text: /*-------------------------------------------------------------------------
   *
   * postgres.c
   *	  POSTGRES C Backend Interface
   *
   * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.468.2.3 2005/12/14 17:06:37 tgl Exp $
   *
   * NOTES
   *	  this is the "main" module of the postgres backend and
   *	  hence the main module of the "traffic cop".
   *
   *-------------------------------------------------------------------------
   */
  
  #include "postgres.h"
  
  #include <unistd.h>
  #include <signal.h>
  #include <fcntl.h>
  #include <sys/socket.h>
  #if HAVE_SYS_SELECT_H
  #include <sys/select.h>
  #endif
  #ifdef HAVE_GETOPT_H
  #include <getopt.h>
  #endif
  
  #include "access/printtup.h"
  #include "access/xlog.h"
  #include "catalog/pg_type.h"
  #include "commands/async.h"
  #include "commands/prepare.h"
  #include "commands/trigger.h"
  #include "libpq/libpq.h"
  #include "libpq/pqformat.h"
  #include "libpq/pqsignal.h"
  #include "miscadmin.h"
  #include "nodes/print.h"
  #include "optimizer/cost.h"
  #include "optimizer/planner.h"
  #include "parser/analyze.h"
  #include "parser/parser.h"
  #include "rewrite/rewriteHandler.h"
  #include "storage/freespace.h"
  #include "storage/ipc.h"
  #include "storage/pg_shmem.h"
  #include "storage/proc.h"
  #include "storage/sinval.h"
  #include "tcop/fastpath.h"
  #include "tcop/pquery.h"
  #include "tcop/tcopprot.h"
  #include "tcop/utility.h"
  #include "utils/flatfiles.h"
  #include "utils/guc.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/ps_status.h"
  #include "mb/pg_wchar.h"
  
  #include "pgstat.h"
  
  extern int	optind;
  extern char *optarg;
  
  /* ----------------
   *		global variables
   * ----------------
   */
  const char *debug_query_string; /* for pgmonitor and log_min_error_statement */
  
  /* Note: whereToSendOutput is initialized for the bootstrap/standalone case */
  CommandDest whereToSendOutput = DestDebug;
  
  /* flag for logging end of session */
  bool		Log_disconnections = false;
  
  LogStmtLevel log_statement = LOGSTMT_NONE;
  
  /* GUC variable for maximum stack depth (measured in kilobytes) */
  int			max_stack_depth = 2048;
  
  
  /* ----------------
   *		private variables
   * ----------------
   */
  
  /* max_stack_depth converted to bytes for speed of checking */
  static int	max_stack_depth_bytes = 2048 * 1024;
  
  /* stack base pointer (initialized by PostgresMain) */
  /* Do not make static so PL/Java can modifiy it */
  char	   *stack_base_ptr = NULL;
  
  
  /*
   * Flag to mark SIGHUP. Whenever the main loop comes around it
   * will reread the configuration file. (Better than doing the
   * reading in the signal handler, ey?)
   */
  static volatile sig_atomic_t got_SIGHUP = false;
  
  /*
   * Flag to keep track of whether we have started a transaction.
   * For extended query protocol this has to be remembered across messages.
   */
  static bool xact_started = false;
  
  /*
   * Flag to indicate that we are doing the outer loop's read-from-client,
   * as opposed to any random read from client that might happen within
   * commands like COPY FROM STDIN.
   */
  static bool DoingCommandRead = false;
  
  /*
   * Flags to implement skip-till-Sync-after-error behavior for messages of
   * the extended query protocol.
   */
  static bool doing_extended_query_message = false;
  static bool ignore_till_sync = false;
  
  /*
   * If an unnamed prepared statement exists, it's stored here.
   * We keep it separate from the hashtable kept by commands/prepare.c
   * in order to reduce overhead for short-lived queries.
   */
  static MemoryContext unnamed_stmt_context = NULL;
  static PreparedStatement *unnamed_stmt_pstmt = NULL;
  
  
  static bool EchoQuery = false;	/* default don't echo */
  
  /*
   * people who want to use EOF should #define DONTUSENEWLINE in
   * tcop/tcopdebug.h
   */
  #ifndef TCOP_DONTUSENEWLINE
  static int	UseNewLine = 1;		/* Use newlines query delimiters (the default) */
  #else
  static int	UseNewLine = 0;		/* Use EOF as query delimiters */
  #endif   /* TCOP_DONTUSENEWLINE */
  
  
  /* ----------------------------------------------------------------
   *		decls for routines only used in this file
   * ----------------------------------------------------------------
   */
  static int	InteractiveBackend(StringInfo inBuf);
  static int	SocketBackend(StringInfo inBuf);
  static int	ReadCommand(StringInfo inBuf);
  static bool log_after_parse(List *raw_parsetree_list,
  				const char *query_string, char **prepare_string);
  static List *pg_rewrite_queries(List *querytree_list);
  static void start_xact_command(void);
  static void finish_xact_command(void);
  static bool IsTransactionExitStmt(Node *parsetree);
  static bool IsTransactionExitStmtList(List *parseTrees);
  static bool IsTransactionStmtList(List *parseTrees);
  static void SigHupHandler(SIGNAL_ARGS);
  static void log_disconnections(int code, Datum arg);
  
  
  /* ----------------------------------------------------------------
   *		routines to obtain user input
   * ----------------------------------------------------------------
   */
  
  /* ----------------
   *	InteractiveBackend() is called for user interactive connections
   *
   *	the string entered by the user is placed in its parameter inBuf,
   *	and we act like a Q message was received.
   *
   *	EOF is returned if end-of-file input is seen; time to shut down.
   * ----------------
   */
  
  static int
  InteractiveBackend(StringInfo inBuf)
  {
  	int			c;				/* character read from getc() */
  	bool		end = false;	/* end-of-input flag */
  	bool		backslashSeen = false;	/* have we seen a \ ? */
  
  	/*
  	 * display a prompt and obtain input from the user
  	 */
  	printf("backend> ");
  	fflush(stdout);
  
  	/* Reset inBuf to empty */
  	inBuf->len = 0;
  	inBuf->data[0] = '\0';
  	inBuf->cursor = 0;
  
  	for (;;)
  	{
  		if (UseNewLine)
  		{
  			/*
  			 * if we are using \n as a delimiter, then read characters until
  			 * the \n.
  			 */
  			while ((c = getc(stdin)) != EOF)
  			{
  				if (c == '\n')
  				{
  					if (backslashSeen)
  					{
  						/* discard backslash from inBuf */
  						inBuf->data[--inBuf->len] = '\0';
  						backslashSeen = false;
  						continue;
  					}
  					else
  					{
  						/* keep the newline character */
  						appendStringInfoChar(inBuf, '\n');
  						break;
  					}
  				}
  				else if (c == '\\')
  					backslashSeen = true;
  				else
  					backslashSeen = false;
  
  				appendStringInfoChar(inBuf, (char) c);
  			}
  
  			if (c == EOF)
  				end = true;
  		}
  		else
  		{
  			/*
  			 * otherwise read characters until EOF.
  			 */
  			while ((c = getc(stdin)) != EOF)
  				appendStringInfoChar(inBuf, (char) c);
  
  			if (inBuf->len == 0)
  				end = true;
  		}
  
  		if (end)
  			return EOF;
  
  		/*
  		 * otherwise we have a user query so process it.
  		 */
  		break;
  	}
  
  	/* Add '\0' to make it look the same as message case. */
  	appendStringInfoChar(inBuf, (char) '\0');
  
  	/*
  	 * if the query echo flag was given, print the query..
  	 */
  	if (EchoQuery)
  		printf("statement: %s\n", inBuf->data);
  	fflush(stdout);
  
  	return 'Q';
  }
  
  /* ----------------
   *	SocketBackend()		Is called for frontend-backend connections
   *
   *	Returns the message type code, and loads message body data into inBuf.
   *
   *	EOF is returned if the connection is lost.
   * ----------------
   */
  static int
  SocketBackend(StringInfo inBuf)
  {
  	int			qtype;
  
  	/*
  	 * Get message type code from the frontend.
  	 */
  	qtype = pq_getbyte();
  
  	if (qtype == EOF)			/* frontend disconnected */
  	{
  		ereport(COMMERROR,
  				(errcode(ERRCODE_PROTOCOL_VIOLATION),
  				 errmsg("unexpected EOF on client connection")));
  		return qtype;
  	}
  
  	/*
  	 * Validate message type code before trying to read body; if we have lost
  	 * sync, better to say "command unknown" than to run out of memory because
  	 * we used garbage as a length word.
  	 *
  	 * This also gives us a place to set the doing_extended_query_message flag
  	 * as soon as possible.
  	 */
  	switch (qtype)
  	{
  		case 'Q':				/* simple query */
  			doing_extended_query_message = false;
  			if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
  			{
  				/* old style without length word; convert */
  				if (pq_getstring(inBuf))
  				{
  					ereport(COMMERROR,
  							(errcode(ERRCODE_PROTOCOL_VIOLATION),
  							 errmsg("unexpected EOF on client connection")));
  					return EOF;
  				}
  			}
  			break;
  
  		case 'F':				/* fastpath function call */
  			/* we let fastpath.c cope with old-style input of this */
  			doing_extended_query_message = false;
  			break;
  
  		case 'X':				/* terminate */
  			doing_extended_query_message = false;
  			ignore_till_sync = false;
  			break;
  
  		case 'B':				/* bind */
  		case 'C':				/* close */
  		case 'D':				/* describe */
  		case 'E':				/* execute */
  		case 'H':				/* flush */
  		case 'P':				/* parse */
  			doing_extended_query_message = true;
  			/* these are only legal in protocol 3 */
  			if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
  				ereport(FATAL,
  						(errcode(ERRCODE_PROTOCOL_VIOLATION),
  						 errmsg("invalid frontend message type %d", qtype)));
  			break;
  
  		case 'S':				/* sync */
  			/* stop any active skip-till-Sync */
  			ignore_till_sync = false;
  			/* mark not-extended, so that a new error doesn't begin skip */
  			doing_extended_query_message = false;
  			/* only legal in protocol 3 */
  			if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
  				ereport(FATAL,
  						(errcode(ERRCODE_PROTOCOL_VIOLATION),
  						 errmsg("invalid frontend message type %d", qtype)));
  			break;
  
  		case 'd':				/* copy data */
  		case 'c':				/* copy done */
  		case 'f':				/* copy fail */
  			doing_extended_query_message = false;
  			/* these are only legal in protocol 3 */
  			if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
  				ereport(FATAL,
  						(errcode(ERRCODE_PROTOCOL_VIOLATION),
  						 errmsg("invalid frontend message type %d", qtype)));
  			break;
  
  		default:
  
  			/*
  			 * Otherwise we got garbage from the frontend.	We treat this as
  			 * fatal because we have probably lost message boundary sync, and
  			 * there's no good way to recover.
  			 */
  			ereport(FATAL,
  					(errcode(ERRCODE_PROTOCOL_VIOLATION),
  					 errmsg("invalid frontend message type %d", qtype)));
  			break;
  	}
  
  	/*
  	 * In protocol version 3, all frontend messages have a length word next
  	 * after the type code; we can read the message contents independently of
  	 * the type.
  	 */
  	if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
  	{
  		if (pq_getmessage(inBuf, 0))
  			return EOF;			/* suitable message already logged */
  	}
  
  	return qtype;
  }
  
  /* ----------------
   *		ReadCommand reads a command from either the frontend or
   *		standard input, places it in inBuf, and returns the
   *		message type code (first byte of the message).
   *		EOF is returned if end of file.
   * ----------------
   */
  static int
  ReadCommand(StringInfo inBuf)
  {
  	int			result;
  
  	if (whereToSendOutput == DestRemote)
  		result = SocketBackend(inBuf);
  	else
  		result = InteractiveBackend(inBuf);
  	return result;
  }
  
  /*
   * prepare_for_client_read -- set up to possibly block on client input
   *
   * This must be called immediately before any low-level read from the
   * client connection.  It is necessary to do it at a sufficiently low level
   * that there won't be any other operations except the read kernel call
   * itself between this call and the subsequent client_read_ended() call.
   * In particular there mustn't be use of malloc() or other potentially
   * non-reentrant libc functions.  This restriction makes it safe for us
   * to allow interrupt service routines to execute nontrivial code while
   * we are waiting for input.
   */
  void
  prepare_for_client_read(void)
  {
  	if (DoingCommandRead)
  	{
  		/* Enable immediate processing of asynchronous signals */
  		EnableNotifyInterrupt();
  		EnableCatchupInterrupt();
  
  		/* Allow "die" interrupt to be processed while waiting */
  		ImmediateInterruptOK = true;
  
  		/* And don't forget to detect one that already arrived */
  		QueryCancelPending = false;
  		CHECK_FOR_INTERRUPTS();
  	}
  }
  
  /*
   * client_read_ended -- get out of the client-input state
   */
  void
  client_read_ended(void)
  {
  	if (DoingCommandRead)
  	{
  		ImmediateInterruptOK = false;
  		QueryCancelPending = false;		/* forget any CANCEL signal */
  
  		DisableNotifyInterrupt();
  		DisableCatchupInterrupt();
  	}
  }
  
  
  /*
   * Parse a query string and pass it through the rewriter.
   *
   * A list of Query nodes is returned, since the string might contain
   * multiple queries and/or the rewriter might expand one query to several.
   *
   * NOTE: this routine is no longer used for processing interactive queries,
   * but it is still needed for parsing of SQL function bodies.
   */
  List *
  pg_parse_and_rewrite(const char *query_string,	/* string to execute */
  					 Oid *paramTypes,	/* parameter types */
  					 int numParams)		/* number of parameters */
  {
  	List	   *raw_parsetree_list;
  	List	   *querytree_list;
  	ListCell   *list_item;
  
  	/*
  	 * (1) parse the request string into a list of raw parse trees.
  	 */
  	raw_parsetree_list = pg_parse_query(query_string);
  
  	/*
  	 * (2) Do parse analysis and rule rewrite.
  	 */
  	querytree_list = NIL;
  	foreach(list_item, raw_parsetree_list)
  	{
  		Node	   *parsetree = (Node *) lfirst(list_item);
  
  		querytree_list = list_concat(querytree_list,
  									 pg_analyze_and_rewrite(parsetree,
  															paramTypes,
  															numParams));
  	}
  
  	return querytree_list;
  }
  
  /*
   * Do raw parsing (only).
   *
   * A list of parsetrees is returned, since there might be multiple
   * commands in the given string.
   *
   * NOTE: for interactive queries, it is important to keep this routine
   * separate from the analysis & rewrite stages.  Analysis and rewriting
   * cannot be done in an aborted transaction, since they require access to
   * database tables.  So, we rely on the raw parser to determine whether
   * we've seen a COMMIT or ABORT command; when we are in abort state, other
   * commands are not processed any further than the raw parse stage.
   */
  List *
  pg_parse_query(const char *query_string)
  {
  	List	   *raw_parsetree_list;
  
  	if (log_parser_stats)
  		ResetUsage();
  
  	raw_parsetree_list = raw_parser(query_string);
  
  	if (log_parser_stats)
  		ShowUsage("PARSER STATISTICS");
  
  	return raw_parsetree_list;
  }
  
  static bool
  log_after_parse(List *raw_parsetree_list, const char *query_string,
  				char **prepare_string)
  {
  	ListCell   *parsetree_item;
  	bool		log_this_statement = (log_statement == LOGSTMT_ALL);
  
  	*prepare_string = NULL;
  
  	/* Check if we need to log the statement, and get prepare_string. */
  	foreach(parsetree_item, raw_parsetree_list)
  	{
  		Node	   *parsetree = (Node *) lfirst(parsetree_item);
  		const char *commandTag;
  
  		if (IsA(parsetree, ExplainStmt) &&
  			((ExplainStmt *) parsetree)->analyze)
  			parsetree = (Node *) (((ExplainStmt *) parsetree)->query);
  
  		if (IsA(parsetree, PrepareStmt))
  			parsetree = (Node *) (((PrepareStmt *) parsetree)->query);
  
  		if (IsA(parsetree, SelectStmt) &&
  			((SelectStmt *) parsetree)->into == NULL)
  			continue;			/* optimization for frequent command */
  
  		if (log_statement == LOGSTMT_MOD &&
  			(IsA(parsetree, InsertStmt) ||
  			 IsA(parsetree, UpdateStmt) ||
  			 IsA(parsetree, DeleteStmt) ||
  			 IsA(parsetree, TruncateStmt) ||
  			 (IsA(parsetree, CopyStmt) &&
  			  ((CopyStmt *) parsetree)->is_from)))		/* COPY FROM */
  			log_this_statement = true;
  
  		commandTag = CreateCommandTag(parsetree);
  		if ((log_statement == LOGSTMT_MOD ||
  			 log_statement == LOGSTMT_DDL) &&
  			(strncmp(commandTag, "CREATE ", strlen("CREATE ")) == 0 ||
  			 IsA(parsetree, SelectStmt) ||		/* SELECT INTO, CREATE AS */
  			 strncmp(commandTag, "ALTER ", strlen("ALTER ")) == 0 ||
  			 strncmp(commandTag, "DROP ", strlen("DROP ")) == 0 ||
  			 IsA(parsetree, GrantStmt) ||		/* GRANT or REVOKE */
  			 IsA(parsetree, CommentStmt)))
  			log_this_statement = true;
  
  		/*
  		 * For the first EXECUTE we find, record the client statement used by
  		 * the PREPARE.
  		 */
  		if (IsA(parsetree, ExecuteStmt))
  		{
  			ExecuteStmt *stmt = (ExecuteStmt *) parsetree;
  			PreparedStatement *entry;
  
  			if ((entry = FetchPreparedStatement(stmt->name, false)) != NULL &&
  				entry->query_string)
  			{
  				*prepare_string = palloc(strlen(entry->query_string) +
  									  strlen("  [client PREPARE:  %s]") - 1);
  				sprintf(*prepare_string, "  [client PREPARE:  %s]",
  						entry->query_string);
  			}
  		}
  	}
  
  	if (log_this_statement)
  	{
  		ereport(LOG,
  				(errmsg("statement: %s%s", query_string,
  						*prepare_string ? *prepare_string : "")));
  		return true;
  	}
  	else
  		return false;
  }
  
  
  /*
   * Given a raw parsetree (gram.y output), and optionally information about
   * types of parameter symbols ($n), perform parse analysis and rule rewriting.
   *
   * A list of Query nodes is returned, since either the analyzer or the
   * rewriter might expand one query to several.
   *
   * NOTE: for reasons mentioned above, this must be separate from raw parsing.
   */
  List *
  pg_analyze_and_rewrite(Node *parsetree, Oid *paramTypes, int numParams)
  {
  	List	   *querytree_list;
  
  	/*
  	 * (1) Perform parse analysis.
  	 */
  	if (log_parser_stats)
  		ResetUsage();
  
  	querytree_list = parse_analyze(parsetree, paramTypes, numParams);
  
  	if (log_parser_stats)
  		ShowUsage("PARSE ANALYSIS STATISTICS");
  
  	/*
  	 * (2) Rewrite the queries, as necessary
  	 */
  	querytree_list = pg_rewrite_queries(querytree_list);
  
  	return querytree_list;
  }
  
  /*
   * Perform rewriting of a list of queries produced by parse analysis.
   *
   * Note: queries must just have come from the parser, because we do not do
   * AcquireRewriteLocks() on them.
   */
  static List *
  pg_rewrite_queries(List *querytree_list)
  {
  	List	   *new_list = NIL;
  	ListCell   *list_item;
  
  	if (log_parser_stats)
  		ResetUsage();
  
  	/*
  	 * rewritten queries are collected in new_list.  Note there may be more or
  	 * fewer than in the original list.
  	 */
  	foreach(list_item, querytree_list)
  	{
  		Query	   *querytree = (Query *) lfirst(list_item);
  
  		if (Debug_print_parse)
  			elog_node_display(DEBUG1, "parse tree", querytree,
  							  Debug_pretty_print);
  
  		if (querytree->commandType == CMD_UTILITY)
  		{
  			/* don't rewrite utilities, just dump 'em into new_list */
  			new_list = lappend(new_list, querytree);
  		}
  		else
  		{
  			/* rewrite regular queries */
  			List	   *rewritten = QueryRewrite(querytree);
  
  			new_list = list_concat(new_list, rewritten);
  		}
  	}
  
  	querytree_list = new_list;
  
  	if (log_parser_stats)
  		ShowUsage("REWRITER STATISTICS");
  
  #ifdef COPY_PARSE_PLAN_TREES
  
  	/*
  	 * Optional debugging check: pass querytree output through copyObject()
  	 */
  	new_list = (List *) copyObject(querytree_list);
  	/* This checks both copyObject() and the equal() routines... */
  	if (!equal(new_list, querytree_list))
  		elog(WARNING, "copyObject() failed to produce an equal parse tree");
  	else
  		querytree_list = new_list;
  #endif
  
  	if (Debug_print_rewritten)
  		elog_node_display(DEBUG1, "rewritten parse tree", querytree_list,
  						  Debug_pretty_print);
  
  	return querytree_list;
  }
  
  
  /* Generate a plan for a single already-rewritten query. */
  Plan *
  pg_plan_query(Query *querytree, ParamListInfo boundParams)
  {
  	Plan	   *plan;
  
  	/* Utility commands have no plans. */
  	if (querytree->commandType == CMD_UTILITY)
  		return NULL;
  
  	if (log_planner_stats)
  		ResetUsage();
  
  	/* call the optimizer */
  	plan = planner(querytree, false, 0, boundParams);
  
  	if (log_planner_stats)
  		ShowUsage("PLANNER STATISTICS");
  
  #ifdef COPY_PARSE_PLAN_TREES
  	/* Optional debugging check: pass plan output through copyObject() */
  	{
  		Plan	   *new_plan = (Plan *) copyObject(plan);
  
  		/*
  		 * equal() currently does not have routines to compare Plan nodes, so
  		 * don't try to test equality here.  Perhaps fix someday?
  		 */
  #ifdef NOT_USED
  		/* This checks both copyObject() and the equal() routines... */
  		if (!equal(new_plan, plan))
  			elog(WARNING, "copyObject() failed to produce an equal plan tree");
  		else
  #endif
  			plan = new_plan;
  	}
  #endif
  
  	/*
  	 * Print plan if debugging.
  	 */
  	if (Debug_print_plan)
  		elog_node_display(DEBUG1, "plan", plan, Debug_pretty_print);
  
  	return plan;
  }
  
  /*
   * Generate plans for a list of already-rewritten queries.
   *
   * If needSnapshot is TRUE, we haven't yet set a snapshot for the current
   * query.  A snapshot must be set before invoking the planner, since it
   * might try to evaluate user-defined functions.  But we must not set a
   * snapshot if the list contains only utility statements, because some
   * utility statements depend on not having frozen the snapshot yet.
   * (We assume that such statements cannot appear together with plannable
   * statements in the rewriter's output.)
   */
  List *
  pg_plan_queries(List *querytrees, ParamListInfo boundParams,
  				bool needSnapshot)
  {
  	List	   *plan_list = NIL;
  	ListCell   *query_list;
  
  	foreach(query_list, querytrees)
  	{
  		Query	   *query = (Query *) lfirst(query_list);
  		Plan	   *plan;
  
  		if (query->commandType == CMD_UTILITY)
  		{
  			/* Utility commands have no plans. */
  			plan = NULL;
  		}
  		else
  		{
  			if (needSnapshot)
  			{
  				ActiveSnapshot = CopySnapshot(GetTransactionSnapshot());
  				needSnapshot = false;
  			}
  			plan = pg_plan_query(query, boundParams);
  		}
  
  		plan_list = lappend(plan_list, plan);
  	}
  
  	return plan_list;
  }
  
  
  /*
   * exec_simple_query
   *
   * Execute a "simple Query" protocol message.
   */
  static void
  exec_simple_query(const char *query_string)
  {
  	CommandDest dest = whereToSendOutput;
  	MemoryContext oldcontext;
  	List	   *parsetree_list;
  	ListCell   *parsetree_item;
  	struct timeval start_t,
  				stop_t;
  	bool		save_log_duration = log_duration;
  	int			save_log_min_duration_statement = log_min_duration_statement;
  	bool		save_log_statement_stats = log_statement_stats;
  	char	   *prepare_string = NULL;
  	bool		was_logged = false;
  
  	/*
  	 * Report query to various monitoring facilities.
  	 */
  	debug_query_string = query_string;
  
  	pgstat_report_activity(query_string);
  
  	/*
  	 * We use save_log_* so "SET log_duration = true"  and "SET
  	 * log_min_duration_statement = true" don't report incorrect time because
  	 * gettimeofday() wasn't called. Similarly, log_statement_stats has to be
  	 * captured once.
  	 */
  	if (save_log_duration || save_log_min_duration_statement != -1)
  		gettimeofday(&start_t, NULL);
  
  	if (save_log_statement_stats)
  		ResetUsage();
  
  	/*
  	 * Start up a transaction command.	All queries generated by the
  	 * query_string will be in this same command block, *unless* we find a
  	 * BEGIN/COMMIT/ABORT statement; we have to force a new xact command after
  	 * one of those, else bad things will happen in xact.c. (Note that this
  	 * will normally change current memory context.)
  	 */
  	start_xact_command();
  
  	/*
  	 * Zap any pre-existing unnamed statement.	(While not strictly necessary,
  	 * it seems best to define simple-Query mode as if it used the unnamed
  	 * statement and portal; this ensures we recover any storage used by prior
  	 * unnamed operations.)
  	 */
  	unnamed_stmt_pstmt = NULL;
  	if (unnamed_stmt_context)
  	{
  		DropDependentPortals(unnamed_stmt_context);
  		MemoryContextDelete(unnamed_stmt_context);
  	}
  	unnamed_stmt_context = NULL;
  
  	/*
  	 * Switch to appropriate context for constructing parsetrees.
  	 */
  	oldcontext = MemoryContextSwitchTo(MessageContext);
  
  	QueryContext = CurrentMemoryContext;
  
  	/*
  	 * Do basic parsing of the query or queries (this should be safe even if
  	 * we are in aborted transaction state!)
  	 */
  	parsetree_list = pg_parse_query(query_string);
  
  	if (log_statement != LOGSTMT_NONE || save_log_min_duration_statement != -1)
  		was_logged = log_after_parse(parsetree_list, query_string,
  									 &prepare_string);
  
  	/*
  	 * Switch back to transaction context to enter the loop.
  	 */
  	MemoryContextSwitchTo(oldcontext);
  
  	/*
  	 * Run through the raw parsetree(s) and process each one.
  	 */
  	foreach(parsetree_item, parsetree_list)
  	{
  		Node	   *parsetree = (Node *) lfirst(parsetree_item);
  		const char *commandTag;
  		char		completionTag[COMPLETION_TAG_BUFSIZE];
  		List	   *querytree_list,
  				   *plantree_list;
  		Portal		portal;
  		DestReceiver *receiver;
  		int16		format;
  
  		/*
  		 * Get the command name for use in status display (it also becomes the
  		 * default completion tag, down inside PortalRun).	Set ps_status and
  		 * do any special start-of-SQL-command processing needed by the
  		 * destination.
  		 */
  		commandTag = CreateCommandTag(parsetree);
  
  		set_ps_display(commandTag);
  
  		BeginCommand(commandTag, dest);
  
  		/*
  		 * If we are in an aborted transaction, reject all commands except
  		 * COMMIT/ABORT.  It is important that this test occur before we try
  		 * to do parse analysis, rewrite, or planning, since all those phases
  		 * try to do database accesses, which may fail in abort state. (It
  		 * might be safe to allow some additional utility commands in this
  		 * state, but not many...)
  		 */
  		if (IsAbortedTransactionBlockState() &&
  			!IsTransactionExitStmt(parsetree))
  			ereport(ERROR,
  					(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
  					 errmsg("current transaction is aborted, "
  						"commands ignored until end of transaction block")));
  
  		/* Make sure we are in a transaction command */
  		start_xact_command();
  
  		/* If we got a cancel signal in parsing or prior command, quit */
  		CHECK_FOR_INTERRUPTS();
  
  		/*
  		 * OK to analyze, rewrite, and plan this query.
  		 *
  		 * Switch to appropriate context for constructing querytrees (again,
  		 * these must outlive the execution context).
  		 */
  		oldcontext = MemoryContextSwitchTo(MessageContext);
  
  		querytree_list = pg_analyze_and_rewrite(parsetree, NULL, 0);
  
  		plantree_list = pg_plan_queries(querytree_list, NULL, true);
  
  		/* If we got a cancel signal in analysis or planning, quit */
  		CHECK_FOR_INTERRUPTS();
  
  		/*
  		 * Create unnamed portal to run the query or queries in. If there
  		 * already is one, silently drop it.
  		 */
  		portal = CreatePortal("", true, true);
  
  		PortalDefineQuery(portal,
  						  query_string,
  						  commandTag,
  						  querytree_list,
  						  plantree_list,
  						  MessageContext);
  
  		/*
  		 * Start the portal.  No parameters here.
  		 */
  		PortalStart(portal, NULL, InvalidSnapshot);
  
  		/*
  		 * Select the appropriate output format: text unless we are doing a
  		 * FETCH from a binary cursor.	(Pretty grotty to have to do this here
  		 * --- but it avoids grottiness in other places.  Ah, the joys of
  		 * backward compatibility...)
  		 */
  		format = 0;				/* TEXT is default */
  		if (IsA(parsetree, FetchStmt))
  		{
  			FetchStmt  *stmt = (FetchStmt *) parsetree;
  
  			if (!stmt->ismove)
  			{
  				Portal		fportal = GetPortalByName(stmt->portalname);
  
  				if (PortalIsValid(fportal) &&
  					(fportal->cursorOptions & CURSOR_OPT_BINARY))
  					format = 1; /* BINARY */
  			}
  		}
  		PortalSetResultFormat(portal, 1, &format);
  
  		/*
  		 * Now we can create the destination receiver object.
  		 */
  		receiver = CreateDestReceiver(dest, portal);
  
  		/*
  		 * Switch back to transaction context for execution.
  		 */
  		MemoryContextSwitchTo(oldcontext);
  
  		/*
  		 * Run the portal to completion, and then drop it (and the receiver).
  		 */
  		(void) PortalRun(portal,
  						 FETCH_ALL,
  						 receiver,
  						 receiver,
  						 completionTag);
  
  		(*receiver->rDestroy) (receiver);
  
  		PortalDrop(portal, false);
  
  		if (IsA(parsetree, TransactionStmt))
  		{
  			/*
  			 * If this was a transaction control statement, commit it. We will
  			 * start a new xact command for the next command (if any).
  			 */
  			finish_xact_command();
  		}
  		else if (lnext(parsetree_item) == NULL)
  		{
  			/*
  			 * If this is the last parsetree of the query string, close down
  			 * transaction statement before reporting command-complete.  This
  			 * is so that any end-of-transaction errors are reported before
  			 * the command-complete message is issued, to avoid confusing
  			 * clients who will expect either a command-complete message or an
  			 * error, not one and then the other.  But for compatibility with
  			 * historical Postgres behavior, we do not force a transaction
  			 * boundary between queries appearing in a single query string.
  			 */
  			finish_xact_command();
  		}
  		else
  		{
  			/*
  			 * We need a CommandCounterIncrement after every query, except
  			 * those that start or end a transaction block.
  			 */
  			CommandCounterIncrement();
  		}
  
  		/*
  		 * Tell client that we're done with this query.  Note we emit exactly
  		 * one EndCommand report for each raw parsetree, thus one for each SQL
  		 * command the client sent, regardless of rewriting. (But a command
  		 * aborted by error will not send an EndCommand report at all.)
  		 */
  		EndCommand(completionTag, dest);
  	}							/* end loop over parsetrees */
  
  	/*
  	 * Close down transaction statement, if one is open.
  	 */
  	finish_xact_command();
  
  	/*
  	 * If there were no parsetrees, return EmptyQueryResponse message.
  	 */
  	if (!parsetree_list)
  		NullCommand(dest);
  
  	QueryContext = NULL;
  
  	/*
  	 * Combine processing here as we need to calculate the query duration in
  	 * both instances.
  	 */
  	if (save_log_duration || save_log_min_duration_statement != -1)
  	{
  		long		usecs;
  
  		gettimeofday(&stop_t, NULL);
  		if (stop_t.tv_usec < start_t.tv_usec)
  		{
  			stop_t.tv_sec--;
  			stop_t.tv_usec += 1000000;
  		}
  		usecs = (long) (stop_t.tv_sec - start_t.tv_sec) * 1000000 +
  			(long) (stop_t.tv_usec - start_t.tv_usec);
  
  		/* Only print duration if we previously printed the statement. */
  		if (was_logged && save_log_duration)
  			ereport(LOG,
  					(errmsg("duration: %ld.%03ld ms",
  							(long) ((stop_t.tv_sec - start_t.tv_sec) * 1000 +
  								  (stop_t.tv_usec - start_t.tv_usec) / 1000),
  						 (long) (stop_t.tv_usec - start_t.tv_usec) % 1000)));
  
  		/*
  		 * Output a duration_statement to the log if the query has exceeded
  		 * the min duration, or if we are to print all durations.
  		 */
  		if (save_log_min_duration_statement == 0 ||
  			(save_log_min_duration_statement > 0 &&
  			 usecs >= save_log_min_duration_statement * 1000))
  			ereport(LOG,
  					(errmsg("duration: %ld.%03ld ms  statement: %s%s",
  							(long) ((stop_t.tv_sec - start_t.tv_sec) * 1000 +
  								  (stop_t.tv_usec - start_t.tv_usec) / 1000),
  							(long) (stop_t.tv_usec - start_t.tv_usec) % 1000,
  							query_string,
  							prepare_string ? prepare_string : "")));
  	}
  
  	if (save_log_statement_stats)
  		ShowUsage("QUERY STATISTICS");
  
  	if (prepare_string != NULL)
  		pfree(prepare_string);
  
  	debug_query_string = NULL;
  }
  
  /*
   * exec_parse_message
   *
   * Execute a "Parse" protocol message.
   */
  static void
  exec_parse_message(const char *query_string,	/* string to execute */
  				   const char *stmt_name,		/* name for prepared stmt */
  				   Oid *paramTypes,		/* parameter types */
  				   int numParams)		/* number of parameters */
  {
  	MemoryContext oldcontext;
  	List	   *parsetree_list;
  	const char *commandTag;
  	List	   *querytree_list,
  			   *plantree_list,
  			   *param_list;
  	bool		is_named;
  	bool		save_log_statement_stats = log_statement_stats;
  
  	/*
  	 * Report query to various monitoring facilities.
  	 */
  	debug_query_string = query_string;
  
  	pgstat_report_activity(query_string);
  
  	set_ps_display("PARSE");
  
  	if (save_log_statement_stats)
  		ResetUsage();
  
  	if (log_statement == LOGSTMT_ALL)
  		ereport(LOG,
  				(errmsg("statement: PREPARE %s AS %s",
  						(*stmt_name != '\0') ? stmt_name : "<unnamed>",
  						query_string)));
  
  	/*
  	 * Start up a transaction command so we can run parse analysis etc. (Note
  	 * that this will normally change current memory context.) Nothing happens
  	 * if we are already in one.
  	 */
  	start_xact_command();
  
  	/*
  	 * Switch to appropriate context for constructing parsetrees.
  	 *
  	 * We have two strategies depending on whether the prepared statement is
  	 * named or not.  For a named prepared statement, we do parsing in
  	 * MessageContext and copy the finished trees into the prepared
  	 * statement's private context; then the reset of MessageContext releases
  	 * temporary space used by parsing and planning.  For an unnamed prepared
  	 * statement, we assume the statement isn't going to hang around long, so
  	 * getting rid of temp space quickly is probably not worth the costs of
  	 * copying parse/plan trees.  So in this case, we set up a special context
  	 * for the unnamed statement, and do all the parsing/planning therein.
  	 */
  	is_named = (stmt_name[0] != '\0');
  	if (is_named)
  	{
  		/* Named prepared statement --- parse in MessageContext */
  		oldcontext = MemoryContextSwitchTo(MessageContext);
  	}
  	else
  	{
  		/* Unnamed prepared statement --- release any prior unnamed stmt */
  		unnamed_stmt_pstmt = NULL;
  		if (unnamed_stmt_context)
  		{
  			DropDependentPortals(unnamed_stmt_context);
  			MemoryContextDelete(unnamed_stmt_context);
  		}
  		unnamed_stmt_context = NULL;
  		/* create context for parsing/planning */
  		unnamed_stmt_context =
  			AllocSetContextCreate(TopMemoryContext,
  								  "unnamed prepared statement",
  								  ALLOCSET_DEFAULT_MINSIZE,
  								  ALLOCSET_DEFAULT_INITSIZE,
  								  ALLOCSET_DEFAULT_MAXSIZE);
  		oldcontext = MemoryContextSwitchTo(unnamed_stmt_context);
  	}
  
  	QueryContext = CurrentMemoryContext;
  
  	/*
  	 * Do basic parsing of the query or queries (this should be safe even if
  	 * we are in aborted transaction state!)
  	 */
  	parsetree_list = pg_parse_query(query_string);
  
  	/*
  	 * We only allow a single user statement in a prepared statement. This is
  	 * mainly to keep the protocol simple --- otherwise we'd need to worry
  	 * about multiple result tupdescs and things like that.
  	 */
  	if (list_length(parsetree_list) > 1)
  		ereport(ERROR,
  				(errcode(ERRCODE_SYNTAX_ERROR),
  		errmsg("cannot insert multiple commands into a prepared statement")));
  
  	if (parsetree_list != NIL)
  	{
  		Node	   *parsetree = (Node *) linitial(parsetree_list);
  		int			i;
  
  		/*
  		 * Get the command name for possible use in status display.
  		 */
  		commandTag = CreateCommandTag(parsetree);
  
  		/*
  		 * If we are in an aborted transaction, reject all commands except
  		 * COMMIT/ROLLBACK.  It is important that this test occur before we
  		 * try to do parse analysis, rewrite, or planning, since all those
  		 * phases try to do database accesses, which may fail in abort state.
  		 * (It might be safe to allow some additional utility commands in this
  		 * state, but not many...)
  		 */
  		if (IsAbortedTransactionBlockState() &&
  			!IsTransactionExitStmt(parsetree))
  			ereport(ERROR,
  					(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
  					 errmsg("current transaction is aborted, "
  						"commands ignored until end of transaction block")));
  
  		/*
  		 * OK to analyze, rewrite, and plan this query.  Note that the
  		 * originally specified parameter set is not required to be complete,
  		 * so we have to use parse_analyze_varparams().
  		 */
  		if (log_parser_stats)
  			ResetUsage();
  
  		querytree_list = parse_analyze_varparams(parsetree,
  												 &paramTypes,
  												 &numParams);
  
  		/*
  		 * Check all parameter types got determined, and convert array
  		 * representation to a list for storage.
  		 */
  		param_list = NIL;
  		for (i = 0; i < numParams; i++)
  		{
  			Oid			ptype = paramTypes[i];
  
  			if (ptype == InvalidOid || ptype == UNKNOWNOID)
  				ereport(ERROR,
  						(errcode(ERRCODE_INDETERMINATE_DATATYPE),
  					 errmsg("could not determine data type of parameter $%d",
  							i + 1)));
  			param_list = lappend_oid(param_list, ptype);
  		}
  
  		if (log_parser_stats)
  			ShowUsage("PARSE ANALYSIS STATISTICS");
  
  		querytree_list = pg_rewrite_queries(querytree_list);
  
  		/*
  		 * If this is the unnamed statement and it has parameters, defer query
  		 * planning until Bind.  Otherwise do it now.
  		 */
  		if (!is_named && numParams > 0)
  			plantree_list = NIL;
  		else
  			plantree_list = pg_plan_queries(querytree_list, NULL, true);
  	}
  	else
  	{
  		/* Empty input string.	This is legal. */
  		commandTag = NULL;
  		querytree_list = NIL;
  		plantree_list = NIL;
  		param_list = NIL;
  	}
  
  	/* If we got a cancel signal in analysis or planning, quit */
  	CHECK_FOR_INTERRUPTS();
  
  	/*
  	 * Store the query as a prepared statement.  See above comments.
  	 */
  	if (is_named)
  	{
  		StorePreparedStatement(stmt_name,
  							   query_string,
  							   commandTag,
  							   querytree_list,
  							   plantree_list,
  							   param_list);
  	}
  	else
  	{
  		PreparedStatement *pstmt;
  
  		pstmt = (PreparedStatement *) palloc0(sizeof(PreparedStatement));
  		/* query_string needs to be copied into unnamed_stmt_context */
  		pstmt->query_string = pstrdup(query_string);
  		/* the rest is there already */
  		pstmt->commandTag = commandTag;
  		pstmt->query_list = querytree_list;
  		pstmt->plan_list = plantree_list;
  		pstmt->argtype_list = param_list;
  		pstmt->context = unnamed_stmt_context;
  		/* Now the unnamed statement is complete and valid */
  		unnamed_stmt_pstmt = pstmt;
  	}
  
  	MemoryContextSwitchTo(oldcontext);
  
  	QueryContext = NULL;
  
  	/*
  	 * We do NOT close the open transaction command here; that only happens
  	 * when the client sends Sync.	Instead, do CommandCounterIncrement just
  	 * in case something happened during parse/plan.
  	 */
  	CommandCounterIncrement();
  
  	/*
  	 * Send ParseComplete.
  	 */
  	if (whereToSendOutput == DestRemote)
  		pq_putemptymessage('1');
  
  	if (save_log_statement_stats)
  		ShowUsage("PARSE MESSAGE STATISTICS");
  
  	debug_query_string = NULL;
  }
  
  /*
   * exec_bind_message
   *
   * Process a "Bind" message to create a portal from a prepared statement
   */
  static void
  exec_bind_message(StringInfo input_message)
  {
  	const char *portal_name;
  	const char *stmt_name;
  	int			numPFormats;
  	int16	   *pformats = NULL;
  	int			numParams;
  	int			numRFormats;
  	int16	   *rformats = NULL;
  	int			i;
  	PreparedStatement *pstmt;
  	Portal		portal;
  	ParamListInfo params;
  
  	pgstat_report_activity("<BIND>");
  
  	set_ps_display("BIND");
  
  	/*
  	 * Start up a transaction command so we can call functions etc. (Note that
  	 * this will normally change current memory context.) Nothing happens if
  	 * we are already in one.
  	 */
  	start_xact_command();
  
  	/* Switch back to message context */
  	MemoryContextSwitchTo(MessageContext);
  
  	/* Get the fixed part of the message */
  	portal_name = pq_getmsgstring(input_message);
  	stmt_name = pq_getmsgstring(input_message);
  
  	/* Get the parameter format codes */
  	numPFormats = pq_getmsgint(input_message, 2);
  	if (numPFormats > 0)
  	{
  		pformats = (int16 *) palloc(numPFormats * sizeof(int16));
  		for (i = 0; i < numPFormats; i++)
  			pformats[i] = pq_getmsgint(input_message, 2);
  	}
  
  	/* Get the parameter value count */
  	numParams = pq_getmsgint(input_message, 2);
  
  	if (numPFormats > 1 && numPFormats != numParams)
  		ereport(ERROR,
  				(errcode(ERRCODE_PROTOCOL_VIOLATION),
  			errmsg("bind message has %d parameter formats but %d parameters",
  				   numPFormats, numParams)));
  
  	/* Find prepared statement */
  	if (stmt_name[0] != '\0')
  		pstmt = FetchPreparedStatement(stmt_name, true);
  	else
  	{
  		/* special-case the unnamed statement */
  		pstmt = unnamed_stmt_pstmt;
  		if (!pstmt)
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_PSTATEMENT),
  					 errmsg("unnamed prepared statement does not exist")));
  	}
  
  	if (numParams != list_length(pstmt->argtype_list))
  		ereport(ERROR,
  				(errcode(ERRCODE_PROTOCOL_VIOLATION),
  				 errmsg("bind message supplies %d parameters, but prepared statement \"%s\" requires %d",
  				   numParams, stmt_name, list_length(pstmt->argtype_list))));
  
  	/*
  	 * If we are in aborted transaction state, the only portals we can
  	 * actually run are those containing COMMIT or ROLLBACK commands. We
  	 * disallow binding anything else to avoid problems with infrastructure
  	 * that expects to run inside a valid transaction.	We also disallow
  	 * binding any parameters, since we can't risk calling user-defined I/O
  	 * functions.
  	 */
  	if (IsAbortedTransactionBlockState() &&
  		(!IsTransactionExitStmtList(pstmt->query_list) ||
  		 numParams != 0))
  		ereport(ERROR,
  				(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
  				 errmsg("current transaction is aborted, "
  						"commands ignored until end of transaction block")));
  
  	/*
  	 * Create the portal.  Allow silent replacement of an existing portal only
  	 * if the unnamed portal is specified.
  	 */
  	if (portal_name[0] == '\0')
  		portal = CreatePortal(portal_name, true, true);
  	else
  		portal = CreatePortal(portal_name, false, false);
  
  	/* We need to output the parameter values someday */
  	if (log_statement == LOGSTMT_ALL)
  		ereport(LOG,
  				(errmsg("statement: <BIND> %s", portal_name)));
  
  	/*
  	 * Fetch parameters, if any, and store in the portal's memory context.
  	 */
  	if (numParams > 0)
  	{
  		ListCell   *l;
  		MemoryContext oldContext;
  
  		oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
  
  		params = (ParamListInfo)
  			palloc0((numParams + 1) * sizeof(ParamListInfoData));
  
  		i = 0;
  		foreach(l, pstmt->argtype_list)
  		{
  			Oid			ptype = lfirst_oid(l);
  			int32		plength;
  			bool		isNull;
  
  			plength = pq_getmsgint(input_message, 4);
  			isNull = (plength == -1);
  
  			if (!isNull)
  			{
  				const char *pvalue = pq_getmsgbytes(input_message, plength);
  				int16		pformat;
  				StringInfoData pbuf;
  				char		csave;
  
  				if (numPFormats > 1)
  					pformat = pformats[i];
  				else if (numPFormats > 0)
  					pformat = pformats[0];
  				else
  					pformat = 0;	/* default = text */
  
  				/*
  				 * Rather than copying data around, we just set up a phony
  				 * StringInfo pointing to the correct portion of the message
  				 * buffer.	We assume we can scribble on the message buffer so
  				 * as to maintain the convention that StringInfos have a
  				 * trailing null.  This is grotty but is a big win when
  				 * dealing with very large parameter strings.
  				 */
  				pbuf.data = (char *) pvalue;
  				pbuf.maxlen = plength + 1;
  				pbuf.len = plength;
  				pbuf.cursor = 0;
  
  				csave = pbuf.data[plength];
  				pbuf.data[plength] = '\0';
  
  				if (pformat == 0)
  				{
  					Oid			typinput;
  					Oid			typioparam;
  					char	   *pstring;
  
  					getTypeInputInfo(ptype, &typinput, &typioparam);
  
  					/*
  					 * We have to do encoding conversion before calling the
  					 * typinput routine.
  					 */
  					pstring = pg_client_to_server(pbuf.data, plength);
  					params[i].value =
  						OidFunctionCall3(typinput,
  										 CStringGetDatum(pstring),
  										 ObjectIdGetDatum(typioparam),
  										 Int32GetDatum(-1));
  					/* Free result of encoding conversion, if any */
  					if (pstring != pbuf.data)
  						pfree(pstring);
  				}
  				else if (pformat == 1)
  				{
  					Oid			typreceive;
  					Oid			typioparam;
  
  					/*
  					 * Call the parameter type's binary input converter
  					 */
  					getTypeBinaryInputInfo(ptype, &typreceive, &typioparam);
  
  					params[i].value =
  						OidFunctionCall3(typreceive,
  										 PointerGetDatum(&pbuf),
  										 ObjectIdGetDatum(typioparam),
  										 Int32GetDatum(-1));
  
  					/* Trouble if it didn't eat the whole buffer */
  					if (pbuf.cursor != pbuf.len)
  						ereport(ERROR,
  							 (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
  							  errmsg("incorrect binary data format in bind parameter %d",
  									 i + 1)));
  				}
  				else
  				{
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("unsupported format code: %d",
  									pformat)));
  				}
  
  				/* Restore message buffer contents */
  				pbuf.data[plength] = csave;
  			}
  
  			params[i].kind = PARAM_NUM;
  			params[i].id = i + 1;
  			params[i].ptype = ptype;
  			params[i].isnull = isNull;
  
  			i++;
  		}
  
  		params[i].kind = PARAM_INVALID;
  
  		MemoryContextSwitchTo(oldContext);
  	}
  	else
  		params = NULL;
  
  	/* Get the result format codes */
  	numRFormats = pq_getmsgint(input_message, 2);
  	if (numRFormats > 0)
  	{
  		rformats = (int16 *) palloc(numRFormats * sizeof(int16));
  		for (i = 0; i < numRFormats; i++)
  			rformats[i] = pq_getmsgint(input_message, 2);
  	}
  
  	pq_getmsgend(input_message);
  
  	/*
  	 * If we didn't plan the query before, do it now.  This allows the planner
  	 * to make use of the concrete parameter values we now have.
  	 *
  	 * This happens only for unnamed statements, and so switching into the
  	 * statement context for planning is correct (see notes in
  	 * exec_parse_message).
  	 */
  	if (pstmt->plan_list == NIL && pstmt->query_list != NIL)
  	{
  		MemoryContext oldContext = MemoryContextSwitchTo(pstmt->context);
  
  		pstmt->plan_list = pg_plan_queries(pstmt->query_list, params, true);
  		MemoryContextSwitchTo(oldContext);
  	}
  
  	/*
  	 * Define portal and start execution.
  	 */
  	PortalDefineQuery(portal,
  					  pstmt->query_string,
  					  pstmt->commandTag,
  					  pstmt->query_list,
  					  pstmt->plan_list,
  					  pstmt->context);
  
  	PortalStart(portal, params, InvalidSnapshot);
  
  	/*
  	 * Apply the result format requests to the portal.
  	 */
  	PortalSetResultFormat(portal, numRFormats, rformats);
  
  	/*
  	 * Send BindComplete.
  	 */
  	if (whereToSendOutput == DestRemote)
  		pq_putemptymessage('2');
  }
  
  /*
   * exec_execute_message
   *
   * Process an "Execute" message for a portal
   */
  static void
  exec_execute_message(const char *portal_name, long max_rows)
  {
  	CommandDest dest;
  	DestReceiver *receiver;
  	Portal		portal;
  	bool		completed;
  	char		completionTag[COMPLETION_TAG_BUFSIZE];
  	struct timeval start_t,
  				stop_t;
  	bool		save_log_duration = log_duration;
  	int			save_log_min_duration_statement = log_min_duration_statement;
  	bool		save_log_statement_stats = log_statement_stats;
  	bool		execute_is_fetch = false;
  
  	/* Adjust destination to tell printtup.c what to do */
  	dest = whereToSendOutput;
  	if (dest == DestRemote)
  		dest = DestRemoteExecute;
  
  	portal = GetPortalByName(portal_name);
  	if (!PortalIsValid(portal))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_CURSOR),
  				 errmsg("portal \"%s\" does not exist", portal_name)));
  
  	/*
  	 * If we re-issue an Execute protocol request against an existing portal,
  	 * then we are only fetching more rows rather than completely re-executing
  	 * the query from the start. atStart is never reset for a v3 portal, so we
  	 * are safe to use this check.
  	 */
  	if (!portal->atStart)
  		execute_is_fetch = true;
  
  	/*
  	 * If the original query was a null string, just return
  	 * EmptyQueryResponse.
  	 */
  	if (portal->commandTag == NULL)
  	{
  		Assert(portal->parseTrees == NIL);
  		NullCommand(dest);
  		return;
  	}
  
  	/* Should we display the portal names here? */
  	if (execute_is_fetch)
  	{
  		debug_query_string = "fetch message";
  		pgstat_report_activity("<FETCH>");
  	}
  	else if (portal->sourceText)
  	{
  		debug_query_string = portal->sourceText;
  		pgstat_report_activity(portal->sourceText);
  	}
  	else
  	{
  		debug_query_string = "execute message";
  		pgstat_report_activity("<EXECUTE>");
  	}
  
  	set_ps_display(portal->commandTag);
  
  	/*
  	 * We use save_log_* so "SET log_duration = true"  and "SET
  	 * log_min_duration_statement = true" don't report incorrect time because
  	 * gettimeofday() wasn't called. Similarly, log_statement_stats has to be
  	 * captured once.
  	 */
  	if (save_log_duration || save_log_min_duration_statement != -1)
  		gettimeofday(&start_t, NULL);
  
  	if (save_log_statement_stats)
  		ResetUsage();
  
  	if (log_statement == LOGSTMT_ALL)
  		/* We have the portal, so output the source query. */
  		ereport(LOG,
  				(errmsg("statement: %sEXECUTE %s  [PREPARE:  %s]",
  						(execute_is_fetch) ? "FETCH from " : "",
  						(*portal_name != '\0') ? portal_name : "<unnamed>",
  						portal->sourceText ? portal->sourceText : "")));
  
  	BeginCommand(portal->commandTag, dest);
  
  	/*
  	 * Create dest receiver in MessageContext (we don't want it in transaction
  	 * context, because that may get deleted if portal contains VACUUM).
  	 */
  	receiver = CreateDestReceiver(dest, portal);
  
  	/*
  	 * Ensure we are in a transaction command (this should normally be the
  	 * case already due to prior BIND).
  	 */
  	start_xact_command();
  
  	/*
  	 * If we are in aborted transaction state, the only portals we can
  	 * actually run are those containing COMMIT or ROLLBACK commands.
  	 */
  	if (IsAbortedTransactionBlockState() &&
  		!IsTransactionExitStmtList(portal->parseTrees))
  		ereport(ERROR,
  				(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
  				 errmsg("current transaction is aborted, "
  						"commands ignored until end of transaction block")));
  
  	/* Check for cancel signal before we start execution */
  	CHECK_FOR_INTERRUPTS();
  
  	/*
  	 * Okay to run the portal.
  	 */
  	if (max_rows <= 0)
  		max_rows = FETCH_ALL;
  
  	completed = PortalRun(portal,
  						  max_rows,
  						  receiver,
  						  receiver,
  						  completionTag);
  
  	(*receiver->rDestroy) (receiver);
  
  	if (completed)
  	{
  		if (IsTransactionStmtList(portal->parseTrees))
  		{
  			/*
  			 * If this was a transaction control statement, commit it.	We
  			 * will start a new xact command for the next command (if any).
  			 */
  			finish_xact_command();
  		}
  		else
  		{
  			/*
  			 * We need a CommandCounterIncrement after every query, except
  			 * those that start or end a transaction block.
  			 */
  			CommandCounterIncrement();
  		}
  
  		/* Send appropriate CommandComplete to client */
  		EndCommand(completionTag, dest);
  	}
  	else
  	{
  		/* Portal run not complete, so send PortalSuspended */
  		if (whereToSendOutput == DestRemote)
  			pq_putemptymessage('s');
  	}
  
  	/*
  	 * Combine processing here as we need to calculate the query duration in
  	 * both instances.
  	 */
  	if (save_log_duration || save_log_min_duration_statement != -1)
  	{
  		long		usecs;
  
  		gettimeofday(&stop_t, NULL);
  		if (stop_t.tv_usec < start_t.tv_usec)
  		{
  			stop_t.tv_sec--;
  			stop_t.tv_usec += 1000000;
  		}
  		usecs = (long) (stop_t.tv_sec - start_t.tv_sec) * 1000000 +
  			(long) (stop_t.tv_usec - start_t.tv_usec);
  
  		/* Only print duration if we previously printed the statement. */
  		if (log_statement == LOGSTMT_ALL && save_log_duration)
  			ereport(LOG,
  					(errmsg("duration: %ld.%03ld ms",
  							(long) ((stop_t.tv_sec - start_t.tv_sec) * 1000 +
  								  (stop_t.tv_usec - start_t.tv_usec) / 1000),
  						 (long) (stop_t.tv_usec - start_t.tv_usec) % 1000)));
  
  		/*
  		 * Output a duration_statement to the log if the query has exceeded
  		 * the min duration, or if we are to print all durations.
  		 */
  		if (save_log_min_duration_statement == 0 ||
  			(save_log_min_duration_statement > 0 &&
  			 usecs >= save_log_min_duration_statement * 1000))
  			ereport(LOG,
  					(errmsg("duration: %ld.%03ld ms  statement: %sEXECUTE %s  [PREPARE:  %s]",
  							(long) ((stop_t.tv_sec - start_t.tv_sec) * 1000 +
  								  (stop_t.tv_usec - start_t.tv_usec) / 1000),
  							(long) (stop_t.tv_usec - start_t.tv_usec) % 1000,
  							(execute_is_fetch) ? "FETCH from " : "",
  						  (*portal_name != '\0') ? portal_name : "<unnamed>",
  							portal->sourceText ? portal->sourceText : "")));
  	}
  
  	if (save_log_statement_stats)
  		ShowUsage("QUERY STATISTICS");
  
  	debug_query_string = NULL;
  }
  
  /*
   * exec_describe_statement_message
   *
   * Process a "Describe" message for a prepared statement
   */
  static void
  exec_describe_statement_message(const char *stmt_name)
  {
  	PreparedStatement *pstmt;
  	TupleDesc	tupdesc;
  	ListCell   *l;
  	StringInfoData buf;
  
  	/*
  	 * Start up a transaction command. (Note that this will normally change
  	 * current memory context.) Nothing happens if we are already in one.
  	 */
  	start_xact_command();
  
  	/* Switch back to message context */
  	MemoryContextSwitchTo(MessageContext);
  
  	/* Find prepared statement */
  	if (stmt_name[0] != '\0')
  		pstmt = FetchPreparedStatement(stmt_name, true);
  	else
  	{
  		/* special-case the unnamed statement */
  		pstmt = unnamed_stmt_pstmt;
  		if (!pstmt)
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_PSTATEMENT),
  					 errmsg("unnamed prepared statement does not exist")));
  	}
  
  	/*
  	 * If we are in aborted transaction state, we can't safely create a result
  	 * tupledesc, because that needs catalog accesses.  Hence, refuse to
  	 * Describe statements that return data.  (We shouldn't just refuse all
  	 * Describes, since that might break the ability of some clients to issue
  	 * COMMIT or ROLLBACK commands, if they use code that blindly Describes
  	 * whatever it does.)  We can Describe parameters without doing anything
  	 * dangerous, so we don't restrict that.
  	 */
  	if (IsAbortedTransactionBlockState() &&
  		PreparedStatementReturnsTuples(pstmt))
  		ereport(ERROR,
  				(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
  				 errmsg("current transaction is aborted, "
  						"commands ignored until end of transaction block")));
  
  	if (whereToSendOutput != DestRemote)
  		return;					/* can't actually do anything... */
  
  	/*
  	 * First describe the parameters...
  	 */
  	pq_beginmessage(&buf, 't'); /* parameter description message type */
  	pq_sendint(&buf, list_length(pstmt->argtype_list), 2);
  
  	foreach(l, pstmt->argtype_list)
  	{
  		Oid			ptype = lfirst_oid(l);
  
  		pq_sendint(&buf, (int) ptype, 4);
  	}
  	pq_endmessage(&buf);
  
  	/*
  	 * Next send RowDescription or NoData to describe the result...
  	 */
  	tupdesc = FetchPreparedStatementResultDesc(pstmt);
  	if (tupdesc)
  		SendRowDescriptionMessage(tupdesc,
  								  FetchPreparedStatementTargetList(pstmt),
  								  NULL);
  	else
  		pq_putemptymessage('n');	/* NoData */
  
  }
  
  /*
   * exec_describe_portal_message
   *
   * Process a "Describe" message for a portal
   */
  static void
  exec_describe_portal_message(const char *portal_name)
  {
  	Portal		portal;
  
  	/*
  	 * Start up a transaction command. (Note that this will normally change
  	 * current memory context.) Nothing happens if we are already in one.
  	 */
  	start_xact_command();
  
  	/* Switch back to message context */
  	MemoryContextSwitchTo(MessageContext);
  
  	portal = GetPortalByName(portal_name);
  	if (!PortalIsValid(portal))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_CURSOR),
  				 errmsg("portal \"%s\" does not exist", portal_name)));
  
  	/*
  	 * If we are in aborted transaction state, we can't run
  	 * SendRowDescriptionMessage(), because that needs catalog accesses.
  	 * Hence, refuse to Describe portals that return data.  (We shouldn't just
  	 * refuse all Describes, since that might break the ability of some
  	 * clients to issue COMMIT or ROLLBACK commands, if they use code that
  	 * blindly Describes whatever it does.)
  	 */
  	if (IsAbortedTransactionBlockState() &&
  		portal->tupDesc)
  		ereport(ERROR,
  				(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
  				 errmsg("current transaction is aborted, "
  						"commands ignored until end of transaction block")));
  
  	if (whereToSendOutput != DestRemote)
  		return;					/* can't actually do anything... */
  
  	if (portal->tupDesc)
  		SendRowDescriptionMessage(portal->tupDesc,
  								  FetchPortalTargetList(portal),
  								  portal->formats);
  	else
  		pq_putemptymessage('n');	/* NoData */
  }
  
  
  /*
   * Convenience routines for starting/committing a single command.
   */
  static void
  start_xact_command(void)
  {
  	if (!xact_started)
  	{
  		ereport(DEBUG3,
  				(errmsg_internal("StartTransactionCommand")));
  		StartTransactionCommand();
  
  		/* Set statement timeout running, if any */
  		if (StatementTimeout > 0)
  			enable_sig_alarm(StatementTimeout, true);
  		else
  			cancel_from_timeout = false;
  
  		xact_started = true;
  	}
  }
  
  static void
  finish_xact_command(void)
  {
  	if (xact_started)
  	{
  		/* Cancel any active statement timeout before committing */
  		disable_sig_alarm(true);
  
  		/* Now commit the command */
  		ereport(DEBUG3,
  				(errmsg_internal("CommitTransactionCommand")));
  
  		CommitTransactionCommand();
  
  #ifdef MEMORY_CONTEXT_CHECKING
  		/* Check all memory contexts that weren't freed during commit */
  		/* (those that were, were checked before being deleted) */
  		MemoryContextCheck(TopMemoryContext);
  #endif
  
  #ifdef SHOW_MEMORY_STATS
  		/* Print mem stats after each commit for leak tracking */
  		if (ShowStats)
  			MemoryContextStats(TopMemoryContext);
  #endif
  
  		xact_started = false;
  	}
  }
  
  
  /*
   * Convenience routines for checking whether a statement is one of the
   * ones that we allow in transaction-aborted state.
   */
  
  static bool
  IsTransactionExitStmt(Node *parsetree)
  {
  	if (parsetree && IsA(parsetree, TransactionStmt))
  	{
  		TransactionStmt *stmt = (TransactionStmt *) parsetree;
  
  		if (stmt->kind == TRANS_STMT_COMMIT ||
  			stmt->kind == TRANS_STMT_PREPARE ||
  			stmt->kind == TRANS_STMT_ROLLBACK ||
  			stmt->kind == TRANS_STMT_ROLLBACK_TO)
  			return true;
  	}
  	return false;
  }
  
  static bool
  IsTransactionExitStmtList(List *parseTrees)
  {
  	if (list_length(parseTrees) == 1)
  	{
  		Query	   *query = (Query *) linitial(parseTrees);
  
  		if (query->commandType == CMD_UTILITY &&
  			IsTransactionExitStmt(query->utilityStmt))
  			return true;
  	}
  	return false;
  }
  
  static bool
  IsTransactionStmtList(List *parseTrees)
  {
  	if (list_length(parseTrees) == 1)
  	{
  		Query	   *query = (Query *) linitial(parseTrees);
  
  		if (query->commandType == CMD_UTILITY &&
  			query->utilityStmt && IsA(query->utilityStmt, TransactionStmt))
  			return true;
  	}
  	return false;
  }
  
  
  /* --------------------------------
   *		signal handler routines used in PostgresMain()
   * --------------------------------
   */
  
  /*
   * quickdie() occurs when signalled SIGQUIT by the postmaster.
   *
   * Some backend has bought the farm,
   * so we need to stop what we're doing and exit.
   */
  void
  quickdie(SIGNAL_ARGS)
  {
  	PG_SETMASK(&BlockSig);
  
  	/*
  	 * Ideally this should be ereport(FATAL), but then we'd not get control
  	 * back...
  	 */
  	ereport(WARNING,
  			(errcode(ERRCODE_CRASH_SHUTDOWN),
  			 errmsg("terminating connection because of crash of another server process"),
  	errdetail("The postmaster has commanded this server process to roll back"
  			  " the current transaction and exit, because another"
  			  " server process exited abnormally and possibly corrupted"
  			  " shared memory."),
  			 errhint("In a moment you should be able to reconnect to the"
  					 " database and repeat your command.")));
  
  	/*
  	 * DO NOT proc_exit() -- we're here because shared memory may be
  	 * corrupted, so we don't want to try to clean up our transaction. Just
  	 * nail the windows shut and get out of town.
  	 *
  	 * Note we do exit(1) not exit(0).	This is to force the postmaster into a
  	 * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
  	 * backend.  This is necessary precisely because we don't clean up our
  	 * shared memory state.
  	 */
  	exit(1);
  }
  
  /*
   * Shutdown signal from postmaster: abort transaction and exit
   * at soonest convenient time
   */
  void
  die(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	/* Don't joggle the elbow of proc_exit */
  	if (!proc_exit_inprogress)
  	{
  		InterruptPending = true;
  		ProcDiePending = true;
  
  		/*
  		 * If it's safe to interrupt, and we're waiting for input or a lock,
  		 * service the interrupt immediately
  		 */
  		if (ImmediateInterruptOK && InterruptHoldoffCount == 0 &&
  			CritSectionCount == 0)
  		{
  			/* bump holdoff count to make ProcessInterrupts() a no-op */
  			/* until we are done getting ready for it */
  			InterruptHoldoffCount++;
  			DisableNotifyInterrupt();
  			DisableCatchupInterrupt();
  			/* Make sure CheckDeadLock won't run while shutting down... */
  			LockWaitCancel();
  			InterruptHoldoffCount--;
  			ProcessInterrupts();
  		}
  	}
  
  	errno = save_errno;
  }
  
  /*
   * Timeout or shutdown signal from postmaster during client authentication.
   * Simply exit(0).
   *
   * XXX: possible future improvement: try to send a message indicating
   * why we are disconnecting.  Problem is to be sure we don't block while
   * doing so, nor mess up the authentication message exchange.
   */
  void
  authdie(SIGNAL_ARGS)
  {
  	exit(0);
  }
  
  /*
   * Query-cancel signal from postmaster: abort current transaction
   * at soonest convenient time
   */
  void
  StatementCancelHandler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	/*
  	 * Don't joggle the elbow of proc_exit
  	 */
  	if (!proc_exit_inprogress)
  	{
  		InterruptPending = true;
  		QueryCancelPending = true;
  
  		/*
  		 * If it's safe to interrupt, and we're waiting for a lock, service
  		 * the interrupt immediately.  No point in interrupting if we're
  		 * waiting for input, however.
  		 */
  		if (ImmediateInterruptOK && InterruptHoldoffCount == 0 &&
  			CritSectionCount == 0)
  		{
  			/* bump holdoff count to make ProcessInterrupts() a no-op */
  			/* until we are done getting ready for it */
  			InterruptHoldoffCount++;
  			if (LockWaitCancel())
  			{
  				DisableNotifyInterrupt();
  				DisableCatchupInterrupt();
  				InterruptHoldoffCount--;
  				ProcessInterrupts();
  			}
  			else
  				InterruptHoldoffCount--;
  		}
  	}
  
  	errno = save_errno;
  }
  
  /* signal handler for floating point exception */
  void
  FloatExceptionHandler(SIGNAL_ARGS)
  {
  	ereport(ERROR,
  			(errcode(ERRCODE_FLOATING_POINT_EXCEPTION),
  			 errmsg("floating-point exception"),
  			 errdetail("An invalid floating-point operation was signaled. "
  					   "This probably means an out-of-range result or an "
  					   "invalid operation, such as division by zero.")));
  }
  
  /* SIGHUP: set flag to re-read config file at next convenient time */
  static void
  SigHupHandler(SIGNAL_ARGS)
  {
  	got_SIGHUP = true;
  }
  
  
  /*
   * ProcessInterrupts: out-of-line portion of CHECK_FOR_INTERRUPTS() macro
   *
   * If an interrupt condition is pending, and it's safe to service it,
   * then clear the flag and accept the interrupt.  Called only when
   * InterruptPending is true.
   */
  void
  ProcessInterrupts(void)
  {
  	/* OK to accept interrupt now? */
  	if (InterruptHoldoffCount != 0 || CritSectionCount != 0)
  		return;
  	InterruptPending = false;
  	if (ProcDiePending)
  	{
  		ProcDiePending = false;
  		QueryCancelPending = false;		/* ProcDie trumps QueryCancel */
  		ImmediateInterruptOK = false;	/* not idle anymore */
  		DisableNotifyInterrupt();
  		DisableCatchupInterrupt();
  		ereport(FATAL,
  				(errcode(ERRCODE_ADMIN_SHUTDOWN),
  			 errmsg("terminating connection due to administrator command")));
  	}
  	if (QueryCancelPending)
  	{
  		QueryCancelPending = false;
  		ImmediateInterruptOK = false;	/* not idle anymore */
  		DisableNotifyInterrupt();
  		DisableCatchupInterrupt();
  		if (cancel_from_timeout)
  			ereport(ERROR,
  					(errcode(ERRCODE_QUERY_CANCELED),
  					 errmsg("canceling statement due to statement timeout")));
  		else
  			ereport(ERROR,
  					(errcode(ERRCODE_QUERY_CANCELED),
  					 errmsg("canceling statement due to user request")));
  	}
  	/* If we get here, do nothing (probably, QueryCancelPending was reset) */
  }
  
  
  /*
   * check_stack_depth: check for excessively deep recursion
   *
   * This should be called someplace in any recursive routine that might possibly
   * recurse deep enough to overflow the stack.  Most Unixen treat stack
   * overflow as an unrecoverable SIGSEGV, so we want to error out ourselves
   * before hitting the hardware limit.  Unfortunately we have no direct way
   * to detect the hardware limit, so we have to rely on the admin to set a
   * GUC variable for it ...
   */
  void
  check_stack_depth(void)
  {
  	char		stack_top_loc;
  	int			stack_depth;
  
  	/*
  	 * Compute distance from PostgresMain's local variables to my own
  	 *
  	 * Note: in theory stack_depth should be ptrdiff_t or some such, but since
  	 * the whole point of this code is to bound the value to something much
  	 * less than integer-sized, int should work fine.
  	 */
  	stack_depth = (int) (stack_base_ptr - &stack_top_loc);
  
  	/*
  	 * Take abs value, since stacks grow up on some machines, down on others
  	 */
  	if (stack_depth < 0)
  		stack_depth = -stack_depth;
  
  	/*
  	 * Trouble?
  	 *
  	 * The test on stack_base_ptr prevents us from erroring out if called
  	 * during process setup or in a non-backend process.  Logically it should
  	 * be done first, but putting it here avoids wasting cycles during normal
  	 * cases.
  	 */
  	if (stack_depth > max_stack_depth_bytes &&
  		stack_base_ptr != NULL)
  	{
  		ereport(ERROR,
  				(errcode(ERRCODE_STATEMENT_TOO_COMPLEX),
  				 errmsg("stack depth limit exceeded"),
  				 errhint("Increase the configuration parameter \"max_stack_depth\".")));
  	}
  }
  
  /* GUC assign hook to update max_stack_depth_bytes from max_stack_depth */
  bool
  assign_max_stack_depth(int newval, bool doit, GucSource source)
  {
  	/* Range check was already handled by guc.c */
  	if (doit)
  		max_stack_depth_bytes = newval * 1024;
  	return true;
  }
  
  
  static void
  usage(const char *progname)
  {
  	printf(_("%s is the PostgreSQL stand-alone backend.  It is not\nintended to be used by normal users.\n\n"), progname);
  
  	printf(_("Usage:\n  %s [OPTION]... [DBNAME]\n\n"), progname);
  	printf(_("Options:\n"));
  #ifdef USE_ASSERT_CHECKING
  	printf(_("  -A 1|0          enable/disable run-time assert checking\n"));
  #endif
  	printf(_("  -B NBUFFERS     number of shared buffers\n"));
  	printf(_("  -c NAME=VALUE   set run-time parameter\n"));
  	printf(_("  -d 0-5          debugging level (0 is off)\n"));
  	printf(_("  -D DATADIR      database directory\n"));
  	printf(_("  -e              use European date input format (DMY)\n"));
  	printf(_("  -E              echo query before execution\n"));
  	printf(_("  -F              turn fsync off\n"));
  	printf(_("  -N              do not use newline as interactive query delimiter\n"));
  	printf(_("  -o FILENAME     send stdout and stderr to given file\n"));
  	printf(_("  -P              disable system indexes\n"));
  	printf(_("  -s              show statistics after each query\n"));
  	printf(_("  -S WORK-MEM     set amount of memory for sorts (in kB)\n"));
  	printf(_("  --describe-config  describe configuration parameters, then exit\n"));
  	printf(_("  --help          show this help, then exit\n"));
  	printf(_("  --version       output version information, then exit\n"));
  	printf(_("\nDeveloper options:\n"));
  	printf(_("  -f s|i|n|m|h    forbid use of some plan types\n"));
  	printf(_("  -i              do not execute queries\n"));
  	printf(_("  -O              allow system table structure changes\n"));
  	printf(_("  -t pa|pl|ex     show timings after each query\n"));
  	printf(_("  -W NUM          wait NUM seconds to allow attach from a debugger\n"));
  	printf(_("\nReport bugs to <pgsql-bugs@postgresql.org>.\n"));
  }
  
  
  /*
   * set_debug_options --- apply "-d N" command line option
   *
   * -d is not quite the same as setting log_min_messages because it enables
   * other output options.
   */
  void
  set_debug_options(int debug_flag, GucContext context, GucSource source)
  {
  	if (debug_flag > 0)
  	{
  		char		debugstr[64];
  
  		sprintf(debugstr, "debug%d", debug_flag);
  		SetConfigOption("log_min_messages", debugstr, context, source);
  	}
  	else
  		SetConfigOption("log_min_messages", "notice", context, source);
  
  	if (debug_flag >= 1 && context == PGC_POSTMASTER)
  	{
  		SetConfigOption("log_connections", "true", context, source);
  		SetConfigOption("log_disconnections", "true", context, source);
  	}
  	if (debug_flag >= 2)
  		SetConfigOption("log_statement", "all", context, source);
  	if (debug_flag >= 3)
  		SetConfigOption("debug_print_parse", "true", context, source);
  	if (debug_flag >= 4)
  		SetConfigOption("debug_print_plan", "true", context, source);
  	if (debug_flag >= 5)
  		SetConfigOption("debug_print_rewritten", "true", context, source);
  }
  
  
  /* ----------------------------------------------------------------
   * PostgresMain
   *	   postgres main loop -- all backends, interactive or otherwise start here
   *
   * argc/argv are the command line arguments to be used.  (When being forked
   * by the postmaster, these are not the original argv array of the process.)
   * username is the (possibly authenticated) PostgreSQL user name to be used
   * for the session.
   * ----------------------------------------------------------------
   */
  int
  PostgresMain(int argc, char *argv[], const char *username)
  {
  	int			flag;
  	const char *dbname = NULL;
  	char	   *userDoption = NULL;
  	bool		secure;
  	int			errs = 0;
  	int			debug_flag = -1;	/* -1 means not given */
  	List	   *guc_names = NIL;	/* for SUSET options */
  	List	   *guc_values = NIL;
  	GucContext	ctx;
  	GucSource	gucsource;
  	bool		am_superuser;
  	char	   *tmp;
  	int			firstchar;
  	char		stack_base;
  	StringInfoData input_message;
  	sigjmp_buf	local_sigjmp_buf;
  	volatile bool send_rfq = true;
  
  #define PendingConfigOption(name,val) \
  	(guc_names = lappend(guc_names, pstrdup(name)), \
  	 guc_values = lappend(guc_values, pstrdup(val)))
  
  	/*
  	 * Catch standard options before doing much else.  This even works on
  	 * systems without getopt_long.
  	 */
  	if (!IsUnderPostmaster && argc > 1)
  	{
  		if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-?") == 0)
  		{
  			usage(argv[0]);
  			exit(0);
  		}
  		if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
  		{
  			puts(PG_VERSIONSTR);
  			exit(0);
  		}
  	}
  
  	/*
  	 * initialize globals (already done if under postmaster, but not if
  	 * standalone; cheap enough to do over)
  	 */
  	MyProcPid = getpid();
  
  	/*
  	 * Fire up essential subsystems: error and memory management
  	 *
  	 * If we are running under the postmaster, this is done already.
  	 */
  	if (!IsUnderPostmaster)
  		MemoryContextInit();
  
  	set_ps_display("startup");
  
  	SetProcessingMode(InitProcessing);
  
  	/* Set up reference point for stack depth checking */
  	stack_base_ptr = &stack_base;
  
  	/* Compute paths, if we didn't inherit them from postmaster */
  	if (my_exec_path[0] == '\0')
  	{
  		if (find_my_exec(argv[0], my_exec_path) < 0)
  			elog(FATAL, "%s: could not locate my own executable path",
  				 argv[0]);
  	}
  
  	if (pkglib_path[0] == '\0')
  		get_pkglib_path(my_exec_path, pkglib_path);
  
  	/*
  	 * Set default values for command-line options.
  	 */
  	EchoQuery = false;
  
  	if (!IsUnderPostmaster)
  		InitializeGUCOptions();
  
  	/* ----------------
  	 *	parse command line arguments
  	 *
  	 *	There are now two styles of command line layout for the backend:
  	 *
  	 *	For interactive use (not started from postmaster) the format is
  	 *		postgres [switches] [databasename]
  	 *	If the databasename is omitted it is taken to be the user name.
  	 *
  	 *	When started from the postmaster, the format is
  	 *		postgres [secure switches] -p databasename [insecure switches]
  	 *	Switches appearing after -p came from the client (via "options"
  	 *	field of connection request).  For security reasons we restrict
  	 *	what these switches can do.
  	 * ----------------
  	 */
  
  	/* all options are allowed until '-p' */
  	secure = true;
  	ctx = PGC_POSTMASTER;
  	gucsource = PGC_S_ARGV;		/* initial switches came from command line */
  
  	while ((flag = getopt(argc, argv, "A:B:c:D:d:Eef:FiNOPo:p:S:st:v:W:-:")) != -1)
  	{
  		switch (flag)
  		{
  			case 'A':
  #ifdef USE_ASSERT_CHECKING
  				SetConfigOption("debug_assertions", optarg, ctx, gucsource);
  #else
  				ereport(WARNING,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("assert checking is not compiled in")));
  #endif
  				break;
  
  			case 'B':
  
  				/*
  				 * specify the size of buffer pool
  				 */
  				SetConfigOption("shared_buffers", optarg, ctx, gucsource);
  				break;
  
  			case 'D':			/* PGDATA or config directory */
  				if (secure)
  					userDoption = optarg;
  				break;
  
  			case 'd':			/* debug level */
  				debug_flag = atoi(optarg);
  				break;
  
  			case 'E':
  
  				/*
  				 * E - echo the query the user entered
  				 */
  				EchoQuery = true;
  				break;
  
  			case 'e':
  
  				/*
  				 * Use European date input format (DMY)
  				 */
  				SetConfigOption("datestyle", "euro", ctx, gucsource);
  				break;
  
  			case 'F':
  
  				/*
  				 * turn off fsync
  				 */
  				SetConfigOption("fsync", "false", ctx, gucsource);
  				break;
  
  			case 'f':
  
  				/*
  				 * f - forbid generation of certain plans
  				 */
  				tmp = NULL;
  				switch (optarg[0])
  				{
  					case 's':	/* seqscan */
  						tmp = "enable_seqscan";
  						break;
  					case 'i':	/* indexscan */
  						tmp = "enable_indexscan";
  						break;
  					case 'b':	/* bitmapscan */
  						tmp = "enable_bitmapscan";
  						break;
  					case 't':	/* tidscan */
  						tmp = "enable_tidscan";
  						break;
  					case 'n':	/* nestloop */
  						tmp = "enable_nestloop";
  						break;
  					case 'm':	/* mergejoin */
  						tmp = "enable_mergejoin";
  						break;
  					case 'h':	/* hashjoin */
  						tmp = "enable_hashjoin";
  						break;
  					default:
  						errs++;
  				}
  				if (tmp)
  					SetConfigOption(tmp, "false", ctx, gucsource);
  				break;
  
  			case 'N':
  
  				/*
  				 * N - Don't use newline as a query delimiter
  				 */
  				UseNewLine = 0;
  				break;
  
  			case 'O':
  
  				/*
  				 * allow system table structure modifications
  				 */
  				if (secure)		/* XXX safe to allow from client??? */
  					allowSystemTableMods = true;
  				break;
  
  			case 'P':
  
  				/*
  				 * ignore system indexes
  				 *
  				 * As of PG 7.4 this is safe to allow from the client, since
  				 * it only disables reading the system indexes, not writing
  				 * them. Worst case consequence is slowness.
  				 */
  				IgnoreSystemIndexes(true);
  				break;
  
  			case 'o':
  
  				/*
  				 * o - send output (stdout and stderr) to the given file
  				 */
  				if (secure)
  					StrNCpy(OutputFileName, optarg, MAXPGPATH);
  				break;
  
  			case 'p':
  
  				/*
  				 * p - special flag passed if backend was forked by a
  				 * postmaster.
  				 */
  				if (secure)
  				{
  					dbname = strdup(optarg);
  
  					secure = false;		/* subsequent switches are NOT secure */
  					ctx = PGC_BACKEND;
  					gucsource = PGC_S_CLIENT;
  				}
  				break;
  
  			case 'S':
  
  				/*
  				 * S - amount of sort memory to use in 1k bytes
  				 */
  				SetConfigOption("work_mem", optarg, ctx, gucsource);
  				break;
  
  			case 's':
  
  				/*
  				 * s - report usage statistics (timings) after each query
  				 *
  				 * Since log options are SUSET, we need to postpone unless
  				 * still in secure context
  				 */
  				if (ctx == PGC_BACKEND)
  					PendingConfigOption("log_statement_stats", "true");
  				else
  					SetConfigOption("log_statement_stats", "true",
  									ctx, gucsource);
  				break;
  
  			case 't':
  				/* ---------------
  				 *	tell postgres to report usage statistics (timings) for
  				 *	each query
  				 *
  				 *	-tpa[rser] = print stats for parser time of each query
  				 *	-tpl[anner] = print stats for planner time of each query
  				 *	-te[xecutor] = print stats for executor time of each query
  				 *	caution: -s can not be used together with -t.
  				 * ----------------
  				 */
  				tmp = NULL;
  				switch (optarg[0])
  				{
  					case 'p':
  						if (optarg[1] == 'a')
  							tmp = "log_parser_stats";
  						else if (optarg[1] == 'l')
  							tmp = "log_planner_stats";
  						else
  							errs++;
  						break;
  					case 'e':
  						tmp = "log_executor_stats";
  						break;
  					default:
  						errs++;
  						break;
  				}
  				if (tmp)
  				{
  					if (ctx == PGC_BACKEND)
  						PendingConfigOption(tmp, "true");
  					else
  						SetConfigOption(tmp, "true", ctx, gucsource);
  				}
  				break;
  
  			case 'v':
  				if (secure)
  					FrontendProtocol = (ProtocolVersion) atoi(optarg);
  				break;
  
  			case 'W':
  
  				/*
  				 * wait N seconds to allow attach from a debugger
  				 */
  				pg_usleep(atoi(optarg) * 1000000L);
  				break;
  
  			case 'c':
  			case '-':
  				{
  					char	   *name,
  							   *value;
  
  					ParseLongOption(optarg, &name, &value);
  					if (!value)
  					{
  						if (flag == '-')
  							ereport(ERROR,
  									(errcode(ERRCODE_SYNTAX_ERROR),
  									 errmsg("--%s requires a value",
  											optarg)));
  						else
  							ereport(ERROR,
  									(errcode(ERRCODE_SYNTAX_ERROR),
  									 errmsg("-c %s requires a value",
  											optarg)));
  					}
  
  					/*
  					 * If a SUSET option, must postpone evaluation, unless we
  					 * are still reading secure switches.
  					 */
  					if (ctx == PGC_BACKEND && IsSuperuserConfigOption(name))
  						PendingConfigOption(name, value);
  					else
  						SetConfigOption(name, value, ctx, gucsource);
  					free(name);
  					if (value)
  						free(value);
  					break;
  				}
  
  			default:
  				errs++;
  				break;
  		}
  	}
  
  	/*
  	 * Process any additional GUC variable settings passed in startup packet.
  	 * These are handled exactly like command-line variables.
  	 */
  	if (MyProcPort != NULL)
  	{
  		ListCell   *gucopts = list_head(MyProcPort->guc_options);
  
  		while (gucopts)
  		{
  			char	   *name;
  			char	   *value;
  
  			name = lfirst(gucopts);
  			gucopts = lnext(gucopts);
  
  			value = lfirst(gucopts);
  			gucopts = lnext(gucopts);
  
  			if (IsSuperuserConfigOption(name))
  				PendingConfigOption(name, value);
  			else
  				SetConfigOption(name, value, PGC_BACKEND, PGC_S_CLIENT);
  		}
  	}
  
  	/* Acquire configuration parameters, unless inherited from postmaster */
  	if (!IsUnderPostmaster)
  	{
  		if (!SelectConfigFiles(userDoption, argv[0]))
  			proc_exit(1);
  		/* If timezone is not set, determine what the OS uses */
  		pg_timezone_initialize();
  	}
  
  	/*
  	 * Set up signal handlers and masks.
  	 *
  	 * Note that postmaster blocked all signals before forking child process,
  	 * so there is no race condition whereby we might receive a signal before
  	 * we have set up the handler.
  	 *
  	 * Also note: it's best not to use any signals that are SIG_IGNored in the
  	 * postmaster.	If such a signal arrives before we are able to change the
  	 * handler to non-SIG_IGN, it'll get dropped.  Instead, make a dummy
  	 * handler in the postmaster to reserve the signal. (Of course, this isn't
  	 * an issue for signals that are locally generated, such as SIGALRM and
  	 * SIGPIPE.)
  	 */
  	pqsignal(SIGHUP, SigHupHandler);	/* set flag to read config file */
  	pqsignal(SIGINT, StatementCancelHandler);	/* cancel current query */
  	pqsignal(SIGTERM, die);		/* cancel current query and exit */
  	pqsignal(SIGQUIT, quickdie);	/* hard crash time */
  	pqsignal(SIGALRM, handle_sig_alarm);		/* timeout conditions */
  
  	/*
  	 * Ignore failure to write to frontend. Note: if frontend closes
  	 * connection, we will notice it and exit cleanly when control next
  	 * returns to outer loop.  This seems safer than forcing exit in the midst
  	 * of output during who-knows-what operation...
  	 */
  	pqsignal(SIGPIPE, SIG_IGN);
  	pqsignal(SIGUSR1, CatchupInterruptHandler);
  	pqsignal(SIGUSR2, NotifyInterruptHandler);
  	pqsignal(SIGFPE, FloatExceptionHandler);
  
  	/*
  	 * Reset some signals that are accepted by postmaster but not by backend
  	 */
  	pqsignal(SIGCHLD, SIG_DFL); /* system() requires this on some platforms */
  
  	pqinitmask();
  
  	/* We allow SIGQUIT (quickdie) at all times */
  #ifdef HAVE_SIGPROCMASK
  	sigdelset(&BlockSig, SIGQUIT);
  #else
  	BlockSig &= ~(sigmask(SIGQUIT));
  #endif
  
  	PG_SETMASK(&BlockSig);		/* block everything except SIGQUIT */
  
  
  	if (IsUnderPostmaster)
  	{
  		/* noninteractive case: nothing should be left after switches */
  		if (errs || argc != optind || dbname == NULL)
  		{
  			ereport(FATAL,
  					(errcode(ERRCODE_SYNTAX_ERROR),
  				 errmsg("invalid command-line arguments for server process"),
  			   errhint("Try \"%s --help\" for more information.", argv[0])));
  		}
  
  		BaseInit();
  	}
  	else
  	{
  		/* interactive case: database name can be last arg on command line */
  		if (errs || argc - optind > 1)
  		{
  			ereport(FATAL,
  					(errcode(ERRCODE_SYNTAX_ERROR),
  					 errmsg("%s: invalid command-line arguments",
  							argv[0]),
  			   errhint("Try \"%s --help\" for more information.", argv[0])));
  		}
  		else if (argc - optind == 1)
  			dbname = argv[optind];
  		else if ((dbname = username) == NULL)
  		{
  			ereport(FATAL,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  					 errmsg("%s: no database nor user name specified",
  							argv[0])));
  		}
  
  		/*
  		 * Validate we have been given a reasonable-looking DataDir (if under
  		 * postmaster, assume postmaster did this already).
  		 */
  		Assert(DataDir);
  		ValidatePgVersion(DataDir);
  
  		/* Change into DataDir (if under postmaster, was done already) */
  		ChangeToDataDir();
  
  		/*
  		 * Create lockfile for data directory.
  		 */
  		CreateDataDirLockFile(false);
  
  		BaseInit();
  
  		/*
  		 * Start up xlog for standalone backend, and register to have it
  		 * closed down at exit.
  		 */
  		StartupXLOG();
  		on_shmem_exit(ShutdownXLOG, 0);
  
  		/*
  		 * Read any existing FSM cache file, and register to write one out at
  		 * exit.
  		 */
  		LoadFreeSpaceMap();
  		on_shmem_exit(DumpFreeSpaceMap, 0);
  
  		/*
  		 * We have to build the flat file for pg_database, but not for the
  		 * user and group tables, since we won't try to do authentication.
  		 */
  		BuildFlatFiles(true);
  	}
  
  	/*
  	 * General initialization.
  	 *
  	 * NOTE: if you are tempted to add code in this vicinity, consider putting
  	 * it inside InitPostgres() instead.  In particular, anything that
  	 * involves database access should be there, not here.
  	 */
  	ereport(DEBUG3,
  			(errmsg_internal("InitPostgres")));
  	am_superuser = InitPostgres(dbname, username);
  
  	SetProcessingMode(NormalProcessing);
  
  	/*
  	 * Now that we know if client is a superuser, we can try to apply SUSET
  	 * GUC options that came from the client.
  	 */
  	ctx = am_superuser ? PGC_SUSET : PGC_USERSET;
  
  	if (debug_flag >= 0)
  		set_debug_options(debug_flag, ctx, PGC_S_CLIENT);
  
  	if (guc_names != NIL)
  	{
  		ListCell   *namcell,
  				   *valcell;
  
  		forboth(namcell, guc_names, valcell, guc_values)
  		{
  			char	   *name = (char *) lfirst(namcell);
  			char	   *value = (char *) lfirst(valcell);
  
  			SetConfigOption(name, value, ctx, PGC_S_CLIENT);
  			pfree(name);
  			pfree(value);
  		}
  	}
  
  	/*
  	 * Now all GUC states are fully set up.  Report them to client if
  	 * appropriate.
  	 */
  	BeginReportingGUCOptions();
  
  	/*
  	 * Also set up handler to log session end; we have to wait till now to be
  	 * sure Log_disconnections has its final value.
  	 */
  	if (IsUnderPostmaster && Log_disconnections)
  		on_proc_exit(log_disconnections, 0);
  
  	/*
  	 * Send this backend's cancellation info to the frontend.
  	 */
  	if (whereToSendOutput == DestRemote &&
  		PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
  	{
  		StringInfoData buf;
  
  		pq_beginmessage(&buf, 'K');
  		pq_sendint(&buf, (int32) MyProcPid, sizeof(int32));
  		pq_sendint(&buf, (int32) MyCancelKey, sizeof(int32));
  		pq_endmessage(&buf);
  		/* Need not flush since ReadyForQuery will do it. */
  	}
  
  	/* Welcome banner for standalone case */
  	if (whereToSendOutput == DestDebug)
  		printf("\nPostgreSQL stand-alone backend %s\n", PG_VERSION);
  
  	/*
  	 * Create the memory context we will use in the main loop.
  	 *
  	 * MessageContext is reset once per iteration of the main loop, ie, upon
  	 * completion of processing of each command message from the client.
  	 */
  	MessageContext = AllocSetContextCreate(TopMemoryContext,
  										   "MessageContext",
  										   ALLOCSET_DEFAULT_MINSIZE,
  										   ALLOCSET_DEFAULT_INITSIZE,
  										   ALLOCSET_DEFAULT_MAXSIZE);
  
  	/*
  	 * Remember stand-alone backend startup time
  	 */
  	if (!IsUnderPostmaster)
  		PgStartTime = GetCurrentTimestamp();
  
  	/*
  	 * POSTGRES main processing loop begins here
  	 *
  	 * If an exception is encountered, processing resumes here so we abort the
  	 * current transaction and start a new one.
  	 *
  	 * You might wonder why this isn't coded as an infinite loop around a
  	 * PG_TRY construct.  The reason is that this is the bottom of the
  	 * exception stack, and so with PG_TRY there would be no exception handler
  	 * in force at all during the CATCH part.  By leaving the outermost setjmp
  	 * always active, we have at least some chance of recovering from an error
  	 * during error recovery.  (If we get into an infinite loop thereby, it
  	 * will soon be stopped by overflow of elog.c's internal state stack.)
  	 */
  
  	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
  	{
  		/*
  		 * NOTE: if you are tempted to add more code in this if-block,
  		 * consider the high probability that it should be in
  		 * AbortTransaction() instead.	The only stuff done directly here
  		 * should be stuff that is guaranteed to apply *only* for outer-level
  		 * error recovery, such as adjusting the FE/BE protocol status.
  		 */
  
  		/* Since not using PG_TRY, must reset error stack by hand */
  		error_context_stack = NULL;
  
  		/* Prevent interrupts while cleaning up */
  		HOLD_INTERRUPTS();
  
  		/*
  		 * Forget any pending QueryCancel request, since we're returning to
  		 * the idle loop anyway, and cancel the statement timer if running.
  		 */
  		QueryCancelPending = false;
  		disable_sig_alarm(true);
  		QueryCancelPending = false;		/* again in case timeout occurred */
  
  		/*
  		 * Turn off these interrupts too.  This is only needed here and not in
  		 * other exception-catching places since these interrupts are only
  		 * enabled while we wait for client input.
  		 */
  		DoingCommandRead = false;
  		DisableNotifyInterrupt();
  		DisableCatchupInterrupt();
  
  		/* Make sure libpq is in a good state */
  		pq_comm_reset();
  
  		/* Report the error to the client and/or server log */
  		EmitErrorReport();
  
  		/*
  		 * Make sure debug_query_string gets reset before we possibly clobber
  		 * the storage it points at.
  		 */
  		debug_query_string = NULL;
  
  		/*
  		 * Abort the current transaction in order to recover.
  		 */
  		AbortCurrentTransaction();
  
  		/*
  		 * Now return to normal top-level context and clear ErrorContext for
  		 * next time.
  		 */
  		MemoryContextSwitchTo(TopMemoryContext);
  		FlushErrorState();
  		QueryContext = NULL;
  
  		/*
  		 * If we were handling an extended-query-protocol message, initiate
  		 * skip till next Sync.  This also causes us not to issue
  		 * ReadyForQuery (until we get Sync).
  		 */
  		if (doing_extended_query_message)
  			ignore_till_sync = true;
  
  		/* We don't have a transaction command open anymore */
  		xact_started = false;
  
  		/* Now we can allow interrupts again */
  		RESUME_INTERRUPTS();
  	}
  
  	/* We can now handle ereport(ERROR) */
  	PG_exception_stack = &local_sigjmp_buf;
  
  	PG_SETMASK(&UnBlockSig);
  
  	if (!ignore_till_sync)
  		send_rfq = true;		/* initially, or after error */
  
  	/*
  	 * Non-error queries loop here.
  	 */
  
  	for (;;)
  	{
  		/*
  		 * At top of loop, reset extended-query-message flag, so that any
  		 * errors encountered in "idle" state don't provoke skip.
  		 */
  		doing_extended_query_message = false;
  
  		/*
  		 * Release storage left over from prior query cycle, and create a new
  		 * query input buffer in the cleared MessageContext.
  		 */
  		MemoryContextSwitchTo(MessageContext);
  		MemoryContextResetAndDeleteChildren(MessageContext);
  
  		initStringInfo(&input_message);
  
  		/*
  		 * (1) If we've reached idle state, tell the frontend we're ready for
  		 * a new query.
  		 *
  		 * Note: this includes fflush()'ing the last of the prior output.
  		 *
  		 * This is also a good time to send collected statistics to the
  		 * collector, and to update the PS stats display.  We avoid doing
  		 * those every time through the message loop because it'd slow down
  		 * processing of batched messages, and because we don't want to report
  		 * uncommitted updates (that confuses autovacuum).
  		 */
  		if (send_rfq)
  		{
  			if (IsTransactionOrTransactionBlock())
  			{
  				set_ps_display("idle in transaction");
  				pgstat_report_activity("<IDLE> in transaction");
  			}
  			else
  			{
  				pgstat_report_tabstat();
  
  				set_ps_display("idle");
  				pgstat_report_activity("<IDLE>");
  			}
  
  			ReadyForQuery(whereToSendOutput);
  			send_rfq = false;
  		}
  
  		/*
  		 * (2) Allow asynchronous signals to be executed immediately if they
  		 * come in while we are waiting for client input. (This must be
  		 * conditional since we don't want, say, reads on behalf of COPY FROM
  		 * STDIN doing the same thing.)
  		 */
  		QueryCancelPending = false;		/* forget any earlier CANCEL signal */
  		DoingCommandRead = true;
  
  		/*
  		 * (3) read a command (loop blocks here)
  		 */
  		firstchar = ReadCommand(&input_message);
  
  		/*
  		 * (4) disable async signal conditions again.
  		 */
  		DoingCommandRead = false;
  
  		/*
  		 * (5) check for any other interesting events that happened while we
  		 * slept.
  		 */
  		if (got_SIGHUP)
  		{
  			got_SIGHUP = false;
  			ProcessConfigFile(PGC_SIGHUP);
  		}
  
  		/*
  		 * (6) process the command.  But ignore it if we're skipping till
  		 * Sync.
  		 */
  		if (ignore_till_sync && firstchar != EOF)
  			continue;
  
  		switch (firstchar)
  		{
  			case 'Q':			/* simple query */
  				{
  					const char *query_string;
  
  					query_string = pq_getmsgstring(&input_message);
  					pq_getmsgend(&input_message);
  
  					exec_simple_query(query_string);
  
  					send_rfq = true;
  				}
  				break;
  
  			case 'P':			/* parse */
  				{
  					const char *stmt_name;
  					const char *query_string;
  					int			numParams;
  					Oid		   *paramTypes = NULL;
  
  					stmt_name = pq_getmsgstring(&input_message);
  					query_string = pq_getmsgstring(&input_message);
  					numParams = pq_getmsgint(&input_message, 2);
  					if (numParams > 0)
  					{
  						int			i;
  
  						paramTypes = (Oid *) palloc(numParams * sizeof(Oid));
  						for (i = 0; i < numParams; i++)
  							paramTypes[i] = pq_getmsgint(&input_message, 4);
  					}
  					pq_getmsgend(&input_message);
  
  					exec_parse_message(query_string, stmt_name,
  									   paramTypes, numParams);
  				}
  				break;
  
  			case 'B':			/* bind */
  
  				/*
  				 * this message is complex enough that it seems best to put
  				 * the field extraction out-of-line
  				 */
  				exec_bind_message(&input_message);
  				break;
  
  			case 'E':			/* execute */
  				{
  					const char *portal_name;
  					int			max_rows;
  
  					portal_name = pq_getmsgstring(&input_message);
  					max_rows = pq_getmsgint(&input_message, 4);
  					pq_getmsgend(&input_message);
  
  					exec_execute_message(portal_name, max_rows);
  				}
  				break;
  
  			case 'F':			/* fastpath function call */
  				/* Tell the collector what we're doing */
  				pgstat_report_activity("<FASTPATH> function call");
  
  				/* start an xact for this function invocation */
  				start_xact_command();
  
  				/* switch back to message context */
  				MemoryContextSwitchTo(MessageContext);
  
  				/* set snapshot in case function needs one */
  				ActiveSnapshot = CopySnapshot(GetTransactionSnapshot());
  
  				if (HandleFunctionRequest(&input_message) == EOF)
  				{
  					/* lost frontend connection during F message input */
  
  					/*
  					 * Reset whereToSendOutput to prevent ereport from
  					 * attempting to send any more messages to client.
  					 */
  					if (whereToSendOutput == DestRemote)
  						whereToSendOutput = DestNone;
  
  					proc_exit(0);
  				}
  
  				/* commit the function-invocation transaction */
  				finish_xact_command();
  
  				send_rfq = true;
  				break;
  
  			case 'C':			/* close */
  				{
  					int			close_type;
  					const char *close_target;
  
  					close_type = pq_getmsgbyte(&input_message);
  					close_target = pq_getmsgstring(&input_message);
  					pq_getmsgend(&input_message);
  
  					switch (close_type)
  					{
  						case 'S':
  							if (close_target[0] != '\0')
  								DropPreparedStatement(close_target, false);
  							else
  							{
  								/* special-case the unnamed statement */
  								unnamed_stmt_pstmt = NULL;
  								if (unnamed_stmt_context)
  								{
  									DropDependentPortals(unnamed_stmt_context);
  									MemoryContextDelete(unnamed_stmt_context);
  								}
  								unnamed_stmt_context = NULL;
  							}
  							break;
  						case 'P':
  							{
  								Portal		portal;
  
  								portal = GetPortalByName(close_target);
  								if (PortalIsValid(portal))
  									PortalDrop(portal, false);
  							}
  							break;
  						default:
  							ereport(ERROR,
  									(errcode(ERRCODE_PROTOCOL_VIOLATION),
  								   errmsg("invalid CLOSE message subtype %d",
  										  close_type)));
  							break;
  					}
  
  					if (whereToSendOutput == DestRemote)
  						pq_putemptymessage('3');		/* CloseComplete */
  				}
  				break;
  
  			case 'D':			/* describe */
  				{
  					int			describe_type;
  					const char *describe_target;
  
  					describe_type = pq_getmsgbyte(&input_message);
  					describe_target = pq_getmsgstring(&input_message);
  					pq_getmsgend(&input_message);
  
  					switch (describe_type)
  					{
  						case 'S':
  							exec_describe_statement_message(describe_target);
  							break;
  						case 'P':
  							exec_describe_portal_message(describe_target);
  							break;
  						default:
  							ereport(ERROR,
  									(errcode(ERRCODE_PROTOCOL_VIOLATION),
  								errmsg("invalid DESCRIBE message subtype %d",
  									   describe_type)));
  							break;
  					}
  				}
  				break;
  
  			case 'H':			/* flush */
  				pq_getmsgend(&input_message);
  				if (whereToSendOutput == DestRemote)
  					pq_flush();
  				break;
  
  			case 'S':			/* sync */
  				pq_getmsgend(&input_message);
  				finish_xact_command();
  				send_rfq = true;
  				break;
  
  				/*
  				 * 'X' means that the frontend is closing down the socket. EOF
  				 * means unexpected loss of frontend connection. Either way,
  				 * perform normal shutdown.
  				 */
  			case 'X':
  			case EOF:
  
  				/*
  				 * Reset whereToSendOutput to prevent ereport from attempting
  				 * to send any more messages to client.
  				 */
  				if (whereToSendOutput == DestRemote)
  					whereToSendOutput = DestNone;
  
  				/*
  				 * NOTE: if you are tempted to add more code here, DON'T!
  				 * Whatever you had in mind to do should be set up as an
  				 * on_proc_exit or on_shmem_exit callback, instead. Otherwise
  				 * it will fail to be called during other backend-shutdown
  				 * scenarios.
  				 */
  				proc_exit(0);
  
  			case 'd':			/* copy data */
  			case 'c':			/* copy done */
  			case 'f':			/* copy fail */
  
  				/*
  				 * Accept but ignore these messages, per protocol spec; we
  				 * probably got here because a COPY failed, and the frontend
  				 * is still sending data.
  				 */
  				break;
  
  			default:
  				ereport(FATAL,
  						(errcode(ERRCODE_PROTOCOL_VIOLATION),
  						 errmsg("invalid frontend message type %d",
  								firstchar)));
  		}
  	}							/* end of input-reading loop */
  
  	/* can't get here because the above loop never exits */
  	Assert(false);
  
  	return 1;					/* keep compiler quiet */
  }
  
  #ifndef HAVE_GETRUSAGE
  #include "rusagestub.h"
  #else
  #include <sys/resource.h>
  #endif   /* HAVE_GETRUSAGE */
  
  static struct rusage Save_r;
  static struct timeval Save_t;
  
  void
  ResetUsage(void)
  {
  	getrusage(RUSAGE_SELF, &Save_r);
  	gettimeofday(&Save_t, NULL);
  	ResetBufferUsage();
  	/* ResetTupleCount(); */
  }
  
  void
  ShowUsage(const char *title)
  {
  	StringInfoData str;
  	struct timeval user,
  				sys;
  	struct timeval elapse_t;
  	struct rusage r;
  	char	   *bufusage;
  
  	getrusage(RUSAGE_SELF, &r);
  	gettimeofday(&elapse_t, NULL);
  	memcpy((char *) &user, (char *) &r.ru_utime, sizeof(user));
  	memcpy((char *) &sys, (char *) &r.ru_stime, sizeof(sys));
  	if (elapse_t.tv_usec < Save_t.tv_usec)
  	{
  		elapse_t.tv_sec--;
  		elapse_t.tv_usec += 1000000;
  	}
  	if (r.ru_utime.tv_usec < Save_r.ru_utime.tv_usec)
  	{
  		r.ru_utime.tv_sec--;
  		r.ru_utime.tv_usec += 1000000;
  	}
  	if (r.ru_stime.tv_usec < Save_r.ru_stime.tv_usec)
  	{
  		r.ru_stime.tv_sec--;
  		r.ru_stime.tv_usec += 1000000;
  	}
  
  	/*
  	 * the only stats we don't show here are for memory usage -- i can't
  	 * figure out how to interpret the relevant fields in the rusage struct,
  	 * and they change names across o/s platforms, anyway. if you can figure
  	 * out what the entries mean, you can somehow extract resident set size,
  	 * shared text size, and unshared data and stack sizes.
  	 */
  	initStringInfo(&str);
  
  	appendStringInfo(&str, "! system usage stats:\n");
  	appendStringInfo(&str,
  				"!\t%ld.%06ld elapsed %ld.%06ld user %ld.%06ld system sec\n",
  					 (long) (elapse_t.tv_sec - Save_t.tv_sec),
  					 (long) (elapse_t.tv_usec - Save_t.tv_usec),
  					 (long) (r.ru_utime.tv_sec - Save_r.ru_utime.tv_sec),
  					 (long) (r.ru_utime.tv_usec - Save_r.ru_utime.tv_usec),
  					 (long) (r.ru_stime.tv_sec - Save_r.ru_stime.tv_sec),
  					 (long) (r.ru_stime.tv_usec - Save_r.ru_stime.tv_usec));
  	appendStringInfo(&str,
  					 "!\t[%ld.%06ld user %ld.%06ld sys total]\n",
  					 (long) user.tv_sec,
  					 (long) user.tv_usec,
  					 (long) sys.tv_sec,
  					 (long) sys.tv_usec);
  /* BeOS has rusage but only has some fields, and not these... */
  #if defined(HAVE_GETRUSAGE)
  	appendStringInfo(&str,
  					 "!\t%ld/%ld [%ld/%ld] filesystem blocks in/out\n",
  					 r.ru_inblock - Save_r.ru_inblock,
  	/* they only drink coffee at dec */
  					 r.ru_oublock - Save_r.ru_oublock,
  					 r.ru_inblock, r.ru_oublock);
  	appendStringInfo(&str,
  			  "!\t%ld/%ld [%ld/%ld] page faults/reclaims, %ld [%ld] swaps\n",
  					 r.ru_majflt - Save_r.ru_majflt,
  					 r.ru_minflt - Save_r.ru_minflt,
  					 r.ru_majflt, r.ru_minflt,
  					 r.ru_nswap - Save_r.ru_nswap,
  					 r.ru_nswap);
  	appendStringInfo(&str,
  		 "!\t%ld [%ld] signals rcvd, %ld/%ld [%ld/%ld] messages rcvd/sent\n",
  					 r.ru_nsignals - Save_r.ru_nsignals,
  					 r.ru_nsignals,
  					 r.ru_msgrcv - Save_r.ru_msgrcv,
  					 r.ru_msgsnd - Save_r.ru_msgsnd,
  					 r.ru_msgrcv, r.ru_msgsnd);
  	appendStringInfo(&str,
  			 "!\t%ld/%ld [%ld/%ld] voluntary/involuntary context switches\n",
  					 r.ru_nvcsw - Save_r.ru_nvcsw,
  					 r.ru_nivcsw - Save_r.ru_nivcsw,
  					 r.ru_nvcsw, r.ru_nivcsw);
  #endif   /* HAVE_GETRUSAGE */
  
  	bufusage = ShowBufferUsage();
  	appendStringInfo(&str, "! buffer usage stats:\n%s", bufusage);
  	pfree(bufusage);
  
  	/* remove trailing newline */
  	if (str.data[str.len - 1] == '\n')
  		str.data[--str.len] = '\0';
  
  	ereport(LOG,
  			(errmsg_internal("%s", title),
  			 errdetail("%s", str.data)));
  
  	pfree(str.data);
  }
  
  /*
   * on_proc_exit handler to log end of session
   */
  static void
  log_disconnections(int code, Datum arg)
  {
  	Port	   *port = MyProcPort;
  	struct timeval end;
  	int			hours,
  				minutes,
  				seconds;
  
  	gettimeofday(&end, NULL);
  	if (end.tv_usec < port->session_start.tv_usec)
  	{
  		end.tv_sec--;
  		end.tv_usec += 1000000;
  	}
  	end.tv_sec -= port->session_start.tv_sec;
  	end.tv_usec -= port->session_start.tv_usec;
  
  	/* for stricter accuracy here we could round - this is close enough */
  	hours = end.tv_sec / SECS_PER_HOUR;
  	end.tv_sec %= SECS_PER_HOUR;
  	minutes = end.tv_sec / SECS_PER_MINUTE;
  	seconds = end.tv_sec % SECS_PER_MINUTE;
  
  	ereport(LOG,
  			(errmsg("disconnection: session time: %d:%02d:%02d.%02d "
  					"user=%s database=%s host=%s%s%s",
  					hours, minutes, seconds, (int) (end.tv_usec / 10000),
  					port->user_name, port->database_name, port->remote_host,
  				  port->remote_port[0] ? " port=" : "", port->remote_port)));
  }
  