execExprInterp.c

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/*-------------------------------------------------------------------------
 *
 * execExprInterp.c
 *    Interpreted evaluation of an expression step list.
 *
 * This file provides either a "direct threaded" (for gcc, clang and
 * compatible) or a "switch threaded" (for all compilers) implementation of
 * expression evaluation.  The former is amongst the fastest known methods
 * of interpreting programs without resorting to assembly level work, or
 * just-in-time compilation, but it requires support for computed gotos.
 * The latter is amongst the fastest approaches doable in standard C.
 *
 * In either case we use ExprEvalStep->opcode to dispatch to the code block
 * within ExecInterpExpr() that implements the specific opcode type.
 *
 * Switch-threading uses a plain switch() statement to perform the
 * dispatch.  This has the advantages of being plain C and allowing the
 * compiler to warn if implementation of a specific opcode has been forgotten.
 * The disadvantage is that dispatches will, as commonly implemented by
 * compilers, happen from a single location, requiring more jumps and causing
 * bad branch prediction.
 *
 * In direct threading, we use gcc's label-as-values extension - also adopted
 * by some other compilers - to replace ExprEvalStep->opcode with the address
 * of the block implementing the instruction. Dispatch to the next instruction
 * is done by a "computed goto".  This allows for better branch prediction
 * (as the jumps are happening from different locations) and fewer jumps
 * (as no preparatory jump to a common dispatch location is needed).
 *
 * When using direct threading, ExecReadyInterpretedExpr will replace
 * each step's opcode field with the address of the relevant code block and
 * ExprState->flags will contain EEO_FLAG_DIRECT_THREADED to remember that
 * that's been done.
 *
 * For very simple instructions the overhead of the full interpreter
 * "startup", as minimal as it is, is noticeable.  Therefore
 * ExecReadyInterpretedExpr will choose to implement certain simple
 * opcode patterns using special fast-path routines (ExecJust*).
 *
 * Complex or uncommon instructions are not implemented in-line in
 * ExecInterpExpr(), rather we call out to a helper function appearing later
 * in this file.  For one reason, there'd not be a noticeable performance
 * benefit, but more importantly those complex routines are intended to be
 * shared between different expression evaluation approaches.  For instance
 * a JIT compiler would generate calls to them.  (This is why they are
 * exported rather than being "static" in this file.)
 *
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/executor/execExprInterp.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heaptoast.h"
#include "catalog/pg_type.h"
#include "commands/sequence.h"
#include "executor/execExpr.h"
#include "executor/nodeSubplan.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "parser/parsetree.h"
#include "pgstat.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/date.h"
#include "utils/datum.h"
#include "utils/expandedrecord.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/timestamp.h"
#include "utils/typcache.h"
#include "utils/xml.h"

/*
 * Use computed-goto-based opcode dispatch when computed gotos are available.
 * But use a separate symbol so that it's easy to adjust locally in this file
 * for development and testing.
 */
#ifdef HAVE_COMPUTED_GOTO
#define EEO_USE_COMPUTED_GOTO
#endif                          /* HAVE_COMPUTED_GOTO */

/*
 * Macros for opcode dispatch.
 *
 * EEO_SWITCH - just hides the switch if not in use.
 * EEO_CASE - labels the implementation of named expression step type.
 * EEO_DISPATCH - jump to the implementation of the step type for 'op'.
 * EEO_OPCODE - compute opcode required by used expression evaluation method.
 * EEO_NEXT - increment 'op' and jump to correct next step type.
 * EEO_JUMP - jump to the specified step number within the current expression.
 */
#if defined(EEO_USE_COMPUTED_GOTO)

/* struct for jump target -> opcode lookup table */
typedef struct ExprEvalOpLookup
{
    const void *opcode;
    ExprEvalOp  op;
} ExprEvalOpLookup;

/* to make dispatch_table accessible outside ExecInterpExpr() */
static const void **dispatch_table = NULL;

/* jump target -> opcode lookup table */
static ExprEvalOpLookup reverse_dispatch_table[EEOP_LAST];

#define EEO_SWITCH()
#define EEO_CASE(name)      CASE_##name:
#define EEO_DISPATCH()      goto *((void *) op->opcode)
#define EEO_OPCODE(opcode)  ((intptr_t) dispatch_table[opcode])

#else                           /* !EEO_USE_COMPUTED_GOTO */

#define EEO_SWITCH()        starteval: switch ((ExprEvalOp) op->opcode)
#define EEO_CASE(name)      case name:
#define EEO_DISPATCH()      goto starteval
#define EEO_OPCODE(opcode)  (opcode)

#endif                          /* EEO_USE_COMPUTED_GOTO */

#define EEO_NEXT() \
    do { \
        op++; \
        EEO_DISPATCH(); \
    } while (0)

#define EEO_JUMP(stepno) \
    do { \
        op = &state->steps[stepno]; \
        EEO_DISPATCH(); \
    } while (0)


static Datum ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull);
static void ExecInitInterpreter(void);

/* support functions */
static void CheckVarSlotCompatibility(TupleTableSlot *slot, int attnum, Oid vartype);
static void CheckOpSlotCompatibility(ExprEvalStep *op, TupleTableSlot *slot);
static TupleDesc get_cached_rowtype(Oid type_id, int32 typmod,
                                    TupleDesc *cache_field, ExprContext *econtext);
static void ShutdownTupleDescRef(Datum arg);
static void ExecEvalRowNullInt(ExprState *state, ExprEvalStep *op,
                               ExprContext *econtext, bool checkisnull);

/* fast-path evaluation functions */
static Datum ExecJustInnerVar(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustOuterVar(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustScanVar(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignInnerVar(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignOuterVar(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignScanVar(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustApplyFuncToCase(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustConst(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustInnerVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustOuterVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustScanVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignInnerVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignOuterVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);
static Datum ExecJustAssignScanVarVirt(ExprState *state, ExprContext *econtext, bool *isnull);

/* execution helper functions */
static pg_attribute_always_inline void ExecAggPlainTransByVal(AggState *aggstate,
                                                              AggStatePerTrans pertrans,
                                                              AggStatePerGroup pergroup,
                                                              ExprContext *aggcontext,
                                                              int setno);
static pg_attribute_always_inline void ExecAggPlainTransByRef(AggState *aggstate,
                                                              AggStatePerTrans pertrans,
                                                              AggStatePerGroup pergroup,
                                                              ExprContext *aggcontext,
                                                              int setno);

/*
 * Prepare ExprState for interpreted execution.
 */
void
ExecReadyInterpretedExpr(ExprState *state)
{
    /* Ensure one-time interpreter setup has been done */
    ExecInitInterpreter();

    /* Simple validity checks on expression */
    Assert(state->steps_len >= 1);
    Assert(state->steps[state->steps_len - 1].opcode == EEOP_DONE);

    /*
     * Don't perform redundant initialization. This is unreachable in current
     * cases, but might be hit if there's additional expression evaluation
     * methods that rely on interpreted execution to work.
     */
    if (state->flags & EEO_FLAG_INTERPRETER_INITIALIZED)
        return;

    /*
     * First time through, check whether attribute matches Var.  Might not be
     * ok anymore, due to schema changes. We do that by setting up a callback
     * that does checking on the first call, which then sets the evalfunc
     * callback to the actual method of execution.
     */
    state->evalfunc = ExecInterpExprStillValid;

    /* DIRECT_THREADED should not already be set */
    Assert((state->flags & EEO_FLAG_DIRECT_THREADED) == 0);

    /*
     * There shouldn't be any errors before the expression is fully
     * initialized, and even if so, it'd lead to the expression being
     * abandoned.  So we can set the flag now and save some code.
     */
    state->flags |= EEO_FLAG_INTERPRETER_INITIALIZED;

    /*
     * Select fast-path evalfuncs for very simple expressions.  "Starting up"
     * the full interpreter is a measurable overhead for these, and these
     * patterns occur often enough to be worth optimizing.
     */
    if (state->steps_len == 3)
    {
        ExprEvalOp  step0 = state->steps[0].opcode;
        ExprEvalOp  step1 = state->steps[1].opcode;

        if (step0 == EEOP_INNER_FETCHSOME &&
            step1 == EEOP_INNER_VAR)
        {
            state->evalfunc_private = (void *) ExecJustInnerVar;
            return;
        }
        else if (step0 == EEOP_OUTER_FETCHSOME &&
                 step1 == EEOP_OUTER_VAR)
        {
            state->evalfunc_private = (void *) ExecJustOuterVar;
            return;
        }
        else if (step0 == EEOP_SCAN_FETCHSOME &&
                 step1 == EEOP_SCAN_VAR)
        {
            state->evalfunc_private = (void *) ExecJustScanVar;
            return;
        }
        else if (step0 == EEOP_INNER_FETCHSOME &&
                 step1 == EEOP_ASSIGN_INNER_VAR)
        {
            state->evalfunc_private = (void *) ExecJustAssignInnerVar;
            return;
        }
        else if (step0 == EEOP_OUTER_FETCHSOME &&
                 step1 == EEOP_ASSIGN_OUTER_VAR)
        {
            state->evalfunc_private = (void *) ExecJustAssignOuterVar;
            return;
        }
        else if (step0 == EEOP_SCAN_FETCHSOME &&
                 step1 == EEOP_ASSIGN_SCAN_VAR)
        {
            state->evalfunc_private = (void *) ExecJustAssignScanVar;
            return;
        }
        else if (step0 == EEOP_CASE_TESTVAL &&
                 step1 == EEOP_FUNCEXPR_STRICT &&
                 state->steps[0].d.casetest.value)
        {
            state->evalfunc_private = (void *) ExecJustApplyFuncToCase;
            return;
        }
    }
    else if (state->steps_len == 2)
    {
        ExprEvalOp  step0 = state->steps[0].opcode;

        if (step0 == EEOP_CONST)
        {
            state->evalfunc_private = (void *) ExecJustConst;
            return;
        }
        else if (step0 == EEOP_INNER_VAR)
        {
            state->evalfunc_private = (void *) ExecJustInnerVarVirt;
            return;
        }
        else if (step0 == EEOP_OUTER_VAR)
        {
            state->evalfunc_private = (void *) ExecJustOuterVarVirt;
            return;
        }
        else if (step0 == EEOP_SCAN_VAR)
        {
            state->evalfunc_private = (void *) ExecJustScanVarVirt;
            return;
        }
        else if (step0 == EEOP_ASSIGN_INNER_VAR)
        {
            state->evalfunc_private = (void *) ExecJustAssignInnerVarVirt;
            return;
        }
        else if (step0 == EEOP_ASSIGN_OUTER_VAR)
        {
            state->evalfunc_private = (void *) ExecJustAssignOuterVarVirt;
            return;
        }
        else if (step0 == EEOP_ASSIGN_SCAN_VAR)
        {
            state->evalfunc_private = (void *) ExecJustAssignScanVarVirt;
            return;
        }
    }

#if defined(EEO_USE_COMPUTED_GOTO)

    /*
     * In the direct-threaded implementation, replace each opcode with the
     * address to jump to.  (Use ExecEvalStepOp() to get back the opcode.)
     */
    for (int off = 0; off < state->steps_len; off++)
    {
        ExprEvalStep *op = &state->steps[off];

        op->opcode = EEO_OPCODE(op->opcode);
    }

    state->flags |= EEO_FLAG_DIRECT_THREADED;
#endif                          /* EEO_USE_COMPUTED_GOTO */

    state->evalfunc_private = (void *) ExecInterpExpr;
}


/*
 * Evaluate expression identified by "state" in the execution context
 * given by "econtext".  *isnull is set to the is-null flag for the result,
 * and the Datum value is the function result.
 *
 * As a special case, return the dispatch table's address if state is NULL.
 * This is used by ExecInitInterpreter to set up the dispatch_table global.
 * (Only applies when EEO_USE_COMPUTED_GOTO is defined.)
 */
static Datum
ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
{
    ExprEvalStep *op;
    TupleTableSlot *resultslot;
    TupleTableSlot *innerslot;
    TupleTableSlot *outerslot;
    TupleTableSlot *scanslot;

    /*
     * This array has to be in the same order as enum ExprEvalOp.
     */
#if defined(EEO_USE_COMPUTED_GOTO)
    static const void *const dispatch_table[] = {
        &&CASE_EEOP_DONE,
        &&CASE_EEOP_INNER_FETCHSOME,
        &&CASE_EEOP_OUTER_FETCHSOME,
        &&CASE_EEOP_SCAN_FETCHSOME,
        &&CASE_EEOP_INNER_VAR,
        &&CASE_EEOP_OUTER_VAR,
        &&CASE_EEOP_SCAN_VAR,
        &&CASE_EEOP_INNER_SYSVAR,
        &&CASE_EEOP_OUTER_SYSVAR,
        &&CASE_EEOP_SCAN_SYSVAR,
        &&CASE_EEOP_WHOLEROW,
        &&CASE_EEOP_ASSIGN_INNER_VAR,
        &&CASE_EEOP_ASSIGN_OUTER_VAR,
        &&CASE_EEOP_ASSIGN_SCAN_VAR,
        &&CASE_EEOP_ASSIGN_TMP,
        &&CASE_EEOP_ASSIGN_TMP_MAKE_RO,
        &&CASE_EEOP_CONST,
        &&CASE_EEOP_FUNCEXPR,
        &&CASE_EEOP_FUNCEXPR_STRICT,
        &&CASE_EEOP_FUNCEXPR_FUSAGE,
        &&CASE_EEOP_FUNCEXPR_STRICT_FUSAGE,
        &&CASE_EEOP_BOOL_AND_STEP_FIRST,
        &&CASE_EEOP_BOOL_AND_STEP,
        &&CASE_EEOP_BOOL_AND_STEP_LAST,
        &&CASE_EEOP_BOOL_OR_STEP_FIRST,
        &&CASE_EEOP_BOOL_OR_STEP,
        &&CASE_EEOP_BOOL_OR_STEP_LAST,
        &&CASE_EEOP_BOOL_NOT_STEP,
        &&CASE_EEOP_QUAL,
        &&CASE_EEOP_JUMP,
        &&CASE_EEOP_JUMP_IF_NULL,
        &&CASE_EEOP_JUMP_IF_NOT_NULL,
        &&CASE_EEOP_JUMP_IF_NOT_TRUE,
        &&CASE_EEOP_NULLTEST_ISNULL,
        &&CASE_EEOP_NULLTEST_ISNOTNULL,
        &&CASE_EEOP_NULLTEST_ROWISNULL,
        &&CASE_EEOP_NULLTEST_ROWISNOTNULL,
        &&CASE_EEOP_BOOLTEST_IS_TRUE,
        &&CASE_EEOP_BOOLTEST_IS_NOT_TRUE,
        &&CASE_EEOP_BOOLTEST_IS_FALSE,
        &&CASE_EEOP_BOOLTEST_IS_NOT_FALSE,
        &&CASE_EEOP_PARAM_EXEC,
        &&CASE_EEOP_PARAM_EXTERN,
        &&CASE_EEOP_PARAM_CALLBACK,
        &&CASE_EEOP_CASE_TESTVAL,
        &&CASE_EEOP_MAKE_READONLY,
        &&CASE_EEOP_IOCOERCE,
        &&CASE_EEOP_DISTINCT,
        &&CASE_EEOP_NOT_DISTINCT,
        &&CASE_EEOP_NULLIF,
        &&CASE_EEOP_SQLVALUEFUNCTION,
        &&CASE_EEOP_CURRENTOFEXPR,
        &&CASE_EEOP_NEXTVALUEEXPR,
        &&CASE_EEOP_ARRAYEXPR,
        &&CASE_EEOP_ARRAYCOERCE,
        &&CASE_EEOP_ROW,
        &&CASE_EEOP_ROWCOMPARE_STEP,
        &&CASE_EEOP_ROWCOMPARE_FINAL,
        &&CASE_EEOP_MINMAX,
        &&CASE_EEOP_FIELDSELECT,
        &&CASE_EEOP_FIELDSTORE_DEFORM,
        &&CASE_EEOP_FIELDSTORE_FORM,
        &&CASE_EEOP_SBSREF_SUBSCRIPTS,
        &&CASE_EEOP_SBSREF_OLD,
        &&CASE_EEOP_SBSREF_ASSIGN,
        &&CASE_EEOP_SBSREF_FETCH,
        &&CASE_EEOP_DOMAIN_TESTVAL,
        &&CASE_EEOP_DOMAIN_NOTNULL,
        &&CASE_EEOP_DOMAIN_CHECK,
        &&CASE_EEOP_CONVERT_ROWTYPE,
        &&CASE_EEOP_SCALARARRAYOP,
        &&CASE_EEOP_XMLEXPR,
        &&CASE_EEOP_AGGREF,
        &&CASE_EEOP_GROUPING_FUNC,
        &&CASE_EEOP_WINDOW_FUNC,
        &&CASE_EEOP_SUBPLAN,
        &&CASE_EEOP_AGG_STRICT_DESERIALIZE,
        &&CASE_EEOP_AGG_DESERIALIZE,
        &&CASE_EEOP_AGG_STRICT_INPUT_CHECK_ARGS,
        &&CASE_EEOP_AGG_STRICT_INPUT_CHECK_NULLS,
        &&CASE_EEOP_AGG_PLAIN_PERGROUP_NULLCHECK,
        &&CASE_EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL,
        &&CASE_EEOP_AGG_PLAIN_TRANS_STRICT_BYVAL,
        &&CASE_EEOP_AGG_PLAIN_TRANS_BYVAL,
        &&CASE_EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYREF,
        &&CASE_EEOP_AGG_PLAIN_TRANS_STRICT_BYREF,
        &&CASE_EEOP_AGG_PLAIN_TRANS_BYREF,
        &&CASE_EEOP_AGG_ORDERED_TRANS_DATUM,
        &&CASE_EEOP_AGG_ORDERED_TRANS_TUPLE,
        &&CASE_EEOP_LAST
    };

    StaticAssertStmt(EEOP_LAST + 1 == lengthof(dispatch_table),
                     "dispatch_table out of whack with ExprEvalOp");

    if (unlikely(state == NULL))
        return PointerGetDatum(dispatch_table);
#else
    Assert(state != NULL);
#endif                          /* EEO_USE_COMPUTED_GOTO */

    /* setup state */
    op = state->steps;
    resultslot = state->resultslot;
    innerslot = econtext->ecxt_innertuple;
    outerslot = econtext->ecxt_outertuple;
    scanslot = econtext->ecxt_scantuple;

#if defined(EEO_USE_COMPUTED_GOTO)
    EEO_DISPATCH();
#endif

    EEO_SWITCH()
    {
        EEO_CASE(EEOP_DONE)
        {
            goto out;
        }

        EEO_CASE(EEOP_INNER_FETCHSOME)
        {
            CheckOpSlotCompatibility(op, innerslot);

            slot_getsomeattrs(innerslot, op->d.fetch.last_var);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_OUTER_FETCHSOME)
        {
            CheckOpSlotCompatibility(op, outerslot);

            slot_getsomeattrs(outerslot, op->d.fetch.last_var);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_SCAN_FETCHSOME)
        {
            CheckOpSlotCompatibility(op, scanslot);

            slot_getsomeattrs(scanslot, op->d.fetch.last_var);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_INNER_VAR)
        {
            int         attnum = op->d.var.attnum;

            /*
             * Since we already extracted all referenced columns from the
             * tuple with a FETCHSOME step, we can just grab the value
             * directly out of the slot's decomposed-data arrays.  But let's
             * have an Assert to check that that did happen.
             */
            Assert(attnum >= 0 && attnum < innerslot->tts_nvalid);
            *op->resvalue = innerslot->tts_values[attnum];
            *op->resnull = innerslot->tts_isnull[attnum];

            EEO_NEXT();
        }

        EEO_CASE(EEOP_OUTER_VAR)
        {
            int         attnum = op->d.var.attnum;

            /* See EEOP_INNER_VAR comments */

            Assert(attnum >= 0 && attnum < outerslot->tts_nvalid);
            *op->resvalue = outerslot->tts_values[attnum];
            *op->resnull = outerslot->tts_isnull[attnum];

            EEO_NEXT();
        }

        EEO_CASE(EEOP_SCAN_VAR)
        {
            int         attnum = op->d.var.attnum;

            /* See EEOP_INNER_VAR comments */

            Assert(attnum >= 0 && attnum < scanslot->tts_nvalid);
            *op->resvalue = scanslot->tts_values[attnum];
            *op->resnull = scanslot->tts_isnull[attnum];

            EEO_NEXT();
        }

        EEO_CASE(EEOP_INNER_SYSVAR)
        {
            ExecEvalSysVar(state, op, econtext, innerslot);
            EEO_NEXT();
        }

        EEO_CASE(EEOP_OUTER_SYSVAR)
        {
            ExecEvalSysVar(state, op, econtext, outerslot);
            EEO_NEXT();
        }

        EEO_CASE(EEOP_SCAN_SYSVAR)
        {
            ExecEvalSysVar(state, op, econtext, scanslot);
            EEO_NEXT();
        }

        EEO_CASE(EEOP_WHOLEROW)
        {
            /* too complex for an inline implementation */
            ExecEvalWholeRowVar(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ASSIGN_INNER_VAR)
        {
            int         resultnum = op->d.assign_var.resultnum;
            int         attnum = op->d.assign_var.attnum;

            /*
             * We do not need CheckVarSlotCompatibility here; that was taken
             * care of at compilation time.  But see EEOP_INNER_VAR comments.
             */
            Assert(attnum >= 0 && attnum < innerslot->tts_nvalid);
            resultslot->tts_values[resultnum] = innerslot->tts_values[attnum];
            resultslot->tts_isnull[resultnum] = innerslot->tts_isnull[attnum];

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ASSIGN_OUTER_VAR)
        {
            int         resultnum = op->d.assign_var.resultnum;
            int         attnum = op->d.assign_var.attnum;

            /*
             * We do not need CheckVarSlotCompatibility here; that was taken
             * care of at compilation time.  But see EEOP_INNER_VAR comments.
             */
            Assert(attnum >= 0 && attnum < outerslot->tts_nvalid);
            resultslot->tts_values[resultnum] = outerslot->tts_values[attnum];
            resultslot->tts_isnull[resultnum] = outerslot->tts_isnull[attnum];

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ASSIGN_SCAN_VAR)
        {
            int         resultnum = op->d.assign_var.resultnum;
            int         attnum = op->d.assign_var.attnum;

            /*
             * We do not need CheckVarSlotCompatibility here; that was taken
             * care of at compilation time.  But see EEOP_INNER_VAR comments.
             */
            Assert(attnum >= 0 && attnum < scanslot->tts_nvalid);
            resultslot->tts_values[resultnum] = scanslot->tts_values[attnum];
            resultslot->tts_isnull[resultnum] = scanslot->tts_isnull[attnum];

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ASSIGN_TMP)
        {
            int         resultnum = op->d.assign_tmp.resultnum;

            resultslot->tts_values[resultnum] = state->resvalue;
            resultslot->tts_isnull[resultnum] = state->resnull;

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ASSIGN_TMP_MAKE_RO)
        {
            int         resultnum = op->d.assign_tmp.resultnum;

            resultslot->tts_isnull[resultnum] = state->resnull;
            if (!resultslot->tts_isnull[resultnum])
                resultslot->tts_values[resultnum] =
                    MakeExpandedObjectReadOnlyInternal(state->resvalue);
            else
                resultslot->tts_values[resultnum] = state->resvalue;

            EEO_NEXT();
        }

        EEO_CASE(EEOP_CONST)
        {
            *op->resnull = op->d.constval.isnull;
            *op->resvalue = op->d.constval.value;

            EEO_NEXT();
        }

        /*
         * Function-call implementations. Arguments have previously been
         * evaluated directly into fcinfo->args.
         *
         * As both STRICT checks and function-usage are noticeable performance
         * wise, and function calls are a very hot-path (they also back
         * operators!), it's worth having so many separate opcodes.
         *
         * Note: the reason for using a temporary variable "d", here and in
         * other places, is that some compilers think "*op->resvalue = f();"
         * requires them to evaluate op->resvalue into a register before
         * calling f(), just in case f() is able to modify op->resvalue
         * somehow.  The extra line of code can save a useless register spill
         * and reload across the function call.
         */
        EEO_CASE(EEOP_FUNCEXPR)
        {
            FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
            Datum       d;

            fcinfo->isnull = false;
            d = op->d.func.fn_addr(fcinfo);
            *op->resvalue = d;
            *op->resnull = fcinfo->isnull;

            EEO_NEXT();
        }

        EEO_CASE(EEOP_FUNCEXPR_STRICT)
        {
            FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
            NullableDatum *args = fcinfo->args;
            int         nargs = op->d.func.nargs;
            Datum       d;

            /* strict function, so check for NULL args */
            for (int argno = 0; argno < nargs; argno++)
            {
                if (args[argno].isnull)
                {
                    *op->resnull = true;
                    goto strictfail;
                }
            }
            fcinfo->isnull = false;
            d = op->d.func.fn_addr(fcinfo);
            *op->resvalue = d;
            *op->resnull = fcinfo->isnull;

    strictfail:
            EEO_NEXT();
        }

        EEO_CASE(EEOP_FUNCEXPR_FUSAGE)
        {
            /* not common enough to inline */
            ExecEvalFuncExprFusage(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_FUNCEXPR_STRICT_FUSAGE)
        {
            /* not common enough to inline */
            ExecEvalFuncExprStrictFusage(state, op, econtext);

            EEO_NEXT();
        }

        /*
         * If any of its clauses is FALSE, an AND's result is FALSE regardless
         * of the states of the rest of the clauses, so we can stop evaluating
         * and return FALSE immediately.  If none are FALSE and one or more is
         * NULL, we return NULL; otherwise we return TRUE.  This makes sense
         * when you interpret NULL as "don't know": perhaps one of the "don't
         * knows" would have been FALSE if we'd known its value.  Only when
         * all the inputs are known to be TRUE can we state confidently that
         * the AND's result is TRUE.
         */
        EEO_CASE(EEOP_BOOL_AND_STEP_FIRST)
        {
            *op->d.boolexpr.anynull = false;

            /*
             * EEOP_BOOL_AND_STEP_FIRST resets anynull, otherwise it's the
             * same as EEOP_BOOL_AND_STEP - so fall through to that.
             */

            /* FALL THROUGH */
        }

        EEO_CASE(EEOP_BOOL_AND_STEP)
        {
            if (*op->resnull)
            {
                *op->d.boolexpr.anynull = true;
            }
            else if (!DatumGetBool(*op->resvalue))
            {
                /* result is already set to FALSE, need not change it */
                /* bail out early */
                EEO_JUMP(op->d.boolexpr.jumpdone);
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_BOOL_AND_STEP_LAST)
        {
            if (*op->resnull)
            {
                /* result is already set to NULL, need not change it */
            }
            else if (!DatumGetBool(*op->resvalue))
            {
                /* result is already set to FALSE, need not change it */

                /*
                 * No point jumping early to jumpdone - would be same target
                 * (as this is the last argument to the AND expression),
                 * except more expensive.
                 */
            }
            else if (*op->d.boolexpr.anynull)
            {
                *op->resvalue = (Datum) 0;
                *op->resnull = true;
            }
            else
            {
                /* result is already set to TRUE, need not change it */
            }

            EEO_NEXT();
        }

        /*
         * If any of its clauses is TRUE, an OR's result is TRUE regardless of
         * the states of the rest of the clauses, so we can stop evaluating
         * and return TRUE immediately.  If none are TRUE and one or more is
         * NULL, we return NULL; otherwise we return FALSE.  This makes sense
         * when you interpret NULL as "don't know": perhaps one of the "don't
         * knows" would have been TRUE if we'd known its value.  Only when all
         * the inputs are known to be FALSE can we state confidently that the
         * OR's result is FALSE.
         */
        EEO_CASE(EEOP_BOOL_OR_STEP_FIRST)
        {
            *op->d.boolexpr.anynull = false;

            /*
             * EEOP_BOOL_OR_STEP_FIRST resets anynull, otherwise it's the same
             * as EEOP_BOOL_OR_STEP - so fall through to that.
             */

            /* FALL THROUGH */
        }

        EEO_CASE(EEOP_BOOL_OR_STEP)
        {
            if (*op->resnull)
            {
                *op->d.boolexpr.anynull = true;
            }
            else if (DatumGetBool(*op->resvalue))
            {
                /* result is already set to TRUE, need not change it */
                /* bail out early */
                EEO_JUMP(op->d.boolexpr.jumpdone);
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_BOOL_OR_STEP_LAST)
        {
            if (*op->resnull)
            {
                /* result is already set to NULL, need not change it */
            }
            else if (DatumGetBool(*op->resvalue))
            {
                /* result is already set to TRUE, need not change it */

                /*
                 * No point jumping to jumpdone - would be same target (as
                 * this is the last argument to the AND expression), except
                 * more expensive.
                 */
            }
            else if (*op->d.boolexpr.anynull)
            {
                *op->resvalue = (Datum) 0;
                *op->resnull = true;
            }
            else
            {
                /* result is already set to FALSE, need not change it */
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_BOOL_NOT_STEP)
        {
            /*
             * Evaluation of 'not' is simple... if expr is false, then return
             * 'true' and vice versa.  It's safe to do this even on a
             * nominally null value, so we ignore resnull; that means that
             * NULL in produces NULL out, which is what we want.
             */
            *op->resvalue = BoolGetDatum(!DatumGetBool(*op->resvalue));

            EEO_NEXT();
        }

        EEO_CASE(EEOP_QUAL)
        {
            /* simplified version of BOOL_AND_STEP for use by ExecQual() */

            /* If argument (also result) is false or null ... */
            if (*op->resnull ||
                !DatumGetBool(*op->resvalue))
            {
                /* ... bail out early, returning FALSE */
                *op->resnull = false;
                *op->resvalue = BoolGetDatum(false);
                EEO_JUMP(op->d.qualexpr.jumpdone);
            }

            /*
             * Otherwise, leave the TRUE value in place, in case this is the
             * last qual.  Then, TRUE is the correct answer.
             */

            EEO_NEXT();
        }

        EEO_CASE(EEOP_JUMP)
        {
            /* Unconditionally jump to target step */
            EEO_JUMP(op->d.jump.jumpdone);
        }

        EEO_CASE(EEOP_JUMP_IF_NULL)
        {
            /* Transfer control if current result is null */
            if (*op->resnull)
                EEO_JUMP(op->d.jump.jumpdone);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_JUMP_IF_NOT_NULL)
        {
            /* Transfer control if current result is non-null */
            if (!*op->resnull)
                EEO_JUMP(op->d.jump.jumpdone);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_JUMP_IF_NOT_TRUE)
        {
            /* Transfer control if current result is null or false */
            if (*op->resnull || !DatumGetBool(*op->resvalue))
                EEO_JUMP(op->d.jump.jumpdone);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_NULLTEST_ISNULL)
        {
            *op->resvalue = BoolGetDatum(*op->resnull);
            *op->resnull = false;

            EEO_NEXT();
        }

        EEO_CASE(EEOP_NULLTEST_ISNOTNULL)
        {
            *op->resvalue = BoolGetDatum(!*op->resnull);
            *op->resnull = false;

            EEO_NEXT();
        }

        EEO_CASE(EEOP_NULLTEST_ROWISNULL)
        {
            /* out of line implementation: too large */
            ExecEvalRowNull(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_NULLTEST_ROWISNOTNULL)
        {
            /* out of line implementation: too large */
            ExecEvalRowNotNull(state, op, econtext);

            EEO_NEXT();
        }

        /* BooleanTest implementations for all booltesttypes */

        EEO_CASE(EEOP_BOOLTEST_IS_TRUE)
        {
            if (*op->resnull)
            {
                *op->resvalue = BoolGetDatum(false);
                *op->resnull = false;
            }
            /* else, input value is the correct output as well */

            EEO_NEXT();
        }

        EEO_CASE(EEOP_BOOLTEST_IS_NOT_TRUE)
        {
            if (*op->resnull)
            {
                *op->resvalue = BoolGetDatum(true);
                *op->resnull = false;
            }
            else
                *op->resvalue = BoolGetDatum(!DatumGetBool(*op->resvalue));

            EEO_NEXT();
        }

        EEO_CASE(EEOP_BOOLTEST_IS_FALSE)
        {
            if (*op->resnull)
            {
                *op->resvalue = BoolGetDatum(false);
                *op->resnull = false;
            }
            else
                *op->resvalue = BoolGetDatum(!DatumGetBool(*op->resvalue));

            EEO_NEXT();
        }

        EEO_CASE(EEOP_BOOLTEST_IS_NOT_FALSE)
        {
            if (*op->resnull)
            {
                *op->resvalue = BoolGetDatum(true);
                *op->resnull = false;
            }
            /* else, input value is the correct output as well */

            EEO_NEXT();
        }

        EEO_CASE(EEOP_PARAM_EXEC)
        {
            /* out of line implementation: too large */
            ExecEvalParamExec(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_PARAM_EXTERN)
        {
            /* out of line implementation: too large */
            ExecEvalParamExtern(state, op, econtext);
            EEO_NEXT();
        }

        EEO_CASE(EEOP_PARAM_CALLBACK)
        {
            /* allow an extension module to supply a PARAM_EXTERN value */
            op->d.cparam.paramfunc(state, op, econtext);
            EEO_NEXT();
        }

        EEO_CASE(EEOP_CASE_TESTVAL)
        {
            /*
             * Normally upper parts of the expression tree have setup the
             * values to be returned here, but some parts of the system
             * currently misuse {caseValue,domainValue}_{datum,isNull} to set
             * run-time data.  So if no values have been set-up, use
             * ExprContext's.  This isn't pretty, but also not *that* ugly,
             * and this is unlikely to be performance sensitive enough to
             * worry about an extra branch.
             */
            if (op->d.casetest.value)
            {
                *op->resvalue = *op->d.casetest.value;
                *op->resnull = *op->d.casetest.isnull;
            }
            else
            {
                *op->resvalue = econtext->caseValue_datum;
                *op->resnull = econtext->caseValue_isNull;
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_DOMAIN_TESTVAL)
        {
            /*
             * See EEOP_CASE_TESTVAL comment.
             */
            if (op->d.casetest.value)
            {
                *op->resvalue = *op->d.casetest.value;
                *op->resnull = *op->d.casetest.isnull;
            }
            else
            {
                *op->resvalue = econtext->domainValue_datum;
                *op->resnull = econtext->domainValue_isNull;
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_MAKE_READONLY)
        {
            /*
             * Force a varlena value that might be read multiple times to R/O
             */
            if (!*op->d.make_readonly.isnull)
                *op->resvalue =
                    MakeExpandedObjectReadOnlyInternal(*op->d.make_readonly.value);
            *op->resnull = *op->d.make_readonly.isnull;

            EEO_NEXT();
        }

        EEO_CASE(EEOP_IOCOERCE)
        {
            /*
             * Evaluate a CoerceViaIO node.  This can be quite a hot path, so
             * inline as much work as possible.  The source value is in our
             * result variable.
             */
            char       *str;

            /* call output function (similar to OutputFunctionCall) */
            if (*op->resnull)
            {
                /* output functions are not called on nulls */
                str = NULL;
            }
            else
            {
                FunctionCallInfo fcinfo_out;

                fcinfo_out = op->d.iocoerce.fcinfo_data_out;
                fcinfo_out->args[0].value = *op->resvalue;
                fcinfo_out->args[0].isnull = false;

                fcinfo_out->isnull = false;
                str = DatumGetCString(FunctionCallInvoke(fcinfo_out));

                /* OutputFunctionCall assumes result isn't null */
                Assert(!fcinfo_out->isnull);
            }

            /* call input function (similar to InputFunctionCall) */
            if (!op->d.iocoerce.finfo_in->fn_strict || str != NULL)
            {
                FunctionCallInfo fcinfo_in;
                Datum       d;

                fcinfo_in = op->d.iocoerce.fcinfo_data_in;
                fcinfo_in->args[0].value = PointerGetDatum(str);
                fcinfo_in->args[0].isnull = *op->resnull;
                /* second and third arguments are already set up */

                fcinfo_in->isnull = false;
                d = FunctionCallInvoke(fcinfo_in);
                *op->resvalue = d;

                /* Should get null result if and only if str is NULL */
                if (str == NULL)
                {
                    Assert(*op->resnull);
                    Assert(fcinfo_in->isnull);
                }
                else
                {
                    Assert(!*op->resnull);
                    Assert(!fcinfo_in->isnull);
                }
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_DISTINCT)
        {
            /*
             * IS DISTINCT FROM must evaluate arguments (already done into
             * fcinfo->args) to determine whether they are NULL; if either is
             * NULL then the result is determined.  If neither is NULL, then
             * proceed to evaluate the comparison function, which is just the
             * type's standard equality operator.  We need not care whether
             * that function is strict.  Because the handling of nulls is
             * different, we can't just reuse EEOP_FUNCEXPR.
             */
            FunctionCallInfo fcinfo = op->d.func.fcinfo_data;

            /* check function arguments for NULLness */
            if (fcinfo->args[0].isnull && fcinfo->args[1].isnull)
            {
                /* Both NULL? Then is not distinct... */
                *op->resvalue = BoolGetDatum(false);
                *op->resnull = false;
            }
            else if (fcinfo->args[0].isnull || fcinfo->args[1].isnull)
            {
                /* Only one is NULL? Then is distinct... */
                *op->resvalue = BoolGetDatum(true);
                *op->resnull = false;
            }
            else
            {
                /* Neither null, so apply the equality function */
                Datum       eqresult;

                fcinfo->isnull = false;
                eqresult = op->d.func.fn_addr(fcinfo);
                /* Must invert result of "="; safe to do even if null */
                *op->resvalue = BoolGetDatum(!DatumGetBool(eqresult));
                *op->resnull = fcinfo->isnull;
            }

            EEO_NEXT();
        }

        /* see EEOP_DISTINCT for comments, this is just inverted */
        EEO_CASE(EEOP_NOT_DISTINCT)
        {
            FunctionCallInfo fcinfo = op->d.func.fcinfo_data;

            if (fcinfo->args[0].isnull && fcinfo->args[1].isnull)
            {
                *op->resvalue = BoolGetDatum(true);
                *op->resnull = false;
            }
            else if (fcinfo->args[0].isnull || fcinfo->args[1].isnull)
            {
                *op->resvalue = BoolGetDatum(false);
                *op->resnull = false;
            }
            else
            {
                Datum       eqresult;

                fcinfo->isnull = false;
                eqresult = op->d.func.fn_addr(fcinfo);
                *op->resvalue = eqresult;
                *op->resnull = fcinfo->isnull;
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_NULLIF)
        {
            /*
             * The arguments are already evaluated into fcinfo->args.
             */
            FunctionCallInfo fcinfo = op->d.func.fcinfo_data;

            /* if either argument is NULL they can't be equal */
            if (!fcinfo->args[0].isnull && !fcinfo->args[1].isnull)
            {
                Datum       result;

                fcinfo->isnull = false;
                result = op->d.func.fn_addr(fcinfo);

                /* if the arguments are equal return null */
                if (!fcinfo->isnull && DatumGetBool(result))
                {
                    *op->resvalue = (Datum) 0;
                    *op->resnull = true;

                    EEO_NEXT();
                }
            }

            /* Arguments aren't equal, so return the first one */
            *op->resvalue = fcinfo->args[0].value;
            *op->resnull = fcinfo->args[0].isnull;

            EEO_NEXT();
        }

        EEO_CASE(EEOP_SQLVALUEFUNCTION)
        {
            /*
             * Doesn't seem worthwhile to have an inline implementation
             * efficiency-wise.
             */
            ExecEvalSQLValueFunction(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_CURRENTOFEXPR)
        {
            /* error invocation uses space, and shouldn't ever occur */
            ExecEvalCurrentOfExpr(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_NEXTVALUEEXPR)
        {
            /*
             * Doesn't seem worthwhile to have an inline implementation
             * efficiency-wise.
             */
            ExecEvalNextValueExpr(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ARRAYEXPR)
        {
            /* too complex for an inline implementation */
            ExecEvalArrayExpr(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ARRAYCOERCE)
        {
            /* too complex for an inline implementation */
            ExecEvalArrayCoerce(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ROW)
        {
            /* too complex for an inline implementation */
            ExecEvalRow(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ROWCOMPARE_STEP)
        {
            FunctionCallInfo fcinfo = op->d.rowcompare_step.fcinfo_data;
            Datum       d;

            /* force NULL result if strict fn and NULL input */
            if (op->d.rowcompare_step.finfo->fn_strict &&
                (fcinfo->args[0].isnull || fcinfo->args[1].isnull))
            {
                *op->resnull = true;
                EEO_JUMP(op->d.rowcompare_step.jumpnull);
            }

            /* Apply comparison function */
            fcinfo->isnull = false;
            d = op->d.rowcompare_step.fn_addr(fcinfo);
            *op->resvalue = d;

            /* force NULL result if NULL function result */
            if (fcinfo->isnull)
            {
                *op->resnull = true;
                EEO_JUMP(op->d.rowcompare_step.jumpnull);
            }
            *op->resnull = false;

            /* If unequal, no need to compare remaining columns */
            if (DatumGetInt32(*op->resvalue) != 0)
            {
                EEO_JUMP(op->d.rowcompare_step.jumpdone);
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_ROWCOMPARE_FINAL)
        {
            int32       cmpresult = DatumGetInt32(*op->resvalue);
            RowCompareType rctype = op->d.rowcompare_final.rctype;

            *op->resnull = false;
            switch (rctype)
            {
                    /* EQ and NE cases aren't allowed here */
                case ROWCOMPARE_LT:
                    *op->resvalue = BoolGetDatum(cmpresult < 0);
                    break;
                case ROWCOMPARE_LE:
                    *op->resvalue = BoolGetDatum(cmpresult <= 0);
                    break;
                case ROWCOMPARE_GE:
                    *op->resvalue = BoolGetDatum(cmpresult >= 0);
                    break;
                case ROWCOMPARE_GT:
                    *op->resvalue = BoolGetDatum(cmpresult > 0);
                    break;
                default:
                    Assert(false);
                    break;
            }

            EEO_NEXT();
        }

        EEO_CASE(EEOP_MINMAX)
        {
            /* too complex for an inline implementation */
            ExecEvalMinMax(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_FIELDSELECT)
        {
            /* too complex for an inline implementation */
            ExecEvalFieldSelect(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_FIELDSTORE_DEFORM)
        {
            /* too complex for an inline implementation */
            ExecEvalFieldStoreDeForm(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_FIELDSTORE_FORM)
        {
            /* too complex for an inline implementation */
            ExecEvalFieldStoreForm(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_SBSREF_SUBSCRIPTS)
        {
            /* Precheck SubscriptingRef subscript(s) */
            if (op->d.sbsref_subscript.subscriptfunc(state, op, econtext))
            {
                EEO_NEXT();
            }
            else
            {
                /* Subscript is null, short-circuit SubscriptingRef to NULL */
                EEO_JUMP(op->d.sbsref_subscript.jumpdone);
            }
        }

        EEO_CASE(EEOP_SBSREF_OLD)
            EEO_CASE(EEOP_SBSREF_ASSIGN)
            EEO_CASE(EEOP_SBSREF_FETCH)
        {
            /* Perform a SubscriptingRef fetch or assignment */
            op->d.sbsref.subscriptfunc(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_CONVERT_ROWTYPE)
        {
            /* too complex for an inline implementation */
            ExecEvalConvertRowtype(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_SCALARARRAYOP)
        {
            /* too complex for an inline implementation */
            ExecEvalScalarArrayOp(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_DOMAIN_NOTNULL)
        {
            /* too complex for an inline implementation */
            ExecEvalConstraintNotNull(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_DOMAIN_CHECK)
        {
            /* too complex for an inline implementation */
            ExecEvalConstraintCheck(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_XMLEXPR)
        {
            /* too complex for an inline implementation */
            ExecEvalXmlExpr(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_AGGREF)
        {
            /*
             * Returns a Datum whose value is the precomputed aggregate value
             * found in the given expression context.
             */
            int         aggno = op->d.aggref.aggno;

            Assert(econtext->ecxt_aggvalues != NULL);

            *op->resvalue = econtext->ecxt_aggvalues[aggno];
            *op->resnull = econtext->ecxt_aggnulls[aggno];

            EEO_NEXT();
        }

        EEO_CASE(EEOP_GROUPING_FUNC)
        {
            /* too complex/uncommon for an inline implementation */
            ExecEvalGroupingFunc(state, op);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_WINDOW_FUNC)
        {
            /*
             * Like Aggref, just return a precomputed value from the econtext.
             */
            WindowFuncExprState *wfunc = op->d.window_func.wfstate;

            Assert(econtext->ecxt_aggvalues != NULL);

            *op->resvalue = econtext->ecxt_aggvalues[wfunc->wfuncno];
            *op->resnull = econtext->ecxt_aggnulls[wfunc->wfuncno];

            EEO_NEXT();
        }

        EEO_CASE(EEOP_SUBPLAN)
        {
            /* too complex for an inline implementation */
            ExecEvalSubPlan(state, op, econtext);

            EEO_NEXT();
        }

        /* evaluate a strict aggregate deserialization function */
        EEO_CASE(EEOP_AGG_STRICT_DESERIALIZE)
        {
            /* Don't call a strict deserialization function with NULL input */
            if (op->d.agg_deserialize.fcinfo_data->args[0].isnull)
                EEO_JUMP(op->d.agg_deserialize.jumpnull);

            /* fallthrough */
        }

        /* evaluate aggregate deserialization function (non-strict portion) */
        EEO_CASE(EEOP_AGG_DESERIALIZE)
        {
            FunctionCallInfo fcinfo = op->d.agg_deserialize.fcinfo_data;
            AggState   *aggstate = castNode(AggState, state->parent);
            MemoryContext oldContext;

            /*
             * We run the deserialization functions in per-input-tuple memory
             * context.
             */
            oldContext = MemoryContextSwitchTo(aggstate->tmpcontext->ecxt_per_tuple_memory);
            fcinfo->isnull = false;
            *op->resvalue = FunctionCallInvoke(fcinfo);
            *op->resnull = fcinfo->isnull;
            MemoryContextSwitchTo(oldContext);

            EEO_NEXT();
        }

        /*
         * Check that a strict aggregate transition / combination function's
         * input is not NULL.
         */

        EEO_CASE(EEOP_AGG_STRICT_INPUT_CHECK_ARGS)
        {
            NullableDatum *args = op->d.agg_strict_input_check.args;
            int         nargs = op->d.agg_strict_input_check.nargs;

            for (int argno = 0; argno < nargs; argno++)
            {
                if (args[argno].isnull)
                    EEO_JUMP(op->d.agg_strict_input_check.jumpnull);
            }
            EEO_NEXT();
        }

        EEO_CASE(EEOP_AGG_STRICT_INPUT_CHECK_NULLS)
        {
            bool       *nulls = op->d.agg_strict_input_check.nulls;
            int         nargs = op->d.agg_strict_input_check.nargs;

            for (int argno = 0; argno < nargs; argno++)
            {
                if (nulls[argno])
                    EEO_JUMP(op->d.agg_strict_input_check.jumpnull);
            }
            EEO_NEXT();
        }

        /*
         * Check for a NULL pointer to the per-group states.
         */

        EEO_CASE(EEOP_AGG_PLAIN_PERGROUP_NULLCHECK)
        {
            AggState   *aggstate = castNode(AggState, state->parent);
            AggStatePerGroup pergroup_allaggs =
            aggstate->all_pergroups[op->d.agg_plain_pergroup_nullcheck.setoff];

            if (pergroup_allaggs == NULL)
                EEO_JUMP(op->d.agg_plain_pergroup_nullcheck.jumpnull);

            EEO_NEXT();
        }

        /*
         * Different types of aggregate transition functions are implemented
         * as different types of steps, to avoid incurring unnecessary
         * overhead.  There's a step type for each valid combination of having
         * a by value / by reference transition type, [not] needing to the
         * initialize the transition value for the first row in a group from
         * input, and [not] strict transition function.
         *
         * Could optimize further by splitting off by-reference for
         * fixed-length types, but currently that doesn't seem worth it.
         */

        EEO_CASE(EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL)
        {
            AggState   *aggstate = castNode(AggState, state->parent);
            AggStatePerTrans pertrans = op->d.agg_trans.pertrans;
            AggStatePerGroup pergroup =
            &aggstate->all_pergroups[op->d.agg_trans.setoff][op->d.agg_trans.transno];

            Assert(pertrans->transtypeByVal);

            if (pergroup->noTransValue)
            {
                /* If transValue has not yet been initialized, do so now. */
                ExecAggInitGroup(aggstate, pertrans, pergroup,
                                 op->d.agg_trans.aggcontext);
                /* copied trans value from input, done this round */
            }
            else if (likely(!pergroup->transValueIsNull))
            {
                /* invoke transition function, unless prevented by strictness */
                ExecAggPlainTransByVal(aggstate, pertrans, pergroup,
                                       op->d.agg_trans.aggcontext,
                                       op->d.agg_trans.setno);
            }

            EEO_NEXT();
        }

        /* see comments above EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL */
        EEO_CASE(EEOP_AGG_PLAIN_TRANS_STRICT_BYVAL)
        {
            AggState   *aggstate = castNode(AggState, state->parent);
            AggStatePerTrans pertrans = op->d.agg_trans.pertrans;
            AggStatePerGroup pergroup =
            &aggstate->all_pergroups[op->d.agg_trans.setoff][op->d.agg_trans.transno];

            Assert(pertrans->transtypeByVal);

            if (likely(!pergroup->transValueIsNull))
                ExecAggPlainTransByVal(aggstate, pertrans, pergroup,
                                       op->d.agg_trans.aggcontext,
                                       op->d.agg_trans.setno);

            EEO_NEXT();
        }

        /* see comments above EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL */
        EEO_CASE(EEOP_AGG_PLAIN_TRANS_BYVAL)
        {
            AggState   *aggstate = castNode(AggState, state->parent);
            AggStatePerTrans pertrans = op->d.agg_trans.pertrans;
            AggStatePerGroup pergroup =
            &aggstate->all_pergroups[op->d.agg_trans.setoff][op->d.agg_trans.transno];

            Assert(pertrans->transtypeByVal);

            ExecAggPlainTransByVal(aggstate, pertrans, pergroup,
                                   op->d.agg_trans.aggcontext,
                                   op->d.agg_trans.setno);

            EEO_NEXT();
        }

        /* see comments above EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL */
        EEO_CASE(EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYREF)
        {
            AggState   *aggstate = castNode(AggState, state->parent);
            AggStatePerTrans pertrans = op->d.agg_trans.pertrans;
            AggStatePerGroup pergroup =
            &aggstate->all_pergroups[op->d.agg_trans.setoff][op->d.agg_trans.transno];

            Assert(!pertrans->transtypeByVal);

            if (pergroup->noTransValue)
                ExecAggInitGroup(aggstate, pertrans, pergroup,
                                 op->d.agg_trans.aggcontext);
            else if (likely(!pergroup->transValueIsNull))
                ExecAggPlainTransByRef(aggstate, pertrans, pergroup,
                                       op->d.agg_trans.aggcontext,
                                       op->d.agg_trans.setno);

            EEO_NEXT();
        }

        /* see comments above EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL */
        EEO_CASE(EEOP_AGG_PLAIN_TRANS_STRICT_BYREF)
        {
            AggState   *aggstate = castNode(AggState, state->parent);
            AggStatePerTrans pertrans = op->d.agg_trans.pertrans;
            AggStatePerGroup pergroup =
            &aggstate->all_pergroups[op->d.agg_trans.setoff][op->d.agg_trans.transno];

            Assert(!pertrans->transtypeByVal);

            if (likely(!pergroup->transValueIsNull))
                ExecAggPlainTransByRef(aggstate, pertrans, pergroup,
                                       op->d.agg_trans.aggcontext,
                                       op->d.agg_trans.setno);
            EEO_NEXT();
        }

        /* see comments above EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL */
        EEO_CASE(EEOP_AGG_PLAIN_TRANS_BYREF)
        {
            AggState   *aggstate = castNode(AggState, state->parent);
            AggStatePerTrans pertrans = op->d.agg_trans.pertrans;
            AggStatePerGroup pergroup =
            &aggstate->all_pergroups[op->d.agg_trans.setoff][op->d.agg_trans.transno];

            Assert(!pertrans->transtypeByVal);

            ExecAggPlainTransByRef(aggstate, pertrans, pergroup,
                                   op->d.agg_trans.aggcontext,
                                   op->d.agg_trans.setno);

            EEO_NEXT();
        }

        /* process single-column ordered aggregate datum */
        EEO_CASE(EEOP_AGG_ORDERED_TRANS_DATUM)
        {
            /* too complex for an inline implementation */
            ExecEvalAggOrderedTransDatum(state, op, econtext);

            EEO_NEXT();
        }

        /* process multi-column ordered aggregate tuple */
        EEO_CASE(EEOP_AGG_ORDERED_TRANS_TUPLE)
        {
            /* too complex for an inline implementation */
            ExecEvalAggOrderedTransTuple(state, op, econtext);

            EEO_NEXT();
        }

        EEO_CASE(EEOP_LAST)
        {
            /* unreachable */
            Assert(false);
            goto out;
        }
    }

out:
    *isnull = state->resnull;
    return state->resvalue;
}

/*
 * Expression evaluation callback that performs extra checks before executing
 * the expression. Declared extern so other methods of execution can use it
 * too.
 */
Datum
ExecInterpExprStillValid(ExprState *state, ExprContext *econtext, bool *isNull)
{
    /*
     * First time through, check whether attribute matches Var.  Might not be
     * ok anymore, due to schema changes.
     */
    CheckExprStillValid(state, econtext);

    /* skip the check during further executions */
    state->evalfunc = (ExprStateEvalFunc) state->evalfunc_private;

    /* and actually execute */
    return state->evalfunc(state, econtext, isNull);
}

/*
 * Check that an expression is still valid in the face of potential schema
 * changes since the plan has been created.
 */
void
CheckExprStillValid(ExprState *state, ExprContext *econtext)
{
    TupleTableSlot *innerslot;
    TupleTableSlot *outerslot;
    TupleTableSlot *scanslot;

    innerslot = econtext->ecxt_innertuple;
    outerslot = econtext->ecxt_outertuple;
    scanslot = econtext->ecxt_scantuple;

    for (int i = 0; i < state->steps_len; i++)
    {
        ExprEvalStep *op = &state->steps[i];

        switch (ExecEvalStepOp(state, op))
        {
            case EEOP_INNER_VAR:
                {
                    int         attnum = op->d.var.attnum;

                    CheckVarSlotCompatibility(innerslot, attnum + 1, op->d.var.vartype);
                    break;
                }

            case EEOP_OUTER_VAR:
                {
                    int         attnum = op->d.var.attnum;

                    CheckVarSlotCompatibility(outerslot, attnum + 1, op->d.var.vartype);
                    break;
                }

            case EEOP_SCAN_VAR:
                {
                    int         attnum = op->d.var.attnum;

                    CheckVarSlotCompatibility(scanslot, attnum + 1, op->d.var.vartype);
                    break;
                }
            default:
                break;
        }
    }
}

/*
 * Check whether a user attribute in a slot can be referenced by a Var
 * expression.  This should succeed unless there have been schema changes
 * since the expression tree has been created.
 */
static void
CheckVarSlotCompatibility(TupleTableSlot *slot, int attnum, Oid vartype)
{
    /*
     * What we have to check for here is the possibility of an attribute
     * having been dropped or changed in type since the plan tree was created.
     * Ideally the plan will get invalidated and not re-used, but just in
     * case, we keep these defenses.  Fortunately it's sufficient to check
     * once on the first time through.
     *
     * Note: ideally we'd check typmod as well as typid, but that seems
     * impractical at the moment: in many cases the tupdesc will have been
     * generated by ExecTypeFromTL(), and that can't guarantee to generate an
     * accurate typmod in all cases, because some expression node types don't
     * carry typmod.  Fortunately, for precisely that reason, there should be
     * no places with a critical dependency on the typmod of a value.
     *
     * System attributes don't require checking since their types never
     * change.
     */
    if (attnum > 0)
    {
        TupleDesc   slot_tupdesc = slot->tts_tupleDescriptor;
        Form_pg_attribute attr;

        if (attnum > slot_tupdesc->natts)   /* should never happen */
            elog(ERROR, "attribute number %d exceeds number of columns %d",
                 attnum, slot_tupdesc->natts);

        attr = TupleDescAttr(slot_tupdesc, attnum - 1);

        if (attr->attisdropped)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_COLUMN),
                     errmsg("attribute %d of type %s has been dropped",
                            attnum, format_type_be(slot_tupdesc->tdtypeid))));

        if (vartype != attr->atttypid)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("attribute %d of type %s has wrong type",
                            attnum, format_type_be(slot_tupdesc->tdtypeid)),
                     errdetail("Table has type %s, but query expects %s.",
                               format_type_be(attr->atttypid),
                               format_type_be(vartype))));
    }
}

/*
 * Verify that the slot is compatible with a EEOP_*_FETCHSOME operation.
 */
static void
CheckOpSlotCompatibility(ExprEvalStep *op, TupleTableSlot *slot)
{
#ifdef USE_ASSERT_CHECKING
    /* there's nothing to check */
    if (!op->d.fetch.fixed)
        return;

    /*
     * Should probably fixed at some point, but for now it's easier to allow
     * buffer and heap tuples to be used interchangeably.
     */
    if (slot->tts_ops == &TTSOpsBufferHeapTuple &&
        op->d.fetch.kind == &TTSOpsHeapTuple)
        return;
    if (slot->tts_ops == &TTSOpsHeapTuple &&
        op->d.fetch.kind == &TTSOpsBufferHeapTuple)
        return;

    /*
     * At the moment we consider it OK if a virtual slot is used instead of a
     * specific type of slot, as a virtual slot never needs to be deformed.
     */
    if (slot->tts_ops == &TTSOpsVirtual)
        return;

    Assert(op->d.fetch.kind == slot->tts_ops);
#endif
}

/*
 * get_cached_rowtype: utility function to lookup a rowtype tupdesc
 *
 * type_id, typmod: identity of the rowtype
 * cache_field: where to cache the TupleDesc pointer in expression state node
 *      (field must be initialized to NULL)
 * econtext: expression context we are executing in
 *
 * NOTE: because the shutdown callback will be called during plan rescan,
 * must be prepared to re-do this during any node execution; cannot call
 * just once during expression initialization.
 */
static TupleDesc
get_cached_rowtype(Oid type_id, int32 typmod,
                   TupleDesc *cache_field, ExprContext *econtext)
{
    TupleDesc   tupDesc = *cache_field;

    /* Do lookup if no cached value or if requested type changed */
    if (tupDesc == NULL ||
        type_id != tupDesc->tdtypeid ||
        typmod != tupDesc->tdtypmod)
    {
        tupDesc = lookup_rowtype_tupdesc(type_id, typmod);

        if (*cache_field)
        {
            /* Release old tupdesc; but callback is already registered */
            ReleaseTupleDesc(*cache_field);
        }
        else
        {
            /* Need to register shutdown callback to release tupdesc */
            RegisterExprContextCallback(econtext,
                                        ShutdownTupleDescRef,
                                        PointerGetDatum(cache_field));
        }
        *cache_field = tupDesc;
    }
    return tupDesc;
}

/*
 * Callback function to release a tupdesc refcount at econtext shutdown
 */
static void
ShutdownTupleDescRef(Datum arg)
{
    TupleDesc  *cache_field = (TupleDesc *) DatumGetPointer(arg);

    if (*cache_field)
        ReleaseTupleDesc(*cache_field);
    *cache_field = NULL;
}

/*
 * Fast-path functions, for very simple expressions
 */

/* implementation of ExecJust(Inner|Outer|Scan)Var */
static pg_attribute_always_inline Datum
ExecJustVarImpl(ExprState *state, TupleTableSlot *slot, bool *isnull)
{
    ExprEvalStep *op = &state->steps[1];
    int         attnum = op->d.var.attnum + 1;

    CheckOpSlotCompatibility(&state->steps[0], slot);

    /*
     * Since we use slot_getattr(), we don't need to implement the FETCHSOME
     * step explicitly, and we also needn't Assert that the attnum is in range
     * --- slot_getattr() will take care of any problems.
     */
    return slot_getattr(slot, attnum, isnull);
}

/* Simple reference to inner Var */
static Datum
ExecJustInnerVar(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustVarImpl(state, econtext->ecxt_innertuple, isnull);
}

/* Simple reference to outer Var */
static Datum
ExecJustOuterVar(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustVarImpl(state, econtext->ecxt_outertuple, isnull);
}

/* Simple reference to scan Var */
static Datum
ExecJustScanVar(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustVarImpl(state, econtext->ecxt_scantuple, isnull);
}

/* implementation of ExecJustAssign(Inner|Outer|Scan)Var */
static pg_attribute_always_inline Datum
ExecJustAssignVarImpl(ExprState *state, TupleTableSlot *inslot, bool *isnull)
{
    ExprEvalStep *op = &state->steps[1];
    int         attnum = op->d.assign_var.attnum + 1;
    int         resultnum = op->d.assign_var.resultnum;
    TupleTableSlot *outslot = state->resultslot;

    CheckOpSlotCompatibility(&state->steps[0], inslot);

    /*
     * We do not need CheckVarSlotCompatibility here; that was taken care of
     * at compilation time.
     *
     * Since we use slot_getattr(), we don't need to implement the FETCHSOME
     * step explicitly, and we also needn't Assert that the attnum is in range
     * --- slot_getattr() will take care of any problems.
     */
    outslot->tts_values[resultnum] =
        slot_getattr(inslot, attnum, &outslot->tts_isnull[resultnum]);
    return 0;
}

/* Evaluate inner Var and assign to appropriate column of result tuple */
static Datum
ExecJustAssignInnerVar(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustAssignVarImpl(state, econtext->ecxt_innertuple, isnull);
}

/* Evaluate outer Var and assign to appropriate column of result tuple */
static Datum
ExecJustAssignOuterVar(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustAssignVarImpl(state, econtext->ecxt_outertuple, isnull);
}

/* Evaluate scan Var and assign to appropriate column of result tuple */
static Datum
ExecJustAssignScanVar(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustAssignVarImpl(state, econtext->ecxt_scantuple, isnull);
}

/* Evaluate CASE_TESTVAL and apply a strict function to it */
static Datum
ExecJustApplyFuncToCase(ExprState *state, ExprContext *econtext, bool *isnull)
{
    ExprEvalStep *op = &state->steps[0];
    FunctionCallInfo fcinfo;
    NullableDatum *args;
    int         nargs;
    Datum       d;

    /*
     * XXX with some redesign of the CaseTestExpr mechanism, maybe we could
     * get rid of this data shuffling?
     */
    *op->resvalue = *op->d.casetest.value;
    *op->resnull = *op->d.casetest.isnull;

    op++;

    nargs = op->d.func.nargs;
    fcinfo = op->d.func.fcinfo_data;
    args = fcinfo->args;

    /* strict function, so check for NULL args */
    for (int argno = 0; argno < nargs; argno++)
    {
        if (args[argno].isnull)
        {
            *isnull = true;
            return (Datum) 0;
        }
    }
    fcinfo->isnull = false;
    d = op->d.func.fn_addr(fcinfo);
    *isnull = fcinfo->isnull;
    return d;
}

/* Simple Const expression */
static Datum
ExecJustConst(ExprState *state, ExprContext *econtext, bool *isnull)
{
    ExprEvalStep *op = &state->steps[0];

    *isnull = op->d.constval.isnull;
    return op->d.constval.value;
}

/* implementation of ExecJust(Inner|Outer|Scan)VarVirt */
static pg_attribute_always_inline Datum
ExecJustVarVirtImpl(ExprState *state, TupleTableSlot *slot, bool *isnull)
{
    ExprEvalStep *op = &state->steps[0];
    int         attnum = op->d.var.attnum;

    /*
     * As it is guaranteed that a virtual slot is used, there never is a need
     * to perform tuple deforming (nor would it be possible). Therefore
     * execExpr.c has not emitted an EEOP_*_FETCHSOME step. Verify, as much as
     * possible, that that determination was accurate.
     */
    Assert(TTS_IS_VIRTUAL(slot));
    Assert(TTS_FIXED(slot));
    Assert(attnum >= 0 && attnum < slot->tts_nvalid);

    *isnull = slot->tts_isnull[attnum];

    return slot->tts_values[attnum];
}

/* Like ExecJustInnerVar, optimized for virtual slots */
static Datum
ExecJustInnerVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustVarVirtImpl(state, econtext->ecxt_innertuple, isnull);
}

/* Like ExecJustOuterVar, optimized for virtual slots */
static Datum
ExecJustOuterVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustVarVirtImpl(state, econtext->ecxt_outertuple, isnull);
}

/* Like ExecJustScanVar, optimized for virtual slots */
static Datum
ExecJustScanVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustVarVirtImpl(state, econtext->ecxt_scantuple, isnull);
}

/* implementation of ExecJustAssign(Inner|Outer|Scan)VarVirt */
static pg_attribute_always_inline Datum
ExecJustAssignVarVirtImpl(ExprState *state, TupleTableSlot *inslot, bool *isnull)
{
    ExprEvalStep *op = &state->steps[0];
    int         attnum = op->d.assign_var.attnum;
    int         resultnum = op->d.assign_var.resultnum;
    TupleTableSlot *outslot = state->resultslot;

    /* see ExecJustVarVirtImpl for comments */

    Assert(TTS_IS_VIRTUAL(inslot));
    Assert(TTS_FIXED(inslot));
    Assert(attnum >= 0 && attnum < inslot->tts_nvalid);

    outslot->tts_values[resultnum] = inslot->tts_values[attnum];
    outslot->tts_isnull[resultnum] = inslot->tts_isnull[attnum];

    return 0;
}

/* Like ExecJustAssignInnerVar, optimized for virtual slots */
static Datum
ExecJustAssignInnerVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustAssignVarVirtImpl(state, econtext->ecxt_innertuple, isnull);
}

/* Like ExecJustAssignOuterVar, optimized for virtual slots */
static Datum
ExecJustAssignOuterVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustAssignVarVirtImpl(state, econtext->ecxt_outertuple, isnull);
}

/* Like ExecJustAssignScanVar, optimized for virtual slots */
static Datum
ExecJustAssignScanVarVirt(ExprState *state, ExprContext *econtext, bool *isnull)
{
    return ExecJustAssignVarVirtImpl(state, econtext->ecxt_scantuple, isnull);
}

#if defined(EEO_USE_COMPUTED_GOTO)
/*
 * Comparator used when building address->opcode lookup table for
 * ExecEvalStepOp() in the threaded dispatch case.
 */
static int
dispatch_compare_ptr(const void *a, const void *b)
{
    const ExprEvalOpLookup *la = (const ExprEvalOpLookup *) a;
    const ExprEvalOpLookup *lb = (const ExprEvalOpLookup *) b;

    if (la->opcode < lb->opcode)
        return -1;
    else if (la->opcode > lb->opcode)
        return 1;
    return 0;
}
#endif

/*
 * Do one-time initialization of interpretation machinery.
 */
static void
ExecInitInterpreter(void)
{
#if defined(EEO_USE_COMPUTED_GOTO)
    /* Set up externally-visible pointer to dispatch table */
    if (dispatch_table == NULL)
    {
        dispatch_table = (const void **)
            DatumGetPointer(ExecInterpExpr(NULL, NULL, NULL));

        /* build reverse lookup table */
        for (int i = 0; i < EEOP_LAST; i++)
        {
            reverse_dispatch_table[i].opcode = dispatch_table[i];
            reverse_dispatch_table[i].op = (ExprEvalOp) i;
        }

        /* make it bsearch()able */
        qsort(reverse_dispatch_table,
              EEOP_LAST /* nmembers */ ,
              sizeof(ExprEvalOpLookup),
              dispatch_compare_ptr);
    }
#endif
}

/*
 * Function to return the opcode of an expression step.
 *
 * When direct-threading is in use, ExprState->opcode isn't easily
 * decipherable. This function returns the appropriate enum member.
 */
ExprEvalOp
ExecEvalStepOp(ExprState *state, ExprEvalStep *op)
{
#if defined(EEO_USE_COMPUTED_GOTO)
    if (state->flags & EEO_FLAG_DIRECT_THREADED)
    {
        ExprEvalOpLookup key;
        ExprEvalOpLookup *res;

        key.opcode = (void *) op->opcode;
        res = bsearch(&key,
                      reverse_dispatch_table,
                      EEOP_LAST /* nmembers */ ,
                      sizeof(ExprEvalOpLookup),
                      dispatch_compare_ptr);
        Assert(res);            /* unknown ops shouldn't get looked up */
        return res->op;
    }
#endif
    return (ExprEvalOp) op->opcode;
}


/*
 * Out-of-line helper functions for complex instructions.
 */

/*
 * Evaluate EEOP_FUNCEXPR_FUSAGE
 */
void
ExecEvalFuncExprFusage(ExprState *state, ExprEvalStep *op,
                       ExprContext *econtext)
{
    FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
    PgStat_FunctionCallUsage fcusage;
    Datum       d;

    pgstat_init_function_usage(fcinfo, &fcusage);

    fcinfo->isnull = false;
    d = op->d.func.fn_addr(fcinfo);
    *op->resvalue = d;
    *op->resnull = fcinfo->isnull;

    pgstat_end_function_usage(&fcusage, true);
}

/*
 * Evaluate EEOP_FUNCEXPR_STRICT_FUSAGE
 */
void
ExecEvalFuncExprStrictFusage(ExprState *state, ExprEvalStep *op,
                             ExprContext *econtext)
{

    FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
    PgStat_FunctionCallUsage fcusage;
    NullableDatum *args = fcinfo->args;
    int         nargs = op->d.func.nargs;
    Datum       d;

    /* strict function, so check for NULL args */
    for (int argno = 0; argno < nargs; argno++)
    {
        if (args[argno].isnull)
        {
            *op->resnull = true;
            return;
        }
    }

    pgstat_init_function_usage(fcinfo, &fcusage);

    fcinfo->isnull = false;
    d = op->d.func.fn_addr(fcinfo);
    *op->resvalue = d;
    *op->resnull = fcinfo->isnull;

    pgstat_end_function_usage(&fcusage, true);
}

/*
 * Evaluate a PARAM_EXEC parameter.
 *
 * PARAM_EXEC params (internal executor parameters) are stored in the
 * ecxt_param_exec_vals array, and can be accessed by array index.
 */
void
ExecEvalParamExec(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    ParamExecData *prm;

    prm = &(econtext->ecxt_param_exec_vals[op->d.param.paramid]);
    if (unlikely(prm->execPlan != NULL))
    {
        /* Parameter not evaluated yet, so go do it */
        ExecSetParamPlan(prm->execPlan, econtext);
        /* ExecSetParamPlan should have processed this param... */
        Assert(prm->execPlan == NULL);
    }
    *op->resvalue = prm->value;
    *op->resnull = prm->isnull;
}

/*
 * Evaluate a PARAM_EXTERN parameter.
 *
 * PARAM_EXTERN parameters must be sought in ecxt_param_list_info.
 */
void
ExecEvalParamExtern(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    ParamListInfo paramInfo = econtext->ecxt_param_list_info;
    int         paramId = op->d.param.paramid;

    if (likely(paramInfo &&
               paramId > 0 && paramId <= paramInfo->numParams))
    {
        ParamExternData *prm;
        ParamExternData prmdata;

        /* give hook a chance in case parameter is dynamic */
        if (paramInfo->paramFetch != NULL)
            prm = paramInfo->paramFetch(paramInfo, paramId, false, &prmdata);
        else
            prm = &paramInfo->params[paramId - 1];

        if (likely(OidIsValid(prm->ptype)))
        {
            /* safety check in case hook did something unexpected */
            if (unlikely(prm->ptype != op->d.param.paramtype))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("type of parameter %d (%s) does not match that when preparing the plan (%s)",
                                paramId,
                                format_type_be(prm->ptype),
                                format_type_be(op->d.param.paramtype))));
            *op->resvalue = prm->value;
            *op->resnull = prm->isnull;
            return;
        }
    }

    ereport(ERROR,
            (errcode(ERRCODE_UNDEFINED_OBJECT),
             errmsg("no value found for parameter %d", paramId)));
}

/*
 * Evaluate a SQLValueFunction expression.
 */
void
ExecEvalSQLValueFunction(ExprState *state, ExprEvalStep *op)
{
    LOCAL_FCINFO(fcinfo, 0);
    SQLValueFunction *svf = op->d.sqlvaluefunction.svf;

    *op->resnull = false;

    /*
     * Note: current_schema() can return NULL.  current_user() etc currently
     * cannot, but might as well code those cases the same way for safety.
     */
    switch (svf->op)
    {
        case SVFOP_CURRENT_DATE:
            *op->resvalue = DateADTGetDatum(GetSQLCurrentDate());
            break;
        case SVFOP_CURRENT_TIME:
        case SVFOP_CURRENT_TIME_N:
            *op->resvalue = TimeTzADTPGetDatum(GetSQLCurrentTime(svf->typmod));
            break;
        case SVFOP_CURRENT_TIMESTAMP:
        case SVFOP_CURRENT_TIMESTAMP_N:
            *op->resvalue = TimestampTzGetDatum(GetSQLCurrentTimestamp(svf->typmod));
            break;
        case SVFOP_LOCALTIME:
        case SVFOP_LOCALTIME_N:
            *op->resvalue = TimeADTGetDatum(GetSQLLocalTime(svf->typmod));
            break;
        case SVFOP_LOCALTIMESTAMP:
        case SVFOP_LOCALTIMESTAMP_N:
            *op->resvalue = TimestampGetDatum(GetSQLLocalTimestamp(svf->typmod));
            break;
        case SVFOP_CURRENT_ROLE:
        case SVFOP_CURRENT_USER:
        case SVFOP_USER:
            InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
            *op->resvalue = current_user(fcinfo);
            *op->resnull = fcinfo->isnull;
            break;
        case SVFOP_SESSION_USER:
            InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
            *op->resvalue = session_user(fcinfo);
            *op->resnull = fcinfo->isnull;
            break;
        case SVFOP_CURRENT_CATALOG:
            InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
            *op->resvalue = current_database(fcinfo);
            *op->resnull = fcinfo->isnull;
            break;
        case SVFOP_CURRENT_SCHEMA:
            InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
            *op->resvalue = current_schema(fcinfo);
            *op->resnull = fcinfo->isnull;
            break;
    }
}

/*
 * Raise error if a CURRENT OF expression is evaluated.
 *
 * The planner should convert CURRENT OF into a TidScan qualification, or some
 * other special handling in a ForeignScan node.  So we have to be able to do
 * ExecInitExpr on a CurrentOfExpr, but we shouldn't ever actually execute it.
 * If we get here, we suppose we must be dealing with CURRENT OF on a foreign
 * table whose FDW doesn't handle it, and complain accordingly.
 */
void
ExecEvalCurrentOfExpr(ExprState *state, ExprEvalStep *op)
{
    ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("WHERE CURRENT OF is not supported for this table type")));
}

/*
 * Evaluate NextValueExpr.
 */
void
ExecEvalNextValueExpr(ExprState *state, ExprEvalStep *op)
{
    int64       newval = nextval_internal(op->d.nextvalueexpr.seqid, false);

    switch (op->d.nextvalueexpr.seqtypid)
    {
        case INT2OID:
            *op->resvalue = Int16GetDatum((int16) newval);
            break;
        case INT4OID:
            *op->resvalue = Int32GetDatum((int32) newval);
            break;
        case INT8OID:
            *op->resvalue = Int64GetDatum((int64) newval);
            break;
        default:
            elog(ERROR, "unsupported sequence type %u",
                 op->d.nextvalueexpr.seqtypid);
    }
    *op->resnull = false;
}

/*
 * Evaluate NullTest / IS NULL for rows.
 */
void
ExecEvalRowNull(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    ExecEvalRowNullInt(state, op, econtext, true);
}

/*
 * Evaluate NullTest / IS NOT NULL for rows.
 */
void
ExecEvalRowNotNull(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    ExecEvalRowNullInt(state, op, econtext, false);
}

/* Common code for IS [NOT] NULL on a row value */
static void
ExecEvalRowNullInt(ExprState *state, ExprEvalStep *op,
                   ExprContext *econtext, bool checkisnull)
{
    Datum       value = *op->resvalue;
    bool        isnull = *op->resnull;
    HeapTupleHeader tuple;
    Oid         tupType;
    int32       tupTypmod;
    TupleDesc   tupDesc;
    HeapTupleData tmptup;

    *op->resnull = false;

    /* NULL row variables are treated just as NULL scalar columns */
    if (isnull)
    {
        *op->resvalue = BoolGetDatum(checkisnull);
        return;
    }

    /*
     * The SQL standard defines IS [NOT] NULL for a non-null rowtype argument
     * as:
     *
     * "R IS NULL" is true if every field is the null value.
     *
     * "R IS NOT NULL" is true if no field is the null value.
     *
     * This definition is (apparently intentionally) not recursive; so our
     * tests on the fields are primitive attisnull tests, not recursive checks
     * to see if they are all-nulls or no-nulls rowtypes.
     *
     * The standard does not consider the possibility of zero-field rows, but
     * here we consider them to vacuously satisfy both predicates.
     */

    tuple = DatumGetHeapTupleHeader(value);

    tupType = HeapTupleHeaderGetTypeId(tuple);
    tupTypmod = HeapTupleHeaderGetTypMod(tuple);

    /* Lookup tupdesc if first time through or if type changes */
    tupDesc = get_cached_rowtype(tupType, tupTypmod,
                                 &op->d.nulltest_row.argdesc,
                                 econtext);

    /*
     * heap_attisnull needs a HeapTuple not a bare HeapTupleHeader.
     */
    tmptup.t_len = HeapTupleHeaderGetDatumLength(tuple);
    tmptup.t_data = tuple;

    for (int att = 1; att <= tupDesc->natts; att++)
    {
        /* ignore dropped columns */
        if (TupleDescAttr(tupDesc, att - 1)->attisdropped)
            continue;
        if (heap_attisnull(&tmptup, att, tupDesc))
        {
            /* null field disproves IS NOT NULL */
            if (!checkisnull)
            {
                *op->resvalue = BoolGetDatum(false);
                return;
            }
        }
        else
        {
            /* non-null field disproves IS NULL */
            if (checkisnull)
            {
                *op->resvalue = BoolGetDatum(false);
                return;
            }
        }
    }

    *op->resvalue = BoolGetDatum(true);
}

/*
 * Evaluate an ARRAY[] expression.
 *
 * The individual array elements (or subarrays) have already been evaluated
 * into op->d.arrayexpr.elemvalues[]/elemnulls[].
 */
void
ExecEvalArrayExpr(ExprState *state, ExprEvalStep *op)
{
    ArrayType  *result;
    Oid         element_type = op->d.arrayexpr.elemtype;
    int         nelems = op->d.arrayexpr.nelems;
    int         ndims = 0;
    int         dims[MAXDIM];
    int         lbs[MAXDIM];

    /* Set non-null as default */
    *op->resnull = false;

    if (!op->d.arrayexpr.multidims)
    {
        /* Elements are presumably of scalar type */
        Datum      *dvalues = op->d.arrayexpr.elemvalues;
        bool       *dnulls = op->d.arrayexpr.elemnulls;

        /* setup for 1-D array of the given length */
        ndims = 1;
        dims[0] = nelems;
        lbs[0] = 1;

        result = construct_md_array(dvalues, dnulls, ndims, dims, lbs,
                                    element_type,
                                    op->d.arrayexpr.elemlength,
                                    op->d.arrayexpr.elembyval,
                                    op->d.arrayexpr.elemalign);
    }
    else
    {
        /* Must be nested array expressions */
        int         nbytes = 0;
        int         nitems = 0;
        int         outer_nelems = 0;
        int         elem_ndims = 0;
        int        *elem_dims = NULL;
        int        *elem_lbs = NULL;
        bool        firstone = true;
        bool        havenulls = false;
        bool        haveempty = false;
        char      **subdata;
        bits8     **subbitmaps;
        int        *subbytes;
        int        *subnitems;
        int32       dataoffset;
        char       *dat;
        int         iitem;

        subdata = (char **) palloc(nelems * sizeof(char *));
        subbitmaps = (bits8 **) palloc(nelems * sizeof(bits8 *));
        subbytes = (int *) palloc(nelems * sizeof(int));
        subnitems = (int *) palloc(nelems * sizeof(int));

        /* loop through and get data area from each element */
        for (int elemoff = 0; elemoff < nelems; elemoff++)
        {
            Datum       arraydatum;
            bool        eisnull;
            ArrayType  *array;
            int         this_ndims;

            arraydatum = op->d.arrayexpr.elemvalues[elemoff];
            eisnull = op->d.arrayexpr.elemnulls[elemoff];

            /* temporarily ignore null subarrays */
            if (eisnull)
            {
                haveempty = true;
                continue;
            }

            array = DatumGetArrayTypeP(arraydatum);

            /* run-time double-check on element type */
            if (element_type != ARR_ELEMTYPE(array))
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("cannot merge incompatible arrays"),
                         errdetail("Array with element type %s cannot be "
                                   "included in ARRAY construct with element type %s.",
                                   format_type_be(ARR_ELEMTYPE(array)),
                                   format_type_be(element_type))));

            this_ndims = ARR_NDIM(array);
            /* temporarily ignore zero-dimensional subarrays */
            if (this_ndims <= 0)
            {
                haveempty = true;
                continue;
            }

            if (firstone)
            {
                /* Get sub-array details from first member */
                elem_ndims = this_ndims;
                ndims = elem_ndims + 1;
                if (ndims <= 0 || ndims > MAXDIM)
                    ereport(ERROR,
                            (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                             errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
                                    ndims, MAXDIM)));

                elem_dims = (int *) palloc(elem_ndims * sizeof(int));
                memcpy(elem_dims, ARR_DIMS(array), elem_ndims * sizeof(int));
                elem_lbs = (int *) palloc(elem_ndims * sizeof(int));
                memcpy(elem_lbs, ARR_LBOUND(array), elem_ndims * sizeof(int));

                firstone = false;
            }
            else
            {
                /* Check other sub-arrays are compatible */
                if (elem_ndims != this_ndims ||
                    memcmp(elem_dims, ARR_DIMS(array),
                           elem_ndims * sizeof(int)) != 0 ||
                    memcmp(elem_lbs, ARR_LBOUND(array),
                           elem_ndims * sizeof(int)) != 0)
                    ereport(ERROR,
                            (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                             errmsg("multidimensional arrays must have array "
                                    "expressions with matching dimensions")));
            }

            subdata[outer_nelems] = ARR_DATA_PTR(array);
            subbitmaps[outer_nelems] = ARR_NULLBITMAP(array);
            subbytes[outer_nelems] = ARR_SIZE(array) - ARR_DATA_OFFSET(array);
            nbytes += subbytes[outer_nelems];
            subnitems[outer_nelems] = ArrayGetNItems(this_ndims,
                                                     ARR_DIMS(array));
            nitems += subnitems[outer_nelems];
            havenulls |= ARR_HASNULL(array);
            outer_nelems++;
        }

        /*
         * If all items were null or empty arrays, return an empty array;
         * otherwise, if some were and some weren't, raise error.  (Note: we
         * must special-case this somehow to avoid trying to generate a 1-D
         * array formed from empty arrays.  It's not ideal...)
         */
        if (haveempty)
        {
            if (ndims == 0)     /* didn't find any nonempty array */
            {
                *op->resvalue = PointerGetDatum(construct_empty_array(element_type));
                return;
            }
            ereport(ERROR,
                    (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                     errmsg("multidimensional arrays must have array "
                            "expressions with matching dimensions")));
        }

        /* setup for multi-D array */
        dims[0] = outer_nelems;
        lbs[0] = 1;
        for (int i = 1; i < ndims; i++)
        {
            dims[i] = elem_dims[i - 1];
            lbs[i] = elem_lbs[i - 1];
        }

        if (havenulls)
        {
            dataoffset = ARR_OVERHEAD_WITHNULLS(ndims, nitems);
            nbytes += dataoffset;
        }
        else
        {
            dataoffset = 0;     /* marker for no null bitmap */
            nbytes += ARR_OVERHEAD_NONULLS(ndims);
        }

        result = (ArrayType *) palloc(nbytes);
        SET_VARSIZE(result, nbytes);
        result->ndim = ndims;
        result->dataoffset = dataoffset;
        result->elemtype = element_type;
        memcpy(ARR_DIMS(result), dims, ndims * sizeof(int));
        memcpy(ARR_LBOUND(result), lbs, ndims * sizeof(int));

        dat = ARR_DATA_PTR(result);
        iitem = 0;
        for (int i = 0; i < outer_nelems; i++)
        {
            memcpy(dat, subdata[i], subbytes[i]);
            dat += subbytes[i];
            if (havenulls)
                array_bitmap_copy(ARR_NULLBITMAP(result), iitem,
                                  subbitmaps[i], 0,
                                  subnitems[i]);
            iitem += subnitems[i];
        }
    }

    *op->resvalue = PointerGetDatum(result);
}

/*
 * Evaluate an ArrayCoerceExpr expression.
 *
 * Source array is in step's result variable.
 */
void
ExecEvalArrayCoerce(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    Datum       arraydatum;

    /* NULL array -> NULL result */
    if (*op->resnull)
        return;

    arraydatum = *op->resvalue;

    /*
     * If it's binary-compatible, modify the element type in the array header,
     * but otherwise leave the array as we received it.
     */
    if (op->d.arraycoerce.elemexprstate == NULL)
    {
        /* Detoast input array if necessary, and copy in any case */
        ArrayType  *array = DatumGetArrayTypePCopy(arraydatum);

        ARR_ELEMTYPE(array) = op->d.arraycoerce.resultelemtype;
        *op->resvalue = PointerGetDatum(array);
        return;
    }

    /*
     * Use array_map to apply the sub-expression to each array element.
     */
    *op->resvalue = array_map(arraydatum,
                              op->d.arraycoerce.elemexprstate,
                              econtext,
                              op->d.arraycoerce.resultelemtype,
                              op->d.arraycoerce.amstate);
}

/*
 * Evaluate a ROW() expression.
 *
 * The individual columns have already been evaluated into
 * op->d.row.elemvalues[]/elemnulls[].
 */
void
ExecEvalRow(ExprState *state, ExprEvalStep *op)
{
    HeapTuple   tuple;

    /* build tuple from evaluated field values */
    tuple = heap_form_tuple(op->d.row.tupdesc,
                            op->d.row.elemvalues,
                            op->d.row.elemnulls);

    *op->resvalue = HeapTupleGetDatum(tuple);
    *op->resnull = false;
}

/*
 * Evaluate GREATEST() or LEAST() expression (note this is *not* MIN()/MAX()).
 *
 * All of the to-be-compared expressions have already been evaluated into
 * op->d.minmax.values[]/nulls[].
 */
void
ExecEvalMinMax(ExprState *state, ExprEvalStep *op)
{
    Datum      *values = op->d.minmax.values;
    bool       *nulls = op->d.minmax.nulls;
    FunctionCallInfo fcinfo = op->d.minmax.fcinfo_data;
    MinMaxOp    operator = op->d.minmax.op;

    /* set at initialization */
    Assert(fcinfo->args[0].isnull == false);
    Assert(fcinfo->args[1].isnull == false);

    /* default to null result */
    *op->resnull = true;

    for (int off = 0; off < op->d.minmax.nelems; off++)
    {
        /* ignore NULL inputs */
        if (nulls[off])
            continue;

        if (*op->resnull)
        {
            /* first nonnull input, adopt value */
            *op->resvalue = values[off];
            *op->resnull = false;
        }
        else
        {
            int         cmpresult;

            /* apply comparison function */
            fcinfo->args[0].value = *op->resvalue;
            fcinfo->args[1].value = values[off];

            fcinfo->isnull = false;
            cmpresult = DatumGetInt32(FunctionCallInvoke(fcinfo));
            if (fcinfo->isnull) /* probably should not happen */
                continue;

            if (cmpresult > 0 && operator == IS_LEAST)
                *op->resvalue = values[off];
            else if (cmpresult < 0 && operator == IS_GREATEST)
                *op->resvalue = values[off];
        }
    }
}

/*
 * Evaluate a FieldSelect node.
 *
 * Source record is in step's result variable.
 */
void
ExecEvalFieldSelect(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    AttrNumber  fieldnum = op->d.fieldselect.fieldnum;
    Datum       tupDatum;
    HeapTupleHeader tuple;
    Oid         tupType;
    int32       tupTypmod;
    TupleDesc   tupDesc;
    Form_pg_attribute attr;
    HeapTupleData tmptup;

    /* NULL record -> NULL result */
    if (*op->resnull)
        return;

    tupDatum = *op->resvalue;

    /* We can special-case expanded records for speed */
    if (VARATT_IS_EXTERNAL_EXPANDED(DatumGetPointer(tupDatum)))
    {
        ExpandedRecordHeader *erh = (ExpandedRecordHeader *) DatumGetEOHP(tupDatum);

        Assert(erh->er_magic == ER_MAGIC);

        /* Extract record's TupleDesc */
        tupDesc = expanded_record_get_tupdesc(erh);

        /*
         * Find field's attr record.  Note we don't support system columns
         * here: a datum tuple doesn't have valid values for most of the
         * interesting system columns anyway.
         */
        if (fieldnum <= 0)      /* should never happen */
            elog(ERROR, "unsupported reference to system column %d in FieldSelect",
                 fieldnum);
        if (fieldnum > tupDesc->natts)  /* should never happen */
            elog(ERROR, "attribute number %d exceeds number of columns %d",
                 fieldnum, tupDesc->natts);
        attr = TupleDescAttr(tupDesc, fieldnum - 1);

        /* Check for dropped column, and force a NULL result if so */
        if (attr->attisdropped)
        {
            *op->resnull = true;
            return;
        }

        /* Check for type mismatch --- possible after ALTER COLUMN TYPE? */
        /* As in CheckVarSlotCompatibility, we should but can't check typmod */
        if (op->d.fieldselect.resulttype != attr->atttypid)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("attribute %d has wrong type", fieldnum),
                     errdetail("Table has type %s, but query expects %s.",
                               format_type_be(attr->atttypid),
                               format_type_be(op->d.fieldselect.resulttype))));

        /* extract the field */
        *op->resvalue = expanded_record_get_field(erh, fieldnum,
                                                  op->resnull);
    }
    else
    {
        /* Get the composite datum and extract its type fields */
        tuple = DatumGetHeapTupleHeader(tupDatum);

        tupType = HeapTupleHeaderGetTypeId(tuple);
        tupTypmod = HeapTupleHeaderGetTypMod(tuple);

        /* Lookup tupdesc if first time through or if type changes */
        tupDesc = get_cached_rowtype(tupType, tupTypmod,
                                     &op->d.fieldselect.argdesc,
                                     econtext);

        /*
         * Find field's attr record.  Note we don't support system columns
         * here: a datum tuple doesn't have valid values for most of the
         * interesting system columns anyway.
         */
        if (fieldnum <= 0)      /* should never happen */
            elog(ERROR, "unsupported reference to system column %d in FieldSelect",
                 fieldnum);
        if (fieldnum > tupDesc->natts)  /* should never happen */
            elog(ERROR, "attribute number %d exceeds number of columns %d",
                 fieldnum, tupDesc->natts);
        attr = TupleDescAttr(tupDesc, fieldnum - 1);

        /* Check for dropped column, and force a NULL result if so */
        if (attr->attisdropped)
        {
            *op->resnull = true;
            return;
        }

        /* Check for type mismatch --- possible after ALTER COLUMN TYPE? */
        /* As in CheckVarSlotCompatibility, we should but can't check typmod */
        if (op->d.fieldselect.resulttype != attr->atttypid)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("attribute %d has wrong type", fieldnum),
                     errdetail("Table has type %s, but query expects %s.",
                               format_type_be(attr->atttypid),
                               format_type_be(op->d.fieldselect.resulttype))));

        /* heap_getattr needs a HeapTuple not a bare HeapTupleHeader */
        tmptup.t_len = HeapTupleHeaderGetDatumLength(tuple);
        tmptup.t_data = tuple;

        /* extract the field */
        *op->resvalue = heap_getattr(&tmptup,
                                     fieldnum,
                                     tupDesc,
                                     op->resnull);
    }
}

/*
 * Deform source tuple, filling in the step's values/nulls arrays, before
 * evaluating individual new values as part of a FieldStore expression.
 * Subsequent steps will overwrite individual elements of the values/nulls
 * arrays with the new field values, and then FIELDSTORE_FORM will build the
 * new tuple value.
 *
 * Source record is in step's result variable.
 */
void
ExecEvalFieldStoreDeForm(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    TupleDesc   tupDesc;

    /* Lookup tupdesc if first time through or after rescan */
    tupDesc = get_cached_rowtype(op->d.fieldstore.fstore->resulttype, -1,
                                 op->d.fieldstore.argdesc, econtext);

    /* Check that current tupdesc doesn't have more fields than we allocated */
    if (unlikely(tupDesc->natts > op->d.fieldstore.ncolumns))
        elog(ERROR, "too many columns in composite type %u",
             op->d.fieldstore.fstore->resulttype);

    if (*op->resnull)
    {
        /* Convert null input tuple into an all-nulls row */
        memset(op->d.fieldstore.nulls, true,
               op->d.fieldstore.ncolumns * sizeof(bool));
    }
    else
    {
        /*
         * heap_deform_tuple needs a HeapTuple not a bare HeapTupleHeader. We
         * set all the fields in the struct just in case.
         */
        Datum       tupDatum = *op->resvalue;
        HeapTupleHeader tuphdr;
        HeapTupleData tmptup;

        tuphdr = DatumGetHeapTupleHeader(tupDatum);
        tmptup.t_len = HeapTupleHeaderGetDatumLength(tuphdr);
        ItemPointerSetInvalid(&(tmptup.t_self));
        tmptup.t_tableOid = InvalidOid;
        tmptup.t_data = tuphdr;

        heap_deform_tuple(&tmptup, tupDesc,
                          op->d.fieldstore.values,
                          op->d.fieldstore.nulls);
    }
}

/*
 * Compute the new composite datum after each individual field value of a
 * FieldStore expression has been evaluated.
 */
void
ExecEvalFieldStoreForm(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    HeapTuple   tuple;

    /* argdesc should already be valid from the DeForm step */
    tuple = heap_form_tuple(*op->d.fieldstore.argdesc,
                            op->d.fieldstore.values,
                            op->d.fieldstore.nulls);

    *op->resvalue = HeapTupleGetDatum(tuple);
    *op->resnull = false;
}

/*
 * Evaluate a rowtype coercion operation.
 * This may require rearranging field positions.
 *
 * Source record is in step's result variable.
 */
void
ExecEvalConvertRowtype(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    ConvertRowtypeExpr *convert = op->d.convert_rowtype.convert;
    HeapTuple   result;
    Datum       tupDatum;
    HeapTupleHeader tuple;
    HeapTupleData tmptup;
    TupleDesc   indesc,
                outdesc;

    /* NULL in -> NULL out */
    if (*op->resnull)
        return;

    tupDatum = *op->resvalue;
    tuple = DatumGetHeapTupleHeader(tupDatum);

    /* Lookup tupdescs if first time through or after rescan */
    if (op->d.convert_rowtype.indesc == NULL)
    {
        get_cached_rowtype(exprType((Node *) convert->arg), -1,
                           &op->d.convert_rowtype.indesc,
                           econtext);
        op->d.convert_rowtype.initialized = false;
    }
    if (op->d.convert_rowtype.outdesc == NULL)
    {
        get_cached_rowtype(convert->resulttype, -1,
                           &op->d.convert_rowtype.outdesc,
                           econtext);
        op->d.convert_rowtype.initialized = false;
    }

    indesc = op->d.convert_rowtype.indesc;
    outdesc = op->d.convert_rowtype.outdesc;

    /*
     * We used to be able to assert that incoming tuples are marked with
     * exactly the rowtype of indesc.  However, now that ExecEvalWholeRowVar
     * might change the tuples' marking to plain RECORD due to inserting
     * aliases, we can only make this weak test:
     */
    Assert(HeapTupleHeaderGetTypeId(tuple) == indesc->tdtypeid ||
           HeapTupleHeaderGetTypeId(tuple) == RECORDOID);

    /* if first time through, initialize conversion map */
    if (!op->d.convert_rowtype.initialized)
    {
        MemoryContext old_cxt;

        /* allocate map in long-lived memory context */
        old_cxt = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);

        /* prepare map from old to new attribute numbers */
        op->d.convert_rowtype.map = convert_tuples_by_name(indesc, outdesc);
        op->d.convert_rowtype.initialized = true;

        MemoryContextSwitchTo(old_cxt);
    }

    /* Following steps need a HeapTuple not a bare HeapTupleHeader */
    tmptup.t_len = HeapTupleHeaderGetDatumLength(tuple);
    tmptup.t_data = tuple;

    if (op->d.convert_rowtype.map != NULL)
    {
        /* Full conversion with attribute rearrangement needed */
        result = execute_attr_map_tuple(&tmptup, op->d.convert_rowtype.map);
        /* Result already has appropriate composite-datum header fields */
        *op->resvalue = HeapTupleGetDatum(result);
    }
    else
    {
        /*
         * The tuple is physically compatible as-is, but we need to insert the
         * destination rowtype OID in its composite-datum header field, so we
         * have to copy it anyway.  heap_copy_tuple_as_datum() is convenient
         * for this since it will both make the physical copy and insert the
         * correct composite header fields.  Note that we aren't expecting to
         * have to flatten any toasted fields: the input was a composite
         * datum, so it shouldn't contain any.  So heap_copy_tuple_as_datum()
         * is overkill here, but its check for external fields is cheap.
         */
        *op->resvalue = heap_copy_tuple_as_datum(&tmptup, outdesc);
    }
}

/*
 * Evaluate "scalar op ANY/ALL (array)".
 *
 * Source array is in our result area, scalar arg is already evaluated into
 * fcinfo->args[0].
 *
 * The operator always yields boolean, and we combine the results across all
 * array elements using OR and AND (for ANY and ALL respectively).  Of course
 * we short-circuit as soon as the result is known.
 */
void
ExecEvalScalarArrayOp(ExprState *state, ExprEvalStep *op)
{
    FunctionCallInfo fcinfo = op->d.scalararrayop.fcinfo_data;
    bool        useOr = op->d.scalararrayop.useOr;
    bool        strictfunc = op->d.scalararrayop.finfo->fn_strict;
    ArrayType  *arr;
    int         nitems;
    Datum       result;
    bool        resultnull;
    int16       typlen;
    bool        typbyval;
    char        typalign;
    char       *s;
    bits8      *bitmap;
    int         bitmask;

    /*
     * If the array is NULL then we return NULL --- it's not very meaningful
     * to do anything else, even if the operator isn't strict.
     */
    if (*op->resnull)
        return;

    /* Else okay to fetch and detoast the array */
    arr = DatumGetArrayTypeP(*op->resvalue);

    /*
     * If the array is empty, we return either FALSE or TRUE per the useOr
     * flag.  This is correct even if the scalar is NULL; since we would
     * evaluate the operator zero times, it matters not whether it would want
     * to return NULL.
     */
    nitems = ArrayGetNItems(ARR_NDIM(arr), ARR_DIMS(arr));
    if (nitems <= 0)
    {
        *op->resvalue = BoolGetDatum(!useOr);
        *op->resnull = false;
        return;
    }

    /*
     * If the scalar is NULL, and the function is strict, return NULL; no
     * point in iterating the loop.
     */
    if (fcinfo->args[0].isnull && strictfunc)
    {
        *op->resnull = true;
        return;
    }

    /*
     * We arrange to look up info about the element type only once per series
     * of calls, assuming the element type doesn't change underneath us.
     */
    if (op->d.scalararrayop.element_type != ARR_ELEMTYPE(arr))
    {
        get_typlenbyvalalign(ARR_ELEMTYPE(arr),
                             &op->d.scalararrayop.typlen,
                             &op->d.scalararrayop.typbyval,
                             &op->d.scalararrayop.typalign);
        op->d.scalararrayop.element_type = ARR_ELEMTYPE(arr);
    }

    typlen = op->d.scalararrayop.typlen;
    typbyval = op->d.scalararrayop.typbyval;
    typalign = op->d.scalararrayop.typalign;

    /* Initialize result appropriately depending on useOr */
    result = BoolGetDatum(!useOr);
    resultnull = false;

    /* Loop over the array elements */
    s = (char *) ARR_DATA_PTR(arr);
    bitmap = ARR_NULLBITMAP(arr);
    bitmask = 1;

    for (int i = 0; i < nitems; i++)
    {
        Datum       elt;
        Datum       thisresult;

        /* Get array element, checking for NULL */
        if (bitmap && (*bitmap & bitmask) == 0)
        {
            fcinfo->args[1].value = (Datum) 0;
            fcinfo->args[1].isnull = true;
        }
        else
        {
            elt = fetch_att(s, typbyval, typlen);
            s = att_addlength_pointer(s, typlen, s);
            s = (char *) att_align_nominal(s, typalign);
            fcinfo->args[1].value = elt;
            fcinfo->args[1].isnull = false;
        }

        /* Call comparison function */
        if (fcinfo->args[1].isnull && strictfunc)
        {
            fcinfo->isnull = true;
            thisresult = (Datum) 0;
        }
        else
        {
            fcinfo->isnull = false;
            thisresult = op->d.scalararrayop.fn_addr(fcinfo);
        }

        /* Combine results per OR or AND semantics */
        if (fcinfo->isnull)
            resultnull = true;
        else if (useOr)
        {
            if (DatumGetBool(thisresult))
            {
                result = BoolGetDatum(true);
                resultnull = false;
                break;          /* needn't look at any more elements */
            }
        }
        else
        {
            if (!DatumGetBool(thisresult))
            {
                result = BoolGetDatum(false);
                resultnull = false;
                break;          /* needn't look at any more elements */
            }
        }

        /* advance bitmap pointer if any */
        if (bitmap)
        {
            bitmask <<= 1;
            if (bitmask == 0x100)
            {
                bitmap++;
                bitmask = 1;
            }
        }
    }

    *op->resvalue = result;
    *op->resnull = resultnull;
}

/*
 * Evaluate a NOT NULL domain constraint.
 */
void
ExecEvalConstraintNotNull(ExprState *state, ExprEvalStep *op)
{
    if (*op->resnull)
        ereport(ERROR,
                (errcode(ERRCODE_NOT_NULL_VIOLATION),
                 errmsg("domain %s does not allow null values",
                        format_type_be(op->d.domaincheck.resulttype)),
                 errdatatype(op->d.domaincheck.resulttype)));
}

/*
 * Evaluate a CHECK domain constraint.
 */
void
ExecEvalConstraintCheck(ExprState *state, ExprEvalStep *op)
{
    if (!*op->d.domaincheck.checknull &&
        !DatumGetBool(*op->d.domaincheck.checkvalue))
        ereport(ERROR,
                (errcode(ERRCODE_CHECK_VIOLATION),
                 errmsg("value for domain %s violates check constraint \"%s\"",
                        format_type_be(op->d.domaincheck.resulttype),
                        op->d.domaincheck.constraintname),
                 errdomainconstraint(op->d.domaincheck.resulttype,
                                     op->d.domaincheck.constraintname)));
}

/*
 * Evaluate the various forms of XmlExpr.
 *
 * Arguments have been evaluated into named_argvalue/named_argnull
 * and/or argvalue/argnull arrays.
 */
void
ExecEvalXmlExpr(ExprState *state, ExprEvalStep *op)
{
    XmlExpr    *xexpr = op->d.xmlexpr.xexpr;
    Datum       value;

    *op->resnull = true;        /* until we get a result */
    *op->resvalue = (Datum) 0;

    switch (xexpr->op)
    {
        case IS_XMLCONCAT:
            {
                Datum      *argvalue = op->d.xmlexpr.argvalue;
                bool       *argnull = op->d.xmlexpr.argnull;
                List       *values = NIL;

                for (int i = 0; i < list_length(xexpr->args); i++)
                {
                    if (!argnull[i])
                        values = lappend(values, DatumGetPointer(argvalue[i]));
                }

                if (values != NIL)
                {
                    *op->resvalue = PointerGetDatum(xmlconcat(values));
                    *op->resnull = false;
                }
            }
            break;

        case IS_XMLFOREST:
            {
                Datum      *argvalue = op->d.xmlexpr.named_argvalue;
                bool       *argnull = op->d.xmlexpr.named_argnull;
                StringInfoData buf;
                ListCell   *lc;
                ListCell   *lc2;
                int         i;

                initStringInfo(&buf);

                i = 0;
                forboth(lc, xexpr->named_args, lc2, xexpr->arg_names)
                {
                    Expr       *e = (Expr *) lfirst(lc);
                    char       *argname = strVal(lfirst(lc2));

                    if (!argnull[i])
                    {
                        value = argvalue[i];
                        appendStringInfo(&buf, "<%s>%s</%s>",
                                         argname,
                                         map_sql_value_to_xml_value(value,
                                                                    exprType((Node *) e), true),
                                         argname);
                        *op->resnull = false;
                    }
                    i++;
                }

                if (!*op->resnull)
                {
                    text       *result;

                    result = cstring_to_text_with_len(buf.data, buf.len);
                    *op->resvalue = PointerGetDatum(result);
                }

                pfree(buf.data);
            }
            break;

        case IS_XMLELEMENT:
            *op->resvalue = PointerGetDatum(xmlelement(xexpr,
                                                       op->d.xmlexpr.named_argvalue,
                                                       op->d.xmlexpr.named_argnull,
                                                       op->d.xmlexpr.argvalue,
                                                       op->d.xmlexpr.argnull));
            *op->resnull = false;
            break;

        case IS_XMLPARSE:
            {
                Datum      *argvalue = op->d.xmlexpr.argvalue;
                bool       *argnull = op->d.xmlexpr.argnull;
                text       *data;
                bool        preserve_whitespace;

                /* arguments are known to be text, bool */
                Assert(list_length(xexpr->args) == 2);

                if (argnull[0])
                    return;
                value = argvalue[0];
                data = DatumGetTextPP(value);

                if (argnull[1]) /* probably can't happen */
                    return;
                value = argvalue[1];
                preserve_whitespace = DatumGetBool(value);

                *op->resvalue = PointerGetDatum(xmlparse(data,
                                                         xexpr->xmloption,
                                                         preserve_whitespace));
                *op->resnull = false;
            }
            break;

        case IS_XMLPI:
            {
                text       *arg;
                bool        isnull;

                /* optional argument is known to be text */
                Assert(list_length(xexpr->args) <= 1);

                if (xexpr->args)
                {
                    isnull = op->d.xmlexpr.argnull[0];
                    if (isnull)
                        arg = NULL;
                    else
                        arg = DatumGetTextPP(op->d.xmlexpr.argvalue[0]);
                }
                else
                {
                    arg = NULL;
                    isnull = false;
                }

                *op->resvalue = PointerGetDatum(xmlpi(xexpr->name,
                                                      arg,
                                                      isnull,
                                                      op->resnull));
            }
            break;

        case IS_XMLROOT:
            {
                Datum      *argvalue = op->d.xmlexpr.argvalue;
                bool       *argnull = op->d.xmlexpr.argnull;
                xmltype    *data;
                text       *version;
                int         standalone;

                /* arguments are known to be xml, text, int */
                Assert(list_length(xexpr->args) == 3);

                if (argnull[0])
                    return;
                data = DatumGetXmlP(argvalue[0]);

                if (argnull[1])
                    version = NULL;
                else
                    version = DatumGetTextPP(argvalue[1]);

                Assert(!argnull[2]);    /* always present */
                standalone = DatumGetInt32(argvalue[2]);

                *op->resvalue = PointerGetDatum(xmlroot(data,
                                                        version,
                                                        standalone));
                *op->resnull = false;
            }
            break;

        case IS_XMLSERIALIZE:
            {
                Datum      *argvalue = op->d.xmlexpr.argvalue;
                bool       *argnull = op->d.xmlexpr.argnull;

                /* argument type is known to be xml */
                Assert(list_length(xexpr->args) == 1);

                if (argnull[0])
                    return;
                value = argvalue[0];

                *op->resvalue = PointerGetDatum(xmltotext_with_xmloption(DatumGetXmlP(value),
                                                                         xexpr->xmloption));
                *op->resnull = false;
            }
            break;

        case IS_DOCUMENT:
            {
                Datum      *argvalue = op->d.xmlexpr.argvalue;
                bool       *argnull = op->d.xmlexpr.argnull;

                /* optional argument is known to be xml */
                Assert(list_length(xexpr->args) == 1);

                if (argnull[0])
                    return;
                value = argvalue[0];

                *op->resvalue =
                    BoolGetDatum(xml_is_document(DatumGetXmlP(value)));
                *op->resnull = false;
            }
            break;

        default:
            elog(ERROR, "unrecognized XML operation");
            break;
    }
}

/*
 * ExecEvalGroupingFunc
 *
 * Computes a bitmask with a bit for each (unevaluated) argument expression
 * (rightmost arg is least significant bit).
 *
 * A bit is set if the corresponding expression is NOT part of the set of
 * grouping expressions in the current grouping set.
 */
void
ExecEvalGroupingFunc(ExprState *state, ExprEvalStep *op)
{
    AggState   *aggstate = castNode(AggState, state->parent);
    int         result = 0;
    Bitmapset  *grouped_cols = aggstate->grouped_cols;
    ListCell   *lc;

    foreach(lc, op->d.grouping_func.clauses)
    {
        int         attnum = lfirst_int(lc);

        result <<= 1;

        if (!bms_is_member(attnum, grouped_cols))
            result |= 1;
    }

    *op->resvalue = Int32GetDatum(result);
    *op->resnull = false;
}

/*
 * Hand off evaluation of a subplan to nodeSubplan.c
 */
void
ExecEvalSubPlan(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    SubPlanState *sstate = op->d.subplan.sstate;

    /* could potentially be nested, so make sure there's enough stack */
    check_stack_depth();

    *op->resvalue = ExecSubPlan(sstate, econtext, op->resnull);
}

/*
 * Evaluate a wholerow Var expression.
 *
 * Returns a Datum whose value is the value of a whole-row range variable
 * with respect to given expression context.
 */
void
ExecEvalWholeRowVar(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
{
    Var        *variable = op->d.wholerow.var;
    TupleTableSlot *slot;
    TupleDesc   output_tupdesc;
    MemoryContext oldcontext;
    HeapTupleHeader dtuple;
    HeapTuple   tuple;

    /* This was checked by ExecInitExpr */
    Assert(variable->varattno == InvalidAttrNumber);

    /* Get the input slot we want */
    switch (variable->varno)
    {
        case INNER_VAR:
            /* get the tuple from the inner node */
            slot = econtext->ecxt_innertuple;
            break;

        case OUTER_VAR:
            /* get the tuple from the outer node */
            slot = econtext->ecxt_outertuple;
            break;

            /* INDEX_VAR is handled by default case */

        default:
            /* get the tuple from the relation being scanned */
            slot = econtext->ecxt_scantuple;
            break;
    }

    /* Apply the junkfilter if any */
    if (op->d.wholerow.junkFilter != NULL)
        slot = ExecFilterJunk(op->d.wholerow.junkFilter, slot);

    /*
     * If first time through, obtain tuple descriptor and check compatibility.
     *
     * XXX: It'd be great if this could be moved to the expression
     * initialization phase, but due to using slots that's currently not
     * feasible.
     */
    if (op->d.wholerow.first)
    {
        /* optimistically assume we don't need slow path */
        op->d.wholerow.slow = false;

        /*
         * If the Var identifies a named composite type, we must check that
         * the actual tuple type is compatible with it.
         */
        if (variable->vartype != RECORDOID)
        {
            TupleDesc   var_tupdesc;
            TupleDesc   slot_tupdesc;

            /*
             * We really only care about numbers of attributes and data types.
             * Also, we can ignore type mismatch on columns that are dropped
             * in the destination type, so long as (1) the physical storage
             * matches or (2) the actual column value is NULL.  Case (1) is
             * helpful in some cases involving out-of-date cached plans, while
             * case (2) is expected behavior in situations such as an INSERT
             * into a table with dropped columns (the planner typically
             * generates an INT4 NULL regardless of the dropped column type).
             * If we find a dropped column and cannot verify that case (1)
             * holds, we have to use the slow path to check (2) for each row.
             *
             * If vartype is a domain over composite, just look through that
             * to the base composite type.
             */
            var_tupdesc = lookup_rowtype_tupdesc_domain(variable->vartype,
                                                        -1, false);

            slot_tupdesc = slot->tts_tupleDescriptor;

            if (var_tupdesc->natts != slot_tupdesc->natts)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("table row type and query-specified row type do not match"),
                         errdetail_plural("Table row contains %d attribute, but query expects %d.",
                                          "Table row contains %d attributes, but query expects %d.",
                                          slot_tupdesc->natts,
                                          slot_tupdesc->natts,
                                          var_tupdesc->natts)));

            for (int i = 0; i < var_tupdesc->natts; i++)
            {
                Form_pg_attribute vattr = TupleDescAttr(var_tupdesc, i);
                Form_pg_attribute sattr = TupleDescAttr(slot_tupdesc, i);

                if (vattr->atttypid == sattr->atttypid)
                    continue;   /* no worries */
                if (!vattr->attisdropped)
                    ereport(ERROR,
                            (errcode(ERRCODE_DATATYPE_MISMATCH),
                             errmsg("table row type and query-specified row type do not match"),
                             errdetail("Table has type %s at ordinal position %d, but query expects %s.",
                                       format_type_be(sattr->atttypid),
                                       i + 1,
                                       format_type_be(vattr->atttypid))));

                if (vattr->attlen != sattr->attlen ||
                    vattr->attalign != sattr->attalign)
                    op->d.wholerow.slow = true; /* need to check for nulls */
            }

            /*
             * Use the variable's declared rowtype as the descriptor for the
             * output values, modulo possibly assigning new column names
             * below. In particular, we *must* absorb any attisdropped
             * markings.
             */
            oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
            output_tupdesc = CreateTupleDescCopy(var_tupdesc);
            MemoryContextSwitchTo(oldcontext);

            ReleaseTupleDesc(var_tupdesc);
        }
        else
        {
            /*
             * In the RECORD case, we use the input slot's rowtype as the
             * descriptor for the output values, modulo possibly assigning new
             * column names below.
             */
            oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
            output_tupdesc = CreateTupleDescCopy(slot->tts_tupleDescriptor);
            MemoryContextSwitchTo(oldcontext);
        }

        /*
         * Construct a tuple descriptor for the composite values we'll
         * produce, and make sure its record type is "blessed".  The main
         * reason to do this is to be sure that operations such as
         * row_to_json() will see the desired column names when they look up
         * the descriptor from the type information embedded in the composite
         * values.
         *
         * We already got the correct physical datatype info above, but now we
         * should try to find the source RTE and adopt its column aliases, in
         * case they are different from the original rowtype's names.  For
         * example, in "SELECT foo(t) FROM tab t(x,y)", the first two columns
         * in the composite output should be named "x" and "y" regardless of
         * tab's column names.
         *
         * If we can't locate the RTE, assume the column names we've got are
         * OK.  (As of this writing, the only cases where we can't locate the
         * RTE are in execution of trigger WHEN clauses, and then the Var will
         * have the trigger's relation's rowtype, so its names are fine.)
         * Also, if the creator of the RTE didn't bother to fill in an eref
         * field, assume our column names are OK.  (This happens in COPY, and
         * perhaps other places.)
         */
        if (econtext->ecxt_estate &&
            variable->varno <= econtext->ecxt_estate->es_range_table_size)
        {
            RangeTblEntry *rte = exec_rt_fetch(variable->varno,
                                               econtext->ecxt_estate);

            if (rte->eref)
                ExecTypeSetColNames(output_tupdesc, rte->eref->colnames);
        }

        /* Bless the tupdesc if needed, and save it in the execution state */
        op->d.wholerow.tupdesc = BlessTupleDesc(output_tupdesc);

        op->d.wholerow.first = false;
    }

    /*
     * Make sure all columns of the slot are accessible in the slot's
     * Datum/isnull arrays.
     */
    slot_getallattrs(slot);

    if (op->d.wholerow.slow)
    {
        /* Check to see if any dropped attributes are non-null */
        TupleDesc   tupleDesc = slot->tts_tupleDescriptor;
        TupleDesc   var_tupdesc = op->d.wholerow.tupdesc;

        Assert(var_tupdesc->natts == tupleDesc->natts);

        for (int i = 0; i < var_tupdesc->natts; i++)
        {
            Form_pg_attribute vattr = TupleDescAttr(var_tupdesc, i);
            Form_pg_attribute sattr = TupleDescAttr(tupleDesc, i);

            if (!vattr->attisdropped)
                continue;       /* already checked non-dropped cols */
            if (slot->tts_isnull[i])
                continue;       /* null is always okay */
            if (vattr->attlen != sattr->attlen ||
                vattr->attalign != sattr->attalign)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("table row type and query-specified row type do not match"),
                         errdetail("Physical storage mismatch on dropped attribute at ordinal position %d.",
                                   i + 1)));
        }
    }

    /*
     * Build a composite datum, making sure any toasted fields get detoasted.
     *
     * (Note: it is critical that we not change the slot's state here.)
     */
    tuple = toast_build_flattened_tuple(slot->tts_tupleDescriptor,
                                        slot->tts_values,
                                        slot->tts_isnull);
    dtuple = tuple->t_data;

    /*
     * Label the datum with the composite type info we identified before.
     *
     * (Note: we could skip doing this by passing op->d.wholerow.tupdesc to
     * the tuple build step; but that seems a tad risky so let's not.)
     */
    HeapTupleHeaderSetTypeId(dtuple, op->d.wholerow.tupdesc->tdtypeid);
    HeapTupleHeaderSetTypMod(dtuple, op->d.wholerow.tupdesc->tdtypmod);

    *op->resvalue = PointerGetDatum(dtuple);
    *op->resnull = false;
}

void
ExecEvalSysVar(ExprState *state, ExprEvalStep *op, ExprContext *econtext,
               TupleTableSlot *slot)
{
    Datum       d;

    /* slot_getsysattr has sufficient defenses against bad attnums */
    d = slot_getsysattr(slot,
                        op->d.var.attnum,
                        op->resnull);
    *op->resvalue = d;
    /* this ought to be unreachable, but it's cheap enough to check */
    if (unlikely(*op->resnull))
        elog(ERROR, "failed to fetch attribute from slot");
}

/*
 * Transition value has not been initialized. This is the first non-NULL input
 * value for a group. We use it as the initial value for transValue.
 */
void
ExecAggInitGroup(AggState *aggstate, AggStatePerTrans pertrans, AggStatePerGroup pergroup,
                 ExprContext *aggcontext)
{
    FunctionCallInfo fcinfo = pertrans->transfn_fcinfo;
    MemoryContext oldContext;

    /*
     * We must copy the datum into aggcontext if it is pass-by-ref. We do not
     * need to pfree the old transValue, since it's NULL.  (We already checked
     * that the agg's input type is binary-compatible with its transtype, so
     * straight copy here is OK.)
     */
    oldContext = MemoryContextSwitchTo(aggcontext->ecxt_per_tuple_memory);
    pergroup->transValue = datumCopy(fcinfo->args[1].value,
                                     pertrans->transtypeByVal,
                                     pertrans->transtypeLen);
    pergroup->transValueIsNull = false;
    pergroup->noTransValue = false;
    MemoryContextSwitchTo(oldContext);
}

/*
 * Ensure that the current transition value is a child of the aggcontext,
 * rather than the per-tuple context.
 *
 * NB: This can change the current memory context.
 */
Datum
ExecAggTransReparent(AggState *aggstate, AggStatePerTrans pertrans,
                     Datum newValue, bool newValueIsNull,
                     Datum oldValue, bool oldValueIsNull)
{
    Assert(newValue != oldValue);

    if (!newValueIsNull)
    {
        MemoryContextSwitchTo(aggstate->curaggcontext->ecxt_per_tuple_memory);
        if (DatumIsReadWriteExpandedObject(newValue,
                                           false,
                                           pertrans->transtypeLen) &&
            MemoryContextGetParent(DatumGetEOHP(newValue)->eoh_context) == CurrentMemoryContext)
             /* do nothing */ ;
        else
            newValue = datumCopy(newValue,
                                 pertrans->transtypeByVal,
                                 pertrans->transtypeLen);
    }
    else
    {
        /*
         * Ensure that AggStatePerGroup->transValue ends up being 0, so
         * callers can safely compare newValue/oldValue without having to
         * check their respective nullness.
         */
        newValue = (Datum) 0;
    }

    if (!oldValueIsNull)
    {
        if (DatumIsReadWriteExpandedObject(oldValue,
                                           false,
                                           pertrans->transtypeLen))
            DeleteExpandedObject(oldValue);
        else
            pfree(DatumGetPointer(oldValue));
    }

    return newValue;
}

/*
 * Invoke ordered transition function, with a datum argument.
 */
void
ExecEvalAggOrderedTransDatum(ExprState *state, ExprEvalStep *op,
                             ExprContext *econtext)
{
    AggStatePerTrans pertrans = op->d.agg_trans.pertrans;
    int         setno = op->d.agg_trans.setno;

    tuplesort_putdatum(pertrans->sortstates[setno],
                       *op->resvalue, *op->resnull);
}

/*
 * Invoke ordered transition function, with a tuple argument.
 */
void
ExecEvalAggOrderedTransTuple(ExprState *state, ExprEvalStep *op,
                             ExprContext *econtext)
{
    AggStatePerTrans pertrans = op->d.agg_trans.pertrans;
    int         setno = op->d.agg_trans.setno;

    ExecClearTuple(pertrans->sortslot);
    pertrans->sortslot->tts_nvalid = pertrans->numInputs;
    ExecStoreVirtualTuple(pertrans->sortslot);
    tuplesort_puttupleslot(pertrans->sortstates[setno], pertrans->sortslot);
}

/* implementation of transition function invocation for byval types */
static pg_attribute_always_inline void
ExecAggPlainTransByVal(AggState *aggstate, AggStatePerTrans pertrans,
                       AggStatePerGroup pergroup,
                       ExprContext *aggcontext, int setno)
{
    FunctionCallInfo fcinfo = pertrans->transfn_fcinfo;
    MemoryContext oldContext;
    Datum       newVal;

    /* cf. select_current_set() */
    aggstate->curaggcontext = aggcontext;
    aggstate->current_set = setno;

    /* set up aggstate->curpertrans for AggGetAggref() */
    aggstate->curpertrans = pertrans;

    /* invoke transition function in per-tuple context */
    oldContext = MemoryContextSwitchTo(aggstate->tmpcontext->ecxt_per_tuple_memory);

    fcinfo->args[0].value = pergroup->transValue;
    fcinfo->args[0].isnull = pergroup->transValueIsNull;
    fcinfo->isnull = false;     /* just in case transfn doesn't set it */

    newVal = FunctionCallInvoke(fcinfo);

    pergroup->transValue = newVal;
    pergroup->transValueIsNull = fcinfo->isnull;

    MemoryContextSwitchTo(oldContext);
}

/* implementation of transition function invocation for byref types */
static pg_attribute_always_inline void
ExecAggPlainTransByRef(AggState *aggstate, AggStatePerTrans pertrans,
                       AggStatePerGroup pergroup,
                       ExprContext *aggcontext, int setno)
{
    FunctionCallInfo fcinfo = pertrans->transfn_fcinfo;
    MemoryContext oldContext;
    Datum       newVal;

    /* cf. select_current_set() */
    aggstate->curaggcontext = aggcontext;
    aggstate->current_set = setno;

    /* set up aggstate->curpertrans for AggGetAggref() */
    aggstate->curpertrans = pertrans;

    /* invoke transition function in per-tuple context */
    oldContext = MemoryContextSwitchTo(aggstate->tmpcontext->ecxt_per_tuple_memory);

    fcinfo->args[0].value = pergroup->transValue;
    fcinfo->args[0].isnull = pergroup->transValueIsNull;
    fcinfo->isnull = false;     /* just in case transfn doesn't set it */

    newVal = FunctionCallInvoke(fcinfo);

    /*
     * For pass-by-ref datatype, must copy the new value into aggcontext and
     * free the prior transValue.  But if transfn returned a pointer to its
     * first input, we don't need to do anything.  Also, if transfn returned a
     * pointer to a R/W expanded object that is already a child of the
     * aggcontext, assume we can adopt that value without copying it.
     *
     * It's safe to compare newVal with pergroup->transValue without regard
     * for either being NULL, because ExecAggTransReparent() takes care to set
     * transValue to 0 when NULL. Otherwise we could end up accidentally not
     * reparenting, when the transValue has the same numerical value as
     * newValue, despite being NULL.  This is a somewhat hot path, making it
     * undesirable to instead solve this with another branch for the common
     * case of the transition function returning its (modified) input
     * argument.
     */
    if (DatumGetPointer(newVal) != DatumGetPointer(pergroup->transValue))
        newVal = ExecAggTransReparent(aggstate, pertrans,
                                      newVal, fcinfo->isnull,
                                      pergroup->transValue,
                                      pergroup->transValueIsNull);

    pergroup->transValue = newVal;
    pergroup->transValueIsNull = fcinfo->isnull;

    MemoryContextSwitchTo(oldContext);
}