postgres.c

/*-------------------------------------------------------------------------
 *
 * postgres.c
 *	  POSTGRES C Backend Interface
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.552 2008/05/12 20:02:01 alvherre Exp $
 *
 * NOTES
 *	  this is the "main" module of the postgres backend and
 *	  hence the main module of the "traffic cop".
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <time.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#ifdef HAVE_SYS_RESOURCE_H
#include <sys/time.h>
#include <sys/resource.h>
#endif
#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif

#ifndef HAVE_GETRUSAGE
#include "rusagestub.h"
#endif

#include "access/printtup.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "commands/async.h"
#include "commands/prepare.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "nodes/print.h"
#include "optimizer/planner.h"
#include "parser/analyze.h"
#include "parser/parser.h"
#include "postmaster/autovacuum.h"
#include "rewrite/rewriteHandler.h"
#include "storage/bufmgr.h"
#include "storage/freespace.h"
#include "storage/ipc.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/lsyscache.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"
#include "utils/snapmgr.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;

int			log_statement = LOGSTMT_NONE;

/* GUC variable for maximum stack depth (measured in kilobytes) */
int			max_stack_depth = 100;

/* wait N seconds to allow attach from a debugger */
int			PostAuthDelay = 0;



/* ----------------
 *		private variables
 * ----------------
 */

/* max_stack_depth converted to bytes for speed of checking */
static long max_stack_depth_bytes = 100 * 1024L;

/*
 * Stack base pointer -- initialized by PostgresMain. This is not static
 * so that PL/Java can modify 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 CachedPlanSource *unnamed_stmt_psrc = NULL;

/* workspace for building a new unnamed statement in */
static MemoryContext unnamed_stmt_context = 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	interactive_getc(void);
static int	SocketBackend(StringInfo inBuf);
static int	ReadCommand(StringInfo inBuf);
static List *pg_rewrite_query(Query *query);
static bool check_log_statement(List *stmt_list);
static int	errdetail_execute(List *raw_parsetree_list);
static int	errdetail_params(ParamListInfo params);
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 drop_unnamed_stmt(void);
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);

	resetStringInfo(inBuf);

	if (UseNewLine)
	{
		/*
		 * if we are using \n as a delimiter, then read characters until the
		 * \n.
		 */
		while ((c = interactive_getc()) != 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 = interactive_getc()) != EOF)
			appendStringInfoChar(inBuf, (char) c);

		/* No input before EOF signal means time to quit. */
		if (inBuf->len == 0)
			end = true;
	}

	if (end)
		return EOF;

	/*
	 * otherwise we have a user query so process it.
	 */

	/* 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';
}

/*
 * interactive_getc -- collect one character from stdin
 *
 * Even though we are not reading from a "client" process, we still want to
 * respond to signals, particularly SIGTERM/SIGQUIT.  Hence we must use
 * prepare_for_client_read and client_read_ended.
 */
static int
interactive_getc(void)
{
	int			c;

	prepare_for_client_read();
	c = getc(stdin);
	client_read_ended();
	return c;
}

/* ----------------
 *	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,
															query_string,
															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");

#ifdef COPY_PARSE_PLAN_TREES
	/* Optional debugging check: pass raw parsetrees through copyObject() */
	{
		List	   *new_list = (List *) copyObject(raw_parsetree_list);

		/* This checks both copyObject() and the equal() routines... */
		if (!equal(new_list, raw_parsetree_list))
			elog(WARNING, "copyObject() failed to produce an equal raw parse tree");
		else
			raw_parsetree_list = new_list;
	}
#endif

	return raw_parsetree_list;
}

/*
 * 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, const char *query_string,
					   Oid *paramTypes, int numParams)
{
	Query	   *query;
	List	   *querytree_list;

	/*
	 * (1) Perform parse analysis.
	 */
	if (log_parser_stats)
		ResetUsage();

	query = parse_analyze(parsetree, query_string, paramTypes, numParams);

	if (log_parser_stats)
		ShowUsage("PARSE ANALYSIS STATISTICS");

	/*
	 * (2) Rewrite the queries, as necessary
	 */
	querytree_list = pg_rewrite_query(query);

	return querytree_list;
}

/*
 * Perform rewriting of a query produced by parse analysis.
 *
 * Note: query must just have come from the parser, because we do not do
 * AcquireRewriteLocks() on it.
 */
static List *
pg_rewrite_query(Query *query)
{
	List	   *querytree_list;

	if (log_parser_stats)
		ResetUsage();

	if (Debug_print_parse)
		elog_node_display(DEBUG1, "parse tree", query,
						  Debug_pretty_print);

	if (query->commandType == CMD_UTILITY)
	{
		/* don't rewrite utilities, just dump 'em into result list */
		querytree_list = list_make1(query);
	}
	else
	{
		/* rewrite regular queries */
		querytree_list = QueryRewrite(query);
	}

	if (log_parser_stats)
		ShowUsage("REWRITER STATISTICS");

#ifdef COPY_PARSE_PLAN_TREES
	/* Optional debugging check: pass querytree output through copyObject() */
	{
		List	   *new_list;

		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 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.
 * This is a thin wrapper around planner() and takes the same parameters.
 */
PlannedStmt *
pg_plan_query(Query *querytree, int cursorOptions, ParamListInfo boundParams)
{
	PlannedStmt *plan;

	/* Utility commands have no plans. */
	if (querytree->commandType == CMD_UTILITY)
		return NULL;

	if (log_planner_stats)
		ResetUsage();

	/* call the optimizer */
	plan = planner(querytree, cursorOptions, boundParams);

	if (log_planner_stats)
		ShowUsage("PLANNER STATISTICS");

#ifdef COPY_PARSE_PLAN_TREES
	/* Optional debugging check: pass plan output through copyObject() */
	{
		PlannedStmt *new_plan = (PlannedStmt *) 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.)
 *
 * Normal optimizable statements generate PlannedStmt entries in the result
 * list.  Utility statements are simply represented by their statement nodes.
 */
List *
pg_plan_queries(List *querytrees, int cursorOptions, ParamListInfo boundParams,
				bool needSnapshot)
{
	List	   *stmt_list = NIL;
	ListCell   *query_list;
	bool		snapshot_set = false;

	foreach(query_list, querytrees)
	{
		Query	   *query = (Query *) lfirst(query_list);
		Node	   *stmt;

		if (query->commandType == CMD_UTILITY)
		{
			/* Utility commands have no plans. */
			stmt = query->utilityStmt;
		}
		else
		{
			if (needSnapshot && !snapshot_set)
			{
				PushActiveSnapshot(GetTransactionSnapshot());
				snapshot_set = true;
			}

			stmt = (Node *) pg_plan_query(query, cursorOptions,
										  boundParams);
		}

		stmt_list = lappend(stmt_list, stmt);
	}

	if (snapshot_set)
		PopActiveSnapshot();

	return stmt_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;
	bool		save_log_statement_stats = log_statement_stats;
	bool		was_logged = false;
	bool		isTopLevel;
	char		msec_str[32];

	/*
	 * Report query to various monitoring facilities.
	 */
	debug_query_string = query_string;

	pgstat_report_activity(query_string);

	/*
	 * We use save_log_statement_stats so ShowUsage doesn't report incorrect
	 * results because ResetUsage wasn't called.
	 */
	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.)
	 */
	drop_unnamed_stmt();

	/*
	 * Switch to appropriate context for constructing parsetrees.
	 */
	oldcontext = MemoryContextSwitchTo(MessageContext);

	/*
	 * 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);

	/* Log immediately if dictated by log_statement */
	if (check_log_statement(parsetree_list))
	{
		ereport(LOG,
				(errmsg("statement: %s", query_string),
				 errhidestmt(true),
				 errdetail_execute(parsetree_list)));
		was_logged = true;
	}

	/*
	 * Switch back to transaction context to enter the loop.
	 */
	MemoryContextSwitchTo(oldcontext);

	/*
	 * We'll tell PortalRun it's a top-level command iff there's exactly one
	 * raw parsetree.  If more than one, it's effectively a transaction block
	 * and we want PreventTransactionChain to reject unsafe commands. (Note:
	 * we're assuming that query rewrite cannot add commands that are
	 * significant to PreventTransactionChain.)
	 */
	isTopLevel = (list_length(parsetree_list) == 1);

	/*
	 * 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, false);

		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, query_string,
												NULL, 0);

		plantree_list = pg_plan_queries(querytree_list, 0, 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);
		/* Don't display the portal in pg_cursors */
		portal->visible = false;

		/*
		 * We don't have to copy anything into the portal, because everything
		 * we are passsing here is in MessageContext, which will outlive the
		 * portal anyway.
		 */
		PortalDefineQuery(portal,
						  NULL,
						  query_string,
						  commandTag,
						  plantree_list,
						  NULL);

		/*
		 * 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,
						 isTopLevel,
						 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);

	/*
	 * Emit duration logging if appropriate.
	 */
	switch (check_log_duration(msec_str, was_logged))
	{
		case 1:
			ereport(LOG,
					(errmsg("duration: %s ms", msec_str),
					 errhidestmt(true)));
			break;
		case 2:
			ereport(LOG,
					(errmsg("duration: %s ms  statement: %s",
							msec_str, query_string),
					 errhidestmt(true),
					 errdetail_execute(parsetree_list)));
			break;
	}

	if (save_log_statement_stats)
		ShowUsage("QUERY STATISTICS");

	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;
	Node	   *raw_parse_tree;
	const char *commandTag;
	List	   *querytree_list,
			   *stmt_list;
	bool		is_named;
	bool		fully_planned;
	bool		save_log_statement_stats = log_statement_stats;
	char		msec_str[32];

	/*
	 * Report query to various monitoring facilities.
	 */
	debug_query_string = query_string;

	pgstat_report_activity(query_string);

	set_ps_display("PARSE", false);

	if (save_log_statement_stats)
		ResetUsage();

	ereport(DEBUG2,
			(errmsg("parse %s: %s",
					*stmt_name ? 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 plancache entry; 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 create the plancache
	 * entry's context here, and do all the parsing work 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 */
		drop_unnamed_stmt();
		/* Create context for parsing/planning */
		unnamed_stmt_context =
			AllocSetContextCreate(CacheMemoryContext,
								  "unnamed prepared statement",
								  ALLOCSET_DEFAULT_MINSIZE,
								  ALLOCSET_DEFAULT_INITSIZE,
								  ALLOCSET_DEFAULT_MAXSIZE);
		oldcontext = MemoryContextSwitchTo(unnamed_stmt_context);
	}

	/*
	 * 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)
	{
		Query	   *query;
		int			i;

		raw_parse_tree = (Node *) linitial(parsetree_list);

		/*
		 * Get the command name for possible use in status display.
		 */
		commandTag = CreateCommandTag(raw_parse_tree);

		/*
		 * 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(raw_parse_tree))
			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().
		 *
		 * XXX must use copyObject here since parse analysis scribbles on its
		 * input, and we need the unmodified raw parse tree for possible
		 * replanning later.
		 */
		if (log_parser_stats)
			ResetUsage();

		query = parse_analyze_varparams(copyObject(raw_parse_tree),
										query_string,
										&paramTypes,
										&numParams);

		/*
		 * Check all parameter types got determined.
		 */
		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)));
		}

		if (log_parser_stats)
			ShowUsage("PARSE ANALYSIS STATISTICS");

		querytree_list = pg_rewrite_query(query);

		/*
		 * If this is the unnamed statement and it has parameters, defer query
		 * planning until Bind.  Otherwise do it now.
		 */
		if (!is_named && numParams > 0)
		{
			stmt_list = querytree_list;
			fully_planned = false;
		}
		else
		{
			stmt_list = pg_plan_queries(querytree_list, 0, NULL, true);
			fully_planned = true;
		}
	}
	else
	{
		/* Empty input string.	This is legal. */
		raw_parse_tree = NULL;
		commandTag = NULL;
		stmt_list = NIL;
		fully_planned = true;
	}

	/* 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,
							   raw_parse_tree,
							   query_string,
							   commandTag,
							   paramTypes,
							   numParams,
							   0,		/* default cursor options */
							   stmt_list,
							   false);
	}
	else
	{
		/*
		 * paramTypes and query_string need to be copied into
		 * unnamed_stmt_context.  The rest is there already
		 */
		Oid		   *newParamTypes;

		if (numParams > 0)
		{
			newParamTypes = (Oid *) palloc(numParams * sizeof(Oid));
			memcpy(newParamTypes, paramTypes, numParams * sizeof(Oid));
		}
		else
			newParamTypes = NULL;

		unnamed_stmt_psrc = FastCreateCachedPlan(raw_parse_tree,
												 pstrdup(query_string),
												 commandTag,
												 newParamTypes,
												 numParams,
												 0,		/* cursor options */
												 stmt_list,
												 fully_planned,
												 true,
												 unnamed_stmt_context);
		/* context now belongs to the plancache entry */
		unnamed_stmt_context = NULL;
	}

	MemoryContextSwitchTo(oldcontext);

	/*
	 * 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');

	/*
	 * Emit duration logging if appropriate.
	 */
	switch (check_log_duration(msec_str, false))
	{
		case 1:
			ereport(LOG,
					(errmsg("duration: %s ms", msec_str),
					 errhidestmt(true)));
			break;
		case 2:
			ereport(LOG,
					(errmsg("duration: %s ms  parse %s: %s",
							msec_str,
							*stmt_name ? stmt_name : "<unnamed>",
							query_string),
					 errhidestmt(true)));
			break;
	}

	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;
	CachedPlanSource *psrc;
	CachedPlan *cplan;
	Portal		portal;
	char	   *query_string;
	char	   *saved_stmt_name;
	ParamListInfo params;
	List	   *plan_list;
	MemoryContext oldContext;
	bool		save_log_statement_stats = log_statement_stats;
	char		msec_str[32];

	/* Get the fixed part of the message */
	portal_name = pq_getmsgstring(input_message);
	stmt_name = pq_getmsgstring(input_message);

	ereport(DEBUG2,
			(errmsg("bind %s to %s",
					*portal_name ? portal_name : "<unnamed>",
					*stmt_name ? stmt_name : "<unnamed>")));

	/* Find prepared statement */
	if (stmt_name[0] != '\0')
	{
		PreparedStatement *pstmt;

		pstmt = FetchPreparedStatement(stmt_name, true);
		psrc = pstmt->plansource;
	}
	else
	{
		/* special-case the unnamed statement */
		psrc = unnamed_stmt_psrc;
		if (!psrc)
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_PSTATEMENT),
					 errmsg("unnamed prepared statement does not exist")));
	}

	/*
	 * Report query to various monitoring facilities.
	 */
	debug_query_string = psrc->query_string ? psrc->query_string : "<BIND>";

	pgstat_report_activity(debug_query_string);

	set_ps_display("BIND", false);

	if (save_log_statement_stats)
		ResetUsage();

	/*
	 * 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 parameter format codes */
	numPFormats = pq_getmsgint(input_message, 2);
	if (numPFormats > 0)
	{
		int			i;

		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)));

	if (numParams != psrc->num_params)
		ereport(ERROR,
				(errcode(ERRCODE_PROTOCOL_VIOLATION),
				 errmsg("bind message supplies %d parameters, but prepared statement \"%s\" requires %d",
						numParams, stmt_name, psrc->num_params)));

	/*
	 * 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() &&
		(!IsTransactionExitStmt(psrc->raw_parse_tree) ||
		 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);

	/*
	 * Prepare to copy stuff into the portal's memory context.  We do all this
	 * copying first, because it could possibly fail (out-of-memory) and we
	 * don't want a failure to occur between RevalidateCachedPlan and
	 * PortalDefineQuery; that would result in leaking our plancache refcount.
	 */
	oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));

	/* Copy the plan's query string, if available, into the portal */
	query_string = psrc->query_string;
	if (query_string)
		query_string = pstrdup(query_string);

	/* Likewise make a copy of the statement name, unless it's unnamed */
	if (stmt_name[0])
		saved_stmt_name = pstrdup(stmt_name);
	else
		saved_stmt_name = NULL;

	/*
	 * Fetch parameters, if any, and store in the portal's memory context.
	 */
	if (numParams > 0)
	{
		int			paramno;

		/* sizeof(ParamListInfoData) includes the first array element */
		params = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
								   (numParams - 1) *sizeof(ParamExternData));
		params->numParams = numParams;

		for (paramno = 0; paramno < numParams; paramno++)
		{
			Oid			ptype = psrc->param_types[paramno];
			int32		plength;
			Datum		pval;
			bool		isNull;
			StringInfoData pbuf;
			char		csave;
			int16		pformat;

			plength = pq_getmsgint(input_message, 4);
			isNull = (plength == -1);

			if (!isNull)
			{
				const char *pvalue = pq_getmsgbytes(input_message, plength);

				/*
				 * 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';
			}
			else
			{
				pbuf.data = NULL;		/* keep compiler quiet */
				csave = 0;
			}

			if (numPFormats > 1)
				pformat = pformats[paramno];
			else if (numPFormats > 0)
				pformat = pformats[0];
			else
				pformat = 0;	/* default = text */

			if (pformat == 0)	/* text mode */
			{
				Oid			typinput;
				Oid			typioparam;
				char	   *pstring;

				getTypeInputInfo(ptype, &typinput, &typioparam);

				/*
				 * We have to do encoding conversion before calling the
				 * typinput routine.
				 */
				if (isNull)
					pstring = NULL;
				else
					pstring = pg_client_to_server(pbuf.data, plength);

				pval = OidInputFunctionCall(typinput, pstring, typioparam, -1);

				/* Free result of encoding conversion, if any */
				if (pstring && pstring != pbuf.data)
					pfree(pstring);
			}
			else if (pformat == 1)		/* binary mode */
			{
				Oid			typreceive;
				Oid			typioparam;
				StringInfo	bufptr;

				/*
				 * Call the parameter type's binary input converter
				 */
				getTypeBinaryInputInfo(ptype, &typreceive, &typioparam);

				if (isNull)
					bufptr = NULL;
				else
					bufptr = &pbuf;

				pval = OidReceiveFunctionCall(typreceive, bufptr, typioparam, -1);

				/* Trouble if it didn't eat the whole buffer */
				if (!isNull && pbuf.cursor != pbuf.len)
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
							 errmsg("incorrect binary data format in bind parameter %d",
									paramno + 1)));
			}
			else
			{
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
						 errmsg("unsupported format code: %d",
								pformat)));
				pval = 0;		/* keep compiler quiet */
			}

			/* Restore message buffer contents */
			if (!isNull)
				pbuf.data[plength] = csave;

			params->params[paramno].value = pval;
			params->params[paramno].isnull = isNull;

			/*
			 * We mark the params as CONST.  This has no effect if we already
			 * did planning, but if we didn't, it licenses the planner to
			 * substitute the parameters directly into the one-shot plan we
			 * will generate below.
			 */
			params->params[paramno].pflags = PARAM_FLAG_CONST;
			params->params[paramno].ptype = ptype;
		}
	}
	else
		params = NULL;

	/* Done storing stuff in portal's context */
	MemoryContextSwitchTo(oldContext);

	/* Get the result format codes */
	numRFormats = pq_getmsgint(input_message, 2);
	if (numRFormats > 0)
	{
		int			i;

		rformats = (int16 *) palloc(numRFormats * sizeof(int16));
		for (i = 0; i < numRFormats; i++)
			rformats[i] = pq_getmsgint(input_message, 2);
	}

	pq_getmsgend(input_message);

	if (psrc->fully_planned)
	{
		/*
		 * Revalidate the cached plan; this may result in replanning.  Any
		 * cruft will be generated in MessageContext.  The plan refcount will
		 * be assigned to the Portal, so it will be released at portal
		 * destruction.
		 */
		cplan = RevalidateCachedPlan(psrc, false);
		plan_list = cplan->stmt_list;
	}
	else
	{
		List	   *query_list;

		/*
		 * Revalidate the cached plan; this may result in redoing parse
		 * analysis and rewriting (but not planning).  Any cruft will be
		 * generated in MessageContext.  The plan refcount is assigned to
		 * CurrentResourceOwner.
		 */
		cplan = RevalidateCachedPlan(psrc, true);

		/*
		 * We didn't plan the query before, so do it now.  This allows the
		 * planner to make use of the concrete parameter values we now have.
		 * Because we use PARAM_FLAG_CONST, the plan is good only for this set
		 * of param values, and so we generate the plan in the portal's own
		 * memory context where it will be thrown away after use. As in
		 * exec_parse_message, we make no attempt to recover planner temporary
		 * memory until the end of the operation.
		 *
		 * XXX because the planner has a bad habit of scribbling on its input,
		 * we have to make a copy of the parse trees.  FIXME someday.
		 */
		oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
		query_list = copyObject(cplan->stmt_list);
		plan_list = pg_plan_queries(query_list, 0, params, true);
		MemoryContextSwitchTo(oldContext);

		/* We no longer need the cached plan refcount ... */
		ReleaseCachedPlan(cplan, true);
		/* ... and we don't want the portal to depend on it, either */
		cplan = NULL;
	}

	/*
	 * Define portal and start execution.
	 */
	PortalDefineQuery(portal,
					  saved_stmt_name,
					  query_string,
					  psrc->commandTag,
					  plan_list,
					  cplan);

	PortalStart(portal, params, InvalidSnapshot);

	/*
	 * Apply the result format requests to the portal.
	 */
	PortalSetResultFormat(portal, numRFormats, rformats);

	/*
	 * Send BindComplete.
	 */
	if (whereToSendOutput == DestRemote)
		pq_putemptymessage('2');

	/*
	 * Emit duration logging if appropriate.
	 */
	switch (check_log_duration(msec_str, false))
	{
		case 1:
			ereport(LOG,
					(errmsg("duration: %s ms", msec_str),
					 errhidestmt(true)));
			break;
		case 2:
			ereport(LOG,
					(errmsg("duration: %s ms  bind %s%s%s: %s",
							msec_str,
							*stmt_name ? stmt_name : "<unnamed>",
							*portal_name ? "/" : "",
							*portal_name ? portal_name : "",
			psrc->query_string ? psrc->query_string : "<source not stored>"),
					 errhidestmt(true),
					 errdetail_params(params)));
			break;
	}

	if (save_log_statement_stats)
		ShowUsage("BIND MESSAGE STATISTICS");

	debug_query_string = NULL;
}

/*
 * 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];
	const char *sourceText;
	const char *prepStmtName;
	ParamListInfo portalParams;
	bool		save_log_statement_stats = log_statement_stats;
	bool		is_xact_command;
	bool		execute_is_fetch;
	bool		was_logged = false;
	char		msec_str[32];

	/* 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 the original query was a null string, just return
	 * EmptyQueryResponse.
	 */
	if (portal->commandTag == NULL)
	{
		Assert(portal->stmts == NIL);
		NullCommand(dest);
		return;
	}

	/* Does the portal contain a transaction command? */
	is_xact_command = IsTransactionStmtList(portal->stmts);

	/*
	 * We must copy the sourceText and prepStmtName into MessageContext in
	 * case the portal is destroyed during finish_xact_command. Can avoid the
	 * copy if it's not an xact command, though.
	 */
	if (is_xact_command)
	{
		sourceText = portal->sourceText ? pstrdup(portal->sourceText) : NULL;
		if (portal->prepStmtName)
			prepStmtName = pstrdup(portal->prepStmtName);
		else
			prepStmtName = "<unnamed>";

		/*
		 * An xact command shouldn't have any parameters, which is a good
		 * thing because they wouldn't be around after finish_xact_command.
		 */
		portalParams = NULL;
	}
	else
	{
		sourceText = portal->sourceText;
		if (portal->prepStmtName)
			prepStmtName = portal->prepStmtName;
		else
			prepStmtName = "<unnamed>";
		portalParams = portal->portalParams;
	}

	/*
	 * Report query to various monitoring facilities.
	 */
	debug_query_string = sourceText ? sourceText : "<EXECUTE>";

	pgstat_report_activity(debug_query_string);

	set_ps_display(portal->commandTag, false);

	if (save_log_statement_stats)
		ResetUsage();

	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 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.
	 */
	execute_is_fetch = !portal->atStart;

	/* Log immediately if dictated by log_statement */
	if (check_log_statement(portal->stmts))
	{
		ereport(LOG,
				(errmsg("%s %s%s%s%s%s",
						execute_is_fetch ?
						_("execute fetch from") :
						_("execute"),
						prepStmtName,
						*portal_name ? "/" : "",
						*portal_name ? portal_name : "",
						sourceText ? ": " : "",
						sourceText ? sourceText : ""),
				 errhidestmt(true),
				 errdetail_params(portalParams)));
		was_logged = true;
	}

	/*
	 * 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->stmts))
		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,
						  true, /* always top level */
						  receiver,
						  receiver,
						  completionTag);

	(*receiver->rDestroy) (receiver);

	if (completed)
	{
		if (is_xact_command)
		{
			/*
			 * 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');
	}

	/*
	 * Emit duration logging if appropriate.
	 */
	switch (check_log_duration(msec_str, was_logged))
	{
		case 1:
			ereport(LOG,
					(errmsg("duration: %s ms", msec_str),
					 errhidestmt(true)));
			break;
		case 2:
			ereport(LOG,
					(errmsg("duration: %s ms  %s %s%s%s%s%s",
							msec_str,
							execute_is_fetch ?
							_("execute fetch from") :
							_("execute"),
							prepStmtName,
							*portal_name ? "/" : "",
							*portal_name ? portal_name : "",
							sourceText ? ": " : "",
							sourceText ? sourceText : ""),
					 errhidestmt(true),
					 errdetail_params(portalParams)));
			break;
	}

	if (save_log_statement_stats)
		ShowUsage("EXECUTE MESSAGE STATISTICS");

	debug_query_string = NULL;
}

/*
 * check_log_statement
 *		Determine whether command should be logged because of log_statement
 *
 * parsetree_list can be either raw grammar output or a list of planned
 * statements
 */
static bool
check_log_statement(List *stmt_list)
{
	ListCell   *stmt_item;

	if (log_statement == LOGSTMT_NONE)
		return false;
	if (log_statement == LOGSTMT_ALL)
		return true;

	/* Else we have to inspect the statement(s) to see whether to log */
	foreach(stmt_item, stmt_list)
	{
		Node	   *stmt = (Node *) lfirst(stmt_item);

		if (GetCommandLogLevel(stmt) <= log_statement)
			return true;
	}

	return false;
}

/*
 * check_log_duration
 *		Determine whether current command's duration should be logged
 *
 * Returns:
 *		0 if no logging is needed
 *		1 if just the duration should be logged
 *		2 if duration and query details should be logged
 *
 * If logging is needed, the duration in msec is formatted into msec_str[],
 * which must be a 32-byte buffer.
 *
 * was_logged should be TRUE if caller already logged query details (this
 * essentially prevents 2 from being returned).
 */
int
check_log_duration(char *msec_str, bool was_logged)
{
	if (log_duration || log_min_duration_statement >= 0)
	{
		long		secs;
		int			usecs;
		int			msecs;
		bool		exceeded;

		TimestampDifference(GetCurrentStatementStartTimestamp(),
							GetCurrentTimestamp(),
							&secs, &usecs);
		msecs = usecs / 1000;

		/*
		 * This odd-looking test for log_min_duration_statement being exceeded
		 * is designed to avoid integer overflow with very long durations:
		 * don't compute secs * 1000 until we've verified it will fit in int.
		 */
		exceeded = (log_min_duration_statement == 0 ||
					(log_min_duration_statement > 0 &&
					 (secs > log_min_duration_statement / 1000 ||
					  secs * 1000 + msecs >= log_min_duration_statement)));

		if (exceeded || log_duration)
		{
			snprintf(msec_str, 32, "%ld.%03d",
					 secs * 1000 + msecs, usecs % 1000);
			if (exceeded && !was_logged)
				return 2;
			else
				return 1;
		}
	}

	return 0;
}

/*
 * errdetail_execute
 *
 * Add an errdetail() line showing the query referenced by an EXECUTE, if any.
 * The argument is the raw parsetree list.
 */
static int
errdetail_execute(List *raw_parsetree_list)
{
	ListCell   *parsetree_item;

	foreach(parsetree_item, raw_parsetree_list)
	{
		Node	   *parsetree = (Node *) lfirst(parsetree_item);

		if (IsA(parsetree, ExecuteStmt))
		{
			ExecuteStmt *stmt = (ExecuteStmt *) parsetree;
			PreparedStatement *pstmt;

			pstmt = FetchPreparedStatement(stmt->name, false);
			if (pstmt && pstmt->plansource->query_string)
			{
				errdetail("prepare: %s", pstmt->plansource->query_string);
				return 0;
			}
		}
	}

	return 0;
}

/*
 * errdetail_params
 *
 * Add an errdetail() line showing bind-parameter data, if available.
 */
static int
errdetail_params(ParamListInfo params)
{
	/* We mustn't call user-defined I/O functions when in an aborted xact */
	if (params && params->numParams > 0 && !IsAbortedTransactionBlockState())
	{
		StringInfoData param_str;
		MemoryContext oldcontext;
		int			paramno;

		/* Make sure any trash is generated in MessageContext */
		oldcontext = MemoryContextSwitchTo(MessageContext);

		initStringInfo(&param_str);

		for (paramno = 0; paramno < params->numParams; paramno++)
		{
			ParamExternData *prm = &params->params[paramno];
			Oid			typoutput;
			bool		typisvarlena;
			char	   *pstring;
			char	   *p;

			appendStringInfo(&param_str, "%s$%d = ",
							 paramno > 0 ? ", " : "",
							 paramno + 1);

			if (prm->isnull || !OidIsValid(prm->ptype))
			{
				appendStringInfoString(&param_str, "NULL");
				continue;
			}

			getTypeOutputInfo(prm->ptype, &typoutput, &typisvarlena);

			pstring = OidOutputFunctionCall(typoutput, prm->value);

			appendStringInfoCharMacro(&param_str, '\'');
			for (p = pstring; *p; p++)
			{
				if (*p == '\'') /* double single quotes */
					appendStringInfoCharMacro(&param_str, *p);
				appendStringInfoCharMacro(&param_str, *p);
			}
			appendStringInfoCharMacro(&param_str, '\'');

			pfree(pstring);
		}

		errdetail("parameters: %s", param_str.data);

		pfree(param_str.data);

		MemoryContextSwitchTo(oldcontext);
	}

	return 0;
}

/*
 * exec_describe_statement_message
 *
 * Process a "Describe" message for a prepared statement
 */
static void
exec_describe_statement_message(const char *stmt_name)
{
	CachedPlanSource *psrc;
	StringInfoData buf;
	int			i;

	/*
	 * 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')
	{
		PreparedStatement *pstmt;

		pstmt = FetchPreparedStatement(stmt_name, true);
		psrc = pstmt->plansource;
	}
	else
	{
		/* special-case the unnamed statement */
		psrc = unnamed_stmt_psrc;
		if (!psrc)
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_PSTATEMENT),
					 errmsg("unnamed prepared statement does not exist")));
	}

	/* Prepared statements shouldn't have changeable result descs */
	Assert(psrc->fixed_result);

	/*
	 * If we are in aborted transaction state, we can't run
	 * SendRowDescriptionMessage(), because that needs catalog accesses. (We
	 * can't do RevalidateCachedPlan, either, but that's a lesser problem.)
	 * 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() &&
		psrc->resultDesc)
		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, psrc->num_params, 2);

	for (i = 0; i < psrc->num_params; i++)
	{
		Oid			ptype = psrc->param_types[i];

		pq_sendint(&buf, (int) ptype, 4);
	}
	pq_endmessage(&buf);

	/*
	 * Next send RowDescription or NoData to describe the result...
	 */
	if (psrc->resultDesc)
	{
		CachedPlan *cplan;
		List	   *tlist;

		/* Make sure the plan is up to date */
		cplan = RevalidateCachedPlan(psrc, true);

		/* Get the primary statement and find out what it returns */
		tlist = FetchStatementTargetList(PortalListGetPrimaryStmt(cplan->stmt_list));

		SendRowDescriptionMessage(psrc->resultDesc, tlist, NULL);

		ReleaseCachedPlan(cplan, true);
	}
	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 */
		/* NB: this mustn't be enabled until we are within an xact */
		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 */
		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.
 */

/* Test a bare parsetree */
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;
}

/* Test a list that might contain Query nodes or bare parsetrees */
static bool
IsTransactionExitStmtList(List *parseTrees)
{
	if (list_length(parseTrees) == 1)
	{
		Node	   *stmt = (Node *) linitial(parseTrees);

		if (IsA(stmt, Query))
		{
			Query	   *query = (Query *) stmt;

			if (query->commandType == CMD_UTILITY &&
				IsTransactionExitStmt(query->utilityStmt))
				return true;
		}
		else if (IsTransactionExitStmt(stmt))
			return true;
	}
	return false;
}

/* Test a list that might contain Query nodes or bare parsetrees */
static bool
IsTransactionStmtList(List *parseTrees)
{
	if (list_length(parseTrees) == 1)
	{
		Node	   *stmt = (Node *) linitial(parseTrees);

		if (IsA(stmt, Query))
		{
			Query	   *query = (Query *) stmt;

			if (query->commandType == CMD_UTILITY &&
				IsA(query->utilityStmt, TransactionStmt))
				return true;
		}
		else if (IsA(stmt, TransactionStmt))
			return true;
	}
	return false;
}

/* Release any existing unnamed prepared statement */
static void
drop_unnamed_stmt(void)
{
	/* Release any completed unnamed statement */
	if (unnamed_stmt_psrc)
		DropCachedPlan(unnamed_stmt_psrc);
	unnamed_stmt_psrc = NULL;

	/*
	 * If we failed while trying to build a prior unnamed statement, we may
	 * have a memory context that wasn't assigned to a completed plancache
	 * entry.  If so, drop it to avoid a permanent memory leak.
	 */
	if (unnamed_stmt_context)
		MemoryContextDelete(unnamed_stmt_context);
	unnamed_stmt_context = NULL;
}


/* --------------------------------
 *		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(2) 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(2);
}

/*
 * 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++;
			LockWaitCancel();	/* prevent CheckDeadLock from running */
			DisableNotifyInterrupt();
			DisableCatchupInterrupt();
			InterruptHoldoffCount--;
			ProcessInterrupts();
		}
	}

	errno = save_errno;
}

/*
 * Timeout or shutdown signal from postmaster during client authentication.
 * Simply exit(1).
 *
 * 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(1);
}

/*
 * 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 && !DoingCommandRead)
		{
			/* bump holdoff count to make ProcessInterrupts() a no-op */
			/* until we are done getting ready for it */
			InterruptHoldoffCount++;
			LockWaitCancel();	/* prevent CheckDeadLock from running */
			DisableNotifyInterrupt();
			DisableCatchupInterrupt();
			InterruptHoldoffCount--;
			ProcessInterrupts();
		}
	}

	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();
		if (IsAutoVacuumWorkerProcess())
			ereport(FATAL,
					(errcode(ERRCODE_ADMIN_SHUTDOWN),
					 errmsg("terminating autovacuum process due to administrator command")));
		else
			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 if (IsAutoVacuumWorkerProcess())
			ereport(ERROR,
					(errcode(ERRCODE_QUERY_CANCELED),
					 errmsg("canceling autovacuum task")));
		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.
 */
void
check_stack_depth(void)
{
	char		stack_top_loc;
	long		stack_depth;

	/*
	 * Compute distance from PostgresMain's local variables to my own
	 */
	stack_depth = (long) (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\", "
		   "after ensuring the platform's stack depth limit is adequate.")));
	}
}

/* GUC assign hook for max_stack_depth */
bool
assign_max_stack_depth(int newval, bool doit, GucSource source)
{
	long		newval_bytes = newval * 1024L;
	long		stack_rlimit = get_stack_depth_rlimit();

	if (stack_rlimit > 0 && newval_bytes > stack_rlimit - STACK_DEPTH_SLOP)
	{
		ereport(GUC_complaint_elevel(source),
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("\"max_stack_depth\" must not exceed %ldkB",
						(stack_rlimit - STACK_DEPTH_SLOP) / 1024L),
				 errhint("Increase the platform's stack depth limit via \"ulimit -s\" or local equivalent.")));
		return false;
	}
	if (doit)
		max_stack_depth_bytes = newval_bytes;
	return true;
}


/*
 * 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);
}


bool
set_plan_disabling_options(const char *arg, GucContext context, GucSource source)
{
	char	   *tmp = NULL;

	switch (arg[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;
	}
	if (tmp)
	{
		SetConfigOption(tmp, "false", context, source);
		return true;
	}
	else
		return false;
}


const char *
get_stats_option_name(const char *arg)
{
	switch (arg[0])
	{
		case 'p':
			if (optarg[1] == 'a')		/* "parser" */
				return "log_parser_stats";
			else if (optarg[1] == 'l')	/* "planner" */
				return "log_planner_stats";
			break;

		case 'e':				/* "executor" */
			return "log_executor_stats";
			break;
	}

	return NULL;
}


/* ----------------------------------------------------------------
 * 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;
	int			firstchar;
	char		stack_base;
	StringInfoData input_message;
	sigjmp_buf	local_sigjmp_buf;
	volatile bool send_ready_for_query = true;

#define PendingConfigOption(name,val) \
	(guc_names = lappend(guc_names, pstrdup(name)), \
	 guc_values = lappend(guc_values, pstrdup(val)))

	/*
	 * initialize globals (already done if under postmaster, but not if
	 * standalone; cheap enough to do over)
	 */
	MyProcPid = getpid();

	MyStartTime = time(NULL);

	/*
	 * 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", false);

	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.
	 * ----------------
	 */

	/* Ignore the initial --single argument, if present */
	if (argc > 1 && strcmp(argv[1], "--single") == 0)
	{
		argv++;
		argc--;
	}

	/* all options are allowed until '-p' */
	secure = true;
	ctx = PGC_POSTMASTER;
	gucsource = PGC_S_ARGV;		/* initial switches came from command line */

	/*
	 * Parse command-line options.	CAUTION: keep this in sync with
	 * postmaster/postmaster.c (the option sets should not conflict) and with
	 * the common help() function in main/main.c.
	 */
	while ((flag = getopt(argc, argv, "A:B:c:D:d:EeFf:h:ijk:lN:nOo:Pp:r:S:sTt:v:W:y:-:")) != -1)
	{
		switch (flag)
		{
			case 'A':
				SetConfigOption("debug_assertions", optarg, ctx, gucsource);
				break;

			case 'B':
				SetConfigOption("shared_buffers", optarg, ctx, gucsource);
				break;

			case 'D':
				if (secure)
					userDoption = optarg;
				break;

			case 'd':
				debug_flag = atoi(optarg);
				break;

			case 'E':
				EchoQuery = true;
				break;

			case 'e':
				SetConfigOption("datestyle", "euro", ctx, gucsource);
				break;

			case 'F':
				SetConfigOption("fsync", "false", ctx, gucsource);
				break;

			case 'f':
				if (!set_plan_disabling_options(optarg, ctx, gucsource))
					errs++;
				break;

			case 'h':
				SetConfigOption("listen_addresses", optarg, ctx, gucsource);
				break;

			case 'i':
				SetConfigOption("listen_addresses", "*", ctx, gucsource);
				break;

			case 'j':
				UseNewLine = 0;
				break;

			case 'k':
				SetConfigOption("unix_socket_directory", optarg, ctx, gucsource);
				break;

			case 'l':
				SetConfigOption("ssl", "true", ctx, gucsource);
				break;

			case 'N':
				SetConfigOption("max_connections", optarg, ctx, gucsource);
				break;

			case 'n':
				/* ignored for consistency with postmaster */
				break;

			case 'O':
				SetConfigOption("allow_system_table_mods", "true", ctx, gucsource);
				break;

			case 'o':
				errs++;
				break;

			case 'P':
				SetConfigOption("ignore_system_indexes", "true", ctx, gucsource);
				break;

			case 'p':
				SetConfigOption("port", optarg, ctx, gucsource);
				break;

			case 'r':
				/* send output (stdout and stderr) to the given file */
				if (secure)
					strlcpy(OutputFileName, optarg, MAXPGPATH);
				break;

			case 'S':
				SetConfigOption("work_mem", optarg, ctx, gucsource);
				break;

			case 's':

				/*
				 * 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':
				/* ignored for consistency with postmaster */
				break;

			case 't':
				{
					const char *tmp = get_stats_option_name(optarg);

					if (tmp)
					{
						if (ctx == PGC_BACKEND)
							PendingConfigOption(tmp, "true");
						else
							SetConfigOption(tmp, "true", ctx, gucsource);
					}
					else
						errs++;
					break;
				}

			case 'v':
				if (secure)
					FrontendProtocol = (ProtocolVersion) atoi(optarg);
				break;

			case 'W':
				SetConfigOption("post_auth_delay", optarg, ctx, gucsource);
				break;


			case 'y':

				/*
				 * y - 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 '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();
		/* If timezone_abbreviations is not set, select default */
		pg_timezone_abbrev_initialize();
	}

	if (PostAuthDelay)
		pg_usleep(PostAuthDelay * 1000000L);

	/*
	 * You might expect to see a setsid() call here, but it's not needed,
	 * because if we are under a postmaster then BackendInitialize() did it.
	 */

	/*
	 * 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 */

	/*
	 * In a standalone backend, SIGQUIT can be generated from the keyboard
	 * easily, while SIGTERM cannot, so we make both signals do die() rather
	 * than quickdie().
	 */
	if (IsUnderPostmaster)
		pqsignal(SIGQUIT, quickdie);	/* hard crash time */
	else
		pqsignal(SIGQUIT, die); /* cancel current query and exit */
	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();

	if (IsUnderPostmaster)
	{
		/* 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);
	}

	/*
	 * Create a per-backend PGPROC struct in shared memory, except in the
	 * EXEC_BACKEND case where this was done in SubPostmasterMain. We must do
	 * this before we can use LWLocks (and in the EXEC_BACKEND case we already
	 * had to do some stuff with LWLocks).
	 */
#ifdef EXEC_BACKEND
	if (!IsUnderPostmaster)
		InitProcess();
#else
	InitProcess();
#endif

	/*
	 * 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, InvalidOid, username, NULL);

	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);

	/*
	 * process any libraries that should be preloaded at backend start (this
	 * likewise can't be done until GUC settings are complete)
	 */
	process_local_preload_libraries();

	/*
	 * 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();

		/*
		 * 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_ready_for_query = 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_ready_for_query)
		{
			if (IsTransactionOrTransactionBlock())
			{
				set_ps_display("idle in transaction", false);
				pgstat_report_activity("<IDLE> in transaction");
			}
			else
			{
				pgstat_report_tabstat(false);

				set_ps_display("idle", false);
				pgstat_report_activity("<IDLE>");
			}

			ReadyForQuery(whereToSendOutput);
			send_ready_for_query = 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;

					/* Set statement_timestamp() */
					SetCurrentStatementStartTimestamp();

					query_string = pq_getmsgstring(&input_message);
					pq_getmsgend(&input_message);

					exec_simple_query(query_string);

					send_ready_for_query = true;
				}
				break;

			case 'P':			/* parse */
				{
					const char *stmt_name;
					const char *query_string;
					int			numParams;
					Oid		   *paramTypes = NULL;

					/* Set statement_timestamp() */
					SetCurrentStatementStartTimestamp();

					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 */
				/* Set statement_timestamp() */
				SetCurrentStatementStartTimestamp();

				/*
				 * 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;

					/* Set statement_timestamp() */
					SetCurrentStatementStartTimestamp();

					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 */
				/* Set statement_timestamp() */
				SetCurrentStatementStartTimestamp();

				/* Tell the collector what we're doing */
				pgstat_report_activity("<FASTPATH> function call");

				/* start an xact for this function invocation */
				start_xact_command();

				/*
				 * Note: we may at this point be inside an aborted
				 * transaction.  We can't throw error for that until we've
				 * finished reading the function-call message, so
				 * HandleFunctionRequest() must check for it after doing so.
				 * Be careful not to do anything that assumes we're inside a
				 * valid transaction here.
				 */

				/* switch back to message context */
				MemoryContextSwitchTo(MessageContext);

				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_ready_for_query = 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 */
								drop_unnamed_stmt();
							}
							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;

					/* Set statement_timestamp() (needed for xact) */
					SetCurrentStatementStartTimestamp();

					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_ready_for_query = 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 */
}


/*
 * Obtain platform stack depth limit (in bytes)
 *
 * Return -1 if unlimited or not known
 */
long
get_stack_depth_rlimit(void)
{
#if defined(HAVE_GETRLIMIT) && defined(RLIMIT_STACK)
	static long val = 0;

	/* This won't change after process launch, so check just once */
	if (val == 0)
	{
		struct rlimit rlim;

		if (getrlimit(RLIMIT_STACK, &rlim) < 0)
			val = -1;
		else if (rlim.rlim_cur == RLIM_INFINITY)
			val = -1;
		else
			val = rlim.rlim_cur;
	}
	return val;
#else							/* no getrlimit */
#if defined(WIN32) || defined(__CYGWIN__)
	/* On Windows we set the backend stack size in src/backend/Makefile */
	return WIN32_STACK_RLIMIT;
#else							/* not windows ... give up */
	return -1;
#endif
#endif
}


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);
#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;
	long		secs;
	int			usecs;
	int			msecs;
	int			hours,
				minutes,
				seconds;

	TimestampDifference(port->SessionStartTime,
						GetCurrentTimestamp(),
						&secs, &usecs);
	msecs = usecs / 1000;

	hours = secs / SECS_PER_HOUR;
	secs %= SECS_PER_HOUR;
	minutes = secs / SECS_PER_MINUTE;
	seconds = secs % SECS_PER_MINUTE;

	ereport(LOG,
			(errmsg("disconnection: session time: %d:%02d:%02d.%03d "
					"user=%s database=%s host=%s%s%s",
					hours, minutes, seconds, msecs,
					port->user_name, port->database_name, port->remote_host,
				  port->remote_port[0] ? " port=" : "", port->remote_port)));
}