Force a checkpoint in CREATE DATABASE before starting to copy the files,

[PostgreSQL.git] / src / backend / tcop / 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
 *        $PostgreSQL$
 *
 * 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 "pgstat.h"
#include "pg_trace.h"
#include "parser/analyze.h"
#include "parser/parser.h"
#include "postmaster/autovacuum.h"
#include "rewrite/rewriteHandler.h"
#include "storage/bufmgr.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"


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;

        TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);

        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

        TRACE_POSTGRESQL_QUERY_PARSE_DONE(query_string);

        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;

        TRACE_POSTGRESQL_QUERY_REWRITE_START(query_string);

        /*
         * (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);

        TRACE_POSTGRESQL_QUERY_REWRITE_DONE(query_string);

        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 (Debug_print_parse)
                elog_node_display(LOG, "parse tree", query,
                                                  Debug_pretty_print);

        if (log_parser_stats)
                ResetUsage();

        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(LOG, "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;

        TRACE_POSTGRESQL_QUERY_PLAN_START();

        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(LOG, "plan", plan, Debug_pretty_print);

        TRACE_POSTGRESQL_QUERY_PLAN_DONE();

        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);

        TRACE_POSTGRESQL_QUERY_START(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");

        TRACE_POSTGRESQL_QUERY_DONE(query_string);

        debug_query_string = NULL;
}

/*
 * exec_parse_message
 *
 * Execute a "Parse" protocol message.
 */
static void
exec_parse_message(const char *query_string,    /* string to execute */
                                   const char *stmt_name,               /* name for prepared stmt */
                                   Oid *paramTypes,             /* parameter types */
                                   int numParams)               /* number of parameters */
{
        MemoryContext oldcontext;
        List       *parsetree_list;
        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;

        pgstat_report_activity(psrc->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 into the portal */
        query_string = pstrdup(psrc->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),
                                         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 = pstrdup(portal->sourceText);
                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;

        pgstat_report_activity(sourceText);

        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",
                                                execute_is_fetch ?
                                                _("execute fetch from") :
                                                _("execute"),
                                                prepStmtName,
                                                *portal_name ? "/" : "",
                                                *portal_name ? portal_name : "",
                                                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",
                                                        msec_str,
                                                        execute_is_fetch ?
                                                        _("execute fetch from") :
                                                        _("execute"),
                                                        prepStmtName,
                                                        *portal_name ? "/" : "",
                                                        *portal_name ? portal_name : "",
                                                        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)
                        {
                                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);

                /*
                 * 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_stat(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)));
}