parse_agg.c

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/*-------------------------------------------------------------------------
 *
 * parse_agg.c
 *    handle aggregates and window functions in parser
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/parser/parse_agg.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/htup_details.h"
#include "catalog/pg_aggregate.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_type.h"
#include "common/int.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "parser/parse_agg.h"
#include "parser/parse_clause.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteManip.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
 
typedef struct
{
    ParseState *pstate;
    int         min_varlevel;
    int         min_agglevel;
    int         min_ctelevel;
    RangeTblEntry *min_cte;
    int         sublevels_up;
} check_agg_arguments_context;
 
typedef struct
{
    ParseState *pstate;
    Query      *qry;
    bool        hasJoinRTEs;
    List       *groupClauses;   /* list of TargetEntry */
    List       *groupClauseCommonVars;  /* list of Vars */
    List       *groupClauseSubLevels;   /* list of lists of TargetEntry */
    List       *gset_common;    /* integer list of sortgrouprefs */
    bool        have_non_var_grouping;
    List      **func_grouped_rels;
    int         sublevels_up;
    bool        in_agg_direct_args;
} substitute_grouped_columns_context;
 
static int  check_agg_arguments(ParseState *pstate,
                                List *directargs,
                                List *args,
                                Expr *filter,
                                int agglocation);
static bool check_agg_arguments_walker(Node *node,
                                       check_agg_arguments_context *context);
static Node *substitute_grouped_columns(Node *node, ParseState *pstate, Query *qry,
                                        List *groupClauses, List *groupClauseCommonVars,
                                        List *gset_common,
                                        bool have_non_var_grouping,
                                        List **func_grouped_rels);
static Node *substitute_grouped_columns_mutator(Node *node,
                                                substitute_grouped_columns_context *context);
static void finalize_grouping_exprs(Node *node, ParseState *pstate, Query *qry,
                                    List *groupClauses, bool hasJoinRTEs,
                                    bool have_non_var_grouping);
static bool finalize_grouping_exprs_walker(Node *node,
                                           substitute_grouped_columns_context *context);
static Var *buildGroupedVar(int attnum, Index ressortgroupref,
                            substitute_grouped_columns_context *context);
static void check_agglevels_and_constraints(ParseState *pstate, Node *expr);
static List *expand_groupingset_node(GroupingSet *gs);
static Node *make_agg_arg(Oid argtype, Oid argcollation);
 
 
/*
 * transformAggregateCall -
 *      Finish initial transformation of an aggregate call
 *
 * parse_func.c has recognized the function as an aggregate, and has set up
 * all the fields of the Aggref except aggargtypes, aggdirectargs, args,
 * aggorder, aggdistinct and agglevelsup.  The passed-in args list has been
 * through standard expression transformation and type coercion to match the
 * agg's declared arg types, while the passed-in aggorder list hasn't been
 * transformed at all.
 *
 * Here we separate the args list into direct and aggregated args, storing the
 * former in agg->aggdirectargs and the latter in agg->args.  The regular
 * args, but not the direct args, are converted into a targetlist by inserting
 * TargetEntry nodes.  We then transform the aggorder and agg_distinct
 * specifications to produce lists of SortGroupClause nodes for agg->aggorder
 * and agg->aggdistinct.  (For a regular aggregate, this might result in
 * adding resjunk expressions to the targetlist; but for ordered-set
 * aggregates the aggorder list will always be one-to-one with the aggregated
 * args.)
 *
 * We must also determine which query level the aggregate actually belongs to,
 * set agglevelsup accordingly, and mark p_hasAggs true in the corresponding
 * pstate level.
 */
void
transformAggregateCall(ParseState *pstate, Aggref *agg,
                       List *args, List *aggorder, bool agg_distinct)
{
    List       *argtypes = NIL;
    List       *tlist = NIL;
    List       *torder = NIL;
    List       *tdistinct = NIL;
    AttrNumber  attno = 1;
    int         save_next_resno;
    ListCell   *lc;
 
    if (AGGKIND_IS_ORDERED_SET(agg->aggkind))
    {
        /*
         * For an ordered-set agg, the args list includes direct args and
         * aggregated args; we must split them apart.
         */
        int         numDirectArgs = list_length(args) - list_length(aggorder);
        List       *aargs;
        ListCell   *lc2;
 
        Assert(numDirectArgs >= 0);
 
        aargs = list_copy_tail(args, numDirectArgs);
        agg->aggdirectargs = list_truncate(args, numDirectArgs);
 
        /*
         * Build a tlist from the aggregated args, and make a sortlist entry
         * for each one.  Note that the expressions in the SortBy nodes are
         * ignored (they are the raw versions of the transformed args); we are
         * just looking at the sort information in the SortBy nodes.
         */
        forboth(lc, aargs, lc2, aggorder)
        {
            Expr       *arg = (Expr *) lfirst(lc);
            SortBy     *sortby = (SortBy *) lfirst(lc2);
            TargetEntry *tle;
 
            /* We don't bother to assign column names to the entries */
            tle = makeTargetEntry(arg, attno++, NULL, false);
            tlist = lappend(tlist, tle);
 
            torder = addTargetToSortList(pstate, tle,
                                         torder, tlist, sortby);
        }
 
        /* Never any DISTINCT in an ordered-set agg */
        Assert(!agg_distinct);
    }
    else
    {
        /* Regular aggregate, so it has no direct args */
        agg->aggdirectargs = NIL;
 
        /*
         * Transform the plain list of Exprs into a targetlist.
         */
        foreach(lc, args)
        {
            Expr       *arg = (Expr *) lfirst(lc);
            TargetEntry *tle;
 
            /* We don't bother to assign column names to the entries */
            tle = makeTargetEntry(arg, attno++, NULL, false);
            tlist = lappend(tlist, tle);
        }
 
        /*
         * If we have an ORDER BY, transform it.  This will add columns to the
         * tlist if they appear in ORDER BY but weren't already in the arg
         * list.  They will be marked resjunk = true so we can tell them apart
         * from regular aggregate arguments later.
         *
         * We need to mess with p_next_resno since it will be used to number
         * any new targetlist entries.
         */
        save_next_resno = pstate->p_next_resno;
        pstate->p_next_resno = attno;
 
        torder = transformSortClause(pstate,
                                     aggorder,
                                     &tlist,
                                     EXPR_KIND_ORDER_BY,
                                     true /* force SQL99 rules */ );
 
        /*
         * If we have DISTINCT, transform that to produce a distinctList.
         */
        if (agg_distinct)
        {
            tdistinct = transformDistinctClause(pstate, &tlist, torder, true);
 
            /*
             * Remove this check if executor support for hashed distinct for
             * aggregates is ever added.
             */
            foreach(lc, tdistinct)
            {
                SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc);
 
                if (!OidIsValid(sortcl->sortop))
                {
                    Node       *expr = get_sortgroupclause_expr(sortcl, tlist);
 
                    ereport(ERROR,
                            (errcode(ERRCODE_UNDEFINED_FUNCTION),
                             errmsg("could not identify an ordering operator for type %s",
                                    format_type_be(exprType(expr))),
                             errdetail("Aggregates with DISTINCT must be able to sort their inputs."),
                             parser_errposition(pstate, exprLocation(expr))));
                }
            }
        }
 
        pstate->p_next_resno = save_next_resno;
    }
 
    /* Update the Aggref with the transformation results */
    agg->args = tlist;
    agg->aggorder = torder;
    agg->aggdistinct = tdistinct;
 
    /*
     * Now build the aggargtypes list with the type OIDs of the direct and
     * aggregated args, ignoring any resjunk entries that might have been
     * added by ORDER BY/DISTINCT processing.  We can't do this earlier
     * because said processing can modify some args' data types, in particular
     * by resolving previously-unresolved "unknown" literals.
     */
    foreach(lc, agg->aggdirectargs)
    {
        Expr       *arg = (Expr *) lfirst(lc);
 
        argtypes = lappend_oid(argtypes, exprType((Node *) arg));
    }
    foreach(lc, tlist)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(lc);
 
        if (tle->resjunk)
            continue;           /* ignore junk */
        argtypes = lappend_oid(argtypes, exprType((Node *) tle->expr));
    }
    agg->aggargtypes = argtypes;
 
    check_agglevels_and_constraints(pstate, (Node *) agg);
}
 
/*
 * transformGroupingFunc
 *      Transform a GROUPING expression
 *
 * GROUPING() behaves very like an aggregate.  Processing of levels and nesting
 * is done as for aggregates.  We set p_hasAggs for these expressions too.
 */
Node *
transformGroupingFunc(ParseState *pstate, GroupingFunc *p)
{
    ListCell   *lc;
    List       *args = p->args;
    List       *result_list = NIL;
    GroupingFunc *result = makeNode(GroupingFunc);
 
    if (list_length(args) > 31)
        ereport(ERROR,
                (errcode(ERRCODE_TOO_MANY_ARGUMENTS),
                 errmsg("GROUPING must have fewer than 32 arguments"),
                 parser_errposition(pstate, p->location)));
 
    foreach(lc, args)
    {
        Node       *current_result;
 
        current_result = transformExpr(pstate, (Node *) lfirst(lc), pstate->p_expr_kind);
 
        /* acceptability of expressions is checked later */
 
        result_list = lappend(result_list, current_result);
    }
 
    result->args = result_list;
    result->location = p->location;
 
    check_agglevels_and_constraints(pstate, (Node *) result);
 
    return (Node *) result;
}
 
/*
 * Aggregate functions and grouping operations (which are combined in the spec
 * as <set function specification>) are very similar with regard to level and
 * nesting restrictions (though we allow a lot more things than the spec does).
 * Centralise those restrictions here.
 */
static void
check_agglevels_and_constraints(ParseState *pstate, Node *expr)
{
    List       *directargs = NIL;
    List       *args = NIL;
    Expr       *filter = NULL;
    int         min_varlevel;
    int         location = -1;
    Index      *p_levelsup;
    const char *err;
    bool        errkind;
    bool        isAgg = IsA(expr, Aggref);
 
    if (isAgg)
    {
        Aggref     *agg = (Aggref *) expr;
 
        directargs = agg->aggdirectargs;
        args = agg->args;
        filter = agg->aggfilter;
        location = agg->location;
        p_levelsup = &agg->agglevelsup;
    }
    else
    {
        GroupingFunc *grp = (GroupingFunc *) expr;
 
        args = grp->args;
        location = grp->location;
        p_levelsup = &grp->agglevelsup;
    }
 
    /*
     * Check the arguments to compute the aggregate's level and detect
     * improper nesting.
     */
    min_varlevel = check_agg_arguments(pstate,
                                       directargs,
                                       args,
                                       filter,
                                       location);
 
    *p_levelsup = min_varlevel;
 
    /* Mark the correct pstate level as having aggregates */
    while (min_varlevel-- > 0)
        pstate = pstate->parentParseState;
    pstate->p_hasAggs = true;
 
    /*
     * Check to see if the aggregate function is in an invalid place within
     * its aggregation query.
     *
     * For brevity we support two schemes for reporting an error here: set
     * "err" to a custom message, or set "errkind" true if the error context
     * is sufficiently identified by what ParseExprKindName will return, *and*
     * what it will return is just a SQL keyword.  (Otherwise, use a custom
     * message to avoid creating translation problems.)
     */
    err = NULL;
    errkind = false;
    switch (pstate->p_expr_kind)
    {
        case EXPR_KIND_NONE:
            Assert(false);      /* can't happen */
            break;
        case EXPR_KIND_OTHER:
 
            /*
             * Accept aggregate/grouping here; caller must throw error if
             * wanted
             */
            break;
        case EXPR_KIND_JOIN_ON:
        case EXPR_KIND_JOIN_USING:
            if (isAgg)
                err = _("aggregate functions are not allowed in JOIN conditions");
            else
                err = _("grouping operations are not allowed in JOIN conditions");
 
            break;
        case EXPR_KIND_FROM_SUBSELECT:
 
            /*
             * Aggregate/grouping scope rules make it worth being explicit
             * here
             */
            if (isAgg)
                err = _("aggregate functions are not allowed in FROM clause of their own query level");
            else
                err = _("grouping operations are not allowed in FROM clause of their own query level");
 
            break;
        case EXPR_KIND_FROM_FUNCTION:
            if (isAgg)
                err = _("aggregate functions are not allowed in functions in FROM");
            else
                err = _("grouping operations are not allowed in functions in FROM");
 
            break;
        case EXPR_KIND_WHERE:
            errkind = true;
            break;
        case EXPR_KIND_POLICY:
            if (isAgg)
                err = _("aggregate functions are not allowed in policy expressions");
            else
                err = _("grouping operations are not allowed in policy expressions");
 
            break;
        case EXPR_KIND_HAVING:
            /* okay */
            break;
        case EXPR_KIND_FILTER:
            errkind = true;
            break;
        case EXPR_KIND_WINDOW_PARTITION:
            /* okay */
            break;
        case EXPR_KIND_WINDOW_ORDER:
            /* okay */
            break;
        case EXPR_KIND_WINDOW_FRAME_RANGE:
            if (isAgg)
                err = _("aggregate functions are not allowed in window RANGE");
            else
                err = _("grouping operations are not allowed in window RANGE");
 
            break;
        case EXPR_KIND_WINDOW_FRAME_ROWS:
            if (isAgg)
                err = _("aggregate functions are not allowed in window ROWS");
            else
                err = _("grouping operations are not allowed in window ROWS");
 
            break;
        case EXPR_KIND_WINDOW_FRAME_GROUPS:
            if (isAgg)
                err = _("aggregate functions are not allowed in window GROUPS");
            else
                err = _("grouping operations are not allowed in window GROUPS");
 
            break;
        case EXPR_KIND_SELECT_TARGET:
            /* okay */
            break;
        case EXPR_KIND_INSERT_TARGET:
        case EXPR_KIND_UPDATE_SOURCE:
        case EXPR_KIND_UPDATE_TARGET:
            errkind = true;
            break;
        case EXPR_KIND_MERGE_WHEN:
            if (isAgg)
                err = _("aggregate functions are not allowed in MERGE WHEN conditions");
            else
                err = _("grouping operations are not allowed in MERGE WHEN conditions");
 
            break;
        case EXPR_KIND_GROUP_BY:
            errkind = true;
            break;
        case EXPR_KIND_ORDER_BY:
            /* okay */
            break;
        case EXPR_KIND_DISTINCT_ON:
            /* okay */
            break;
        case EXPR_KIND_LIMIT:
        case EXPR_KIND_OFFSET:
            errkind = true;
            break;
        case EXPR_KIND_RETURNING:
        case EXPR_KIND_MERGE_RETURNING:
            errkind = true;
            break;
        case EXPR_KIND_VALUES:
        case EXPR_KIND_VALUES_SINGLE:
            errkind = true;
            break;
        case EXPR_KIND_CHECK_CONSTRAINT:
        case EXPR_KIND_DOMAIN_CHECK:
            if (isAgg)
                err = _("aggregate functions are not allowed in check constraints");
            else
                err = _("grouping operations are not allowed in check constraints");
 
            break;
        case EXPR_KIND_COLUMN_DEFAULT:
        case EXPR_KIND_FUNCTION_DEFAULT:
 
            if (isAgg)
                err = _("aggregate functions are not allowed in DEFAULT expressions");
            else
                err = _("grouping operations are not allowed in DEFAULT expressions");
 
            break;
        case EXPR_KIND_INDEX_EXPRESSION:
            if (isAgg)
                err = _("aggregate functions are not allowed in index expressions");
            else
                err = _("grouping operations are not allowed in index expressions");
 
            break;
        case EXPR_KIND_INDEX_PREDICATE:
            if (isAgg)
                err = _("aggregate functions are not allowed in index predicates");
            else
                err = _("grouping operations are not allowed in index predicates");
 
            break;
        case EXPR_KIND_STATS_EXPRESSION:
            if (isAgg)
                err = _("aggregate functions are not allowed in statistics expressions");
            else
                err = _("grouping operations are not allowed in statistics expressions");
 
            break;
        case EXPR_KIND_ALTER_COL_TRANSFORM:
            if (isAgg)
                err = _("aggregate functions are not allowed in transform expressions");
            else
                err = _("grouping operations are not allowed in transform expressions");
 
            break;
        case EXPR_KIND_EXECUTE_PARAMETER:
            if (isAgg)
                err = _("aggregate functions are not allowed in EXECUTE parameters");
            else
                err = _("grouping operations are not allowed in EXECUTE parameters");
 
            break;
        case EXPR_KIND_TRIGGER_WHEN:
            if (isAgg)
                err = _("aggregate functions are not allowed in trigger WHEN conditions");
            else
                err = _("grouping operations are not allowed in trigger WHEN conditions");
 
            break;
        case EXPR_KIND_PARTITION_BOUND:
            if (isAgg)
                err = _("aggregate functions are not allowed in partition bound");
            else
                err = _("grouping operations are not allowed in partition bound");
 
            break;
        case EXPR_KIND_PARTITION_EXPRESSION:
            if (isAgg)
                err = _("aggregate functions are not allowed in partition key expressions");
            else
                err = _("grouping operations are not allowed in partition key expressions");
 
            break;
        case EXPR_KIND_GENERATED_COLUMN:
 
            if (isAgg)
                err = _("aggregate functions are not allowed in column generation expressions");
            else
                err = _("grouping operations are not allowed in column generation expressions");
 
            break;
 
        case EXPR_KIND_CALL_ARGUMENT:
            if (isAgg)
                err = _("aggregate functions are not allowed in CALL arguments");
            else
                err = _("grouping operations are not allowed in CALL arguments");
 
            break;
 
        case EXPR_KIND_COPY_WHERE:
            if (isAgg)
                err = _("aggregate functions are not allowed in COPY FROM WHERE conditions");
            else
                err = _("grouping operations are not allowed in COPY FROM WHERE conditions");
 
            break;
 
        case EXPR_KIND_CYCLE_MARK:
            errkind = true;
            break;
 
        case EXPR_KIND_PROPGRAPH_PROPERTY:
            if (isAgg)
                err = _("aggregate functions are not allowed in property definition expressions");
            else
                err = _("grouping operations are not allowed in property definition expressions");
 
            break;
 
            /*
             * There is intentionally no default: case here, so that the
             * compiler will warn if we add a new ParseExprKind without
             * extending this switch.  If we do see an unrecognized value at
             * runtime, the behavior will be the same as for EXPR_KIND_OTHER,
             * which is sane anyway.
             */
    }
 
    if (err)
        ereport(ERROR,
                (errcode(ERRCODE_GROUPING_ERROR),
                 errmsg_internal("%s", err),
                 parser_errposition(pstate, location)));
 
    if (errkind)
    {
        if (isAgg)
            /* translator: %s is name of a SQL construct, eg GROUP BY */
            err = _("aggregate functions are not allowed in %s");
        else
            /* translator: %s is name of a SQL construct, eg GROUP BY */
            err = _("grouping operations are not allowed in %s");
 
        ereport(ERROR,
                (errcode(ERRCODE_GROUPING_ERROR),
                 errmsg_internal(err,
                                 ParseExprKindName(pstate->p_expr_kind)),
                 parser_errposition(pstate, location)));
    }
}
 
/*
 * check_agg_arguments
 *    Scan the arguments of an aggregate function to determine the
 *    aggregate's semantic level (zero is the current select's level,
 *    one is its parent, etc).
 *
 * The aggregate's level is the same as the level of the lowest-level variable
 * or aggregate in its aggregated arguments (including any ORDER BY columns)
 * or filter expression; or if it contains no variables at all, we presume it
 * to be local.
 *
 * Vars/Aggs in direct arguments are *not* counted towards determining the
 * agg's level, as those arguments aren't evaluated per-row but only
 * per-group, and so in some sense aren't really agg arguments.  However,
 * this can mean that we decide an agg is upper-level even when its direct
 * args contain lower-level Vars/Aggs, and that case has to be disallowed.
 * (This is a little strange, but the SQL standard seems pretty definite that
 * direct args are not to be considered when setting the agg's level.)
 *
 * We also take this opportunity to detect any aggregates or window functions
 * nested within the arguments.  We can throw error immediately if we find
 * a window function.  Aggregates are a bit trickier because it's only an
 * error if the inner aggregate is of the same semantic level as the outer,
 * which we can't know until we finish scanning the arguments.
 */
static int
check_agg_arguments(ParseState *pstate,
                    List *directargs,
                    List *args,
                    Expr *filter,
                    int agglocation)
{
    int         agglevel;
    check_agg_arguments_context context;
 
    context.pstate = pstate;
    context.min_varlevel = -1;  /* signifies nothing found yet */
    context.min_agglevel = -1;
    context.min_ctelevel = -1;
    context.min_cte = NULL;
    context.sublevels_up = 0;
 
    (void) check_agg_arguments_walker((Node *) args, &context);
    (void) check_agg_arguments_walker((Node *) filter, &context);
 
    /*
     * If we found no vars nor aggs at all, it's a level-zero aggregate;
     * otherwise, its level is the minimum of vars or aggs.
     */
    if (context.min_varlevel < 0)
    {
        if (context.min_agglevel < 0)
            agglevel = 0;
        else
            agglevel = context.min_agglevel;
    }
    else if (context.min_agglevel < 0)
        agglevel = context.min_varlevel;
    else
        agglevel = Min(context.min_varlevel, context.min_agglevel);
 
    /*
     * If there's a nested aggregate of the same semantic level, complain.
     */
    if (agglevel == context.min_agglevel)
    {
        int         aggloc;
 
        aggloc = locate_agg_of_level((Node *) args, agglevel);
        if (aggloc < 0)
            aggloc = locate_agg_of_level((Node *) filter, agglevel);
        ereport(ERROR,
                (errcode(ERRCODE_GROUPING_ERROR),
                 errmsg("aggregate function calls cannot be nested"),
                 parser_errposition(pstate, aggloc)));
    }
 
    /*
     * If there's a non-local CTE that's below the aggregate's semantic level,
     * complain.  It's not quite clear what we should do to fix up such a case
     * (treating the CTE reference like a Var seems wrong), and it's also
     * unclear whether there is a real-world use for such cases.
     */
    if (context.min_ctelevel >= 0 && context.min_ctelevel < agglevel)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("outer-level aggregate cannot use a nested CTE"),
                 errdetail("CTE \"%s\" is below the aggregate's semantic level.",
                           context.min_cte->eref->aliasname),
                 parser_errposition(pstate, agglocation)));
 
    /*
     * Now check for vars/aggs in the direct arguments, and throw error if
     * needed.  Note that we allow a Var of the agg's semantic level, but not
     * an Agg of that level.  In principle such Aggs could probably be
     * supported, but it would create an ordering dependency among the
     * aggregates at execution time.  Since the case appears neither to be
     * required by spec nor particularly useful, we just treat it as a
     * nested-aggregate situation.
     */
    if (directargs)
    {
        context.min_varlevel = -1;
        context.min_agglevel = -1;
        context.min_ctelevel = -1;
        (void) check_agg_arguments_walker((Node *) directargs, &context);
        if (context.min_varlevel >= 0 && context.min_varlevel < agglevel)
            ereport(ERROR,
                    (errcode(ERRCODE_GROUPING_ERROR),
                     errmsg("outer-level aggregate cannot contain a lower-level variable in its direct arguments"),
                     parser_errposition(pstate,
                                        locate_var_of_level((Node *) directargs,
                                                            context.min_varlevel))));
        if (context.min_agglevel >= 0 && context.min_agglevel <= agglevel)
            ereport(ERROR,
                    (errcode(ERRCODE_GROUPING_ERROR),
                     errmsg("aggregate function calls cannot be nested"),
                     parser_errposition(pstate,
                                        locate_agg_of_level((Node *) directargs,
                                                            context.min_agglevel))));
        if (context.min_ctelevel >= 0 && context.min_ctelevel < agglevel)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("outer-level aggregate cannot use a nested CTE"),
                     errdetail("CTE \"%s\" is below the aggregate's semantic level.",
                               context.min_cte->eref->aliasname),
                     parser_errposition(pstate, agglocation)));
    }
    return agglevel;
}
 
static bool
check_agg_arguments_walker(Node *node,
                           check_agg_arguments_context *context)
{
    if (node == NULL)
        return false;
    if (IsA(node, Var))
    {
        int         varlevelsup = ((Var *) node)->varlevelsup;
 
        /* convert levelsup to frame of reference of original query */
        varlevelsup -= context->sublevels_up;
        /* ignore local vars of subqueries */
        if (varlevelsup >= 0)
        {
            if (context->min_varlevel < 0 ||
                context->min_varlevel > varlevelsup)
                context->min_varlevel = varlevelsup;
        }
        return false;
    }
    if (IsA(node, Aggref))
    {
        int         agglevelsup = ((Aggref *) node)->agglevelsup;
 
        /* convert levelsup to frame of reference of original query */
        agglevelsup -= context->sublevels_up;
        /* ignore local aggs of subqueries */
        if (agglevelsup >= 0)
        {
            if (context->min_agglevel < 0 ||
                context->min_agglevel > agglevelsup)
                context->min_agglevel = agglevelsup;
        }
        /* Continue and descend into subtree */
    }
    if (IsA(node, GroupingFunc))
    {
        int         agglevelsup = ((GroupingFunc *) node)->agglevelsup;
 
        /* convert levelsup to frame of reference of original query */
        agglevelsup -= context->sublevels_up;
        /* ignore local aggs of subqueries */
        if (agglevelsup >= 0)
        {
            if (context->min_agglevel < 0 ||
                context->min_agglevel > agglevelsup)
                context->min_agglevel = agglevelsup;
        }
        /* Continue and descend into subtree */
    }
 
    /*
     * SRFs and window functions can be rejected immediately, unless we are
     * within a sub-select within the aggregate's arguments; in that case
     * they're OK.
     */
    if (context->sublevels_up == 0)
    {
        if ((IsA(node, FuncExpr) && ((FuncExpr *) node)->funcretset) ||
            (IsA(node, OpExpr) && ((OpExpr *) node)->opretset))
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("aggregate function calls cannot contain set-returning function calls"),
                     errhint("You might be able to move the set-returning function into a LATERAL FROM item."),
                     parser_errposition(context->pstate, exprLocation(node))));
        if (IsA(node, WindowFunc))
            ereport(ERROR,
                    (errcode(ERRCODE_GROUPING_ERROR),
                     errmsg("aggregate function calls cannot contain window function calls"),
                     parser_errposition(context->pstate,
                                        ((WindowFunc *) node)->location)));
    }
 
    if (IsA(node, RangeTblEntry))
    {
        RangeTblEntry *rte = (RangeTblEntry *) node;
 
        if (rte->rtekind == RTE_CTE)
        {
            int         ctelevelsup = rte->ctelevelsup;
 
            /* convert levelsup to frame of reference of original query */
            ctelevelsup -= context->sublevels_up;
            /* ignore local CTEs of subqueries */
            if (ctelevelsup >= 0)
            {
                if (context->min_ctelevel < 0 ||
                    context->min_ctelevel > ctelevelsup)
                {
                    context->min_ctelevel = ctelevelsup;
                    context->min_cte = rte;
                }
            }
        }
        return false;           /* allow range_table_walker to continue */
    }
    if (IsA(node, Query))
    {
        /* Recurse into subselects */
        bool        result;
 
        context->sublevels_up++;
        result = query_tree_walker((Query *) node,
                                   check_agg_arguments_walker,
                                   context,
                                   QTW_EXAMINE_RTES_BEFORE);
        context->sublevels_up--;
        return result;
    }
 
    return expression_tree_walker(node,
                                  check_agg_arguments_walker,
                                  context);
}
 
/*
 * transformWindowFuncCall -
 *      Finish initial transformation of a window function call
 *
 * parse_func.c has recognized the function as a window function, and has set
 * up all the fields of the WindowFunc except winref.  Here we must (1) add
 * the WindowDef to the pstate (if not a duplicate of one already present) and
 * set winref to link to it; and (2) mark p_hasWindowFuncs true in the pstate.
 * Unlike aggregates, only the most closely nested pstate level need be
 * considered --- there are no "outer window functions" per SQL spec.
 */
void
transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
                        WindowDef *windef)
{
    const char *err;
    bool        errkind;
 
    /*
     * A window function call can't contain another one (but aggs are OK). XXX
     * is this required by spec, or just an unimplemented feature?
     *
     * Note: we don't need to check the filter expression here, because the
     * context checks done below and in transformAggregateCall would have
     * already rejected any window funcs or aggs within the filter.
     */
    if (pstate->p_hasWindowFuncs &&
        contain_windowfuncs((Node *) wfunc->args))
        ereport(ERROR,
                (errcode(ERRCODE_WINDOWING_ERROR),
                 errmsg("window function calls cannot be nested"),
                 parser_errposition(pstate,
                                    locate_windowfunc((Node *) wfunc->args))));
 
    /*
     * Check to see if the window function is in an invalid place within the
     * query.
     *
     * For brevity we support two schemes for reporting an error here: set
     * "err" to a custom message, or set "errkind" true if the error context
     * is sufficiently identified by what ParseExprKindName will return, *and*
     * what it will return is just a SQL keyword.  (Otherwise, use a custom
     * message to avoid creating translation problems.)
     */
    err = NULL;
    errkind = false;
    switch (pstate->p_expr_kind)
    {
        case EXPR_KIND_NONE:
            Assert(false);      /* can't happen */
            break;
        case EXPR_KIND_OTHER:
            /* Accept window func here; caller must throw error if wanted */
            break;
        case EXPR_KIND_JOIN_ON:
        case EXPR_KIND_JOIN_USING:
            err = _("window functions are not allowed in JOIN conditions");
            break;
        case EXPR_KIND_FROM_SUBSELECT:
            /* can't get here, but just in case, throw an error */
            errkind = true;
            break;
        case EXPR_KIND_FROM_FUNCTION:
            err = _("window functions are not allowed in functions in FROM");
            break;
        case EXPR_KIND_WHERE:
            errkind = true;
            break;
        case EXPR_KIND_POLICY:
            err = _("window functions are not allowed in policy expressions");
            break;
        case EXPR_KIND_HAVING:
            errkind = true;
            break;
        case EXPR_KIND_FILTER:
            errkind = true;
            break;
        case EXPR_KIND_WINDOW_PARTITION:
        case EXPR_KIND_WINDOW_ORDER:
        case EXPR_KIND_WINDOW_FRAME_RANGE:
        case EXPR_KIND_WINDOW_FRAME_ROWS:
        case EXPR_KIND_WINDOW_FRAME_GROUPS:
            err = _("window functions are not allowed in window definitions");
            break;
        case EXPR_KIND_SELECT_TARGET:
            /* okay */
            break;
        case EXPR_KIND_INSERT_TARGET:
        case EXPR_KIND_UPDATE_SOURCE:
        case EXPR_KIND_UPDATE_TARGET:
            errkind = true;
            break;
        case EXPR_KIND_MERGE_WHEN:
            err = _("window functions are not allowed in MERGE WHEN conditions");
            break;
        case EXPR_KIND_GROUP_BY:
            errkind = true;
            break;
        case EXPR_KIND_ORDER_BY:
            /* okay */
            break;
        case EXPR_KIND_DISTINCT_ON:
            /* okay */
            break;
        case EXPR_KIND_LIMIT:
        case EXPR_KIND_OFFSET:
            errkind = true;
            break;
        case EXPR_KIND_RETURNING:
        case EXPR_KIND_MERGE_RETURNING:
            errkind = true;
            break;
        case EXPR_KIND_VALUES:
        case EXPR_KIND_VALUES_SINGLE:
            errkind = true;
            break;
        case EXPR_KIND_CHECK_CONSTRAINT:
        case EXPR_KIND_DOMAIN_CHECK:
            err = _("window functions are not allowed in check constraints");
            break;
        case EXPR_KIND_COLUMN_DEFAULT:
        case EXPR_KIND_FUNCTION_DEFAULT:
            err = _("window functions are not allowed in DEFAULT expressions");
            break;
        case EXPR_KIND_INDEX_EXPRESSION:
            err = _("window functions are not allowed in index expressions");
            break;
        case EXPR_KIND_STATS_EXPRESSION:
            err = _("window functions are not allowed in statistics expressions");
            break;
        case EXPR_KIND_INDEX_PREDICATE:
            err = _("window functions are not allowed in index predicates");
            break;
        case EXPR_KIND_ALTER_COL_TRANSFORM:
            err = _("window functions are not allowed in transform expressions");
            break;
        case EXPR_KIND_EXECUTE_PARAMETER:
            err = _("window functions are not allowed in EXECUTE parameters");
            break;
        case EXPR_KIND_TRIGGER_WHEN:
            err = _("window functions are not allowed in trigger WHEN conditions");
            break;
        case EXPR_KIND_PARTITION_BOUND:
            err = _("window functions are not allowed in partition bound");
            break;
        case EXPR_KIND_PARTITION_EXPRESSION:
            err = _("window functions are not allowed in partition key expressions");
            break;
        case EXPR_KIND_CALL_ARGUMENT:
            err = _("window functions are not allowed in CALL arguments");
            break;
        case EXPR_KIND_COPY_WHERE:
            err = _("window functions are not allowed in COPY FROM WHERE conditions");
            break;
        case EXPR_KIND_GENERATED_COLUMN:
            err = _("window functions are not allowed in column generation expressions");
            break;
        case EXPR_KIND_CYCLE_MARK:
            errkind = true;
            break;
        case EXPR_KIND_PROPGRAPH_PROPERTY:
            err = _("window functions are not allowed in property definition expressions");
            break;
 
            /*
             * There is intentionally no default: case here, so that the
             * compiler will warn if we add a new ParseExprKind without
             * extending this switch.  If we do see an unrecognized value at
             * runtime, the behavior will be the same as for EXPR_KIND_OTHER,
             * which is sane anyway.
             */
    }
    if (err)
        ereport(ERROR,
                (errcode(ERRCODE_WINDOWING_ERROR),
                 errmsg_internal("%s", err),
                 parser_errposition(pstate, wfunc->location)));
    if (errkind)
        ereport(ERROR,
                (errcode(ERRCODE_WINDOWING_ERROR),
        /* translator: %s is name of a SQL construct, eg GROUP BY */
                 errmsg("window functions are not allowed in %s",
                        ParseExprKindName(pstate->p_expr_kind)),
                 parser_errposition(pstate, wfunc->location)));
 
    /*
     * If the OVER clause just specifies a window name, find that WINDOW
     * clause (which had better be present).  Otherwise, try to match all the
     * properties of the OVER clause, and make a new entry in the p_windowdefs
     * list if no luck.
     */
    if (windef->name)
    {
        Index       winref = 0;
        ListCell   *lc;
 
        Assert(windef->refname == NULL &&
               windef->partitionClause == NIL &&
               windef->orderClause == NIL &&
               windef->frameOptions == FRAMEOPTION_DEFAULTS);
 
        foreach(lc, pstate->p_windowdefs)
        {
            WindowDef  *refwin = (WindowDef *) lfirst(lc);
 
            winref++;
            if (refwin->name && strcmp(refwin->name, windef->name) == 0)
            {
                wfunc->winref = winref;
                break;
            }
        }
        if (lc == NULL)         /* didn't find it? */
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("window \"%s\" does not exist", windef->name),
                     parser_errposition(pstate, windef->location)));
    }
    else
    {
        Index       winref = 0;
        ListCell   *lc;
 
        foreach(lc, pstate->p_windowdefs)
        {
            WindowDef  *refwin = (WindowDef *) lfirst(lc);
 
            winref++;
            if (refwin->refname && windef->refname &&
                strcmp(refwin->refname, windef->refname) == 0)
                 /* matched on refname */ ;
            else if (!refwin->refname && !windef->refname)
                 /* matched, no refname */ ;
            else
                continue;
 
            /*
             * Also see similar de-duplication code in optimize_window_clauses
             */
            if (equal(refwin->partitionClause, windef->partitionClause) &&
                equal(refwin->orderClause, windef->orderClause) &&
                refwin->frameOptions == windef->frameOptions &&
                equal(refwin->startOffset, windef->startOffset) &&
                equal(refwin->endOffset, windef->endOffset))
            {
                /* found a duplicate window specification */
                wfunc->winref = winref;
                break;
            }
        }
        if (lc == NULL)         /* didn't find it? */
        {
            pstate->p_windowdefs = lappend(pstate->p_windowdefs, windef);
            wfunc->winref = list_length(pstate->p_windowdefs);
        }
    }
 
    pstate->p_hasWindowFuncs = true;
}
 
/*
 * parseCheckAggregates
 *  Check for aggregates where they shouldn't be and improper grouping, and
 *  replace grouped variables in the targetlist and HAVING clause with Vars
 *  that reference the RTE_GROUP RTE.
 *  This function should be called after the target list and qualifications
 *  are finalized.
 *
 *  Misplaced aggregates are now mostly detected in transformAggregateCall,
 *  but it seems more robust to check for aggregates in recursive queries
 *  only after everything is finalized.  In any case it's hard to detect
 *  improper grouping on-the-fly, so we have to make another pass over the
 *  query for that.
 */
void
parseCheckAggregates(ParseState *pstate, Query *qry)
{
    List       *gset_common = NIL;
    List       *groupClauses = NIL;
    List       *groupClauseCommonVars = NIL;
    bool        have_non_var_grouping;
    List       *func_grouped_rels = NIL;
    ListCell   *l;
    bool        hasJoinRTEs;
    bool        hasSelfRefRTEs;
    Node       *clause;
 
    /* This should only be called if we found aggregates or grouping */
    Assert(pstate->p_hasAggs || qry->groupClause || qry->havingQual || qry->groupingSets);
 
    /*
     * If we have grouping sets, expand them and find the intersection of all
     * sets.
     */
    if (qry->groupingSets)
    {
        /*
         * The limit of 4096 is arbitrary and exists simply to avoid resource
         * issues from pathological constructs.
         */
        List       *gsets = expand_grouping_sets(qry->groupingSets, qry->groupDistinct, 4096);
 
        if (!gsets)
            ereport(ERROR,
                    (errcode(ERRCODE_STATEMENT_TOO_COMPLEX),
                     errmsg("too many grouping sets present (maximum 4096)"),
                     parser_errposition(pstate,
                                        qry->groupClause
                                        ? exprLocation((Node *) qry->groupClause)
                                        : exprLocation((Node *) qry->groupingSets))));
 
        /*
         * The intersection will often be empty, so help things along by
         * seeding the intersect with the smallest set.
         */
        gset_common = linitial(gsets);
 
        if (gset_common)
        {
            for_each_from(l, gsets, 1)
            {
                gset_common = list_intersection_int(gset_common, lfirst(l));
                if (!gset_common)
                    break;
            }
        }
 
        /*
         * If there was only one grouping set in the expansion, AND if the
         * groupClause is non-empty (meaning that the grouping set is not
         * empty either), then we can ditch the grouping set and pretend we
         * just had a normal GROUP BY.
         */
        if (list_length(gsets) == 1 && qry->groupClause)
            qry->groupingSets = NIL;
    }
 
    /*
     * Scan the range table to see if there are JOIN or self-reference CTE
     * entries.  We'll need this info below.
     */
    hasJoinRTEs = hasSelfRefRTEs = false;
    foreach(l, pstate->p_rtable)
    {
        RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 
        if (rte->rtekind == RTE_JOIN)
            hasJoinRTEs = true;
        else if (rte->rtekind == RTE_CTE && rte->self_reference)
            hasSelfRefRTEs = true;
    }
 
    /*
     * Build a list of the acceptable GROUP BY expressions to save in the
     * RTE_GROUP RTE, and for use by substitute_grouped_columns().
     *
     * We get the TLE, not just the expr, because GROUPING wants to know the
     * sortgroupref.
     */
    foreach(l, qry->groupClause)
    {
        SortGroupClause *grpcl = (SortGroupClause *) lfirst(l);
        TargetEntry *expr;
 
        expr = get_sortgroupclause_tle(grpcl, qry->targetList);
        if (expr == NULL)
            continue;           /* probably cannot happen */
 
        groupClauses = lappend(groupClauses, expr);
    }
 
    /*
     * If there are any acceptable GROUP BY expressions, build an RTE and
     * nsitem for the result of the grouping step.  (It's important to do this
     * before flattening join alias vars in groupClauses, because the RTE
     * should preserve any alias vars that were in the input.)
     */
    if (groupClauses)
    {
        pstate->p_grouping_nsitem =
            addRangeTableEntryForGroup(pstate, groupClauses);
 
        /* Set qry->rtable again in case it was previously NIL */
        qry->rtable = pstate->p_rtable;
        /* Mark the Query as having RTE_GROUP RTE */
        qry->hasGroupRTE = true;
    }
 
    /*
     * If there are join alias vars involved, we have to flatten them to the
     * underlying vars, so that aliased and unaliased vars will be correctly
     * taken as equal.  We can skip the expense of doing this if no rangetable
     * entries are RTE_JOIN kind.
     */
    if (hasJoinRTEs)
        groupClauses = (List *)
            flatten_join_alias_for_parser(qry, (Node *) groupClauses, 0);
 
    /*
     * Detect whether any of the grouping expressions aren't simple Vars; if
     * they're all Vars then we don't have to work so hard in the recursive
     * scans.  (Note we have to flatten aliases before this.)
     *
     * Track Vars that are included in all grouping sets separately in
     * groupClauseCommonVars, since these are the only ones we can use to
     * check for functional dependencies.
     */
    have_non_var_grouping = false;
    foreach(l, groupClauses)
    {
        TargetEntry *tle = lfirst(l);
 
        if (!IsA(tle->expr, Var))
        {
            have_non_var_grouping = true;
        }
        else if (!qry->groupingSets ||
                 list_member_int(gset_common, tle->ressortgroupref))
        {
            groupClauseCommonVars = lappend(groupClauseCommonVars, tle->expr);
        }
    }
 
    /*
     * Replace grouped variables in the targetlist and HAVING clause with Vars
     * that reference the RTE_GROUP RTE.  Emit an error message if we find any
     * ungrouped variables.
     *
     * Note: because we check resjunk tlist elements as well as regular ones,
     * this will also find ungrouped variables that came from ORDER BY and
     * WINDOW clauses.  For that matter, it's also going to examine the
     * grouping expressions themselves --- but they'll all pass the test ...
     *
     * We also finalize GROUPING expressions, but for that we need to traverse
     * the original (unflattened) clause in order to modify nodes.
     */
    clause = (Node *) qry->targetList;
    finalize_grouping_exprs(clause, pstate, qry,
                            groupClauses, hasJoinRTEs,
                            have_non_var_grouping);
    if (hasJoinRTEs)
        clause = flatten_join_alias_for_parser(qry, clause, 0);
    qry->targetList = (List *)
        substitute_grouped_columns(clause, pstate, qry,
                                   groupClauses, groupClauseCommonVars,
                                   gset_common,
                                   have_non_var_grouping,
                                   &func_grouped_rels);
 
    clause = (Node *) qry->havingQual;
    finalize_grouping_exprs(clause, pstate, qry,
                            groupClauses, hasJoinRTEs,
                            have_non_var_grouping);
    if (hasJoinRTEs)
        clause = flatten_join_alias_for_parser(qry, clause, 0);
    qry->havingQual =
        substitute_grouped_columns(clause, pstate, qry,
                                   groupClauses, groupClauseCommonVars,
                                   gset_common,
                                   have_non_var_grouping,
                                   &func_grouped_rels);
 
    /*
     * Per spec, aggregates can't appear in a recursive term.
     */
    if (pstate->p_hasAggs && hasSelfRefRTEs)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_RECURSION),
                 errmsg("aggregate functions are not allowed in a recursive query's recursive term"),
                 parser_errposition(pstate,
                                    locate_agg_of_level((Node *) qry, 0))));
}
 
/*
 * substitute_grouped_columns -
 *    Scan the given expression tree for grouped variables (variables that
 *    are listed in the groupClauses list) and replace them with Vars that
 *    reference the RTE_GROUP RTE.  Emit a suitable error message if any
 *    ungrouped variables (variables that are not listed in the groupClauses
 *    list and are not within the arguments of aggregate functions) are
 *    found.
 *
 * NOTE: we assume that the given clause has been transformed suitably for
 * parser output.  This means we can use expression_tree_mutator.
 */
static Node *
substitute_grouped_columns(Node *node, ParseState *pstate, Query *qry,
                           List *groupClauses, List *groupClauseCommonVars,
                           List *gset_common,
                           bool have_non_var_grouping,
                           List **func_grouped_rels)
{
    substitute_grouped_columns_context context;
 
    context.pstate = pstate;
    context.qry = qry;
    context.hasJoinRTEs = false;    /* assume caller flattened join Vars */
    context.groupClauses = groupClauses;
    context.groupClauseCommonVars = groupClauseCommonVars;
    context.groupClauseSubLevels = NIL;
    context.gset_common = gset_common;
    context.have_non_var_grouping = have_non_var_grouping;
    context.func_grouped_rels = func_grouped_rels;
    context.sublevels_up = 0;
    context.in_agg_direct_args = false;
    return substitute_grouped_columns_mutator(node, &context);
}
 
static Node *
substitute_grouped_columns_mutator(Node *node,
                                   substitute_grouped_columns_context *context)
{
    ListCell   *gl;
 
    if (node == NULL)
        return NULL;
 
    if (IsA(node, Aggref))
    {
        Aggref     *agg = (Aggref *) node;
 
        if ((int) agg->agglevelsup == context->sublevels_up)
        {
            /*
             * If we find an aggregate call of the original level, do not
             * recurse into its normal arguments, ORDER BY arguments, or
             * filter; grouped vars there do not need to be replaced and
             * ungrouped vars there are not an error.  But we should check
             * direct arguments as though they weren't in an aggregate.  We
             * set a special flag in the context to help produce a useful
             * error message for ungrouped vars in direct arguments.
             */
            agg = copyObject(agg);
 
            Assert(!context->in_agg_direct_args);
            context->in_agg_direct_args = true;
            agg->aggdirectargs = (List *)
                substitute_grouped_columns_mutator((Node *) agg->aggdirectargs,
                                                   context);
            context->in_agg_direct_args = false;
            return (Node *) agg;
        }
 
        /*
         * We can skip recursing into aggregates of higher levels altogether,
         * since they could not possibly contain Vars of concern to us (see
         * transformAggregateCall).  We do need to look at aggregates of lower
         * levels, however.
         */
        if ((int) agg->agglevelsup > context->sublevels_up)
            return node;
    }
 
    if (IsA(node, GroupingFunc))
    {
        GroupingFunc *grp = (GroupingFunc *) node;
 
        /* handled GroupingFunc separately, no need to recheck at this level */
 
        if ((int) grp->agglevelsup >= context->sublevels_up)
            return node;
    }
 
    /*
     * If we have any GROUP BY items that are not simple Vars, check to see if
     * subexpression as a whole matches any GROUP BY item. We need to do this
     * at every recursion level so that we recognize GROUPed-BY expressions
     * before reaching variables within them.  (Since this approach is pretty
     * expensive, we don't do it this way if the items are all simple Vars.)
     */
    if (context->have_non_var_grouping)
    {
        List       *groupClauses;
        int         attnum = 0;
 
        /* Within a subquery, we need a mutated version of the groupClauses */
        if (context->sublevels_up == 0)
            groupClauses = context->groupClauses;
        else
            groupClauses = list_nth(context->groupClauseSubLevels,
                                    context->sublevels_up - 1);
 
        foreach(gl, groupClauses)
        {
            TargetEntry *tle = (TargetEntry *) lfirst(gl);
 
            attnum++;
            if (equal(node, tle->expr))
            {
                /* acceptable, replace it with a GROUP Var */
                return (Node *) buildGroupedVar(attnum,
                                                tle->ressortgroupref,
                                                context);
            }
        }
    }
 
    /*
     * Constants are always acceptable.  We have to do this after we checked
     * the subexpression as a whole for a match, because it is possible that
     * we have GROUP BY items that are constants, and the constants would
     * become not so constant after the grouping step.
     */
    if (IsA(node, Const) ||
        IsA(node, Param))
        return node;
 
    /*
     * If we have an ungrouped Var of the original query level, we have a
     * failure.  Vars below the original query level are not a problem, and
     * neither are Vars from above it.  (If such Vars are ungrouped as far as
     * their own query level is concerned, that's someone else's problem...)
     */
    if (IsA(node, Var))
    {
        Var        *var = (Var *) node;
        RangeTblEntry *rte;
        char       *attname;
 
        if (var->varlevelsup != context->sublevels_up)
            return node;        /* it's not local to my query, ignore */
 
        /*
         * Check for a match, if we didn't do it above.
         */
        if (!context->have_non_var_grouping)
        {
            int         attnum = 0;
 
            foreach(gl, context->groupClauses)
            {
                TargetEntry *tle = (TargetEntry *) lfirst(gl);
                Var        *gvar = (Var *) tle->expr;
 
                attnum++;
                if (IsA(gvar, Var) &&
                    gvar->varno == var->varno &&
                    gvar->varattno == var->varattno &&
                    gvar->varlevelsup == 0)
                {
                    /* acceptable, replace it with a GROUP Var */
                    return (Node *) buildGroupedVar(attnum,
                                                    tle->ressortgroupref,
                                                    context);
                }
            }
        }
 
        /*
         * Check whether the Var is known functionally dependent on the GROUP
         * BY columns.  If so, we can allow the Var to be used, because the
         * grouping is really a no-op for this table.  However, this deduction
         * depends on one or more constraints of the table, so we have to add
         * those constraints to the query's constraintDeps list, because it's
         * not semantically valid anymore if the constraint(s) get dropped.
         * (Therefore, this check must be the last-ditch effort before raising
         * error: we don't want to add dependencies unnecessarily.)
         *
         * Because this is a pretty expensive check, and will have the same
         * outcome for all columns of a table, we remember which RTEs we've
         * already proven functional dependency for in the func_grouped_rels
         * list.  This test also prevents us from adding duplicate entries to
         * the constraintDeps list.
         */
        if (list_member_int(*context->func_grouped_rels, var->varno))
            return node;        /* previously proven acceptable */
 
        Assert(var->varno > 0 &&
               (int) var->varno <= list_length(context->pstate->p_rtable));
        rte = rt_fetch(var->varno, context->pstate->p_rtable);
        if (rte->rtekind == RTE_RELATION)
        {
            if (check_functional_grouping(rte->relid,
                                          var->varno,
                                          0,
                                          context->groupClauseCommonVars,
                                          &context->qry->constraintDeps))
            {
                *context->func_grouped_rels =
                    lappend_int(*context->func_grouped_rels, var->varno);
                return node;    /* acceptable */
            }
        }
 
        /* Found an ungrouped local variable; generate error message */
        attname = get_rte_attribute_name(rte, var->varattno);
        if (context->sublevels_up == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_GROUPING_ERROR),
                     errmsg("column \"%s.%s\" must appear in the GROUP BY clause or be used in an aggregate function",
                            rte->eref->aliasname, attname),
                     context->in_agg_direct_args ?
                     errdetail("Direct arguments of an ordered-set aggregate must use only grouped columns.") : 0,
                     parser_errposition(context->pstate, var->location)));
        else
            ereport(ERROR,
                    (errcode(ERRCODE_GROUPING_ERROR),
                     errmsg("subquery uses ungrouped column \"%s.%s\" from outer query",
                            rte->eref->aliasname, attname),
                     parser_errposition(context->pstate, var->location)));
    }
 
    if (IsA(node, Query))
    {
        /* Recurse into subselects */
        Query      *newnode;
 
        context->sublevels_up++;
 
        /*
         * If we have non-Var grouping expressions, we'll need a copy of the
         * groupClauses list that's mutated to match this sublevels_up depth.
         * Build one if we've not yet visited a subquery at this depth.
         */
        if (context->have_non_var_grouping &&
            context->sublevels_up > list_length(context->groupClauseSubLevels))
        {
            List       *subGroupClauses = copyObject(context->groupClauses);
 
            IncrementVarSublevelsUp((Node *) subGroupClauses,
                                    context->sublevels_up, 0);
            context->groupClauseSubLevels =
                lappend(context->groupClauseSubLevels, subGroupClauses);
            Assert(context->sublevels_up == list_length(context->groupClauseSubLevels));
        }
 
        newnode = query_tree_mutator((Query *) node,
                                     substitute_grouped_columns_mutator,
                                     context,
                                     0);
        context->sublevels_up--;
        return (Node *) newnode;
    }
    return expression_tree_mutator(node, substitute_grouped_columns_mutator,
                                   context);
}
 
/*
 * finalize_grouping_exprs -
 *    Scan the given expression tree for GROUPING() and related calls,
 *    and validate and process their arguments.
 *
 * This is split out from substitute_grouped_columns above because it needs
 * to modify the nodes (which it does in-place, not via a mutator) while
 * substitute_grouped_columns may see only a copy of the original thanks to
 * flattening of join alias vars. So here, we flatten each individual
 * GROUPING argument as we see it before comparing it.
 */
static void
finalize_grouping_exprs(Node *node, ParseState *pstate, Query *qry,
                        List *groupClauses, bool hasJoinRTEs,
                        bool have_non_var_grouping)
{
    substitute_grouped_columns_context context;
 
    context.pstate = pstate;
    context.qry = qry;
    context.hasJoinRTEs = hasJoinRTEs;
    context.groupClauses = groupClauses;
    context.groupClauseCommonVars = NIL;
    context.groupClauseSubLevels = NIL;
    context.gset_common = NIL;
    context.have_non_var_grouping = have_non_var_grouping;
    context.func_grouped_rels = NULL;
    context.sublevels_up = 0;
    context.in_agg_direct_args = false;
    finalize_grouping_exprs_walker(node, &context);
}
 
static bool
finalize_grouping_exprs_walker(Node *node,
                               substitute_grouped_columns_context *context)
{
    ListCell   *gl;
 
    if (node == NULL)
        return false;
    if (IsA(node, Const) ||
        IsA(node, Param))
        return false;           /* constants are always acceptable */
 
    if (IsA(node, Aggref))
    {
        Aggref     *agg = (Aggref *) node;
 
        if ((int) agg->agglevelsup == context->sublevels_up)
        {
            /*
             * If we find an aggregate call of the original level, do not
             * recurse into its normal arguments, ORDER BY arguments, or
             * filter; GROUPING exprs of this level are not allowed there. But
             * check direct arguments as though they weren't in an aggregate.
             */
            bool        result;
 
            Assert(!context->in_agg_direct_args);
            context->in_agg_direct_args = true;
            result = finalize_grouping_exprs_walker((Node *) agg->aggdirectargs,
                                                    context);
            context->in_agg_direct_args = false;
            return result;
        }
 
        /*
         * We can skip recursing into aggregates of higher levels altogether,
         * since they could not possibly contain exprs of concern to us (see
         * transformAggregateCall).  We do need to look at aggregates of lower
         * levels, however.
         */
        if ((int) agg->agglevelsup > context->sublevels_up)
            return false;
    }
 
    if (IsA(node, GroupingFunc))
    {
        GroupingFunc *grp = (GroupingFunc *) node;
 
        /*
         * We only need to check GroupingFunc nodes at the exact level to
         * which they belong, since they cannot mix levels in arguments.
         */
 
        if ((int) grp->agglevelsup == context->sublevels_up)
        {
            ListCell   *lc;
            List       *ref_list = NIL;
 
            foreach(lc, grp->args)
            {
                Node       *expr = lfirst(lc);
                Index       ref = 0;
 
                if (context->hasJoinRTEs)
                    expr = flatten_join_alias_for_parser(context->qry,
                                                         expr,
                                                         context->sublevels_up);
 
                /*
                 * Each expression must match a grouping entry at the current
                 * query level. Unlike the general expression case, we don't
                 * allow functional dependencies or outer references.
                 */
 
                if (IsA(expr, Var))
                {
                    Var        *var = (Var *) expr;
 
                    if (var->varlevelsup == context->sublevels_up)
                    {
                        foreach(gl, context->groupClauses)
                        {
                            TargetEntry *tle = lfirst(gl);
                            Var        *gvar = (Var *) tle->expr;
 
                            if (IsA(gvar, Var) &&
                                gvar->varno == var->varno &&
                                gvar->varattno == var->varattno &&
                                gvar->varlevelsup == 0)
                            {
                                ref = tle->ressortgroupref;
                                break;
                            }
                        }
                    }
                }
                else if (context->have_non_var_grouping)
                {
                    List       *groupClauses;
 
                    /*
                     * Within a subquery, we need a mutated version of the
                     * groupClauses
                     */
                    if (context->sublevels_up == 0)
                        groupClauses = context->groupClauses;
                    else
                        groupClauses = list_nth(context->groupClauseSubLevels,
                                                context->sublevels_up - 1);
 
                    foreach(gl, groupClauses)
                    {
                        TargetEntry *tle = lfirst(gl);
 
                        if (equal(expr, tle->expr))
                        {
                            ref = tle->ressortgroupref;
                            break;
                        }
                    }
                }
 
                if (ref == 0)
                    ereport(ERROR,
                            (errcode(ERRCODE_GROUPING_ERROR),
                             errmsg("arguments to GROUPING must be grouping expressions of the associated query level"),
                             parser_errposition(context->pstate,
                                                exprLocation(expr))));
 
                ref_list = lappend_int(ref_list, ref);
            }
 
            grp->refs = ref_list;
        }
 
        if ((int) grp->agglevelsup > context->sublevels_up)
            return false;
    }
 
    if (IsA(node, Query))
    {
        /* Recurse into subselects */
        bool        result;
 
        context->sublevels_up++;
 
        /*
         * If we have non-Var grouping expressions, we'll need a copy of the
         * groupClauses list that's mutated to match this sublevels_up depth.
         * Build one if we've not yet visited a subquery at this depth.
         */
        if (context->have_non_var_grouping &&
            context->sublevels_up > list_length(context->groupClauseSubLevels))
        {
            List       *subGroupClauses = copyObject(context->groupClauses);
 
            IncrementVarSublevelsUp((Node *) subGroupClauses,
                                    context->sublevels_up, 0);
            context->groupClauseSubLevels =
                lappend(context->groupClauseSubLevels, subGroupClauses);
            Assert(context->sublevels_up == list_length(context->groupClauseSubLevels));
        }
 
        result = query_tree_walker((Query *) node,
                                   finalize_grouping_exprs_walker,
                                   context,
                                   0);
        context->sublevels_up--;
        return result;
    }
    return expression_tree_walker(node, finalize_grouping_exprs_walker,
                                  context);
}
 
/*
 * buildGroupedVar -
 *    build a Var node that references the RTE_GROUP RTE
 */
static Var *
buildGroupedVar(int attnum, Index ressortgroupref,
                substitute_grouped_columns_context *context)
{
    Var        *var;
    ParseNamespaceItem *grouping_nsitem = context->pstate->p_grouping_nsitem;
    ParseNamespaceColumn *nscol = grouping_nsitem->p_nscolumns + attnum - 1;
 
    Assert(nscol->p_varno == grouping_nsitem->p_rtindex);
    Assert(nscol->p_varattno == attnum);
    var = makeVar(nscol->p_varno,
                  nscol->p_varattno,
                  nscol->p_vartype,
                  nscol->p_vartypmod,
                  nscol->p_varcollid,
                  context->sublevels_up);
    /* makeVar doesn't offer parameters for these, so set by hand: */
    var->varnosyn = nscol->p_varnosyn;
    var->varattnosyn = nscol->p_varattnosyn;
 
    if (context->qry->groupingSets &&
        !list_member_int(context->gset_common, ressortgroupref))
        var->varnullingrels =
            bms_add_member(var->varnullingrels, grouping_nsitem->p_rtindex);
 
    return var;
}
 
 
/*
 * Given a GroupingSet node, expand it and return a list of lists.
 *
 * For EMPTY nodes, return a list of one empty list.
 *
 * For SIMPLE nodes, return a list of one list, which is the node content.
 *
 * For CUBE and ROLLUP nodes, return a list of the expansions.
 *
 * For SET nodes, recursively expand contained CUBE and ROLLUP.
 */
static List *
expand_groupingset_node(GroupingSet *gs)
{
    List       *result = NIL;
 
    switch (gs->kind)
    {
        case GROUPING_SET_EMPTY:
            result = list_make1(NIL);
            break;
 
        case GROUPING_SET_SIMPLE:
            result = list_make1(gs->content);
            break;
 
        case GROUPING_SET_ROLLUP:
            {
                List       *rollup_val = gs->content;
                ListCell   *lc;
                int         curgroup_size = list_length(gs->content);
 
                while (curgroup_size > 0)
                {
                    List       *current_result = NIL;
                    int         i = curgroup_size;
 
                    foreach(lc, rollup_val)
                    {
                        GroupingSet *gs_current = (GroupingSet *) lfirst(lc);
 
                        Assert(gs_current->kind == GROUPING_SET_SIMPLE);
 
                        current_result = list_concat(current_result,
                                                     gs_current->content);
 
                        /* If we are done with making the current group, break */
                        if (--i == 0)
                            break;
                    }
 
                    result = lappend(result, current_result);
                    --curgroup_size;
                }
 
                result = lappend(result, NIL);
            }
            break;
 
        case GROUPING_SET_CUBE:
            {
                List       *cube_list = gs->content;
                int         number_bits = list_length(cube_list);
                uint32      num_sets;
                uint32      i;
 
                /* parser should cap this much lower */
                Assert(number_bits < 31);
 
                num_sets = (1U << number_bits);
 
                for (i = 0; i < num_sets; i++)
                {
                    List       *current_result = NIL;
                    ListCell   *lc;
                    uint32      mask = 1U;
 
                    foreach(lc, cube_list)
                    {
                        GroupingSet *gs_current = (GroupingSet *) lfirst(lc);
 
                        Assert(gs_current->kind == GROUPING_SET_SIMPLE);
 
                        if (mask & i)
                            current_result = list_concat(current_result,
                                                         gs_current->content);
 
                        mask <<= 1;
                    }
 
                    result = lappend(result, current_result);
                }
            }
            break;
 
        case GROUPING_SET_SETS:
            {
                ListCell   *lc;
 
                foreach(lc, gs->content)
                {
                    List       *current_result = expand_groupingset_node(lfirst(lc));
 
                    result = list_concat(result, current_result);
                }
            }
            break;
    }
 
    return result;
}
 
/* list_sort comparator to sort sub-lists by length */
static int
cmp_list_len_asc(const ListCell *a, const ListCell *b)
{
    int         la = list_length((const List *) lfirst(a));
    int         lb = list_length((const List *) lfirst(b));
 
    return pg_cmp_s32(la, lb);
}
 
/* list_sort comparator to sort sub-lists by length and contents */
static int
cmp_list_len_contents_asc(const ListCell *a, const ListCell *b)
{
    int         res = cmp_list_len_asc(a, b);
 
    if (res == 0)
    {
        List       *la = (List *) lfirst(a);
        List       *lb = (List *) lfirst(b);
        ListCell   *lca;
        ListCell   *lcb;
 
        forboth(lca, la, lcb, lb)
        {
            int         va = lfirst_int(lca);
            int         vb = lfirst_int(lcb);
 
            if (va > vb)
                return 1;
            if (va < vb)
                return -1;
        }
    }
 
    return res;
}
 
/*
 * Expand a groupingSets clause to a flat list of grouping sets.
 * The returned list is sorted by length, shortest sets first.
 *
 * This is mainly for the planner, but we use it here too to do
 * some consistency checks.
 */
List *
expand_grouping_sets(List *groupingSets, bool groupDistinct, int limit)
{
    List       *expanded_groups = NIL;
    List       *result = NIL;
    double      numsets = 1;
    ListCell   *lc;
 
    if (groupingSets == NIL)
        return NIL;
 
    foreach(lc, groupingSets)
    {
        List       *current_result = NIL;
        GroupingSet *gs = lfirst(lc);
 
        current_result = expand_groupingset_node(gs);
 
        Assert(current_result != NIL);
 
        numsets *= list_length(current_result);
 
        if (limit >= 0 && numsets > limit)
            return NIL;
 
        expanded_groups = lappend(expanded_groups, current_result);
    }
 
    /*
     * Do cartesian product between sublists of expanded_groups. While at it,
     * remove any duplicate elements from individual grouping sets (we must
     * NOT change the number of sets though)
     */
 
    foreach(lc, (List *) linitial(expanded_groups))
    {
        result = lappend(result, list_union_int(NIL, (List *) lfirst(lc)));
    }
 
    for_each_from(lc, expanded_groups, 1)
    {
        List       *p = lfirst(lc);
        List       *new_result = NIL;
        ListCell   *lc2;
 
        foreach(lc2, result)
        {
            List       *q = lfirst(lc2);
            ListCell   *lc3;
 
            foreach(lc3, p)
            {
                new_result = lappend(new_result,
                                     list_union_int(q, (List *) lfirst(lc3)));
            }
        }
        result = new_result;
    }
 
    /* Now sort the lists by length and deduplicate if necessary */
    if (!groupDistinct || list_length(result) < 2)
        list_sort(result, cmp_list_len_asc);
    else
    {
        ListCell   *cell;
        List       *prev;
 
        /* Sort each groupset individually */
        foreach(cell, result)
            list_sort(lfirst(cell), list_int_cmp);
 
        /* Now sort the list of groupsets by length and contents */
        list_sort(result, cmp_list_len_contents_asc);
 
        /* Finally, remove duplicates */
        prev = linitial(result);
        for_each_from(cell, result, 1)
        {
            if (equal(lfirst(cell), prev))
                result = foreach_delete_current(result, cell);
            else
                prev = lfirst(cell);
        }
    }
 
    return result;
}
 
/*
 * get_aggregate_argtypes
 *  Identify the specific datatypes passed to an aggregate call.
 *
 * Given an Aggref, extract the actual datatypes of the input arguments.
 * The input datatypes are reported in a way that matches up with the
 * aggregate's declaration, ie, any ORDER BY columns attached to a plain
 * aggregate are ignored, but we report both direct and aggregated args of
 * an ordered-set aggregate.
 *
 * Datatypes are returned into inputTypes[], which must reference an array
 * of length FUNC_MAX_ARGS.
 *
 * The function result is the number of actual arguments.
 */
int
get_aggregate_argtypes(Aggref *aggref, Oid *inputTypes)
{
    int         numArguments = 0;
    ListCell   *lc;
 
    Assert(list_length(aggref->aggargtypes) <= FUNC_MAX_ARGS);
 
    foreach(lc, aggref->aggargtypes)
    {
        inputTypes[numArguments++] = lfirst_oid(lc);
    }
 
    return numArguments;
}
 
/*
 * resolve_aggregate_transtype
 *  Identify the transition state value's datatype for an aggregate call.
 *
 * This function resolves a polymorphic aggregate's state datatype.
 * It must be passed the aggtranstype from the aggregate's catalog entry,
 * as well as the actual argument types extracted by get_aggregate_argtypes.
 * (We could fetch pg_aggregate.aggtranstype internally, but all existing
 * callers already have the value at hand, so we make them pass it.)
 */
Oid
resolve_aggregate_transtype(Oid aggfuncid,
                            Oid aggtranstype,
                            Oid *inputTypes,
                            int numArguments)
{
    /* resolve actual type of transition state, if polymorphic */
    if (IsPolymorphicType(aggtranstype))
    {
        /* have to fetch the agg's declared input types... */
        Oid        *declaredArgTypes;
        int         agg_nargs;
 
        (void) get_func_signature(aggfuncid, &declaredArgTypes, &agg_nargs);
 
        /*
         * VARIADIC ANY aggs could have more actual than declared args, but
         * such extra args can't affect polymorphic type resolution.
         */
        Assert(agg_nargs <= numArguments);
 
        aggtranstype = enforce_generic_type_consistency(inputTypes,
                                                        declaredArgTypes,
                                                        agg_nargs,
                                                        aggtranstype,
                                                        false);
        pfree(declaredArgTypes);
    }
    return aggtranstype;
}
 
/*
 * agg_args_support_sendreceive
 *      Returns true if all non-byval types of aggref's args have send and
 *      receive functions.
 */
bool
agg_args_support_sendreceive(Aggref *aggref)
{
    ListCell   *lc;
 
    foreach(lc, aggref->args)
    {
        HeapTuple   typeTuple;
        Form_pg_type pt;
        TargetEntry *tle = (TargetEntry *) lfirst(lc);
        Oid         type = exprType((Node *) tle->expr);
 
        /*
         * RECORD is a special case: it has typsend/typreceive functions, but
         * record_recv only works if passed the correct typmod to identify the
         * specific anonymous record type.  array_agg_deserialize cannot do
         * that, so we have to disclaim support for the case.
         */
        if (type == RECORDOID)
            return false;
 
        typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type));
        if (!HeapTupleIsValid(typeTuple))
            elog(ERROR, "cache lookup failed for type %u", type);
 
        pt = (Form_pg_type) GETSTRUCT(typeTuple);
 
        if (!pt->typbyval &&
            (!OidIsValid(pt->typsend) || !OidIsValid(pt->typreceive)))
        {
            ReleaseSysCache(typeTuple);
            return false;
        }
        ReleaseSysCache(typeTuple);
    }
    return true;
}
 
/*
 * Create an expression tree for the transition function of an aggregate.
 * This is needed so that polymorphic functions can be used within an
 * aggregate --- without the expression tree, such functions would not know
 * the datatypes they are supposed to use.  (The trees will never actually
 * be executed, however, so we can skimp a bit on correctness.)
 *
 * agg_input_types and agg_state_type identifies the input types of the
 * aggregate.  These should be resolved to actual types (ie, none should
 * ever be ANYELEMENT etc).
 * agg_input_collation is the aggregate function's input collation.
 *
 * For an ordered-set aggregate, remember that agg_input_types describes
 * the direct arguments followed by the aggregated arguments.
 *
 * transfn_oid and invtransfn_oid identify the funcs to be called; the
 * latter may be InvalidOid, however if invtransfn_oid is set then
 * transfn_oid must also be set.
 *
 * transfn_oid may also be passed as the aggcombinefn when the *transfnexpr is
 * to be used for a combine aggregate phase.  We expect invtransfn_oid to be
 * InvalidOid in this case since there is no such thing as an inverse
 * combinefn.
 *
 * Pointers to the constructed trees are returned into *transfnexpr,
 * *invtransfnexpr. If there is no invtransfn, the respective pointer is set
 * to NULL.  Since use of the invtransfn is optional, NULL may be passed for
 * invtransfnexpr.
 */
void
build_aggregate_transfn_expr(Oid *agg_input_types,
                             int agg_num_inputs,
                             int agg_num_direct_inputs,
                             bool agg_variadic,
                             Oid agg_state_type,
                             Oid agg_input_collation,
                             Oid transfn_oid,
                             Oid invtransfn_oid,
                             Expr **transfnexpr,
                             Expr **invtransfnexpr)
{
    List       *args;
    FuncExpr   *fexpr;
    int         i;
 
    /*
     * Build arg list to use in the transfn FuncExpr node.
     */
    args = list_make1(make_agg_arg(agg_state_type, agg_input_collation));
 
    for (i = agg_num_direct_inputs; i < agg_num_inputs; i++)
    {
        args = lappend(args,
                       make_agg_arg(agg_input_types[i], agg_input_collation));
    }
 
    fexpr = makeFuncExpr(transfn_oid,
                         agg_state_type,
                         args,
                         InvalidOid,
                         agg_input_collation,
                         COERCE_EXPLICIT_CALL);
    fexpr->funcvariadic = agg_variadic;
    *transfnexpr = (Expr *) fexpr;
 
    /*
     * Build invtransfn expression if requested, with same args as transfn
     */
    if (invtransfnexpr != NULL)
    {
        if (OidIsValid(invtransfn_oid))
        {
            fexpr = makeFuncExpr(invtransfn_oid,
                                 agg_state_type,
                                 args,
                                 InvalidOid,
                                 agg_input_collation,
                                 COERCE_EXPLICIT_CALL);
            fexpr->funcvariadic = agg_variadic;
            *invtransfnexpr = (Expr *) fexpr;
        }
        else
            *invtransfnexpr = NULL;
    }
}
 
/*
 * Like build_aggregate_transfn_expr, but creates an expression tree for the
 * serialization function of an aggregate.
 */
void
build_aggregate_serialfn_expr(Oid serialfn_oid,
                              Expr **serialfnexpr)
{
    List       *args;
    FuncExpr   *fexpr;
 
    /* serialfn always takes INTERNAL and returns BYTEA */
    args = list_make1(make_agg_arg(INTERNALOID, InvalidOid));
 
    fexpr = makeFuncExpr(serialfn_oid,
                         BYTEAOID,
                         args,
                         InvalidOid,
                         InvalidOid,
                         COERCE_EXPLICIT_CALL);
    *serialfnexpr = (Expr *) fexpr;
}
 
/*
 * Like build_aggregate_transfn_expr, but creates an expression tree for the
 * deserialization function of an aggregate.
 */
void
build_aggregate_deserialfn_expr(Oid deserialfn_oid,
                                Expr **deserialfnexpr)
{
    List       *args;
    FuncExpr   *fexpr;
 
    /* deserialfn always takes BYTEA, INTERNAL and returns INTERNAL */
    args = list_make2(make_agg_arg(BYTEAOID, InvalidOid),
                      make_agg_arg(INTERNALOID, InvalidOid));
 
    fexpr = makeFuncExpr(deserialfn_oid,
                         INTERNALOID,
                         args,
                         InvalidOid,
                         InvalidOid,
                         COERCE_EXPLICIT_CALL);
    *deserialfnexpr = (Expr *) fexpr;
}
 
/*
 * Like build_aggregate_transfn_expr, but creates an expression tree for the
 * final function of an aggregate, rather than the transition function.
 */
void
build_aggregate_finalfn_expr(Oid *agg_input_types,
                             int num_finalfn_inputs,
                             Oid agg_state_type,
                             Oid agg_result_type,
                             Oid agg_input_collation,
                             Oid finalfn_oid,
                             Expr **finalfnexpr)
{
    List       *args;
    int         i;
 
    /*
     * Build expr tree for final function
     */
    args = list_make1(make_agg_arg(agg_state_type, agg_input_collation));
 
    /* finalfn may take additional args, which match agg's input types */
    for (i = 0; i < num_finalfn_inputs - 1; i++)
    {
        args = lappend(args,
                       make_agg_arg(agg_input_types[i], agg_input_collation));
    }
 
    *finalfnexpr = (Expr *) makeFuncExpr(finalfn_oid,
                                         agg_result_type,
                                         args,
                                         InvalidOid,
                                         agg_input_collation,
                                         COERCE_EXPLICIT_CALL);
    /* finalfn is currently never treated as variadic */
}
 
/*
 * Convenience function to build dummy argument expressions for aggregates.
 *
 * We really only care that an aggregate support function can discover its
 * actual argument types at runtime using get_fn_expr_argtype(), so it's okay
 * to use Param nodes that don't correspond to any real Param.
 */
static Node *
make_agg_arg(Oid argtype, Oid argcollation)
{
    Param      *argp = makeNode(Param);
 
    argp->paramkind = PARAM_EXEC;
    argp->paramid = -1;
    argp->paramtype = argtype;
    argp->paramtypmod = -1;
    argp->paramcollid = argcollation;
    argp->location = -1;
    return (Node *) argp;
}