GucRealAssignHook assign_hook,
  						 GucShowHook show_hook)
  {
  	struct config_real *var;
  
  	var = (struct config_real *)
  		init_custom_variable(name, short_desc, long_desc, context, flags,
  							 PGC_REAL, sizeof(struct config_real));
  	var->variable = valueAddr;
  	var->boot_val = bootValue;
  	var->reset_val = bootValue;
  	var->min = minValue;
  	var->max = maxValue;
  	var->check_hook = check_hook;
  	var->assign_hook = assign_hook;
  	var->show_hook = show_hook;
  	define_custom_variable(&var->gen);
  }
  
  void
  DefineCustomStringVariable(const char *name,
  						   const char *short_desc,
  						   const char *long_desc,
  						   char **valueAddr,
  						   const char *bootValue,
  						   GucContext context,
  						   int flags,
  						   GucStringCheckHook check_hook,
  						   GucStringAssignHook assign_hook,
  						   GucShowHook show_hook)
  {
  	struct config_string *var;
  
  	var = (struct config_string *)
  		init_custom_variable(name, short_desc, long_desc, context, flags,
  							 PGC_STRING, sizeof(struct config_string));
  	var->variable = valueAddr;
  	var->boot_val = bootValue;
  	var->check_hook = check_hook;
  	var->assign_hook = assign_hook;
  	var->show_hook = show_hook;
  	define_custom_variable(&var->gen);
  }
  
  void
  DefineCustomEnumVariable(const char *name,
  						 const char *short_desc,
  						 const char *long_desc,
  						 int *valueAddr,
  						 int bootValue,
  						 const struct config_enum_entry *options,
  						 GucContext context,
  						 int flags,
  						 GucEnumCheckHook check_hook,
  						 GucEnumAssignHook assign_hook,
  						 GucShowHook show_hook)
  {
  	struct config_enum *var;
  
  	var = (struct config_enum *)
  		init_custom_variable(name, short_desc, long_desc, context, flags,
  							 PGC_ENUM, sizeof(struct config_enum));
  	var->variable = valueAddr;
  	var->boot_val = bootValue;
  	var->reset_val = bootValue;
  	var->options = options;
  	var->check_hook = check_hook;
  	var->assign_hook = assign_hook;
  	var->show_hook = show_hook;
  	define_custom_variable(&var->gen);
  }
  
  void
  EmitWarningsOnPlaceholders(const char *className)
  {
  	int			classLen = strlen(className);
  	int			i;
  
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *var = guc_variables[i];
  
  		if ((var->flags & GUC_CUSTOM_PLACEHOLDER) != 0 &&
  			strncmp(className, var->name, classLen) == 0 &&
  			var->name[classLen] == GUC_QUALIFIER_SEPARATOR)
  		{
  			ereport(WARNING,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("unrecognized configuration parameter \"%s\"",
  							var->name)));
  		}
  	}
  }
  
  
  /*
   * SHOW command
   */
  void
  GetPGVariable(const char *name, DestReceiver *dest)
  {
  	if (guc_name_compare(name, "all") == 0)
  		ShowAllGUCConfig(dest);
  	else
  		ShowGUCConfigOption(name, dest);
  }
  
  TupleDesc
  GetPGVariableResultDesc(const char *name)
  {
  	TupleDesc	tupdesc;
  
  	if (guc_name_compare(name, "all") == 0)
  	{
  		/* need a tuple descriptor representing three TEXT columns */
  		tupdesc = CreateTemplateTupleDesc(3);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "description",
  						   TEXTOID, -1, 0);
  	}
  	else
  	{
  		const char *varname;
  
  		/* Get the canonical spelling of name */
  		(void) GetConfigOptionByName(name, &varname, false);
  
  		/* need a tuple descriptor representing a single TEXT column */
  		tupdesc = CreateTemplateTupleDesc(1);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 1, varname,
  						   TEXTOID, -1, 0);
  	}
  	return tupdesc;
  }
  
  
  /*
   * SHOW command
   */
  static void
  ShowGUCConfigOption(const char *name, DestReceiver *dest)
  {
  	TupOutputState *tstate;
  	TupleDesc	tupdesc;
  	const char *varname;
  	char	   *value;
  
  	/* Get the value and canonical spelling of name */
  	value = GetConfigOptionByName(name, &varname, false);
  
  	/* need a tuple descriptor representing a single TEXT column */
  	tupdesc = CreateTemplateTupleDesc(1);
  	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, varname,
  							  TEXTOID, -1, 0);
  
  	/* prepare for projection of tuples */
  	tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
  
  	/* Send it */
  	do_text_output_oneline(tstate, value);
  
  	end_tup_output(tstate);
  }
  
  /*
   * SHOW ALL command
   */
  static void
  ShowAllGUCConfig(DestReceiver *dest)
  {
  	int			i;
  	TupOutputState *tstate;
  	TupleDesc	tupdesc;
  	Datum		values[3];
  	bool		isnull[3] = {false, false, false};
  
  	/* need a tuple descriptor representing three TEXT columns */
  	tupdesc = CreateTemplateTupleDesc(3);
  	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "name",
  							  TEXTOID, -1, 0);
  	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "setting",
  							  TEXTOID, -1, 0);
  	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 3, "description",
  							  TEXTOID, -1, 0);
  
  	/* prepare for projection of tuples */
  	tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
  
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *conf = guc_variables[i];
  		char	   *setting;
  
  		if ((conf->flags & GUC_NO_SHOW_ALL) ||
  			((conf->flags & GUC_SUPERUSER_ONLY) &&
  			 !is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_SETTINGS)))
  			continue;
  
  		/* assign to the values array */
  		values[0] = PointerGetDatum(cstring_to_text(conf->name));
  
  		setting = _ShowOption(conf, true);
  		if (setting)
  		{
  			values[1] = PointerGetDatum(cstring_to_text(setting));
  			isnull[1] = false;
  		}
  		else
  		{
  			values[1] = PointerGetDatum(NULL);
  			isnull[1] = true;
  		}
  
  		values[2] = PointerGetDatum(cstring_to_text(conf->short_desc));
  
  		/* send it to dest */
  		do_tup_output(tstate, values, isnull);
  
  		/* clean up */
  		pfree(DatumGetPointer(values[0]));
  		if (setting)
  		{
  			pfree(setting);
  			pfree(DatumGetPointer(values[1]));
  		}
  		pfree(DatumGetPointer(values[2]));
  	}
  
  	end_tup_output(tstate);
  }
  
  /*
   * Return an array of modified GUC options to show in EXPLAIN.
   *
   * We only report options related to query planning (marked with GUC_EXPLAIN),
   * with values different from their built-in defaults.
   */
  struct config_generic **
  get_explain_guc_options(int *num)
  {
  	struct config_generic **result;
  
  	*num = 0;
  
  	/*
  	 * While only a fraction of all the GUC variables are marked GUC_EXPLAIN,
  	 * it doesn't seem worth dynamically resizing this array.
  	 */
  	result = palloc(sizeof(struct config_generic *) * num_guc_variables);
  
  	for (int i = 0; i < num_guc_variables; i++)
  	{
  		bool		modified;
  		struct config_generic *conf = guc_variables[i];
  
  		/* return only parameters marked for inclusion in explain */
  		if (!(conf->flags & GUC_EXPLAIN))
  			continue;
  
  		/* return only options visible to the current user */
  		if ((conf->flags & GUC_NO_SHOW_ALL) ||
  			((conf->flags & GUC_SUPERUSER_ONLY) &&
  			 !is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_SETTINGS)))
  			continue;
  
  		/* return only options that are different from their boot values */
  		modified = false;
  
  		switch (conf->vartype)
  		{
  			case PGC_BOOL:
  				{
  					struct config_bool *lconf = (struct config_bool *) conf;
  
  					modified = (lconf->boot_val != *(lconf->variable));
  				}
  				break;
  
  			case PGC_INT:
  				{
  					struct config_int *lconf = (struct config_int *) conf;
  
  					modified = (lconf->boot_val != *(lconf->variable));
  				}
  				break;
  
  			case PGC_REAL:
  				{
  					struct config_real *lconf = (struct config_real *) conf;
  
  					modified = (lconf->boot_val != *(lconf->variable));
  				}
  				break;
  
  			case PGC_STRING:
  				{
  					struct config_string *lconf = (struct config_string *) conf;
  
  					modified = (strcmp(lconf->boot_val, *(lconf->variable)) != 0);
  				}
  				break;
  
  			case PGC_ENUM:
  				{
  					struct config_enum *lconf = (struct config_enum *) conf;
  
  					modified = (lconf->boot_val != *(lconf->variable));
  				}
  				break;
  
  			default:
  				elog(ERROR, "unexpected GUC type: %d", conf->vartype);
  		}
  
  		if (!modified)
  			continue;
  
  		/* OK, report it */
  		result[*num] = conf;
  		*num = *num + 1;
  	}
  
  	return result;
  }
  
  /*
   * Return GUC variable value by name; optionally return canonical form of
   * name.  If the GUC is unset, then throw an error unless missing_ok is true,
   * in which case return NULL.  Return value is palloc'd (but *varname isn't).
   */
  char *
  GetConfigOptionByName(const char *name, const char **varname, bool missing_ok)
  {
  	struct config_generic *record;
  
  	record = find_option(name, false, missing_ok, ERROR);
  	if (record == NULL)
  	{
  		if (varname)
  			*varname = NULL;
  		return NULL;
  	}
  
  	if ((record->flags & GUC_SUPERUSER_ONLY) &&
  		!is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_SETTINGS))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("must be superuser or a member of pg_read_all_settings to examine \"%s\"",
  						name)));
  
  	if (varname)
  		*varname = record->name;
  
  	return _ShowOption(record, true);
  }
  
  /*
   * Return GUC variable value by variable number; optionally return canonical
   * form of name.  Return value is palloc'd.
   */
  void
  GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
  {
  	char		buffer[256];
  	struct config_generic *conf;
  
  	/* check requested variable number valid */
  	Assert((varnum >= 0) && (varnum < num_guc_variables));
  
  	conf = guc_variables[varnum];
  
  	if (noshow)
  	{
  		if ((conf->flags & GUC_NO_SHOW_ALL) ||
  			((conf->flags & GUC_SUPERUSER_ONLY) &&
  			 !is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_SETTINGS)))
  			*noshow = true;
  		else
  			*noshow = false;
  	}
  
  	/* first get the generic attributes */
  
  	/* name */
  	values[0] = conf->name;
  
  	/* setting: use _ShowOption in order to avoid duplicating the logic */
  	values[1] = _ShowOption(conf, false);
  
  	/* unit, if any (NULL is fine) */
  	values[2] = get_config_unit_name(conf->flags);
  
  	/* group */
  	values[3] = _(config_group_names[conf->group]);
  
  	/* short_desc */
  	values[4] = _(conf->short_desc);
  
  	/* extra_desc */
  	values[5] = _(conf->long_desc);
  
  	/* context */
  	values[6] = GucContext_Names[conf->context];
  
  	/* vartype */
  	values[7] = config_type_names[conf->vartype];
  
  	/* source */
  	values[8] = GucSource_Names[conf->source];
  
  	/* now get the type specific attributes */
  	switch (conf->vartype)
  	{
  		case PGC_BOOL:
  			{
  				struct config_bool *lconf = (struct config_bool *) conf;
  
  				/* min_val */
  				values[9] = NULL;
  
  				/* max_val */
  				values[10] = NULL;
  
  				/* enumvals */
  				values[11] = NULL;
  
  				/* boot_val */
  				values[12] = pstrdup(lconf->boot_val ? "on" : "off");
  
  				/* reset_val */
  				values[13] = pstrdup(lconf->reset_val ? "on" : "off");
  			}
  			break;
  
  		case PGC_INT:
  			{
  				struct config_int *lconf = (struct config_int *) conf;
  
  				/* min_val */
  				snprintf(buffer, sizeof(buffer), "%d", lconf->min);
  				values[9] = pstrdup(buffer);
  
  				/* max_val */
  				snprintf(buffer, sizeof(buffer), "%d", lconf->max);
  				values[10] = pstrdup(buffer);
  
  				/* enumvals */
  				values[11] = NULL;
  
  				/* boot_val */
  				snprintf(buffer, sizeof(buffer), "%d", lconf->boot_val);
  				values[12] = pstrdup(buffer);
  
  				/* reset_val */
  				snprintf(buffer, sizeof(buffer), "%d", lconf->reset_val);
  				values[13] = pstrdup(buffer);
  			}
  			break;
  
  		case PGC_REAL:
  			{
  				struct config_real *lconf = (struct config_real *) conf;
  
  				/* min_val */
  				snprintf(buffer, sizeof(buffer), "%g", lconf->min);
  				values[9] = pstrdup(buffer);
  
  				/* max_val */
  				snprintf(buffer, sizeof(buffer), "%g", lconf->max);
  				values[10] = pstrdup(buffer);
  
  				/* enumvals */
  				values[11] = NULL;
  
  				/* boot_val */
  				snprintf(buffer, sizeof(buffer), "%g", lconf->boot_val);
  				values[12] = pstrdup(buffer);
  
  				/* reset_val */
  				snprintf(buffer, sizeof(buffer), "%g", lconf->reset_val);
  				values[13] = pstrdup(buffer);
  			}
  			break;
  
  		case PGC_STRING:
  			{
  				struct config_string *lconf = (struct config_string *) conf;
  
  				/* min_val */
  				values[9] = NULL;
  
  				/* max_val */
  				values[10] = NULL;
  
  				/* enumvals */
  				values[11] = NULL;
  
  				/* boot_val */
  				if (lconf->boot_val == NULL)
  					values[12] = NULL;
  				else
  					values[12] = pstrdup(lconf->boot_val);
  
  				/* reset_val */
  				if (lconf->reset_val == NULL)
  					values[13] = NULL;
  				else
  					values[13] = pstrdup(lconf->reset_val);
  			}
  			break;
  
  		case PGC_ENUM:
  			{
  				struct config_enum *lconf = (struct config_enum *) conf;
  
  				/* min_val */
  				values[9] = NULL;
  
  				/* max_val */
  				values[10] = NULL;
  
  				/* enumvals */
  
  				/*
  				 * NOTE! enumvals with double quotes in them are not
  				 * supported!
  				 */
  				values[11] = config_enum_get_options((struct config_enum *) conf,
  													 "{\"", "\"}", "\",\"");
  
  				/* boot_val */
  				values[12] = pstrdup(config_enum_lookup_by_value(lconf,
  																 lconf->boot_val));
  
  				/* reset_val */
  				values[13] = pstrdup(config_enum_lookup_by_value(lconf,
  																 lconf->reset_val));
  			}
  			break;
  
  		default:
  			{
  				/*
  				 * should never get here, but in case we do, set 'em to NULL
  				 */
  
  				/* min_val */
  				values[9] = NULL;
  
  				/* max_val */
  				values[10] = NULL;
  
  				/* enumvals */
  				values[11] = NULL;
  
  				/* boot_val */
  				values[12] = NULL;
  
  				/* reset_val */
  				values[13] = NULL;
  			}
  			break;
  	}
  
  	/*
  	 * If the setting came from a config file, set the source location. For
  	 * security reasons, we don't show source file/line number for
  	 * insufficiently-privileged users.
  	 */
  	if (conf->source == PGC_S_FILE &&
  		is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_SETTINGS))
  	{
  		values[14] = conf->sourcefile;
  		snprintf(buffer, sizeof(buffer), "%d", conf->sourceline);
  		values[15] = pstrdup(buffer);
  	}
  	else
  	{
  		values[14] = NULL;
  		values[15] = NULL;
  	}
  
  	values[16] = (conf->status & GUC_PENDING_RESTART) ? "t" : "f";
  }
  
  /*
   * Return the total number of GUC variables
   */
  int
  GetNumConfigOptions(void)
  {
  	return num_guc_variables;
  }
  
  /*
   * show_config_by_name - equiv to SHOW X command but implemented as
   * a function.
   */
  Datum
  show_config_by_name(PG_FUNCTION_ARGS)
  {
  	char	   *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
  	char	   *varval;
  
  	/* Get the value */
  	varval = GetConfigOptionByName(varname, NULL, false);
  
  	/* Convert to text */
  	PG_RETURN_TEXT_P(cstring_to_text(varval));
  }
  
  /*
   * show_config_by_name_missing_ok - equiv to SHOW X command but implemented as
   * a function.  If X does not exist, suppress the error and just return NULL
   * if missing_ok is true.
   */
  Datum
  show_config_by_name_missing_ok(PG_FUNCTION_ARGS)
  {
  	char	   *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
  	bool		missing_ok = PG_GETARG_BOOL(1);
  	char	   *varval;
  
  	/* Get the value */
  	varval = GetConfigOptionByName(varname, NULL, missing_ok);
  
  	/* return NULL if no such variable */
  	if (varval == NULL)
  		PG_RETURN_NULL();
  
  	/* Convert to text */
  	PG_RETURN_TEXT_P(cstring_to_text(varval));
  }
  
  /*
   * show_all_settings - equiv to SHOW ALL command but implemented as
   * a Table Function.
   */
  #define NUM_PG_SETTINGS_ATTS	17
  
  Datum
  show_all_settings(PG_FUNCTION_ARGS)
  {
  	FuncCallContext *funcctx;
  	TupleDesc	tupdesc;
  	int			call_cntr;
  	int			max_calls;
  	AttInMetadata *attinmeta;
  	MemoryContext oldcontext;
  
  	/* stuff done only on the first call of the function */
  	if (SRF_IS_FIRSTCALL())
  	{
  		/* create a function context for cross-call persistence */
  		funcctx = SRF_FIRSTCALL_INIT();
  
  		/*
  		 * switch to memory context appropriate for multiple function calls
  		 */
  		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
  
  		/*
  		 * need a tuple descriptor representing NUM_PG_SETTINGS_ATTS columns
  		 * of the appropriate types
  		 */
  		tupdesc = CreateTemplateTupleDesc(NUM_PG_SETTINGS_ATTS);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "unit",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 4, "category",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 5, "short_desc",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 6, "extra_desc",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 7, "context",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 8, "vartype",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 9, "source",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 10, "min_val",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 11, "max_val",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 12, "enumvals",
  						   TEXTARRAYOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 13, "boot_val",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 14, "reset_val",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 15, "sourcefile",
  						   TEXTOID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 16, "sourceline",
  						   INT4OID, -1, 0);
  		TupleDescInitEntry(tupdesc, (AttrNumber) 17, "pending_restart",
  						   BOOLOID, -1, 0);
  
  		/*
  		 * Generate attribute metadata needed later to produce tuples from raw
  		 * C strings
  		 */
  		attinmeta = TupleDescGetAttInMetadata(tupdesc);
  		funcctx->attinmeta = attinmeta;
  
  		/* total number of tuples to be returned */
  		funcctx->max_calls = GetNumConfigOptions();
  
  		MemoryContextSwitchTo(oldcontext);
  	}
  
  	/* stuff done on every call of the function */
  	funcctx = SRF_PERCALL_SETUP();
  
  	call_cntr = funcctx->call_cntr;
  	max_calls = funcctx->max_calls;
  	attinmeta = funcctx->attinmeta;
  
  	if (call_cntr < max_calls)	/* do when there is more left to send */
  	{
  		char	   *values[NUM_PG_SETTINGS_ATTS];
  		bool		noshow;
  		HeapTuple	tuple;
  		Datum		result;
  
  		/*
  		 * Get the next visible GUC variable name and value
  		 */
  		do
  		{
  			GetConfigOptionByNum(call_cntr, (const char **) values, &noshow);
  			if (noshow)
  			{
  				/* bump the counter and get the next config setting */
  				call_cntr = ++funcctx->call_cntr;
  
  				/* make sure we haven't gone too far now */
  				if (call_cntr >= max_calls)
  					SRF_RETURN_DONE(funcctx);
  			}
  		} while (noshow);
  
  		/* build a tuple */
  		tuple = BuildTupleFromCStrings(attinmeta, values);
  
  		/* make the tuple into a datum */
  		result = HeapTupleGetDatum(tuple);
  
  		SRF_RETURN_NEXT(funcctx, result);
  	}
  	else
  	{
  		/* do when there is no more left */
  		SRF_RETURN_DONE(funcctx);
  	}
  }
  
  /*
   * show_all_file_settings
   *
   * Returns a table of all parameter settings in all configuration files
   * which includes the config file pathname, the line number, a sequence number
   * indicating the order in which the settings were encountered, the parameter
   * name and value, a bool showing if the value could be applied, and possibly
   * an associated error message.  (For problems such as syntax errors, the
   * parameter name/value might be NULL.)
   *
   * Note: no filtering is done here, instead we depend on the GRANT system
   * to prevent unprivileged users from accessing this function or the view
   * built on top of it.
   */
  Datum
  show_all_file_settings(PG_FUNCTION_ARGS)
  {
  #define NUM_PG_FILE_SETTINGS_ATTS 7
  	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
  	TupleDesc	tupdesc;
  	Tuplestorestate *tupstore;
  	ConfigVariable *conf;
  	int			seqno;
  	MemoryContext per_query_ctx;
  	MemoryContext oldcontext;
  
  	/* Check to see if caller supports us returning a tuplestore */
  	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("set-valued function called in context that cannot accept a set")));
  	if (!(rsinfo->allowedModes & SFRM_Materialize))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("materialize mode required, but it is not allowed in this context")));
  
  	/* Scan the config files using current context as workspace */
  	conf = ProcessConfigFileInternal(PGC_SIGHUP, false, DEBUG3);
  
  	/* Switch into long-lived context to construct returned data structures */
  	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
  	oldcontext = MemoryContextSwitchTo(per_query_ctx);
  
  	/* Build a tuple descriptor for our result type */
  	tupdesc = CreateTemplateTupleDesc(NUM_PG_FILE_SETTINGS_ATTS);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "sourcefile",
  					   TEXTOID, -1, 0);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "sourceline",
  					   INT4OID, -1, 0);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "seqno",
  					   INT4OID, -1, 0);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "name",
  					   TEXTOID, -1, 0);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "setting",
  					   TEXTOID, -1, 0);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "applied",
  					   BOOLOID, -1, 0);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "error",
  					   TEXTOID, -1, 0);
  
  	/* Build a tuplestore to return our results in */
  	tupstore = tuplestore_begin_heap(true, false, work_mem);
  	rsinfo->returnMode = SFRM_Materialize;
  	rsinfo->setResult = tupstore;
  	rsinfo->setDesc = tupdesc;
  
  	/* The rest can be done in short-lived context */
  	MemoryContextSwitchTo(oldcontext);
  
  	/* Process the results and create a tuplestore */
  	for (seqno = 1; conf != NULL; conf = conf->next, seqno++)
  	{
  		Datum		values[NUM_PG_FILE_SETTINGS_ATTS];
  		bool		nulls[NUM_PG_FILE_SETTINGS_ATTS];
  
  		memset(values, 0, sizeof(values));
  		memset(nulls, 0, sizeof(nulls));
  
  		/* sourcefile */
  		if (conf->filename)
  			values[0] = PointerGetDatum(cstring_to_text(conf->filename));
  		else
  			nulls[0] = true;
  
  		/* sourceline (not meaningful if no sourcefile) */
  		if (conf->filename)
  			values[1] = Int32GetDatum(conf->sourceline);
  		else
  			nulls[1] = true;
  
  		/* seqno */
  		values[2] = Int32GetDatum(seqno);
  
  		/* name */
  		if (conf->name)
  			values[3] = PointerGetDatum(cstring_to_text(conf->name));
  		else
  			nulls[3] = true;
  
  		/* setting */
  		if (conf->value)
  			values[4] = PointerGetDatum(cstring_to_text(conf->value));
  		else
  			nulls[4] = true;
  
  		/* applied */
  		values[5] = BoolGetDatum(conf->applied);
  
  		/* error */
  		if (conf->errmsg)
  			values[6] = PointerGetDatum(cstring_to_text(conf->errmsg));
  		else
  			nulls[6] = true;
  
  		/* shove row into tuplestore */
  		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
  	}
  
  	tuplestore_donestoring(tupstore);
  
  	return (Datum) 0;
  }
  
  static char *
  _ShowOption(struct config_generic *record, bool use_units)
  {
  	char		buffer[256];
  	const char *val;
  
  	switch (record->vartype)
  	{
  		case PGC_BOOL:
  			{
  				struct config_bool *conf = (struct config_bool *) record;
  
  				if (conf->show_hook)
  					val = conf->show_hook();
  				else
  					val = *conf->variable ? "on" : "off";
  			}
  			break;
  
  		case PGC_INT:
  			{
  				struct config_int *conf = (struct config_int *) record;
  
  				if (conf->show_hook)
  					val = conf->show_hook();
  				else
  				{
  					/*
  					 * Use int64 arithmetic to avoid overflows in units
  					 * conversion.
  					 */
  					int64		result = *conf->variable;
  					const char *unit;
  
  					if (use_units && result > 0 && (record->flags & GUC_UNIT))
  						convert_int_from_base_unit(result,
  												   record->flags & GUC_UNIT,
  												   &result, &unit);
  					else
  						unit = "";
  
  					snprintf(buffer, sizeof(buffer), INT64_FORMAT "%s",
  							 result, unit);
  					val = buffer;
  				}
  			}
  			break;
  
  		case PGC_REAL:
  			{
  				struct config_real *conf = (struct config_real *) record;
  
  				if (conf->show_hook)
  					val = conf->show_hook();
  				else
  				{
  					double		result = *conf->variable;
  					const char *unit;
  
  					if (use_units && result > 0 && (record->flags & GUC_UNIT))
  						convert_real_from_base_unit(result,
  													record->flags & GUC_UNIT,
  													&result, &unit);
  					else
  						unit = "";
  
  					snprintf(buffer, sizeof(buffer), "%g%s",
  							 result, unit);
  					val = buffer;
  				}
  			}
  			break;
  
  		case PGC_STRING:
  			{
  				struct config_string *conf = (struct config_string *) record;
  
  				if (conf->show_hook)
  					val = conf->show_hook();
  				else if (*conf->variable && **conf->variable)
  					val = *conf->variable;
  				else
  					val = "";
  			}
  			break;
  
  		case PGC_ENUM:
  			{
  				struct config_enum *conf = (struct config_enum *) record;
  
  				if (conf->show_hook)
  					val = conf->show_hook();
  				else
  					val = config_enum_lookup_by_value(conf, *conf->variable);
  			}
  			break;
  
  		default:
  			/* just to keep compiler quiet */
  			val = "???";
  			break;
  	}
  
  	return pstrdup(val);
  }
  
  
  #ifdef EXEC_BACKEND
  
  /*
   *	These routines dump out all non-default GUC options into a binary
   *	file that is read by all exec'ed backends.  The format is:
   *
   *		variable name, string, null terminated
   *		variable value, string, null terminated
   *		variable sourcefile, string, null terminated (empty if none)
   *		variable sourceline, integer
   *		variable source, integer
   *		variable scontext, integer
   */
  static void
  write_one_nondefault_variable(FILE *fp, struct config_generic *gconf)
  {
  	if (gconf->source == PGC_S_DEFAULT)
  		return;
  
  	fprintf(fp, "%s", gconf->name);
  	fputc(0, fp);
  
  	switch (gconf->vartype)
  	{
  		case PGC_BOOL:
  			{
  				struct config_bool *conf = (struct config_bool *) gconf;
  
  				if (*conf->variable)
  					fprintf(fp, "true");
  				else
  					fprintf(fp, "false");
  			}
  			break;
  
  		case PGC_INT:
  			{
  				struct config_int *conf = (struct config_int *) gconf;
  
  				fprintf(fp, "%d", *conf->variable);
  			}
  			break;
  
  		case PGC_REAL:
  			{
  				struct config_real *conf = (struct config_real *) gconf;
  
  				fprintf(fp, "%.17g", *conf->variable);
  			}
  			break;
  
  		case PGC_STRING:
  			{
  				struct config_string *conf = (struct config_string *) gconf;
  
  				fprintf(fp, "%s", *conf->variable);
  			}
  			break;
  
  		case PGC_ENUM:
  			{
  				struct config_enum *conf = (struct config_enum *) gconf;
  
  				fprintf(fp, "%s",
  						config_enum_lookup_by_value(conf, *conf->variable));
  			}
  			break;
  	}
  
  	fputc(0, fp);
  
  	if (gconf->sourcefile)
  		fprintf(fp, "%s", gconf->sourcefile);
  	fputc(0, fp);
  
  	fwrite(&gconf->sourceline, 1, sizeof(gconf->sourceline), fp);
  	fwrite(&gconf->source, 1, sizeof(gconf->source), fp);
  	fwrite(&gconf->scontext, 1, sizeof(gconf->scontext), fp);
  }
  
  void
  write_nondefault_variables(GucContext context)
  {
  	int			elevel;
  	FILE	   *fp;
  	int			i;
  
  	Assert(context == PGC_POSTMASTER || context == PGC_SIGHUP);
  
  	elevel = (context == PGC_SIGHUP) ? LOG : ERROR;
  
  	/*
  	 * Open file
  	 */
  	fp = AllocateFile(CONFIG_EXEC_PARAMS_NEW, "w");
  	if (!fp)
  	{
  		ereport(elevel,
  				(errcode_for_file_access(),
  				 errmsg("could not write to file \"%s\": %m",
  						CONFIG_EXEC_PARAMS_NEW)));
  		return;
  	}
  
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		write_one_nondefault_variable(fp, guc_variables[i]);
  	}
  
  	if (FreeFile(fp))
  	{
  		ereport(elevel,
  				(errcode_for_file_access(),
  				 errmsg("could not write to file \"%s\": %m",
  						CONFIG_EXEC_PARAMS_NEW)));
  		return;
  	}
  
  	/*
  	 * Put new file in place.  This could delay on Win32, but we don't hold
  	 * any exclusive locks.
  	 */
  	rename(CONFIG_EXEC_PARAMS_NEW, CONFIG_EXEC_PARAMS);
  }
  
  
  /*
   *	Read string, including null byte from file
   *
   *	Return NULL on EOF and nothing read
   */
  static char *
  read_string_with_null(FILE *fp)
  {
  	int			i = 0,
  				ch,
  				maxlen = 256;
  	char	   *str = NULL;
  
  	do
  	{
  		if ((ch = fgetc(fp)) == EOF)
  		{
  			if (i == 0)
  				return NULL;
  			else
  				elog(FATAL, "invalid format of exec config params file");
  		}
  		if (i == 0)
  			str = guc_malloc(FATAL, maxlen);
  		else if (i == maxlen)
  			str = guc_realloc(FATAL, str, maxlen *= 2);
  		str[i++] = ch;
  	} while (ch != 0);
  
  	return str;
  }
  
  
  /*
   *	This routine loads a previous postmaster dump of its non-default
   *	settings.
   */
  void
  read_nondefault_variables(void)
  {
  	FILE	   *fp;
  	char	   *varname,
  			   *varvalue,
  			   *varsourcefile;
  	int			varsourceline;
  	GucSource	varsource;
  	GucContext	varscontext;
  
  	/*
  	 * Open file
  	 */
  	fp = AllocateFile(CONFIG_EXEC_PARAMS, "r");
  	if (!fp)
  	{
  		/* File not found is fine */
  		if (errno != ENOENT)
  			ereport(FATAL,
  					(errcode_for_file_access(),
  					 errmsg("could not read from file \"%s\": %m",
  							CONFIG_EXEC_PARAMS)));
  		return;
  	}
  
  	for (;;)
  	{
  		struct config_generic *record;
  
  		if ((varname = read_string_with_null(fp)) == NULL)
  			break;
  
  		if ((record = find_option(varname, true, false, FATAL)) == NULL)
  			elog(FATAL, "failed to locate variable \"%s\" in exec config params file", varname);
  
  		if ((varvalue = read_string_with_null(fp)) == NULL)
  			elog(FATAL, "invalid format of exec config params file");
  		if ((varsourcefile = read_string_with_null(fp)) == NULL)
  			elog(FATAL, "invalid format of exec config params file");
  		if (fread(&varsourceline, 1, sizeof(varsourceline), fp) != sizeof(varsourceline))
  			elog(FATAL, "invalid format of exec config params file");
  		if (fread(&varsource, 1, sizeof(varsource), fp) != sizeof(varsource))
  			elog(FATAL, "invalid format of exec config params file");
  		if (fread(&varscontext, 1, sizeof(varscontext), fp) != sizeof(varscontext))
  			elog(FATAL, "invalid format of exec config params file");
  
  		(void) set_config_option(varname, varvalue,
  								 varscontext, varsource,
  								 GUC_ACTION_SET, true, 0, true);
  		if (varsourcefile[0])
  			set_config_sourcefile(varname, varsourcefile, varsourceline);
  
  		free(varname);
  		free(varvalue);
  		free(varsourcefile);
  	}
  
  	FreeFile(fp);
  }
  #endif							/* EXEC_BACKEND */
  
  /*
   * can_skip_gucvar:
   * Decide whether SerializeGUCState can skip sending this GUC variable,
   * or whether RestoreGUCState can skip resetting this GUC to default.
   *
   * It is somewhat magical and fragile that the same test works for both cases.
   * Realize in particular that we are very likely selecting different sets of
   * GUCs on the leader and worker sides!  Be sure you've understood the
   * comments here and in RestoreGUCState thoroughly before changing this.
   */
  static bool
  can_skip_gucvar(struct config_generic *gconf)
  {
  	/*
  	 * We can skip GUCs that are guaranteed to have the same values in leaders
  	 * and workers.  (Note it is critical that the leader and worker have the
  	 * same idea of which GUCs fall into this category.  It's okay to consider
  	 * context and name for this purpose, since those are unchanging
  	 * properties of a GUC.)
  	 *
  	 * PGC_POSTMASTER variables always have the same value in every child of a
  	 * particular postmaster, so the worker will certainly have the right
  	 * value already.  Likewise, PGC_INTERNAL variables are set by special
  	 * mechanisms (if indeed they aren't compile-time constants).  So we may
  	 * always skip these.
  	 *
  	 * Role must be handled specially because its current value can be an
  	 * invalid value (for instance, if someone dropped the role since we set
  	 * it).  So if we tried to serialize it normally, we might get a failure.
  	 * We skip it here, and use another mechanism to ensure the worker has the
  	 * right value.
  	 *
  	 * For all other GUCs, we skip if the GUC has its compiled-in default
  	 * value (i.e., source == PGC_S_DEFAULT).  On the leader side, this means
  	 * we don't send GUCs that have their default values, which typically
  	 * saves lots of work.  On the worker side, this means we don't need to
  	 * reset the GUC to default because it already has that value.  See
  	 * comments in RestoreGUCState for more info.
  	 */
  	return gconf->context == PGC_POSTMASTER ||
  		gconf->context == PGC_INTERNAL || gconf->source == PGC_S_DEFAULT ||
  		strcmp(gconf->name, "role") == 0;
  }
  
  /*
   * estimate_variable_size:
   *		Compute space needed for dumping the given GUC variable.
   *
   * It's OK to overestimate, but not to underestimate.
   */
  static Size
  estimate_variable_size(struct config_generic *gconf)
  {
  	Size		size;
  	Size		valsize = 0;
  
  	/* Skippable GUCs consume zero space. */
  	if (can_skip_gucvar(gconf))
  		return 0;
  
  	/* Name, plus trailing zero byte. */
  	size = strlen(gconf->name) + 1;
  
  	/* Get the maximum display length of the GUC value. */
  	switch (gconf->vartype)
  	{
  		case PGC_BOOL:
  			{
  				valsize = 5;	/* max(strlen('true'), strlen('false')) */
  			}
  			break;
  
  		case PGC_INT:
  			{
  				struct config_int *conf = (struct config_int *) gconf;
  
  				/*
  				 * Instead of getting the exact display length, use max
  				 * length.  Also reduce the max length for typical ranges of
  				 * small values.  Maximum value is 2147483647, i.e. 10 chars.
  				 * Include one byte for sign.
  				 */
  				if (Abs(*conf->variable) < 1000)
  					valsize = 3 + 1;
  				else
  					valsize = 10 + 1;
  			}
  			break;
  
  		case PGC_REAL:
  			{
  				/*
  				 * We are going to print it with %e with REALTYPE_PRECISION
  				 * fractional digits.  Account for sign, leading digit,
  				 * decimal point, and exponent with up to 3 digits.  E.g.
  				 * -3.99329042340000021e+110
  				 */
  				valsize = 1 + 1 + 1 + REALTYPE_PRECISION + 5;
  			}
  			break;
  
  		case PGC_STRING:
  			{
  				struct config_string *conf = (struct config_string *) gconf;
  
  				/*
  				 * If the value is NULL, we transmit it as an empty string.
  				 * Although this is not physically the same value, GUC
  				 * generally treats a NULL the same as empty string.
  				 */
  				if (*conf->variable)
  					valsize = strlen(*conf->variable);
  				else
  					valsize = 0;
  			}
  			break;
  
  		case PGC_ENUM:
  			{
  				struct config_enum *conf = (struct config_enum *) gconf;
  
  				valsize = strlen(config_enum_lookup_by_value(conf, *conf->variable));
  			}
  			break;
  	}
  
  	/* Allow space for terminating zero-byte for value */
  	size = add_size(size, valsize + 1);
  
  	if (gconf->sourcefile)
  		size = add_size(size, strlen(gconf->sourcefile));
  
  	/* Allow space for terminating zero-byte for sourcefile */
  	size = add_size(size, 1);
  
  	/* Include line whenever file is nonempty. */
  	if (gconf->sourcefile && gconf->sourcefile[0])
  		size = add_size(size, sizeof(gconf->sourceline));
  
  	size = add_size(size, sizeof(gconf->source));
  	size = add_size(size, sizeof(gconf->scontext));
  
  	return size;
  }
  
  /*
   * EstimateGUCStateSpace:
   * Returns the size needed to store the GUC state for the current process
   */
  Size
  EstimateGUCStateSpace(void)
  {
  	Size		size;
  	int			i;
  
  	/* Add space reqd for saving the data size of the guc state */
  	size = sizeof(Size);
  
  	/* Add up the space needed for each GUC variable */
  	for (i = 0; i < num_guc_variables; i++)
  		size = add_size(size,
  						estimate_variable_size(guc_variables[i]));
  
  	return size;
  }
  
  /*
   * do_serialize:
   * Copies the formatted string into the destination.  Moves ahead the
   * destination pointer, and decrements the maxbytes by that many bytes. If
   * maxbytes is not sufficient to copy the string, error out.
   */
  static void
  do_serialize(char **destptr, Size *maxbytes, const char *fmt,...)
  {
  	va_list		vargs;
  	int			n;
  
  	if (*maxbytes <= 0)
  		elog(ERROR, "not enough space to serialize GUC state");
  
  	va_start(vargs, fmt);
  	n = vsnprintf(*destptr, *maxbytes, fmt, vargs);
  	va_end(vargs);
  
  	if (n < 0)
  	{
  		/* Shouldn't happen. Better show errno description. */
  		elog(ERROR, "vsnprintf failed: %m with format string \"%s\"", fmt);
  	}
  	if (n >= *maxbytes)
  	{
  		/* This shouldn't happen either, really. */
  		elog(ERROR, "not enough space to serialize GUC state");
  	}
  
  	/* Shift the destptr ahead of the null terminator */
  	*destptr += n + 1;
  	*maxbytes -= n + 1;
  }
  
  /* Binary copy version of do_serialize() */
  static void
  do_serialize_binary(char **destptr, Size *maxbytes, void *val, Size valsize)
  {
  	if (valsize > *maxbytes)
  		elog(ERROR, "not enough space to serialize GUC state");
  
  	memcpy(*destptr, val, valsize);
  	*destptr += valsize;
  	*maxbytes -= valsize;
  }
  
  /*
   * serialize_variable:
   * Dumps name, value and other information of a GUC variable into destptr.
   */
  static void
  serialize_variable(char **destptr, Size *maxbytes,
  				   struct config_generic *gconf)
  {
  	/* Ignore skippable GUCs. */
  	if (can_skip_gucvar(gconf))
  		return;
  
  	do_serialize(destptr, maxbytes, "%s", gconf->name);
  
  	switch (gconf->vartype)
  	{
  		case PGC_BOOL:
  			{
  				struct config_bool *conf = (struct config_bool *) gconf;
  
  				do_serialize(destptr, maxbytes,
  							 (*conf->variable ? "true" : "false"));
  			}
  			break;
  
  		case PGC_INT:
  			{
  				struct config_int *conf = (struct config_int *) gconf;
  
  				do_serialize(destptr, maxbytes, "%d", *conf->variable);
  			}
  			break;
  
  		case PGC_REAL:
  			{
  				struct config_real *conf = (struct config_real *) gconf;
  
  				do_serialize(destptr, maxbytes, "%.*e",
  							 REALTYPE_PRECISION, *conf->variable);
  			}
  			break;
  
  		case PGC_STRING:
  			{
  				struct config_string *conf = (struct config_string *) gconf;
  
  				/* NULL becomes empty string, see estimate_variable_size() */
  				do_serialize(destptr, maxbytes, "%s",
  							 *conf->variable ? *conf->variable : "");
  			}
  			break;
  
  		case PGC_ENUM:
  			{
  				struct config_enum *conf = (struct config_enum *) gconf;
  
  				do_serialize(destptr, maxbytes, "%s",
  							 config_enum_lookup_by_value(conf, *conf->variable));
  			}
  			break;
  	}
  
  	do_serialize(destptr, maxbytes, "%s",
  				 (gconf->sourcefile ? gconf->sourcefile : ""));
  
  	if (gconf->sourcefile && gconf->sourcefile[0])
  		do_serialize_binary(destptr, maxbytes, &gconf->sourceline,
  							sizeof(gconf->sourceline));
  
  	do_serialize_binary(destptr, maxbytes, &gconf->source,
  						sizeof(gconf->source));
  	do_serialize_binary(destptr, maxbytes, &gconf->scontext,
  						sizeof(gconf->scontext));
  }
  
  /*
   * SerializeGUCState:
   * Dumps the complete GUC state onto the memory location at start_address.
   */
  void
  SerializeGUCState(Size maxsize, char *start_address)
  {
  	char	   *curptr;
  	Size		actual_size;
  	Size		bytes_left;
  	int			i;
  
  	/* Reserve space for saving the actual size of the guc state */
  	Assert(maxsize > sizeof(actual_size));
  	curptr = start_address + sizeof(actual_size);
  	bytes_left = maxsize - sizeof(actual_size);
  
  	for (i = 0; i < num_guc_variables; i++)
  		serialize_variable(&curptr, &bytes_left, guc_variables[i]);
  
  	/* Store actual size without assuming alignment of start_address. */
  	actual_size = maxsize - bytes_left - sizeof(actual_size);
  	memcpy(start_address, &actual_size, sizeof(actual_size));
  }
  
  /*
   * read_gucstate:
   * Actually it does not read anything, just returns the srcptr. But it does
   * move the srcptr past the terminating zero byte, so that the caller is ready
   * to read the next string.
   */
  static char *
  read_gucstate(char **srcptr, char *srcend)
  {
  	char	   *retptr = *srcptr;
  	char	   *ptr;
  
  	if (*srcptr >= srcend)
  		elog(ERROR, "incomplete GUC state");
  
  	/* The string variables are all null terminated */
  	for (ptr = *srcptr; ptr < srcend && *ptr != '\0'; ptr++)
  		;
  
  	if (ptr >= srcend)
  		elog(ERROR, "could not find null terminator in GUC state");
  
  	/* Set the new position to the byte following the terminating NUL */
  	*srcptr = ptr + 1;
  
  	return retptr;
  }
  
  /* Binary read version of read_gucstate(). Copies into dest */
  static void
  read_gucstate_binary(char **srcptr, char *srcend, void *dest, Size size)
  {
  	if (*srcptr + size > srcend)
  		elog(ERROR, "incomplete GUC state");
  
  	memcpy(dest, *srcptr, size);
  	*srcptr += size;
  }
  
  /*
   * Callback used to add a context message when reporting errors that occur
   * while trying to restore GUCs in parallel workers.
   */
  static void
  guc_restore_error_context_callback(void *arg)
  {
  	char	  **error_context_name_and_value = (char **) arg;
  
  	if (error_context_name_and_value)
  		errcontext("while setting parameter \"%s\" to \"%s\"",
  				   error_context_name_and_value[0],
  				   error_context_name_and_value[1]);
  }
  
  /*
   * RestoreGUCState:
   * Reads the GUC state at the specified address and sets this process's
   * GUCs to match.
   *
   * Note that this provides the worker with only a very shallow view of the
   * leader's GUC state: we'll know about the currently active values, but not
   * about stacked or reset values.  That's fine since the worker is just
   * executing one part of a query, within which the active values won't change
   * and the stacked values are invisible.
   */
  void
  RestoreGUCState(void *gucstate)
  {
  	char	   *varname,
  			   *varvalue,
  			   *varsourcefile;
  	int			varsourceline;
  	GucSource	varsource;
  	GucContext	varscontext;
  	char	   *srcptr = (char *) gucstate;
  	char	   *srcend;
  	Size		len;
  	int			i;
  	ErrorContextCallback error_context_callback;
  
  	/*
  	 * First, ensure that all potentially-shippable GUCs are reset to their
  	 * default values.  We must not touch those GUCs that the leader will
  	 * never ship, while there is no need to touch those that are shippable
  	 * but already have their default values.  Thus, this ends up being the
  	 * same test that SerializeGUCState uses, even though the sets of
  	 * variables involved may well be different since the leader's set of
  	 * variables-not-at-default-values can differ from the set that are
  	 * not-default in this freshly started worker.
  	 *
  	 * Once we have set all the potentially-shippable GUCs to default values,
  	 * restoring the GUCs that the leader sent (because they had non-default
  	 * values over there) leads us to exactly the set of GUC values that the
  	 * leader has.  This is true even though the worker may have initially
  	 * absorbed postgresql.conf settings that the leader hasn't yet seen, or
  	 * ALTER USER/DATABASE SET settings that were established after the leader
  	 * started.
  	 *
  	 * Note that ensuring all the potential target GUCs are at PGC_S_DEFAULT
  	 * also ensures that set_config_option won't refuse to set them because of
  	 * source-priority comparisons.
  	 */
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *gconf = guc_variables[i];
  
  		/* Do nothing if non-shippable or if already at PGC_S_DEFAULT. */
  		if (can_skip_gucvar(gconf))
  			continue;
  
  		/*
  		 * We can use InitializeOneGUCOption to reset the GUC to default, but
  		 * first we must free any existing subsidiary data to avoid leaking
  		 * memory.  The stack must be empty, but we have to clean up all other
  		 * fields.  Beware that there might be duplicate value or "extra"
  		 * pointers.
  		 */
  		Assert(gconf->stack == NULL);
  		if (gconf->extra)
  			free(gconf->extra);
  		if (gconf->last_reported)	/* probably can't happen */
  			free(gconf->last_reported);
  		if (gconf->sourcefile)
  			free(gconf->sourcefile);
  		switch (gconf->vartype)
  		{
  			case PGC_BOOL:
  				{
  					struct config_bool *conf = (struct config_bool *) gconf;
  
  					if (conf->reset_extra && conf->reset_extra != gconf->extra)
  						free(conf->reset_extra);
  					break;
  				}
  			case PGC_INT:
  				{
  					struct config_int *conf = (struct config_int *) gconf;
  
  					if (conf->reset_extra && conf->reset_extra != gconf->extra)
  						free(conf->reset_extra);
  					break;
  				}
  			case PGC_REAL:
  				{
  					struct config_real *conf = (struct config_real *) gconf;
  
  					if (conf->reset_extra && conf->reset_extra != gconf->extra)
  						free(conf->reset_extra);
  					break;
  				}
  			case PGC_STRING:
  				{
  					struct config_string *conf = (struct config_string *) gconf;
  
  					if (*conf->variable)
  						free(*conf->variable);
  					if (conf->reset_val && conf->reset_val != *conf->variable)
  						free(conf->reset_val);
  					if (conf->reset_extra && conf->reset_extra != gconf->extra)
  						free(conf->reset_extra);
  					break;
  				}
  			case PGC_ENUM:
  				{
  					struct config_enum *conf = (struct config_enum *) gconf;
  
  					if (conf->reset_extra && conf->reset_extra != gconf->extra)
  						free(conf->reset_extra);
  					break;
  				}
  		}
  		/* Now we can reset the struct to PGS_S_DEFAULT state. */
  		InitializeOneGUCOption(gconf);
  	}
  
  	/* First item is the length of the subsequent data */
  	memcpy(&len, gucstate, sizeof(len));
  
  	srcptr += sizeof(len);
  	srcend = srcptr + len;
  
  	/* If the GUC value check fails, we want errors to show useful context. */
  	error_context_callback.callback = guc_restore_error_context_callback;
  	error_context_callback.previous = error_context_stack;
  	error_context_callback.arg = NULL;
  	error_context_stack = &error_context_callback;
  
  	/* Restore all the listed GUCs. */
  	while (srcptr < srcend)
  	{
  		int			result;
  		char	   *error_context_name_and_value[2];
  
  		varname = read_gucstate(&srcptr, srcend);
  		varvalue = read_gucstate(&srcptr, srcend);
  		varsourcefile = read_gucstate(&srcptr, srcend);
  		if (varsourcefile[0])
  			read_gucstate_binary(&srcptr, srcend,
  								 &varsourceline, sizeof(varsourceline));
  		else
  			varsourceline = 0;
  		read_gucstate_binary(&srcptr, srcend,
  							 &varsource, sizeof(varsource));
  		read_gucstate_binary(&srcptr, srcend,
  							 &varscontext, sizeof(varscontext));
  
  		error_context_name_and_value[0] = varname;
  		error_context_name_and_value[1] = varvalue;
  		error_context_callback.arg = &error_context_name_and_value[0];
  		result = set_config_option(varname, varvalue, varscontext, varsource,
  								   GUC_ACTION_SET, true, ERROR, true);
  		if (result <= 0)
  			ereport(ERROR,
  					(errcode(ERRCODE_INTERNAL_ERROR),
  					 errmsg("parameter \"%s\" could not be set", varname)));
  		if (varsourcefile[0])
  			set_config_sourcefile(varname, varsourcefile, varsourceline);
  		error_context_callback.arg = NULL;
  	}
  
  	error_context_stack = error_context_callback.previous;
  }
  
  /*
   * A little "long argument" simulation, although not quite GNU
   * compliant. Takes a string of the form "some-option=some value" and
   * returns name = "some_option" and value = "some value" in malloc'ed
   * storage. Note that '-' is converted to '_' in the option name. If
   * there is no '=' in the input string then value will be NULL.
   */
  void
  ParseLongOption(const char *string, char **name, char **value)
  {
  	size_t		equal_pos;
  	char	   *cp;
  
  	AssertArg(string);
  	AssertArg(name);
  	AssertArg(value);
  
  	equal_pos = strcspn(string, "=");
  
  	if (string[equal_pos] == '=')
  	{
  		*name = guc_malloc(FATAL, equal_pos + 1);
  		strlcpy(*name, string, equal_pos + 1);
  
  		*value = guc_strdup(FATAL, &string[equal_pos + 1]);
  	}
  	else
  	{
  		/* no equal sign in string */
  		*name = guc_strdup(FATAL, string);
  		*value = NULL;
  	}
  
  	for (cp = *name; *cp; cp++)
  		if (*cp == '-')
  			*cp = '_';
  }
  
  
  /*
   * Handle options fetched from pg_db_role_setting.setconfig,
   * pg_proc.proconfig, etc.  Caller must specify proper context/source/action.
   *
   * The array parameter must be an array of TEXT (it must not be NULL).
   */
  void
  ProcessGUCArray(ArrayType *array,
  				GucContext context, GucSource source, GucAction action)
  {
  	int			i;
  
  	Assert(array != NULL);
  	Assert(ARR_ELEMTYPE(array) == TEXTOID);
  	Assert(ARR_NDIM(array) == 1);
  	Assert(ARR_LBOUND(array)[0] == 1);
  
  	for (i = 1; i <= ARR_DIMS(array)[0]; i++)
  	{
  		Datum		d;
  		bool		isnull;
  		char	   *s;
  		char	   *name;
  		char	   *value;
  		char	   *namecopy;
  		char	   *valuecopy;
  
  		d = array_ref(array, 1, &i,
  					  -1 /* varlenarray */ ,
  					  -1 /* TEXT's typlen */ ,
  					  false /* TEXT's typbyval */ ,
  					  TYPALIGN_INT /* TEXT's typalign */ ,
  					  &isnull);
  
  		if (isnull)
  			continue;
  
  		s = TextDatumGetCString(d);
  
  		ParseLongOption(s, &name, &value);
  		if (!value)
  		{
  			ereport(WARNING,
  					(errcode(ERRCODE_SYNTAX_ERROR),
  					 errmsg("could not parse setting for parameter \"%s\"",
  							name)));
  			free(name);
  			continue;
  		}
  
  		/* free malloc'd strings immediately to avoid leak upon error */
  		namecopy = pstrdup(name);
  		free(name);
  		valuecopy = pstrdup(value);
  		free(value);
  
  		(void) set_config_option(namecopy, valuecopy,
  								 context, source,
  								 action, true, 0, false);
  
  		pfree(namecopy);
  		pfree(valuecopy);
  		pfree(s);
  	}
  }
  
  
  /*
   * Add an entry to an option array.  The array parameter may be NULL
   * to indicate the current table entry is NULL.
   */
  ArrayType *
  GUCArrayAdd(ArrayType *array, const char *name, const char *value)
  {
  	struct config_generic *record;
  	Datum		datum;
  	char	   *newval;
  	ArrayType  *a;
  
  	Assert(name);
  	Assert(value);
  
  	/* test if the option is valid and we're allowed to set it */
  	(void) validate_option_array_item(name, value, false);
  
  	/* normalize name (converts obsolete GUC names to modern spellings) */
  	record = find_option(name, false, true, WARNING);
  	if (record)
  		name = record->name;
  
  	/* build new item for array */
  	newval = psprintf("%s=%s", name, value);
  	datum = CStringGetTextDatum(newval);
  
  	if (array)
  	{
  		int			index;
  		bool		isnull;
  		int			i;
  
  		Assert(ARR_ELEMTYPE(array) == TEXTOID);
  		Assert(ARR_NDIM(array) == 1);
  		Assert(ARR_LBOUND(array)[0] == 1);
  
  		index = ARR_DIMS(array)[0] + 1; /* add after end */
  
  		for (i = 1; i <= ARR_DIMS(array)[0]; i++)
  		{
  			Datum		d;
  			char	   *current;
  
  			d = array_ref(array, 1, &i,
  						  -1 /* varlenarray */ ,
  						  -1 /* TEXT's typlen */ ,
  						  false /* TEXT's typbyval */ ,
  						  TYPALIGN_INT /* TEXT's typalign */ ,
  						  &isnull);
  			if (isnull)
  				continue;
  			current = TextDatumGetCString(d);
  
  			/* check for match up through and including '=' */
  			if (strncmp(current, newval, strlen(name) + 1) == 0)
  			{
  				index = i;
  				break;
  			}
  		}
  
  		a = array_set(array, 1, &index,
  					  datum,
  					  false,
  					  -1 /* varlena array */ ,
  					  -1 /* TEXT's typlen */ ,
  					  false /* TEXT's typbyval */ ,
  					  TYPALIGN_INT /* TEXT's typalign */ );
  	}
  	else
  		a = construct_array(&datum, 1,
  							TEXTOID,
  							-1, false, TYPALIGN_INT);
  
  	return a;
  }
  
  
  /*
   * Delete an entry from an option array.  The array parameter may be NULL
   * to indicate the current table entry is NULL.  Also, if the return value
   * is NULL then a null should be stored.
   */
  ArrayType *
  GUCArrayDelete(ArrayType *array, const char *name)
  {
  	struct config_generic *record;
  	ArrayType  *newarray;
  	int			i;
  	int			index;
  
  	Assert(name);
  
  	/* test if the option is valid and we're allowed to set it */
  	(void) validate_option_array_item(name, NULL, false);
  
  	/* normalize name (converts obsolete GUC names to modern spellings) */
  	record = find_option(name, false, true, WARNING);
  	if (record)
  		name = record->name;
  
  	/* if array is currently null, then surely nothing to delete */
  	if (!array)
  		return NULL;
  
  	newarray = NULL;
  	index = 1;
  
  	for (i = 1; i <= ARR_DIMS(array)[0]; i++)
  	{
  		Datum		d;
  		char	   *val;
  		bool		isnull;
  
  		d = array_ref(array, 1, &i,
  					  -1 /* varlenarray */ ,
  					  -1 /* TEXT's typlen */ ,
  					  false /* TEXT's typbyval */ ,
  					  TYPALIGN_INT /* TEXT's typalign */ ,
  					  &isnull);
  		if (isnull)
  			continue;
  		val = TextDatumGetCString(d);
  
  		/* ignore entry if it's what we want to delete */
  		if (strncmp(val, name, strlen(name)) == 0
  			&& val[strlen(name)] == '=')
  			continue;
  
  		/* else add it to the output array */
  		if (newarray)
  			newarray = array_set(newarray, 1, &index,
  								 d,
  								 false,
  								 -1 /* varlenarray */ ,
  								 -1 /* TEXT's typlen */ ,
  								 false /* TEXT's typbyval */ ,
  								 TYPALIGN_INT /* TEXT's typalign */ );
  		else
  			newarray = construct_array(&d, 1,
  									   TEXTOID,
  									   -1, false, TYPALIGN_INT);
  
  		index++;
  	}
  
  	return newarray;
  }
  
  
  /*
   * Given a GUC array, delete all settings from it that our permission
   * level allows: if superuser, delete them all; if regular user, only
   * those that are PGC_USERSET
   */
  ArrayType *
  GUCArrayReset(ArrayType *array)
  {
  	ArrayType  *newarray;
  	int			i;
  	int			index;
  
  	/* if array is currently null, nothing to do */
  	if (!array)
  		return NULL;
  
  	/* if we're superuser, we can delete everything, so just do it */
  	if (superuser())
  		return NULL;
  
  	newarray = NULL;
  	index = 1;
  
  	for (i = 1; i <= ARR_DIMS(array)[0]; i++)
  	{
  		Datum		d;
  		char	   *val;
  		char	   *eqsgn;
  		bool		isnull;
  
  		d = array_ref(array, 1, &i,
  					  -1 /* varlenarray */ ,
  					  -1 /* TEXT's typlen */ ,
  					  false /* TEXT's typbyval */ ,
  					  TYPALIGN_INT /* TEXT's typalign */ ,
  					  &isnull);
  		if (isnull)
  			continue;
  		val = TextDatumGetCString(d);
  
  		eqsgn = strchr(val, '=');
  		*eqsgn = '\0';
  
  		/* skip if we have permission to delete it */
  		if (validate_option_array_item(val, NULL, true))
  			continue;
  
  		/* else add it to the output array */
  		if (newarray)
  			newarray = array_set(newarray, 1, &index,
  								 d,
  								 false,
  								 -1 /* varlenarray */ ,
  								 -1 /* TEXT's typlen */ ,
  								 false /* TEXT's typbyval */ ,
  								 TYPALIGN_INT /* TEXT's typalign */ );
  		else
  			newarray = construct_array(&d, 1,
  									   TEXTOID,
  									   -1, false, TYPALIGN_INT);
  
  		index++;
  		pfree(val);
  	}
  
  	return newarray;
  }
  
  /*
   * Validate a proposed option setting for GUCArrayAdd/Delete/Reset.
   *
   * name is the option name.  value is the proposed value for the Add case,
   * or NULL for the Delete/Reset cases.  If skipIfNoPermissions is true, it's
   * not an error to have no permissions to set the option.
   *
   * Returns true if OK, false if skipIfNoPermissions is true and user does not
   * have permission to change this option (all other error cases result in an
   * error being thrown).
   */
  static bool
  validate_option_array_item(const char *name, const char *value,
  						   bool skipIfNoPermissions)
  
  {
  	struct config_generic *gconf;
  
  	/*
  	 * There are three cases to consider:
  	 *
  	 * name is a known GUC variable.  Check the value normally, check
  	 * permissions normally (i.e., allow if variable is USERSET, or if it's
  	 * SUSET and user is superuser).
  	 *
  	 * name is not known, but exists or can be created as a placeholder (i.e.,
  	 * it has a valid custom name).  We allow this case if you're a superuser,
  	 * otherwise not.  Superusers are assumed to know what they're doing. We
  	 * can't allow it for other users, because when the placeholder is
  	 * resolved it might turn out to be a SUSET variable;
  	 * define_custom_variable assumes we checked that.
  	 *
  	 * name is not known and can't be created as a placeholder.  Throw error,
  	 * unless skipIfNoPermissions is true, in which case return false.
  	 */
  	gconf = find_option(name, true, skipIfNoPermissions, ERROR);
  	if (!gconf)
  	{
  		/* not known, failed to make a placeholder */
  		return false;
  	}
  
  	if (gconf->flags & GUC_CUSTOM_PLACEHOLDER)
  	{
  		/*
  		 * We cannot do any meaningful check on the value, so only permissions
  		 * are useful to check.
  		 */
  		if (superuser())
  			return true;
  		if (skipIfNoPermissions)
  			return false;
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied to set parameter \"%s\"", name)));
  	}
  
  	/* manual permissions check so we can avoid an error being thrown */
  	if (gconf->context == PGC_USERSET)
  		 /* ok */ ;
  	else if (gconf->context == PGC_SUSET && superuser())
  		 /* ok */ ;
  	else if (skipIfNoPermissions)
  		return false;
  	/* if a permissions error should be thrown, let set_config_option do it */
  
  	/* test for permissions and valid option value */
  	(void) set_config_option(name, value,
  							 superuser() ? PGC_SUSET : PGC_USERSET,
  							 PGC_S_TEST, GUC_ACTION_SET, false, 0, false);
  
  	return true;
  }
  
  
  /*
   * Called by check_hooks that want to override the normal
   * ERRCODE_INVALID_PARAMETER_VALUE SQLSTATE for check hook failures.
   *
   * Note that GUC_check_errmsg() etc are just macros that result in a direct
   * assignment to the associated variables.  That is ugly, but forced by the
   * limitations of C's macro mechanisms.
   */
  void
  GUC_check_errcode(int sqlerrcode)
  {
  	GUC_check_errcode_value = sqlerrcode;
  }
  
  
  /*
   * Convenience functions to manage calling a variable's check_hook.
   * These mostly take care of the protocol for letting check hooks supply
   * portions of the error report on failure.
   */
  
  static bool
  call_bool_check_hook(struct config_bool *conf, bool *newval, void **extra,
  					 GucSource source, int elevel)
  {
  	/* Quick success if no hook */
  	if (!conf->check_hook)
  		return true;
  
  	/* Reset variables that might be set by hook */
  	GUC_check_errcode_value = ERRCODE_INVALID_PARAMETER_VALUE;
  	GUC_check_errmsg_string = NULL;
  	GUC_check_errdetail_string = NULL;
  	GUC_check_errhint_string = NULL;
  
  	if (!conf->check_hook(newval, extra, source))
  	{
  		ereport(elevel,
  				(errcode(GUC_check_errcode_value),
  				 GUC_check_errmsg_string ?
  				 errmsg_internal("%s", GUC_check_errmsg_string) :
  				 errmsg("invalid value for parameter \"%s\": %d",
  						conf->gen.name, (int) *newval),
  				 GUC_check_errdetail_string ?
  				 errdetail_internal("%s", GUC_check_errdetail_string) : 0,
  				 GUC_check_errhint_string ?
  				 errhint("%s", GUC_check_errhint_string) : 0));
  		/* Flush any strings created in ErrorContext */
  		FlushErrorState();
  		return false;
  	}
  
  	return true;
  }
  
  static bool
  call_int_check_hook(struct config_int *conf, int *newval, void **extra,
  					GucSource source, int elevel)
  {
  	/* Quick success if no hook */
  	if (!conf->check_hook)
  		return true;
  
  	/* Reset variables that might be set by hook */
  	GUC_check_errcode_value = ERRCODE_INVALID_PARAMETER_VALUE;
  	GUC_check_errmsg_string = NULL;
  	GUC_check_errdetail_string = NULL;
  	GUC_check_errhint_string = NULL;
  
  	if (!conf->check_hook(newval, extra, source))
  	{
  		ereport(elevel,
  				(errcode(GUC_check_errcode_value),
  				 GUC_check_errmsg_string ?
  				 errmsg_internal("%s", GUC_check_errmsg_string) :
  				 errmsg("invalid value for parameter \"%s\": %d",
  						conf->gen.name, *newval),
  				 GUC_check_errdetail_string ?
  				 errdetail_internal("%s", GUC_check_errdetail_string) : 0,
  				 GUC_check_errhint_string ?
  				 errhint("%s", GUC_check_errhint_string) : 0));
  		/* Flush any strings created in ErrorContext */
  		FlushErrorState();
  		return false;
  	}
  
  	return true;
  }
  
  static bool
  call_real_check_hook(struct config_real *conf, double *newval, void **extra,
  					 GucSource source, int elevel)
  {
  	/* Quick success if no hook */
  	if (!conf->check_hook)
  		return true;
  
  	/* Reset variables that might be set by hook */
  	GUC_check_errcode_value = ERRCODE_INVALID_PARAMETER_VALUE;
  	GUC_check_errmsg_string = NULL;
  	GUC_check_errdetail_string = NULL;
  	GUC_check_errhint_string = NULL;
  
  	if (!conf->check_hook(newval, extra, source))
  	{
  		ereport(elevel,
  				(errcode(GUC_check_errcode_value),
  				 GUC_check_errmsg_string ?
  				 errmsg_internal("%s", GUC_check_errmsg_string) :
  				 errmsg("invalid value for parameter \"%s\": %g",
  						conf->gen.name, *newval),
  				 GUC_check_errdetail_string ?
  				 errdetail_internal("%s", GUC_check_errdetail_string) : 0,
  				 GUC_check_errhint_string ?
  				 errhint("%s", GUC_check_errhint_string) : 0));
  		/* Flush any strings created in ErrorContext */
  		FlushErrorState();
  		return false;
  	}
  
  	return true;
  }
  
  static bool
  call_string_check_hook(struct config_string *conf, char **newval, void **extra,
  					   GucSource source, int elevel)
  {
  	volatile bool result = true;
  
  	/* Quick success if no hook */
  	if (!conf->check_hook)
  		return true;
  
  	/*
  	 * If elevel is ERROR, or if the check_hook itself throws an elog
  	 * (undesirable, but not always avoidable), make sure we don't leak the
  	 * already-malloc'd newval string.
  	 */
  	PG_TRY();
  	{
  		/* Reset variables that might be set by hook */
  		GUC_check_errcode_value = ERRCODE_INVALID_PARAMETER_VALUE;
  		GUC_check_errmsg_string = NULL;
  		GUC_check_errdetail_string = NULL;
  		GUC_check_errhint_string = NULL;
  
  		if (!conf->check_hook(newval, extra, source))
  		{
  			ereport(elevel,
  					(errcode(GUC_check_errcode_value),
  					 GUC_check_errmsg_string ?
  					 errmsg_internal("%s", GUC_check_errmsg_string) :
  					 errmsg("invalid value for parameter \"%s\": \"%s\"",
  							conf->gen.name, *newval ? *newval : ""),
  					 GUC_check_errdetail_string ?
  					 errdetail_internal("%s", GUC_check_errdetail_string) : 0,
  					 GUC_check_errhint_string ?
  					 errhint("%s", GUC_check_errhint_string) : 0));
  			/* Flush any strings created in ErrorContext */
  			FlushErrorState();
  			result = false;
  		}
  	}
  	PG_CATCH();
  	{
  		free(*newval);
  		PG_RE_THROW();
  	}
  	PG_END_TRY();
  
  	return result;
  }
  
  static bool
  call_enum_check_hook(struct config_enum *conf, int *newval, void **extra,
  					 GucSource source, int elevel)
  {
  	/* Quick success if no hook */
  	if (!conf->check_hook)
  		return true;
  
  	/* Reset variables that might be set by hook */
  	GUC_check_errcode_value = ERRCODE_INVALID_PARAMETER_VALUE;
  	GUC_check_errmsg_string = NULL;
  	GUC_check_errdetail_string = NULL;
  	GUC_check_errhint_string = NULL;
  
  	if (!conf->check_hook(newval, extra, source))
  	{
  		ereport(elevel,
  				(errcode(GUC_check_errcode_value),
  				 GUC_check_errmsg_string ?
  				 errmsg_internal("%s", GUC_check_errmsg_string) :
  				 errmsg("invalid value for parameter \"%s\": \"%s\"",
  						conf->gen.name,
  						config_enum_lookup_by_value(conf, *newval)),
  				 GUC_check_errdetail_string ?
  				 errdetail_internal("%s", GUC_check_errdetail_string) : 0,
  				 GUC_check_errhint_string ?
  				 errhint("%s", GUC_check_errhint_string) : 0));
  		/* Flush any strings created in ErrorContext */
  		FlushErrorState();
  		return false;
  	}
  
  	return true;
  }
  
  
  /*
   * check_hook, assign_hook and show_hook subroutines
   */
  
  static bool
  check_wal_consistency_checking(char **newval, void **extra, GucSource source)
  {
  	char	   *rawstring;
  	List	   *elemlist;
  	ListCell   *l;
  	bool		newwalconsistency[RM_MAX_ID + 1];
  
  	/* Initialize the array */
  	MemSet(newwalconsistency, 0, (RM_MAX_ID + 1) * sizeof(bool));
  
  	/* Need a modifiable copy of string */
  	rawstring = pstrdup(*newval);
  
  	/* Parse string into list of identifiers */
  	if (!SplitIdentifierString(rawstring, ',', &elemlist))
  	{
  		/* syntax error in list */
  		GUC_check_errdetail("List syntax is invalid.");
  		pfree(rawstring);
  		list_free(elemlist);
  		return false;
  	}
  
  	foreach(l, elemlist)
  	{
  		char	   *tok = (char *) lfirst(l);
  		bool		found = false;
  		RmgrId		rmid;
  
  		/* Check for 'all'. */
  		if (pg_strcasecmp(tok, "all") == 0)
  		{
  			for (rmid = 0; rmid <= RM_MAX_ID; rmid++)
  				if (RmgrTable[rmid].rm_mask != NULL)
  					newwalconsistency[rmid] = true;
  			found = true;
  		}
  		else
  		{
  			/*
  			 * Check if the token matches with any individual resource
  			 * manager.
  			 */
  			for (rmid = 0; rmid <= RM_MAX_ID; rmid++)
  			{
  				if (pg_strcasecmp(tok, RmgrTable[rmid].rm_name) == 0 &&
  					RmgrTable[rmid].rm_mask != NULL)
  				{
  					newwalconsistency[rmid] = true;
  					found = true;
  				}
  			}
  		}
  
  		/* If a valid resource manager is found, check for the next one. */
  		if (!found)
  		{
  			GUC_check_errdetail("Unrecognized key word: \"%s\".", tok);
  			pfree(rawstring);
  			list_free(elemlist);
  			return false;
  		}
  	}
  
  	pfree(rawstring);
  	list_free(elemlist);
  
  	/* assign new value */
  	*extra = guc_malloc(ERROR, (RM_MAX_ID + 1) * sizeof(bool));
  	memcpy(*extra, newwalconsistency, (RM_MAX_ID + 1) * sizeof(bool));
  	return true;
  }
  
  static void
  assign_wal_consistency_checking(const char *newval, void *extra)
  {
  	wal_consistency_checking = (bool *) extra;
  }
  
  static bool
  check_log_destination(char **newval, void **extra, GucSource source)
  {
  	char	   *rawstring;
  	List	   *elemlist;
  	ListCell   *l;
  	int			newlogdest = 0;
  	int		   *myextra;
  
  	/* Need a modifiable copy of string */
  	rawstring = pstrdup(*newval);
  
  	/* Parse string into list of identifiers */
  	if (!SplitIdentifierString(rawstring, ',', &elemlist))
  	{
  		/* syntax error in list */
  		GUC_check_errdetail("List syntax is invalid.");
  		pfree(rawstring);
  		list_free(elemlist);
  		return false;
  	}
  
  	foreach(l, elemlist)
  	{
  		char	   *tok = (char *) lfirst(l);
  
  		if (pg_strcasecmp(tok, "stderr") == 0)
  			newlogdest |= LOG_DESTINATION_STDERR;
  		else if (pg_strcasecmp(tok, "csvlog") == 0)
  			newlogdest |= LOG_DESTINATION_CSVLOG;
  #ifdef HAVE_SYSLOG
  		else if (pg_strcasecmp(tok, "syslog") == 0)
  			newlogdest |= LOG_DESTINATION_SYSLOG;
  #endif
  #ifdef WIN32
  		else if (pg_strcasecmp(tok, "eventlog") == 0)
  			newlogdest |= LOG_DESTINATION_EVENTLOG;
  #endif
  		else
  		{
  			GUC_check_errdetail("Unrecognized key word: \"%s\".", tok);
  			pfree(rawstring);
  			list_free(elemlist);
  			return false;
  		}
  	}
  
  	pfree(rawstring);
  	list_free(elemlist);
  
  	myextra = (int *) guc_malloc(ERROR, sizeof(int));
  	*myextra = newlogdest;
  	*extra = (void *) myextra;
  
  	return true;
  }
  
  static void
  assign_log_destination(const char *newval, void *extra)
  {
  	Log_destination = *((int *) extra);
  }
  
  static void
  assign_syslog_facility(int newval, void *extra)
  {
  #ifdef HAVE_SYSLOG
  	set_syslog_parameters(syslog_ident_str ? syslog_ident_str : "postgres",
  						  newval);
  #endif
  	/* Without syslog support, just ignore it */
  }
  
  static void
  assign_syslog_ident(const char *newval, void *extra)
  {
  #ifdef HAVE_SYSLOG
  	set_syslog_parameters(newval, syslog_facility);
  #endif
  	/* Without syslog support, it will always be set to "none", so ignore */
  }
  
  
  static void
  assign_session_replication_role(int newval, void *extra)
  {
  	/*
  	 * Must flush the plan cache when changing replication role; but don't
  	 * flush unnecessarily.
  	 */
  	if (SessionReplicationRole != newval)
  		ResetPlanCache();
  }
  
  static bool
  check_temp_buffers(int *newval, void **extra, GucSource source)
  {
  	/*
  	 * Once local buffers have been initialized, it's too late to change this.
  	 * However, if this is only a test call, allow it.
  	 */
  	if (source != PGC_S_TEST && NLocBuffer && NLocBuffer != *newval)
  	{
  		GUC_check_errdetail("\"temp_buffers\" cannot be changed after any temporary tables have been accessed in the session.");
  		return false;
  	}
  	return true;
  }
  
  static bool
  check_bonjour(bool *newval, void **extra, GucSource source)
  {
  #ifndef USE_BONJOUR
  	if (*newval)
  	{
  		GUC_check_errmsg("Bonjour is not supported by this build");
  		return false;
  	}
  #endif
  	return true;
  }
  
  static bool
  check_ssl(bool *newval, void **extra, GucSource source)
  {
  #ifndef USE_SSL
  	if (*newval)
  	{
  		GUC_check_errmsg("SSL is not supported by this build");
  		return false;
  	}
  #endif
  	return true;
  }
  
  static bool
  check_stage_log_stats(bool *newval, void **extra, GucSource source)
  {
  	if (*newval && log_statement_stats)
  	{
  		GUC_check_errdetail("Cannot enable parameter when \"log_statement_stats\" is true.");
  		return false;
  	}
  	return true;
  }
  
  static bool
  check_log_stats(bool *newval, void **extra, GucSource source)
  {
  	if (*newval &&
  		(log_parser_stats || log_planner_stats || log_executor_stats))
  	{
  		GUC_check_errdetail("Cannot enable \"log_statement_stats\" when "
  							"\"log_parser_stats\", \"log_planner_stats\", "
  							"or \"log_executor_stats\" is true.");
  		return false;
  	}
  	return true;
  }
  
  static bool
  check_canonical_path(char **newval, void **extra, GucSource source)
  {
  	/*
  	 * Since canonicalize_path never enlarges the string, we can just modify
  	 * newval in-place.  But watch out for NULL, which is the default value
  	 * for external_pid_file.
  	 */
  	if (*newval)
  		canonicalize_path(*newval);
  	return true;
  }
  
  static bool
  check_timezone_abbreviations(char **newval, void **extra, GucSource source)
  {
  	/*
  	 * The boot_val given above for timezone_abbreviations is NULL. When we
  	 * see this we just do nothing.  If this value isn't overridden from the
  	 * config file then pg_timezone_abbrev_initialize() will eventually
  	 * replace it with "Default".  This hack has two purposes: to avoid
  	 * wasting cycles loading values that might soon be overridden from the
  	 * config file, and to avoid trying to read the timezone abbrev files
  	 * during InitializeGUCOptions().  The latter doesn't work in an
  	 * EXEC_BACKEND subprocess because my_exec_path hasn't been set yet and so
  	 * we can't locate PGSHAREDIR.
  	 */
  	if (*newval == NULL)
  	{
  		Assert(source == PGC_S_DEFAULT);
  		return true;
  	}
  
  	/* OK, load the file and produce a malloc'd TimeZoneAbbrevTable */
  	*extra = load_tzoffsets(*newval);
  
  	/* tzparser.c returns NULL on failure, reporting via GUC_check_errmsg */
  	if (!*extra)
  		return false;
  
  	return true;
  }
  
  static void
  assign_timezone_abbreviations(const char *newval, void *extra)
  {
  	/* Do nothing for the boot_val default of NULL */
  	if (!extra)
  		return;
  
  	InstallTimeZoneAbbrevs((TimeZoneAbbrevTable *) extra);
  }
  
  /*
   * pg_timezone_abbrev_initialize --- set default value if not done already
   *
   * This is called after initial loading of postgresql.conf.  If no
   * timezone_abbreviations setting was found therein, select default.
   * If a non-default value is already installed, nothing will happen.
   *
   * This can also be called from ProcessConfigFile to establish the default
   * value after a postgresql.conf entry for it is removed.
   */
  static void
  pg_timezone_abbrev_initialize(void)
  {
  	SetConfigOption("timezone_abbreviations", "Default",
  					PGC_POSTMASTER, PGC_S_DYNAMIC_DEFAULT);
  }
  
  static const char *
  show_archive_command(void)
  {
  	if (XLogArchivingActive())
  		return XLogArchiveCommand;
  	else
  		return "(disabled)";
  }
  
  static void
  assign_tcp_keepalives_idle(int newval, void *extra)
  {
  	/*
  	 * The kernel API provides no way to test a value without setting it; and
  	 * once we set it we might fail to unset it.  So there seems little point
  	 * in fully implementing the check-then-assign GUC API for these
  	 * variables.  Instead we just do the assignment on demand.  pqcomm.c
  	 * reports any problems via ereport(LOG).
  	 *
  	 * This approach means that the GUC value might have little to do with the
  	 * actual kernel value, so we use a show_hook that retrieves the kernel
  	 * value rather than trusting GUC's copy.
  	 */
  	(void) pq_setkeepalivesidle(newval, MyProcPort);
  }
  
  static const char *
  show_tcp_keepalives_idle(void)
  {
  	/* See comments in assign_tcp_keepalives_idle */
  	static char nbuf[16];
  
  	snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivesidle(MyProcPort));
  	return nbuf;
  }
  
  static void
  assign_tcp_keepalives_interval(int newval, void *extra)
  {
  	/* See comments in assign_tcp_keepalives_idle */
  	(void) pq_setkeepalivesinterval(newval, MyProcPort);
  }
  
  static const char *
  show_tcp_keepalives_interval(void)
  {
  	/* See comments in assign_tcp_keepalives_idle */
  	static char nbuf[16];
  
  	snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivesinterval(MyProcPort));
  	return nbuf;
  }
  
  static void
  assign_tcp_keepalives_count(int newval, void *extra)
  {
  	/* See comments in assign_tcp_keepalives_idle */
  	(void) pq_setkeepalivescount(newval, MyProcPort);
  }
  
  static const char *
  show_tcp_keepalives_count(void)
  {
  	/* See comments in assign_tcp_keepalives_idle */
  	static char nbuf[16];
  
  	snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivescount(MyProcPort));
  	return nbuf;
  }
  
  static void
  assign_tcp_user_timeout(int newval, void *extra)
  {
  	/* See comments in assign_tcp_keepalives_idle */
  	(void) pq_settcpusertimeout(newval, MyProcPort);
  }
  
  static const char *
  show_tcp_user_timeout(void)
  {
  	/* See comments in assign_tcp_keepalives_idle */
  	static char nbuf[16];
  
  	snprintf(nbuf, sizeof(nbuf), "%d", pq_gettcpusertimeout(MyProcPort));
  	return nbuf;
  }
  
  static bool
  check_maxconnections(int *newval, void **extra, GucSource source)
  {
  	if (*newval + autovacuum_max_workers + 1 +
  		max_worker_processes + max_wal_senders > MAX_BACKENDS)
  		return false;
  	return true;
  }
  
  static bool
  check_autovacuum_max_workers(int *newval, void **extra, GucSource source)
  {
  	if (MaxConnections + *newval + 1 +
  		max_worker_processes + max_wal_senders > MAX_BACKENDS)
  		return false;
  	return true;
  }
  
  static bool
  check_max_wal_senders(int *newval, void **extra, GucSource source)
  {
  	if (MaxConnections + autovacuum_max_workers + 1 +
  		max_worker_processes + *newval > MAX_BACKENDS)
  		return false;
  	return true;
  }
  
  static bool
  check_autovacuum_work_mem(int *newval, void **extra, GucSource source)
  {
  	/*
  	 * -1 indicates fallback.
  	 *
  	 * If we haven't yet changed the boot_val default of -1, just let it be.
  	 * Autovacuum will look to maintenance_work_mem instead.
  	 */
  	if (*newval == -1)
  		return true;
  
  	/*
  	 * We clamp manually-set values to at least 1MB.  Since
  	 * maintenance_work_mem is always set to at least this value, do the same
  	 * here.
  	 */
  	if (*newval < 1024)
  		*newval = 1024;
  
  	return true;
  }
  
  static bool
  check_max_worker_processes(int *newval, void **extra, GucSource source)
  {
  	if (MaxConnections + autovacuum_max_workers + 1 +
  		*newval + max_wal_senders > MAX_BACKENDS)
  		return false;
  	return true;
  }
  
  static bool
  check_effective_io_concurrency(int *newval, void **extra, GucSource source)
  {
  #ifndef USE_PREFETCH
  	if (*newval != 0)
  	{
  		GUC_check_errdetail("effective_io_concurrency must be set to 0 on platforms that lack posix_fadvise().");
  		return false;
  	}
  #endif							/* USE_PREFETCH */
  	return true;
  }
  
  static bool
  check_maintenance_io_concurrency(int *newval, void **extra, GucSource source)
  {
  #ifndef USE_PREFETCH
  	if (*newval != 0)
  	{
  		GUC_check_errdetail("maintenance_io_concurrency must be set to 0 on platforms that lack posix_fadvise().");
  		return false;
  	}
  #endif							/* USE_PREFETCH */
  	return true;
  }
  
  static bool
  check_huge_page_size(int *newval, void **extra, GucSource source)
  {
  #if !(defined(MAP_HUGE_MASK) && defined(MAP_HUGE_SHIFT))
  	/* Recent enough Linux only, for now.  See GetHugePageSize(). */
  	if (*newval != 0)
  	{
  		GUC_check_errdetail("huge_page_size must be 0 on this platform.");
  		return false;
  	}
  #endif
  	return true;
  }
  
  static bool
  check_client_connection_check_interval(int *newval, void **extra, GucSource source)
  {
  #ifndef POLLRDHUP
  	/* Linux only, for now.  See pq_check_connection(). */
  	if (*newval != 0)
  	{
  		GUC_check_errdetail("client_connection_check_interval must be set to 0 on platforms that lack POLLRDHUP.");
  		return false;
  	}
  #endif
  	return true;
  }
  
  static void
  assign_pgstat_temp_directory(const char *newval, void *extra)
  {
  	/* check_canonical_path already canonicalized newval for us */
  	char	   *dname;
  	char	   *tname;
  	char	   *fname;
  
  	/* directory */
  	dname = guc_malloc(ERROR, strlen(newval) + 1);	/* runtime dir */
  	sprintf(dname, "%s", newval);
  
  	/* global stats */
  	tname = guc_malloc(ERROR, strlen(newval) + 12); /* /global.tmp */
  	sprintf(tname, "%s/global.tmp", newval);
  	fname = guc_malloc(ERROR, strlen(newval) + 13); /* /global.stat */
  	sprintf(fname, "%s/global.stat", newval);
  
  	if (pgstat_stat_directory)
  		free(pgstat_stat_directory);
  	pgstat_stat_directory = dname;
  	if (pgstat_stat_tmpname)
  		free(pgstat_stat_tmpname);
  	pgstat_stat_tmpname = tname;
  	if (pgstat_stat_filename)
  		free(pgstat_stat_filename);
  	pgstat_stat_filename = fname;
  }
  
  static bool
  check_application_name(char **newval, void **extra, GucSource source)
  {
  	/* Only allow clean ASCII chars in the application name */
  	pg_clean_ascii(*newval);
  
  	return true;
  }
  
  static void
  assign_application_name(const char *newval, void *extra)
  {
  	/* Update the pg_stat_activity view */
  	pgstat_report_appname(newval);
  }
  
  static bool
  check_cluster_name(char **newval, void **extra, GucSource source)
  {
  	/* Only allow clean ASCII chars in the cluster name */
  	pg_clean_ascii(*newval);
  
  	return true;
  }
  
  static const char *
  show_unix_socket_permissions(void)
  {
  	static char buf[12];
  
  	snprintf(buf, sizeof(buf), "%04o", Unix_socket_permissions);
  	return buf;
  }
  
  static const char *
  show_log_file_mode(void)
  {
  	static char buf[12];
  
  	snprintf(buf, sizeof(buf), "%04o", Log_file_mode);
  	return buf;
  }
  
  static const char *
  show_data_directory_mode(void)
  {
  	static char buf[12];
  
  	snprintf(buf, sizeof(buf), "%04o", data_directory_mode);
  	return buf;
  }
  
  static const char *
  show_in_hot_standby(void)
  {
  	/*
  	 * We display the actual state based on shared memory, so that this GUC
  	 * reports up-to-date state if examined intra-query.  The underlying
  	 * variable in_hot_standby changes only when we transmit a new value to
  	 * the client.
  	 */
  	return RecoveryInProgress() ? "on" : "off";
  }
  
  /*
   * We split the input string, where commas separate function names
   * and certain whitespace chars are ignored, into a \0-separated (and
   * \0\0-terminated) list of function names.  This formulation allows
   * easy scanning when an error is thrown while avoiding the use of
   * non-reentrant strtok(), as well as keeping the output data in a
   * single palloc() chunk.
   */
  static bool
  check_backtrace_functions(char **newval, void **extra, GucSource source)
  {
  	int			newvallen = strlen(*newval);
  	char	   *someval;
  	int			validlen;
  	int			i;
  	int			j;
  
  	/*
  	 * Allow characters that can be C identifiers and commas as separators, as
  	 * well as some whitespace for readability.
  	 */
  	validlen = strspn(*newval,
  					  "0123456789_"
  					  "abcdefghijklmnopqrstuvwxyz"
  					  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  					  ", \n\t");
  	if (validlen != newvallen)
  	{
  		GUC_check_errdetail("invalid character");
  		return false;
  	}
  
  	if (*newval[0] == '\0')
  	{
  		*extra = NULL;
  		return true;
  	}
  
  	/*
  	 * Allocate space for the output and create the copy.  We could discount
  	 * whitespace chars to save some memory, but it doesn't seem worth the
  	 * trouble.
  	 */
  	someval = guc_malloc(ERROR, newvallen + 1 + 1);
  	for (i = 0, j = 0; i < newvallen; i++)
  	{
  		if ((*newval)[i] == ',')
  			someval[j++] = '\0';	/* next item */
  		else if ((*newval)[i] == ' ' ||
  				 (*newval)[i] == '\n' ||
  				 (*newval)[i] == '\t')
  			;					/* ignore these */
  		else
  			someval[j++] = (*newval)[i];	/* copy anything else */
  	}
  
  	/* two \0s end the setting */
  	someval[j] = '\0';
  	someval[j + 1] = '\0';
  
  	*extra = someval;
  	return true;
  }
  
  static void
  assign_backtrace_functions(const char *newval, void *extra)
  {
  	backtrace_symbol_list = (char *) extra;
  }
  
  static bool
  check_recovery_target_timeline(char **newval, void **extra, GucSource source)
  {
  	RecoveryTargetTimeLineGoal rttg;
  	RecoveryTargetTimeLineGoal *myextra;
  
  	if (strcmp(*newval, "current") == 0)
  		rttg = RECOVERY_TARGET_TIMELINE_CONTROLFILE;
  	else if (strcmp(*newval, "latest") == 0)
  		rttg = RECOVERY_TARGET_TIMELINE_LATEST;
  	else
  	{
  		rttg = RECOVERY_TARGET_TIMELINE_NUMERIC;
  
  		errno = 0;
  		strtoul(*newval, NULL, 0);
  		if (errno == EINVAL || errno == ERANGE)
  		{
  			GUC_check_errdetail("recovery_target_timeline is not a valid number.");
  			return false;
  		}
  	}
  
  	myextra = (RecoveryTargetTimeLineGoal *) guc_malloc(ERROR, sizeof(RecoveryTargetTimeLineGoal));
  	*myextra = rttg;
  	*extra = (void *) myextra;
  
  	return true;
  }
  
  static void
  assign_recovery_target_timeline(const char *newval, void *extra)
  {
  	recoveryTargetTimeLineGoal = *((RecoveryTargetTimeLineGoal *) extra);
  	if (recoveryTargetTimeLineGoal == RECOVERY_TARGET_TIMELINE_NUMERIC)
  		recoveryTargetTLIRequested = (TimeLineID) strtoul(newval, NULL, 0);
  	else
  		recoveryTargetTLIRequested = 0;
  }
  
  /*
   * Recovery target settings: Only one of the several recovery_target* settings
   * may be set.  Setting a second one results in an error.  The global variable
   * recoveryTarget tracks which kind of recovery target was chosen.  Other
   * variables store the actual target value (for example a string or a xid).
   * The assign functions of the parameters check whether a competing parameter
   * was already set.  But we want to allow setting the same parameter multiple
   * times.  We also want to allow unsetting a parameter and setting a different
   * one, so we unset recoveryTarget when the parameter is set to an empty
   * string.
   */
  
  static void
  pg_attribute_noreturn()
  error_multiple_recovery_targets(void)
  {
  	ereport(ERROR,
  			(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  			 errmsg("multiple recovery targets specified"),
  			 errdetail("At most one of recovery_target, recovery_target_lsn, recovery_target_name, recovery_target_time, recovery_target_xid may be set.")));
  }
  
  static bool
  check_recovery_target(char **newval, void **extra, GucSource source)
  {
  	if (strcmp(*newval, "immediate") != 0 && strcmp(*newval, "") != 0)
  	{
  		GUC_check_errdetail("The only allowed value is \"immediate\".");
  		return false;
  	}
  	return true;
  }
  
  static void
  assign_recovery_target(const char *newval, void *extra)
  {
  	if (recoveryTarget != RECOVERY_TARGET_UNSET &&
  		recoveryTarget != RECOVERY_TARGET_IMMEDIATE)
  		error_multiple_recovery_targets();
  
  	if (newval && strcmp(newval, "") != 0)
  		recoveryTarget = RECOVERY_TARGET_IMMEDIATE;
  	else
  		recoveryTarget = RECOVERY_TARGET_UNSET;
  }
  
  static bool
  check_recovery_target_xid(char **newval, void **extra, GucSource source)
  {
  	if (strcmp(*newval, "") != 0)
  	{
  		TransactionId xid;
  		TransactionId *myextra;
  
  		errno = 0;
  		xid = (TransactionId) pg_strtouint64(*newval, NULL, 0);
  		if (errno == EINVAL || errno == ERANGE)
  			return false;
  
  		myextra = (TransactionId *) guc_malloc(ERROR, sizeof(TransactionId));
  		*myextra = xid;
  		*extra = (void *) myextra;
  	}
  	return true;
  }
  
  static void
  assign_recovery_target_xid(const char *newval, void *extra)
  {
  	if (recoveryTarget != RECOVERY_TARGET_UNSET &&
  		recoveryTarget != RECOVERY_TARGET_XID)
  		error_multiple_recovery_targets();
  
  	if (newval && strcmp(newval, "") != 0)
  	{
  		recoveryTarget = RECOVERY_TARGET_XID;
  		recoveryTargetXid = *((TransactionId *) extra);
  	}
  	else
  		recoveryTarget = RECOVERY_TARGET_UNSET;
  }
  
  /*
   * The interpretation of the recovery_target_time string can depend on the
   * time zone setting, so we need to wait until after all GUC processing is
   * done before we can do the final parsing of the string.  This check function
   * only does a parsing pass to catch syntax errors, but we store the string
   * and parse it again when we need to use it.
   */
  static bool
  check_recovery_target_time(char **newval, void **extra, GucSource source)
  {
  	if (strcmp(*newval, "") != 0)
  	{
  		/* reject some special values */
  		if (strcmp(*newval, "now") == 0 ||
  			strcmp(*newval, "today") == 0 ||
  			strcmp(*newval, "tomorrow") == 0 ||
  			strcmp(*newval, "yesterday") == 0)
  		{
  			return false;
  		}
  
  		/*
  		 * parse timestamp value (see also timestamptz_in())
  		 */
  		{
  			char	   *str = *newval;
  			fsec_t		fsec;
  			struct pg_tm tt,
  					   *tm = &tt;
  			int			tz;
  			int			dtype;
  			int			nf;
  			int			dterr;
  			char	   *field[MAXDATEFIELDS];
  			int			ftype[MAXDATEFIELDS];
  			char		workbuf[MAXDATELEN + MAXDATEFIELDS];
  			TimestampTz timestamp;
  
  			dterr = ParseDateTime(str, workbuf, sizeof(workbuf),
  								  field, ftype, MAXDATEFIELDS, &nf);
  			if (dterr == 0)
  				dterr = DecodeDateTime(field, ftype, nf, &dtype, tm, &fsec, &tz);
  			if (dterr != 0)
  				return false;
  			if (dtype != DTK_DATE)
  				return false;
  
  			if (tm2timestamp(tm, fsec, &tz, &timestamp) != 0)
  			{
  				GUC_check_errdetail("timestamp out of range: \"%s\"", str);
  				return false;
  			}
  		}
  	}
  	return true;
  }
  
  static void
  assign_recovery_target_time(const char *newval, void *extra)
  {
  	if (recoveryTarget != RECOVERY_TARGET_UNSET &&
  		recoveryTarget != RECOVERY_TARGET_TIME)
  		error_multiple_recovery_targets();
  
  	if (newval && strcmp(newval, "") != 0)
  		recoveryTarget = RECOVERY_TARGET_TIME;
  	else
  		recoveryTarget = RECOVERY_TARGET_UNSET;
  }
  
  static bool
  check_recovery_target_name(char **newval, void **extra, GucSource source)
  {
  	/* Use the value of newval directly */
  	if (strlen(*newval) >= MAXFNAMELEN)
  	{
  		GUC_check_errdetail("%s is too long (maximum %d characters).",
  							"recovery_target_name", MAXFNAMELEN - 1);
  		return false;
  	}
  	return true;
  }
  
  static void
  assign_recovery_target_name(const char *newval, void *extra)
  {
  	if (recoveryTarget != RECOVERY_TARGET_UNSET &&
  		recoveryTarget != RECOVERY_TARGET_NAME)
  		error_multiple_recovery_targets();
  
  	if (newval && strcmp(newval, "") != 0)
  	{
  		recoveryTarget = RECOVERY_TARGET_NAME;
  		recoveryTargetName = newval;
  	}
  	else
  		recoveryTarget = RECOVERY_TARGET_UNSET;
  }
  
  static bool
  check_recovery_target_lsn(char **newval, void **extra, GucSource source)
  {
  	if (strcmp(*newval, "") != 0)
  	{
  		XLogRecPtr	lsn;
  		XLogRecPtr *myextra;
  		bool		have_error = false;
  
  		lsn = pg_lsn_in_internal(*newval, &have_error);
  		if (have_error)
  			return false;
  
  		myextra = (XLogRecPtr *) guc_malloc(ERROR, sizeof(XLogRecPtr));
  		*myextra = lsn;
  		*extra = (void *) myextra;
  	}
  	return true;
  }
  
  static void
  assign_recovery_target_lsn(const char *newval, void *extra)
  {
  	if (recoveryTarget != RECOVERY_TARGET_UNSET &&
  		recoveryTarget != RECOVERY_TARGET_LSN)
  		error_multiple_recovery_targets();
  
  	if (newval && strcmp(newval, "") != 0)
  	{
  		recoveryTarget = RECOVERY_TARGET_LSN;
  		recoveryTargetLSN = *((XLogRecPtr *) extra);
  	}
  	else
  		recoveryTarget = RECOVERY_TARGET_UNSET;
  }
  
  static bool
  check_primary_slot_name(char **newval, void **extra, GucSource source)
  {
  	if (*newval && strcmp(*newval, "") != 0 &&
  		!ReplicationSlotValidateName(*newval, WARNING))
  		return false;
  
  	return true;
  }
  
  static bool
  check_default_with_oids(bool *newval, void **extra, GucSource source)
  {
  	if (*newval)
  	{
  		/* check the GUC's definition for an explanation */
  		GUC_check_errcode(ERRCODE_FEATURE_NOT_SUPPORTED);
  		GUC_check_errmsg("tables declared WITH OIDS are not supported");
  
  		return false;
  	}
  
  	return true;
  }
  
  #include "guc-file.c"
  