text: /* ----------
   *	pgstat.h
   *
   *	Definitions for the PostgreSQL statistics collector daemon.
   *
   *	Copyright (c) 2001-2020, PostgreSQL Global Development Group
   *
   *	src/include/pgstat.h
   * ----------
   */
  #ifndef PGSTAT_H
  #define PGSTAT_H
  
  #include "datatype/timestamp.h"
  #include "libpq/pqcomm.h"
  #include "miscadmin.h"
  #include "port/atomics.h"
  #include "portability/instr_time.h"
  #include "postmaster/pgarch.h"
  #include "storage/proc.h"
  #include "utils/hsearch.h"
  #include "utils/relcache.h"
  
  
  /* ----------
   * Paths for the statistics files (relative to installation's $PGDATA).
   * ----------
   */
  #define PGSTAT_STAT_PERMANENT_DIRECTORY		"pg_stat"
  #define PGSTAT_STAT_PERMANENT_FILENAME		"pg_stat/global.stat"
  #define PGSTAT_STAT_PERMANENT_TMPFILE		"pg_stat/global.tmp"
  
  /* Default directory to store temporary statistics data in */
  #define PG_STAT_TMP_DIR		"pg_stat_tmp"
  
  /* Values for track_functions GUC variable --- order is significant! */
  typedef enum TrackFunctionsLevel
  {
  	TRACK_FUNC_OFF,
  	TRACK_FUNC_PL,
  	TRACK_FUNC_ALL
  }			TrackFunctionsLevel;
  
  /* ----------
   * The types of backend -> collector messages
   * ----------
   */
  typedef enum StatMsgType
  {
  	PGSTAT_MTYPE_DUMMY,
  	PGSTAT_MTYPE_INQUIRY,
  	PGSTAT_MTYPE_TABSTAT,
  	PGSTAT_MTYPE_TABPURGE,
  	PGSTAT_MTYPE_DROPDB,
  	PGSTAT_MTYPE_RESETCOUNTER,
  	PGSTAT_MTYPE_RESETSHAREDCOUNTER,
  	PGSTAT_MTYPE_RESETSINGLECOUNTER,
  	PGSTAT_MTYPE_RESETSLRUCOUNTER,
  	PGSTAT_MTYPE_RESETREPLSLOTCOUNTER,
  	PGSTAT_MTYPE_AUTOVAC_START,
  	PGSTAT_MTYPE_VACUUM,
  	PGSTAT_MTYPE_ANALYZE,
  	PGSTAT_MTYPE_ARCHIVER,
  	PGSTAT_MTYPE_BGWRITER,
  	PGSTAT_MTYPE_WAL,
  	PGSTAT_MTYPE_SLRU,
  	PGSTAT_MTYPE_FUNCSTAT,
  	PGSTAT_MTYPE_FUNCPURGE,
  	PGSTAT_MTYPE_RECOVERYCONFLICT,
  	PGSTAT_MTYPE_TEMPFILE,
  	PGSTAT_MTYPE_DEADLOCK,
  	PGSTAT_MTYPE_CHECKSUMFAILURE,
  	PGSTAT_MTYPE_REPLSLOT,
  } StatMsgType;
  
  /* ----------
   * The data type used for counters.
   * ----------
   */
  typedef int64 PgStat_Counter;
  
  /* ----------
   * PgStat_TableCounts			The actual per-table counts kept by a backend
   *
   * This struct should contain only actual event counters, because we memcmp
   * it against zeroes to detect whether there are any counts to transmit.
   * It is a component of PgStat_TableStatus (within-backend state) and
   * PgStat_TableEntry (the transmitted message format).
   *
   * Note: for a table, tuples_returned is the number of tuples successfully
   * fetched by heap_getnext, while tuples_fetched is the number of tuples
   * successfully fetched by heap_fetch under the control of bitmap indexscans.
   * For an index, tuples_returned is the number of index entries returned by
   * the index AM, while tuples_fetched is the number of tuples successfully
   * fetched by heap_fetch under the control of simple indexscans for this index.
   *
   * tuples_inserted/updated/deleted/hot_updated count attempted actions,
   * regardless of whether the transaction committed.  delta_live_tuples,
   * delta_dead_tuples, and changed_tuples are set depending on commit or abort.
   * Note that delta_live_tuples and delta_dead_tuples can be negative!
   * ----------
   */
  typedef struct PgStat_TableCounts
  {
  	PgStat_Counter t_numscans;
  
  	PgStat_Counter t_tuples_returned;
  	PgStat_Counter t_tuples_fetched;
  
  	PgStat_Counter t_tuples_inserted;
  	PgStat_Counter t_tuples_updated;
  	PgStat_Counter t_tuples_deleted;
  	PgStat_Counter t_tuples_hot_updated;
  	bool		t_truncated;
  
  	PgStat_Counter t_delta_live_tuples;
  	PgStat_Counter t_delta_dead_tuples;
  	PgStat_Counter t_changed_tuples;
  
  	PgStat_Counter t_blocks_fetched;
  	PgStat_Counter t_blocks_hit;
  } PgStat_TableCounts;
  
  /* Possible targets for resetting cluster-wide shared values */
  typedef enum PgStat_Shared_Reset_Target
  {
  	RESET_ARCHIVER,
  	RESET_BGWRITER,
  	RESET_WAL
  } PgStat_Shared_Reset_Target;
  
  /* Possible object types for resetting single counters */
  typedef enum PgStat_Single_Reset_Type
  {
  	RESET_TABLE,
  	RESET_FUNCTION
  } PgStat_Single_Reset_Type;
  
  /* ------------------------------------------------------------
   * Structures kept in backend local memory while accumulating counts
   * ------------------------------------------------------------
   */
  
  
  /* ----------
   * PgStat_TableStatus			Per-table status within a backend
   *
   * Many of the event counters are nontransactional, ie, we count events
   * in committed and aborted transactions alike.  For these, we just count
   * directly in the PgStat_TableStatus.  However, delta_live_tuples,
   * delta_dead_tuples, and changed_tuples must be derived from event counts
   * with awareness of whether the transaction or subtransaction committed or
   * aborted.  Hence, we also keep a stack of per-(sub)transaction status
   * records for every table modified in the current transaction.  At commit
   * or abort, we propagate tuples_inserted/updated/deleted up to the
   * parent subtransaction level, or out to the parent PgStat_TableStatus,
   * as appropriate.
   * ----------
   */
  typedef struct PgStat_TableStatus
  {
  	Oid			t_id;			/* table's OID */
  	bool		t_shared;		/* is it a shared catalog? */
  	struct PgStat_TableXactStatus *trans;	/* lowest subxact's counts */
  	PgStat_TableCounts t_counts;	/* event counts to be sent */
  } PgStat_TableStatus;
  
  /* ----------
   * PgStat_TableXactStatus		Per-table, per-subtransaction status
   * ----------
   */
  typedef struct PgStat_TableXactStatus
  {
  	PgStat_Counter tuples_inserted; /* tuples inserted in (sub)xact */
  	PgStat_Counter tuples_updated;	/* tuples updated in (sub)xact */
  	PgStat_Counter tuples_deleted;	/* tuples deleted in (sub)xact */
  	bool		truncated;		/* relation truncated in this (sub)xact */
  	PgStat_Counter inserted_pre_trunc;	/* tuples inserted prior to truncate */
  	PgStat_Counter updated_pre_trunc;	/* tuples updated prior to truncate */
  	PgStat_Counter deleted_pre_trunc;	/* tuples deleted prior to truncate */
  	int			nest_level;		/* subtransaction nest level */
  	/* links to other structs for same relation: */
  	struct PgStat_TableXactStatus *upper;	/* next higher subxact if any */
  	PgStat_TableStatus *parent; /* per-table status */
  	/* structs of same subxact level are linked here: */
  	struct PgStat_TableXactStatus *next;	/* next of same subxact */
  } PgStat_TableXactStatus;
  
  
  /* ------------------------------------------------------------
   * Message formats follow
   * ------------------------------------------------------------
   */
  
  
  /* ----------
   * PgStat_MsgHdr				The common message header
   * ----------
   */
  typedef struct PgStat_MsgHdr
  {
  	StatMsgType m_type;
  	int			m_size;
  } PgStat_MsgHdr;
  
  /* ----------
   * Space available in a message.  This will keep the UDP packets below 1K,
   * which should fit unfragmented into the MTU of the loopback interface.
   * (Larger values of PGSTAT_MAX_MSG_SIZE would work for that on most
   * platforms, but we're being conservative here.)
   * ----------
   */
  #define PGSTAT_MAX_MSG_SIZE 1000
  #define PGSTAT_MSG_PAYLOAD	(PGSTAT_MAX_MSG_SIZE - sizeof(PgStat_MsgHdr))
  
  
  /* ----------
   * PgStat_MsgDummy				A dummy message, ignored by the collector
   * ----------
   */
  typedef struct PgStat_MsgDummy
  {
  	PgStat_MsgHdr m_hdr;
  } PgStat_MsgDummy;
  
  
  /* ----------
   * PgStat_MsgInquiry			Sent by a backend to ask the collector
   *								to write the stats file(s).
   *
   * Ordinarily, an inquiry message prompts writing of the global stats file,
   * the stats file for shared catalogs, and the stats file for the specified
   * database.  If databaseid is InvalidOid, only the first two are written.
   *
   * New file(s) will be written only if the existing file has a timestamp
   * older than the specified cutoff_time; this prevents duplicated effort
   * when multiple requests arrive at nearly the same time, assuming that
   * backends send requests with cutoff_times a little bit in the past.
   *
   * clock_time should be the requestor's current local time; the collector
   * uses this to check for the system clock going backward, but it has no
   * effect unless that occurs.  We assume clock_time >= cutoff_time, though.
   * ----------
   */
  
  typedef struct PgStat_MsgInquiry
  {
  	PgStat_MsgHdr m_hdr;
  	TimestampTz clock_time;		/* observed local clock time */
  	TimestampTz cutoff_time;	/* minimum acceptable file timestamp */
  	Oid			databaseid;		/* requested DB (InvalidOid => shared only) */
  } PgStat_MsgInquiry;
  
  
  /* ----------
   * PgStat_TableEntry			Per-table info in a MsgTabstat
   * ----------
   */
  typedef struct PgStat_TableEntry
  {
  	Oid			t_id;
  	PgStat_TableCounts t_counts;
  } PgStat_TableEntry;
  
  /* ----------
   * PgStat_MsgTabstat			Sent by the backend to report table
   *								and buffer access statistics.
   * ----------
   */
  #define PGSTAT_NUM_TABENTRIES  \
  	((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - 3 * sizeof(int) - 2 * sizeof(PgStat_Counter))	\
  	 / sizeof(PgStat_TableEntry))
  
  typedef struct PgStat_MsgTabstat
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	int			m_nentries;
  	int			m_xact_commit;
  	int			m_xact_rollback;
  	PgStat_Counter m_block_read_time;	/* times in microseconds */
  	PgStat_Counter m_block_write_time;
  	PgStat_TableEntry m_entry[PGSTAT_NUM_TABENTRIES];
  } PgStat_MsgTabstat;
  
  
  /* ----------
   * PgStat_MsgTabpurge			Sent by the backend to tell the collector
   *								about dead tables.
   * ----------
   */
  #define PGSTAT_NUM_TABPURGE  \
  	((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - sizeof(int))  \
  	 / sizeof(Oid))
  
  typedef struct PgStat_MsgTabpurge
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	int			m_nentries;
  	Oid			m_tableid[PGSTAT_NUM_TABPURGE];
  } PgStat_MsgTabpurge;
  
  
  /* ----------
   * PgStat_MsgDropdb				Sent by the backend to tell the collector
   *								about a dropped database
   * ----------
   */
  typedef struct PgStat_MsgDropdb
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  } PgStat_MsgDropdb;
  
  
  /* ----------
   * PgStat_MsgResetcounter		Sent by the backend to tell the collector
   *								to reset counters
   * ----------
   */
  typedef struct PgStat_MsgResetcounter
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  } PgStat_MsgResetcounter;
  
  /* ----------
   * PgStat_MsgResetsharedcounter Sent by the backend to tell the collector
   *								to reset a shared counter
   * ----------
   */
  typedef struct PgStat_MsgResetsharedcounter
  {
  	PgStat_MsgHdr m_hdr;
  	PgStat_Shared_Reset_Target m_resettarget;
  } PgStat_MsgResetsharedcounter;
  
  /* ----------
   * PgStat_MsgResetsinglecounter Sent by the backend to tell the collector
   *								to reset a single counter
   * ----------
   */
  typedef struct PgStat_MsgResetsinglecounter
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	PgStat_Single_Reset_Type m_resettype;
  	Oid			m_objectid;
  } PgStat_MsgResetsinglecounter;
  
  /* ----------
   * PgStat_MsgResetslrucounter Sent by the backend to tell the collector
   *								to reset a SLRU counter
   * ----------
   */
  typedef struct PgStat_MsgResetslrucounter
  {
  	PgStat_MsgHdr m_hdr;
  	int			m_index;
  } PgStat_MsgResetslrucounter;
  
  /* ----------
   * PgStat_MsgResetreplslotcounter Sent by the backend to tell the collector
   *								to reset replication slot counter(s)
   * ----------
   */
  typedef struct PgStat_MsgResetreplslotcounter
  {
  	PgStat_MsgHdr m_hdr;
  	char		m_slotname[NAMEDATALEN];
  	bool		clearall;
  } PgStat_MsgResetreplslotcounter;
  
  /* ----------
   * PgStat_MsgAutovacStart		Sent by the autovacuum daemon to signal
   *								that a database is going to be processed
   * ----------
   */
  typedef struct PgStat_MsgAutovacStart
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	TimestampTz m_start_time;
  } PgStat_MsgAutovacStart;
  
  
  /* ----------
   * PgStat_MsgVacuum				Sent by the backend or autovacuum daemon
   *								after VACUUM
   * ----------
   */
  typedef struct PgStat_MsgVacuum
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	Oid			m_tableoid;
  	bool		m_autovacuum;
  	TimestampTz m_vacuumtime;
  	PgStat_Counter m_live_tuples;
  	PgStat_Counter m_dead_tuples;
  } PgStat_MsgVacuum;
  
  
  /* ----------
   * PgStat_MsgAnalyze			Sent by the backend or autovacuum daemon
   *								after ANALYZE
   * ----------
   */
  typedef struct PgStat_MsgAnalyze
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	Oid			m_tableoid;
  	bool		m_autovacuum;
  	bool		m_resetcounter;
  	TimestampTz m_analyzetime;
  	PgStat_Counter m_live_tuples;
  	PgStat_Counter m_dead_tuples;
  } PgStat_MsgAnalyze;
  
  
  /* ----------
   * PgStat_MsgArchiver			Sent by the archiver to update statistics.
   * ----------
   */
  typedef struct PgStat_MsgArchiver
  {
  	PgStat_MsgHdr m_hdr;
  	bool		m_failed;		/* Failed attempt */
  	char		m_xlog[MAX_XFN_CHARS + 1];
  	TimestampTz m_timestamp;
  } PgStat_MsgArchiver;
  
  /* ----------
   * PgStat_MsgBgWriter			Sent by the bgwriter to update statistics.
   * ----------
   */
  typedef struct PgStat_MsgBgWriter
  {
  	PgStat_MsgHdr m_hdr;
  
  	PgStat_Counter m_timed_checkpoints;
  	PgStat_Counter m_requested_checkpoints;
  	PgStat_Counter m_buf_written_checkpoints;
  	PgStat_Counter m_buf_written_clean;
  	PgStat_Counter m_maxwritten_clean;
  	PgStat_Counter m_buf_written_backend;
  	PgStat_Counter m_buf_fsync_backend;
  	PgStat_Counter m_buf_alloc;
  	PgStat_Counter m_checkpoint_write_time; /* times in milliseconds */
  	PgStat_Counter m_checkpoint_sync_time;
  } PgStat_MsgBgWriter;
  
  /* ----------
   * PgStat_MsgWal			Sent by backends and background processes to update WAL statistics.
   * ----------
   */
  typedef struct PgStat_MsgWal
  {
  	PgStat_MsgHdr m_hdr;
  	PgStat_Counter m_wal_buffers_full;
  } PgStat_MsgWal;
  
  /* ----------
   * PgStat_MsgSLRU			Sent by a backend to update SLRU statistics.
   * ----------
   */
  typedef struct PgStat_MsgSLRU
  {
  	PgStat_MsgHdr m_hdr;
  	PgStat_Counter m_index;
  	PgStat_Counter m_blocks_zeroed;
  	PgStat_Counter m_blocks_hit;
  	PgStat_Counter m_blocks_read;
  	PgStat_Counter m_blocks_written;
  	PgStat_Counter m_blocks_exists;
  	PgStat_Counter m_flush;
  	PgStat_Counter m_truncate;
  } PgStat_MsgSLRU;
  
  /* ----------
   * PgStat_MsgReplSlot	Sent by a backend or a wal sender to update replication
   *						slot statistics.
   * ----------
   */
  typedef struct PgStat_MsgReplSlot
  {
  	PgStat_MsgHdr m_hdr;
  	char		m_slotname[NAMEDATALEN];
  	bool		m_drop;
  	PgStat_Counter m_spill_txns;
  	PgStat_Counter m_spill_count;
  	PgStat_Counter m_spill_bytes;
  } PgStat_MsgReplSlot;
  
  
  /* ----------
   * PgStat_MsgRecoveryConflict	Sent by the backend upon recovery conflict
   * ----------
   */
  typedef struct PgStat_MsgRecoveryConflict
  {
  	PgStat_MsgHdr m_hdr;
  
  	Oid			m_databaseid;
  	int			m_reason;
  } PgStat_MsgRecoveryConflict;
  
  /* ----------
   * PgStat_MsgTempFile	Sent by the backend upon creating a temp file
   * ----------
   */
  typedef struct PgStat_MsgTempFile
  {
  	PgStat_MsgHdr m_hdr;
  
  	Oid			m_databaseid;
  	size_t		m_filesize;
  } PgStat_MsgTempFile;
  
  /* ----------
   * PgStat_FunctionCounts	The actual per-function counts kept by a backend
   *
   * This struct should contain only actual event counters, because we memcmp
   * it against zeroes to detect whether there are any counts to transmit.
   *
   * Note that the time counters are in instr_time format here.  We convert to
   * microseconds in PgStat_Counter format when transmitting to the collector.
   * ----------
   */
  typedef struct PgStat_FunctionCounts
  {
  	PgStat_Counter f_numcalls;
  	instr_time	f_total_time;
  	instr_time	f_self_time;
  } PgStat_FunctionCounts;
  
  /* ----------
   * PgStat_BackendFunctionEntry	Entry in backend's per-function hash table
   * ----------
   */
  typedef struct PgStat_BackendFunctionEntry
  {
  	Oid			f_id;
  	PgStat_FunctionCounts f_counts;
  } PgStat_BackendFunctionEntry;
  
  /* ----------
   * PgStat_FunctionEntry			Per-function info in a MsgFuncstat
   * ----------
   */
  typedef struct PgStat_FunctionEntry
  {
  	Oid			f_id;
  	PgStat_Counter f_numcalls;
  	PgStat_Counter f_total_time;	/* times in microseconds */
  	PgStat_Counter f_self_time;
  } PgStat_FunctionEntry;
  
  /* ----------
   * PgStat_MsgFuncstat			Sent by the backend to report function
   *								usage statistics.
   * ----------
   */
  #define PGSTAT_NUM_FUNCENTRIES	\
  	((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - sizeof(int))  \
  	 / sizeof(PgStat_FunctionEntry))
  
  typedef struct PgStat_MsgFuncstat
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	int			m_nentries;
  	PgStat_FunctionEntry m_entry[PGSTAT_NUM_FUNCENTRIES];
  } PgStat_MsgFuncstat;
  
  /* ----------
   * PgStat_MsgFuncpurge			Sent by the backend to tell the collector
   *								about dead functions.
   * ----------
   */
  #define PGSTAT_NUM_FUNCPURGE  \
  	((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - sizeof(int))  \
  	 / sizeof(Oid))
  
  typedef struct PgStat_MsgFuncpurge
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	int			m_nentries;
  	Oid			m_functionid[PGSTAT_NUM_FUNCPURGE];
  } PgStat_MsgFuncpurge;
  
  /* ----------
   * PgStat_MsgDeadlock			Sent by the backend to tell the collector
   *								about a deadlock that occurred.
   * ----------
   */
  typedef struct PgStat_MsgDeadlock
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  } PgStat_MsgDeadlock;
  
  /* ----------
   * PgStat_MsgChecksumFailure	Sent by the backend to tell the collector
   *								about checksum failures noticed.
   * ----------
   */
  typedef struct PgStat_MsgChecksumFailure
  {
  	PgStat_MsgHdr m_hdr;
  	Oid			m_databaseid;
  	int			m_failurecount;
  	TimestampTz m_failure_time;
  } PgStat_MsgChecksumFailure;
  
  
  /* ----------
   * PgStat_Msg					Union over all possible messages.
   * ----------
   */
  typedef union PgStat_Msg
  {
  	PgStat_MsgHdr msg_hdr;
  	PgStat_MsgDummy msg_dummy;
  	PgStat_MsgInquiry msg_inquiry;
  	PgStat_MsgTabstat msg_tabstat;
  	PgStat_MsgTabpurge msg_tabpurge;
  	PgStat_MsgDropdb msg_dropdb;
  	PgStat_MsgResetcounter msg_resetcounter;
  	PgStat_MsgResetsharedcounter msg_resetsharedcounter;
  	PgStat_MsgResetsinglecounter msg_resetsinglecounter;
  	PgStat_MsgResetslrucounter msg_resetslrucounter;
  	PgStat_MsgResetreplslotcounter msg_resetreplslotcounter;
  	PgStat_MsgAutovacStart msg_autovacuum_start;
  	PgStat_MsgVacuum msg_vacuum;
  	PgStat_MsgAnalyze msg_analyze;
  	PgStat_MsgArchiver msg_archiver;
  	PgStat_MsgBgWriter msg_bgwriter;
  	PgStat_MsgWal msg_wal;
  	PgStat_MsgSLRU msg_slru;
  	PgStat_MsgFuncstat msg_funcstat;
  	PgStat_MsgFuncpurge msg_funcpurge;
  	PgStat_MsgRecoveryConflict msg_recoveryconflict;
  	PgStat_MsgDeadlock msg_deadlock;
  	PgStat_MsgTempFile msg_tempfile;
  	PgStat_MsgChecksumFailure msg_checksumfailure;
  	PgStat_MsgReplSlot msg_replslot;
  } PgStat_Msg;
  
  
  /* ------------------------------------------------------------
   * Statistic collector data structures follow
   *
   * PGSTAT_FILE_FORMAT_ID should be changed whenever any of these
   * data structures change.
   * ------------------------------------------------------------
   */
  
  #define PGSTAT_FILE_FORMAT_ID	0x01A5BC9F
  
  /* ----------
   * PgStat_StatDBEntry			The collector's data per database
   * ----------
   */
  typedef struct PgStat_StatDBEntry
  {
  	Oid			databaseid;
  	PgStat_Counter n_xact_commit;
  	PgStat_Counter n_xact_rollback;
  	PgStat_Counter n_blocks_fetched;
  	PgStat_Counter n_blocks_hit;
  	PgStat_Counter n_tuples_returned;
  	PgStat_Counter n_tuples_fetched;
  	PgStat_Counter n_tuples_inserted;
  	PgStat_Counter n_tuples_updated;
  	PgStat_Counter n_tuples_deleted;
  	TimestampTz last_autovac_time;
  	PgStat_Counter n_conflict_tablespace;
  	PgStat_Counter n_conflict_lock;
  	PgStat_Counter n_conflict_snapshot;
  	PgStat_Counter n_conflict_bufferpin;
  	PgStat_Counter n_conflict_startup_deadlock;
  	PgStat_Counter n_temp_files;
  	PgStat_Counter n_temp_bytes;
  	PgStat_Counter n_deadlocks;
  	PgStat_Counter n_checksum_failures;
  	TimestampTz last_checksum_failure;
  	PgStat_Counter n_block_read_time;	/* times in microseconds */
  	PgStat_Counter n_block_write_time;
  
  	TimestampTz stat_reset_timestamp;
  	TimestampTz stats_timestamp;	/* time of db stats file update */
  
  	/*
  	 * tables and functions must be last in the struct, because we don't write
  	 * the pointers out to the stats file.
  	 */
  	HTAB	   *tables;
  	HTAB	   *functions;
  } PgStat_StatDBEntry;
  
  
  /* ----------
   * PgStat_StatTabEntry			The collector's data per table (or index)
   * ----------
   */
  typedef struct PgStat_StatTabEntry
  {
  	Oid			tableid;
  
  	PgStat_Counter numscans;
  
  	PgStat_Counter tuples_returned;
  	PgStat_Counter tuples_fetched;
  
  	PgStat_Counter tuples_inserted;
  	PgStat_Counter tuples_updated;
  	PgStat_Counter tuples_deleted;
  	PgStat_Counter tuples_hot_updated;
  
  	PgStat_Counter n_live_tuples;
  	PgStat_Counter n_dead_tuples;
  	PgStat_Counter changes_since_analyze;
  	PgStat_Counter inserts_since_vacuum;
  
  	PgStat_Counter blocks_fetched;
  	PgStat_Counter blocks_hit;
  
  	TimestampTz vacuum_timestamp;	/* user initiated vacuum */
  	PgStat_Counter vacuum_count;
  	TimestampTz autovac_vacuum_timestamp;	/* autovacuum initiated */
  	PgStat_Counter autovac_vacuum_count;
  	TimestampTz analyze_timestamp;	/* user initiated */
  	PgStat_Counter analyze_count;
  	TimestampTz autovac_analyze_timestamp;	/* autovacuum initiated */
  	PgStat_Counter autovac_analyze_count;
  } PgStat_StatTabEntry;
  
  
  /* ----------
   * PgStat_StatFuncEntry			The collector's data per function
   * ----------
   */
  typedef struct PgStat_StatFuncEntry
  {
  	Oid			functionid;
  
  	PgStat_Counter f_numcalls;
  
  	PgStat_Counter f_total_time;	/* times in microseconds */
  	PgStat_Counter f_self_time;
  } PgStat_StatFuncEntry;
  
  
  /*
   * Archiver statistics kept in the stats collector
   */
  typedef struct PgStat_ArchiverStats
  {
  	PgStat_Counter archived_count;	/* archival successes */
  	char		last_archived_wal[MAX_XFN_CHARS + 1];	/* last WAL file
  														 * archived */
  	TimestampTz last_archived_timestamp;	/* last archival success time */
  	PgStat_Counter failed_count;	/* failed archival attempts */
  	char		last_failed_wal[MAX_XFN_CHARS + 1]; /* WAL file involved in
  													 * last failure */
  	TimestampTz last_failed_timestamp;	/* last archival failure time */
  	TimestampTz stat_reset_timestamp;
  } PgStat_ArchiverStats;
  
  /*
   * Global statistics kept in the stats collector
   */
  typedef struct PgStat_GlobalStats
  {
  	TimestampTz stats_timestamp;	/* time of stats file update */
  	PgStat_Counter timed_checkpoints;
  	PgStat_Counter requested_checkpoints;
  	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
  	PgStat_Counter checkpoint_sync_time;
  	PgStat_Counter buf_written_checkpoints;
  	PgStat_Counter buf_written_clean;
  	PgStat_Counter maxwritten_clean;
  	PgStat_Counter buf_written_backend;
  	PgStat_Counter buf_fsync_backend;
  	PgStat_Counter buf_alloc;
  	TimestampTz stat_reset_timestamp;
  } PgStat_GlobalStats;
  
  /*
   * WAL statistics kept in the stats collector
   */
  typedef struct PgStat_WalStats
  {
  	PgStat_Counter wal_buffers_full;
  	TimestampTz stat_reset_timestamp;
  } PgStat_WalStats;
  
  /*
   * SLRU statistics kept in the stats collector
   */
  typedef struct PgStat_SLRUStats
  {
  	PgStat_Counter blocks_zeroed;
  	PgStat_Counter blocks_hit;
  	PgStat_Counter blocks_read;
  	PgStat_Counter blocks_written;
  	PgStat_Counter blocks_exists;
  	PgStat_Counter flush;
  	PgStat_Counter truncate;
  	TimestampTz stat_reset_timestamp;
  } PgStat_SLRUStats;
  
  /*
   * Replication slot statistics kept in the stats collector
   */
  typedef struct PgStat_ReplSlotStats
  {
  	char		slotname[NAMEDATALEN];
  	PgStat_Counter spill_txns;
  	PgStat_Counter spill_count;
  	PgStat_Counter spill_bytes;
  	TimestampTz stat_reset_timestamp;
  } PgStat_ReplSlotStats;
  
  /* ----------
   * Backend states
   * ----------
   */
  typedef enum BackendState
  {
  	STATE_UNDEFINED,
  	STATE_IDLE,
  	STATE_RUNNING,
  	STATE_IDLEINTRANSACTION,
  	STATE_FASTPATH,
  	STATE_IDLEINTRANSACTION_ABORTED,
  	STATE_DISABLED
  } BackendState;
  
  
  /* ----------
   * Wait Classes
   * ----------
   */
  #define PG_WAIT_LWLOCK				0x01000000U
  #define PG_WAIT_LOCK				0x03000000U
  #define PG_WAIT_BUFFER_PIN			0x04000000U
  #define PG_WAIT_ACTIVITY			0x05000000U
  #define PG_WAIT_CLIENT				0x06000000U
  #define PG_WAIT_EXTENSION			0x07000000U
  #define PG_WAIT_IPC					0x08000000U
  #define PG_WAIT_TIMEOUT				0x09000000U
  #define PG_WAIT_IO					0x0A000000U
  
  /* ----------
   * Wait Events - Activity
   *
   * Use this category when a process is waiting because it has no work to do,
   * unless the "Client" or "Timeout" category describes the situation better.
   * Typically, this should only be used for background processes.
   * ----------
   */
  typedef enum
  {
  	WAIT_EVENT_ARCHIVER_MAIN = PG_WAIT_ACTIVITY,
  	WAIT_EVENT_AUTOVACUUM_MAIN,
  	WAIT_EVENT_BGWRITER_HIBERNATE,
  	WAIT_EVENT_BGWRITER_MAIN,
  	WAIT_EVENT_CHECKPOINTER_MAIN,
  	WAIT_EVENT_LOGICAL_APPLY_MAIN,
  	WAIT_EVENT_LOGICAL_LAUNCHER_MAIN,
  	WAIT_EVENT_PGSTAT_MAIN,
  	WAIT_EVENT_RECOVERY_WAL_STREAM,
  	WAIT_EVENT_SYSLOGGER_MAIN,
  	WAIT_EVENT_WAL_RECEIVER_MAIN,
  	WAIT_EVENT_WAL_SENDER_MAIN,
  	WAIT_EVENT_WAL_WRITER_MAIN
  } WaitEventActivity;
  
  /* ----------
   * Wait Events - Client
   *
   * Use this category when a process is waiting to send data to or receive data
   * from the frontend process to which it is connected.  This is never used for
   * a background process, which has no client connection.
   * ----------
   */
  typedef enum
  {
  	WAIT_EVENT_CLIENT_READ = PG_WAIT_CLIENT,
  	WAIT_EVENT_CLIENT_WRITE,
  	WAIT_EVENT_GSS_OPEN_SERVER,
  	WAIT_EVENT_LIBPQWALRECEIVER_CONNECT,
  	WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE,
  	WAIT_EVENT_SSL_OPEN_SERVER,
  	WAIT_EVENT_WAL_RECEIVER_WAIT_START,
  	WAIT_EVENT_WAL_SENDER_WAIT_WAL,
  	WAIT_EVENT_WAL_SENDER_WRITE_DATA,
  } WaitEventClient;
  
  /* ----------
   * Wait Events - IPC
   *
   * Use this category when a process cannot complete the work it is doing because
   * it is waiting for a notification from another process.
   * ----------
   */
  typedef enum
  {
  	WAIT_EVENT_BACKUP_WAIT_WAL_ARCHIVE = PG_WAIT_IPC,
  	WAIT_EVENT_BGWORKER_SHUTDOWN,
  	WAIT_EVENT_BGWORKER_STARTUP,
  	WAIT_EVENT_BTREE_PAGE,
  	WAIT_EVENT_CHECKPOINT_DONE,
  	WAIT_EVENT_CHECKPOINT_START,
  	WAIT_EVENT_EXECUTE_GATHER,
  	WAIT_EVENT_HASH_BATCH_ALLOCATE,
  	WAIT_EVENT_HASH_BATCH_ELECT,
  	WAIT_EVENT_HASH_BATCH_LOAD,
  	WAIT_EVENT_HASH_BUILD_ALLOCATE,
  	WAIT_EVENT_HASH_BUILD_ELECT,
  	WAIT_EVENT_HASH_BUILD_HASH_INNER,
  	WAIT_EVENT_HASH_BUILD_HASH_OUTER,
  	WAIT_EVENT_HASH_GROW_BATCHES_ALLOCATE,
  	WAIT_EVENT_HASH_GROW_BATCHES_DECIDE,
  	WAIT_EVENT_HASH_GROW_BATCHES_ELECT,
  	WAIT_EVENT_HASH_GROW_BATCHES_FINISH,
  	WAIT_EVENT_HASH_GROW_BATCHES_REPARTITION,
  	WAIT_EVENT_HASH_GROW_BUCKETS_ALLOCATE,
  	WAIT_EVENT_HASH_GROW_BUCKETS_ELECT,
  	WAIT_EVENT_HASH_GROW_BUCKETS_REINSERT,
  	WAIT_EVENT_LOGICAL_SYNC_DATA,
  	WAIT_EVENT_LOGICAL_SYNC_STATE_CHANGE,
  	WAIT_EVENT_MQ_INTERNAL,
  	WAIT_EVENT_MQ_PUT_MESSAGE,
  	WAIT_EVENT_MQ_RECEIVE,
  	WAIT_EVENT_MQ_SEND,
  	WAIT_EVENT_PARALLEL_BITMAP_SCAN,
  	WAIT_EVENT_PARALLEL_CREATE_INDEX_SCAN,
  	WAIT_EVENT_PARALLEL_FINISH,
  	WAIT_EVENT_PROCARRAY_GROUP_UPDATE,
  	WAIT_EVENT_PROC_SIGNAL_BARRIER,
  	WAIT_EVENT_PROMOTE,
  	WAIT_EVENT_RECOVERY_CONFLICT_SNAPSHOT,
  	WAIT_EVENT_RECOVERY_CONFLICT_TABLESPACE,
  	WAIT_EVENT_RECOVERY_PAUSE,
  	WAIT_EVENT_REPLICATION_ORIGIN_DROP,
  	WAIT_EVENT_REPLICATION_SLOT_DROP,
  	WAIT_EVENT_SAFE_SNAPSHOT,
  	WAIT_EVENT_SYNC_REP,
  	WAIT_EVENT_XACT_GROUP_UPDATE
  } WaitEventIPC;
  
  /* ----------
   * Wait Events - Timeout
   *
   * Use this category when a process is waiting for a timeout to expire.
   * ----------
   */
  typedef enum
  {
  	WAIT_EVENT_BASE_BACKUP_THROTTLE = PG_WAIT_TIMEOUT,
  	WAIT_EVENT_PG_SLEEP,
  	WAIT_EVENT_RECOVERY_APPLY_DELAY,
  	WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL,
  	WAIT_EVENT_VACUUM_DELAY
  } WaitEventTimeout;
  
  /* ----------
   * Wait Events - IO
   *
   * Use this category when a process is waiting for a IO.
   * ----------
   */
  typedef enum
  {
  	WAIT_EVENT_BASEBACKUP_READ = PG_WAIT_IO,
  	WAIT_EVENT_BUFFILE_READ,
  	WAIT_EVENT_BUFFILE_WRITE,
  	WAIT_EVENT_BUFFILE_TRUNCATE,
  	WAIT_EVENT_CONTROL_FILE_READ,
  	WAIT_EVENT_CONTROL_FILE_SYNC,
  	WAIT_EVENT_CONTROL_FILE_SYNC_UPDATE,
  	WAIT_EVENT_CONTROL_FILE_WRITE,
  	WAIT_EVENT_CONTROL_FILE_WRITE_UPDATE,
  	WAIT_EVENT_COPY_FILE_READ,
  	WAIT_EVENT_COPY_FILE_WRITE,
  	WAIT_EVENT_DATA_FILE_EXTEND,
  	WAIT_EVENT_DATA_FILE_FLUSH,
  	WAIT_EVENT_DATA_FILE_IMMEDIATE_SYNC,
  	WAIT_EVENT_DATA_FILE_PREFETCH,
  	WAIT_EVENT_DATA_FILE_READ,
  	WAIT_EVENT_DATA_FILE_SYNC,
  	WAIT_EVENT_DATA_FILE_TRUNCATE,
  	WAIT_EVENT_DATA_FILE_WRITE,
  	WAIT_EVENT_DSM_FILL_ZERO_WRITE,
  	WAIT_EVENT_LOCK_FILE_ADDTODATADIR_READ,
  	WAIT_EVENT_LOCK_FILE_ADDTODATADIR_SYNC,
  	WAIT_EVENT_LOCK_FILE_ADDTODATADIR_WRITE,
  	WAIT_EVENT_LOCK_FILE_CREATE_READ,
  	WAIT_EVENT_LOCK_FILE_CREATE_SYNC,
  	WAIT_EVENT_LOCK_FILE_CREATE_WRITE,
  	WAIT_EVENT_LOCK_FILE_RECHECKDATADIR_READ,
  	WAIT_EVENT_LOGICAL_REWRITE_CHECKPOINT_SYNC,
  	WAIT_EVENT_LOGICAL_REWRITE_MAPPING_SYNC,
  	WAIT_EVENT_LOGICAL_REWRITE_MAPPING_WRITE,
  	WAIT_EVENT_LOGICAL_REWRITE_SYNC,
  	WAIT_EVENT_LOGICAL_REWRITE_TRUNCATE,
  	WAIT_EVENT_LOGICAL_REWRITE_WRITE,
  	WAIT_EVENT_RELATION_MAP_READ,
  	WAIT_EVENT_RELATION_MAP_SYNC,
  	WAIT_EVENT_RELATION_MAP_WRITE,
  	WAIT_EVENT_REORDER_BUFFER_READ,
  	WAIT_EVENT_REORDER_BUFFER_WRITE,
  	WAIT_EVENT_REORDER_LOGICAL_MAPPING_READ,
  	WAIT_EVENT_REPLICATION_SLOT_READ,
  	WAIT_EVENT_REPLICATION_SLOT_RESTORE_SYNC,
  	WAIT_EVENT_REPLICATION_SLOT_SYNC,
  	WAIT_EVENT_REPLICATION_SLOT_WRITE,
  	WAIT_EVENT_SLRU_FLUSH_SYNC,
  	WAIT_EVENT_SLRU_READ,
  	WAIT_EVENT_SLRU_SYNC,
  	WAIT_EVENT_SLRU_WRITE,
  	WAIT_EVENT_SNAPBUILD_READ,
  	WAIT_EVENT_SNAPBUILD_SYNC,
  	WAIT_EVENT_SNAPBUILD_WRITE,
  	WAIT_EVENT_TIMELINE_HISTORY_FILE_SYNC,
  	WAIT_EVENT_TIMELINE_HISTORY_FILE_WRITE,
  	WAIT_EVENT_TIMELINE_HISTORY_READ,
  	WAIT_EVENT_TIMELINE_HISTORY_SYNC,
  	WAIT_EVENT_TIMELINE_HISTORY_WRITE,
  	WAIT_EVENT_TWOPHASE_FILE_READ,
  	WAIT_EVENT_TWOPHASE_FILE_SYNC,
  	WAIT_EVENT_TWOPHASE_FILE_WRITE,
  	WAIT_EVENT_WALSENDER_TIMELINE_HISTORY_READ,
  	WAIT_EVENT_WAL_BOOTSTRAP_SYNC,
  	WAIT_EVENT_WAL_BOOTSTRAP_WRITE,
  	WAIT_EVENT_WAL_COPY_READ,
  	WAIT_EVENT_WAL_COPY_SYNC,
  	WAIT_EVENT_WAL_COPY_WRITE,
  	WAIT_EVENT_WAL_INIT_SYNC,
  	WAIT_EVENT_WAL_INIT_WRITE,
  	WAIT_EVENT_WAL_READ,
  	WAIT_EVENT_WAL_SYNC,
  	WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN,
  	WAIT_EVENT_WAL_WRITE,
  	WAIT_EVENT_LOGICAL_CHANGES_READ,
  	WAIT_EVENT_LOGICAL_CHANGES_WRITE,
  	WAIT_EVENT_LOGICAL_SUBXACT_READ,
  	WAIT_EVENT_LOGICAL_SUBXACT_WRITE
  } WaitEventIO;
  
  /* ----------
   * Command type for progress reporting purposes
   * ----------
   */
  typedef enum ProgressCommandType
  {
  	PROGRESS_COMMAND_INVALID,
  	PROGRESS_COMMAND_VACUUM,
  	PROGRESS_COMMAND_ANALYZE,
  	PROGRESS_COMMAND_CLUSTER,
  	PROGRESS_COMMAND_CREATE_INDEX,
  	PROGRESS_COMMAND_BASEBACKUP
  } ProgressCommandType;
  
  #define PGSTAT_NUM_PROGRESS_PARAM	20
  
  /* ----------
   * Shared-memory data structures
   * ----------
   */
  
  
  /*
   * PgBackendSSLStatus
   *
   * For each backend, we keep the SSL status in a separate struct, that
   * is only filled in if SSL is enabled.
   *
   * All char arrays must be null-terminated.
   */
  typedef struct PgBackendSSLStatus
  {
  	/* Information about SSL connection */
  	int			ssl_bits;
  	bool		ssl_compression;
  	char		ssl_version[NAMEDATALEN];
  	char		ssl_cipher[NAMEDATALEN];
  	char		ssl_client_dn[NAMEDATALEN];
  
  	/*
  	 * serial number is max "20 octets" per RFC 5280, so this size should be
  	 * fine
  	 */
  	char		ssl_client_serial[NAMEDATALEN];
  
  	char		ssl_issuer_dn[NAMEDATALEN];
  } PgBackendSSLStatus;
  
  /*
   * PgBackendGSSStatus
   *
   * For each backend, we keep the GSS status in a separate struct, that
   * is only filled in if GSS is enabled.
   *
   * All char arrays must be null-terminated.
   */
  typedef struct PgBackendGSSStatus
  {
  	/* Information about GSSAPI connection */
  	char		gss_princ[NAMEDATALEN]; /* GSSAPI Principal used to auth */
  	bool		gss_auth;		/* If GSSAPI authentication was used */
  	bool		gss_enc;		/* If encryption is being used */
  
  } PgBackendGSSStatus;
  
  
  /* ----------
   * PgBackendStatus
   *
   * Each live backend maintains a PgBackendStatus struct in shared memory
   * showing its current activity.  (The structs are allocated according to
   * BackendId, but that is not critical.)  Note that the collector process
   * has no involvement in, or even access to, these structs.
   *
   * Each auxiliary process also maintains a PgBackendStatus struct in shared
   * memory.
   * ----------
   */
  typedef struct PgBackendStatus
  {
  	/*
  	 * To avoid locking overhead, we use the following protocol: a backend
  	 * increments st_changecount before modifying its entry, and again after
  	 * finishing a modification.  A would-be reader should note the value of
  	 * st_changecount, copy the entry into private memory, then check
  	 * st_changecount again.  If the value hasn't changed, and if it's even,
  	 * the copy is valid; otherwise start over.  This makes updates cheap
  	 * while reads are potentially expensive, but that's the tradeoff we want.
  	 *
  	 * The above protocol needs memory barriers to ensure that the apparent
  	 * order of execution is as it desires.  Otherwise, for example, the CPU
  	 * might rearrange the code so that st_changecount is incremented twice
  	 * before the modification on a machine with weak memory ordering.  Hence,
  	 * use the macros defined below for manipulating st_changecount, rather
  	 * than touching it directly.
  	 */
  	int			st_changecount;
  
  	/* The entry is valid iff st_procpid > 0, unused if st_procpid == 0 */
  	int			st_procpid;
  
  	/* Type of backends */
  	BackendType st_backendType;
  
  	/* Times when current backend, transaction, and activity started */
  	TimestampTz st_proc_start_timestamp;
  	TimestampTz st_xact_start_timestamp;
  	TimestampTz st_activity_start_timestamp;
  	TimestampTz st_state_start_timestamp;
  
  	/* Database OID, owning user's OID, connection client address */
  	Oid			st_databaseid;
  	Oid			st_userid;
  	SockAddr	st_clientaddr;
  	char	   *st_clienthostname;	/* MUST be null-terminated */
  
  	/* Information about SSL connection */
  	bool		st_ssl;
  	PgBackendSSLStatus *st_sslstatus;
  
  	/* Information about GSSAPI connection */
  	bool		st_gss;
  	PgBackendGSSStatus *st_gssstatus;
  
  	/* current state */
  	BackendState st_state;
  
  	/* application name; MUST be null-terminated */
  	char	   *st_appname;
  
  	/*
  	 * Current command string; MUST be null-terminated. Note that this string
  	 * possibly is truncated in the middle of a multi-byte character. As
  	 * activity strings are stored more frequently than read, that allows to
  	 * move the cost of correct truncation to the display side. Use
  	 * pgstat_clip_activity() to truncate correctly.
  	 */
  	char	   *st_activity_raw;
  
  	/*
  	 * Command progress reporting.  Any command which wishes can advertise
  	 * that it is running by setting st_progress_command,
  	 * st_progress_command_target, and st_progress_param[].
  	 * st_progress_command_target should be the OID of the relation which the
  	 * command targets (we assume there's just one, as this is meant for
  	 * utility commands), but the meaning of each element in the
  	 * st_progress_param array is command-specific.
  	 */
  	ProgressCommandType st_progress_command;
  	Oid			st_progress_command_target;
  	int64		st_progress_param[PGSTAT_NUM_PROGRESS_PARAM];
  } PgBackendStatus;
  
  /*
   * Macros to load and store st_changecount with appropriate memory barriers.
   *
   * Use PGSTAT_BEGIN_WRITE_ACTIVITY() before, and PGSTAT_END_WRITE_ACTIVITY()
   * after, modifying the current process's PgBackendStatus data.  Note that,
   * since there is no mechanism for cleaning up st_changecount after an error,
   * THESE MACROS FORM A CRITICAL SECTION.  Any error between them will be
   * promoted to PANIC, causing a database restart to clean up shared memory!
   * Hence, keep the critical section as short and straight-line as possible.
   * Aside from being safer, that minimizes the window in which readers will
   * have to loop.
   *
   * Reader logic should follow this sketch:
   *
   *		for (;;)
   *		{
   *			int before_ct, after_ct;
   *
   *			pgstat_begin_read_activity(beentry, before_ct);
   *			... copy beentry data to local memory ...
   *			pgstat_end_read_activity(beentry, after_ct);
   *			if (pgstat_read_activity_complete(before_ct, after_ct))
   *				break;
   *			CHECK_FOR_INTERRUPTS();
   *		}
   *
   * For extra safety, we generally use volatile beentry pointers, although
   * the memory barriers should theoretically be sufficient.
   */
  #define PGSTAT_BEGIN_WRITE_ACTIVITY(beentry) \
  	do { \
  		START_CRIT_SECTION(); \
  		(beentry)->st_changecount++; \
  		pg_write_barrier(); \
  	} while (0)
  
  #define PGSTAT_END_WRITE_ACTIVITY(beentry) \
  	do { \
  		pg_write_barrier(); \
  		(beentry)->st_changecount++; \
  		Assert(((beentry)->st_changecount & 1) == 0); \
  		END_CRIT_SECTION(); \
  	} while (0)
  
  #define pgstat_begin_read_activity(beentry, before_changecount) \
  	do { \
  		(before_changecount) = (beentry)->st_changecount; \
  		pg_read_barrier(); \
  	} while (0)
  
  #define pgstat_end_read_activity(beentry, after_changecount) \
  	do { \
  		pg_read_barrier(); \
  		(after_changecount) = (beentry)->st_changecount; \
  	} while (0)
  
  #define pgstat_read_activity_complete(before_changecount, after_changecount) \
  	((before_changecount) == (after_changecount) && \
  	 ((before_changecount) & 1) == 0)
  
  
  /* ----------
   * LocalPgBackendStatus
   *
   * When we build the backend status array, we use LocalPgBackendStatus to be
   * able to add new values to the struct when needed without adding new fields
   * to the shared memory. It contains the backend status as a first member.
   * ----------
   */
  typedef struct LocalPgBackendStatus
  {
  	/*
  	 * Local version of the backend status entry.
  	 */
  	PgBackendStatus backendStatus;
  
  	/*
  	 * The xid of the current transaction if available, InvalidTransactionId
  	 * if not.
  	 */
  	TransactionId backend_xid;
  
  	/*
  	 * The xmin of the current session if available, InvalidTransactionId if
  	 * not.
  	 */
  	TransactionId backend_xmin;
  } LocalPgBackendStatus;
  
  /*
   * Working state needed to accumulate per-function-call timing statistics.
   */
  typedef struct PgStat_FunctionCallUsage
  {
  	/* Link to function's hashtable entry (must still be there at exit!) */
  	/* NULL means we are not tracking the current function call */
  	PgStat_FunctionCounts *fs;
  	/* Total time previously charged to function, as of function start */
  	instr_time	save_f_total_time;
  	/* Backend-wide total time as of function start */
  	instr_time	save_total;
  	/* system clock as of function start */
  	instr_time	f_start;
  } PgStat_FunctionCallUsage;
  
  
  /* ----------
   * GUC parameters
   * ----------
   */
  extern PGDLLIMPORT bool pgstat_track_activities;
  extern PGDLLIMPORT bool pgstat_track_counts;
  extern PGDLLIMPORT int pgstat_track_functions;
  extern PGDLLIMPORT int pgstat_track_activity_query_size;
  extern char *pgstat_stat_directory;
  extern char *pgstat_stat_tmpname;
  extern char *pgstat_stat_filename;
  
  /*
   * BgWriter statistics counters are updated directly by bgwriter and bufmgr
   */
  extern PgStat_MsgBgWriter BgWriterStats;
  
  /*
   * WAL statistics counter is updated by backends and background processes
   */
  extern PgStat_MsgWal WalStats;
  
  /*
   * Updated by pgstat_count_buffer_*_time macros
   */
  extern PgStat_Counter pgStatBlockReadTime;
  extern PgStat_Counter pgStatBlockWriteTime;
  
  /* ----------
   * Functions called from postmaster
   * ----------
   */
  extern Size BackendStatusShmemSize(void);
  extern void CreateSharedBackendStatus(void);
  
  extern void pgstat_init(void);
  extern int	pgstat_start(void);
  extern void pgstat_reset_all(void);
  extern void allow_immediate_pgstat_restart(void);
  
  #ifdef EXEC_BACKEND
  extern void PgstatCollectorMain(int argc, char *argv[]) pg_attribute_noreturn();
  #endif
  
  
  /* ----------
   * Functions called from backends
   * ----------
   */
  extern void pgstat_ping(void);
  
  extern void pgstat_report_stat(bool force);
  extern void pgstat_vacuum_stat(void);
  extern void pgstat_drop_database(Oid databaseid);
  
  extern void pgstat_clear_snapshot(void);
  extern void pgstat_reset_counters(void);
  extern void pgstat_reset_shared_counters(const char *);
  extern void pgstat_reset_single_counter(Oid objectid, PgStat_Single_Reset_Type type);
  extern void pgstat_reset_slru_counter(const char *);
  extern void pgstat_reset_replslot_counter(const char *name);
  
  extern void pgstat_report_autovac(Oid dboid);
  extern void pgstat_report_vacuum(Oid tableoid, bool shared,
  								 PgStat_Counter livetuples, PgStat_Counter deadtuples);
  extern void pgstat_report_analyze(Relation rel,
  								  PgStat_Counter livetuples, PgStat_Counter deadtuples,
  								  bool resetcounter);
  
  extern void pgstat_report_recovery_conflict(int reason);
  extern void pgstat_report_deadlock(void);
  extern void pgstat_report_checksum_failures_in_db(Oid dboid, int failurecount);
  extern void pgstat_report_checksum_failure(void);
  extern void pgstat_report_replslot(const char *slotname, int spilltxns, int spillcount,
  								   int spillbytes);
  extern void pgstat_report_replslot_drop(const char *slotname);
  
  extern void pgstat_initialize(void);
  extern void pgstat_bestart(void);
  
  extern void pgstat_report_activity(BackendState state, const char *cmd_str);
  extern void pgstat_report_tempfile(size_t filesize);
  extern void pgstat_report_appname(const char *appname);
  extern void pgstat_report_xact_timestamp(TimestampTz tstamp);
  extern const char *pgstat_get_wait_event(uint32 wait_event_info);
  extern const char *pgstat_get_wait_event_type(uint32 wait_event_info);
  extern const char *pgstat_get_backend_current_activity(int pid, bool checkUser);
  extern const char *pgstat_get_crashed_backend_activity(int pid, char *buffer,
  													   int buflen);
  
  extern void pgstat_progress_start_command(ProgressCommandType cmdtype,
  										  Oid relid);
  extern void pgstat_progress_update_param(int index, int64 val);
  extern void pgstat_progress_update_multi_param(int nparam, const int *index,
  											   const int64 *val);
  extern void pgstat_progress_end_command(void);
  
  extern PgStat_TableStatus *find_tabstat_entry(Oid rel_id);
  extern PgStat_BackendFunctionEntry *find_funcstat_entry(Oid func_id);
  
  extern void pgstat_initstats(Relation rel);
  
  extern char *pgstat_clip_activity(const char *raw_activity);
  
  /* ----------
   * pgstat_report_wait_start() -
   *
   *	Called from places where server process needs to wait.  This is called
   *	to report wait event information.  The wait information is stored
   *	as 4-bytes where first byte represents the wait event class (type of
   *	wait, for different types of wait, refer WaitClass) and the next
   *	3-bytes represent the actual wait event.  Currently 2-bytes are used
   *	for wait event which is sufficient for current usage, 1-byte is
   *	reserved for future usage.
   *
   * NB: this *must* be able to survive being called before MyProc has been
   * initialized.
   * ----------
   */
  static inline void
  pgstat_report_wait_start(uint32 wait_event_info)
  {
  	volatile PGPROC *proc = MyProc;
  
  	if (!pgstat_track_activities || !proc)
  		return;
  
  	/*
  	 * Since this is a four-byte field which is always read and written as
  	 * four-bytes, updates are atomic.
  	 */
  	proc->wait_event_info = wait_event_info;
  }
  
  /* ----------
   * pgstat_report_wait_end() -
   *
   *	Called to report end of a wait.
   *
   * NB: this *must* be able to survive being called before MyProc has been
   * initialized.
   * ----------
   */
  static inline void
  pgstat_report_wait_end(void)
  {
  	volatile PGPROC *proc = MyProc;
  
  	if (!pgstat_track_activities || !proc)
  		return;
  
  	/*
  	 * Since this is a four-byte field which is always read and written as
  	 * four-bytes, updates are atomic.
  	 */
  	proc->wait_event_info = 0;
  }
  
  /* nontransactional event counts are simple enough to inline */
  
  #define pgstat_count_heap_scan(rel)									\
  	do {															\
  		if ((rel)->pgstat_info != NULL)								\
  			(rel)->pgstat_info->t_counts.t_numscans++;				\
  	} while (0)
  #define pgstat_count_heap_getnext(rel)								\
  	do {															\
  		if ((rel)->pgstat_info != NULL)								\
  			(rel)->pgstat_info->t_counts.t_tuples_returned++;		\
  	} while (0)
  #define pgstat_count_heap_fetch(rel)								\
  	do {															\
  		if ((rel)->pgstat_info != NULL)								\
  			(rel)->pgstat_info->t_counts.t_tuples_fetched++;		\
  	} while (0)
  #define pgstat_count_index_scan(rel)								\
  	do {															\
  		if ((rel)->pgstat_info != NULL)								\
  			(rel)->pgstat_info->t_counts.t_numscans++;				\
  	} while (0)
  #define pgstat_count_index_tuples(rel, n)							\
  	do {															\
  		if ((rel)->pgstat_info != NULL)								\
  			(rel)->pgstat_info->t_counts.t_tuples_returned += (n);	\
  	} while (0)
  #define pgstat_count_buffer_read(rel)								\
  	do {															\
  		if ((rel)->pgstat_info != NULL)								\
  			(rel)->pgstat_info->t_counts.t_blocks_fetched++;		\
  	} while (0)
  #define pgstat_count_buffer_hit(rel)								\
  	do {															\
  		if ((rel)->pgstat_info != NULL)								\
  			(rel)->pgstat_info->t_counts.t_blocks_hit++;			\
  	} while (0)
  #define pgstat_count_buffer_read_time(n)							\
  	(pgStatBlockReadTime += (n))
  #define pgstat_count_buffer_write_time(n)							\
  	(pgStatBlockWriteTime += (n))
  
  extern void pgstat_count_heap_insert(Relation rel, PgStat_Counter n);
  extern void pgstat_count_heap_update(Relation rel, bool hot);
  extern void pgstat_count_heap_delete(Relation rel);
  extern void pgstat_count_truncate(Relation rel);
  extern void pgstat_update_heap_dead_tuples(Relation rel, int delta);
  
  struct FunctionCallInfoBaseData;
  extern void pgstat_init_function_usage(struct FunctionCallInfoBaseData *fcinfo,
  									   PgStat_FunctionCallUsage *fcu);
  extern void pgstat_end_function_usage(PgStat_FunctionCallUsage *fcu,
  									  bool finalize);
  
  extern void AtEOXact_PgStat(bool isCommit, bool parallel);
  extern void AtEOSubXact_PgStat(bool isCommit, int nestDepth);
  
  extern void AtPrepare_PgStat(void);
  extern void PostPrepare_PgStat(void);
  
  extern void pgstat_twophase_postcommit(TransactionId xid, uint16 info,
  									   void *recdata, uint32 len);
  extern void pgstat_twophase_postabort(TransactionId xid, uint16 info,
  									  void *recdata, uint32 len);
  
  extern void pgstat_send_archiver(const char *xlog, bool failed);
  extern void pgstat_send_bgwriter(void);
  extern void pgstat_send_wal(void);
  
  /* ----------
   * Support functions for the SQL-callable functions to
   * generate the pgstat* views.
   * ----------
   */
  extern PgStat_StatDBEntry *pgstat_fetch_stat_dbentry(Oid dbid);
  extern PgStat_StatTabEntry *pgstat_fetch_stat_tabentry(Oid relid);
  extern PgBackendStatus *pgstat_fetch_stat_beentry(int beid);
  extern LocalPgBackendStatus *pgstat_fetch_stat_local_beentry(int beid);
  extern PgStat_StatFuncEntry *pgstat_fetch_stat_funcentry(Oid funcid);
  extern int	pgstat_fetch_stat_numbackends(void);
  extern PgStat_ArchiverStats *pgstat_fetch_stat_archiver(void);
  extern PgStat_GlobalStats *pgstat_fetch_global(void);
  extern PgStat_WalStats *pgstat_fetch_stat_wal(void);
  extern PgStat_SLRUStats *pgstat_fetch_slru(void);
  extern PgStat_ReplSlotStats *pgstat_fetch_replslot(int *nslots_p);
  
  extern void pgstat_count_slru_page_zeroed(int slru_idx);
  extern void pgstat_count_slru_page_hit(int slru_idx);
  extern void pgstat_count_slru_page_read(int slru_idx);
  extern void pgstat_count_slru_page_written(int slru_idx);
  extern void pgstat_count_slru_page_exists(int slru_idx);
  extern void pgstat_count_slru_flush(int slru_idx);
  extern void pgstat_count_slru_truncate(int slru_idx);
  extern const char *pgstat_slru_name(int slru_idx);
  extern int	pgstat_slru_index(const char *name);
  
  #endif							/* PGSTAT_H */
  