execExpr.c

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/*-------------------------------------------------------------------------
 *
 * execExpr.c
 *    Expression evaluation infrastructure.
 *
 *  During executor startup, we compile each expression tree (which has
 *  previously been processed by the parser and planner) into an ExprState,
 *  using ExecInitExpr() et al.  This converts the tree into a flat array
 *  of ExprEvalSteps, which may be thought of as instructions in a program.
 *  At runtime, we'll execute steps, starting with the first, until we reach
 *  an EEOP_DONE opcode.
 *
 *  This file contains the "compilation" logic.  It is independent of the
 *  specific execution technology we use (switch statement, computed goto,
 *  JIT compilation, etc).
 *
 *  See src/backend/executor/README for some background, specifically the
 *  "Expression Trees and ExprState nodes", "Expression Initialization",
 *  and "Expression Evaluation" sections.
 *
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/executor/execExpr.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/nbtree.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_type.h"
#include "executor/execExpr.h"
#include "executor/nodeSubplan.h"
#include "funcapi.h"
#include "jit/jit.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/subscripting.h"
#include "optimizer/optimizer.h"
#include "pgstat.h"
#include "utils/acl.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/typcache.h"


typedef struct LastAttnumInfo
{
    AttrNumber  last_inner;
    AttrNumber  last_outer;
    AttrNumber  last_scan;
} LastAttnumInfo;

static void ExecReadyExpr(ExprState *state);
static void ExecInitExprRec(Expr *node, ExprState *state,
                            Datum *resv, bool *resnull);
static void ExecInitFunc(ExprEvalStep *scratch, Expr *node, List *args,
                         Oid funcid, Oid inputcollid,
                         ExprState *state);
static void ExecInitExprSlots(ExprState *state, Node *node);
static void ExecPushExprSlots(ExprState *state, LastAttnumInfo *info);
static bool get_last_attnums_walker(Node *node, LastAttnumInfo *info);
static bool ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op);
static void ExecInitWholeRowVar(ExprEvalStep *scratch, Var *variable,
                                ExprState *state);
static void ExecInitSubscriptingRef(ExprEvalStep *scratch,
                                    SubscriptingRef *sbsref,
                                    ExprState *state,
                                    Datum *resv, bool *resnull);
static bool isAssignmentIndirectionExpr(Expr *expr);
static void ExecInitCoerceToDomain(ExprEvalStep *scratch, CoerceToDomain *ctest,
                                   ExprState *state,
                                   Datum *resv, bool *resnull);
static void ExecBuildAggTransCall(ExprState *state, AggState *aggstate,
                                  ExprEvalStep *scratch,
                                  FunctionCallInfo fcinfo, AggStatePerTrans pertrans,
                                  int transno, int setno, int setoff, bool ishash,
                                  bool nullcheck);


/*
 * ExecInitExpr: prepare an expression tree for execution
 *
 * This function builds and returns an ExprState implementing the given
 * Expr node tree.  The return ExprState can then be handed to ExecEvalExpr
 * for execution.  Because the Expr tree itself is read-only as far as
 * ExecInitExpr and ExecEvalExpr are concerned, several different executions
 * of the same plan tree can occur concurrently.  (But note that an ExprState
 * does mutate at runtime, so it can't be re-used concurrently.)
 *
 * This must be called in a memory context that will last as long as repeated
 * executions of the expression are needed.  Typically the context will be
 * the same as the per-query context of the associated ExprContext.
 *
 * Any Aggref, WindowFunc, or SubPlan nodes found in the tree are added to
 * the lists of such nodes held by the parent PlanState.
 *
 * Note: there is no ExecEndExpr function; we assume that any resource
 * cleanup needed will be handled by just releasing the memory context
 * in which the state tree is built.  Functions that require additional
 * cleanup work can register a shutdown callback in the ExprContext.
 *
 *  'node' is the root of the expression tree to compile.
 *  'parent' is the PlanState node that owns the expression.
 *
 * 'parent' may be NULL if we are preparing an expression that is not
 * associated with a plan tree.  (If so, it can't have aggs or subplans.)
 * Such cases should usually come through ExecPrepareExpr, not directly here.
 *
 * Also, if 'node' is NULL, we just return NULL.  This is convenient for some
 * callers that may or may not have an expression that needs to be compiled.
 * Note that a NULL ExprState pointer *cannot* be handed to ExecEvalExpr,
 * although ExecQual and ExecCheck will accept one (and treat it as "true").
 */
ExprState *
ExecInitExpr(Expr *node, PlanState *parent)
{
    ExprState  *state;
    ExprEvalStep scratch = {0};

    /* Special case: NULL expression produces a NULL ExprState pointer */
    if (node == NULL)
        return NULL;

    /* Initialize ExprState with empty step list */
    state = makeNode(ExprState);
    state->expr = node;
    state->parent = parent;
    state->ext_params = NULL;

    /* Insert EEOP_*_FETCHSOME steps as needed */
    ExecInitExprSlots(state, (Node *) node);

    /* Compile the expression proper */
    ExecInitExprRec(node, state, &state->resvalue, &state->resnull);

    /* Finally, append a DONE step */
    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return state;
}

/*
 * ExecInitExprWithParams: prepare a standalone expression tree for execution
 *
 * This is the same as ExecInitExpr, except that there is no parent PlanState,
 * and instead we may have a ParamListInfo describing PARAM_EXTERN Params.
 */
ExprState *
ExecInitExprWithParams(Expr *node, ParamListInfo ext_params)
{
    ExprState  *state;
    ExprEvalStep scratch = {0};

    /* Special case: NULL expression produces a NULL ExprState pointer */
    if (node == NULL)
        return NULL;

    /* Initialize ExprState with empty step list */
    state = makeNode(ExprState);
    state->expr = node;
    state->parent = NULL;
    state->ext_params = ext_params;

    /* Insert EEOP_*_FETCHSOME steps as needed */
    ExecInitExprSlots(state, (Node *) node);

    /* Compile the expression proper */
    ExecInitExprRec(node, state, &state->resvalue, &state->resnull);

    /* Finally, append a DONE step */
    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return state;
}

/*
 * ExecInitQual: prepare a qual for execution by ExecQual
 *
 * Prepares for the evaluation of a conjunctive boolean expression (qual list
 * with implicit AND semantics) that returns true if none of the
 * subexpressions are false.
 *
 * We must return true if the list is empty.  Since that's a very common case,
 * we optimize it a bit further by translating to a NULL ExprState pointer
 * rather than setting up an ExprState that computes constant TRUE.  (Some
 * especially hot-spot callers of ExecQual detect this and avoid calling
 * ExecQual at all.)
 *
 * If any of the subexpressions yield NULL, then the result of the conjunction
 * is false.  This makes ExecQual primarily useful for evaluating WHERE
 * clauses, since SQL specifies that tuples with null WHERE results do not
 * get selected.
 */
ExprState *
ExecInitQual(List *qual, PlanState *parent)
{
    ExprState  *state;
    ExprEvalStep scratch = {0};
    List       *adjust_jumps = NIL;
    ListCell   *lc;

    /* short-circuit (here and in ExecQual) for empty restriction list */
    if (qual == NIL)
        return NULL;

    Assert(IsA(qual, List));

    state = makeNode(ExprState);
    state->expr = (Expr *) qual;
    state->parent = parent;
    state->ext_params = NULL;

    /* mark expression as to be used with ExecQual() */
    state->flags = EEO_FLAG_IS_QUAL;

    /* Insert EEOP_*_FETCHSOME steps as needed */
    ExecInitExprSlots(state, (Node *) qual);

    /*
     * ExecQual() needs to return false for an expression returning NULL. That
     * allows us to short-circuit the evaluation the first time a NULL is
     * encountered.  As qual evaluation is a hot-path this warrants using a
     * special opcode for qual evaluation that's simpler than BOOL_AND (which
     * has more complex NULL handling).
     */
    scratch.opcode = EEOP_QUAL;

    /*
     * We can use ExprState's resvalue/resnull as target for each qual expr.
     */
    scratch.resvalue = &state->resvalue;
    scratch.resnull = &state->resnull;

    foreach(lc, qual)
    {
        Expr       *node = (Expr *) lfirst(lc);

        /* first evaluate expression */
        ExecInitExprRec(node, state, &state->resvalue, &state->resnull);

        /* then emit EEOP_QUAL to detect if it's false (or null) */
        scratch.d.qualexpr.jumpdone = -1;
        ExprEvalPushStep(state, &scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
    }

    /* adjust jump targets */
    foreach(lc, adjust_jumps)
    {
        ExprEvalStep *as = &state->steps[lfirst_int(lc)];

        Assert(as->opcode == EEOP_QUAL);
        Assert(as->d.qualexpr.jumpdone == -1);
        as->d.qualexpr.jumpdone = state->steps_len;
    }

    /*
     * At the end, we don't need to do anything more.  The last qual expr must
     * have yielded TRUE, and since its result is stored in the desired output
     * location, we're done.
     */
    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return state;
}

/*
 * ExecInitCheck: prepare a check constraint for execution by ExecCheck
 *
 * This is much like ExecInitQual/ExecQual, except that a null result from
 * the conjunction is treated as TRUE.  This behavior is appropriate for
 * evaluating CHECK constraints, since SQL specifies that NULL constraint
 * conditions are not failures.
 *
 * Note that like ExecInitQual, this expects input in implicit-AND format.
 * Users of ExecCheck that have expressions in normal explicit-AND format
 * can just apply ExecInitExpr to produce suitable input for ExecCheck.
 */
ExprState *
ExecInitCheck(List *qual, PlanState *parent)
{
    /* short-circuit (here and in ExecCheck) for empty restriction list */
    if (qual == NIL)
        return NULL;

    Assert(IsA(qual, List));

    /*
     * Just convert the implicit-AND list to an explicit AND (if there's more
     * than one entry), and compile normally.  Unlike ExecQual, we can't
     * short-circuit on NULL results, so the regular AND behavior is needed.
     */
    return ExecInitExpr(make_ands_explicit(qual), parent);
}

/*
 * Call ExecInitExpr() on a list of expressions, return a list of ExprStates.
 */
List *
ExecInitExprList(List *nodes, PlanState *parent)
{
    List       *result = NIL;
    ListCell   *lc;

    foreach(lc, nodes)
    {
        Expr       *e = lfirst(lc);

        result = lappend(result, ExecInitExpr(e, parent));
    }

    return result;
}

/*
 *      ExecBuildProjectionInfo
 *
 * Build a ProjectionInfo node for evaluating the given tlist in the given
 * econtext, and storing the result into the tuple slot.  (Caller must have
 * ensured that tuple slot has a descriptor matching the tlist!)
 *
 * inputDesc can be NULL, but if it is not, we check to see whether simple
 * Vars in the tlist match the descriptor.  It is important to provide
 * inputDesc for relation-scan plan nodes, as a cross check that the relation
 * hasn't been changed since the plan was made.  At higher levels of a plan,
 * there is no need to recheck.
 *
 * This is implemented by internally building an ExprState that performs the
 * whole projection in one go.
 *
 * Caution: before PG v10, the targetList was a list of ExprStates; now it
 * should be the planner-created targetlist, since we do the compilation here.
 */
ProjectionInfo *
ExecBuildProjectionInfo(List *targetList,
                        ExprContext *econtext,
                        TupleTableSlot *slot,
                        PlanState *parent,
                        TupleDesc inputDesc)
{
    ProjectionInfo *projInfo = makeNode(ProjectionInfo);
    ExprState  *state;
    ExprEvalStep scratch = {0};
    ListCell   *lc;

    projInfo->pi_exprContext = econtext;
    /* We embed ExprState into ProjectionInfo instead of doing extra palloc */
    projInfo->pi_state.type = T_ExprState;
    state = &projInfo->pi_state;
    state->expr = (Expr *) targetList;
    state->parent = parent;
    state->ext_params = NULL;

    state->resultslot = slot;

    /* Insert EEOP_*_FETCHSOME steps as needed */
    ExecInitExprSlots(state, (Node *) targetList);

    /* Now compile each tlist column */
    foreach(lc, targetList)
    {
        TargetEntry *tle = lfirst_node(TargetEntry, lc);
        Var        *variable = NULL;
        AttrNumber  attnum = 0;
        bool        isSafeVar = false;

        /*
         * If tlist expression is a safe non-system Var, use the fast-path
         * ASSIGN_*_VAR opcodes.  "Safe" means that we don't need to apply
         * CheckVarSlotCompatibility() during plan startup.  If a source slot
         * was provided, we make the equivalent tests here; if a slot was not
         * provided, we assume that no check is needed because we're dealing
         * with a non-relation-scan-level expression.
         */
        if (tle->expr != NULL &&
            IsA(tle->expr, Var) &&
            ((Var *) tle->expr)->varattno > 0)
        {
            /* Non-system Var, but how safe is it? */
            variable = (Var *) tle->expr;
            attnum = variable->varattno;

            if (inputDesc == NULL)
                isSafeVar = true;   /* can't check, just assume OK */
            else if (attnum <= inputDesc->natts)
            {
                Form_pg_attribute attr = TupleDescAttr(inputDesc, attnum - 1);

                /*
                 * If user attribute is dropped or has a type mismatch, don't
                 * use ASSIGN_*_VAR.  Instead let the normal expression
                 * machinery handle it (which'll possibly error out).
                 */
                if (!attr->attisdropped && variable->vartype == attr->atttypid)
                {
                    isSafeVar = true;
                }
            }
        }

        if (isSafeVar)
        {
            /* Fast-path: just generate an EEOP_ASSIGN_*_VAR step */
            switch (variable->varno)
            {
                case INNER_VAR:
                    /* get the tuple from the inner node */
                    scratch.opcode = EEOP_ASSIGN_INNER_VAR;
                    break;

                case OUTER_VAR:
                    /* get the tuple from the outer node */
                    scratch.opcode = EEOP_ASSIGN_OUTER_VAR;
                    break;

                    /* INDEX_VAR is handled by default case */

                default:
                    /* get the tuple from the relation being scanned */
                    scratch.opcode = EEOP_ASSIGN_SCAN_VAR;
                    break;
            }

            scratch.d.assign_var.attnum = attnum - 1;
            scratch.d.assign_var.resultnum = tle->resno - 1;
            ExprEvalPushStep(state, &scratch);
        }
        else
        {
            /*
             * Otherwise, compile the column expression normally.
             *
             * We can't tell the expression to evaluate directly into the
             * result slot, as the result slot (and the exprstate for that
             * matter) can change between executions.  We instead evaluate
             * into the ExprState's resvalue/resnull and then move.
             */
            ExecInitExprRec(tle->expr, state,
                            &state->resvalue, &state->resnull);

            /*
             * Column might be referenced multiple times in upper nodes, so
             * force value to R/O - but only if it could be an expanded datum.
             */
            if (get_typlen(exprType((Node *) tle->expr)) == -1)
                scratch.opcode = EEOP_ASSIGN_TMP_MAKE_RO;
            else
                scratch.opcode = EEOP_ASSIGN_TMP;
            scratch.d.assign_tmp.resultnum = tle->resno - 1;
            ExprEvalPushStep(state, &scratch);
        }
    }

    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return projInfo;
}

/*
 *      ExecBuildUpdateProjection
 *
 * Build a ProjectionInfo node for constructing a new tuple during UPDATE.
 * The projection will be executed in the given econtext and the result will
 * be stored into the given tuple slot.  (Caller must have ensured that tuple
 * slot has a descriptor matching the target rel!)
 *
 * When evalTargetList is false, targetList contains the UPDATE ... SET
 * expressions that have already been computed by a subplan node; the values
 * from this tlist are assumed to be available in the "outer" tuple slot.
 * When evalTargetList is true, targetList contains the UPDATE ... SET
 * expressions that must be computed (which could contain references to
 * the outer, inner, or scan tuple slots).
 *
 * In either case, targetColnos contains a list of the target column numbers
 * corresponding to the non-resjunk entries of targetList.  The tlist values
 * are assigned into these columns of the result tuple slot.  Target columns
 * not listed in targetColnos are filled from the UPDATE's old tuple, which
 * is assumed to be available in the "scan" tuple slot.
 *
 * targetList can also contain resjunk columns.  These must be evaluated
 * if evalTargetList is true, but their values are discarded.
 *
 * relDesc must describe the relation we intend to update.
 *
 * This is basically a specialized variant of ExecBuildProjectionInfo.
 * However, it also performs sanity checks equivalent to ExecCheckPlanOutput.
 * Since we never make a normal tlist equivalent to the whole
 * tuple-to-be-assigned, there is no convenient way to apply
 * ExecCheckPlanOutput, so we must do our safety checks here.
 */
ProjectionInfo *
ExecBuildUpdateProjection(List *targetList,
                          bool evalTargetList,
                          List *targetColnos,
                          TupleDesc relDesc,
                          ExprContext *econtext,
                          TupleTableSlot *slot,
                          PlanState *parent)
{
    ProjectionInfo *projInfo = makeNode(ProjectionInfo);
    ExprState  *state;
    int         nAssignableCols;
    bool        sawJunk;
    Bitmapset  *assignedCols;
    LastAttnumInfo deform = {0, 0, 0};
    ExprEvalStep scratch = {0};
    int         outerattnum;
    ListCell   *lc,
               *lc2;

    projInfo->pi_exprContext = econtext;
    /* We embed ExprState into ProjectionInfo instead of doing extra palloc */
    projInfo->pi_state.type = T_ExprState;
    state = &projInfo->pi_state;
    if (evalTargetList)
        state->expr = (Expr *) targetList;
    else
        state->expr = NULL;     /* not used */
    state->parent = parent;
    state->ext_params = NULL;

    state->resultslot = slot;

    /*
     * Examine the targetList to see how many non-junk columns there are, and
     * to verify that the non-junk columns come before the junk ones.
     */
    nAssignableCols = 0;
    sawJunk = false;
    foreach(lc, targetList)
    {
        TargetEntry *tle = lfirst_node(TargetEntry, lc);

        if (tle->resjunk)
            sawJunk = true;
        else
        {
            if (sawJunk)
                elog(ERROR, "subplan target list is out of order");
            nAssignableCols++;
        }
    }

    /* We should have one targetColnos entry per non-junk column */
    if (nAssignableCols != list_length(targetColnos))
        elog(ERROR, "targetColnos does not match subplan target list");

    /*
     * Build a bitmapset of the columns in targetColnos.  (We could just use
     * list_member_int() tests, but that risks O(N^2) behavior with many
     * columns.)
     */
    assignedCols = NULL;
    foreach(lc, targetColnos)
    {
        AttrNumber  targetattnum = lfirst_int(lc);

        assignedCols = bms_add_member(assignedCols, targetattnum);
    }

    /*
     * We need to insert EEOP_*_FETCHSOME steps to ensure the input tuples are
     * sufficiently deconstructed.  The scan tuple must be deconstructed at
     * least as far as the last old column we need.
     */
    for (int attnum = relDesc->natts; attnum > 0; attnum--)
    {
        Form_pg_attribute attr = TupleDescAttr(relDesc, attnum - 1);

        if (attr->attisdropped)
            continue;
        if (bms_is_member(attnum, assignedCols))
            continue;
        deform.last_scan = attnum;
        break;
    }

    /*
     * If we're actually evaluating the tlist, incorporate its input
     * requirements too; otherwise, we'll just need to fetch the appropriate
     * number of columns of the "outer" tuple.
     */
    if (evalTargetList)
        get_last_attnums_walker((Node *) targetList, &deform);
    else
        deform.last_outer = nAssignableCols;

    ExecPushExprSlots(state, &deform);

    /*
     * Now generate code to evaluate the tlist's assignable expressions or
     * fetch them from the outer tuple, incidentally validating that they'll
     * be of the right data type.  The checks above ensure that the forboth()
     * will iterate over exactly the non-junk columns.
     */
    outerattnum = 0;
    forboth(lc, targetList, lc2, targetColnos)
    {
        TargetEntry *tle = lfirst_node(TargetEntry, lc);
        AttrNumber  targetattnum = lfirst_int(lc2);
        Form_pg_attribute attr;

        Assert(!tle->resjunk);

        /*
         * Apply sanity checks comparable to ExecCheckPlanOutput().
         */
        if (targetattnum <= 0 || targetattnum > relDesc->natts)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("table row type and query-specified row type do not match"),
                     errdetail("Query has too many columns.")));
        attr = TupleDescAttr(relDesc, targetattnum - 1);

        if (attr->attisdropped)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("table row type and query-specified row type do not match"),
                     errdetail("Query provides a value for a dropped column at ordinal position %d.",
                               targetattnum)));
        if (exprType((Node *) tle->expr) != attr->atttypid)
            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(attr->atttypid),
                               targetattnum,
                               format_type_be(exprType((Node *) tle->expr)))));

        /* OK, generate code to perform the assignment. */
        if (evalTargetList)
        {
            /*
             * We must evaluate the TLE's expression and assign it.  We do not
             * bother jumping through hoops for "safe" Vars like
             * ExecBuildProjectionInfo does; this is a relatively less-used
             * path and it doesn't seem worth expending code for that.
             */
            ExecInitExprRec(tle->expr, state,
                            &state->resvalue, &state->resnull);
            /* Needn't worry about read-only-ness here, either. */
            scratch.opcode = EEOP_ASSIGN_TMP;
            scratch.d.assign_tmp.resultnum = targetattnum - 1;
            ExprEvalPushStep(state, &scratch);
        }
        else
        {
            /* Just assign from the outer tuple. */
            scratch.opcode = EEOP_ASSIGN_OUTER_VAR;
            scratch.d.assign_var.attnum = outerattnum;
            scratch.d.assign_var.resultnum = targetattnum - 1;
            ExprEvalPushStep(state, &scratch);
        }
        outerattnum++;
    }

    /*
     * If we're evaluating the tlist, must evaluate any resjunk columns too.
     * (This matters for things like MULTIEXPR_SUBLINK SubPlans.)
     */
    if (evalTargetList)
    {
        for_each_cell(lc, targetList, lc)
        {
            TargetEntry *tle = lfirst_node(TargetEntry, lc);

            Assert(tle->resjunk);
            ExecInitExprRec(tle->expr, state,
                            &state->resvalue, &state->resnull);
        }
    }

    /*
     * Now generate code to copy over any old columns that were not assigned
     * to, and to ensure that dropped columns are set to NULL.
     */
    for (int attnum = 1; attnum <= relDesc->natts; attnum++)
    {
        Form_pg_attribute attr = TupleDescAttr(relDesc, attnum - 1);

        if (attr->attisdropped)
        {
            /* Put a null into the ExprState's resvalue/resnull ... */
            scratch.opcode = EEOP_CONST;
            scratch.resvalue = &state->resvalue;
            scratch.resnull = &state->resnull;
            scratch.d.constval.value = (Datum) 0;
            scratch.d.constval.isnull = true;
            ExprEvalPushStep(state, &scratch);
            /* ... then assign it to the result slot */
            scratch.opcode = EEOP_ASSIGN_TMP;
            scratch.d.assign_tmp.resultnum = attnum - 1;
            ExprEvalPushStep(state, &scratch);
        }
        else if (!bms_is_member(attnum, assignedCols))
        {
            /* Certainly the right type, so needn't check */
            scratch.opcode = EEOP_ASSIGN_SCAN_VAR;
            scratch.d.assign_var.attnum = attnum - 1;
            scratch.d.assign_var.resultnum = attnum - 1;
            ExprEvalPushStep(state, &scratch);
        }
    }

    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return projInfo;
}

/*
 * ExecPrepareExpr --- initialize for expression execution outside a normal
 * Plan tree context.
 *
 * This differs from ExecInitExpr in that we don't assume the caller is
 * already running in the EState's per-query context.  Also, we run the
 * passed expression tree through expression_planner() to prepare it for
 * execution.  (In ordinary Plan trees the regular planning process will have
 * made the appropriate transformations on expressions, but for standalone
 * expressions this won't have happened.)
 */
ExprState *
ExecPrepareExpr(Expr *node, EState *estate)
{
    ExprState  *result;
    MemoryContext oldcontext;

    oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

    node = expression_planner(node);

    result = ExecInitExpr(node, NULL);

    MemoryContextSwitchTo(oldcontext);

    return result;
}

/*
 * ExecPrepareQual --- initialize for qual execution outside a normal
 * Plan tree context.
 *
 * This differs from ExecInitQual in that we don't assume the caller is
 * already running in the EState's per-query context.  Also, we run the
 * passed expression tree through expression_planner() to prepare it for
 * execution.  (In ordinary Plan trees the regular planning process will have
 * made the appropriate transformations on expressions, but for standalone
 * expressions this won't have happened.)
 */
ExprState *
ExecPrepareQual(List *qual, EState *estate)
{
    ExprState  *result;
    MemoryContext oldcontext;

    oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

    qual = (List *) expression_planner((Expr *) qual);

    result = ExecInitQual(qual, NULL);

    MemoryContextSwitchTo(oldcontext);

    return result;
}

/*
 * ExecPrepareCheck -- initialize check constraint for execution outside a
 * normal Plan tree context.
 *
 * See ExecPrepareExpr() and ExecInitCheck() for details.
 */
ExprState *
ExecPrepareCheck(List *qual, EState *estate)
{
    ExprState  *result;
    MemoryContext oldcontext;

    oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

    qual = (List *) expression_planner((Expr *) qual);

    result = ExecInitCheck(qual, NULL);

    MemoryContextSwitchTo(oldcontext);

    return result;
}

/*
 * Call ExecPrepareExpr() on each member of a list of Exprs, and return
 * a list of ExprStates.
 *
 * See ExecPrepareExpr() for details.
 */
List *
ExecPrepareExprList(List *nodes, EState *estate)
{
    List       *result = NIL;
    MemoryContext oldcontext;
    ListCell   *lc;

    /* Ensure that the list cell nodes are in the right context too */
    oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

    foreach(lc, nodes)
    {
        Expr       *e = (Expr *) lfirst(lc);

        result = lappend(result, ExecPrepareExpr(e, estate));
    }

    MemoryContextSwitchTo(oldcontext);

    return result;
}

/*
 * ExecCheck - evaluate a check constraint
 *
 * For check constraints, a null result is taken as TRUE, ie the constraint
 * passes.
 *
 * The check constraint may have been prepared with ExecInitCheck
 * (possibly via ExecPrepareCheck) if the caller had it in implicit-AND
 * format, but a regular boolean expression prepared with ExecInitExpr or
 * ExecPrepareExpr works too.
 */
bool
ExecCheck(ExprState *state, ExprContext *econtext)
{
    Datum       ret;
    bool        isnull;

    /* short-circuit (here and in ExecInitCheck) for empty restriction list */
    if (state == NULL)
        return true;

    /* verify that expression was not compiled using ExecInitQual */
    Assert(!(state->flags & EEO_FLAG_IS_QUAL));

    ret = ExecEvalExprSwitchContext(state, econtext, &isnull);

    if (isnull)
        return true;

    return DatumGetBool(ret);
}

/*
 * Prepare a compiled expression for execution.  This has to be called for
 * every ExprState before it can be executed.
 *
 * NB: While this currently only calls ExecReadyInterpretedExpr(),
 * this will likely get extended to further expression evaluation methods.
 * Therefore this should be used instead of directly calling
 * ExecReadyInterpretedExpr().
 */
static void
ExecReadyExpr(ExprState *state)
{
    if (jit_compile_expr(state))
        return;

    ExecReadyInterpretedExpr(state);
}

/*
 * Append the steps necessary for the evaluation of node to ExprState->steps,
 * possibly recursing into sub-expressions of node.
 *
 * node - expression to evaluate
 * state - ExprState to whose ->steps to append the necessary operations
 * resv / resnull - where to store the result of the node into
 */
static void
ExecInitExprRec(Expr *node, ExprState *state,
                Datum *resv, bool *resnull)
{
    ExprEvalStep scratch = {0};

    /* Guard against stack overflow due to overly complex expressions */
    check_stack_depth();

    /* Step's output location is always what the caller gave us */
    Assert(resv != NULL && resnull != NULL);
    scratch.resvalue = resv;
    scratch.resnull = resnull;

    /* cases should be ordered as they are in enum NodeTag */
    switch (nodeTag(node))
    {
        case T_Var:
            {
                Var        *variable = (Var *) node;

                if (variable->varattno == InvalidAttrNumber)
                {
                    /* whole-row Var */
                    ExecInitWholeRowVar(&scratch, variable, state);
                }
                else if (variable->varattno <= 0)
                {
                    /* system column */
                    scratch.d.var.attnum = variable->varattno;
                    scratch.d.var.vartype = variable->vartype;
                    switch (variable->varno)
                    {
                        case INNER_VAR:
                            scratch.opcode = EEOP_INNER_SYSVAR;
                            break;
                        case OUTER_VAR:
                            scratch.opcode = EEOP_OUTER_SYSVAR;
                            break;

                            /* INDEX_VAR is handled by default case */

                        default:
                            scratch.opcode = EEOP_SCAN_SYSVAR;
                            break;
                    }
                }
                else
                {
                    /* regular user column */
                    scratch.d.var.attnum = variable->varattno - 1;
                    scratch.d.var.vartype = variable->vartype;
                    switch (variable->varno)
                    {
                        case INNER_VAR:
                            scratch.opcode = EEOP_INNER_VAR;
                            break;
                        case OUTER_VAR:
                            scratch.opcode = EEOP_OUTER_VAR;
                            break;

                            /* INDEX_VAR is handled by default case */

                        default:
                            scratch.opcode = EEOP_SCAN_VAR;
                            break;
                    }
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_Const:
            {
                Const      *con = (Const *) node;

                scratch.opcode = EEOP_CONST;
                scratch.d.constval.value = con->constvalue;
                scratch.d.constval.isnull = con->constisnull;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_Param:
            {
                Param      *param = (Param *) node;
                ParamListInfo params;

                switch (param->paramkind)
                {
                    case PARAM_EXEC:
                        scratch.opcode = EEOP_PARAM_EXEC;
                        scratch.d.param.paramid = param->paramid;
                        scratch.d.param.paramtype = param->paramtype;
                        ExprEvalPushStep(state, &scratch);
                        break;
                    case PARAM_EXTERN:

                        /*
                         * If we have a relevant ParamCompileHook, use it;
                         * otherwise compile a standard EEOP_PARAM_EXTERN
                         * step.  ext_params, if supplied, takes precedence
                         * over info from the parent node's EState (if any).
                         */
                        if (state->ext_params)
                            params = state->ext_params;
                        else if (state->parent &&
                                 state->parent->state)
                            params = state->parent->state->es_param_list_info;
                        else
                            params = NULL;
                        if (params && params->paramCompile)
                        {
                            params->paramCompile(params, param, state,
                                                 resv, resnull);
                        }
                        else
                        {
                            scratch.opcode = EEOP_PARAM_EXTERN;
                            scratch.d.param.paramid = param->paramid;
                            scratch.d.param.paramtype = param->paramtype;
                            ExprEvalPushStep(state, &scratch);
                        }
                        break;
                    default:
                        elog(ERROR, "unrecognized paramkind: %d",
                             (int) param->paramkind);
                        break;
                }
                break;
            }

        case T_Aggref:
            {
                Aggref     *aggref = (Aggref *) node;

                scratch.opcode = EEOP_AGGREF;
                scratch.d.aggref.aggno = aggref->aggno;

                if (state->parent && IsA(state->parent, AggState))
                {
                    AggState   *aggstate = (AggState *) state->parent;

                    aggstate->aggs = lappend(aggstate->aggs, aggref);
                }
                else
                {
                    /* planner messed up */
                    elog(ERROR, "Aggref found in non-Agg plan node");
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_GroupingFunc:
            {
                GroupingFunc *grp_node = (GroupingFunc *) node;
                Agg        *agg;

                if (!state->parent || !IsA(state->parent, AggState) ||
                    !IsA(state->parent->plan, Agg))
                    elog(ERROR, "GroupingFunc found in non-Agg plan node");

                scratch.opcode = EEOP_GROUPING_FUNC;

                agg = (Agg *) (state->parent->plan);

                if (agg->groupingSets)
                    scratch.d.grouping_func.clauses = grp_node->cols;
                else
                    scratch.d.grouping_func.clauses = NIL;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_WindowFunc:
            {
                WindowFunc *wfunc = (WindowFunc *) node;
                WindowFuncExprState *wfstate = makeNode(WindowFuncExprState);

                wfstate->wfunc = wfunc;

                if (state->parent && IsA(state->parent, WindowAggState))
                {
                    WindowAggState *winstate = (WindowAggState *) state->parent;
                    int         nfuncs;

                    winstate->funcs = lappend(winstate->funcs, wfstate);
                    nfuncs = ++winstate->numfuncs;
                    if (wfunc->winagg)
                        winstate->numaggs++;

                    /* for now initialize agg using old style expressions */
                    wfstate->args = ExecInitExprList(wfunc->args,
                                                     state->parent);
                    wfstate->aggfilter = ExecInitExpr(wfunc->aggfilter,
                                                      state->parent);

                    /*
                     * Complain if the windowfunc's arguments contain any
                     * windowfuncs; nested window functions are semantically
                     * nonsensical.  (This should have been caught earlier,
                     * but we defend against it here anyway.)
                     */
                    if (nfuncs != winstate->numfuncs)
                        ereport(ERROR,
                                (errcode(ERRCODE_WINDOWING_ERROR),
                                 errmsg("window function calls cannot be nested")));
                }
                else
                {
                    /* planner messed up */
                    elog(ERROR, "WindowFunc found in non-WindowAgg plan node");
                }

                scratch.opcode = EEOP_WINDOW_FUNC;
                scratch.d.window_func.wfstate = wfstate;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_SubscriptingRef:
            {
                SubscriptingRef *sbsref = (SubscriptingRef *) node;

                ExecInitSubscriptingRef(&scratch, sbsref, state, resv, resnull);
                break;
            }

        case T_FuncExpr:
            {
                FuncExpr   *func = (FuncExpr *) node;

                ExecInitFunc(&scratch, node,
                             func->args, func->funcid, func->inputcollid,
                             state);
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_OpExpr:
            {
                OpExpr     *op = (OpExpr *) node;

                ExecInitFunc(&scratch, node,
                             op->args, op->opfuncid, op->inputcollid,
                             state);
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_DistinctExpr:
            {
                DistinctExpr *op = (DistinctExpr *) node;

                ExecInitFunc(&scratch, node,
                             op->args, op->opfuncid, op->inputcollid,
                             state);

                /*
                 * Change opcode of call instruction to EEOP_DISTINCT.
                 *
                 * XXX: historically we've not called the function usage
                 * pgstat infrastructure - that seems inconsistent given that
                 * we do so for normal function *and* operator evaluation.  If
                 * we decided to do that here, we'd probably want separate
                 * opcodes for FUSAGE or not.
                 */
                scratch.opcode = EEOP_DISTINCT;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_NullIfExpr:
            {
                NullIfExpr *op = (NullIfExpr *) node;

                ExecInitFunc(&scratch, node,
                             op->args, op->opfuncid, op->inputcollid,
                             state);

                /*
                 * Change opcode of call instruction to EEOP_NULLIF.
                 *
                 * XXX: historically we've not called the function usage
                 * pgstat infrastructure - that seems inconsistent given that
                 * we do so for normal function *and* operator evaluation.  If
                 * we decided to do that here, we'd probably want separate
                 * opcodes for FUSAGE or not.
                 */
                scratch.opcode = EEOP_NULLIF;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ScalarArrayOpExpr:
            {
                ScalarArrayOpExpr *opexpr = (ScalarArrayOpExpr *) node;
                Expr       *scalararg;
                Expr       *arrayarg;
                FmgrInfo   *finfo;
                FunctionCallInfo fcinfo;
                AclResult   aclresult;
                FmgrInfo   *hash_finfo;
                FunctionCallInfo hash_fcinfo;
                Oid         cmpfuncid;

                /*
                 * Select the correct comparison function.  When we do hashed
                 * NOT IN clauses, the opfuncid will be the inequality
                 * comparison function and negfuncid will be set to equality.
                 * We need to use the equality function for hash probes.
                 */
                if (OidIsValid(opexpr->negfuncid))
                {
                    Assert(OidIsValid(opexpr->hashfuncid));
                    cmpfuncid = opexpr->negfuncid;
                }
                else
                    cmpfuncid = opexpr->opfuncid;

                Assert(list_length(opexpr->args) == 2);
                scalararg = (Expr *) linitial(opexpr->args);
                arrayarg = (Expr *) lsecond(opexpr->args);

                /* Check permission to call function */
                aclresult = pg_proc_aclcheck(cmpfuncid,
                                             GetUserId(),
                                             ACL_EXECUTE);
                if (aclresult != ACLCHECK_OK)
                    aclcheck_error(aclresult, OBJECT_FUNCTION,
                                   get_func_name(cmpfuncid));
                InvokeFunctionExecuteHook(cmpfuncid);

                if (OidIsValid(opexpr->hashfuncid))
                {
                    aclresult = pg_proc_aclcheck(opexpr->hashfuncid,
                                                 GetUserId(),
                                                 ACL_EXECUTE);
                    if (aclresult != ACLCHECK_OK)
                        aclcheck_error(aclresult, OBJECT_FUNCTION,
                                       get_func_name(opexpr->hashfuncid));
                    InvokeFunctionExecuteHook(opexpr->hashfuncid);
                }

                /* Set up the primary fmgr lookup information */
                finfo = palloc0(sizeof(FmgrInfo));
                fcinfo = palloc0(SizeForFunctionCallInfo(2));
                fmgr_info(cmpfuncid, finfo);
                fmgr_info_set_expr((Node *) node, finfo);
                InitFunctionCallInfoData(*fcinfo, finfo, 2,
                                         opexpr->inputcollid, NULL, NULL);

                /*
                 * If hashfuncid is set, we create a EEOP_HASHED_SCALARARRAYOP
                 * step instead of a EEOP_SCALARARRAYOP.  This provides much
                 * faster lookup performance than the normal linear search
                 * when the number of items in the array is anything but very
                 * small.
                 */
                if (OidIsValid(opexpr->hashfuncid))
                {
                    hash_finfo = palloc0(sizeof(FmgrInfo));
                    hash_fcinfo = palloc0(SizeForFunctionCallInfo(1));
                    fmgr_info(opexpr->hashfuncid, hash_finfo);
                    fmgr_info_set_expr((Node *) node, hash_finfo);
                    InitFunctionCallInfoData(*hash_fcinfo, hash_finfo,
                                             1, opexpr->inputcollid, NULL,
                                             NULL);

                    scratch.d.hashedscalararrayop.hash_finfo = hash_finfo;
                    scratch.d.hashedscalararrayop.hash_fcinfo_data = hash_fcinfo;
                    scratch.d.hashedscalararrayop.hash_fn_addr = hash_finfo->fn_addr;

                    /* Evaluate scalar directly into left function argument */
                    ExecInitExprRec(scalararg, state,
                                    &fcinfo->args[0].value, &fcinfo->args[0].isnull);

                    /*
                     * Evaluate array argument into our return value.  There's
                     * no danger in that, because the return value is
                     * guaranteed to be overwritten by
                     * EEOP_HASHED_SCALARARRAYOP, and will not be passed to
                     * any other expression.
                     */
                    ExecInitExprRec(arrayarg, state, resv, resnull);

                    /* And perform the operation */
                    scratch.opcode = EEOP_HASHED_SCALARARRAYOP;
                    scratch.d.hashedscalararrayop.inclause = opexpr->useOr;
                    scratch.d.hashedscalararrayop.finfo = finfo;
                    scratch.d.hashedscalararrayop.fcinfo_data = fcinfo;
                    scratch.d.hashedscalararrayop.fn_addr = finfo->fn_addr;

                    scratch.d.hashedscalararrayop.hash_finfo = hash_finfo;
                    scratch.d.hashedscalararrayop.hash_fcinfo_data = hash_fcinfo;
                    scratch.d.hashedscalararrayop.hash_fn_addr = hash_finfo->fn_addr;

                    ExprEvalPushStep(state, &scratch);
                }
                else
                {
                    /* Evaluate scalar directly into left function argument */
                    ExecInitExprRec(scalararg, state,
                                    &fcinfo->args[0].value,
                                    &fcinfo->args[0].isnull);

                    /*
                     * Evaluate array argument into our return value.  There's
                     * no danger in that, because the return value is
                     * guaranteed to be overwritten by EEOP_SCALARARRAYOP, and
                     * will not be passed to any other expression.
                     */
                    ExecInitExprRec(arrayarg, state, resv, resnull);

                    /* And perform the operation */
                    scratch.opcode = EEOP_SCALARARRAYOP;
                    scratch.d.scalararrayop.element_type = InvalidOid;
                    scratch.d.scalararrayop.useOr = opexpr->useOr;
                    scratch.d.scalararrayop.finfo = finfo;
                    scratch.d.scalararrayop.fcinfo_data = fcinfo;
                    scratch.d.scalararrayop.fn_addr = finfo->fn_addr;
                    ExprEvalPushStep(state, &scratch);
                }
                break;
            }

        case T_BoolExpr:
            {
                BoolExpr   *boolexpr = (BoolExpr *) node;
                int         nargs = list_length(boolexpr->args);
                List       *adjust_jumps = NIL;
                int         off;
                ListCell   *lc;

                /* allocate scratch memory used by all steps of AND/OR */
                if (boolexpr->boolop != NOT_EXPR)
                    scratch.d.boolexpr.anynull = (bool *) palloc(sizeof(bool));

                /*
                 * For each argument evaluate the argument itself, then
                 * perform the bool operation's appropriate handling.
                 *
                 * We can evaluate each argument into our result area, since
                 * the short-circuiting logic means we only need to remember
                 * previous NULL values.
                 *
                 * AND/OR is split into separate STEP_FIRST (one) / STEP (zero
                 * or more) / STEP_LAST (one) steps, as each of those has to
                 * perform different work.  The FIRST/LAST split is valid
                 * because AND/OR have at least two arguments.
                 */
                off = 0;
                foreach(lc, boolexpr->args)
                {
                    Expr       *arg = (Expr *) lfirst(lc);

                    /* Evaluate argument into our output variable */
                    ExecInitExprRec(arg, state, resv, resnull);

                    /* Perform the appropriate step type */
                    switch (boolexpr->boolop)
                    {
                        case AND_EXPR:
                            Assert(nargs >= 2);

                            if (off == 0)
                                scratch.opcode = EEOP_BOOL_AND_STEP_FIRST;
                            else if (off + 1 == nargs)
                                scratch.opcode = EEOP_BOOL_AND_STEP_LAST;
                            else
                                scratch.opcode = EEOP_BOOL_AND_STEP;
                            break;
                        case OR_EXPR:
                            Assert(nargs >= 2);

                            if (off == 0)
                                scratch.opcode = EEOP_BOOL_OR_STEP_FIRST;
                            else if (off + 1 == nargs)
                                scratch.opcode = EEOP_BOOL_OR_STEP_LAST;
                            else
                                scratch.opcode = EEOP_BOOL_OR_STEP;
                            break;
                        case NOT_EXPR:
                            Assert(nargs == 1);

                            scratch.opcode = EEOP_BOOL_NOT_STEP;
                            break;
                        default:
                            elog(ERROR, "unrecognized boolop: %d",
                                 (int) boolexpr->boolop);
                            break;
                    }

                    scratch.d.boolexpr.jumpdone = -1;
                    ExprEvalPushStep(state, &scratch);
                    adjust_jumps = lappend_int(adjust_jumps,
                                               state->steps_len - 1);
                    off++;
                }

                /* adjust jump targets */
                foreach(lc, adjust_jumps)
                {
                    ExprEvalStep *as = &state->steps[lfirst_int(lc)];

                    Assert(as->d.boolexpr.jumpdone == -1);
                    as->d.boolexpr.jumpdone = state->steps_len;
                }

                break;
            }

        case T_SubPlan:
            {
                SubPlan    *subplan = (SubPlan *) node;
                SubPlanState *sstate;

                if (!state->parent)
                    elog(ERROR, "SubPlan found with no parent plan");

                sstate = ExecInitSubPlan(subplan, state->parent);

                /* add SubPlanState nodes to state->parent->subPlan */
                state->parent->subPlan = lappend(state->parent->subPlan,
                                                 sstate);

                scratch.opcode = EEOP_SUBPLAN;
                scratch.d.subplan.sstate = sstate;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_FieldSelect:
            {
                FieldSelect *fselect = (FieldSelect *) node;

                /* evaluate row/record argument into result area */
                ExecInitExprRec(fselect->arg, state, resv, resnull);

                /* and extract field */
                scratch.opcode = EEOP_FIELDSELECT;
                scratch.d.fieldselect.fieldnum = fselect->fieldnum;
                scratch.d.fieldselect.resulttype = fselect->resulttype;
                scratch.d.fieldselect.rowcache.cacheptr = NULL;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_FieldStore:
            {
                FieldStore *fstore = (FieldStore *) node;
                TupleDesc   tupDesc;
                ExprEvalRowtypeCache *rowcachep;
                Datum      *values;
                bool       *nulls;
                int         ncolumns;
                ListCell   *l1,
                           *l2;

                /* find out the number of columns in the composite type */
                tupDesc = lookup_rowtype_tupdesc(fstore->resulttype, -1);
                ncolumns = tupDesc->natts;
                DecrTupleDescRefCount(tupDesc);

                /* create workspace for column values */
                values = (Datum *) palloc(sizeof(Datum) * ncolumns);
                nulls = (bool *) palloc(sizeof(bool) * ncolumns);

                /* create shared composite-type-lookup cache struct */
                rowcachep = palloc(sizeof(ExprEvalRowtypeCache));
                rowcachep->cacheptr = NULL;

                /* emit code to evaluate the composite input value */
                ExecInitExprRec(fstore->arg, state, resv, resnull);

                /* next, deform the input tuple into our workspace */
                scratch.opcode = EEOP_FIELDSTORE_DEFORM;
                scratch.d.fieldstore.fstore = fstore;
                scratch.d.fieldstore.rowcache = rowcachep;
                scratch.d.fieldstore.values = values;
                scratch.d.fieldstore.nulls = nulls;
                scratch.d.fieldstore.ncolumns = ncolumns;
                ExprEvalPushStep(state, &scratch);

                /* evaluate new field values, store in workspace columns */
                forboth(l1, fstore->newvals, l2, fstore->fieldnums)
                {
                    Expr       *e = (Expr *) lfirst(l1);
                    AttrNumber  fieldnum = lfirst_int(l2);
                    Datum      *save_innermost_caseval;
                    bool       *save_innermost_casenull;

                    if (fieldnum <= 0 || fieldnum > ncolumns)
                        elog(ERROR, "field number %d is out of range in FieldStore",
                             fieldnum);

                    /*
                     * Use the CaseTestExpr mechanism to pass down the old
                     * value of the field being replaced; this is needed in
                     * case the newval is itself a FieldStore or
                     * SubscriptingRef that has to obtain and modify the old
                     * value.  It's safe to reuse the CASE mechanism because
                     * there cannot be a CASE between here and where the value
                     * would be needed, and a field assignment can't be within
                     * a CASE either.  (So saving and restoring
                     * innermost_caseval is just paranoia, but let's do it
                     * anyway.)
                     *
                     * Another non-obvious point is that it's safe to use the
                     * field's values[]/nulls[] entries as both the caseval
                     * source and the result address for this subexpression.
                     * That's okay only because (1) both FieldStore and
                     * SubscriptingRef evaluate their arg or refexpr inputs
                     * first, and (2) any such CaseTestExpr is directly the
                     * arg or refexpr input.  So any read of the caseval will
                     * occur before there's a chance to overwrite it.  Also,
                     * if multiple entries in the newvals/fieldnums lists
                     * target the same field, they'll effectively be applied
                     * left-to-right which is what we want.
                     */
                    save_innermost_caseval = state->innermost_caseval;
                    save_innermost_casenull = state->innermost_casenull;
                    state->innermost_caseval = &values[fieldnum - 1];
                    state->innermost_casenull = &nulls[fieldnum - 1];

                    ExecInitExprRec(e, state,
                                    &values[fieldnum - 1],
                                    &nulls[fieldnum - 1]);

                    state->innermost_caseval = save_innermost_caseval;
                    state->innermost_casenull = save_innermost_casenull;
                }

                /* finally, form result tuple */
                scratch.opcode = EEOP_FIELDSTORE_FORM;
                scratch.d.fieldstore.fstore = fstore;
                scratch.d.fieldstore.rowcache = rowcachep;
                scratch.d.fieldstore.values = values;
                scratch.d.fieldstore.nulls = nulls;
                scratch.d.fieldstore.ncolumns = ncolumns;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_RelabelType:
            {
                /* relabel doesn't need to do anything at runtime */
                RelabelType *relabel = (RelabelType *) node;

                ExecInitExprRec(relabel->arg, state, resv, resnull);
                break;
            }

        case T_CoerceViaIO:
            {
                CoerceViaIO *iocoerce = (CoerceViaIO *) node;
                Oid         iofunc;
                bool        typisvarlena;
                Oid         typioparam;
                FunctionCallInfo fcinfo_in;

                /* evaluate argument into step's result area */
                ExecInitExprRec(iocoerce->arg, state, resv, resnull);

                /*
                 * Prepare both output and input function calls, to be
                 * evaluated inside a single evaluation step for speed - this
                 * can be a very common operation.
                 *
                 * We don't check permissions here as a type's input/output
                 * function are assumed to be executable by everyone.
                 */
                scratch.opcode = EEOP_IOCOERCE;

                /* lookup the source type's output function */
                scratch.d.iocoerce.finfo_out = palloc0(sizeof(FmgrInfo));
                scratch.d.iocoerce.fcinfo_data_out = palloc0(SizeForFunctionCallInfo(1));

                getTypeOutputInfo(exprType((Node *) iocoerce->arg),
                                  &iofunc, &typisvarlena);
                fmgr_info(iofunc, scratch.d.iocoerce.finfo_out);
                fmgr_info_set_expr((Node *) node, scratch.d.iocoerce.finfo_out);
                InitFunctionCallInfoData(*scratch.d.iocoerce.fcinfo_data_out,
                                         scratch.d.iocoerce.finfo_out,
                                         1, InvalidOid, NULL, NULL);

                /* lookup the result type's input function */
                scratch.d.iocoerce.finfo_in = palloc0(sizeof(FmgrInfo));
                scratch.d.iocoerce.fcinfo_data_in = palloc0(SizeForFunctionCallInfo(3));

                getTypeInputInfo(iocoerce->resulttype,
                                 &iofunc, &typioparam);
                fmgr_info(iofunc, scratch.d.iocoerce.finfo_in);
                fmgr_info_set_expr((Node *) node, scratch.d.iocoerce.finfo_in);
                InitFunctionCallInfoData(*scratch.d.iocoerce.fcinfo_data_in,
                                         scratch.d.iocoerce.finfo_in,
                                         3, InvalidOid, NULL, NULL);

                /*
                 * We can preload the second and third arguments for the input
                 * function, since they're constants.
                 */
                fcinfo_in = scratch.d.iocoerce.fcinfo_data_in;
                fcinfo_in->args[1].value = ObjectIdGetDatum(typioparam);
                fcinfo_in->args[1].isnull = false;
                fcinfo_in->args[2].value = Int32GetDatum(-1);
                fcinfo_in->args[2].isnull = false;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ArrayCoerceExpr:
            {
                ArrayCoerceExpr *acoerce = (ArrayCoerceExpr *) node;
                Oid         resultelemtype;
                ExprState  *elemstate;

                /* evaluate argument into step's result area */
                ExecInitExprRec(acoerce->arg, state, resv, resnull);

                resultelemtype = get_element_type(acoerce->resulttype);
                if (!OidIsValid(resultelemtype))
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("target type is not an array")));

                /*
                 * Construct a sub-expression for the per-element expression;
                 * but don't ready it until after we check it for triviality.
                 * We assume it hasn't any Var references, but does have a
                 * CaseTestExpr representing the source array element values.
                 */
                elemstate = makeNode(ExprState);
                elemstate->expr = acoerce->elemexpr;
                elemstate->parent = state->parent;
                elemstate->ext_params = state->ext_params;

                elemstate->innermost_caseval = (Datum *) palloc(sizeof(Datum));
                elemstate->innermost_casenull = (bool *) palloc(sizeof(bool));

                ExecInitExprRec(acoerce->elemexpr, elemstate,
                                &elemstate->resvalue, &elemstate->resnull);

                if (elemstate->steps_len == 1 &&
                    elemstate->steps[0].opcode == EEOP_CASE_TESTVAL)
                {
                    /* Trivial, so we need no per-element work at runtime */
                    elemstate = NULL;
                }
                else
                {
                    /* Not trivial, so append a DONE step */
                    scratch.opcode = EEOP_DONE;
                    ExprEvalPushStep(elemstate, &scratch);
                    /* and ready the subexpression */
                    ExecReadyExpr(elemstate);
                }

                scratch.opcode = EEOP_ARRAYCOERCE;
                scratch.d.arraycoerce.elemexprstate = elemstate;
                scratch.d.arraycoerce.resultelemtype = resultelemtype;

                if (elemstate)
                {
                    /* Set up workspace for array_map */
                    scratch.d.arraycoerce.amstate =
                        (ArrayMapState *) palloc0(sizeof(ArrayMapState));
                }
                else
                {
                    /* Don't need workspace if there's no subexpression */
                    scratch.d.arraycoerce.amstate = NULL;
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ConvertRowtypeExpr:
            {
                ConvertRowtypeExpr *convert = (ConvertRowtypeExpr *) node;
                ExprEvalRowtypeCache *rowcachep;

                /* cache structs must be out-of-line for space reasons */
                rowcachep = palloc(2 * sizeof(ExprEvalRowtypeCache));
                rowcachep[0].cacheptr = NULL;
                rowcachep[1].cacheptr = NULL;

                /* evaluate argument into step's result area */
                ExecInitExprRec(convert->arg, state, resv, resnull);

                /* and push conversion step */
                scratch.opcode = EEOP_CONVERT_ROWTYPE;
                scratch.d.convert_rowtype.inputtype =
                    exprType((Node *) convert->arg);
                scratch.d.convert_rowtype.outputtype = convert->resulttype;
                scratch.d.convert_rowtype.incache = &rowcachep[0];
                scratch.d.convert_rowtype.outcache = &rowcachep[1];
                scratch.d.convert_rowtype.map = NULL;

                ExprEvalPushStep(state, &scratch);
                break;
            }

            /* note that CaseWhen expressions are handled within this block */
        case T_CaseExpr:
            {
                CaseExpr   *caseExpr = (CaseExpr *) node;
                List       *adjust_jumps = NIL;
                Datum      *caseval = NULL;
                bool       *casenull = NULL;
                ListCell   *lc;

                /*
                 * If there's a test expression, we have to evaluate it and
                 * save the value where the CaseTestExpr placeholders can find
                 * it.
                 */
                if (caseExpr->arg != NULL)
                {
                    /* Evaluate testexpr into caseval/casenull workspace */
                    caseval = palloc(sizeof(Datum));
                    casenull = palloc(sizeof(bool));

                    ExecInitExprRec(caseExpr->arg, state,
                                    caseval, casenull);

                    /*
                     * Since value might be read multiple times, force to R/O
                     * - but only if it could be an expanded datum.
                     */
                    if (get_typlen(exprType((Node *) caseExpr->arg)) == -1)
                    {
                        /* change caseval in-place */
                        scratch.opcode = EEOP_MAKE_READONLY;
                        scratch.resvalue = caseval;
                        scratch.resnull = casenull;
                        scratch.d.make_readonly.value = caseval;
                        scratch.d.make_readonly.isnull = casenull;
                        ExprEvalPushStep(state, &scratch);
                        /* restore normal settings of scratch fields */
                        scratch.resvalue = resv;
                        scratch.resnull = resnull;
                    }
                }

                /*
                 * Prepare to evaluate each of the WHEN clauses in turn; as
                 * soon as one is true we return the value of the
                 * corresponding THEN clause.  If none are true then we return
                 * the value of the ELSE clause, or NULL if there is none.
                 */
                foreach(lc, caseExpr->args)
                {
                    CaseWhen   *when = (CaseWhen *) lfirst(lc);
                    Datum      *save_innermost_caseval;
                    bool       *save_innermost_casenull;
                    int         whenstep;

                    /*
                     * Make testexpr result available to CaseTestExpr nodes
                     * within the condition.  We must save and restore prior
                     * setting of innermost_caseval fields, in case this node
                     * is itself within a larger CASE.
                     *
                     * If there's no test expression, we don't actually need
                     * to save and restore these fields; but it's less code to
                     * just do so unconditionally.
                     */
                    save_innermost_caseval = state->innermost_caseval;
                    save_innermost_casenull = state->innermost_casenull;
                    state->innermost_caseval = caseval;
                    state->innermost_casenull = casenull;

                    /* evaluate condition into CASE's result variables */
                    ExecInitExprRec(when->expr, state, resv, resnull);

                    state->innermost_caseval = save_innermost_caseval;
                    state->innermost_casenull = save_innermost_casenull;

                    /* If WHEN result isn't true, jump to next CASE arm */
                    scratch.opcode = EEOP_JUMP_IF_NOT_TRUE;
                    scratch.d.jump.jumpdone = -1;   /* computed later */
                    ExprEvalPushStep(state, &scratch);
                    whenstep = state->steps_len - 1;

                    /*
                     * If WHEN result is true, evaluate THEN result, storing
                     * it into the CASE's result variables.
                     */
                    ExecInitExprRec(when->result, state, resv, resnull);

                    /* Emit JUMP step to jump to end of CASE's code */
                    scratch.opcode = EEOP_JUMP;
                    scratch.d.jump.jumpdone = -1;   /* computed later */
                    ExprEvalPushStep(state, &scratch);

                    /*
                     * Don't know address for that jump yet, compute once the
                     * whole CASE expression is built.
                     */
                    adjust_jumps = lappend_int(adjust_jumps,
                                               state->steps_len - 1);

                    /*
                     * But we can set WHEN test's jump target now, to make it
                     * jump to the next WHEN subexpression or the ELSE.
                     */
                    state->steps[whenstep].d.jump.jumpdone = state->steps_len;
                }

                /* transformCaseExpr always adds a default */
                Assert(caseExpr->defresult);

                /* evaluate ELSE expr into CASE's result variables */
                ExecInitExprRec(caseExpr->defresult, state,
                                resv, resnull);

                /* adjust jump targets */
                foreach(lc, adjust_jumps)
                {
                    ExprEvalStep *as = &state->steps[lfirst_int(lc)];

                    Assert(as->opcode == EEOP_JUMP);
                    Assert(as->d.jump.jumpdone == -1);
                    as->d.jump.jumpdone = state->steps_len;
                }

                break;
            }

        case T_CaseTestExpr:
            {
                /*
                 * Read from location identified by innermost_caseval.  Note
                 * that innermost_caseval could be NULL, if this node isn't
                 * actually within a CaseExpr, ArrayCoerceExpr, etc structure.
                 * That can happen because some parts of the system abuse
                 * CaseTestExpr to cause a read of a value externally supplied
                 * in econtext->caseValue_datum.  We'll take care of that
                 * scenario at runtime.
                 */
                scratch.opcode = EEOP_CASE_TESTVAL;
                scratch.d.casetest.value = state->innermost_caseval;
                scratch.d.casetest.isnull = state->innermost_casenull;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ArrayExpr:
            {
                ArrayExpr  *arrayexpr = (ArrayExpr *) node;
                int         nelems = list_length(arrayexpr->elements);
                ListCell   *lc;
                int         elemoff;

                /*
                 * Evaluate by computing each element, and then forming the
                 * array.  Elements are computed into scratch arrays
                 * associated with the ARRAYEXPR step.
                 */
                scratch.opcode = EEOP_ARRAYEXPR;
                scratch.d.arrayexpr.elemvalues =
                    (Datum *) palloc(sizeof(Datum) * nelems);
                scratch.d.arrayexpr.elemnulls =
                    (bool *) palloc(sizeof(bool) * nelems);
                scratch.d.arrayexpr.nelems = nelems;

                /* fill remaining fields of step */
                scratch.d.arrayexpr.multidims = arrayexpr->multidims;
                scratch.d.arrayexpr.elemtype = arrayexpr->element_typeid;

                /* do one-time catalog lookup for type info */
                get_typlenbyvalalign(arrayexpr->element_typeid,
                                     &scratch.d.arrayexpr.elemlength,
                                     &scratch.d.arrayexpr.elembyval,
                                     &scratch.d.arrayexpr.elemalign);

                /* prepare to evaluate all arguments */
                elemoff = 0;
                foreach(lc, arrayexpr->elements)
                {
                    Expr       *e = (Expr *) lfirst(lc);

                    ExecInitExprRec(e, state,
                                    &scratch.d.arrayexpr.elemvalues[elemoff],
                                    &scratch.d.arrayexpr.elemnulls[elemoff]);
                    elemoff++;
                }

                /* and then collect all into an array */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_RowExpr:
            {
                RowExpr    *rowexpr = (RowExpr *) node;
                int         nelems = list_length(rowexpr->args);
                TupleDesc   tupdesc;
                int         i;
                ListCell   *l;

                /* Build tupdesc to describe result tuples */
                if (rowexpr->row_typeid == RECORDOID)
                {
                    /* generic record, use types of given expressions */
                    tupdesc = ExecTypeFromExprList(rowexpr->args);
                }
                else
                {
                    /* it's been cast to a named type, use that */
                    tupdesc = lookup_rowtype_tupdesc_copy(rowexpr->row_typeid, -1);
                }
                /* In either case, adopt RowExpr's column aliases */
                ExecTypeSetColNames(tupdesc, rowexpr->colnames);
                /* Bless the tupdesc in case it's now of type RECORD */
                BlessTupleDesc(tupdesc);

                /*
                 * In the named-type case, the tupdesc could have more columns
                 * than are in the args list, since the type might have had
                 * columns added since the ROW() was parsed.  We want those
                 * extra columns to go to nulls, so we make sure that the
                 * workspace arrays are large enough and then initialize any
                 * extra columns to read as NULLs.
                 */
                Assert(nelems <= tupdesc->natts);
                nelems = Max(nelems, tupdesc->natts);

                /*
                 * Evaluate by first building datums for each field, and then
                 * a final step forming the composite datum.
                 */
                scratch.opcode = EEOP_ROW;
                scratch.d.row.tupdesc = tupdesc;

                /* space for the individual field datums */
                scratch.d.row.elemvalues =
                    (Datum *) palloc(sizeof(Datum) * nelems);
                scratch.d.row.elemnulls =
                    (bool *) palloc(sizeof(bool) * nelems);
                /* as explained above, make sure any extra columns are null */
                memset(scratch.d.row.elemnulls, true, sizeof(bool) * nelems);

                /* Set up evaluation, skipping any deleted columns */
                i = 0;
                foreach(l, rowexpr->args)
                {
                    Form_pg_attribute att = TupleDescAttr(tupdesc, i);
                    Expr       *e = (Expr *) lfirst(l);

                    if (!att->attisdropped)
                    {
                        /*
                         * Guard against ALTER COLUMN TYPE on rowtype since
                         * the RowExpr was created.  XXX should we check
                         * typmod too?  Not sure we can be sure it'll be the
                         * same.
                         */
                        if (exprType((Node *) e) != att->atttypid)
                            ereport(ERROR,
                                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                                     errmsg("ROW() column has type %s instead of type %s",
                                            format_type_be(exprType((Node *) e)),
                                            format_type_be(att->atttypid))));
                    }
                    else
                    {
                        /*
                         * Ignore original expression and insert a NULL. We
                         * don't really care what type of NULL it is, so
                         * always make an int4 NULL.
                         */
                        e = (Expr *) makeNullConst(INT4OID, -1, InvalidOid);
                    }

                    /* Evaluate column expr into appropriate workspace slot */
                    ExecInitExprRec(e, state,
                                    &scratch.d.row.elemvalues[i],
                                    &scratch.d.row.elemnulls[i]);
                    i++;
                }

                /* And finally build the row value */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_RowCompareExpr:
            {
                RowCompareExpr *rcexpr = (RowCompareExpr *) node;
                int         nopers = list_length(rcexpr->opnos);
                List       *adjust_jumps = NIL;
                ListCell   *l_left_expr,
                           *l_right_expr,
                           *l_opno,
                           *l_opfamily,
                           *l_inputcollid;
                ListCell   *lc;

                /*
                 * Iterate over each field, prepare comparisons.  To handle
                 * NULL results, prepare jumps to after the expression.  If a
                 * comparison yields a != 0 result, jump to the final step.
                 */
                Assert(list_length(rcexpr->largs) == nopers);
                Assert(list_length(rcexpr->rargs) == nopers);
                Assert(list_length(rcexpr->opfamilies) == nopers);
                Assert(list_length(rcexpr->inputcollids) == nopers);

                forfive(l_left_expr, rcexpr->largs,
                        l_right_expr, rcexpr->rargs,
                        l_opno, rcexpr->opnos,
                        l_opfamily, rcexpr->opfamilies,
                        l_inputcollid, rcexpr->inputcollids)
                {
                    Expr       *left_expr = (Expr *) lfirst(l_left_expr);
                    Expr       *right_expr = (Expr *) lfirst(l_right_expr);
                    Oid         opno = lfirst_oid(l_opno);
                    Oid         opfamily = lfirst_oid(l_opfamily);
                    Oid         inputcollid = lfirst_oid(l_inputcollid);
                    int         strategy;
                    Oid         lefttype;
                    Oid         righttype;
                    Oid         proc;
                    FmgrInfo   *finfo;
                    FunctionCallInfo fcinfo;

                    get_op_opfamily_properties(opno, opfamily, false,
                                               &strategy,
                                               &lefttype,
                                               &righttype);
                    proc = get_opfamily_proc(opfamily,
                                             lefttype,
                                             righttype,
                                             BTORDER_PROC);
                    if (!OidIsValid(proc))
                        elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
                             BTORDER_PROC, lefttype, righttype, opfamily);

                    /* Set up the primary fmgr lookup information */
                    finfo = palloc0(sizeof(FmgrInfo));
                    fcinfo = palloc0(SizeForFunctionCallInfo(2));
                    fmgr_info(proc, finfo);
                    fmgr_info_set_expr((Node *) node, finfo);
                    InitFunctionCallInfoData(*fcinfo, finfo, 2,
                                             inputcollid, NULL, NULL);

                    /*
                     * If we enforced permissions checks on index support
                     * functions, we'd need to make a check here.  But the
                     * index support machinery doesn't do that, and thus
                     * neither does this code.
                     */

                    /* evaluate left and right args directly into fcinfo */
                    ExecInitExprRec(left_expr, state,
                                    &fcinfo->args[0].value, &fcinfo->args[0].isnull);
                    ExecInitExprRec(right_expr, state,
                                    &fcinfo->args[1].value, &fcinfo->args[1].isnull);

                    scratch.opcode = EEOP_ROWCOMPARE_STEP;
                    scratch.d.rowcompare_step.finfo = finfo;
                    scratch.d.rowcompare_step.fcinfo_data = fcinfo;
                    scratch.d.rowcompare_step.fn_addr = finfo->fn_addr;
                    /* jump targets filled below */
                    scratch.d.rowcompare_step.jumpnull = -1;
                    scratch.d.rowcompare_step.jumpdone = -1;

                    ExprEvalPushStep(state, &scratch);
                    adjust_jumps = lappend_int(adjust_jumps,
                                               state->steps_len - 1);
                }

                /*
                 * We could have a zero-column rowtype, in which case the rows
                 * necessarily compare equal.
                 */
                if (nopers == 0)
                {
                    scratch.opcode = EEOP_CONST;
                    scratch.d.constval.value = Int32GetDatum(0);
                    scratch.d.constval.isnull = false;
                    ExprEvalPushStep(state, &scratch);
                }

                /* Finally, examine the last comparison result */
                scratch.opcode = EEOP_ROWCOMPARE_FINAL;
                scratch.d.rowcompare_final.rctype = rcexpr->rctype;
                ExprEvalPushStep(state, &scratch);

                /* adjust jump targets */
                foreach(lc, adjust_jumps)
                {
                    ExprEvalStep *as = &state->steps[lfirst_int(lc)];

                    Assert(as->opcode == EEOP_ROWCOMPARE_STEP);
                    Assert(as->d.rowcompare_step.jumpdone == -1);
                    Assert(as->d.rowcompare_step.jumpnull == -1);

                    /* jump to comparison evaluation */
                    as->d.rowcompare_step.jumpdone = state->steps_len - 1;
                    /* jump to the following expression */
                    as->d.rowcompare_step.jumpnull = state->steps_len;
                }

                break;
            }

        case T_CoalesceExpr:
            {
                CoalesceExpr *coalesce = (CoalesceExpr *) node;
                List       *adjust_jumps = NIL;
                ListCell   *lc;

                /* We assume there's at least one arg */
                Assert(coalesce->args != NIL);

                /*
                 * Prepare evaluation of all coalesced arguments, after each
                 * one push a step that short-circuits if not null.
                 */
                foreach(lc, coalesce->args)
                {
                    Expr       *e = (Expr *) lfirst(lc);

                    /* evaluate argument, directly into result datum */
                    ExecInitExprRec(e, state, resv, resnull);

                    /* if it's not null, skip to end of COALESCE expr */
                    scratch.opcode = EEOP_JUMP_IF_NOT_NULL;
                    scratch.d.jump.jumpdone = -1;   /* adjust later */
                    ExprEvalPushStep(state, &scratch);

                    adjust_jumps = lappend_int(adjust_jumps,
                                               state->steps_len - 1);
                }

                /*
                 * No need to add a constant NULL return - we only can get to
                 * the end of the expression if a NULL already is being
                 * returned.
                 */

                /* adjust jump targets */
                foreach(lc, adjust_jumps)
                {
                    ExprEvalStep *as = &state->steps[lfirst_int(lc)];

                    Assert(as->opcode == EEOP_JUMP_IF_NOT_NULL);
                    Assert(as->d.jump.jumpdone == -1);
                    as->d.jump.jumpdone = state->steps_len;
                }

                break;
            }

        case T_MinMaxExpr:
            {
                MinMaxExpr *minmaxexpr = (MinMaxExpr *) node;
                int         nelems = list_length(minmaxexpr->args);
                TypeCacheEntry *typentry;
                FmgrInfo   *finfo;
                FunctionCallInfo fcinfo;
                ListCell   *lc;
                int         off;

                /* Look up the btree comparison function for the datatype */
                typentry = lookup_type_cache(minmaxexpr->minmaxtype,
                                             TYPECACHE_CMP_PROC);
                if (!OidIsValid(typentry->cmp_proc))
                    ereport(ERROR,
                            (errcode(ERRCODE_UNDEFINED_FUNCTION),
                             errmsg("could not identify a comparison function for type %s",
                                    format_type_be(minmaxexpr->minmaxtype))));

                /*
                 * If we enforced permissions checks on index support
                 * functions, we'd need to make a check here.  But the index
                 * support machinery doesn't do that, and thus neither does
                 * this code.
                 */

                /* Perform function lookup */
                finfo = palloc0(sizeof(FmgrInfo));
                fcinfo = palloc0(SizeForFunctionCallInfo(2));
                fmgr_info(typentry->cmp_proc, finfo);
                fmgr_info_set_expr((Node *) node, finfo);
                InitFunctionCallInfoData(*fcinfo, finfo, 2,
                                         minmaxexpr->inputcollid, NULL, NULL);

                scratch.opcode = EEOP_MINMAX;
                /* allocate space to store arguments */
                scratch.d.minmax.values =
                    (Datum *) palloc(sizeof(Datum) * nelems);
                scratch.d.minmax.nulls =
                    (bool *) palloc(sizeof(bool) * nelems);
                scratch.d.minmax.nelems = nelems;

                scratch.d.minmax.op = minmaxexpr->op;
                scratch.d.minmax.finfo = finfo;
                scratch.d.minmax.fcinfo_data = fcinfo;

                /* evaluate expressions into minmax->values/nulls */
                off = 0;
                foreach(lc, minmaxexpr->args)
                {
                    Expr       *e = (Expr *) lfirst(lc);

                    ExecInitExprRec(e, state,
                                    &scratch.d.minmax.values[off],
                                    &scratch.d.minmax.nulls[off]);
                    off++;
                }

                /* and push the final comparison */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_SQLValueFunction:
            {
                SQLValueFunction *svf = (SQLValueFunction *) node;

                scratch.opcode = EEOP_SQLVALUEFUNCTION;
                scratch.d.sqlvaluefunction.svf = svf;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_XmlExpr:
            {
                XmlExpr    *xexpr = (XmlExpr *) node;
                int         nnamed = list_length(xexpr->named_args);
                int         nargs = list_length(xexpr->args);
                int         off;
                ListCell   *arg;

                scratch.opcode = EEOP_XMLEXPR;
                scratch.d.xmlexpr.xexpr = xexpr;

                /* allocate space for storing all the arguments */
                if (nnamed)
                {
                    scratch.d.xmlexpr.named_argvalue =
                        (Datum *) palloc(sizeof(Datum) * nnamed);
                    scratch.d.xmlexpr.named_argnull =
                        (bool *) palloc(sizeof(bool) * nnamed);
                }
                else
                {
                    scratch.d.xmlexpr.named_argvalue = NULL;
                    scratch.d.xmlexpr.named_argnull = NULL;
                }

                if (nargs)
                {
                    scratch.d.xmlexpr.argvalue =
                        (Datum *) palloc(sizeof(Datum) * nargs);
                    scratch.d.xmlexpr.argnull =
                        (bool *) palloc(sizeof(bool) * nargs);
                }
                else
                {
                    scratch.d.xmlexpr.argvalue = NULL;
                    scratch.d.xmlexpr.argnull = NULL;
                }

                /* prepare argument execution */
                off = 0;
                foreach(arg, xexpr->named_args)
                {
                    Expr       *e = (Expr *) lfirst(arg);

                    ExecInitExprRec(e, state,
                                    &scratch.d.xmlexpr.named_argvalue[off],
                                    &scratch.d.xmlexpr.named_argnull[off]);
                    off++;
                }

                off = 0;
                foreach(arg, xexpr->args)
                {
                    Expr       *e = (Expr *) lfirst(arg);

                    ExecInitExprRec(e, state,
                                    &scratch.d.xmlexpr.argvalue[off],
                                    &scratch.d.xmlexpr.argnull[off]);
                    off++;
                }

                /* and evaluate the actual XML expression */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_NullTest:
            {
                NullTest   *ntest = (NullTest *) node;

                if (ntest->nulltesttype == IS_NULL)
                {
                    if (ntest->argisrow)
                        scratch.opcode = EEOP_NULLTEST_ROWISNULL;
                    else
                        scratch.opcode = EEOP_NULLTEST_ISNULL;
                }
                else if (ntest->nulltesttype == IS_NOT_NULL)
                {
                    if (ntest->argisrow)
                        scratch.opcode = EEOP_NULLTEST_ROWISNOTNULL;
                    else
                        scratch.opcode = EEOP_NULLTEST_ISNOTNULL;
                }
                else
                {
                    elog(ERROR, "unrecognized nulltesttype: %d",
                         (int) ntest->nulltesttype);
                }
                /* initialize cache in case it's a row test */
                scratch.d.nulltest_row.rowcache.cacheptr = NULL;

                /* first evaluate argument into result variable */
                ExecInitExprRec(ntest->arg, state,
                                resv, resnull);

                /* then push the test of that argument */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_BooleanTest:
            {
                BooleanTest *btest = (BooleanTest *) node;

                /*
                 * Evaluate argument, directly into result datum.  That's ok,
                 * because resv/resnull is definitely not used anywhere else,
                 * and will get overwritten by the below EEOP_BOOLTEST_IS_*
                 * step.
                 */
                ExecInitExprRec(btest->arg, state, resv, resnull);

                switch (btest->booltesttype)
                {
                    case IS_TRUE:
                        scratch.opcode = EEOP_BOOLTEST_IS_TRUE;
                        break;
                    case IS_NOT_TRUE:
                        scratch.opcode = EEOP_BOOLTEST_IS_NOT_TRUE;
                        break;
                    case IS_FALSE:
                        scratch.opcode = EEOP_BOOLTEST_IS_FALSE;
                        break;
                    case IS_NOT_FALSE:
                        scratch.opcode = EEOP_BOOLTEST_IS_NOT_FALSE;
                        break;
                    case IS_UNKNOWN:
                        /* Same as scalar IS NULL test */
                        scratch.opcode = EEOP_NULLTEST_ISNULL;
                        break;
                    case IS_NOT_UNKNOWN:
                        /* Same as scalar IS NOT NULL test */
                        scratch.opcode = EEOP_NULLTEST_ISNOTNULL;
                        break;
                    default:
                        elog(ERROR, "unrecognized booltesttype: %d",
                             (int) btest->booltesttype);
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_CoerceToDomain:
            {
                CoerceToDomain *ctest = (CoerceToDomain *) node;

                ExecInitCoerceToDomain(&scratch, ctest, state,
                                       resv, resnull);
                break;
            }

        case T_CoerceToDomainValue:
            {
                /*
                 * Read from location identified by innermost_domainval.  Note
                 * that innermost_domainval could be NULL, if we're compiling
                 * a standalone domain check rather than one embedded in a
                 * larger expression.  In that case we must read from
                 * econtext->domainValue_datum.  We'll take care of that
                 * scenario at runtime.
                 */
                scratch.opcode = EEOP_DOMAIN_TESTVAL;
                /* we share instruction union variant with case testval */
                scratch.d.casetest.value = state->innermost_domainval;
                scratch.d.casetest.isnull = state->innermost_domainnull;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_CurrentOfExpr:
            {
                scratch.opcode = EEOP_CURRENTOFEXPR;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_NextValueExpr:
            {
                NextValueExpr *nve = (NextValueExpr *) node;

                scratch.opcode = EEOP_NEXTVALUEEXPR;
                scratch.d.nextvalueexpr.seqid = nve->seqid;
                scratch.d.nextvalueexpr.seqtypid = nve->typeId;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        default:
            elog(ERROR, "unrecognized node type: %d",
                 (int) nodeTag(node));
            break;
    }
}

/*
 * Add another expression evaluation step to ExprState->steps.
 *
 * Note that this potentially re-allocates es->steps, therefore no pointer
 * into that array may be used while the expression is still being built.
 */
void
ExprEvalPushStep(ExprState *es, const ExprEvalStep *s)
{
    if (es->steps_alloc == 0)
    {
        es->steps_alloc = 16;
        es->steps = palloc(sizeof(ExprEvalStep) * es->steps_alloc);
    }
    else if (es->steps_alloc == es->steps_len)
    {
        es->steps_alloc *= 2;
        es->steps = repalloc(es->steps,
                             sizeof(ExprEvalStep) * es->steps_alloc);
    }

    memcpy(&es->steps[es->steps_len++], s, sizeof(ExprEvalStep));
}

/*
 * Perform setup necessary for the evaluation of a function-like expression,
 * appending argument evaluation steps to the steps list in *state, and
 * setting up *scratch so it is ready to be pushed.
 *
 * *scratch is not pushed here, so that callers may override the opcode,
 * which is useful for function-like cases like DISTINCT.
 */
static void
ExecInitFunc(ExprEvalStep *scratch, Expr *node, List *args, Oid funcid,
             Oid inputcollid, ExprState *state)
{
    int         nargs = list_length(args);
    AclResult   aclresult;
    FmgrInfo   *flinfo;
    FunctionCallInfo fcinfo;
    int         argno;
    ListCell   *lc;

    /* Check permission to call function */
    aclresult = pg_proc_aclcheck(funcid, GetUserId(), ACL_EXECUTE);
    if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, OBJECT_FUNCTION, get_func_name(funcid));
    InvokeFunctionExecuteHook(funcid);

    /*
     * Safety check on nargs.  Under normal circumstances this should never
     * fail, as parser should check sooner.  But possibly it might fail if
     * server has been compiled with FUNC_MAX_ARGS smaller than some functions
     * declared in pg_proc?
     */
    if (nargs > FUNC_MAX_ARGS)
        ereport(ERROR,
                (errcode(ERRCODE_TOO_MANY_ARGUMENTS),
                 errmsg_plural("cannot pass more than %d argument to a function",
                               "cannot pass more than %d arguments to a function",
                               FUNC_MAX_ARGS,
                               FUNC_MAX_ARGS)));

    /* Allocate function lookup data and parameter workspace for this call */
    scratch->d.func.finfo = palloc0(sizeof(FmgrInfo));
    scratch->d.func.fcinfo_data = palloc0(SizeForFunctionCallInfo(nargs));
    flinfo = scratch->d.func.finfo;
    fcinfo = scratch->d.func.fcinfo_data;

    /* Set up the primary fmgr lookup information */
    fmgr_info(funcid, flinfo);
    fmgr_info_set_expr((Node *) node, flinfo);

    /* Initialize function call parameter structure too */
    InitFunctionCallInfoData(*fcinfo, flinfo,
                             nargs, inputcollid, NULL, NULL);

    /* Keep extra copies of this info to save an indirection at runtime */
    scratch->d.func.fn_addr = flinfo->fn_addr;
    scratch->d.func.nargs = nargs;

    /* We only support non-set functions here */
    if (flinfo->fn_retset)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-valued function called in context that cannot accept a set"),
                 state->parent ?
                 executor_errposition(state->parent->state,
                                      exprLocation((Node *) node)) : 0));

    /* Build code to evaluate arguments directly into the fcinfo struct */
    argno = 0;
    foreach(lc, args)
    {
        Expr       *arg = (Expr *) lfirst(lc);

        if (IsA(arg, Const))
        {
            /*
             * Don't evaluate const arguments every round; especially
             * interesting for constants in comparisons.
             */
            Const      *con = (Const *) arg;

            fcinfo->args[argno].value = con->constvalue;
            fcinfo->args[argno].isnull = con->constisnull;
        }
        else
        {
            ExecInitExprRec(arg, state,
                            &fcinfo->args[argno].value,
                            &fcinfo->args[argno].isnull);
        }
        argno++;
    }

    /* Insert appropriate opcode depending on strictness and stats level */
    if (pgstat_track_functions <= flinfo->fn_stats)
    {
        if (flinfo->fn_strict && nargs > 0)
            scratch->opcode = EEOP_FUNCEXPR_STRICT;
        else
            scratch->opcode = EEOP_FUNCEXPR;
    }
    else
    {
        if (flinfo->fn_strict && nargs > 0)
            scratch->opcode = EEOP_FUNCEXPR_STRICT_FUSAGE;
        else
            scratch->opcode = EEOP_FUNCEXPR_FUSAGE;
    }
}

/*
 * Add expression steps deforming the ExprState's inner/outer/scan slots
 * as much as required by the expression.
 */
static void
ExecInitExprSlots(ExprState *state, Node *node)
{
    LastAttnumInfo info = {0, 0, 0};

    /*
     * Figure out which attributes we're going to need.
     */
    get_last_attnums_walker(node, &info);

    ExecPushExprSlots(state, &info);
}

/*
 * Add steps deforming the ExprState's inner/out/scan slots as much as
 * indicated by info. This is useful when building an ExprState covering more
 * than one expression.
 */
static void
ExecPushExprSlots(ExprState *state, LastAttnumInfo *info)
{
    ExprEvalStep scratch = {0};

    scratch.resvalue = NULL;
    scratch.resnull = NULL;

    /* Emit steps as needed */
    if (info->last_inner > 0)
    {
        scratch.opcode = EEOP_INNER_FETCHSOME;
        scratch.d.fetch.last_var = info->last_inner;
        scratch.d.fetch.fixed = false;
        scratch.d.fetch.kind = NULL;
        scratch.d.fetch.known_desc = NULL;
        if (ExecComputeSlotInfo(state, &scratch))
            ExprEvalPushStep(state, &scratch);
    }
    if (info->last_outer > 0)
    {
        scratch.opcode = EEOP_OUTER_FETCHSOME;
        scratch.d.fetch.last_var = info->last_outer;
        scratch.d.fetch.fixed = false;
        scratch.d.fetch.kind = NULL;
        scratch.d.fetch.known_desc = NULL;
        if (ExecComputeSlotInfo(state, &scratch))
            ExprEvalPushStep(state, &scratch);
    }
    if (info->last_scan > 0)
    {
        scratch.opcode = EEOP_SCAN_FETCHSOME;
        scratch.d.fetch.last_var = info->last_scan;
        scratch.d.fetch.fixed = false;
        scratch.d.fetch.kind = NULL;
        scratch.d.fetch.known_desc = NULL;
        if (ExecComputeSlotInfo(state, &scratch))
            ExprEvalPushStep(state, &scratch);
    }
}

/*
 * get_last_attnums_walker: expression walker for ExecInitExprSlots
 */
static bool
get_last_attnums_walker(Node *node, LastAttnumInfo *info)
{
    if (node == NULL)
        return false;
    if (IsA(node, Var))
    {
        Var        *variable = (Var *) node;
        AttrNumber  attnum = variable->varattno;

        switch (variable->varno)
        {
            case INNER_VAR:
                info->last_inner = Max(info->last_inner, attnum);
                break;

            case OUTER_VAR:
                info->last_outer = Max(info->last_outer, attnum);
                break;

                /* INDEX_VAR is handled by default case */

            default:
                info->last_scan = Max(info->last_scan, attnum);
                break;
        }
        return false;
    }

    /*
     * Don't examine the arguments or filters of Aggrefs or WindowFuncs,
     * because those do not represent expressions to be evaluated within the
     * calling expression's econtext.  GroupingFunc arguments are never
     * evaluated at all.
     */
    if (IsA(node, Aggref))
        return false;
    if (IsA(node, WindowFunc))
        return false;
    if (IsA(node, GroupingFunc))
        return false;
    return expression_tree_walker(node, get_last_attnums_walker,
                                  (void *) info);
}

/*
 * Compute additional information for EEOP_*_FETCHSOME ops.
 *
 * The goal is to determine whether a slot is 'fixed', that is, every
 * evaluation of the expression will have the same type of slot, with an
 * equivalent descriptor.
 *
 * Returns true if the deforming step is required, false otherwise.
 */
static bool
ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op)
{
    PlanState  *parent = state->parent;
    TupleDesc   desc = NULL;
    const TupleTableSlotOps *tts_ops = NULL;
    bool        isfixed = false;
    ExprEvalOp  opcode = op->opcode;

    Assert(opcode == EEOP_INNER_FETCHSOME ||
           opcode == EEOP_OUTER_FETCHSOME ||
           opcode == EEOP_SCAN_FETCHSOME);

    if (op->d.fetch.known_desc != NULL)
    {
        desc = op->d.fetch.known_desc;
        tts_ops = op->d.fetch.kind;
        isfixed = op->d.fetch.kind != NULL;
    }
    else if (!parent)
    {
        isfixed = false;
    }
    else if (opcode == EEOP_INNER_FETCHSOME)
    {
        PlanState  *is = innerPlanState(parent);

        if (parent->inneropsset && !parent->inneropsfixed)
        {
            isfixed = false;
        }
        else if (parent->inneropsset && parent->innerops)
        {
            isfixed = true;
            tts_ops = parent->innerops;
            desc = ExecGetResultType(is);
        }
        else if (is)
        {
            tts_ops = ExecGetResultSlotOps(is, &isfixed);
            desc = ExecGetResultType(is);
        }
    }
    else if (opcode == EEOP_OUTER_FETCHSOME)
    {
        PlanState  *os = outerPlanState(parent);

        if (parent->outeropsset && !parent->outeropsfixed)
        {
            isfixed = false;
        }
        else if (parent->outeropsset && parent->outerops)
        {
            isfixed = true;
            tts_ops = parent->outerops;
            desc = ExecGetResultType(os);
        }
        else if (os)
        {
            tts_ops = ExecGetResultSlotOps(os, &isfixed);
            desc = ExecGetResultType(os);
        }
    }
    else if (opcode == EEOP_SCAN_FETCHSOME)
    {
        desc = parent->scandesc;

        if (parent->scanops)
            tts_ops = parent->scanops;

        if (parent->scanopsset)
            isfixed = parent->scanopsfixed;
    }

    if (isfixed && desc != NULL && tts_ops != NULL)
    {
        op->d.fetch.fixed = true;
        op->d.fetch.kind = tts_ops;
        op->d.fetch.known_desc = desc;
    }
    else
    {
        op->d.fetch.fixed = false;
        op->d.fetch.kind = NULL;
        op->d.fetch.known_desc = NULL;
    }

    /* if the slot is known to always virtual we never need to deform */
    if (op->d.fetch.fixed && op->d.fetch.kind == &TTSOpsVirtual)
        return false;

    return true;
}

/*
 * Prepare step for the evaluation of a whole-row variable.
 * The caller still has to push the step.
 */
static void
ExecInitWholeRowVar(ExprEvalStep *scratch, Var *variable, ExprState *state)
{
    PlanState  *parent = state->parent;

    /* fill in all but the target */
    scratch->opcode = EEOP_WHOLEROW;
    scratch->d.wholerow.var = variable;
    scratch->d.wholerow.first = true;
    scratch->d.wholerow.slow = false;
    scratch->d.wholerow.tupdesc = NULL; /* filled at runtime */
    scratch->d.wholerow.junkFilter = NULL;

    /*
     * If the input tuple came from a subquery, it might contain "resjunk"
     * columns (such as GROUP BY or ORDER BY columns), which we don't want to
     * keep in the whole-row result.  We can get rid of such columns by
     * passing the tuple through a JunkFilter --- but to make one, we have to
     * lay our hands on the subquery's targetlist.  Fortunately, there are not
     * very many cases where this can happen, and we can identify all of them
     * by examining our parent PlanState.  We assume this is not an issue in
     * standalone expressions that don't have parent plans.  (Whole-row Vars
     * can occur in such expressions, but they will always be referencing
     * table rows.)
     */
    if (parent)
    {
        PlanState  *subplan = NULL;

        switch (nodeTag(parent))
        {
            case T_SubqueryScanState:
                subplan = ((SubqueryScanState *) parent)->subplan;
                break;
            case T_CteScanState:
                subplan = ((CteScanState *) parent)->cteplanstate;
                break;
            default:
                break;
        }

        if (subplan)
        {
            bool        junk_filter_needed = false;
            ListCell   *tlist;

            /* Detect whether subplan tlist actually has any junk columns */
            foreach(tlist, subplan->plan->targetlist)
            {
                TargetEntry *tle = (TargetEntry *) lfirst(tlist);

                if (tle->resjunk)
                {
                    junk_filter_needed = true;
                    break;
                }
            }

            /* If so, build the junkfilter now */
            if (junk_filter_needed)
            {
                scratch->d.wholerow.junkFilter =
                    ExecInitJunkFilter(subplan->plan->targetlist,
                                       ExecInitExtraTupleSlot(parent->state, NULL,
                                                              &TTSOpsVirtual));
            }
        }
    }
}

/*
 * Prepare evaluation of a SubscriptingRef expression.
 */
static void
ExecInitSubscriptingRef(ExprEvalStep *scratch, SubscriptingRef *sbsref,
                        ExprState *state, Datum *resv, bool *resnull)
{
    bool        isAssignment = (sbsref->refassgnexpr != NULL);
    int         nupper = list_length(sbsref->refupperindexpr);
    int         nlower = list_length(sbsref->reflowerindexpr);
    const SubscriptRoutines *sbsroutines;
    SubscriptingRefState *sbsrefstate;
    SubscriptExecSteps methods;
    char       *ptr;
    List       *adjust_jumps = NIL;
    ListCell   *lc;
    int         i;

    /* Look up the subscripting support methods */
    sbsroutines = getSubscriptingRoutines(sbsref->refcontainertype, NULL);
    if (!sbsroutines)
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("cannot subscript type %s because it does not support subscripting",
                        format_type_be(sbsref->refcontainertype)),
                 state->parent ?
                 executor_errposition(state->parent->state,
                                      exprLocation((Node *) sbsref)) : 0));

    /* Allocate sbsrefstate, with enough space for per-subscript arrays too */
    sbsrefstate = palloc0(MAXALIGN(sizeof(SubscriptingRefState)) +
                          (nupper + nlower) * (sizeof(Datum) +
                                               2 * sizeof(bool)));

    /* Fill constant fields of SubscriptingRefState */
    sbsrefstate->isassignment = isAssignment;
    sbsrefstate->numupper = nupper;
    sbsrefstate->numlower = nlower;
    /* Set up per-subscript arrays */
    ptr = ((char *) sbsrefstate) + MAXALIGN(sizeof(SubscriptingRefState));
    sbsrefstate->upperindex = (Datum *) ptr;
    ptr += nupper * sizeof(Datum);
    sbsrefstate->lowerindex = (Datum *) ptr;
    ptr += nlower * sizeof(Datum);
    sbsrefstate->upperprovided = (bool *) ptr;
    ptr += nupper * sizeof(bool);
    sbsrefstate->lowerprovided = (bool *) ptr;
    ptr += nlower * sizeof(bool);
    sbsrefstate->upperindexnull = (bool *) ptr;
    ptr += nupper * sizeof(bool);
    sbsrefstate->lowerindexnull = (bool *) ptr;
    /* ptr += nlower * sizeof(bool); */

    /*
     * Let the container-type-specific code have a chance.  It must fill the
     * "methods" struct with function pointers for us to possibly use in
     * execution steps below; and it can optionally set up some data pointed
     * to by the workspace field.
     */
    memset(&methods, 0, sizeof(methods));
    sbsroutines->exec_setup(sbsref, sbsrefstate, &methods);

    /*
     * Evaluate array input.  It's safe to do so into resv/resnull, because we
     * won't use that as target for any of the other subexpressions, and it'll
     * be overwritten by the final EEOP_SBSREF_FETCH/ASSIGN step, which is
     * pushed last.
     */
    ExecInitExprRec(sbsref->refexpr, state, resv, resnull);

    /*
     * If refexpr yields NULL, and the operation should be strict, then result
     * is NULL.  We can implement this with just JUMP_IF_NULL, since we
     * evaluated the array into the desired target location.
     */
    if (!isAssignment && sbsroutines->fetch_strict)
    {
        scratch->opcode = EEOP_JUMP_IF_NULL;
        scratch->d.jump.jumpdone = -1;  /* adjust later */
        ExprEvalPushStep(state, scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
    }

    /* Evaluate upper subscripts */
    i = 0;
    foreach(lc, sbsref->refupperindexpr)
    {
        Expr       *e = (Expr *) lfirst(lc);

        /* When slicing, individual subscript bounds can be omitted */
        if (!e)
        {
            sbsrefstate->upperprovided[i] = false;
            sbsrefstate->upperindexnull[i] = true;
        }
        else
        {
            sbsrefstate->upperprovided[i] = true;
            /* Each subscript is evaluated into appropriate array entry */
            ExecInitExprRec(e, state,
                            &sbsrefstate->upperindex[i],
                            &sbsrefstate->upperindexnull[i]);
        }
        i++;
    }

    /* Evaluate lower subscripts similarly */
    i = 0;
    foreach(lc, sbsref->reflowerindexpr)
    {
        Expr       *e = (Expr *) lfirst(lc);

        /* When slicing, individual subscript bounds can be omitted */
        if (!e)
        {
            sbsrefstate->lowerprovided[i] = false;
            sbsrefstate->lowerindexnull[i] = true;
        }
        else
        {
            sbsrefstate->lowerprovided[i] = true;
            /* Each subscript is evaluated into appropriate array entry */
            ExecInitExprRec(e, state,
                            &sbsrefstate->lowerindex[i],
                            &sbsrefstate->lowerindexnull[i]);
        }
        i++;
    }

    /* SBSREF_SUBSCRIPTS checks and converts all the subscripts at once */
    if (methods.sbs_check_subscripts)
    {
        scratch->opcode = EEOP_SBSREF_SUBSCRIPTS;
        scratch->d.sbsref_subscript.subscriptfunc = methods.sbs_check_subscripts;
        scratch->d.sbsref_subscript.state = sbsrefstate;
        scratch->d.sbsref_subscript.jumpdone = -1;  /* adjust later */
        ExprEvalPushStep(state, scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
    }

    if (isAssignment)
    {
        Datum      *save_innermost_caseval;
        bool       *save_innermost_casenull;

        /* Check for unimplemented methods */
        if (!methods.sbs_assign)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("type %s does not support subscripted assignment",
                            format_type_be(sbsref->refcontainertype))));

        /*
         * We might have a nested-assignment situation, in which the
         * refassgnexpr is itself a FieldStore or SubscriptingRef that needs
         * to obtain and modify the previous value of the array element or
         * slice being replaced.  If so, we have to extract that value from
         * the array and pass it down via the CaseTestExpr mechanism.  It's
         * safe to reuse the CASE mechanism because there cannot be a CASE
         * between here and where the value would be needed, and an array
         * assignment can't be within a CASE either.  (So saving and restoring
         * innermost_caseval is just paranoia, but let's do it anyway.)
         *
         * Since fetching the old element might be a nontrivial expense, do it
         * only if the argument actually needs it.
         */
        if (isAssignmentIndirectionExpr(sbsref->refassgnexpr))
        {
            if (!methods.sbs_fetch_old)
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("type %s does not support subscripted assignment",
                                format_type_be(sbsref->refcontainertype))));
            scratch->opcode = EEOP_SBSREF_OLD;
            scratch->d.sbsref.subscriptfunc = methods.sbs_fetch_old;
            scratch->d.sbsref.state = sbsrefstate;
            ExprEvalPushStep(state, scratch);
        }

        /* SBSREF_OLD puts extracted value into prevvalue/prevnull */
        save_innermost_caseval = state->innermost_caseval;
        save_innermost_casenull = state->innermost_casenull;
        state->innermost_caseval = &sbsrefstate->prevvalue;
        state->innermost_casenull = &sbsrefstate->prevnull;

        /* evaluate replacement value into replacevalue/replacenull */
        ExecInitExprRec(sbsref->refassgnexpr, state,
                        &sbsrefstate->replacevalue, &sbsrefstate->replacenull);

        state->innermost_caseval = save_innermost_caseval;
        state->innermost_casenull = save_innermost_casenull;

        /* and perform the assignment */
        scratch->opcode = EEOP_SBSREF_ASSIGN;
        scratch->d.sbsref.subscriptfunc = methods.sbs_assign;
        scratch->d.sbsref.state = sbsrefstate;
        ExprEvalPushStep(state, scratch);
    }
    else
    {
        /* array fetch is much simpler */
        scratch->opcode = EEOP_SBSREF_FETCH;
        scratch->d.sbsref.subscriptfunc = methods.sbs_fetch;
        scratch->d.sbsref.state = sbsrefstate;
        ExprEvalPushStep(state, scratch);
    }

    /* adjust jump targets */
    foreach(lc, adjust_jumps)
    {
        ExprEvalStep *as = &state->steps[lfirst_int(lc)];

        if (as->opcode == EEOP_SBSREF_SUBSCRIPTS)
        {
            Assert(as->d.sbsref_subscript.jumpdone == -1);
            as->d.sbsref_subscript.jumpdone = state->steps_len;
        }
        else
        {
            Assert(as->opcode == EEOP_JUMP_IF_NULL);
            Assert(as->d.jump.jumpdone == -1);
            as->d.jump.jumpdone = state->steps_len;
        }
    }
}

/*
 * Helper for preparing SubscriptingRef expressions for evaluation: is expr
 * a nested FieldStore or SubscriptingRef that needs the old element value
 * passed down?
 *
 * (We could use this in FieldStore too, but in that case passing the old
 * value is so cheap there's no need.)
 *
 * Note: it might seem that this needs to recurse, but in most cases it does
 * not; the CaseTestExpr, if any, will be directly the arg or refexpr of the
 * top-level node.  Nested-assignment situations give rise to expression
 * trees in which each level of assignment has its own CaseTestExpr, and the
 * recursive structure appears within the newvals or refassgnexpr field.
 * There is an exception, though: if the array is an array-of-domain, we will
 * have a CoerceToDomain as the refassgnexpr, and we need to be able to look
 * through that.
 */
static bool
isAssignmentIndirectionExpr(Expr *expr)
{
    if (expr == NULL)
        return false;           /* just paranoia */
    if (IsA(expr, FieldStore))
    {
        FieldStore *fstore = (FieldStore *) expr;

        if (fstore->arg && IsA(fstore->arg, CaseTestExpr))
            return true;
    }
    else if (IsA(expr, SubscriptingRef))
    {
        SubscriptingRef *sbsRef = (SubscriptingRef *) expr;

        if (sbsRef->refexpr && IsA(sbsRef->refexpr, CaseTestExpr))
            return true;
    }
    else if (IsA(expr, CoerceToDomain))
    {
        CoerceToDomain *cd = (CoerceToDomain *) expr;

        return isAssignmentIndirectionExpr(cd->arg);
    }
    return false;
}

/*
 * Prepare evaluation of a CoerceToDomain expression.
 */
static void
ExecInitCoerceToDomain(ExprEvalStep *scratch, CoerceToDomain *ctest,
                       ExprState *state, Datum *resv, bool *resnull)
{
    DomainConstraintRef *constraint_ref;
    ListCell   *l;

    scratch->d.domaincheck.resulttype = ctest->resulttype;
    /* we'll allocate workspace only if needed */
    scratch->d.domaincheck.checkvalue = NULL;
    scratch->d.domaincheck.checknull = NULL;

    /*
     * Evaluate argument - it's fine to directly store it into resv/resnull,
     * if there's constraint failures there'll be errors, otherwise it's what
     * needs to be returned.
     */
    ExecInitExprRec(ctest->arg, state, resv, resnull);

    /*
     * Note: if the argument is of varlena type, it could be a R/W expanded
     * object.  We want to return the R/W pointer as the final result, but we
     * have to pass a R/O pointer as the value to be tested by any functions
     * in check expressions.  We don't bother to emit a MAKE_READONLY step
     * unless there's actually at least one check expression, though.  Until
     * we've tested that, domainval/domainnull are NULL.
     */

    /*
     * Collect the constraints associated with the domain.
     *
     * Note: before PG v10 we'd recheck the set of constraints during each
     * evaluation of the expression.  Now we bake them into the ExprState
     * during executor initialization.  That means we don't need typcache.c to
     * provide compiled exprs.
     */
    constraint_ref = (DomainConstraintRef *)
        palloc(sizeof(DomainConstraintRef));
    InitDomainConstraintRef(ctest->resulttype,
                            constraint_ref,
                            CurrentMemoryContext,
                            false);

    /*
     * Compile code to check each domain constraint.  NOTNULL constraints can
     * just be applied on the resv/resnull value, but for CHECK constraints we
     * need more pushups.
     */
    foreach(l, constraint_ref->constraints)
    {
        DomainConstraintState *con = (DomainConstraintState *) lfirst(l);
        Datum      *domainval = NULL;
        bool       *domainnull = NULL;
        Datum      *save_innermost_domainval;
        bool       *save_innermost_domainnull;

        scratch->d.domaincheck.constraintname = con->name;

        switch (con->constrainttype)
        {
            case DOM_CONSTRAINT_NOTNULL:
                scratch->opcode = EEOP_DOMAIN_NOTNULL;
                ExprEvalPushStep(state, scratch);
                break;
            case DOM_CONSTRAINT_CHECK:
                /* Allocate workspace for CHECK output if we didn't yet */
                if (scratch->d.domaincheck.checkvalue == NULL)
                {
                    scratch->d.domaincheck.checkvalue =
                        (Datum *) palloc(sizeof(Datum));
                    scratch->d.domaincheck.checknull =
                        (bool *) palloc(sizeof(bool));
                }

                /*
                 * If first time through, determine where CoerceToDomainValue
                 * nodes should read from.
                 */
                if (domainval == NULL)
                {
                    /*
                     * Since value might be read multiple times, force to R/O
                     * - but only if it could be an expanded datum.
                     */
                    if (get_typlen(ctest->resulttype) == -1)
                    {
                        ExprEvalStep scratch2 = {0};

                        /* Yes, so make output workspace for MAKE_READONLY */
                        domainval = (Datum *) palloc(sizeof(Datum));
                        domainnull = (bool *) palloc(sizeof(bool));

                        /* Emit MAKE_READONLY */
                        scratch2.opcode = EEOP_MAKE_READONLY;
                        scratch2.resvalue = domainval;
                        scratch2.resnull = domainnull;
                        scratch2.d.make_readonly.value = resv;
                        scratch2.d.make_readonly.isnull = resnull;
                        ExprEvalPushStep(state, &scratch2);
                    }
                    else
                    {
                        /* No, so it's fine to read from resv/resnull */
                        domainval = resv;
                        domainnull = resnull;
                    }
                }

                /*
                 * Set up value to be returned by CoerceToDomainValue nodes.
                 * We must save and restore innermost_domainval/null fields,
                 * in case this node is itself within a check expression for
                 * another domain.
                 */
                save_innermost_domainval = state->innermost_domainval;
                save_innermost_domainnull = state->innermost_domainnull;
                state->innermost_domainval = domainval;
                state->innermost_domainnull = domainnull;

                /* evaluate check expression value */
                ExecInitExprRec(con->check_expr, state,
                                scratch->d.domaincheck.checkvalue,
                                scratch->d.domaincheck.checknull);

                state->innermost_domainval = save_innermost_domainval;
                state->innermost_domainnull = save_innermost_domainnull;

                /* now test result */
                scratch->opcode = EEOP_DOMAIN_CHECK;
                ExprEvalPushStep(state, scratch);

                break;
            default:
                elog(ERROR, "unrecognized constraint type: %d",
                     (int) con->constrainttype);
                break;
        }
    }
}

/*
 * Build transition/combine function invocations for all aggregate transition
 * / combination function invocations in a grouping sets phase. This has to
 * invoke all sort based transitions in a phase (if doSort is true), all hash
 * based transitions (if doHash is true), or both (both true).
 *
 * The resulting expression will, for each set of transition values, first
 * check for filters, evaluate aggregate input, check that that input is not
 * NULL for a strict transition function, and then finally invoke the
 * transition for each of the concurrently computed grouping sets.
 *
 * If nullcheck is true, the generated code will check for a NULL pointer to
 * the array of AggStatePerGroup, and skip evaluation if so.
 */
ExprState *
ExecBuildAggTrans(AggState *aggstate, AggStatePerPhase phase,
                  bool doSort, bool doHash, bool nullcheck)
{
    ExprState  *state = makeNode(ExprState);
    PlanState  *parent = &aggstate->ss.ps;
    ExprEvalStep scratch = {0};
    bool        isCombine = DO_AGGSPLIT_COMBINE(aggstate->aggsplit);
    LastAttnumInfo deform = {0, 0, 0};

    state->expr = (Expr *) aggstate;
    state->parent = parent;

    scratch.resvalue = &state->resvalue;
    scratch.resnull = &state->resnull;

    /*
     * First figure out which slots, and how many columns from each, we're
     * going to need.
     */
    for (int transno = 0; transno < aggstate->numtrans; transno++)
    {
        AggStatePerTrans pertrans = &aggstate->pertrans[transno];

        get_last_attnums_walker((Node *) pertrans->aggref->aggdirectargs,
                                &deform);
        get_last_attnums_walker((Node *) pertrans->aggref->args,
                                &deform);
        get_last_attnums_walker((Node *) pertrans->aggref->aggorder,
                                &deform);
        get_last_attnums_walker((Node *) pertrans->aggref->aggdistinct,
                                &deform);
        get_last_attnums_walker((Node *) pertrans->aggref->aggfilter,
                                &deform);
    }
    ExecPushExprSlots(state, &deform);

    /*
     * Emit instructions for each transition value / grouping set combination.
     */
    for (int transno = 0; transno < aggstate->numtrans; transno++)
    {
        AggStatePerTrans pertrans = &aggstate->pertrans[transno];
        FunctionCallInfo trans_fcinfo = pertrans->transfn_fcinfo;
        List       *adjust_bailout = NIL;
        NullableDatum *strictargs = NULL;
        bool       *strictnulls = NULL;
        int         argno;
        ListCell   *bail;

        /*
         * If filter present, emit. Do so before evaluating the input, to
         * avoid potentially unneeded computations, or even worse, unintended
         * side-effects.  When combining, all the necessary filtering has
         * already been done.
         */
        if (pertrans->aggref->aggfilter && !isCombine)
        {
            /* evaluate filter expression */
            ExecInitExprRec(pertrans->aggref->aggfilter, state,
                            &state->resvalue, &state->resnull);
            /* and jump out if false */
            scratch.opcode = EEOP_JUMP_IF_NOT_TRUE;
            scratch.d.jump.jumpdone = -1;   /* adjust later */
            ExprEvalPushStep(state, &scratch);
            adjust_bailout = lappend_int(adjust_bailout,
                                         state->steps_len - 1);
        }

        /*
         * Evaluate arguments to aggregate/combine function.
         */
        argno = 0;
        if (isCombine)
        {
            /*
             * Combining two aggregate transition values. Instead of directly
             * coming from a tuple the input is a, potentially deserialized,
             * transition value.
             */
            TargetEntry *source_tle;

            Assert(pertrans->numSortCols == 0);
            Assert(list_length(pertrans->aggref->args) == 1);

            strictargs = trans_fcinfo->args + 1;
            source_tle = (TargetEntry *) linitial(pertrans->aggref->args);

            /*
             * deserialfn_oid will be set if we must deserialize the input
             * state before calling the combine function.
             */
            if (!OidIsValid(pertrans->deserialfn_oid))
            {
                /*
                 * Start from 1, since the 0th arg will be the transition
                 * value
                 */
                ExecInitExprRec(source_tle->expr, state,
                                &trans_fcinfo->args[argno + 1].value,
                                &trans_fcinfo->args[argno + 1].isnull);
            }
            else
            {
                FunctionCallInfo ds_fcinfo = pertrans->deserialfn_fcinfo;

                /* evaluate argument */
                ExecInitExprRec(source_tle->expr, state,
                                &ds_fcinfo->args[0].value,
                                &ds_fcinfo->args[0].isnull);

                /* Dummy second argument for type-safety reasons */
                ds_fcinfo->args[1].value = PointerGetDatum(NULL);
                ds_fcinfo->args[1].isnull = false;

                /*
                 * Don't call a strict deserialization function with NULL
                 * input
                 */
                if (pertrans->deserialfn.fn_strict)
                    scratch.opcode = EEOP_AGG_STRICT_DESERIALIZE;
                else
                    scratch.opcode = EEOP_AGG_DESERIALIZE;

                scratch.d.agg_deserialize.fcinfo_data = ds_fcinfo;
                scratch.d.agg_deserialize.jumpnull = -1;    /* adjust later */
                scratch.resvalue = &trans_fcinfo->args[argno + 1].value;
                scratch.resnull = &trans_fcinfo->args[argno + 1].isnull;

                ExprEvalPushStep(state, &scratch);
                /* don't add an adjustment unless the function is strict */
                if (pertrans->deserialfn.fn_strict)
                    adjust_bailout = lappend_int(adjust_bailout,
                                                 state->steps_len - 1);

                /* restore normal settings of scratch fields */
                scratch.resvalue = &state->resvalue;
                scratch.resnull = &state->resnull;
            }
            argno++;
        }
        else if (pertrans->numSortCols == 0)
        {
            ListCell   *arg;

            /*
             * Normal transition function without ORDER BY / DISTINCT.
             */
            strictargs = trans_fcinfo->args + 1;

            foreach(arg, pertrans->aggref->args)
            {
                TargetEntry *source_tle = (TargetEntry *) lfirst(arg);

                /*
                 * Start from 1, since the 0th arg will be the transition
                 * value
                 */
                ExecInitExprRec(source_tle->expr, state,
                                &trans_fcinfo->args[argno + 1].value,
                                &trans_fcinfo->args[argno + 1].isnull);
                argno++;
            }
        }
        else if (pertrans->numInputs == 1)
        {
            /*
             * DISTINCT and/or ORDER BY case, with a single column sorted on.
             */
            TargetEntry *source_tle =
            (TargetEntry *) linitial(pertrans->aggref->args);

            Assert(list_length(pertrans->aggref->args) == 1);

            ExecInitExprRec(source_tle->expr, state,
                            &state->resvalue,
                            &state->resnull);
            strictnulls = &state->resnull;
            argno++;
        }
        else
        {
            /*
             * DISTINCT and/or ORDER BY case, with multiple columns sorted on.
             */
            Datum      *values = pertrans->sortslot->tts_values;
            bool       *nulls = pertrans->sortslot->tts_isnull;
            ListCell   *arg;

            strictnulls = nulls;

            foreach(arg, pertrans->aggref->args)
            {
                TargetEntry *source_tle = (TargetEntry *) lfirst(arg);

                ExecInitExprRec(source_tle->expr, state,
                                &values[argno], &nulls[argno]);
                argno++;
            }
        }
        Assert(pertrans->numInputs == argno);

        /*
         * For a strict transfn, nothing happens when there's a NULL input; we
         * just keep the prior transValue. This is true for both plain and
         * sorted/distinct aggregates.
         */
        if (trans_fcinfo->flinfo->fn_strict && pertrans->numTransInputs > 0)
        {
            if (strictnulls)
                scratch.opcode = EEOP_AGG_STRICT_INPUT_CHECK_NULLS;
            else
                scratch.opcode = EEOP_AGG_STRICT_INPUT_CHECK_ARGS;
            scratch.d.agg_strict_input_check.nulls = strictnulls;
            scratch.d.agg_strict_input_check.args = strictargs;
            scratch.d.agg_strict_input_check.jumpnull = -1; /* adjust later */
            scratch.d.agg_strict_input_check.nargs = pertrans->numTransInputs;
            ExprEvalPushStep(state, &scratch);
            adjust_bailout = lappend_int(adjust_bailout,
                                         state->steps_len - 1);
        }

        /*
         * Call transition function (once for each concurrently evaluated
         * grouping set). Do so for both sort and hash based computations, as
         * applicable.
         */
        if (doSort)
        {
            int         processGroupingSets = Max(phase->numsets, 1);
            int         setoff = 0;

            for (int setno = 0; setno < processGroupingSets; setno++)
            {
                ExecBuildAggTransCall(state, aggstate, &scratch, trans_fcinfo,
                                      pertrans, transno, setno, setoff, false,
                                      nullcheck);
                setoff++;
            }
        }

        if (doHash)
        {
            int         numHashes = aggstate->num_hashes;
            int         setoff;

            /* in MIXED mode, there'll be preceding transition values */
            if (aggstate->aggstrategy != AGG_HASHED)
                setoff = aggstate->maxsets;
            else
                setoff = 0;

            for (int setno = 0; setno < numHashes; setno++)
            {
                ExecBuildAggTransCall(state, aggstate, &scratch, trans_fcinfo,
                                      pertrans, transno, setno, setoff, true,
                                      nullcheck);
                setoff++;
            }
        }

        /* adjust early bail out jump target(s) */
        foreach(bail, adjust_bailout)
        {
            ExprEvalStep *as = &state->steps[lfirst_int(bail)];

            if (as->opcode == EEOP_JUMP_IF_NOT_TRUE)
            {
                Assert(as->d.jump.jumpdone == -1);
                as->d.jump.jumpdone = state->steps_len;
            }
            else if (as->opcode == EEOP_AGG_STRICT_INPUT_CHECK_ARGS ||
                     as->opcode == EEOP_AGG_STRICT_INPUT_CHECK_NULLS)
            {
                Assert(as->d.agg_strict_input_check.jumpnull == -1);
                as->d.agg_strict_input_check.jumpnull = state->steps_len;
            }
            else if (as->opcode == EEOP_AGG_STRICT_DESERIALIZE)
            {
                Assert(as->d.agg_deserialize.jumpnull == -1);
                as->d.agg_deserialize.jumpnull = state->steps_len;
            }
            else
                Assert(false);
        }
    }

    scratch.resvalue = NULL;
    scratch.resnull = NULL;
    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return state;
}

/*
 * Build transition/combine function invocation for a single transition
 * value. This is separated from ExecBuildAggTrans() because there are
 * multiple callsites (hash and sort in some grouping set cases).
 */
static void
ExecBuildAggTransCall(ExprState *state, AggState *aggstate,
                      ExprEvalStep *scratch,
                      FunctionCallInfo fcinfo, AggStatePerTrans pertrans,
                      int transno, int setno, int setoff, bool ishash,
                      bool nullcheck)
{
    ExprContext *aggcontext;
    int         adjust_jumpnull = -1;

    if (ishash)
        aggcontext = aggstate->hashcontext;
    else
        aggcontext = aggstate->aggcontexts[setno];

    /* add check for NULL pointer? */
    if (nullcheck)
    {
        scratch->opcode = EEOP_AGG_PLAIN_PERGROUP_NULLCHECK;
        scratch->d.agg_plain_pergroup_nullcheck.setoff = setoff;
        /* adjust later */
        scratch->d.agg_plain_pergroup_nullcheck.jumpnull = -1;
        ExprEvalPushStep(state, scratch);
        adjust_jumpnull = state->steps_len - 1;
    }

    /*
     * Determine appropriate transition implementation.
     *
     * For non-ordered aggregates:
     *
     * If the initial value for the transition state doesn't exist in the
     * pg_aggregate table then we will let the first non-NULL value returned
     * from the outer procNode become the initial value. (This is useful for
     * aggregates like max() and min().) The noTransValue flag signals that we
     * need to do so. If true, generate a
     * EEOP_AGG_INIT_STRICT_PLAIN_TRANS{,_BYVAL} step. This step also needs to
     * do the work described next:
     *
     * If the function is strict, but does have an initial value, choose
     * EEOP_AGG_STRICT_PLAIN_TRANS{,_BYVAL}, which skips the transition
     * function if the transition value has become NULL (because a previous
     * transition function returned NULL). This step also needs to do the work
     * described next:
     *
     * Otherwise we call EEOP_AGG_PLAIN_TRANS{,_BYVAL}, which does not have to
     * perform either of the above checks.
     *
     * Having steps with overlapping responsibilities is not nice, but
     * aggregations are very performance sensitive, making this worthwhile.
     *
     * For ordered aggregates:
     *
     * Only need to choose between the faster path for a single ordered
     * column, and the one between multiple columns. Checking strictness etc
     * is done when finalizing the aggregate. See
     * process_ordered_aggregate_{single, multi} and
     * advance_transition_function.
     */
    if (pertrans->numSortCols == 0)
    {
        if (pertrans->transtypeByVal)
        {
            if (fcinfo->flinfo->fn_strict &&
                pertrans->initValueIsNull)
                scratch->opcode = EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL;
            else if (fcinfo->flinfo->fn_strict)
                scratch->opcode = EEOP_AGG_PLAIN_TRANS_STRICT_BYVAL;
            else
                scratch->opcode = EEOP_AGG_PLAIN_TRANS_BYVAL;
        }
        else
        {
            if (fcinfo->flinfo->fn_strict &&
                pertrans->initValueIsNull)
                scratch->opcode = EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYREF;
            else if (fcinfo->flinfo->fn_strict)
                scratch->opcode = EEOP_AGG_PLAIN_TRANS_STRICT_BYREF;
            else
                scratch->opcode = EEOP_AGG_PLAIN_TRANS_BYREF;
        }
    }
    else if (pertrans->numInputs == 1)
        scratch->opcode = EEOP_AGG_ORDERED_TRANS_DATUM;
    else
        scratch->opcode = EEOP_AGG_ORDERED_TRANS_TUPLE;

    scratch->d.agg_trans.pertrans = pertrans;
    scratch->d.agg_trans.setno = setno;
    scratch->d.agg_trans.setoff = setoff;
    scratch->d.agg_trans.transno = transno;
    scratch->d.agg_trans.aggcontext = aggcontext;
    ExprEvalPushStep(state, scratch);

    /* fix up jumpnull */
    if (adjust_jumpnull != -1)
    {
        ExprEvalStep *as = &state->steps[adjust_jumpnull];

        Assert(as->opcode == EEOP_AGG_PLAIN_PERGROUP_NULLCHECK);
        Assert(as->d.agg_plain_pergroup_nullcheck.jumpnull == -1);
        as->d.agg_plain_pergroup_nullcheck.jumpnull = state->steps_len;
    }
}

/*
 * Build equality expression that can be evaluated using ExecQual(), returning
 * true if the expression context's inner/outer tuple are NOT DISTINCT. I.e
 * two nulls match, a null and a not-null don't match.
 *
 * desc: tuple descriptor of the to-be-compared tuples
 * numCols: the number of attributes to be examined
 * keyColIdx: array of attribute column numbers
 * eqFunctions: array of function oids of the equality functions to use
 * parent: parent executor node
 */
ExprState *
ExecBuildGroupingEqual(TupleDesc ldesc, TupleDesc rdesc,
                       const TupleTableSlotOps *lops, const TupleTableSlotOps *rops,
                       int numCols,
                       const AttrNumber *keyColIdx,
                       const Oid *eqfunctions,
                       const Oid *collations,
                       PlanState *parent)
{
    ExprState  *state = makeNode(ExprState);
    ExprEvalStep scratch = {0};
    int         maxatt = -1;
    List       *adjust_jumps = NIL;
    ListCell   *lc;

    /*
     * When no columns are actually compared, the result's always true. See
     * special case in ExecQual().
     */
    if (numCols == 0)
        return NULL;

    state->expr = NULL;
    state->flags = EEO_FLAG_IS_QUAL;
    state->parent = parent;

    scratch.resvalue = &state->resvalue;
    scratch.resnull = &state->resnull;

    /* compute max needed attribute */
    for (int natt = 0; natt < numCols; natt++)
    {
        int         attno = keyColIdx[natt];

        if (attno > maxatt)
            maxatt = attno;
    }
    Assert(maxatt >= 0);

    /* push deform steps */
    scratch.opcode = EEOP_INNER_FETCHSOME;
    scratch.d.fetch.last_var = maxatt;
    scratch.d.fetch.fixed = false;
    scratch.d.fetch.known_desc = ldesc;
    scratch.d.fetch.kind = lops;
    if (ExecComputeSlotInfo(state, &scratch))
        ExprEvalPushStep(state, &scratch);

    scratch.opcode = EEOP_OUTER_FETCHSOME;
    scratch.d.fetch.last_var = maxatt;
    scratch.d.fetch.fixed = false;
    scratch.d.fetch.known_desc = rdesc;
    scratch.d.fetch.kind = rops;
    if (ExecComputeSlotInfo(state, &scratch))
        ExprEvalPushStep(state, &scratch);

    /*
     * Start comparing at the last field (least significant sort key). That's
     * the most likely to be different if we are dealing with sorted input.
     */
    for (int natt = numCols; --natt >= 0;)
    {
        int         attno = keyColIdx[natt];
        Form_pg_attribute latt = TupleDescAttr(ldesc, attno - 1);
        Form_pg_attribute ratt = TupleDescAttr(rdesc, attno - 1);
        Oid         foid = eqfunctions[natt];
        Oid         collid = collations[natt];
        FmgrInfo   *finfo;
        FunctionCallInfo fcinfo;
        AclResult   aclresult;

        /* Check permission to call function */
        aclresult = pg_proc_aclcheck(foid, GetUserId(), ACL_EXECUTE);
        if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult, OBJECT_FUNCTION, get_func_name(foid));

        InvokeFunctionExecuteHook(foid);

        /* Set up the primary fmgr lookup information */
        finfo = palloc0(sizeof(FmgrInfo));
        fcinfo = palloc0(SizeForFunctionCallInfo(2));
        fmgr_info(foid, finfo);
        fmgr_info_set_expr(NULL, finfo);
        InitFunctionCallInfoData(*fcinfo, finfo, 2,
                                 collid, NULL, NULL);

        /* left arg */
        scratch.opcode = EEOP_INNER_VAR;
        scratch.d.var.attnum = attno - 1;
        scratch.d.var.vartype = latt->atttypid;
        scratch.resvalue = &fcinfo->args[0].value;
        scratch.resnull = &fcinfo->args[0].isnull;
        ExprEvalPushStep(state, &scratch);

        /* right arg */
        scratch.opcode = EEOP_OUTER_VAR;
        scratch.d.var.attnum = attno - 1;
        scratch.d.var.vartype = ratt->atttypid;
        scratch.resvalue = &fcinfo->args[1].value;
        scratch.resnull = &fcinfo->args[1].isnull;
        ExprEvalPushStep(state, &scratch);

        /* evaluate distinctness */
        scratch.opcode = EEOP_NOT_DISTINCT;
        scratch.d.func.finfo = finfo;
        scratch.d.func.fcinfo_data = fcinfo;
        scratch.d.func.fn_addr = finfo->fn_addr;
        scratch.d.func.nargs = 2;
        scratch.resvalue = &state->resvalue;
        scratch.resnull = &state->resnull;
        ExprEvalPushStep(state, &scratch);

        /* then emit EEOP_QUAL to detect if result is false (or null) */
        scratch.opcode = EEOP_QUAL;
        scratch.d.qualexpr.jumpdone = -1;
        scratch.resvalue = &state->resvalue;
        scratch.resnull = &state->resnull;
        ExprEvalPushStep(state, &scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
    }

    /* adjust jump targets */
    foreach(lc, adjust_jumps)
    {
        ExprEvalStep *as = &state->steps[lfirst_int(lc)];

        Assert(as->opcode == EEOP_QUAL);
        Assert(as->d.qualexpr.jumpdone == -1);
        as->d.qualexpr.jumpdone = state->steps_len;
    }

    scratch.resvalue = NULL;
    scratch.resnull = NULL;
    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return state;
}

/*
 * Build equality expression that can be evaluated using ExecQual(), returning
 * true if the expression context's inner/outer tuples are equal.  Datums in
 * the inner/outer slots are assumed to be in the same order and quantity as
 * the 'eqfunctions' parameter.  NULLs are treated as equal.
 *
 * desc: tuple descriptor of the to-be-compared tuples
 * lops: the slot ops for the inner tuple slots
 * rops: the slot ops for the outer tuple slots
 * eqFunctions: array of function oids of the equality functions to use
 * this must be the same length as the 'param_exprs' list.
 * collations: collation Oids to use for equality comparison. Must be the
 * same length as the 'param_exprs' list.
 * parent: parent executor node
 */
ExprState *
ExecBuildParamSetEqual(TupleDesc desc,
                       const TupleTableSlotOps *lops,
                       const TupleTableSlotOps *rops,
                       const Oid *eqfunctions,
                       const Oid *collations,
                       const List *param_exprs,
                       PlanState *parent)
{
    ExprState  *state = makeNode(ExprState);
    ExprEvalStep scratch = {0};
    int         maxatt = list_length(param_exprs);
    List       *adjust_jumps = NIL;
    ListCell   *lc;

    state->expr = NULL;
    state->flags = EEO_FLAG_IS_QUAL;
    state->parent = parent;

    scratch.resvalue = &state->resvalue;
    scratch.resnull = &state->resnull;

    /* push deform steps */
    scratch.opcode = EEOP_INNER_FETCHSOME;
    scratch.d.fetch.last_var = maxatt;
    scratch.d.fetch.fixed = false;
    scratch.d.fetch.known_desc = desc;
    scratch.d.fetch.kind = lops;
    if (ExecComputeSlotInfo(state, &scratch))
        ExprEvalPushStep(state, &scratch);

    scratch.opcode = EEOP_OUTER_FETCHSOME;
    scratch.d.fetch.last_var = maxatt;
    scratch.d.fetch.fixed = false;
    scratch.d.fetch.known_desc = desc;
    scratch.d.fetch.kind = rops;
    if (ExecComputeSlotInfo(state, &scratch))
        ExprEvalPushStep(state, &scratch);

    for (int attno = 0; attno < maxatt; attno++)
    {
        Form_pg_attribute att = TupleDescAttr(desc, attno);
        Oid         foid = eqfunctions[attno];
        Oid         collid = collations[attno];
        FmgrInfo   *finfo;
        FunctionCallInfo fcinfo;
        AclResult   aclresult;

        /* Check permission to call function */
        aclresult = pg_proc_aclcheck(foid, GetUserId(), ACL_EXECUTE);
        if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult, OBJECT_FUNCTION, get_func_name(foid));

        InvokeFunctionExecuteHook(foid);

        /* Set up the primary fmgr lookup information */
        finfo = palloc0(sizeof(FmgrInfo));
        fcinfo = palloc0(SizeForFunctionCallInfo(2));
        fmgr_info(foid, finfo);
        fmgr_info_set_expr(NULL, finfo);
        InitFunctionCallInfoData(*fcinfo, finfo, 2,
                                 collid, NULL, NULL);

        /* left arg */
        scratch.opcode = EEOP_INNER_VAR;
        scratch.d.var.attnum = attno;
        scratch.d.var.vartype = att->atttypid;
        scratch.resvalue = &fcinfo->args[0].value;
        scratch.resnull = &fcinfo->args[0].isnull;
        ExprEvalPushStep(state, &scratch);

        /* right arg */
        scratch.opcode = EEOP_OUTER_VAR;
        scratch.d.var.attnum = attno;
        scratch.d.var.vartype = att->atttypid;
        scratch.resvalue = &fcinfo->args[1].value;
        scratch.resnull = &fcinfo->args[1].isnull;
        ExprEvalPushStep(state, &scratch);

        /* evaluate distinctness */
        scratch.opcode = EEOP_NOT_DISTINCT;
        scratch.d.func.finfo = finfo;
        scratch.d.func.fcinfo_data = fcinfo;
        scratch.d.func.fn_addr = finfo->fn_addr;
        scratch.d.func.nargs = 2;
        scratch.resvalue = &state->resvalue;
        scratch.resnull = &state->resnull;
        ExprEvalPushStep(state, &scratch);

        /* then emit EEOP_QUAL to detect if result is false (or null) */
        scratch.opcode = EEOP_QUAL;
        scratch.d.qualexpr.jumpdone = -1;
        scratch.resvalue = &state->resvalue;
        scratch.resnull = &state->resnull;
        ExprEvalPushStep(state, &scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
    }

    /* adjust jump targets */
    foreach(lc, adjust_jumps)
    {
        ExprEvalStep *as = &state->steps[lfirst_int(lc)];

        Assert(as->opcode == EEOP_QUAL);
        Assert(as->d.qualexpr.jumpdone == -1);
        as->d.qualexpr.jumpdone = state->steps_len;
    }

    scratch.resvalue = NULL;
    scratch.resnull = NULL;
    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return state;
}