spi.c

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/*-------------------------------------------------------------------------
 *
 * spi.c
 *              Server Programming Interface
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/executor/spi.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/htup_details.h"
#include "access/printtup.h"
#include "access/sysattr.h"
#include "access/xact.h"
#include "catalog/heap.h"
#include "catalog/pg_type.h"
#include "commands/trigger.h"
#include "executor/executor.h"
#include "executor/spi_priv.h"
#include "tcop/pquery.h"
#include "tcop/utility.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/typcache.h"


uint32      SPI_processed = 0;
Oid         SPI_lastoid = InvalidOid;
SPITupleTable *SPI_tuptable = NULL;
int         SPI_result;

static _SPI_connection *_SPI_stack = NULL;
static _SPI_connection *_SPI_current = NULL;
static int  _SPI_stack_depth = 0;       /* allocated size of _SPI_stack */
static int  _SPI_connected = -1;
static int  _SPI_curid = -1;

static Portal SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
                         ParamListInfo paramLI, bool read_only);

static void _SPI_prepare_plan(const char *src, SPIPlanPtr plan);

static void _SPI_prepare_oneshot_plan(const char *src, SPIPlanPtr plan);

static int _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
                  Snapshot snapshot, Snapshot crosscheck_snapshot,
                  bool read_only, bool fire_triggers, long tcount);

static ParamListInfo _SPI_convert_params(int nargs, Oid *argtypes,
                    Datum *Values, const char *Nulls);

static int  _SPI_pquery(QueryDesc *queryDesc, bool fire_triggers, long tcount);

static void _SPI_error_callback(void *arg);

static void _SPI_cursor_operation(Portal portal,
                      FetchDirection direction, long count,
                      DestReceiver *dest);

static SPIPlanPtr _SPI_make_plan_non_temp(SPIPlanPtr plan);
static SPIPlanPtr _SPI_save_plan(SPIPlanPtr plan);

static int  _SPI_begin_call(bool execmem);
static int  _SPI_end_call(bool procmem);
static MemoryContext _SPI_execmem(void);
static MemoryContext _SPI_procmem(void);
static bool _SPI_checktuples(void);


/* =================== interface functions =================== */

int
SPI_connect(void)
{
    int         newdepth;

    /*
     * When procedure called by Executor _SPI_curid expected to be equal to
     * _SPI_connected
     */
    if (_SPI_curid != _SPI_connected)
        return SPI_ERROR_CONNECT;

    if (_SPI_stack == NULL)
    {
        if (_SPI_connected != -1 || _SPI_stack_depth != 0)
            elog(ERROR, "SPI stack corrupted");
        newdepth = 16;
        _SPI_stack = (_SPI_connection *)
            MemoryContextAlloc(TopTransactionContext,
                               newdepth * sizeof(_SPI_connection));
        _SPI_stack_depth = newdepth;
    }
    else
    {
        if (_SPI_stack_depth <= 0 || _SPI_stack_depth <= _SPI_connected)
            elog(ERROR, "SPI stack corrupted");
        if (_SPI_stack_depth == _SPI_connected + 1)
        {
            newdepth = _SPI_stack_depth * 2;
            _SPI_stack = (_SPI_connection *)
                repalloc(_SPI_stack,
                         newdepth * sizeof(_SPI_connection));
            _SPI_stack_depth = newdepth;
        }
    }

    /*
     * We're entering procedure where _SPI_curid == _SPI_connected - 1
     */
    _SPI_connected++;
    Assert(_SPI_connected >= 0 && _SPI_connected < _SPI_stack_depth);

    _SPI_current = &(_SPI_stack[_SPI_connected]);
    _SPI_current->processed = 0;
    _SPI_current->lastoid = InvalidOid;
    _SPI_current->tuptable = NULL;
    _SPI_current->procCxt = NULL;       /* in case we fail to create 'em */
    _SPI_current->execCxt = NULL;
    _SPI_current->connectSubid = GetCurrentSubTransactionId();

    /*
     * Create memory contexts for this procedure
     *
     * XXX it would be better to use PortalContext as the parent context, but
     * we may not be inside a portal (consider deferred-trigger execution).
     * Perhaps CurTransactionContext would do?  For now it doesn't matter
     * because we clean up explicitly in AtEOSubXact_SPI().
     */
    _SPI_current->procCxt = AllocSetContextCreate(TopTransactionContext,
                                                  "SPI Proc",
                                                  ALLOCSET_DEFAULT_MINSIZE,
                                                  ALLOCSET_DEFAULT_INITSIZE,
                                                  ALLOCSET_DEFAULT_MAXSIZE);
    _SPI_current->execCxt = AllocSetContextCreate(TopTransactionContext,
                                                  "SPI Exec",
                                                  ALLOCSET_DEFAULT_MINSIZE,
                                                  ALLOCSET_DEFAULT_INITSIZE,
                                                  ALLOCSET_DEFAULT_MAXSIZE);
    /* ... and switch to procedure's context */
    _SPI_current->savedcxt = MemoryContextSwitchTo(_SPI_current->procCxt);

    return SPI_OK_CONNECT;
}

int
SPI_finish(void)
{
    int         res;

    res = _SPI_begin_call(false);       /* live in procedure memory */
    if (res < 0)
        return res;

    /* Restore memory context as it was before procedure call */
    MemoryContextSwitchTo(_SPI_current->savedcxt);

    /* Release memory used in procedure call */
    MemoryContextDelete(_SPI_current->execCxt);
    _SPI_current->execCxt = NULL;
    MemoryContextDelete(_SPI_current->procCxt);
    _SPI_current->procCxt = NULL;

    /*
     * Reset result variables, especially SPI_tuptable which is probably
     * pointing at a just-deleted tuptable
     */
    SPI_processed = 0;
    SPI_lastoid = InvalidOid;
    SPI_tuptable = NULL;

    /*
     * After _SPI_begin_call _SPI_connected == _SPI_curid. Now we are closing
     * connection to SPI and returning to upper Executor and so _SPI_connected
     * must be equal to _SPI_curid.
     */
    _SPI_connected--;
    _SPI_curid--;
    if (_SPI_connected == -1)
        _SPI_current = NULL;
    else
        _SPI_current = &(_SPI_stack[_SPI_connected]);

    return SPI_OK_FINISH;
}

/*
 * Clean up SPI state at transaction commit or abort.
 */
void
AtEOXact_SPI(bool isCommit)
{
    /*
     * Note that memory contexts belonging to SPI stack entries will be freed
     * automatically, so we can ignore them here.  We just need to restore our
     * static variables to initial state.
     */
    if (isCommit && _SPI_connected != -1)
        ereport(WARNING,
                (errcode(ERRCODE_WARNING),
                 errmsg("transaction left non-empty SPI stack"),
                 errhint("Check for missing \"SPI_finish\" calls.")));

    _SPI_current = _SPI_stack = NULL;
    _SPI_stack_depth = 0;
    _SPI_connected = _SPI_curid = -1;
    SPI_processed = 0;
    SPI_lastoid = InvalidOid;
    SPI_tuptable = NULL;
}

/*
 * Clean up SPI state at subtransaction commit or abort.
 *
 * During commit, there shouldn't be any unclosed entries remaining from
 * the current subtransaction; we emit a warning if any are found.
 */
void
AtEOSubXact_SPI(bool isCommit, SubTransactionId mySubid)
{
    bool        found = false;

    while (_SPI_connected >= 0)
    {
        _SPI_connection *connection = &(_SPI_stack[_SPI_connected]);

        if (connection->connectSubid != mySubid)
            break;              /* couldn't be any underneath it either */

        found = true;

        /*
         * Release procedure memory explicitly (see note in SPI_connect)
         */
        if (connection->execCxt)
        {
            MemoryContextDelete(connection->execCxt);
            connection->execCxt = NULL;
        }
        if (connection->procCxt)
        {
            MemoryContextDelete(connection->procCxt);
            connection->procCxt = NULL;
        }

        /*
         * Pop the stack entry and reset global variables.  Unlike
         * SPI_finish(), we don't risk switching to memory contexts that might
         * be already gone.
         */
        _SPI_connected--;
        _SPI_curid = _SPI_connected;
        if (_SPI_connected == -1)
            _SPI_current = NULL;
        else
            _SPI_current = &(_SPI_stack[_SPI_connected]);
        SPI_processed = 0;
        SPI_lastoid = InvalidOid;
        SPI_tuptable = NULL;
    }

    if (found && isCommit)
        ereport(WARNING,
                (errcode(ERRCODE_WARNING),
                 errmsg("subtransaction left non-empty SPI stack"),
                 errhint("Check for missing \"SPI_finish\" calls.")));

    /*
     * If we are aborting a subtransaction and there is an open SPI context
     * surrounding the subxact, clean up to prevent memory leakage.
     */
    if (_SPI_current && !isCommit)
    {
        /* free Executor memory the same as _SPI_end_call would do */
        MemoryContextResetAndDeleteChildren(_SPI_current->execCxt);
        /* throw away any partially created tuple-table */
        SPI_freetuptable(_SPI_current->tuptable);
        _SPI_current->tuptable = NULL;
    }
}


/* Pushes SPI stack to allow recursive SPI calls */
void
SPI_push(void)
{
    _SPI_curid++;
}

/* Pops SPI stack to allow recursive SPI calls */
void
SPI_pop(void)
{
    _SPI_curid--;
}

/* Conditional push: push only if we're inside a SPI procedure */
bool
SPI_push_conditional(void)
{
    bool        pushed = (_SPI_curid != _SPI_connected);

    if (pushed)
    {
        _SPI_curid++;
        /* We should now be in a state where SPI_connect would succeed */
        Assert(_SPI_curid == _SPI_connected);
    }
    return pushed;
}

/* Conditional pop: pop only if SPI_push_conditional pushed */
void
SPI_pop_conditional(bool pushed)
{
    /* We should be in a state where SPI_connect would succeed */
    Assert(_SPI_curid == _SPI_connected);
    if (pushed)
        _SPI_curid--;
}

/* Restore state of SPI stack after aborting a subtransaction */
void
SPI_restore_connection(void)
{
    Assert(_SPI_connected >= 0);
    _SPI_curid = _SPI_connected - 1;
}

/* Parse, plan, and execute a query string */
int
SPI_execute(const char *src, bool read_only, long tcount)
{
    _SPI_plan   plan;
    int         res;

    if (src == NULL || tcount < 0)
        return SPI_ERROR_ARGUMENT;

    res = _SPI_begin_call(true);
    if (res < 0)
        return res;

    memset(&plan, 0, sizeof(_SPI_plan));
    plan.magic = _SPI_PLAN_MAGIC;
    plan.cursor_options = 0;

    _SPI_prepare_oneshot_plan(src, &plan);

    res = _SPI_execute_plan(&plan, NULL,
                            InvalidSnapshot, InvalidSnapshot,
                            read_only, true, tcount);

    _SPI_end_call(true);
    return res;
}

/* Obsolete version of SPI_execute */
int
SPI_exec(const char *src, long tcount)
{
    return SPI_execute(src, false, tcount);
}

/* Execute a previously prepared plan */
int
SPI_execute_plan(SPIPlanPtr plan, Datum *Values, const char *Nulls,
                 bool read_only, long tcount)
{
    int         res;

    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC || tcount < 0)
        return SPI_ERROR_ARGUMENT;

    if (plan->nargs > 0 && Values == NULL)
        return SPI_ERROR_PARAM;

    res = _SPI_begin_call(true);
    if (res < 0)
        return res;

    res = _SPI_execute_plan(plan,
                            _SPI_convert_params(plan->nargs, plan->argtypes,
                                                Values, Nulls),
                            InvalidSnapshot, InvalidSnapshot,
                            read_only, true, tcount);

    _SPI_end_call(true);
    return res;
}

/* Obsolete version of SPI_execute_plan */
int
SPI_execp(SPIPlanPtr plan, Datum *Values, const char *Nulls, long tcount)
{
    return SPI_execute_plan(plan, Values, Nulls, false, tcount);
}

/* Execute a previously prepared plan */
int
SPI_execute_plan_with_paramlist(SPIPlanPtr plan, ParamListInfo params,
                                bool read_only, long tcount)
{
    int         res;

    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC || tcount < 0)
        return SPI_ERROR_ARGUMENT;

    res = _SPI_begin_call(true);
    if (res < 0)
        return res;

    res = _SPI_execute_plan(plan, params,
                            InvalidSnapshot, InvalidSnapshot,
                            read_only, true, tcount);

    _SPI_end_call(true);
    return res;
}

/*
 * SPI_execute_snapshot -- identical to SPI_execute_plan, except that we allow
 * the caller to specify exactly which snapshots to use, which will be
 * registered here.  Also, the caller may specify that AFTER triggers should be
 * queued as part of the outer query rather than being fired immediately at the
 * end of the command.
 *
 * This is currently not documented in spi.sgml because it is only intended
 * for use by RI triggers.
 *
 * Passing snapshot == InvalidSnapshot will select the normal behavior of
 * fetching a new snapshot for each query.
 */
int
SPI_execute_snapshot(SPIPlanPtr plan,
                     Datum *Values, const char *Nulls,
                     Snapshot snapshot, Snapshot crosscheck_snapshot,
                     bool read_only, bool fire_triggers, long tcount)
{
    int         res;

    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC || tcount < 0)
        return SPI_ERROR_ARGUMENT;

    if (plan->nargs > 0 && Values == NULL)
        return SPI_ERROR_PARAM;

    res = _SPI_begin_call(true);
    if (res < 0)
        return res;

    res = _SPI_execute_plan(plan,
                            _SPI_convert_params(plan->nargs, plan->argtypes,
                                                Values, Nulls),
                            snapshot, crosscheck_snapshot,
                            read_only, fire_triggers, tcount);

    _SPI_end_call(true);
    return res;
}

/*
 * SPI_execute_with_args -- plan and execute a query with supplied arguments
 *
 * This is functionally equivalent to SPI_prepare followed by
 * SPI_execute_plan.
 */
int
SPI_execute_with_args(const char *src,
                      int nargs, Oid *argtypes,
                      Datum *Values, const char *Nulls,
                      bool read_only, long tcount)
{
    int         res;
    _SPI_plan   plan;
    ParamListInfo paramLI;

    if (src == NULL || nargs < 0 || tcount < 0)
        return SPI_ERROR_ARGUMENT;

    if (nargs > 0 && (argtypes == NULL || Values == NULL))
        return SPI_ERROR_PARAM;

    res = _SPI_begin_call(true);
    if (res < 0)
        return res;

    memset(&plan, 0, sizeof(_SPI_plan));
    plan.magic = _SPI_PLAN_MAGIC;
    plan.cursor_options = 0;
    plan.nargs = nargs;
    plan.argtypes = argtypes;
    plan.parserSetup = NULL;
    plan.parserSetupArg = NULL;

    paramLI = _SPI_convert_params(nargs, argtypes,
                                  Values, Nulls);

    _SPI_prepare_oneshot_plan(src, &plan);

    res = _SPI_execute_plan(&plan, paramLI,
                            InvalidSnapshot, InvalidSnapshot,
                            read_only, true, tcount);

    _SPI_end_call(true);
    return res;
}

SPIPlanPtr
SPI_prepare(const char *src, int nargs, Oid *argtypes)
{
    return SPI_prepare_cursor(src, nargs, argtypes, 0);
}

SPIPlanPtr
SPI_prepare_cursor(const char *src, int nargs, Oid *argtypes,
                   int cursorOptions)
{
    _SPI_plan   plan;
    SPIPlanPtr  result;

    if (src == NULL || nargs < 0 || (nargs > 0 && argtypes == NULL))
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return NULL;
    }

    SPI_result = _SPI_begin_call(true);
    if (SPI_result < 0)
        return NULL;

    memset(&plan, 0, sizeof(_SPI_plan));
    plan.magic = _SPI_PLAN_MAGIC;
    plan.cursor_options = cursorOptions;
    plan.nargs = nargs;
    plan.argtypes = argtypes;
    plan.parserSetup = NULL;
    plan.parserSetupArg = NULL;

    _SPI_prepare_plan(src, &plan);

    /* copy plan to procedure context */
    result = _SPI_make_plan_non_temp(&plan);

    _SPI_end_call(true);

    return result;
}

SPIPlanPtr
SPI_prepare_params(const char *src,
                   ParserSetupHook parserSetup,
                   void *parserSetupArg,
                   int cursorOptions)
{
    _SPI_plan   plan;
    SPIPlanPtr  result;

    if (src == NULL)
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return NULL;
    }

    SPI_result = _SPI_begin_call(true);
    if (SPI_result < 0)
        return NULL;

    memset(&plan, 0, sizeof(_SPI_plan));
    plan.magic = _SPI_PLAN_MAGIC;
    plan.cursor_options = cursorOptions;
    plan.nargs = 0;
    plan.argtypes = NULL;
    plan.parserSetup = parserSetup;
    plan.parserSetupArg = parserSetupArg;

    _SPI_prepare_plan(src, &plan);

    /* copy plan to procedure context */
    result = _SPI_make_plan_non_temp(&plan);

    _SPI_end_call(true);

    return result;
}

int
SPI_keepplan(SPIPlanPtr plan)
{
    ListCell   *lc;

    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC ||
        plan->saved || plan->oneshot)
        return SPI_ERROR_ARGUMENT;

    /*
     * Mark it saved, reparent it under CacheMemoryContext, and mark all the
     * component CachedPlanSources as saved.  This sequence cannot fail
     * partway through, so there's no risk of long-term memory leakage.
     */
    plan->saved = true;
    MemoryContextSetParent(plan->plancxt, CacheMemoryContext);

    foreach(lc, plan->plancache_list)
    {
        CachedPlanSource *plansource = (CachedPlanSource *) lfirst(lc);

        SaveCachedPlan(plansource);
    }

    return 0;
}

SPIPlanPtr
SPI_saveplan(SPIPlanPtr plan)
{
    SPIPlanPtr  newplan;

    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC)
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return NULL;
    }

    SPI_result = _SPI_begin_call(false);        /* don't change context */
    if (SPI_result < 0)
        return NULL;

    newplan = _SPI_save_plan(plan);

    SPI_result = _SPI_end_call(false);

    return newplan;
}

int
SPI_freeplan(SPIPlanPtr plan)
{
    ListCell   *lc;

    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC)
        return SPI_ERROR_ARGUMENT;

    /* Release the plancache entries */
    foreach(lc, plan->plancache_list)
    {
        CachedPlanSource *plansource = (CachedPlanSource *) lfirst(lc);

        DropCachedPlan(plansource);
    }

    /* Now get rid of the _SPI_plan and subsidiary data in its plancxt */
    MemoryContextDelete(plan->plancxt);

    return 0;
}

HeapTuple
SPI_copytuple(HeapTuple tuple)
{
    MemoryContext oldcxt = NULL;
    HeapTuple   ctuple;

    if (tuple == NULL)
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return NULL;
    }

    if (_SPI_curid + 1 == _SPI_connected)       /* connected */
    {
        if (_SPI_current != &(_SPI_stack[_SPI_curid + 1]))
            elog(ERROR, "SPI stack corrupted");
        oldcxt = MemoryContextSwitchTo(_SPI_current->savedcxt);
    }

    ctuple = heap_copytuple(tuple);

    if (oldcxt)
        MemoryContextSwitchTo(oldcxt);

    return ctuple;
}

HeapTupleHeader
SPI_returntuple(HeapTuple tuple, TupleDesc tupdesc)
{
    MemoryContext oldcxt = NULL;
    HeapTupleHeader dtup;

    if (tuple == NULL || tupdesc == NULL)
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return NULL;
    }

    /* For RECORD results, make sure a typmod has been assigned */
    if (tupdesc->tdtypeid == RECORDOID &&
        tupdesc->tdtypmod < 0)
        assign_record_type_typmod(tupdesc);

    if (_SPI_curid + 1 == _SPI_connected)       /* connected */
    {
        if (_SPI_current != &(_SPI_stack[_SPI_curid + 1]))
            elog(ERROR, "SPI stack corrupted");
        oldcxt = MemoryContextSwitchTo(_SPI_current->savedcxt);
    }

    dtup = (HeapTupleHeader) palloc(tuple->t_len);
    memcpy((char *) dtup, (char *) tuple->t_data, tuple->t_len);

    HeapTupleHeaderSetDatumLength(dtup, tuple->t_len);
    HeapTupleHeaderSetTypeId(dtup, tupdesc->tdtypeid);
    HeapTupleHeaderSetTypMod(dtup, tupdesc->tdtypmod);

    if (oldcxt)
        MemoryContextSwitchTo(oldcxt);

    return dtup;
}

HeapTuple
SPI_modifytuple(Relation rel, HeapTuple tuple, int natts, int *attnum,
                Datum *Values, const char *Nulls)
{
    MemoryContext oldcxt = NULL;
    HeapTuple   mtuple;
    int         numberOfAttributes;
    Datum      *v;
    bool       *n;
    int         i;

    if (rel == NULL || tuple == NULL || natts < 0 || attnum == NULL || Values == NULL)
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return NULL;
    }

    if (_SPI_curid + 1 == _SPI_connected)       /* connected */
    {
        if (_SPI_current != &(_SPI_stack[_SPI_curid + 1]))
            elog(ERROR, "SPI stack corrupted");
        oldcxt = MemoryContextSwitchTo(_SPI_current->savedcxt);
    }
    SPI_result = 0;
    numberOfAttributes = rel->rd_att->natts;
    v = (Datum *) palloc(numberOfAttributes * sizeof(Datum));
    n = (bool *) palloc(numberOfAttributes * sizeof(bool));

    /* fetch old values and nulls */
    heap_deform_tuple(tuple, rel->rd_att, v, n);

    /* replace values and nulls */
    for (i = 0; i < natts; i++)
    {
        if (attnum[i] <= 0 || attnum[i] > numberOfAttributes)
            break;
        v[attnum[i] - 1] = Values[i];
        n[attnum[i] - 1] = (Nulls && Nulls[i] == 'n') ? true : false;
    }

    if (i == natts)             /* no errors in *attnum */
    {
        mtuple = heap_form_tuple(rel->rd_att, v, n);

        /*
         * copy the identification info of the old tuple: t_ctid, t_self, and
         * OID (if any)
         */
        mtuple->t_data->t_ctid = tuple->t_data->t_ctid;
        mtuple->t_self = tuple->t_self;
        mtuple->t_tableOid = tuple->t_tableOid;
        if (rel->rd_att->tdhasoid)
            HeapTupleSetOid(mtuple, HeapTupleGetOid(tuple));
    }
    else
    {
        mtuple = NULL;
        SPI_result = SPI_ERROR_NOATTRIBUTE;
    }

    pfree(v);
    pfree(n);

    if (oldcxt)
        MemoryContextSwitchTo(oldcxt);

    return mtuple;
}

int
SPI_fnumber(TupleDesc tupdesc, const char *fname)
{
    int         res;
    Form_pg_attribute sysatt;

    for (res = 0; res < tupdesc->natts; res++)
    {
        if (namestrcmp(&tupdesc->attrs[res]->attname, fname) == 0)
            return res + 1;
    }

    sysatt = SystemAttributeByName(fname, true /* "oid" will be accepted */ );
    if (sysatt != NULL)
        return sysatt->attnum;

    /* SPI_ERROR_NOATTRIBUTE is different from all sys column numbers */
    return SPI_ERROR_NOATTRIBUTE;
}

char *
SPI_fname(TupleDesc tupdesc, int fnumber)
{
    Form_pg_attribute att;

    SPI_result = 0;

    if (fnumber > tupdesc->natts || fnumber == 0 ||
        fnumber <= FirstLowInvalidHeapAttributeNumber)
    {
        SPI_result = SPI_ERROR_NOATTRIBUTE;
        return NULL;
    }

    if (fnumber > 0)
        att = tupdesc->attrs[fnumber - 1];
    else
        att = SystemAttributeDefinition(fnumber, true);

    return pstrdup(NameStr(att->attname));
}

char *
SPI_getvalue(HeapTuple tuple, TupleDesc tupdesc, int fnumber)
{
    char       *result;
    Datum       origval,
                val;
    bool        isnull;
    Oid         typoid,
                foutoid;
    bool        typisvarlena;

    SPI_result = 0;

    if (fnumber > tupdesc->natts || fnumber == 0 ||
        fnumber <= FirstLowInvalidHeapAttributeNumber)
    {
        SPI_result = SPI_ERROR_NOATTRIBUTE;
        return NULL;
    }

    origval = heap_getattr(tuple, fnumber, tupdesc, &isnull);
    if (isnull)
        return NULL;

    if (fnumber > 0)
        typoid = tupdesc->attrs[fnumber - 1]->atttypid;
    else
        typoid = (SystemAttributeDefinition(fnumber, true))->atttypid;

    getTypeOutputInfo(typoid, &foutoid, &typisvarlena);

    /*
     * If we have a toasted datum, forcibly detoast it here to avoid memory
     * leakage inside the type's output routine.
     */
    if (typisvarlena)
        val = PointerGetDatum(PG_DETOAST_DATUM(origval));
    else
        val = origval;

    result = OidOutputFunctionCall(foutoid, val);

    /* Clean up detoasted copy, if any */
    if (val != origval)
        pfree(DatumGetPointer(val));

    return result;
}

Datum
SPI_getbinval(HeapTuple tuple, TupleDesc tupdesc, int fnumber, bool *isnull)
{
    SPI_result = 0;

    if (fnumber > tupdesc->natts || fnumber == 0 ||
        fnumber <= FirstLowInvalidHeapAttributeNumber)
    {
        SPI_result = SPI_ERROR_NOATTRIBUTE;
        *isnull = true;
        return (Datum) NULL;
    }

    return heap_getattr(tuple, fnumber, tupdesc, isnull);
}

char *
SPI_gettype(TupleDesc tupdesc, int fnumber)
{
    Oid         typoid;
    HeapTuple   typeTuple;
    char       *result;

    SPI_result = 0;

    if (fnumber > tupdesc->natts || fnumber == 0 ||
        fnumber <= FirstLowInvalidHeapAttributeNumber)
    {
        SPI_result = SPI_ERROR_NOATTRIBUTE;
        return NULL;
    }

    if (fnumber > 0)
        typoid = tupdesc->attrs[fnumber - 1]->atttypid;
    else
        typoid = (SystemAttributeDefinition(fnumber, true))->atttypid;

    typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typoid));

    if (!HeapTupleIsValid(typeTuple))
    {
        SPI_result = SPI_ERROR_TYPUNKNOWN;
        return NULL;
    }

    result = pstrdup(NameStr(((Form_pg_type) GETSTRUCT(typeTuple))->typname));
    ReleaseSysCache(typeTuple);
    return result;
}

Oid
SPI_gettypeid(TupleDesc tupdesc, int fnumber)
{
    SPI_result = 0;

    if (fnumber > tupdesc->natts || fnumber == 0 ||
        fnumber <= FirstLowInvalidHeapAttributeNumber)
    {
        SPI_result = SPI_ERROR_NOATTRIBUTE;
        return InvalidOid;
    }

    if (fnumber > 0)
        return tupdesc->attrs[fnumber - 1]->atttypid;
    else
        return (SystemAttributeDefinition(fnumber, true))->atttypid;
}

char *
SPI_getrelname(Relation rel)
{
    return pstrdup(RelationGetRelationName(rel));
}

char *
SPI_getnspname(Relation rel)
{
    return get_namespace_name(RelationGetNamespace(rel));
}

void *
SPI_palloc(Size size)
{
    MemoryContext oldcxt = NULL;
    void       *pointer;

    if (_SPI_curid + 1 == _SPI_connected)       /* connected */
    {
        if (_SPI_current != &(_SPI_stack[_SPI_curid + 1]))
            elog(ERROR, "SPI stack corrupted");
        oldcxt = MemoryContextSwitchTo(_SPI_current->savedcxt);
    }

    pointer = palloc(size);

    if (oldcxt)
        MemoryContextSwitchTo(oldcxt);

    return pointer;
}

void *
SPI_repalloc(void *pointer, Size size)
{
    /* No longer need to worry which context chunk was in... */
    return repalloc(pointer, size);
}

void
SPI_pfree(void *pointer)
{
    /* No longer need to worry which context chunk was in... */
    pfree(pointer);
}

void
SPI_freetuple(HeapTuple tuple)
{
    /* No longer need to worry which context tuple was in... */
    heap_freetuple(tuple);
}

void
SPI_freetuptable(SPITupleTable *tuptable)
{
    if (tuptable != NULL)
        MemoryContextDelete(tuptable->tuptabcxt);
}


/*
 * SPI_cursor_open()
 *
 *  Open a prepared SPI plan as a portal
 */
Portal
SPI_cursor_open(const char *name, SPIPlanPtr plan,
                Datum *Values, const char *Nulls,
                bool read_only)
{
    Portal      portal;
    ParamListInfo paramLI;

    /* build transient ParamListInfo in caller's context */
    paramLI = _SPI_convert_params(plan->nargs, plan->argtypes,
                                  Values, Nulls);

    portal = SPI_cursor_open_internal(name, plan, paramLI, read_only);

    /* done with the transient ParamListInfo */
    if (paramLI)
        pfree(paramLI);

    return portal;
}


/*
 * SPI_cursor_open_with_args()
 *
 * Parse and plan a query and open it as a portal.
 */
Portal
SPI_cursor_open_with_args(const char *name,
                          const char *src,
                          int nargs, Oid *argtypes,
                          Datum *Values, const char *Nulls,
                          bool read_only, int cursorOptions)
{
    Portal      result;
    _SPI_plan   plan;
    ParamListInfo paramLI;

    if (src == NULL || nargs < 0)
        elog(ERROR, "SPI_cursor_open_with_args called with invalid arguments");

    if (nargs > 0 && (argtypes == NULL || Values == NULL))
        elog(ERROR, "SPI_cursor_open_with_args called with missing parameters");

    SPI_result = _SPI_begin_call(true);
    if (SPI_result < 0)
        elog(ERROR, "SPI_cursor_open_with_args called while not connected");

    memset(&plan, 0, sizeof(_SPI_plan));
    plan.magic = _SPI_PLAN_MAGIC;
    plan.cursor_options = cursorOptions;
    plan.nargs = nargs;
    plan.argtypes = argtypes;
    plan.parserSetup = NULL;
    plan.parserSetupArg = NULL;

    /* build transient ParamListInfo in executor context */
    paramLI = _SPI_convert_params(nargs, argtypes,
                                  Values, Nulls);

    _SPI_prepare_plan(src, &plan);

    /* We needn't copy the plan; SPI_cursor_open_internal will do so */

    /* Adjust stack so that SPI_cursor_open_internal doesn't complain */
    _SPI_curid--;

    result = SPI_cursor_open_internal(name, &plan, paramLI, read_only);

    /* And clean up */
    _SPI_curid++;
    _SPI_end_call(true);

    return result;
}


/*
 * SPI_cursor_open_with_paramlist()
 *
 *  Same as SPI_cursor_open except that parameters (if any) are passed
 *  as a ParamListInfo, which supports dynamic parameter set determination
 */
Portal
SPI_cursor_open_with_paramlist(const char *name, SPIPlanPtr plan,
                               ParamListInfo params, bool read_only)
{
    return SPI_cursor_open_internal(name, plan, params, read_only);
}


/*
 * SPI_cursor_open_internal()
 *
 *  Common code for SPI_cursor_open variants
 */
static Portal
SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
                         ParamListInfo paramLI, bool read_only)
{
    CachedPlanSource *plansource;
    CachedPlan *cplan;
    List       *stmt_list;
    char       *query_string;
    Snapshot    snapshot;
    MemoryContext oldcontext;
    Portal      portal;
    ErrorContextCallback spierrcontext;

    /*
     * Check that the plan is something the Portal code will special-case as
     * returning one tupleset.
     */
    if (!SPI_is_cursor_plan(plan))
    {
        /* try to give a good error message */
        if (list_length(plan->plancache_list) != 1)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_CURSOR_DEFINITION),
                     errmsg("cannot open multi-query plan as cursor")));
        plansource = (CachedPlanSource *) linitial(plan->plancache_list);
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_CURSOR_DEFINITION),
        /* translator: %s is name of a SQL command, eg INSERT */
                 errmsg("cannot open %s query as cursor",
                        plansource->commandTag)));
    }

    Assert(list_length(plan->plancache_list) == 1);
    plansource = (CachedPlanSource *) linitial(plan->plancache_list);

    /* Push the SPI stack */
    if (_SPI_begin_call(true) < 0)
        elog(ERROR, "SPI_cursor_open called while not connected");

    /* Reset SPI result (note we deliberately don't touch lastoid) */
    SPI_processed = 0;
    SPI_tuptable = NULL;
    _SPI_current->processed = 0;
    _SPI_current->tuptable = NULL;

    /* Create the portal */
    if (name == NULL || name[0] == '\0')
    {
        /* Use a random nonconflicting name */
        portal = CreateNewPortal();
    }
    else
    {
        /* In this path, error if portal of same name already exists */
        portal = CreatePortal(name, false, false);
    }

    /* Copy the plan's query string into the portal */
    query_string = MemoryContextStrdup(PortalGetHeapMemory(portal),
                                       plansource->query_string);

    /*
     * Setup error traceback support for ereport(), in case GetCachedPlan
     * throws an error.
     */
    spierrcontext.callback = _SPI_error_callback;
    spierrcontext.arg = (void *) plansource->query_string;
    spierrcontext.previous = error_context_stack;
    error_context_stack = &spierrcontext;

    /*
     * Note: for a saved plan, we mustn't have any failure occur between
     * GetCachedPlan and PortalDefineQuery; that would result in leaking our
     * plancache refcount.
     */

    /* Replan if needed, and increment plan refcount for portal */
    cplan = GetCachedPlan(plansource, paramLI, false);
    stmt_list = cplan->stmt_list;

    /* Pop the error context stack */
    error_context_stack = spierrcontext.previous;

    if (!plan->saved)
    {
        /*
         * We don't want the portal to depend on an unsaved CachedPlanSource,
         * so must copy the plan into the portal's context.  An error here
         * will result in leaking our refcount on the plan, but it doesn't
         * matter because the plan is unsaved and hence transient anyway.
         */
        oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
        stmt_list = copyObject(stmt_list);
        MemoryContextSwitchTo(oldcontext);
        ReleaseCachedPlan(cplan, false);
        cplan = NULL;           /* portal shouldn't depend on cplan */
    }

    /*
     * Set up the portal.
     */
    PortalDefineQuery(portal,
                      NULL,     /* no statement name */
                      query_string,
                      plansource->commandTag,
                      stmt_list,
                      cplan);

    /*
     * Set up options for portal.  Default SCROLL type is chosen the same way
     * as PerformCursorOpen does it.
     */
    portal->cursorOptions = plan->cursor_options;
    if (!(portal->cursorOptions & (CURSOR_OPT_SCROLL | CURSOR_OPT_NO_SCROLL)))
    {
        if (list_length(stmt_list) == 1 &&
            IsA((Node *) linitial(stmt_list), PlannedStmt) &&
            ((PlannedStmt *) linitial(stmt_list))->rowMarks == NIL &&
            ExecSupportsBackwardScan(((PlannedStmt *) linitial(stmt_list))->planTree))
            portal->cursorOptions |= CURSOR_OPT_SCROLL;
        else
            portal->cursorOptions |= CURSOR_OPT_NO_SCROLL;
    }

    /*
     * Disallow SCROLL with SELECT FOR UPDATE.  This is not redundant with the
     * check in transformDeclareCursorStmt because the cursor options might
     * not have come through there.
     */
    if (portal->cursorOptions & CURSOR_OPT_SCROLL)
    {
        if (list_length(stmt_list) == 1 &&
            IsA((Node *) linitial(stmt_list), PlannedStmt) &&
            ((PlannedStmt *) linitial(stmt_list))->rowMarks != NIL)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("DECLARE SCROLL CURSOR ... FOR UPDATE/SHARE is not supported"),
                     errdetail("Scrollable cursors must be READ ONLY.")));
    }

    /*
     * If told to be read-only, we'd better check for read-only queries. This
     * can't be done earlier because we need to look at the finished, planned
     * queries.  (In particular, we don't want to do it between GetCachedPlan
     * and PortalDefineQuery, because throwing an error between those steps
     * would result in leaking our plancache refcount.)
     */
    if (read_only)
    {
        ListCell   *lc;

        foreach(lc, stmt_list)
        {
            Node       *pstmt = (Node *) lfirst(lc);

            if (!CommandIsReadOnly(pstmt))
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                /* translator: %s is a SQL statement name */
                       errmsg("%s is not allowed in a non-volatile function",
                              CreateCommandTag(pstmt))));
        }
    }

    /* Set up the snapshot to use. */
    if (read_only)
        snapshot = GetActiveSnapshot();
    else
    {
        CommandCounterIncrement();
        snapshot = GetTransactionSnapshot();
    }

    /*
     * If the plan has parameters, copy them into the portal.  Note that this
     * must be done after revalidating the plan, because in dynamic parameter
     * cases the set of parameters could have changed during re-parsing.
     */
    if (paramLI)
    {
        oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
        paramLI = copyParamList(paramLI);
        MemoryContextSwitchTo(oldcontext);
    }

    /*
     * Start portal execution.
     */
    PortalStart(portal, paramLI, 0, snapshot);

    Assert(portal->strategy != PORTAL_MULTI_QUERY);

    /* Pop the SPI stack */
    _SPI_end_call(true);

    /* Return the created portal */
    return portal;
}


/*
 * SPI_cursor_find()
 *
 *  Find the portal of an existing open cursor
 */
Portal
SPI_cursor_find(const char *name)
{
    return GetPortalByName(name);
}


/*
 * SPI_cursor_fetch()
 *
 *  Fetch rows in a cursor
 */
void
SPI_cursor_fetch(Portal portal, bool forward, long count)
{
    _SPI_cursor_operation(portal,
                          forward ? FETCH_FORWARD : FETCH_BACKWARD, count,
                          CreateDestReceiver(DestSPI));
    /* we know that the DestSPI receiver doesn't need a destroy call */
}


/*
 * SPI_cursor_move()
 *
 *  Move in a cursor
 */
void
SPI_cursor_move(Portal portal, bool forward, long count)
{
    _SPI_cursor_operation(portal,
                          forward ? FETCH_FORWARD : FETCH_BACKWARD, count,
                          None_Receiver);
}


/*
 * SPI_scroll_cursor_fetch()
 *
 *  Fetch rows in a scrollable cursor
 */
void
SPI_scroll_cursor_fetch(Portal portal, FetchDirection direction, long count)
{
    _SPI_cursor_operation(portal,
                          direction, count,
                          CreateDestReceiver(DestSPI));
    /* we know that the DestSPI receiver doesn't need a destroy call */
}


/*
 * SPI_scroll_cursor_move()
 *
 *  Move in a scrollable cursor
 */
void
SPI_scroll_cursor_move(Portal portal, FetchDirection direction, long count)
{
    _SPI_cursor_operation(portal, direction, count, None_Receiver);
}


/*
 * SPI_cursor_close()
 *
 *  Close a cursor
 */
void
SPI_cursor_close(Portal portal)
{
    if (!PortalIsValid(portal))
        elog(ERROR, "invalid portal in SPI cursor operation");

    PortalDrop(portal, false);
}

/*
 * Returns the Oid representing the type id for argument at argIndex. First
 * parameter is at index zero.
 */
Oid
SPI_getargtypeid(SPIPlanPtr plan, int argIndex)
{
    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC ||
        argIndex < 0 || argIndex >= plan->nargs)
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return InvalidOid;
    }
    return plan->argtypes[argIndex];
}

/*
 * Returns the number of arguments for the prepared plan.
 */
int
SPI_getargcount(SPIPlanPtr plan)
{
    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC)
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return -1;
    }
    return plan->nargs;
}

/*
 * Returns true if the plan contains exactly one command
 * and that command returns tuples to the caller (eg, SELECT or
 * INSERT ... RETURNING, but not SELECT ... INTO). In essence,
 * the result indicates if the command can be used with SPI_cursor_open
 *
 * Parameters
 *    plan: A plan previously prepared using SPI_prepare
 */
bool
SPI_is_cursor_plan(SPIPlanPtr plan)
{
    CachedPlanSource *plansource;

    if (plan == NULL || plan->magic != _SPI_PLAN_MAGIC)
    {
        SPI_result = SPI_ERROR_ARGUMENT;
        return false;
    }

    if (list_length(plan->plancache_list) != 1)
    {
        SPI_result = 0;
        return false;           /* not exactly 1 pre-rewrite command */
    }
    plansource = (CachedPlanSource *) linitial(plan->plancache_list);

    /*
     * We used to force revalidation of the cached plan here, but that seems
     * unnecessary: invalidation could mean a change in the rowtype of the
     * tuples returned by a plan, but not whether it returns tuples at all.
     */
    SPI_result = 0;

    /* Does it return tuples? */
    if (plansource->resultDesc)
        return true;

    return false;
}

/*
 * SPI_plan_is_valid --- test whether a SPI plan is currently valid
 * (that is, not marked as being in need of revalidation).
 *
 * See notes for CachedPlanIsValid before using this.
 */
bool
SPI_plan_is_valid(SPIPlanPtr plan)
{
    ListCell   *lc;

    Assert(plan->magic == _SPI_PLAN_MAGIC);

    foreach(lc, plan->plancache_list)
    {
        CachedPlanSource *plansource = (CachedPlanSource *) lfirst(lc);

        if (!CachedPlanIsValid(plansource))
            return false;
    }
    return true;
}

/*
 * SPI_result_code_string --- convert any SPI return code to a string
 *
 * This is often useful in error messages.  Most callers will probably
 * only pass negative (error-case) codes, but for generality we recognize
 * the success codes too.
 */
const char *
SPI_result_code_string(int code)
{
    static char buf[64];

    switch (code)
    {
        case SPI_ERROR_CONNECT:
            return "SPI_ERROR_CONNECT";
        case SPI_ERROR_COPY:
            return "SPI_ERROR_COPY";
        case SPI_ERROR_OPUNKNOWN:
            return "SPI_ERROR_OPUNKNOWN";
        case SPI_ERROR_UNCONNECTED:
            return "SPI_ERROR_UNCONNECTED";
        case SPI_ERROR_ARGUMENT:
            return "SPI_ERROR_ARGUMENT";
        case SPI_ERROR_PARAM:
            return "SPI_ERROR_PARAM";
        case SPI_ERROR_TRANSACTION:
            return "SPI_ERROR_TRANSACTION";
        case SPI_ERROR_NOATTRIBUTE:
            return "SPI_ERROR_NOATTRIBUTE";
        case SPI_ERROR_NOOUTFUNC:
            return "SPI_ERROR_NOOUTFUNC";
        case SPI_ERROR_TYPUNKNOWN:
            return "SPI_ERROR_TYPUNKNOWN";
        case SPI_OK_CONNECT:
            return "SPI_OK_CONNECT";
        case SPI_OK_FINISH:
            return "SPI_OK_FINISH";
        case SPI_OK_FETCH:
            return "SPI_OK_FETCH";
        case SPI_OK_UTILITY:
            return "SPI_OK_UTILITY";
        case SPI_OK_SELECT:
            return "SPI_OK_SELECT";
        case SPI_OK_SELINTO:
            return "SPI_OK_SELINTO";
        case SPI_OK_INSERT:
            return "SPI_OK_INSERT";
        case SPI_OK_DELETE:
            return "SPI_OK_DELETE";
        case SPI_OK_UPDATE:
            return "SPI_OK_UPDATE";
        case SPI_OK_CURSOR:
            return "SPI_OK_CURSOR";
        case SPI_OK_INSERT_RETURNING:
            return "SPI_OK_INSERT_RETURNING";
        case SPI_OK_DELETE_RETURNING:
            return "SPI_OK_DELETE_RETURNING";
        case SPI_OK_UPDATE_RETURNING:
            return "SPI_OK_UPDATE_RETURNING";
        case SPI_OK_REWRITTEN:
            return "SPI_OK_REWRITTEN";
    }
    /* Unrecognized code ... return something useful ... */
    sprintf(buf, "Unrecognized SPI code %d", code);
    return buf;
}

/*
 * SPI_plan_get_plan_sources --- get a SPI plan's underlying list of
 * CachedPlanSources.
 *
 * This is exported so that pl/pgsql can use it (this beats letting pl/pgsql
 * look directly into the SPIPlan for itself).  It's not documented in
 * spi.sgml because we'd just as soon not have too many places using this.
 */
List *
SPI_plan_get_plan_sources(SPIPlanPtr plan)
{
    Assert(plan->magic == _SPI_PLAN_MAGIC);
    return plan->plancache_list;
}

/*
 * SPI_plan_get_cached_plan --- get a SPI plan's generic CachedPlan,
 * if the SPI plan contains exactly one CachedPlanSource.  If not,
 * return NULL.  Caller is responsible for doing ReleaseCachedPlan().
 *
 * This is exported so that pl/pgsql can use it (this beats letting pl/pgsql
 * look directly into the SPIPlan for itself).  It's not documented in
 * spi.sgml because we'd just as soon not have too many places using this.
 */
CachedPlan *
SPI_plan_get_cached_plan(SPIPlanPtr plan)
{
    CachedPlanSource *plansource;
    CachedPlan *cplan;
    ErrorContextCallback spierrcontext;

    Assert(plan->magic == _SPI_PLAN_MAGIC);

    /* Can't support one-shot plans here */
    if (plan->oneshot)
        return NULL;

    /* Must have exactly one CachedPlanSource */
    if (list_length(plan->plancache_list) != 1)
        return NULL;
    plansource = (CachedPlanSource *) linitial(plan->plancache_list);

    /* Setup error traceback support for ereport() */
    spierrcontext.callback = _SPI_error_callback;
    spierrcontext.arg = (void *) plansource->query_string;
    spierrcontext.previous = error_context_stack;
    error_context_stack = &spierrcontext;

    /* Get the generic plan for the query */
    cplan = GetCachedPlan(plansource, NULL, plan->saved);
    Assert(cplan == plansource->gplan);

    /* Pop the error context stack */
    error_context_stack = spierrcontext.previous;

    return cplan;
}


/* =================== private functions =================== */

/*
 * spi_dest_startup
 *      Initialize to receive tuples from Executor into SPITupleTable
 *      of current SPI procedure
 */
void
spi_dest_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
{
    SPITupleTable *tuptable;
    MemoryContext oldcxt;
    MemoryContext tuptabcxt;

    /*
     * When called by Executor _SPI_curid expected to be equal to
     * _SPI_connected
     */
    if (_SPI_curid != _SPI_connected || _SPI_connected < 0)
        elog(ERROR, "improper call to spi_dest_startup");
    if (_SPI_current != &(_SPI_stack[_SPI_curid]))
        elog(ERROR, "SPI stack corrupted");

    if (_SPI_current->tuptable != NULL)
        elog(ERROR, "improper call to spi_dest_startup");

    oldcxt = _SPI_procmem();    /* switch to procedure memory context */

    tuptabcxt = AllocSetContextCreate(CurrentMemoryContext,
                                      "SPI TupTable",
                                      ALLOCSET_DEFAULT_MINSIZE,
                                      ALLOCSET_DEFAULT_INITSIZE,
                                      ALLOCSET_DEFAULT_MAXSIZE);
    MemoryContextSwitchTo(tuptabcxt);

    _SPI_current->tuptable = tuptable = (SPITupleTable *)
        palloc(sizeof(SPITupleTable));
    tuptable->tuptabcxt = tuptabcxt;
    tuptable->alloced = tuptable->free = 128;
    tuptable->vals = (HeapTuple *) palloc(tuptable->alloced * sizeof(HeapTuple));
    tuptable->tupdesc = CreateTupleDescCopy(typeinfo);

    MemoryContextSwitchTo(oldcxt);
}

/*
 * spi_printtup
 *      store tuple retrieved by Executor into SPITupleTable
 *      of current SPI procedure
 */
void
spi_printtup(TupleTableSlot *slot, DestReceiver *self)
{
    SPITupleTable *tuptable;
    MemoryContext oldcxt;

    /*
     * When called by Executor _SPI_curid expected to be equal to
     * _SPI_connected
     */
    if (_SPI_curid != _SPI_connected || _SPI_connected < 0)
        elog(ERROR, "improper call to spi_printtup");
    if (_SPI_current != &(_SPI_stack[_SPI_curid]))
        elog(ERROR, "SPI stack corrupted");

    tuptable = _SPI_current->tuptable;
    if (tuptable == NULL)
        elog(ERROR, "improper call to spi_printtup");

    oldcxt = MemoryContextSwitchTo(tuptable->tuptabcxt);

    if (tuptable->free == 0)
    {
        tuptable->free = 256;
        tuptable->alloced += tuptable->free;
        tuptable->vals = (HeapTuple *) repalloc(tuptable->vals,
                                      tuptable->alloced * sizeof(HeapTuple));
    }

    tuptable->vals[tuptable->alloced - tuptable->free] =
        ExecCopySlotTuple(slot);
    (tuptable->free)--;

    MemoryContextSwitchTo(oldcxt);
}

/*
 * Static functions
 */

/*
 * Parse and analyze a querystring.
 *
 * At entry, plan->argtypes and plan->nargs (or alternatively plan->parserSetup
 * and plan->parserSetupArg) must be valid, as must plan->cursor_options.
 *
 * Results are stored into *plan (specifically, plan->plancache_list).
 * Note that the result data is all in CurrentMemoryContext or child contexts
 * thereof; in practice this means it is in the SPI executor context, and
 * what we are creating is a "temporary" SPIPlan.  Cruft generated during
 * parsing is also left in CurrentMemoryContext.
 */
static void
_SPI_prepare_plan(const char *src, SPIPlanPtr plan)
{
    List       *raw_parsetree_list;
    List       *plancache_list;
    ListCell   *list_item;
    ErrorContextCallback spierrcontext;

    /*
     * Setup error traceback support for ereport()
     */
    spierrcontext.callback = _SPI_error_callback;
    spierrcontext.arg = (void *) src;
    spierrcontext.previous = error_context_stack;
    error_context_stack = &spierrcontext;

    /*
     * Parse the request string into a list of raw parse trees.
     */
    raw_parsetree_list = pg_parse_query(src);

    /*
     * Do parse analysis and rule rewrite for each raw parsetree, storing the
     * results into unsaved plancache entries.
     */
    plancache_list = NIL;

    foreach(list_item, raw_parsetree_list)
    {
        Node       *parsetree = (Node *) lfirst(list_item);
        List       *stmt_list;
        CachedPlanSource *plansource;

        /*
         * Create the CachedPlanSource before we do parse analysis, since it
         * needs to see the unmodified raw parse tree.
         */
        plansource = CreateCachedPlan(parsetree,
                                      src,
                                      CreateCommandTag(parsetree));

        /*
         * Parameter datatypes are driven by parserSetup hook if provided,
         * otherwise we use the fixed parameter list.
         */
        if (plan->parserSetup != NULL)
        {
            Assert(plan->nargs == 0);
            stmt_list = pg_analyze_and_rewrite_params(parsetree,
                                                      src,
                                                      plan->parserSetup,
                                                      plan->parserSetupArg);
        }
        else
        {
            stmt_list = pg_analyze_and_rewrite(parsetree,
                                               src,
                                               plan->argtypes,
                                               plan->nargs);
        }

        /* Finish filling in the CachedPlanSource */
        CompleteCachedPlan(plansource,
                           stmt_list,
                           NULL,
                           plan->argtypes,
                           plan->nargs,
                           plan->parserSetup,
                           plan->parserSetupArg,
                           plan->cursor_options,
                           false);      /* not fixed result */

        plancache_list = lappend(plancache_list, plansource);
    }

    plan->plancache_list = plancache_list;
    plan->oneshot = false;

    /*
     * Pop the error context stack
     */
    error_context_stack = spierrcontext.previous;
}

/*
 * Parse, but don't analyze, a querystring.
 *
 * This is a stripped-down version of _SPI_prepare_plan that only does the
 * initial raw parsing.  It creates "one shot" CachedPlanSources
 * that still require parse analysis before execution is possible.
 *
 * The advantage of using the "one shot" form of CachedPlanSource is that
 * we eliminate data copying and invalidation overhead.  Postponing parse
 * analysis also prevents issues if some of the raw parsetrees are DDL
 * commands that affect validity of later parsetrees.  Both of these
 * attributes are good things for SPI_execute() and similar cases.
 *
 * Results are stored into *plan (specifically, plan->plancache_list).
 * Note that the result data is all in CurrentMemoryContext or child contexts
 * thereof; in practice this means it is in the SPI executor context, and
 * what we are creating is a "temporary" SPIPlan.  Cruft generated during
 * parsing is also left in CurrentMemoryContext.
 */
static void
_SPI_prepare_oneshot_plan(const char *src, SPIPlanPtr plan)
{
    List       *raw_parsetree_list;
    List       *plancache_list;
    ListCell   *list_item;
    ErrorContextCallback spierrcontext;

    /*
     * Setup error traceback support for ereport()
     */
    spierrcontext.callback = _SPI_error_callback;
    spierrcontext.arg = (void *) src;
    spierrcontext.previous = error_context_stack;
    error_context_stack = &spierrcontext;

    /*
     * Parse the request string into a list of raw parse trees.
     */
    raw_parsetree_list = pg_parse_query(src);

    /*
     * Construct plancache entries, but don't do parse analysis yet.
     */
    plancache_list = NIL;

    foreach(list_item, raw_parsetree_list)
    {
        Node       *parsetree = (Node *) lfirst(list_item);
        CachedPlanSource *plansource;

        plansource = CreateOneShotCachedPlan(parsetree,
                                             src,
                                             CreateCommandTag(parsetree));

        plancache_list = lappend(plancache_list, plansource);
    }

    plan->plancache_list = plancache_list;
    plan->oneshot = true;

    /*
     * Pop the error context stack
     */
    error_context_stack = spierrcontext.previous;
}

/*
 * Execute the given plan with the given parameter values
 *
 * snapshot: query snapshot to use, or InvalidSnapshot for the normal
 *      behavior of taking a new snapshot for each query.
 * crosscheck_snapshot: for RI use, all others pass InvalidSnapshot
 * read_only: TRUE for read-only execution (no CommandCounterIncrement)
 * fire_triggers: TRUE to fire AFTER triggers at end of query (normal case);
 *      FALSE means any AFTER triggers are postponed to end of outer query
 * tcount: execution tuple-count limit, or 0 for none
 */
static int
_SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
                  Snapshot snapshot, Snapshot crosscheck_snapshot,
                  bool read_only, bool fire_triggers, long tcount)
{
    int         my_res = 0;
    uint32      my_processed = 0;
    Oid         my_lastoid = InvalidOid;
    SPITupleTable *my_tuptable = NULL;
    int         res = 0;
    bool        pushed_active_snap = false;
    ErrorContextCallback spierrcontext;
    CachedPlan *cplan = NULL;
    ListCell   *lc1;

    /*
     * Setup error traceback support for ereport()
     */
    spierrcontext.callback = _SPI_error_callback;
    spierrcontext.arg = NULL;   /* we'll fill this below */
    spierrcontext.previous = error_context_stack;
    error_context_stack = &spierrcontext;

    /*
     * We support four distinct snapshot management behaviors:
     *
     * snapshot != InvalidSnapshot, read_only = true: use exactly the given
     * snapshot.
     *
     * snapshot != InvalidSnapshot, read_only = false: use the given snapshot,
     * modified by advancing its command ID before each querytree.
     *
     * snapshot == InvalidSnapshot, read_only = true: use the entry-time
     * ActiveSnapshot, if any (if there isn't one, we run with no snapshot).
     *
     * snapshot == InvalidSnapshot, read_only = false: take a full new
     * snapshot for each user command, and advance its command ID before each
     * querytree within the command.
     *
     * In the first two cases, we can just push the snap onto the stack once
     * for the whole plan list.
     */
    if (snapshot != InvalidSnapshot)
    {
        if (read_only)
        {
            PushActiveSnapshot(snapshot);
            pushed_active_snap = true;
        }
        else
        {
            /* Make sure we have a private copy of the snapshot to modify */
            PushCopiedSnapshot(snapshot);
            pushed_active_snap = true;
        }
    }

    foreach(lc1, plan->plancache_list)
    {
        CachedPlanSource *plansource = (CachedPlanSource *) lfirst(lc1);
        List       *stmt_list;
        ListCell   *lc2;

        spierrcontext.arg = (void *) plansource->query_string;

        /*
         * If this is a one-shot plan, we still need to do parse analysis.
         */
        if (plan->oneshot)
        {
            Node       *parsetree = plansource->raw_parse_tree;
            const char *src = plansource->query_string;
            List       *stmt_list;

            /*
             * Parameter datatypes are driven by parserSetup hook if provided,
             * otherwise we use the fixed parameter list.
             */
            if (plan->parserSetup != NULL)
            {
                Assert(plan->nargs == 0);
                stmt_list = pg_analyze_and_rewrite_params(parsetree,
                                                          src,
                                                          plan->parserSetup,
                                                          plan->parserSetupArg);
            }
            else
            {
                stmt_list = pg_analyze_and_rewrite(parsetree,
                                                   src,
                                                   plan->argtypes,
                                                   plan->nargs);
            }

            /* Finish filling in the CachedPlanSource */
            CompleteCachedPlan(plansource,
                               stmt_list,
                               NULL,
                               plan->argtypes,
                               plan->nargs,
                               plan->parserSetup,
                               plan->parserSetupArg,
                               plan->cursor_options,
                               false);      /* not fixed result */
        }

        /*
         * Replan if needed, and increment plan refcount.  If it's a saved
         * plan, the refcount must be backed by the CurrentResourceOwner.
         */
        cplan = GetCachedPlan(plansource, paramLI, plan->saved);
        stmt_list = cplan->stmt_list;

        /*
         * In the default non-read-only case, get a new snapshot, replacing
         * any that we pushed in a previous cycle.
         */
        if (snapshot == InvalidSnapshot && !read_only)
        {
            if (pushed_active_snap)
                PopActiveSnapshot();
            PushActiveSnapshot(GetTransactionSnapshot());
            pushed_active_snap = true;
        }

        foreach(lc2, stmt_list)
        {
            Node       *stmt = (Node *) lfirst(lc2);
            bool        canSetTag;
            DestReceiver *dest;

            _SPI_current->processed = 0;
            _SPI_current->lastoid = InvalidOid;
            _SPI_current->tuptable = NULL;

            if (IsA(stmt, PlannedStmt))
            {
                canSetTag = ((PlannedStmt *) stmt)->canSetTag;
            }
            else
            {
                /* utilities are canSetTag if only thing in list */
                canSetTag = (list_length(stmt_list) == 1);

                if (IsA(stmt, CopyStmt))
                {
                    CopyStmt   *cstmt = (CopyStmt *) stmt;

                    if (cstmt->filename == NULL)
                    {
                        my_res = SPI_ERROR_COPY;
                        goto fail;
                    }
                }
                else if (IsA(stmt, TransactionStmt))
                {
                    my_res = SPI_ERROR_TRANSACTION;
                    goto fail;
                }
            }

            if (read_only && !CommandIsReadOnly(stmt))
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                /* translator: %s is a SQL statement name */
                       errmsg("%s is not allowed in a non-volatile function",
                              CreateCommandTag(stmt))));

            /*
             * If not read-only mode, advance the command counter before each
             * command and update the snapshot.
             */
            if (!read_only)
            {
                CommandCounterIncrement();
                UpdateActiveSnapshotCommandId();
            }

            dest = CreateDestReceiver(canSetTag ? DestSPI : DestNone);

            if (IsA(stmt, PlannedStmt) &&
                ((PlannedStmt *) stmt)->utilityStmt == NULL)
            {
                QueryDesc  *qdesc;
                Snapshot    snap;

                if (ActiveSnapshotSet())
                    snap = GetActiveSnapshot();
                else
                    snap = InvalidSnapshot;

                qdesc = CreateQueryDesc((PlannedStmt *) stmt,
                                        plansource->query_string,
                                        snap, crosscheck_snapshot,
                                        dest,
                                        paramLI, 0);
                res = _SPI_pquery(qdesc, fire_triggers,
                                  canSetTag ? tcount : 0);
                FreeQueryDesc(qdesc);
            }
            else
            {
                char        completionTag[COMPLETION_TAG_BUFSIZE];

                ProcessUtility(stmt,
                               plansource->query_string,
                               PROCESS_UTILITY_QUERY,
                               paramLI,
                               dest,
                               completionTag);

                /* Update "processed" if stmt returned tuples */
                if (_SPI_current->tuptable)
                    _SPI_current->processed = _SPI_current->tuptable->alloced -
                        _SPI_current->tuptable->free;

                res = SPI_OK_UTILITY;

                /*
                 * Some utility statements return a row count, even though the
                 * tuples are not returned to the caller.
                 */
                if (IsA(stmt, CreateTableAsStmt))
                {
                    Assert(strncmp(completionTag, "SELECT ", 7) == 0);
                    _SPI_current->processed = strtoul(completionTag + 7,
                                                      NULL, 10);

                    /*
                     * For historical reasons, if CREATE TABLE AS was spelled
                     * as SELECT INTO, return a special return code.
                     */
                    if (((CreateTableAsStmt *) stmt)->is_select_into)
                        res = SPI_OK_SELINTO;
                }
                else if (IsA(stmt, CopyStmt))
                {
                    Assert(strncmp(completionTag, "COPY ", 5) == 0);
                    _SPI_current->processed = strtoul(completionTag + 5,
                                                      NULL, 10);
                }
            }

            /*
             * The last canSetTag query sets the status values returned to the
             * caller.  Be careful to free any tuptables not returned, to
             * avoid intratransaction memory leak.
             */
            if (canSetTag)
            {
                my_processed = _SPI_current->processed;
                my_lastoid = _SPI_current->lastoid;
                SPI_freetuptable(my_tuptable);
                my_tuptable = _SPI_current->tuptable;
                my_res = res;
            }
            else
            {
                SPI_freetuptable(_SPI_current->tuptable);
                _SPI_current->tuptable = NULL;
            }
            /* we know that the receiver doesn't need a destroy call */
            if (res < 0)
            {
                my_res = res;
                goto fail;
            }
        }

        /* Done with this plan, so release refcount */
        ReleaseCachedPlan(cplan, plan->saved);
        cplan = NULL;

        /*
         * If not read-only mode, advance the command counter after the last
         * command.  This ensures that its effects are visible, in case it was
         * DDL that would affect the next CachedPlanSource.
         */
        if (!read_only)
            CommandCounterIncrement();
    }

fail:

    /* Pop the snapshot off the stack if we pushed one */
    if (pushed_active_snap)
        PopActiveSnapshot();

    /* We no longer need the cached plan refcount, if any */
    if (cplan)
        ReleaseCachedPlan(cplan, plan->saved);

    /*
     * Pop the error context stack
     */
    error_context_stack = spierrcontext.previous;

    /* Save results for caller */
    SPI_processed = my_processed;
    SPI_lastoid = my_lastoid;
    SPI_tuptable = my_tuptable;

    /* tuptable now is caller's responsibility, not SPI's */
    _SPI_current->tuptable = NULL;

    /*
     * If none of the queries had canSetTag, return SPI_OK_REWRITTEN. Prior to
     * 8.4, we used return the last query's result code, but not its auxiliary
     * results, but that's confusing.
     */
    if (my_res == 0)
        my_res = SPI_OK_REWRITTEN;

    return my_res;
}

/*
 * Convert arrays of query parameters to form wanted by planner and executor
 */
static ParamListInfo
_SPI_convert_params(int nargs, Oid *argtypes,
                    Datum *Values, const char *Nulls)
{
    ParamListInfo paramLI;

    if (nargs > 0)
    {
        int         i;

        /* sizeof(ParamListInfoData) includes the first array element */
        paramLI = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
                                      (nargs - 1) * sizeof(ParamExternData));
        /* we have static list of params, so no hooks needed */
        paramLI->paramFetch = NULL;
        paramLI->paramFetchArg = NULL;
        paramLI->parserSetup = NULL;
        paramLI->parserSetupArg = NULL;
        paramLI->numParams = nargs;

        for (i = 0; i < nargs; i++)
        {
            ParamExternData *prm = &paramLI->params[i];

            prm->value = Values[i];
            prm->isnull = (Nulls && Nulls[i] == 'n');
            prm->pflags = PARAM_FLAG_CONST;
            prm->ptype = argtypes[i];
        }
    }
    else
        paramLI = NULL;
    return paramLI;
}

static int
_SPI_pquery(QueryDesc *queryDesc, bool fire_triggers, long tcount)
{
    int         operation = queryDesc->operation;
    int         eflags;
    int         res;

    switch (operation)
    {
        case CMD_SELECT:
            Assert(queryDesc->plannedstmt->utilityStmt == NULL);
            if (queryDesc->dest->mydest != DestSPI)
            {
                /* Don't return SPI_OK_SELECT if we're discarding result */
                res = SPI_OK_UTILITY;
            }
            else
                res = SPI_OK_SELECT;
            break;
        case CMD_INSERT:
            if (queryDesc->plannedstmt->hasReturning)
                res = SPI_OK_INSERT_RETURNING;
            else
                res = SPI_OK_INSERT;
            break;
        case CMD_DELETE:
            if (queryDesc->plannedstmt->hasReturning)
                res = SPI_OK_DELETE_RETURNING;
            else
                res = SPI_OK_DELETE;
            break;
        case CMD_UPDATE:
            if (queryDesc->plannedstmt->hasReturning)
                res = SPI_OK_UPDATE_RETURNING;
            else
                res = SPI_OK_UPDATE;
            break;
        default:
            return SPI_ERROR_OPUNKNOWN;
    }

#ifdef SPI_EXECUTOR_STATS
    if (ShowExecutorStats)
        ResetUsage();
#endif

    /* Select execution options */
    if (fire_triggers)
        eflags = 0;             /* default run-to-completion flags */
    else
        eflags = EXEC_FLAG_SKIP_TRIGGERS;

    ExecutorStart(queryDesc, eflags);

    ExecutorRun(queryDesc, ForwardScanDirection, tcount);

    _SPI_current->processed = queryDesc->estate->es_processed;
    _SPI_current->lastoid = queryDesc->estate->es_lastoid;

    if ((res == SPI_OK_SELECT || queryDesc->plannedstmt->hasReturning) &&
        queryDesc->dest->mydest == DestSPI)
    {
        if (_SPI_checktuples())
            elog(ERROR, "consistency check on SPI tuple count failed");
    }

    ExecutorFinish(queryDesc);
    ExecutorEnd(queryDesc);
    /* FreeQueryDesc is done by the caller */

#ifdef SPI_EXECUTOR_STATS
    if (ShowExecutorStats)
        ShowUsage("SPI EXECUTOR STATS");
#endif

    return res;
}

/*
 * _SPI_error_callback
 *
 * Add context information when a query invoked via SPI fails
 */
static void
_SPI_error_callback(void *arg)
{
    const char *query = (const char *) arg;
    int         syntaxerrposition;

    /*
     * If there is a syntax error position, convert to internal syntax error;
     * otherwise treat the query as an item of context stack
     */
    syntaxerrposition = geterrposition();
    if (syntaxerrposition > 0)
    {
        errposition(0);
        internalerrposition(syntaxerrposition);
        internalerrquery(query);
    }
    else
        errcontext("SQL statement \"%s\"", query);
}

/*
 * _SPI_cursor_operation()
 *
 *  Do a FETCH or MOVE in a cursor
 */
static void
_SPI_cursor_operation(Portal portal, FetchDirection direction, long count,
                      DestReceiver *dest)
{
    long        nfetched;

    /* Check that the portal is valid */
    if (!PortalIsValid(portal))
        elog(ERROR, "invalid portal in SPI cursor operation");

    /* Push the SPI stack */
    if (_SPI_begin_call(true) < 0)
        elog(ERROR, "SPI cursor operation called while not connected");

    /* Reset the SPI result (note we deliberately don't touch lastoid) */
    SPI_processed = 0;
    SPI_tuptable = NULL;
    _SPI_current->processed = 0;
    _SPI_current->tuptable = NULL;

    /* Run the cursor */
    nfetched = PortalRunFetch(portal,
                              direction,
                              count,
                              dest);

    /*
     * Think not to combine this store with the preceding function call. If
     * the portal contains calls to functions that use SPI, then SPI_stack is
     * likely to move around while the portal runs.  When control returns,
     * _SPI_current will point to the correct stack entry... but the pointer
     * may be different than it was beforehand. So we must be sure to re-fetch
     * the pointer after the function call completes.
     */
    _SPI_current->processed = nfetched;

    if (dest->mydest == DestSPI && _SPI_checktuples())
        elog(ERROR, "consistency check on SPI tuple count failed");

    /* Put the result into place for access by caller */
    SPI_processed = _SPI_current->processed;
    SPI_tuptable = _SPI_current->tuptable;

    /* tuptable now is caller's responsibility, not SPI's */
    _SPI_current->tuptable = NULL;

    /* Pop the SPI stack */
    _SPI_end_call(true);
}


static MemoryContext
_SPI_execmem(void)
{
    return MemoryContextSwitchTo(_SPI_current->execCxt);
}

static MemoryContext
_SPI_procmem(void)
{
    return MemoryContextSwitchTo(_SPI_current->procCxt);
}

/*
 * _SPI_begin_call: begin a SPI operation within a connected procedure
 */
static int
_SPI_begin_call(bool execmem)
{
    if (_SPI_curid + 1 != _SPI_connected)
        return SPI_ERROR_UNCONNECTED;
    _SPI_curid++;
    if (_SPI_current != &(_SPI_stack[_SPI_curid]))
        elog(ERROR, "SPI stack corrupted");

    if (execmem)                /* switch to the Executor memory context */
        _SPI_execmem();

    return 0;
}

/*
 * _SPI_end_call: end a SPI operation within a connected procedure
 *
 * Note: this currently has no failure return cases, so callers don't check
 */
static int
_SPI_end_call(bool procmem)
{
    /*
     * We're returning to procedure where _SPI_curid == _SPI_connected - 1
     */
    _SPI_curid--;

    if (procmem)                /* switch to the procedure memory context */
    {
        _SPI_procmem();
        /* and free Executor memory */
        MemoryContextResetAndDeleteChildren(_SPI_current->execCxt);
    }

    return 0;
}

static bool
_SPI_checktuples(void)
{
    uint32      processed = _SPI_current->processed;
    SPITupleTable *tuptable = _SPI_current->tuptable;
    bool        failed = false;

    if (tuptable == NULL)       /* spi_dest_startup was not called */
        failed = true;
    else if (processed != (tuptable->alloced - tuptable->free))
        failed = true;

    return failed;
}

/*
 * Convert a "temporary" SPIPlan into an "unsaved" plan.
 *
 * The passed _SPI_plan struct is on the stack, and all its subsidiary data
 * is in or under the current SPI executor context.  Copy the plan into the
 * SPI procedure context so it will survive _SPI_end_call().  To minimize
 * data copying, this destructively modifies the input plan, by taking the
 * plancache entries away from it and reparenting them to the new SPIPlan.
 */
static SPIPlanPtr
_SPI_make_plan_non_temp(SPIPlanPtr plan)
{
    SPIPlanPtr  newplan;
    MemoryContext parentcxt = _SPI_current->procCxt;
    MemoryContext plancxt;
    MemoryContext oldcxt;
    ListCell   *lc;

    /* Assert the input is a temporary SPIPlan */
    Assert(plan->magic == _SPI_PLAN_MAGIC);
    Assert(plan->plancxt == NULL);
    /* One-shot plans can't be saved */
    Assert(!plan->oneshot);

    /*
     * Create a memory context for the plan, underneath the procedure context.
     * We don't expect the plan to be very large, so use smaller-than-default
     * alloc parameters.
     */
    plancxt = AllocSetContextCreate(parentcxt,
                                    "SPI Plan",
                                    ALLOCSET_SMALL_MINSIZE,
                                    ALLOCSET_SMALL_INITSIZE,
                                    ALLOCSET_SMALL_MAXSIZE);
    oldcxt = MemoryContextSwitchTo(plancxt);

    /* Copy the SPI_plan struct and subsidiary data into the new context */
    newplan = (SPIPlanPtr) palloc(sizeof(_SPI_plan));
    newplan->magic = _SPI_PLAN_MAGIC;
    newplan->saved = false;
    newplan->oneshot = false;
    newplan->plancache_list = NIL;
    newplan->plancxt = plancxt;
    newplan->cursor_options = plan->cursor_options;
    newplan->nargs = plan->nargs;
    if (plan->nargs > 0)
    {
        newplan->argtypes = (Oid *) palloc(plan->nargs * sizeof(Oid));
        memcpy(newplan->argtypes, plan->argtypes, plan->nargs * sizeof(Oid));
    }
    else
        newplan->argtypes = NULL;
    newplan->parserSetup = plan->parserSetup;
    newplan->parserSetupArg = plan->parserSetupArg;

    /*
     * Reparent all the CachedPlanSources into the procedure context.  In
     * theory this could fail partway through due to the pallocs, but we don't
     * care too much since both the procedure context and the executor context
     * would go away on error.
     */
    foreach(lc, plan->plancache_list)
    {
        CachedPlanSource *plansource = (CachedPlanSource *) lfirst(lc);

        CachedPlanSetParentContext(plansource, parentcxt);

        /* Build new list, with list cells in plancxt */
        newplan->plancache_list = lappend(newplan->plancache_list, plansource);
    }

    MemoryContextSwitchTo(oldcxt);

    /* For safety, unlink the CachedPlanSources from the temporary plan */
    plan->plancache_list = NIL;

    return newplan;
}

/*
 * Make a "saved" copy of the given plan.
 */
static SPIPlanPtr
_SPI_save_plan(SPIPlanPtr plan)
{
    SPIPlanPtr  newplan;
    MemoryContext plancxt;
    MemoryContext oldcxt;
    ListCell   *lc;

    /* One-shot plans can't be saved */
    Assert(!plan->oneshot);

    /*
     * Create a memory context for the plan.  We don't expect the plan to be
     * very large, so use smaller-than-default alloc parameters.  It's a
     * transient context until we finish copying everything.
     */
    plancxt = AllocSetContextCreate(CurrentMemoryContext,
                                    "SPI Plan",
                                    ALLOCSET_SMALL_MINSIZE,
                                    ALLOCSET_SMALL_INITSIZE,
                                    ALLOCSET_SMALL_MAXSIZE);
    oldcxt = MemoryContextSwitchTo(plancxt);

    /* Copy the SPI plan into its own context */
    newplan = (SPIPlanPtr) palloc(sizeof(_SPI_plan));
    newplan->magic = _SPI_PLAN_MAGIC;
    newplan->saved = false;
    newplan->oneshot = false;
    newplan->plancache_list = NIL;
    newplan->plancxt = plancxt;
    newplan->cursor_options = plan->cursor_options;
    newplan->nargs = plan->nargs;
    if (plan->nargs > 0)
    {
        newplan->argtypes = (Oid *) palloc(plan->nargs * sizeof(Oid));
        memcpy(newplan->argtypes, plan->argtypes, plan->nargs * sizeof(Oid));
    }
    else
        newplan->argtypes = NULL;
    newplan->parserSetup = plan->parserSetup;
    newplan->parserSetupArg = plan->parserSetupArg;

    /* Copy all the plancache entries */
    foreach(lc, plan->plancache_list)
    {
        CachedPlanSource *plansource = (CachedPlanSource *) lfirst(lc);
        CachedPlanSource *newsource;

        newsource = CopyCachedPlan(plansource);
        newplan->plancache_list = lappend(newplan->plancache_list, newsource);
    }

    MemoryContextSwitchTo(oldcxt);

    /*
     * Mark it saved, reparent it under CacheMemoryContext, and mark all the
     * component CachedPlanSources as saved.  This sequence cannot fail
     * partway through, so there's no risk of long-term memory leakage.
     */
    newplan->saved = true;
    MemoryContextSetParent(newplan->plancxt, CacheMemoryContext);

    foreach(lc, newplan->plancache_list)
    {
        CachedPlanSource *plansource = (CachedPlanSource *) lfirst(lc);

        SaveCachedPlan(plansource);
    }

    return newplan;
}