postgres.c

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/*-------------------------------------------------------------------------
 *
 * postgres.c
 *    POSTGRES C Backend Interface
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/tcop/postgres.c
 *
 * NOTES
 *    this is the "main" module of the postgres backend and
 *    hence the main module of the "traffic cop".
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <fcntl.h>
#include <limits.h>
#include <signal.h>
#include <unistd.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

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

#include "access/parallel.h"
#include "access/printtup.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "commands/async.h"
#include "commands/prepare.h"
#include "executor/spi.h"
#include "jit/jit.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "libpq/pqsignal.h"
#include "mb/pg_wchar.h"
#include "mb/stringinfo_mb.h"
#include "miscadmin.h"
#include "nodes/print.h"
#include "optimizer/optimizer.h"
#include "parser/analyze.h"
#include "parser/parser.h"
#include "pg_getopt.h"
#include "pg_trace.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "postmaster/interrupt.h"
#include "postmaster/postmaster.h"
#include "replication/logicallauncher.h"
#include "replication/logicalworker.h"
#include "replication/slot.h"
#include "replication/walsender.h"
#include "rewrite/rewriteHandler.h"
#include "storage/bufmgr.h"
#include "storage/ipc.h"
#include "storage/pmsignal.h"
#include "storage/proc.h"
#include "storage/procsignal.h"
#include "storage/sinval.h"
#include "tcop/fastpath.h"
#include "tcop/pquery.h"
#include "tcop/tcopprot.h"
#include "tcop/utility.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"
#include "utils/snapmgr.h"
#include "utils/timeout.h"
#include "utils/timestamp.h"

/* ----------------
 *      global variables
 * ----------------
 */
const char *debug_query_string; /* client-supplied query string */

/* 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 PostmasterMain and inherited by
 * subprocesses. This is not static because old versions of PL/Java modify
 * it directly. Newer versions use set_stack_base(), but we want to stay
 * binary-compatible for the time being.
 */
char       *stack_base_ptr = NULL;

/*
 * On IA64 we also have to remember the register stack base.
 */
#if defined(__ia64__) || defined(__ia64)
char       *register_stack_base_ptr = NULL;
#endif

/*
 * 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;

/* assorted command-line switches */
static const char *userDoption = NULL;  /* -D switch */
static bool EchoQuery = false;  /* -E switch */
static bool UseSemiNewlineNewline = false;  /* -j switch */

/* whether or not, and why, we were canceled by conflict with recovery */
static bool RecoveryConflictPending = false;
static bool RecoveryConflictRetryable = true;
static ProcSignalReason RecoveryConflictReason;

/* reused buffer to pass to SendRowDescriptionMessage() */
static MemoryContext row_description_context = NULL;
static StringInfoData row_description_buf;

/* ----------------------------------------------------------------
 *      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 void forbidden_in_wal_sender(char firstchar);
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 int  errdetail_abort(void);
static int  errdetail_recovery_conflict(void);
static void start_xact_command(void);
static void finish_xact_command(void);
static bool IsTransactionExitStmt(Node *parsetree);
static bool IsTransactionExitStmtList(List *pstmts);
static bool IsTransactionStmtList(List *pstmts);
static void drop_unnamed_stmt(void);
static void log_disconnections(int code, Datum arg);
static void enable_statement_timeout(void);
static void disable_statement_timeout(void);


/* ----------------------------------------------------------------
 *      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() */

    /*
     * display a prompt and obtain input from the user
     */
    printf("backend> ");
    fflush(stdout);

    resetStringInfo(inBuf);

    /*
     * Read characters until EOF or the appropriate delimiter is seen.
     */
    while ((c = interactive_getc()) != EOF)
    {
        if (c == '\n')
        {
            if (UseSemiNewlineNewline)
            {
                /*
                 * In -j mode, semicolon followed by two newlines ends the
                 * command; otherwise treat newline as regular character.
                 */
                if (inBuf->len > 1 &&
                    inBuf->data[inBuf->len - 1] == '\n' &&
                    inBuf->data[inBuf->len - 2] == ';')
                {
                    /* might as well drop the second newline */
                    break;
                }
            }
            else
            {
                /*
                 * In plain mode, newline ends the command unless preceded by
                 * backslash.
                 */
                if (inBuf->len > 0 &&
                    inBuf->data[inBuf->len - 1] == '\\')
                {
                    /* discard backslash from inBuf */
                    inBuf->data[--inBuf->len] = '\0';
                    /* discard newline too */
                    continue;
                }
                else
                {
                    /* keep the newline character, but end the command */
                    appendStringInfoChar(inBuf, '\n');
                    break;
                }
            }
        }

        /* Not newline, or newline treated as regular character */
        appendStringInfoChar(inBuf, (char) c);
    }

    /* No input before EOF signal means time to quit. */
    if (c == EOF && inBuf->len == 0)
        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.
 */
static int
interactive_getc(void)
{
    int         c;

    /*
     * This will not process catchup interrupts or notifications while
     * reading. But those can't really be relevant for a standalone backend
     * anyway. To properly handle SIGTERM there's a hack in die() that
     * directly processes interrupts at this stage...
     */
    CHECK_FOR_INTERRUPTS();

    c = getc(stdin);

    ProcessClientReadInterrupt(false);

    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.
     */
    HOLD_CANCEL_INTERRUPTS();
    pq_startmsgread();
    qtype = pq_getbyte();

    if (qtype == EOF)           /* frontend disconnected */
    {
        if (IsTransactionState())
            ereport(COMMERROR,
                    (errcode(ERRCODE_CONNECTION_FAILURE),
                     errmsg("unexpected EOF on client connection with an open transaction")));
        else
        {
            /*
             * Can't send DEBUG log messages to client at this point. Since
             * we're disconnecting right away, we don't need to restore
             * whereToSendOutput.
             */
            whereToSendOutput = DestNone;
            ereport(DEBUG1,
                    (errcode(ERRCODE_CONNECTION_DOES_NOT_EXIST),
                     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))
                {
                    if (IsTransactionState())
                        ereport(COMMERROR,
                                (errcode(ERRCODE_CONNECTION_FAILURE),
                                 errmsg("unexpected EOF on client connection with an open transaction")));
                    else
                    {
                        /*
                         * Can't send DEBUG log messages to client at this
                         * point. Since we're disconnecting right away, we
                         * don't need to restore whereToSendOutput.
                         */
                        whereToSendOutput = DestNone;
                        ereport(DEBUG1,
                                (errcode(ERRCODE_CONNECTION_DOES_NOT_EXIST),
                                 errmsg("unexpected EOF on client connection")));
                    }
                    return EOF;
                }
            }
            break;

        case 'F':               /* fastpath function call */
            doing_extended_query_message = false;
            if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
            {
                if (GetOldFunctionMessage(inBuf))
                {
                    if (IsTransactionState())
                        ereport(COMMERROR,
                                (errcode(ERRCODE_CONNECTION_FAILURE),
                                 errmsg("unexpected EOF on client connection with an open transaction")));
                    else
                    {
                        /*
                         * Can't send DEBUG log messages to client at this
                         * point. Since we're disconnecting right away, we
                         * don't need to restore whereToSendOutput.
                         */
                        whereToSendOutput = DestNone;
                        ereport(DEBUG1,
                                (errcode(ERRCODE_CONNECTION_DOES_NOT_EXIST),
                                 errmsg("unexpected EOF on client connection")));
                    }
                    return EOF;
                }
            }
            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 */
    }
    else
        pq_endmsgread();
    RESUME_CANCEL_INTERRUPTS();

    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;
}

/*
 * ProcessClientReadInterrupt() - Process interrupts specific to client reads
 *
 * This is called just before and after low-level reads.
 * 'blocked' is true if no data was available to read and we plan to retry,
 * false if about to read or done reading.
 *
 * Must preserve errno!
 */
void
ProcessClientReadInterrupt(bool blocked)
{
    int         save_errno = errno;

    if (DoingCommandRead)
    {
        /* Check for general interrupts that arrived before/while reading */
        CHECK_FOR_INTERRUPTS();

        /* Process sinval catchup interrupts, if any */
        if (catchupInterruptPending)
            ProcessCatchupInterrupt();

        /* Process notify interrupts, if any */
        if (notifyInterruptPending)
            ProcessNotifyInterrupt();
    }
    else if (ProcDiePending)
    {
        /*
         * We're dying.  If there is no data available to read, then it's safe
         * (and sane) to handle that now.  If we haven't tried to read yet,
         * make sure the process latch is set, so that if there is no data
         * then we'll come back here and die.  If we're done reading, also
         * make sure the process latch is set, as we might've undesirably
         * cleared it while reading.
         */
        if (blocked)
            CHECK_FOR_INTERRUPTS();
        else
            SetLatch(MyLatch);
    }

    errno = save_errno;
}

/*
 * ProcessClientWriteInterrupt() - Process interrupts specific to client writes
 *
 * This is called just before and after low-level writes.
 * 'blocked' is true if no data could be written and we plan to retry,
 * false if about to write or done writing.
 *
 * Must preserve errno!
 */
void
ProcessClientWriteInterrupt(bool blocked)
{
    int         save_errno = errno;

    if (ProcDiePending)
    {
        /*
         * We're dying.  If it's not possible to write, then we should handle
         * that immediately, else a stuck client could indefinitely delay our
         * response to the signal.  If we haven't tried to write yet, make
         * sure the process latch is set, so that if the write would block
         * then we'll come back here and die.  If we're done writing, also
         * make sure the process latch is set, as we might've undesirably
         * cleared it while writing.
         */
        if (blocked)
        {
            /*
             * Don't mess with whereToSendOutput if ProcessInterrupts wouldn't
             * do anything.
             */
            if (InterruptHoldoffCount == 0 && CritSectionCount == 0)
            {
                /*
                 * We don't want to send the client the error message, as a)
                 * that would possibly block again, and b) it would likely
                 * lead to loss of protocol sync because we may have already
                 * sent a partial protocol message.
                 */
                if (whereToSendOutput == DestRemote)
                    whereToSendOutput = DestNone;

                CHECK_FOR_INTERRUPTS();
            }
        }
        else
            SetLatch(MyLatch);
    }

    errno = save_errno;
}

/*
 * Do raw parsing (only).
 *
 * A list of parsetrees (RawStmt nodes) 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, RAW_PARSE_DEFAULT);

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

#ifdef COPY_PARSE_PLAN_TREES
    /* Optional debugging check: pass raw parsetrees through copyObject() */
    {
        List       *new_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

    /*
     * Currently, outfuncs/readfuncs support is missing for many raw parse
     * tree nodes, so we don't try to implement WRITE_READ_PARSE_PLAN_TREES
     * here.
     */

    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(RawStmt *parsetree, const char *query_string,
                       Oid *paramTypes, int numParams,
                       QueryEnvironment *queryEnv)
{
    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,
                          queryEnv);

    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;
}

/*
 * Do parse analysis and rewriting.  This is the same as pg_analyze_and_rewrite
 * except that external-parameter resolution is determined by parser callback
 * hooks instead of a fixed list of parameter datatypes.
 */
List *
pg_analyze_and_rewrite_params(RawStmt *parsetree,
                              const char *query_string,
                              ParserSetupHook parserSetup,
                              void *parserSetupArg,
                              QueryEnvironment *queryEnv)
{
    ParseState *pstate;
    Query      *query;
    List       *querytree_list;

    Assert(query_string != NULL);   /* required as of 8.4 */

    TRACE_POSTGRESQL_QUERY_REWRITE_START(query_string);

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

    pstate = make_parsestate(NULL);
    pstate->p_sourcetext = query_string;
    pstate->p_queryEnv = queryEnv;
    (*parserSetup) (pstate, parserSetupArg);

    query = transformTopLevelStmt(pstate, parsetree);

    if (post_parse_analyze_hook)
        (*post_parse_analyze_hook) (pstate, query);

    free_parsestate(pstate);

    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 through copyObject() */
    {
        List       *new_list;

        new_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

#ifdef WRITE_READ_PARSE_PLAN_TREES
    /* Optional debugging check: pass querytree through outfuncs/readfuncs */
    {
        List       *new_list = NIL;
        ListCell   *lc;

        /*
         * We currently lack outfuncs/readfuncs support for most utility
         * statement types, so only attempt to write/read non-utility queries.
         */
        foreach(lc, querytree_list)
        {
            Query      *query = castNode(Query, lfirst(lc));

            if (query->commandType != CMD_UTILITY)
            {
                char       *str = nodeToString(query);
                Query      *new_query = stringToNodeWithLocations(str);

                /*
                 * queryId is not saved in stored rules, but we must preserve
                 * it here to avoid breaking pg_stat_statements.
                 */
                new_query->queryId = query->queryId;

                new_list = lappend(new_list, new_query);
                pfree(str);
            }
            else
                new_list = lappend(new_list, query);
        }

        /* This checks both outfuncs/readfuncs and the equal() routines... */
        if (!equal(new_list, querytree_list))
            elog(WARNING, "outfuncs/readfuncs 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, const char *query_string, int cursorOptions,
              ParamListInfo boundParams)
{
    PlannedStmt *plan;

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

    /* Planner must have a snapshot in case it calls user-defined functions. */
    Assert(ActiveSnapshotSet());

    TRACE_POSTGRESQL_QUERY_PLAN_START();

    if (log_planner_stats)
        ResetUsage();

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

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

#ifdef COPY_PARSE_PLAN_TREES
    /* Optional debugging check: pass plan tree through copyObject() */
    {
        PlannedStmt *new_plan = copyObject(plan);

        /*
         * equal() currently does not have routines to compare Plan nodes, so
         * don't try to test equality here.  Perhaps fix someday?
         */
#ifdef NOT_USED
        /* This checks both copyObject() and the equal() routines... */
        if (!equal(new_plan, plan))
            elog(WARNING, "copyObject() failed to produce an equal plan tree");
        else
#endif
            plan = new_plan;
    }
#endif

#ifdef WRITE_READ_PARSE_PLAN_TREES
    /* Optional debugging check: pass plan tree through outfuncs/readfuncs */
    {
        char       *str;
        PlannedStmt *new_plan;

        str = nodeToString(plan);
        new_plan = stringToNodeWithLocations(str);
        pfree(str);

        /*
         * 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 outfuncs/readfuncs and the equal() routines... */
        if (!equal(new_plan, plan))
            elog(WARNING, "outfuncs/readfuncs 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.
 *
 * For normal optimizable statements, invoke the planner.  For utility
 * statements, just make a wrapper PlannedStmt node.
 *
 * The result is a list of PlannedStmt nodes.
 */
List *
pg_plan_queries(List *querytrees, const char *query_string, int cursorOptions,
                ParamListInfo boundParams)
{
    List       *stmt_list = NIL;
    ListCell   *query_list;

    foreach(query_list, querytrees)
    {
        Query      *query = lfirst_node(Query, query_list);
        PlannedStmt *stmt;

        if (query->commandType == CMD_UTILITY)
        {
            /* Utility commands require no planning. */
            stmt = makeNode(PlannedStmt);
            stmt->commandType = CMD_UTILITY;
            stmt->canSetTag = query->canSetTag;
            stmt->utilityStmt = query->utilityStmt;
            stmt->stmt_location = query->stmt_location;
            stmt->stmt_len = query->stmt_len;
        }
        else
        {
            stmt = pg_plan_query(query, query_string, cursorOptions,
                                 boundParams);
        }

        stmt_list = lappend(stmt_list, stmt);
    }

    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        use_implicit_block;
    char        msec_str[32];

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

    pgstat_report_activity(STATE_RUNNING, 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);

    /*
     * For historical reasons, if multiple SQL statements are given in a
     * single "simple Query" message, we execute them as a single transaction,
     * unless explicit transaction control commands are included to make
     * portions of the list be separate transactions.  To represent this
     * behavior properly in the transaction machinery, we use an "implicit"
     * transaction block.
     */
    use_implicit_block = (list_length(parsetree_list) > 1);

    /*
     * Run through the raw parsetree(s) and process each one.
     */
    foreach(parsetree_item, parsetree_list)
    {
        RawStmt    *parsetree = lfirst_node(RawStmt, parsetree_item);
        bool        snapshot_set = false;
        CommandTag  commandTag;
        QueryCompletion qc;
        MemoryContext per_parsetree_context = NULL;
        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->stmt);

        set_ps_display(GetCommandTagName(commandTag));

        BeginCommand(commandTag, dest);

        /*
         * If we are in an aborted transaction, reject all commands except
         * COMMIT/ABORT.  It is important that this test occur before we try
         * to do parse analysis, rewrite, or planning, since all those phases
         * try to do database accesses, which may fail in abort state. (It
         * might be safe to allow some additional utility commands in this
         * state, but not many...)
         */
        if (IsAbortedTransactionBlockState() &&
            !IsTransactionExitStmt(parsetree->stmt))
            ereport(ERROR,
                    (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                     errmsg("current transaction is aborted, "
                            "commands ignored until end of transaction block"),
                     errdetail_abort()));

        /* Make sure we are in a transaction command */
        start_xact_command();

        /*
         * If using an implicit transaction block, and we're not already in a
         * transaction block, start an implicit block to force this statement
         * to be grouped together with any following ones.  (We must do this
         * each time through the loop; otherwise, a COMMIT/ROLLBACK in the
         * list would cause later statements to not be grouped.)
         */
        if (use_implicit_block)
            BeginImplicitTransactionBlock();

        /* If we got a cancel signal in parsing or prior command, quit */
        CHECK_FOR_INTERRUPTS();

        /*
         * Set up a snapshot if parse analysis/planning will need one.
         */
        if (analyze_requires_snapshot(parsetree))
        {
            PushActiveSnapshot(GetTransactionSnapshot());
            snapshot_set = true;
        }

        /*
         * OK to analyze, rewrite, and plan this query.
         *
         * Switch to appropriate context for constructing query and plan trees
         * (these can't be in the transaction context, as that will get reset
         * when the command is COMMIT/ROLLBACK).  If we have multiple
         * parsetrees, we use a separate context for each one, so that we can
         * free that memory before moving on to the next one.  But for the
         * last (or only) parsetree, just use MessageContext, which will be
         * reset shortly after completion anyway.  In event of an error, the
         * per_parsetree_context will be deleted when MessageContext is reset.
         */
        if (lnext(parsetree_list, parsetree_item) != NULL)
        {
            per_parsetree_context =
                AllocSetContextCreate(MessageContext,
                                      "per-parsetree message context",
                                      ALLOCSET_DEFAULT_SIZES);
            oldcontext = MemoryContextSwitchTo(per_parsetree_context);
        }
        else
            oldcontext = MemoryContextSwitchTo(MessageContext);

        querytree_list = pg_analyze_and_rewrite(parsetree, query_string,
                                                NULL, 0, NULL);

        plantree_list = pg_plan_queries(querytree_list, query_string,
                                        CURSOR_OPT_PARALLEL_OK, NULL);

        /*
         * Done with the snapshot used for parsing/planning.
         *
         * While it looks promising to reuse the same snapshot for query
         * execution (at least for simple protocol), unfortunately it causes
         * execution to use a snapshot that has been acquired before locking
         * any of the tables mentioned in the query.  This creates user-
         * visible anomalies, so refrain.  Refer to
         * https://postgr.es/m/flat/5075D8DF.6050500@fuzzy.cz for details.
         */
        if (snapshot_set)
            PopActiveSnapshot();

        /* 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 passing here is in MessageContext or the
         * per_parsetree_context, and so will outlive the portal anyway.
         */
        PortalDefineQuery(portal,
                          NULL,
                          query_string,
                          commandTag,
                          plantree_list,
                          NULL);

        /*
         * Start the portal.  No parameters here.
         */
        PortalStart(portal, NULL, 0, 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->stmt, FetchStmt))
        {
            FetchStmt  *stmt = (FetchStmt *) parsetree->stmt;

            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);
        if (dest == DestRemote)
            SetRemoteDestReceiverParams(receiver, 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,
                         true,  /* always top level */
                         true,
                         receiver,
                         receiver,
                         &qc);

        receiver->rDestroy(receiver);

        PortalDrop(portal, false);

        if (lnext(parsetree_list, 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.  Also, if we're using an
             * implicit transaction block, we must close that out first.
             */
            if (use_implicit_block)
                EndImplicitTransactionBlock();
            finish_xact_command();
        }
        else if (IsA(parsetree->stmt, TransactionStmt))
        {
            /*
             * If this was a transaction control statement, commit it. We will
             * start a new xact command for the next command.
             */
            finish_xact_command();
        }
        else
        {
            /*
             * We need a CommandCounterIncrement after every query, except
             * those that start or end a transaction block.
             */
            CommandCounterIncrement();

            /*
             * Disable statement timeout between queries of a multi-query
             * string, so that the timeout applies separately to each query.
             * (Our next loop iteration will start a fresh timeout.)
             */
            disable_statement_timeout();
        }

        /*
         * 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(&qc, dest, false);

        /* Now we may drop the per-parsetree context, if one was created. */
        if (per_parsetree_context)
            MemoryContextDelete(per_parsetree_context);
    }                           /* end loop over parsetrees */

    /*
     * Close down transaction statement, if one is open.  (This will only do
     * something if the parsetree list was empty; otherwise the last loop
     * iteration already did it.)
     */
    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 unnamed_stmt_context = NULL;
    MemoryContext oldcontext;
    List       *parsetree_list;
    RawStmt    *raw_parse_tree;
    List       *querytree_list;
    CachedPlanSource *psrc;
    bool        is_named;
    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(STATE_RUNNING, query_string);

    set_ps_display("PARSE");

    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.  This also arms the statement timeout if
     * necessary.
     */
    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 rewriting. 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 trees.  So in this case, we create the plancache entry's
     * query_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 */
        unnamed_stmt_context =
            AllocSetContextCreate(MessageContext,
                                  "unnamed prepared statement",
                                  ALLOCSET_DEFAULT_SIZES);
        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;
        bool        snapshot_set = false;

        raw_parse_tree = linitial_node(RawStmt, parsetree_list);

        /*
         * 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->stmt))
            ereport(ERROR,
                    (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                     errmsg("current transaction is aborted, "
                            "commands ignored until end of transaction block"),
                     errdetail_abort()));

        /*
         * Create the CachedPlanSource before we do parse analysis, since it
         * needs to see the unmodified raw parse tree.
         */
        psrc = CreateCachedPlan(raw_parse_tree, query_string,
                                CreateCommandTag(raw_parse_tree->stmt));

        /*
         * Set up a snapshot if parse analysis will need one.
         */
        if (analyze_requires_snapshot(raw_parse_tree))
        {
            PushActiveSnapshot(GetTransactionSnapshot());
            snapshot_set = true;
        }

        /*
         * Analyze and rewrite the query.  Note that the originally specified
         * parameter set is not required to be complete, so we have to use
         * parse_analyze_varparams().
         */
        if (log_parser_stats)
            ResetUsage();

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

        /*
         * Check all parameter types got determined.
         */
        for (int 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);

        /* Done with the snapshot used for parsing */
        if (snapshot_set)
            PopActiveSnapshot();
    }
    else
    {
        /* Empty input string.  This is legal. */
        raw_parse_tree = NULL;
        psrc = CreateCachedPlan(raw_parse_tree, query_string,
                                CMDTAG_UNKNOWN);
        querytree_list = NIL;
    }

    /*
     * CachedPlanSource must be a direct child of MessageContext before we
     * reparent unnamed_stmt_context under it, else we have a disconnected
     * circular subgraph.  Klugy, but less so than flipping contexts even more
     * above.
     */
    if (unnamed_stmt_context)
        MemoryContextSetParent(psrc->context, MessageContext);

    /* Finish filling in the CachedPlanSource */
    CompleteCachedPlan(psrc,
                       querytree_list,
                       unnamed_stmt_context,
                       paramTypes,
                       numParams,
                       NULL,
                       NULL,
                       CURSOR_OPT_PARALLEL_OK,  /* allow parallel mode */
                       true);   /* fixed result */

    /* If we got a cancel signal during analysis, quit */
    CHECK_FOR_INTERRUPTS();

    if (is_named)
    {
        /*
         * Store the query as a prepared statement.
         */
        StorePreparedStatement(stmt_name, psrc, false);
    }
    else
    {
        /*
         * We just save the CachedPlanSource into unnamed_stmt_psrc.
         */
        SaveCachedPlan(psrc);
        unnamed_stmt_psrc = psrc;
    }

    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;
    MemoryContext oldContext;
    bool        save_log_statement_stats = log_statement_stats;
    bool        snapshot_set = false;
    char        msec_str[32];
    ParamsErrorCbData params_data;
    ErrorContextCallback params_errcxt;

    /* 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(STATE_RUNNING, psrc->query_string);

    set_ps_display("BIND");

    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.  This also arms the statement timeout if
     * necessary.
     */
    start_xact_command();

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

    /* Get the parameter format codes */
    numPFormats = pq_getmsgint(input_message, 2);
    if (numPFormats > 0)
    {
        pformats = (int16 *) palloc(numPFormats * sizeof(int16));
        for (int 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() &&
        (!(psrc->raw_parse_tree &&
           IsTransactionExitStmt(psrc->raw_parse_tree->stmt)) ||
         numParams != 0))
        ereport(ERROR,
                (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                 errmsg("current transaction is aborted, "
                        "commands ignored until end of transaction block"),
                 errdetail_abort()));

    /*
     * 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 GetCachedPlan and
     * PortalDefineQuery; that would result in leaking our plancache refcount.
     */
    oldContext = MemoryContextSwitchTo(portal->portalContext);

    /* 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;

    /*
     * Set a snapshot if we have parameters to fetch (since the input
     * functions might need it) or the query isn't a utility command (and
     * hence could require redoing parse analysis and planning).  We keep the
     * snapshot active till we're done, so that plancache.c doesn't have to
     * take new ones.
     */
    if (numParams > 0 ||
        (psrc->raw_parse_tree &&
         analyze_requires_snapshot(psrc->raw_parse_tree)))
    {
        PushActiveSnapshot(GetTransactionSnapshot());
        snapshot_set = true;
    }

    /*
     * Fetch parameters, if any, and store in the portal's memory context.
     */
    if (numParams > 0)
    {
        char      **knownTextValues = NULL; /* allocate on first use */

        params = makeParamList(numParams);

        for (int 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 = unconstify(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);

                /*
                 * If we might need to log parameters later, save a copy of
                 * the converted string in MessageContext; then free the
                 * result of encoding conversion, if any was done.
                 */
                if (pstring)
                {
                    if (log_parameter_max_length_on_error != 0)
                    {
                        MemoryContext oldcxt;

                        oldcxt = MemoryContextSwitchTo(MessageContext);

                        if (knownTextValues == NULL)
                            knownTextValues =
                                palloc0(numParams * sizeof(char *));

                        if (log_parameter_max_length_on_error < 0)
                            knownTextValues[paramno] = pstrdup(pstring);
                        else
                        {
                            /*
                             * We can trim the saved string, knowing that we
                             * won't print all of it.  But we must copy at
                             * least two more full characters than
                             * BuildParamLogString wants to use; otherwise it
                             * might fail to include the trailing ellipsis.
                             */
                            knownTextValues[paramno] =
                                pnstrdup(pstring,
                                         log_parameter_max_length_on_error
                                         + 2 * MAX_MULTIBYTE_CHAR_LEN);
                        }

                        MemoryContextSwitchTo(oldcxt);
                    }
                    if (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 ensures that any custom plan
             * makes full use of the parameter values.
             */
            params->params[paramno].pflags = PARAM_FLAG_CONST;
            params->params[paramno].ptype = ptype;
        }

        /*
         * Once all parameters have been received, prepare for printing them
         * in errors, if configured to do so.  (This is saved in the portal,
         * so that they'll appear when the query is executed later.)
         */
        if (log_parameter_max_length_on_error != 0)
            params->paramValuesStr =
                BuildParamLogString(params,
                                    knownTextValues,
                                    log_parameter_max_length_on_error);
    }
    else
        params = NULL;

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

    /* Set the error callback so that parameters are logged, as needed  */
    params_data.portalName = portal->name;
    params_data.params = params;
    params_errcxt.previous = error_context_stack;
    params_errcxt.callback = ParamsErrorCallback;
    params_errcxt.arg = (void *) &params_data;
    error_context_stack = &params_errcxt;

    /* Get the result format codes */
    numRFormats = pq_getmsgint(input_message, 2);
    if (numRFormats > 0)
    {
        rformats = (int16 *) palloc(numRFormats * sizeof(int16));
        for (int i = 0; i < numRFormats; i++)
            rformats[i] = pq_getmsgint(input_message, 2);
    }

    pq_getmsgend(input_message);

    /*
     * Obtain a plan from the CachedPlanSource.  Any cruft from (re)planning
     * will be generated in MessageContext.  The plan refcount will be
     * assigned to the Portal, so it will be released at portal destruction.
     */
    cplan = GetCachedPlan(psrc, params, false, NULL);

    /*
     * Now we can define the portal.
     *
     * DO NOT put any code that could possibly throw an error between the
     * above GetCachedPlan call and here.
     */
    PortalDefineQuery(portal,
                      saved_stmt_name,
                      query_string,
                      psrc->commandTag,
                      cplan->stmt_list,
                      cplan);

    /* Done with the snapshot used for parameter I/O and parsing/planning */
    if (snapshot_set)
        PopActiveSnapshot();

    /*
     * And we're ready to start portal execution.
     */
    PortalStart(portal, params, 0, InvalidSnapshot);

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

    /*
     * Done binding; remove the parameters error callback.  Entries emitted
     * later determine independently whether to log the parameters or not.
     */
    error_context_stack = error_context_stack->previous;

    /*
     * 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;
    QueryCompletion qc;
    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];
    ParamsErrorCbData params_data;
    ErrorContextCallback params_errcxt;

    /* 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 == CMDTAG_UNKNOWN)
    {
        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(STATE_RUNNING, sourceText);

    set_ps_display(GetCommandTagName(portal->commandTag));

    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);
    if (dest == DestRemoteExecute)
        SetRemoteDestReceiverParams(receiver, 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"),
                 errdetail_abort()));

    /* Check for cancel signal before we start execution */
    CHECK_FOR_INTERRUPTS();

    /*
     * Okay to run the portal.  Set the error callback so that parameters are
     * logged.  The parameters must have been saved during the bind phase.
     */
    params_data.portalName = portal->name;
    params_data.params = portalParams;
    params_errcxt.previous = error_context_stack;
    params_errcxt.callback = ParamsErrorCallback;
    params_errcxt.arg = (void *) &params_data;
    error_context_stack = &params_errcxt;

    if (max_rows <= 0)
        max_rows = FETCH_ALL;

    completed = PortalRun(portal,
                          max_rows,
                          true, /* always top level */
                          !execute_is_fetch && max_rows == FETCH_ALL,
                          receiver,
                          receiver,
                          &qc);

    receiver->rDestroy(receiver);

    /* Done executing; remove the params error callback */
    error_context_stack = error_context_stack->previous;

    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();

            /*
             * Disable statement timeout whenever we complete an Execute
             * message.  The next protocol message will start a fresh timeout.
             */
            disable_statement_timeout();
        }

        /* Send appropriate CommandComplete to client */
        EndCommand(&qc, dest, false);
    }
    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
 *
 * stmt_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
 *      We also check if this statement in this transaction must be logged
 *      (regardless of its duration).
 *
 * 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_sample >= 0 ||
        log_min_duration_statement >= 0 || xact_is_sampled)
    {
        long        secs;
        int         usecs;
        int         msecs;
        bool        exceeded_duration;
        bool        exceeded_sample_duration;
        bool        in_sample = false;

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

        /*
         * This odd-looking test for log_min_duration_* 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_duration = (log_min_duration_statement == 0 ||
                             (log_min_duration_statement > 0 &&
                              (secs > log_min_duration_statement / 1000 ||
                               secs * 1000 + msecs >= log_min_duration_statement)));

        exceeded_sample_duration = (log_min_duration_sample == 0 ||
                                    (log_min_duration_sample > 0 &&
                                     (secs > log_min_duration_sample / 1000 ||
                                      secs * 1000 + msecs >= log_min_duration_sample)));

        /*
         * Do not log if log_statement_sample_rate = 0. Log a sample if
         * log_statement_sample_rate <= 1 and avoid unnecessary random() call
         * if log_statement_sample_rate = 1.
         */
        if (exceeded_sample_duration)
            in_sample = log_statement_sample_rate != 0 &&
                (log_statement_sample_rate == 1 ||
                 random() <= log_statement_sample_rate * MAX_RANDOM_VALUE);

        if (exceeded_duration || in_sample || log_duration || xact_is_sampled)
        {
            snprintf(msec_str, 32, "%ld.%03d",
                     secs * 1000 + msecs, usecs % 1000);
            if ((exceeded_duration || in_sample || xact_is_sampled) && !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)
    {
        RawStmt    *parsetree = lfirst_node(RawStmt, parsetree_item);

        if (IsA(parsetree->stmt, ExecuteStmt))
        {
            ExecuteStmt *stmt = (ExecuteStmt *) parsetree->stmt;
            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.
 * Note that this is only used for statement logging, so it is controlled
 * by log_parameter_max_length not log_parameter_max_length_on_error.
 */
static int
errdetail_params(ParamListInfo params)
{
    if (params && params->numParams > 0 && log_parameter_max_length != 0)
    {
        char       *str;

        str = BuildParamLogString(params, NULL, log_parameter_max_length);
        if (str && str[0] != '\0')
            errdetail("parameters: %s", str);
    }

    return 0;
}

/*
 * errdetail_abort
 *
 * Add an errdetail() line showing abort reason, if any.
 */
static int
errdetail_abort(void)
{
    if (MyProc->recoveryConflictPending)
        errdetail("abort reason: recovery conflict");

    return 0;
}

/*
 * errdetail_recovery_conflict
 *
 * Add an errdetail() line showing conflict source.
 */
static int
errdetail_recovery_conflict(void)
{
    switch (RecoveryConflictReason)
    {
        case PROCSIG_RECOVERY_CONFLICT_BUFFERPIN:
            errdetail("User was holding shared buffer pin for too long.");
            break;
        case PROCSIG_RECOVERY_CONFLICT_LOCK:
            errdetail("User was holding a relation lock for too long.");
            break;
        case PROCSIG_RECOVERY_CONFLICT_TABLESPACE:
            errdetail("User was or might have been using tablespace that must be dropped.");
            break;
        case PROCSIG_RECOVERY_CONFLICT_SNAPSHOT:
            errdetail("User query might have needed to see row versions that must be removed.");
            break;
        case PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK:
            errdetail("User transaction caused buffer deadlock with recovery.");
            break;
        case PROCSIG_RECOVERY_CONFLICT_DATABASE:
            errdetail("User was connected to a database that must be dropped.");
            break;
        default:
            break;
            /* no errdetail */
    }

    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;

    /*
     * 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.
     * 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"),
                 errdetail_abort()));

    if (whereToSendOutput != DestRemote)
        return;                 /* can't actually do anything... */

    /*
     * First describe the parameters...
     */
    pq_beginmessage_reuse(&row_description_buf, 't');   /* parameter description
                                                         * message type */
    pq_sendint16(&row_description_buf, psrc->num_params);

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

        pq_sendint32(&row_description_buf, (int) ptype);
    }
    pq_endmessage_reuse(&row_description_buf);

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

        /* Get the plan's primary targetlist */
        tlist = CachedPlanGetTargetList(psrc, NULL);

        SendRowDescriptionMessage(&row_description_buf,
                                  psrc->resultDesc,
                                  tlist,
                                  NULL);
    }
    else
        pq_putemptymessage('n');    /* NoData */

}

/*
 * exec_describe_portal_message
 *
 * Process a "Describe" message for a portal
 */
static void
exec_describe_portal_message(const char *portal_name)
{
    Portal      portal;

    /*
     * Start up a transaction command. (Note that this will normally change
     * current memory context.) Nothing happens if we are already in one.
     */
    start_xact_command();

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

    portal = GetPortalByName(portal_name);
    if (!PortalIsValid(portal))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_CURSOR),
                 errmsg("portal \"%s\" does not exist", portal_name)));

    /*
     * If we are in aborted transaction state, we can't run
     * SendRowDescriptionMessage(), because that needs catalog accesses.
     * Hence, refuse to Describe portals that return data.  (We shouldn't just
     * refuse all Describes, since that might break the ability of some
     * clients to issue COMMIT or ROLLBACK commands, if they use code that
     * blindly Describes whatever it does.)
     */
    if (IsAbortedTransactionBlockState() &&
        portal->tupDesc)
        ereport(ERROR,
                (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                 errmsg("current transaction is aborted, "
                        "commands ignored until end of transaction block"),
                 errdetail_abort()));

    if (whereToSendOutput != DestRemote)
        return;                 /* can't actually do anything... */

    if (portal->tupDesc)
        SendRowDescriptionMessage(&row_description_buf,
                                  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)
    {
        StartTransactionCommand();

        xact_started = true;
    }

    /*
     * Start statement timeout if necessary.  Note that this'll intentionally
     * not reset the clock on an already started timeout, to avoid the timing
     * overhead when start_xact_command() is invoked repeatedly, without an
     * interceding finish_xact_command() (e.g. parse/bind/execute).  If that's
     * not desired, the timeout has to be disabled explicitly.
     */
    enable_statement_timeout();
}

static void
finish_xact_command(void)
{
    /* cancel active statement timeout after each command */
    disable_statement_timeout();

    if (xact_started)
    {
        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 contains PlannedStmt nodes */
static bool
IsTransactionExitStmtList(List *pstmts)
{
    if (list_length(pstmts) == 1)
    {
        PlannedStmt *pstmt = linitial_node(PlannedStmt, pstmts);

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

/* Test a list that contains PlannedStmt nodes */
static bool
IsTransactionStmtList(List *pstmts)
{
    if (list_length(pstmts) == 1)
    {
        PlannedStmt *pstmt = linitial_node(PlannedStmt, pstmts);

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

/* Release any existing unnamed prepared statement */
static void
drop_unnamed_stmt(void)
{
    /* paranoia to avoid a dangling pointer in case of error */
    if (unnamed_stmt_psrc)
    {
        CachedPlanSource *psrc = unnamed_stmt_psrc;

        unnamed_stmt_psrc = NULL;
        DropCachedPlan(psrc);
    }
}


/* --------------------------------
 *      signal handler routines used in PostgresMain()
 * --------------------------------
 */

/*
 * quickdie() occurs when signaled SIGQUIT by the postmaster.
 *
 * Either some backend has bought the farm, or we've been told to shut down
 * "immediately"; so we need to stop what we're doing and exit.
 */
void
quickdie(SIGNAL_ARGS)
{
    sigaddset(&BlockSig, SIGQUIT);  /* prevent nested calls */
    PG_SETMASK(&BlockSig);

    /*
     * Prevent interrupts while exiting; though we just blocked signals that
     * would queue new interrupts, one may have been pending.  We don't want a
     * quickdie() downgraded to a mere query cancel.
     */
    HOLD_INTERRUPTS();

    /*
     * If we're aborting out of client auth, don't risk trying to send
     * anything to the client; we will likely violate the protocol, not to
     * mention that we may have interrupted the guts of OpenSSL or some
     * authentication library.
     */
    if (ClientAuthInProgress && whereToSendOutput == DestRemote)
        whereToSendOutput = DestNone;

    /*
     * Notify the client before exiting, to give a clue on what happened.
     *
     * It's dubious to call ereport() from a signal handler.  It is certainly
     * not async-signal safe.  But it seems better to try, than to disconnect
     * abruptly and leave the client wondering what happened.  It's remotely
     * possible that we crash or hang while trying to send the message, but
     * receiving a SIGQUIT is a sign that something has already gone badly
     * wrong, so there's not much to lose.  Assuming the postmaster is still
     * running, it will SIGKILL us soon if we get stuck for some reason.
     *
     * One thing we can do to make this a tad safer is to clear the error
     * context stack, so that context callbacks are not called.  That's a lot
     * less code that could be reached here, and the context info is unlikely
     * to be very relevant to a SIGQUIT report anyway.
     */
    error_context_stack = NULL;

    /*
     * When responding to a postmaster-issued signal, we send the message only
     * to the client; sending to the server log just creates log spam, plus
     * it's more code that we need to hope will work in a signal handler.
     *
     * Ideally these should be ereport(FATAL), but then we'd not get control
     * back to force the correct type of process exit.
     */
    switch (GetQuitSignalReason())
    {
        case PMQUIT_NOT_SENT:
            /* Hmm, SIGQUIT arrived out of the blue */
            ereport(WARNING,
                    (errcode(ERRCODE_ADMIN_SHUTDOWN),
                     errmsg("terminating connection because of unexpected SIGQUIT signal")));
            break;
        case PMQUIT_FOR_CRASH:
            /* A crash-and-restart cycle is in progress */
            ereport(WARNING_CLIENT_ONLY,
                    (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.")));
            break;
        case PMQUIT_FOR_STOP:
            /* Immediate-mode stop */
            ereport(WARNING_CLIENT_ONLY,
                    (errcode(ERRCODE_ADMIN_SHUTDOWN),
                     errmsg("terminating connection due to immediate shutdown command")));
            break;
    }

    /*
     * We DO NOT want to run proc_exit() or atexit() callbacks -- 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.  The callbacks wouldn't be safe to run from a signal handler,
     * anyway.
     *
     * Note we do _exit(2) not _exit(0).  This is to force the postmaster into
     * a system reset cycle if someone sends a manual SIGQUIT to a random
     * backend.  This is necessary precisely because we don't clean up our
     * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
     * should ensure the postmaster sees this as a crash, too, but no harm in
     * being doubly sure.)
     */
    _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;
    }

    /* for the statistics collector */
    pgStatSessionEndCause = DISCONNECT_KILLED;

    /* If we're still here, waken anything waiting on the process latch */
    SetLatch(MyLatch);

    /*
     * If we're in single user mode, we want to quit immediately - we can't
     * rely on latches as they wouldn't work when stdin/stdout is a file.
     * Rather ugly, but it's unlikely to be worthwhile to invest much more
     * effort just for the benefit of single user mode.
     */
    if (DoingCommandRead && whereToSendOutput != DestRemote)
        ProcessInterrupts();

    errno = save_errno;
}

/*
 * 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 we're still here, waken anything waiting on the process latch */
    SetLatch(MyLatch);

    errno = save_errno;
}

/* signal handler for floating point exception */
void
FloatExceptionHandler(SIGNAL_ARGS)
{
    /* We're not returning, so no need to save errno */
    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.")));
}

/*
 * RecoveryConflictInterrupt: out-of-line portion of recovery conflict
 * handling following receipt of SIGUSR1. Designed to be similar to die()
 * and StatementCancelHandler(). Called only by a normal user backend
 * that begins a transaction during recovery.
 */
void
RecoveryConflictInterrupt(ProcSignalReason reason)
{
    int         save_errno = errno;

    /*
     * Don't joggle the elbow of proc_exit
     */
    if (!proc_exit_inprogress)
    {
        RecoveryConflictReason = reason;
        switch (reason)
        {
            case PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK:

                /*
                 * If we aren't waiting for a lock we can never deadlock.
                 */
                if (!IsWaitingForLock())
                    return;

                /* Intentional fall through to check wait for pin */
                /* FALLTHROUGH */

            case PROCSIG_RECOVERY_CONFLICT_BUFFERPIN:

                /*
                 * If PROCSIG_RECOVERY_CONFLICT_BUFFERPIN is requested but we
                 * aren't blocking the Startup process there is nothing more
                 * to do.
                 *
                 * When PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK is
                 * requested, if we're waiting for locks and the startup
                 * process is not waiting for buffer pin (i.e., also waiting
                 * for locks), we set the flag so that ProcSleep() will check
                 * for deadlocks.
                 */
                if (!HoldingBufferPinThatDelaysRecovery())
                {
                    if (reason == PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK &&
                        GetStartupBufferPinWaitBufId() < 0)
                        CheckDeadLockAlert();
                    return;
                }

                MyProc->recoveryConflictPending = true;

                /* Intentional fall through to error handling */
                /* FALLTHROUGH */

            case PROCSIG_RECOVERY_CONFLICT_LOCK:
            case PROCSIG_RECOVERY_CONFLICT_TABLESPACE:
            case PROCSIG_RECOVERY_CONFLICT_SNAPSHOT:

                /*
                 * If we aren't in a transaction any longer then ignore.
                 */
                if (!IsTransactionOrTransactionBlock())
                    return;

                /*
                 * If we can abort just the current subtransaction then we are
                 * OK to throw an ERROR to resolve the conflict. Otherwise
                 * drop through to the FATAL case.
                 *
                 * XXX other times that we can throw just an ERROR *may* be
                 * PROCSIG_RECOVERY_CONFLICT_LOCK if no locks are held in
                 * parent transactions
                 *
                 * PROCSIG_RECOVERY_CONFLICT_SNAPSHOT if no snapshots are held
                 * by parent transactions and the transaction is not
                 * transaction-snapshot mode
                 *
                 * PROCSIG_RECOVERY_CONFLICT_TABLESPACE if no temp files or
                 * cursors open in parent transactions
                 */
                if (!IsSubTransaction())
                {
                    /*
                     * If we already aborted then we no longer need to cancel.
                     * We do this here since we do not wish to ignore aborted
                     * subtransactions, which must cause FATAL, currently.
                     */
                    if (IsAbortedTransactionBlockState())
                        return;

                    RecoveryConflictPending = true;
                    QueryCancelPending = true;
                    InterruptPending = true;
                    break;
                }

                /* Intentional fall through to session cancel */
                /* FALLTHROUGH */

            case PROCSIG_RECOVERY_CONFLICT_DATABASE:
                RecoveryConflictPending = true;
                ProcDiePending = true;
                InterruptPending = true;
                break;

            default:
                elog(FATAL, "unrecognized conflict mode: %d",
                     (int) reason);
        }

        Assert(RecoveryConflictPending && (QueryCancelPending || ProcDiePending));

        /*
         * All conflicts apart from database cause dynamic errors where the
         * command or transaction can be retried at a later point with some
         * potential for success. No need to reset this, since non-retryable
         * conflict errors are currently FATAL.
         */
        if (reason == PROCSIG_RECOVERY_CONFLICT_DATABASE)
            RecoveryConflictRetryable = false;
    }

    /*
     * Set the process latch. This function essentially emulates signal
     * handlers like die() and StatementCancelHandler() and it seems prudent
     * to behave similarly as they do.
     */
    SetLatch(MyLatch);

    errno = save_errno;
}

/*
 * 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 any interrupts now? */
    if (InterruptHoldoffCount != 0 || CritSectionCount != 0)
        return;
    InterruptPending = false;

    if (ProcDiePending)
    {
        ProcDiePending = false;
        QueryCancelPending = false; /* ProcDie trumps QueryCancel */
        LockErrorCleanup();
        /* As in quickdie, don't risk sending to client during auth */
        if (ClientAuthInProgress && whereToSendOutput == DestRemote)
            whereToSendOutput = DestNone;
        if (ClientAuthInProgress)
            ereport(FATAL,
                    (errcode(ERRCODE_QUERY_CANCELED),
                     errmsg("canceling authentication due to timeout")));
        else if (IsAutoVacuumWorkerProcess())
            ereport(FATAL,
                    (errcode(ERRCODE_ADMIN_SHUTDOWN),
                     errmsg("terminating autovacuum process due to administrator command")));
        else if (IsLogicalWorker())
            ereport(FATAL,
                    (errcode(ERRCODE_ADMIN_SHUTDOWN),
                     errmsg("terminating logical replication worker due to administrator command")));
        else if (IsLogicalLauncher())
        {
            ereport(DEBUG1,
                    (errmsg("logical replication launcher shutting down")));

            /*
             * The logical replication launcher can be stopped at any time.
             * Use exit status 1 so the background worker is restarted.
             */
            proc_exit(1);
        }
        else if (RecoveryConflictPending && RecoveryConflictRetryable)
        {
            pgstat_report_recovery_conflict(RecoveryConflictReason);
            ereport(FATAL,
                    (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                     errmsg("terminating connection due to conflict with recovery"),
                     errdetail_recovery_conflict()));
        }
        else if (RecoveryConflictPending)
        {
            /* Currently there is only one non-retryable recovery conflict */
            Assert(RecoveryConflictReason == PROCSIG_RECOVERY_CONFLICT_DATABASE);
            pgstat_report_recovery_conflict(RecoveryConflictReason);
            ereport(FATAL,
                    (errcode(ERRCODE_DATABASE_DROPPED),
                     errmsg("terminating connection due to conflict with recovery"),
                     errdetail_recovery_conflict()));
        }
        else if (IsBackgroundWorker)
            ereport(FATAL,
                    (errcode(ERRCODE_ADMIN_SHUTDOWN),
                     errmsg("terminating background worker \"%s\" due to administrator command",
                            MyBgworkerEntry->bgw_type)));
        else
            ereport(FATAL,
                    (errcode(ERRCODE_ADMIN_SHUTDOWN),
                     errmsg("terminating connection due to administrator command")));
    }
    if (ClientConnectionLost)
    {
        QueryCancelPending = false; /* lost connection trumps QueryCancel */
        LockErrorCleanup();
        /* don't send to client, we already know the connection to be dead. */
        whereToSendOutput = DestNone;
        ereport(FATAL,
                (errcode(ERRCODE_CONNECTION_FAILURE),
                 errmsg("connection to client lost")));
    }

    /*
     * If a recovery conflict happens while we are waiting for input from the
     * client, the client is presumably just sitting idle in a transaction,
     * preventing recovery from making progress.  Terminate the connection to
     * dislodge it.
     */
    if (RecoveryConflictPending && DoingCommandRead)
    {
        QueryCancelPending = false; /* this trumps QueryCancel */
        RecoveryConflictPending = false;
        LockErrorCleanup();
        pgstat_report_recovery_conflict(RecoveryConflictReason);
        ereport(FATAL,
                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                 errmsg("terminating connection due to conflict with recovery"),
                 errdetail_recovery_conflict(),
                 errhint("In a moment you should be able to reconnect to the"
                         " database and repeat your command.")));
    }

    /*
     * Don't allow query cancel interrupts while reading input from the
     * client, because we might lose sync in the FE/BE protocol.  (Die
     * interrupts are OK, because we won't read any further messages from the
     * client in that case.)
     */
    if (QueryCancelPending && QueryCancelHoldoffCount != 0)
    {
        /*
         * Re-arm InterruptPending so that we process the cancel request as
         * soon as we're done reading the message.
         */
        InterruptPending = true;
    }
    else if (QueryCancelPending)
    {
        bool        lock_timeout_occurred;
        bool        stmt_timeout_occurred;

        QueryCancelPending = false;

        /*
         * If LOCK_TIMEOUT and STATEMENT_TIMEOUT indicators are both set, we
         * need to clear both, so always fetch both.
         */
        lock_timeout_occurred = get_timeout_indicator(LOCK_TIMEOUT, true);
        stmt_timeout_occurred = get_timeout_indicator(STATEMENT_TIMEOUT, true);

        /*
         * If both were set, we want to report whichever timeout completed
         * earlier; this ensures consistent behavior if the machine is slow
         * enough that the second timeout triggers before we get here.  A tie
         * is arbitrarily broken in favor of reporting a lock timeout.
         */
        if (lock_timeout_occurred && stmt_timeout_occurred &&
            get_timeout_finish_time(STATEMENT_TIMEOUT) < get_timeout_finish_time(LOCK_TIMEOUT))
            lock_timeout_occurred = false;  /* report stmt timeout */

        if (lock_timeout_occurred)
        {
            LockErrorCleanup();
            ereport(ERROR,
                    (errcode(ERRCODE_LOCK_NOT_AVAILABLE),
                     errmsg("canceling statement due to lock timeout")));
        }
        if (stmt_timeout_occurred)
        {
            LockErrorCleanup();
            ereport(ERROR,
                    (errcode(ERRCODE_QUERY_CANCELED),
                     errmsg("canceling statement due to statement timeout")));
        }
        if (IsAutoVacuumWorkerProcess())
        {
            LockErrorCleanup();
            ereport(ERROR,
                    (errcode(ERRCODE_QUERY_CANCELED),
                     errmsg("canceling autovacuum task")));
        }
        if (RecoveryConflictPending)
        {
            RecoveryConflictPending = false;
            LockErrorCleanup();
            pgstat_report_recovery_conflict(RecoveryConflictReason);
            ereport(ERROR,
                    (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                     errmsg("canceling statement due to conflict with recovery"),
                     errdetail_recovery_conflict()));
        }

        /*
         * If we are reading a command from the client, just ignore the cancel
         * request --- sending an extra error message won't accomplish
         * anything.  Otherwise, go ahead and throw the error.
         */
        if (!DoingCommandRead)
        {
            LockErrorCleanup();
            ereport(ERROR,
                    (errcode(ERRCODE_QUERY_CANCELED),
                     errmsg("canceling statement due to user request")));
        }
    }

    if (IdleInTransactionSessionTimeoutPending)
    {
        /*
         * If the GUC has been reset to zero, ignore the signal.  This is
         * important because the GUC update itself won't disable any pending
         * interrupt.
         */
        if (IdleInTransactionSessionTimeout > 0)
            ereport(FATAL,
                    (errcode(ERRCODE_IDLE_IN_TRANSACTION_SESSION_TIMEOUT),
                     errmsg("terminating connection due to idle-in-transaction timeout")));
        else
            IdleInTransactionSessionTimeoutPending = false;
    }

    if (IdleSessionTimeoutPending)
    {
        /* As above, ignore the signal if the GUC has been reset to zero. */
        if (IdleSessionTimeout > 0)
            ereport(FATAL,
                    (errcode(ERRCODE_IDLE_SESSION_TIMEOUT),
                     errmsg("terminating connection due to idle-session timeout")));
        else
            IdleSessionTimeoutPending = false;
    }

    if (ProcSignalBarrierPending)
        ProcessProcSignalBarrier();

    if (ParallelMessagePending)
        HandleParallelMessages();
}


/*
 * IA64-specific code to fetch the AR.BSP register for stack depth checks.
 *
 * We currently support gcc, icc, and HP-UX's native compiler here.
 *
 * Note: while icc accepts gcc asm blocks on x86[_64], this is not true on
 * ia64 (at least not in icc versions before 12.x).  So we have to carry a
 * separate implementation for it.
 */
#if defined(__ia64__) || defined(__ia64)

#if defined(__hpux) && !defined(__GNUC__) && !defined(__INTEL_COMPILER)
/* Assume it's HP-UX native compiler */
#include <ia64/sys/inline.h>
#define ia64_get_bsp() ((char *) (_Asm_mov_from_ar(_AREG_BSP, _NO_FENCE)))
#elif defined(__INTEL_COMPILER)
/* icc */
#include <asm/ia64regs.h>
#define ia64_get_bsp() ((char *) __getReg(_IA64_REG_AR_BSP))
#else
/* gcc */
static __inline__ char *
ia64_get_bsp(void)
{
    char       *ret;

    /* the ;; is a "stop", seems to be required before fetching BSP */
    __asm__ __volatile__(
                         ";;\n"
                         "  mov %0=ar.bsp   \n"
:                        "=r"(ret));

    return ret;
}
#endif
#endif                          /* IA64 */


/*
 * set_stack_base: set up reference point for stack depth checking
 *
 * Returns the old reference point, if any.
 */
pg_stack_base_t
set_stack_base(void)
{
    char        stack_base;
    pg_stack_base_t old;

#if defined(__ia64__) || defined(__ia64)
    old.stack_base_ptr = stack_base_ptr;
    old.register_stack_base_ptr = register_stack_base_ptr;
#else
    old = stack_base_ptr;
#endif

    /* Set up reference point for stack depth checking */
    stack_base_ptr = &stack_base;
#if defined(__ia64__) || defined(__ia64)
    register_stack_base_ptr = ia64_get_bsp();
#endif

    return old;
}

/*
 * restore_stack_base: restore reference point for stack depth checking
 *
 * This can be used after set_stack_base() to restore the old value. This
 * is currently only used in PL/Java. When PL/Java calls a backend function
 * from different thread, the thread's stack is at a different location than
 * the main thread's stack, so it sets the base pointer before the call, and
 * restores it afterwards.
 */
void
restore_stack_base(pg_stack_base_t base)
{
#if defined(__ia64__) || defined(__ia64)
    stack_base_ptr = base.stack_base_ptr;
    register_stack_base_ptr = base.register_stack_base_ptr;
#else
    stack_base_ptr = base;
#endif
}

/*
 * check_stack_depth/stack_is_too_deep: 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.
 *
 * check_stack_depth() just throws an error summarily.  stack_is_too_deep()
 * can be used by code that wants to handle the error condition itself.
 */
void
check_stack_depth(void)
{
    if (stack_is_too_deep())
    {
        ereport(ERROR,
                (errcode(ERRCODE_STATEMENT_TOO_COMPLEX),
                 errmsg("stack depth limit exceeded"),
                 errhint("Increase the configuration parameter \"max_stack_depth\" (currently %dkB), "
                         "after ensuring the platform's stack depth limit is adequate.",
                         max_stack_depth)));
    }
}

bool
stack_is_too_deep(void)
{
    char        stack_top_loc;
    long        stack_depth;

    /*
     * Compute distance from reference point to my local variables
     */
    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)
        return true;

    /*
     * On IA64 there is a separate "register" stack that requires its own
     * independent check.  For this, we have to measure the change in the
     * "BSP" pointer from PostgresMain to here.  Logic is just as above,
     * except that we know IA64's register stack grows up.
     *
     * Note we assume that the same max_stack_depth applies to both stacks.
     */
#if defined(__ia64__) || defined(__ia64)
    stack_depth = (long) (ia64_get_bsp() - register_stack_base_ptr);

    if (stack_depth > max_stack_depth_bytes &&
        register_stack_base_ptr != NULL)
        return true;
#endif                          /* IA64 */

    return false;
}

/* GUC check hook for max_stack_depth */
bool
check_max_stack_depth(int *newval, void **extra, 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)
    {
        GUC_check_errdetail("\"max_stack_depth\" must not exceed %ldkB.",
                            (stack_rlimit - STACK_DEPTH_SLOP) / 1024L);
        GUC_check_errhint("Increase the platform's stack depth limit via \"ulimit -s\" or local equivalent.");
        return false;
    }
    return true;
}

/* GUC assign hook for max_stack_depth */
void
assign_max_stack_depth(int newval, void *extra)
{
    long        newval_bytes = newval * 1024L;

    max_stack_depth_bytes = newval_bytes;
}


/*
 * 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)
{
    const char *tmp = NULL;

    switch (arg[0])
    {
        case 's':               /* seqscan */
            tmp = "enable_seqscan";
            break;
        case 'i':               /* indexscan */
            tmp = "enable_indexscan";
            break;
        case 'o':               /* indexonlyscan */
            tmp = "enable_indexonlyscan";
            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;
}


/* ----------------------------------------------------------------
 * process_postgres_switches
 *     Parse command line arguments for PostgresMain
 *
 * This is called twice, once for the "secure" options coming from the
 * postmaster or command line, and once for the "insecure" options coming
 * from the client's startup packet.  The latter have the same syntax but
 * may be restricted in what they can do.
 *
 * argv[0] is ignored in either case (it's assumed to be the program name).
 *
 * ctx is PGC_POSTMASTER for secure options, PGC_BACKEND for insecure options
 * coming from the client, or PGC_SU_BACKEND for insecure options coming from
 * a superuser client.
 *
 * If a database name is present in the command line arguments, it's
 * returned into *dbname (this is allowed only if *dbname is initially NULL).
 * ----------------------------------------------------------------
 */
void
process_postgres_switches(int argc, char *argv[], GucContext ctx,
                          const char **dbname)
{
    bool        secure = (ctx == PGC_POSTMASTER);
    int         errs = 0;
    GucSource   gucsource;
    int         flag;

    if (secure)
    {
        gucsource = PGC_S_ARGV; /* switches came from command line */

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

#ifdef HAVE_INT_OPTERR

    /*
     * Turn this off because it's either printed to stderr and not the log
     * where we'd want it, or argv[0] is now "--single", which would make for
     * a weird error message.  We print our own error message below.
     */
    opterr = 0;
#endif

    /*
     * 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, "B:bc:C:D:d:EeFf:h:ijk:lN:nOPp:r:S:sTt:v:W:-:")) != -1)
    {
        switch (flag)
        {
            case 'B':
                SetConfigOption("shared_buffers", optarg, ctx, gucsource);
                break;

            case 'b':
                /* Undocumented flag used for binary upgrades */
                if (secure)
                    IsBinaryUpgrade = true;
                break;

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

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

            case 'd':
                set_debug_options(atoi(optarg), ctx, gucsource);
                break;

            case 'E':
                if (secure)
                    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':
                if (secure)
                    UseSemiNewlineNewline = true;
                break;

            case 'k':
                SetConfigOption("unix_socket_directories", 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 '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':
                SetConfigOption("log_statement_stats", "true", ctx, gucsource);
                break;

            case 'T':
                /* ignored for consistency with the postmaster */
                break;

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

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

            case 'v':

                /*
                 * -v is no longer used in normal operation, since
                 * FrontendProtocol is already set before we get here. We keep
                 * the switch only for possible use in standalone operation,
                 * in case we ever support using normal FE/BE protocol with a
                 * standalone backend.
                 */
                if (secure)
                    FrontendProtocol = (ProtocolVersion) atoi(optarg);
                break;

            case 'W':
                SetConfigOption("post_auth_delay", optarg, ctx, gucsource);
                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)));
                    }
                    SetConfigOption(name, value, ctx, gucsource);
                    free(name);
                    if (value)
                        free(value);
                    break;
                }

            default:
                errs++;
                break;
        }

        if (errs)
            break;
    }

    /*
     * Optional database name should be there only if *dbname is NULL.
     */
    if (!errs && dbname && *dbname == NULL && argc - optind >= 1)
        *dbname = strdup(argv[optind++]);

    if (errs || argc != optind)
    {
        if (errs)
            optind--;           /* complain about the previous argument */

        /* spell the error message a bit differently depending on context */
        if (IsUnderPostmaster)
            ereport(FATAL,
                    errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("invalid command-line argument for server process: %s", argv[optind]),
                    errhint("Try \"%s --help\" for more information.", progname));
        else
            ereport(FATAL,
                    errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("%s: invalid command-line argument: %s",
                           progname, argv[optind]),
                    errhint("Try \"%s --help\" for more information.", progname));
    }

    /*
     * Reset getopt(3) library so that it will work correctly in subprocesses
     * or when this function is called a second time with another array.
     */
    optind = 1;
#ifdef HAVE_INT_OPTRESET
    optreset = 1;               /* some systems need this too */
#endif
}


/* ----------------------------------------------------------------
 * 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.)
 * dbname is the name of the database to connect to, or NULL if the database
 * name should be extracted from the command line arguments or defaulted.
 * username is the PostgreSQL user name to be used for the session.
 * ----------------------------------------------------------------
 */
void
PostgresMain(int argc, char *argv[],
             const char *dbname,
             const char *username)
{
    int         firstchar;
    StringInfoData input_message;
    sigjmp_buf  local_sigjmp_buf;
    volatile bool send_ready_for_query = true;
    bool        idle_in_transaction_timeout_enabled = false;
    bool        idle_session_timeout_enabled = false;

    /* Initialize startup process environment if necessary. */
    if (!IsUnderPostmaster)
        InitStandaloneProcess(argv[0]);

    SetProcessingMode(InitProcessing);

    /*
     * Set default values for command-line options.
     */
    if (!IsUnderPostmaster)
        InitializeGUCOptions();

    /*
     * Parse command-line options.
     */
    process_postgres_switches(argc, argv, PGC_POSTMASTER, &dbname);

    /* Must have gotten a database name, or have a default (the username) */
    if (dbname == NULL)
    {
        dbname = username;
        if (dbname == NULL)
            ereport(FATAL,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("%s: no database nor user name specified",
                            progname)));
    }

    /* Acquire configuration parameters, unless inherited from postmaster */
    if (!IsUnderPostmaster)
    {
        if (!SelectConfigFiles(userDoption, progname))
            proc_exit(1);
    }

    /*
     * Set up signal handlers.  (InitPostmasterChild or InitStandaloneProcess
     * has already set up BlockSig and made that the active signal mask.)
     *
     * 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.)
     */
    if (am_walsender)
        WalSndSignals();
    else
    {
        pqsignal(SIGHUP, SignalHandlerForConfigReload);
        pqsignal(SIGINT, StatementCancelHandler);   /* cancel current query */
        pqsignal(SIGTERM, die); /* cancel current query and exit */

        /*
         * In a postmaster child backend, replace SignalHandlerForCrashExit
         * with quickdie, so we can tell the client we're dying.
         *
         * 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 */
        InitializeTimeouts();   /* establishes SIGALRM handler */

        /*
         * 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, procsignal_sigusr1_handler);
        pqsignal(SIGUSR2, SIG_IGN);
        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 */
    }

    if (!IsUnderPostmaster)
    {
        /*
         * Validate we have been given a reasonable-looking DataDir (if under
         * postmaster, assume postmaster did this already).
         */
        checkDataDir();

        /* Change into DataDir (if under postmaster, was done already) */
        ChangeToDataDir();

        /*
         * Create lockfile for data directory.
         */
        CreateDataDirLockFile(false);

        /* read control file (error checking and contains config ) */
        LocalProcessControlFile(false);

        /* Initialize MaxBackends (if under postmaster, was done already) */
        InitializeMaxBackends();
    }

    /* Early initialization */
    BaseInit();

    /*
     * 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

    /* We need to allow SIGINT, etc during the initial transaction */
    PG_SETMASK(&UnBlockSig);

    /*
     * 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.
     */
    InitPostgres(dbname, InvalidOid, username, InvalidOid, NULL, false);

    /*
     * If the PostmasterContext is still around, recycle the space; we don't
     * need it anymore after InitPostgres completes.  Note this does not trash
     * *MyProcPort, because ConnCreate() allocated that space with malloc()
     * ... else we'd need to copy the Port data first.  Also, subsidiary data
     * such as the username isn't lost either; see ProcessStartupPacket().
     */
    if (PostmasterContext)
    {
        MemoryContextDelete(PostmasterContext);
        PostmasterContext = NULL;
    }

    SetProcessingMode(NormalProcessing);

    /*
     * 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);

    /* Perform initialization specific to a WAL sender process. */
    if (am_walsender)
        InitWalSender();

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

    /*
     * Send this backend's cancellation info to the frontend.
     */
    if (whereToSendOutput == DestRemote)
    {
        StringInfoData buf;

        pq_beginmessage(&buf, 'K');
        pq_sendint32(&buf, (int32) MyProcPid);
        pq_sendint32(&buf, (int32) MyCancelKey);
        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_SIZES);

    /*
     * Create memory context and buffer used for RowDescription messages. As
     * SendRowDescriptionMessage(), via exec_describe_statement_message(), is
     * frequently executed for ever single statement, we don't want to
     * allocate a separate buffer every time.
     */
    row_description_context = AllocSetContextCreate(TopMemoryContext,
                                                    "RowDescriptionContext",
                                                    ALLOCSET_DEFAULT_SIZES);
    MemoryContextSwitchTo(row_description_context);
    initStringInfo(&row_description_buf);
    MemoryContextSwitchTo(TopMemoryContext);

    /*
     * 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.)
     *
     * Note that we use sigsetjmp(..., 1), so that this function's signal mask
     * (to wit, UnBlockSig) will be restored when longjmp'ing to here.  This
     * is essential in case we longjmp'd out of a signal handler on a platform
     * where that leaves the signal blocked.  It's not redundant with the
     * unblock in AbortTransaction() because the latter is only called if we
     * were inside a transaction.
     */

    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 any active timeout requests.  (In
         * future we might want to allow some timeout requests to survive, but
         * at minimum it'd be necessary to do reschedule_timeouts(), in case
         * we got here because of a query cancel interrupting the SIGALRM
         * interrupt handler.)  Note in particular that we must clear the
         * statement and lock timeout indicators, to prevent any future plain
         * query cancels from being misreported as timeouts in case we're
         * forgetting a timeout cancel.
         */
        disable_all_timeouts(false);
        QueryCancelPending = false; /* second to avoid race condition */

        /* Not reading from the client anymore. */
        DoingCommandRead = false;

        /* 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();

        if (am_walsender)
            WalSndErrorCleanup();

        PortalErrorCleanup();
        SPICleanup();

        /*
         * We can't release replication slots inside AbortTransaction() as we
         * need to be able to start and abort transactions while having a slot
         * acquired. But we never need to hold them across top level errors,
         * so releasing here is fine. There's another cleanup in ProcKill()
         * ensuring we'll correctly cleanup on FATAL errors as well.
         */
        if (MyReplicationSlot != NULL)
            ReplicationSlotRelease();

        /* We also want to cleanup temporary slots on error. */
        ReplicationSlotCleanup();

        jit_reset_after_error();

        /*
         * 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;

        /*
         * If an error occurred while we were reading a message from the
         * client, we have potentially lost track of where the previous
         * message ends and the next one begins.  Even though we have
         * otherwise recovered from the error, we cannot safely read any more
         * messages from the client, so there isn't much we can do with the
         * connection anymore.
         */
        if (pq_is_reading_msg())
            ereport(FATAL,
                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                     errmsg("terminating connection because protocol synchronization was lost")));

        /* Now we can allow interrupts again */
        RESUME_INTERRUPTS();
    }

    /* We can now handle ereport(ERROR) */
    PG_exception_stack = &local_sigjmp_buf;

    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);

        /*
         * Also consider releasing our catalog snapshot if any, so that it's
         * not preventing advance of global xmin while we wait for the client.
         */
        InvalidateCatalogSnapshotConditionally();

        /*
         * (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).  The notification
         * processor wants a call too, if we are not in a transaction block.
         *
         * Also, if an idle timeout is enabled, start the timer for that.
         */
        if (send_ready_for_query)
        {
            if (IsAbortedTransactionBlockState())
            {
                set_ps_display("idle in transaction (aborted)");
                pgstat_report_activity(STATE_IDLEINTRANSACTION_ABORTED, NULL);

                /* Start the idle-in-transaction timer */
                if (IdleInTransactionSessionTimeout > 0)
                {
                    idle_in_transaction_timeout_enabled = true;
                    enable_timeout_after(IDLE_IN_TRANSACTION_SESSION_TIMEOUT,
                                         IdleInTransactionSessionTimeout);
                }
            }
            else if (IsTransactionOrTransactionBlock())
            {
                set_ps_display("idle in transaction");
                pgstat_report_activity(STATE_IDLEINTRANSACTION, NULL);

                /* Start the idle-in-transaction timer */
                if (IdleInTransactionSessionTimeout > 0)
                {
                    idle_in_transaction_timeout_enabled = true;
                    enable_timeout_after(IDLE_IN_TRANSACTION_SESSION_TIMEOUT,
                                         IdleInTransactionSessionTimeout);
                }
            }
            else
            {
                /* Send out notify signals and transmit self-notifies */
                ProcessCompletedNotifies();

                /*
                 * Also process incoming notifies, if any.  This is mostly to
                 * ensure stable behavior in tests: if any notifies were
                 * received during the just-finished transaction, they'll be
                 * seen by the client before ReadyForQuery is.
                 */
                if (notifyInterruptPending)
                    ProcessNotifyInterrupt();

                pgstat_report_stat(false);

                set_ps_display("idle");
                pgstat_report_activity(STATE_IDLE, NULL);

                /* Start the idle-session timer */
                if (IdleSessionTimeout > 0)
                {
                    idle_session_timeout_enabled = true;
                    enable_timeout_after(IDLE_SESSION_TIMEOUT,
                                         IdleSessionTimeout);
                }
            }

            /* Report any recently-changed GUC options */
            ReportChangedGUCOptions();

            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.)
         */
        DoingCommandRead = true;

        /*
         * (3) read a command (loop blocks here)
         */
        firstchar = ReadCommand(&input_message);

        /*
         * (4) turn off the idle-in-transaction and idle-session timeouts, if
         * active.  We do this before step (5) so that any last-moment timeout
         * is certain to be detected in step (5).
         *
         * At most one of these timeouts will be active, so there's no need to
         * worry about combining the timeout.c calls into one.
         */
        if (idle_in_transaction_timeout_enabled)
        {
            disable_timeout(IDLE_IN_TRANSACTION_SESSION_TIMEOUT, false);
            idle_in_transaction_timeout_enabled = false;
        }
        if (idle_session_timeout_enabled)
        {
            disable_timeout(IDLE_SESSION_TIMEOUT, false);
            idle_session_timeout_enabled = false;
        }

        /*
         * (5) disable async signal conditions again.
         *
         * Query cancel is supposed to be a no-op when there is no query in
         * progress, so if a query cancel arrived while we were idle, just
         * reset QueryCancelPending. ProcessInterrupts() has that effect when
         * it's called when DoingCommandRead is set, so check for interrupts
         * before resetting DoingCommandRead.
         */
        CHECK_FOR_INTERRUPTS();
        DoingCommandRead = false;

        /*
         * (6) check for any other interesting events that happened while we
         * slept.
         */
        if (ConfigReloadPending)
        {
            ConfigReloadPending = false;
            ProcessConfigFile(PGC_SIGHUP);
        }

        /*
         * (7) 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);

                    if (am_walsender)
                    {
                        if (!exec_replication_command(query_string))
                            exec_simple_query(query_string);
                    }
                    else
                        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;

                    forbidden_in_wal_sender(firstchar);

                    /* 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)
                    {
                        paramTypes = (Oid *) palloc(numParams * sizeof(Oid));
                        for (int 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 */
                forbidden_in_wal_sender(firstchar);

                /* 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;

                    forbidden_in_wal_sender(firstchar);

                    /* 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 */
                forbidden_in_wal_sender(firstchar);

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

                /* Report query to various monitoring facilities. */
                pgstat_report_activity(STATE_FASTPATH, NULL);
                set_ps_display("<FASTPATH>");

                /* 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);

                HandleFunctionRequest(&input_message);

                /* commit the function-invocation transaction */
                finish_xact_command();

                send_ready_for_query = true;
                break;

            case 'C':           /* close */
                {
                    int         close_type;
                    const char *close_target;

                    forbidden_in_wal_sender(firstchar);

                    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;

                    forbidden_in_wal_sender(firstchar);

                    /* 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 EOF:

                /* for the statistics collector */
                pgStatSessionEndCause = DISCONNECT_CLIENT_EOF;

                /* FALLTHROUGH */

            case 'X':

                /*
                 * 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 */
}

/*
 * Throw an error if we're a WAL sender process.
 *
 * This is used to forbid anything else than simple query protocol messages
 * in a WAL sender process.  'firstchar' specifies what kind of a forbidden
 * message was received, and is used to construct the error message.
 */
static void
forbidden_in_wal_sender(char firstchar)
{
    if (am_walsender)
    {
        if (firstchar == 'F')
            ereport(ERROR,
                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                     errmsg("fastpath function calls not supported in a replication connection")));
        else
            ereport(ERROR,
                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                     errmsg("extended query protocol not supported in a replication connection")));
    }
}


/*
 * Obtain platform stack depth limit (in bytes)
 *
 * Return -1 if unknown
 */
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 = LONG_MAX;
        /* rlim_cur is probably of an unsigned type, so check for overflow */
        else if (rlim.rlim_cur >= LONG_MAX)
            val = LONG_MAX;
        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);
}

void
ShowUsage(const char *title)
{
    StringInfoData str;
    struct timeval user,
                sys;
    struct timeval elapse_t;
    struct rusage r;

    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 ixrss, idrss, isrss.  It takes
     * some work to interpret them, and most platforms don't fill them in.
     */
    initStringInfo(&str);

    appendStringInfoString(&str, "! system usage stats:\n");
    appendStringInfo(&str,
                     "!\t%ld.%06ld s user, %ld.%06ld s system, %ld.%06ld s elapsed\n",
                     (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),
                     (long) (elapse_t.tv_sec - Save_t.tv_sec),
                     (long) (elapse_t.tv_usec - Save_t.tv_usec));
    appendStringInfo(&str,
                     "!\t[%ld.%06ld s user, %ld.%06ld s system 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 kB max resident size\n",
#if defined(__darwin__)
    /* in bytes on macOS */
                     r.ru_maxrss / 1024
#else
    /* in kilobytes on most other platforms */
                     r.ru_maxrss
#endif
        );
    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 */

    /* remove trailing newline */
    if (str.data[str.len - 1] == '\n')
        str.data[--str.len] = '\0';

    ereport(LOG,
            (errmsg_internal("%s", title),
             errdetail_internal("%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(MyStartTimestamp,
                        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)));
}

/*
 * Start statement timeout timer, if enabled.
 *
 * If there's already a timeout running, don't restart the timer.  That
 * enables compromises between accuracy of timeouts and cost of starting a
 * timeout.
 */
static void
enable_statement_timeout(void)
{
    /* must be within an xact */
    Assert(xact_started);

    if (StatementTimeout > 0)
    {
        if (!get_timeout_active(STATEMENT_TIMEOUT))
            enable_timeout_after(STATEMENT_TIMEOUT, StatementTimeout);
    }
    else
    {
        if (get_timeout_active(STATEMENT_TIMEOUT))
            disable_timeout(STATEMENT_TIMEOUT, false);
    }
}

/*
 * Disable statement timeout, if active.
 */
static void
disable_statement_timeout(void)
{
    if (get_timeout_active(STATEMENT_TIMEOUT))
        disable_timeout(STATEMENT_TIMEOUT, false);
}