setrefs.c

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/*-------------------------------------------------------------------------
 *
 * setrefs.c
 *    Post-processing of a completed plan tree: fix references to subplan
 *    vars, compute regproc values for operators, etc
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/plan/setrefs.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/transam.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/pathnode.h"
#include "optimizer/planmain.h"
#include "optimizer/tlist.h"
#include "tcop/utility.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


typedef struct
{
    Index       varno;          /* RT index of Var */
    AttrNumber  varattno;       /* attr number of Var */
    AttrNumber  resno;          /* TLE position of Var */
} tlist_vinfo;

typedef struct
{
    List       *tlist;          /* underlying target list */
    int         num_vars;       /* number of plain Var tlist entries */
    bool        has_ph_vars;    /* are there PlaceHolderVar entries? */
    bool        has_non_vars;   /* are there other entries? */
    /* array of num_vars entries: */
    tlist_vinfo vars[1];        /* VARIABLE LENGTH ARRAY */
} indexed_tlist;                /* VARIABLE LENGTH STRUCT */

typedef struct
{
    PlannerInfo *root;
    int         rtoffset;
} fix_scan_expr_context;

typedef struct
{
    PlannerInfo *root;
    indexed_tlist *outer_itlist;
    indexed_tlist *inner_itlist;
    Index       acceptable_rel;
    int         rtoffset;
} fix_join_expr_context;

typedef struct
{
    PlannerInfo *root;
    indexed_tlist *subplan_itlist;
    Index       newvarno;
    int         rtoffset;
} fix_upper_expr_context;

/*
 * Check if a Const node is a regclass value.  We accept plain OID too,
 * since a regclass Const will get folded to that type if it's an argument
 * to oideq or similar operators.  (This might result in some extraneous
 * values in a plan's list of relation dependencies, but the worst result
 * would be occasional useless replans.)
 */
#define ISREGCLASSCONST(con) \
    (((con)->consttype == REGCLASSOID || (con)->consttype == OIDOID) && \
     !(con)->constisnull)

#define fix_scan_list(root, lst, rtoffset) \
    ((List *) fix_scan_expr(root, (Node *) (lst), rtoffset))

static Plan *set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset);
static Plan *set_indexonlyscan_references(PlannerInfo *root,
                             IndexOnlyScan *plan,
                             int rtoffset);
static Plan *set_subqueryscan_references(PlannerInfo *root,
                            SubqueryScan *plan,
                            int rtoffset);
static bool trivial_subqueryscan(SubqueryScan *plan);
static Node *fix_scan_expr(PlannerInfo *root, Node *node, int rtoffset);
static Node *fix_scan_expr_mutator(Node *node, fix_scan_expr_context *context);
static bool fix_scan_expr_walker(Node *node, fix_scan_expr_context *context);
static void set_join_references(PlannerInfo *root, Join *join, int rtoffset);
static void set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset);
static void set_dummy_tlist_references(Plan *plan, int rtoffset);
static indexed_tlist *build_tlist_index(List *tlist);
static Var *search_indexed_tlist_for_var(Var *var,
                             indexed_tlist *itlist,
                             Index newvarno,
                             int rtoffset);
static Var *search_indexed_tlist_for_non_var(Node *node,
                                 indexed_tlist *itlist,
                                 Index newvarno);
static Var *search_indexed_tlist_for_sortgroupref(Node *node,
                                      Index sortgroupref,
                                      indexed_tlist *itlist,
                                      Index newvarno);
static List *fix_join_expr(PlannerInfo *root,
              List *clauses,
              indexed_tlist *outer_itlist,
              indexed_tlist *inner_itlist,
              Index acceptable_rel, int rtoffset);
static Node *fix_join_expr_mutator(Node *node,
                      fix_join_expr_context *context);
static Node *fix_upper_expr(PlannerInfo *root,
               Node *node,
               indexed_tlist *subplan_itlist,
               Index newvarno,
               int rtoffset);
static Node *fix_upper_expr_mutator(Node *node,
                       fix_upper_expr_context *context);
static List *set_returning_clause_references(PlannerInfo *root,
                                List *rlist,
                                Plan *topplan,
                                Index resultRelation,
                                int rtoffset);
static bool fix_opfuncids_walker(Node *node, void *context);
static bool extract_query_dependencies_walker(Node *node,
                                  PlannerInfo *context);


/*****************************************************************************
 *
 *      SUBPLAN REFERENCES
 *
 *****************************************************************************/

/*
 * set_plan_references
 *
 * This is the final processing pass of the planner/optimizer.  The plan
 * tree is complete; we just have to adjust some representational details
 * for the convenience of the executor:
 *
 * 1. We flatten the various subquery rangetables into a single list, and
 * zero out RangeTblEntry fields that are not useful to the executor.
 *
 * 2. We adjust Vars in scan nodes to be consistent with the flat rangetable.
 *
 * 3. We adjust Vars in upper plan nodes to refer to the outputs of their
 * subplans.
 *
 * 4. We compute regproc OIDs for operators (ie, we look up the function
 * that implements each op).
 *
 * 5. We create lists of specific objects that the plan depends on.
 * This will be used by plancache.c to drive invalidation of cached plans.
 * Relation dependencies are represented by OIDs, and everything else by
 * PlanInvalItems (this distinction is motivated by the shared-inval APIs).
 * Currently, relations and user-defined functions are the only types of
 * objects that are explicitly tracked this way.
 *
 * We also perform one final optimization step, which is to delete
 * SubqueryScan plan nodes that aren't doing anything useful (ie, have
 * no qual and a no-op targetlist).  The reason for doing this last is that
 * it can't readily be done before set_plan_references, because it would
 * break set_upper_references: the Vars in the subquery's top tlist
 * wouldn't match up with the Vars in the outer plan tree.  The SubqueryScan
 * serves a necessary function as a buffer between outer query and subquery
 * variable numbering ... but after we've flattened the rangetable this is
 * no longer a problem, since then there's only one rtindex namespace.
 *
 * set_plan_references recursively traverses the whole plan tree.
 *
 * The return value is normally the same Plan node passed in, but can be
 * different when the passed-in Plan is a SubqueryScan we decide isn't needed.
 *
 * The flattened rangetable entries are appended to root->glob->finalrtable.
 * Also, rowmarks entries are appended to root->glob->finalrowmarks, and the
 * RT indexes of ModifyTable result relations to root->glob->resultRelations.
 * Plan dependencies are appended to root->glob->relationOids (for relations)
 * and root->glob->invalItems (for everything else).
 *
 * Notice that we modify Plan nodes in-place, but use expression_tree_mutator
 * to process targetlist and qual expressions.  We can assume that the Plan
 * nodes were just built by the planner and are not multiply referenced, but
 * it's not so safe to assume that for expression tree nodes.
 */
Plan *
set_plan_references(PlannerInfo *root, Plan *plan)
{
    PlannerGlobal *glob = root->glob;
    int         rtoffset = list_length(glob->finalrtable);
    ListCell   *lc;

    /*
     * In the flat rangetable, we zero out substructure pointers that are not
     * needed by the executor; this reduces the storage space and copying cost
     * for cached plans.  We keep only the alias and eref Alias fields, which
     * are needed by EXPLAIN, and the selectedCols and modifiedCols bitmaps,
     * which are needed for executor-startup permissions checking and for
     * trigger event checking.
     */
    foreach(lc, root->parse->rtable)
    {
        RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
        RangeTblEntry *newrte;

        /* flat copy to duplicate all the scalar fields */
        newrte = (RangeTblEntry *) palloc(sizeof(RangeTblEntry));
        memcpy(newrte, rte, sizeof(RangeTblEntry));

        /* zap unneeded sub-structure */
        newrte->subquery = NULL;
        newrte->joinaliasvars = NIL;
        newrte->funcexpr = NULL;
        newrte->funccoltypes = NIL;
        newrte->funccoltypmods = NIL;
        newrte->funccolcollations = NIL;
        newrte->values_lists = NIL;
        newrte->values_collations = NIL;
        newrte->ctecoltypes = NIL;
        newrte->ctecoltypmods = NIL;
        newrte->ctecolcollations = NIL;

        glob->finalrtable = lappend(glob->finalrtable, newrte);

        /*
         * If it's a plain relation RTE, add the table to relationOids.
         *
         * We do this even though the RTE might be unreferenced in the plan
         * tree; this would correspond to cases such as views that were
         * expanded, child tables that were eliminated by constraint
         * exclusion, etc.  Schema invalidation on such a rel must still force
         * rebuilding of the plan.
         *
         * Note we don't bother to avoid duplicate list entries.  We could,
         * but it would probably cost more cycles than it would save.
         */
        if (newrte->rtekind == RTE_RELATION)
            glob->relationOids = lappend_oid(glob->relationOids,
                                             newrte->relid);
    }

    /*
     * Check for RT index overflow; it's very unlikely, but if it did happen,
     * the executor would get confused by varnos that match the special varno
     * values.
     */
    if (IS_SPECIAL_VARNO(list_length(glob->finalrtable)))
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("too many range table entries")));

    /*
     * Adjust RT indexes of PlanRowMarks and add to final rowmarks list
     */
    foreach(lc, root->rowMarks)
    {
        PlanRowMark *rc = (PlanRowMark *) lfirst(lc);
        PlanRowMark *newrc;

        Assert(IsA(rc, PlanRowMark));

        /* flat copy is enough since all fields are scalars */
        newrc = (PlanRowMark *) palloc(sizeof(PlanRowMark));
        memcpy(newrc, rc, sizeof(PlanRowMark));

        /* adjust indexes ... but *not* the rowmarkId */
        newrc->rti += rtoffset;
        newrc->prti += rtoffset;

        glob->finalrowmarks = lappend(glob->finalrowmarks, newrc);
    }

    /* Now fix the Plan tree */
    return set_plan_refs(root, plan, rtoffset);
}

/*
 * set_plan_refs: recurse through the Plan nodes of a single subquery level
 */
static Plan *
set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
{
    ListCell   *l;

    if (plan == NULL)
        return NULL;

    /*
     * Plan-type-specific fixes
     */
    switch (nodeTag(plan))
    {
        case T_SeqScan:
            {
                SeqScan    *splan = (SeqScan *) plan;

                splan->scanrelid += rtoffset;
                splan->plan.targetlist =
                    fix_scan_list(root, splan->plan.targetlist, rtoffset);
                splan->plan.qual =
                    fix_scan_list(root, splan->plan.qual, rtoffset);
            }
            break;
        case T_IndexScan:
            {
                IndexScan  *splan = (IndexScan *) plan;

                splan->scan.scanrelid += rtoffset;
                splan->scan.plan.targetlist =
                    fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
                splan->scan.plan.qual =
                    fix_scan_list(root, splan->scan.plan.qual, rtoffset);
                splan->indexqual =
                    fix_scan_list(root, splan->indexqual, rtoffset);
                splan->indexqualorig =
                    fix_scan_list(root, splan->indexqualorig, rtoffset);
                splan->indexorderby =
                    fix_scan_list(root, splan->indexorderby, rtoffset);
                splan->indexorderbyorig =
                    fix_scan_list(root, splan->indexorderbyorig, rtoffset);
            }
            break;
        case T_IndexOnlyScan:
            {
                IndexOnlyScan *splan = (IndexOnlyScan *) plan;

                return set_indexonlyscan_references(root, splan, rtoffset);
            }
            break;
        case T_BitmapIndexScan:
            {
                BitmapIndexScan *splan = (BitmapIndexScan *) plan;

                splan->scan.scanrelid += rtoffset;
                /* no need to fix targetlist and qual */
                Assert(splan->scan.plan.targetlist == NIL);
                Assert(splan->scan.plan.qual == NIL);
                splan->indexqual =
                    fix_scan_list(root, splan->indexqual, rtoffset);
                splan->indexqualorig =
                    fix_scan_list(root, splan->indexqualorig, rtoffset);
            }
            break;
        case T_BitmapHeapScan:
            {
                BitmapHeapScan *splan = (BitmapHeapScan *) plan;

                splan->scan.scanrelid += rtoffset;
                splan->scan.plan.targetlist =
                    fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
                splan->scan.plan.qual =
                    fix_scan_list(root, splan->scan.plan.qual, rtoffset);
                splan->bitmapqualorig =
                    fix_scan_list(root, splan->bitmapqualorig, rtoffset);
            }
            break;
        case T_TidScan:
            {
                TidScan    *splan = (TidScan *) plan;

                splan->scan.scanrelid += rtoffset;
                splan->scan.plan.targetlist =
                    fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
                splan->scan.plan.qual =
                    fix_scan_list(root, splan->scan.plan.qual, rtoffset);
                splan->tidquals =
                    fix_scan_list(root, splan->tidquals, rtoffset);
            }
            break;
        case T_SubqueryScan:
            /* Needs special treatment, see comments below */
            return set_subqueryscan_references(root,
                                               (SubqueryScan *) plan,
                                               rtoffset);
        case T_FunctionScan:
            {
                FunctionScan *splan = (FunctionScan *) plan;

                splan->scan.scanrelid += rtoffset;
                splan->scan.plan.targetlist =
                    fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
                splan->scan.plan.qual =
                    fix_scan_list(root, splan->scan.plan.qual, rtoffset);
                splan->funcexpr =
                    fix_scan_expr(root, splan->funcexpr, rtoffset);
            }
            break;
        case T_ValuesScan:
            {
                ValuesScan *splan = (ValuesScan *) plan;

                splan->scan.scanrelid += rtoffset;
                splan->scan.plan.targetlist =
                    fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
                splan->scan.plan.qual =
                    fix_scan_list(root, splan->scan.plan.qual, rtoffset);
                splan->values_lists =
                    fix_scan_list(root, splan->values_lists, rtoffset);
            }
            break;
        case T_CteScan:
            {
                CteScan    *splan = (CteScan *) plan;

                splan->scan.scanrelid += rtoffset;
                splan->scan.plan.targetlist =
                    fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
                splan->scan.plan.qual =
                    fix_scan_list(root, splan->scan.plan.qual, rtoffset);
            }
            break;
        case T_WorkTableScan:
            {
                WorkTableScan *splan = (WorkTableScan *) plan;

                splan->scan.scanrelid += rtoffset;
                splan->scan.plan.targetlist =
                    fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
                splan->scan.plan.qual =
                    fix_scan_list(root, splan->scan.plan.qual, rtoffset);
            }
            break;
        case T_ForeignScan:
            {
                ForeignScan *splan = (ForeignScan *) plan;

                splan->scan.scanrelid += rtoffset;
                splan->scan.plan.targetlist =
                    fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
                splan->scan.plan.qual =
                    fix_scan_list(root, splan->scan.plan.qual, rtoffset);
                splan->fdw_exprs =
                    fix_scan_list(root, splan->fdw_exprs, rtoffset);
            }
            break;

        case T_NestLoop:
        case T_MergeJoin:
        case T_HashJoin:
            set_join_references(root, (Join *) plan, rtoffset);
            break;

        case T_Hash:
        case T_Material:
        case T_Sort:
        case T_Unique:
        case T_SetOp:

            /*
             * These plan types don't actually bother to evaluate their
             * targetlists, because they just return their unmodified input
             * tuples.  Even though the targetlist won't be used by the
             * executor, we fix it up for possible use by EXPLAIN (not to
             * mention ease of debugging --- wrong varnos are very confusing).
             */
            set_dummy_tlist_references(plan, rtoffset);

            /*
             * Since these plan types don't check quals either, we should not
             * find any qual expression attached to them.
             */
            Assert(plan->qual == NIL);
            break;
        case T_LockRows:
            {
                LockRows   *splan = (LockRows *) plan;

                /*
                 * Like the plan types above, LockRows doesn't evaluate its
                 * tlist or quals.  But we have to fix up the RT indexes in
                 * its rowmarks.
                 */
                set_dummy_tlist_references(plan, rtoffset);
                Assert(splan->plan.qual == NIL);

                foreach(l, splan->rowMarks)
                {
                    PlanRowMark *rc = (PlanRowMark *) lfirst(l);

                    rc->rti += rtoffset;
                    rc->prti += rtoffset;
                }
            }
            break;
        case T_Limit:
            {
                Limit      *splan = (Limit *) plan;

                /*
                 * Like the plan types above, Limit doesn't evaluate its tlist
                 * or quals.  It does have live expressions for limit/offset,
                 * however; and those cannot contain subplan variable refs, so
                 * fix_scan_expr works for them.
                 */
                set_dummy_tlist_references(plan, rtoffset);
                Assert(splan->plan.qual == NIL);

                splan->limitOffset =
                    fix_scan_expr(root, splan->limitOffset, rtoffset);
                splan->limitCount =
                    fix_scan_expr(root, splan->limitCount, rtoffset);
            }
            break;
        case T_Agg:
        case T_Group:
            set_upper_references(root, plan, rtoffset);
            break;
        case T_WindowAgg:
            {
                WindowAgg  *wplan = (WindowAgg *) plan;

                set_upper_references(root, plan, rtoffset);

                /*
                 * Like Limit node limit/offset expressions, WindowAgg has
                 * frame offset expressions, which cannot contain subplan
                 * variable refs, so fix_scan_expr works for them.
                 */
                wplan->startOffset =
                    fix_scan_expr(root, wplan->startOffset, rtoffset);
                wplan->endOffset =
                    fix_scan_expr(root, wplan->endOffset, rtoffset);
            }
            break;
        case T_Result:
            {
                Result     *splan = (Result *) plan;

                /*
                 * Result may or may not have a subplan; if not, it's more
                 * like a scan node than an upper node.
                 */
                if (splan->plan.lefttree != NULL)
                    set_upper_references(root, plan, rtoffset);
                else
                {
                    splan->plan.targetlist =
                        fix_scan_list(root, splan->plan.targetlist, rtoffset);
                    splan->plan.qual =
                        fix_scan_list(root, splan->plan.qual, rtoffset);
                }
                /* resconstantqual can't contain any subplan variable refs */
                splan->resconstantqual =
                    fix_scan_expr(root, splan->resconstantqual, rtoffset);
            }
            break;
        case T_ModifyTable:
            {
                ModifyTable *splan = (ModifyTable *) plan;

                Assert(splan->plan.targetlist == NIL);
                Assert(splan->plan.qual == NIL);

                if (splan->returningLists)
                {
                    List       *newRL = NIL;
                    ListCell   *lcrl,
                               *lcrr,
                               *lcp;

                    /*
                     * Pass each per-subplan returningList through
                     * set_returning_clause_references().
                     */
                    Assert(list_length(splan->returningLists) == list_length(splan->resultRelations));
                    Assert(list_length(splan->returningLists) == list_length(splan->plans));
                    forthree(lcrl, splan->returningLists,
                             lcrr, splan->resultRelations,
                             lcp, splan->plans)
                    {
                        List       *rlist = (List *) lfirst(lcrl);
                        Index       resultrel = lfirst_int(lcrr);
                        Plan       *subplan = (Plan *) lfirst(lcp);

                        rlist = set_returning_clause_references(root,
                                                                rlist,
                                                                subplan,
                                                                resultrel,
                                                                rtoffset);
                        newRL = lappend(newRL, rlist);
                    }
                    splan->returningLists = newRL;

                    /*
                     * Set up the visible plan targetlist as being the same as
                     * the first RETURNING list. This is for the use of
                     * EXPLAIN; the executor won't pay any attention to the
                     * targetlist.  We postpone this step until here so that
                     * we don't have to do set_returning_clause_references()
                     * twice on identical targetlists.
                     */
                    splan->plan.targetlist = copyObject(linitial(newRL));
                }

                foreach(l, splan->resultRelations)
                {
                    lfirst_int(l) += rtoffset;
                }
                foreach(l, splan->rowMarks)
                {
                    PlanRowMark *rc = (PlanRowMark *) lfirst(l);

                    rc->rti += rtoffset;
                    rc->prti += rtoffset;
                }
                foreach(l, splan->plans)
                {
                    lfirst(l) = set_plan_refs(root,
                                              (Plan *) lfirst(l),
                                              rtoffset);
                }

                /*
                 * Append this ModifyTable node's final result relation RT
                 * index(es) to the global list for the plan, and set its
                 * resultRelIndex to reflect their starting position in the
                 * global list.
                 */
                splan->resultRelIndex = list_length(root->glob->resultRelations);
                root->glob->resultRelations =
                    list_concat(root->glob->resultRelations,
                                list_copy(splan->resultRelations));
            }
            break;
        case T_Append:
            {
                Append     *splan = (Append *) plan;

                /*
                 * Append, like Sort et al, doesn't actually evaluate its
                 * targetlist or check quals.
                 */
                set_dummy_tlist_references(plan, rtoffset);
                Assert(splan->plan.qual == NIL);
                foreach(l, splan->appendplans)
                {
                    lfirst(l) = set_plan_refs(root,
                                              (Plan *) lfirst(l),
                                              rtoffset);
                }
            }
            break;
        case T_MergeAppend:
            {
                MergeAppend *splan = (MergeAppend *) plan;

                /*
                 * MergeAppend, like Sort et al, doesn't actually evaluate its
                 * targetlist or check quals.
                 */
                set_dummy_tlist_references(plan, rtoffset);
                Assert(splan->plan.qual == NIL);
                foreach(l, splan->mergeplans)
                {
                    lfirst(l) = set_plan_refs(root,
                                              (Plan *) lfirst(l),
                                              rtoffset);
                }
            }
            break;
        case T_RecursiveUnion:
            /* This doesn't evaluate targetlist or check quals either */
            set_dummy_tlist_references(plan, rtoffset);
            Assert(plan->qual == NIL);
            break;
        case T_BitmapAnd:
            {
                BitmapAnd  *splan = (BitmapAnd *) plan;

                /* BitmapAnd works like Append, but has no tlist */
                Assert(splan->plan.targetlist == NIL);
                Assert(splan->plan.qual == NIL);
                foreach(l, splan->bitmapplans)
                {
                    lfirst(l) = set_plan_refs(root,
                                              (Plan *) lfirst(l),
                                              rtoffset);
                }
            }
            break;
        case T_BitmapOr:
            {
                BitmapOr   *splan = (BitmapOr *) plan;

                /* BitmapOr works like Append, but has no tlist */
                Assert(splan->plan.targetlist == NIL);
                Assert(splan->plan.qual == NIL);
                foreach(l, splan->bitmapplans)
                {
                    lfirst(l) = set_plan_refs(root,
                                              (Plan *) lfirst(l),
                                              rtoffset);
                }
            }
            break;
        default:
            elog(ERROR, "unrecognized node type: %d",
                 (int) nodeTag(plan));
            break;
    }

    /*
     * Now recurse into child plans, if any
     *
     * NOTE: it is essential that we recurse into child plans AFTER we set
     * subplan references in this plan's tlist and quals.  If we did the
     * reference-adjustments bottom-up, then we would fail to match this
     * plan's var nodes against the already-modified nodes of the children.
     */
    plan->lefttree = set_plan_refs(root, plan->lefttree, rtoffset);
    plan->righttree = set_plan_refs(root, plan->righttree, rtoffset);

    return plan;
}

/*
 * set_indexonlyscan_references
 *      Do set_plan_references processing on an IndexOnlyScan
 *
 * This is unlike the handling of a plain IndexScan because we have to
 * convert Vars referencing the heap into Vars referencing the index.
 * We can use the fix_upper_expr machinery for that, by working from a
 * targetlist describing the index columns.
 */
static Plan *
set_indexonlyscan_references(PlannerInfo *root,
                             IndexOnlyScan *plan,
                             int rtoffset)
{
    indexed_tlist *index_itlist;

    index_itlist = build_tlist_index(plan->indextlist);

    plan->scan.scanrelid += rtoffset;
    plan->scan.plan.targetlist = (List *)
        fix_upper_expr(root,
                       (Node *) plan->scan.plan.targetlist,
                       index_itlist,
                       INDEX_VAR,
                       rtoffset);
    plan->scan.plan.qual = (List *)
        fix_upper_expr(root,
                       (Node *) plan->scan.plan.qual,
                       index_itlist,
                       INDEX_VAR,
                       rtoffset);
    /* indexqual is already transformed to reference index columns */
    plan->indexqual = fix_scan_list(root, plan->indexqual, rtoffset);
    /* indexorderby is already transformed to reference index columns */
    plan->indexorderby = fix_scan_list(root, plan->indexorderby, rtoffset);
    /* indextlist must NOT be transformed to reference index columns */
    plan->indextlist = fix_scan_list(root, plan->indextlist, rtoffset);

    pfree(index_itlist);

    return (Plan *) plan;
}

/*
 * set_subqueryscan_references
 *      Do set_plan_references processing on a SubqueryScan
 *
 * We try to strip out the SubqueryScan entirely; if we can't, we have
 * to do the normal processing on it.
 */
static Plan *
set_subqueryscan_references(PlannerInfo *root,
                            SubqueryScan *plan,
                            int rtoffset)
{
    RelOptInfo *rel;
    Plan       *result;

    /* Need to look up the subquery's RelOptInfo, since we need its subroot */
    rel = find_base_rel(root, plan->scan.scanrelid);
    Assert(rel->subplan == plan->subplan);

    /* Recursively process the subplan */
    plan->subplan = set_plan_references(rel->subroot, plan->subplan);

    if (trivial_subqueryscan(plan))
    {
        /*
         * We can omit the SubqueryScan node and just pull up the subplan.
         */
        ListCell   *lp,
                   *lc;

        result = plan->subplan;

        /* We have to be sure we don't lose any initplans */
        result->initPlan = list_concat(plan->scan.plan.initPlan,
                                       result->initPlan);

        /*
         * We also have to transfer the SubqueryScan's result-column names
         * into the subplan, else columns sent to client will be improperly
         * labeled if this is the topmost plan level.  Copy the "source
         * column" information too.
         */
        forboth(lp, plan->scan.plan.targetlist, lc, result->targetlist)
        {
            TargetEntry *ptle = (TargetEntry *) lfirst(lp);
            TargetEntry *ctle = (TargetEntry *) lfirst(lc);

            ctle->resname = ptle->resname;
            ctle->resorigtbl = ptle->resorigtbl;
            ctle->resorigcol = ptle->resorigcol;
        }
    }
    else
    {
        /*
         * Keep the SubqueryScan node.  We have to do the processing that
         * set_plan_references would otherwise have done on it.  Notice we do
         * not do set_upper_references() here, because a SubqueryScan will
         * always have been created with correct references to its subplan's
         * outputs to begin with.
         */
        plan->scan.scanrelid += rtoffset;
        plan->scan.plan.targetlist =
            fix_scan_list(root, plan->scan.plan.targetlist, rtoffset);
        plan->scan.plan.qual =
            fix_scan_list(root, plan->scan.plan.qual, rtoffset);

        result = (Plan *) plan;
    }

    return result;
}

/*
 * trivial_subqueryscan
 *      Detect whether a SubqueryScan can be deleted from the plan tree.
 *
 * We can delete it if it has no qual to check and the targetlist just
 * regurgitates the output of the child plan.
 */
static bool
trivial_subqueryscan(SubqueryScan *plan)
{
    int         attrno;
    ListCell   *lp,
               *lc;

    if (plan->scan.plan.qual != NIL)
        return false;

    if (list_length(plan->scan.plan.targetlist) !=
        list_length(plan->subplan->targetlist))
        return false;           /* tlists not same length */

    attrno = 1;
    forboth(lp, plan->scan.plan.targetlist, lc, plan->subplan->targetlist)
    {
        TargetEntry *ptle = (TargetEntry *) lfirst(lp);
        TargetEntry *ctle = (TargetEntry *) lfirst(lc);

        if (ptle->resjunk != ctle->resjunk)
            return false;       /* tlist doesn't match junk status */

        /*
         * We accept either a Var referencing the corresponding element of the
         * subplan tlist, or a Const equaling the subplan element. See
         * generate_setop_tlist() for motivation.
         */
        if (ptle->expr && IsA(ptle->expr, Var))
        {
            Var        *var = (Var *) ptle->expr;

            Assert(var->varno == plan->scan.scanrelid);
            Assert(var->varlevelsup == 0);
            if (var->varattno != attrno)
                return false;   /* out of order */
        }
        else if (ptle->expr && IsA(ptle->expr, Const))
        {
            if (!equal(ptle->expr, ctle->expr))
                return false;
        }
        else
            return false;

        attrno++;
    }

    return true;
}

/*
 * copyVar
 *      Copy a Var node.
 *
 * fix_scan_expr and friends do this enough times that it's worth having
 * a bespoke routine instead of using the generic copyObject() function.
 */
static inline Var *
copyVar(Var *var)
{
    Var        *newvar = (Var *) palloc(sizeof(Var));

    *newvar = *var;
    return newvar;
}

/*
 * fix_expr_common
 *      Do generic set_plan_references processing on an expression node
 *
 * This is code that is common to all variants of expression-fixing.
 * We must look up operator opcode info for OpExpr and related nodes,
 * add OIDs from regclass Const nodes into root->glob->relationOids, and
 * add catalog TIDs for user-defined functions into root->glob->invalItems.
 *
 * We assume it's okay to update opcode info in-place.  So this could possibly
 * scribble on the planner's input data structures, but it's OK.
 */
static void
fix_expr_common(PlannerInfo *root, Node *node)
{
    /* We assume callers won't call us on a NULL pointer */
    if (IsA(node, Aggref))
    {
        record_plan_function_dependency(root,
                                        ((Aggref *) node)->aggfnoid);
    }
    else if (IsA(node, WindowFunc))
    {
        record_plan_function_dependency(root,
                                        ((WindowFunc *) node)->winfnoid);
    }
    else if (IsA(node, FuncExpr))
    {
        record_plan_function_dependency(root,
                                        ((FuncExpr *) node)->funcid);
    }
    else if (IsA(node, OpExpr))
    {
        set_opfuncid((OpExpr *) node);
        record_plan_function_dependency(root,
                                        ((OpExpr *) node)->opfuncid);
    }
    else if (IsA(node, DistinctExpr))
    {
        set_opfuncid((OpExpr *) node);  /* rely on struct equivalence */
        record_plan_function_dependency(root,
                                        ((DistinctExpr *) node)->opfuncid);
    }
    else if (IsA(node, NullIfExpr))
    {
        set_opfuncid((OpExpr *) node);  /* rely on struct equivalence */
        record_plan_function_dependency(root,
                                        ((NullIfExpr *) node)->opfuncid);
    }
    else if (IsA(node, ScalarArrayOpExpr))
    {
        set_sa_opfuncid((ScalarArrayOpExpr *) node);
        record_plan_function_dependency(root,
                                     ((ScalarArrayOpExpr *) node)->opfuncid);
    }
    else if (IsA(node, ArrayCoerceExpr))
    {
        if (OidIsValid(((ArrayCoerceExpr *) node)->elemfuncid))
            record_plan_function_dependency(root,
                                     ((ArrayCoerceExpr *) node)->elemfuncid);
    }
    else if (IsA(node, Const))
    {
        Const      *con = (Const *) node;

        /* Check for regclass reference */
        if (ISREGCLASSCONST(con))
            root->glob->relationOids =
                lappend_oid(root->glob->relationOids,
                            DatumGetObjectId(con->constvalue));
    }
}

/*
 * fix_scan_expr
 *      Do set_plan_references processing on a scan-level expression
 *
 * This consists of incrementing all Vars' varnos by rtoffset,
 * looking up operator opcode info for OpExpr and related nodes,
 * and adding OIDs from regclass Const nodes into root->glob->relationOids.
 */
static Node *
fix_scan_expr(PlannerInfo *root, Node *node, int rtoffset)
{
    fix_scan_expr_context context;

    context.root = root;
    context.rtoffset = rtoffset;

    if (rtoffset != 0 || root->glob->lastPHId != 0)
    {
        return fix_scan_expr_mutator(node, &context);
    }
    else
    {
        /*
         * If rtoffset == 0, we don't need to change any Vars, and if there
         * are no placeholders anywhere we won't need to remove them.  Then
         * it's OK to just scribble on the input node tree instead of copying
         * (since the only change, filling in any unset opfuncid fields, is
         * harmless).  This saves just enough cycles to be noticeable on
         * trivial queries.
         */
        (void) fix_scan_expr_walker(node, &context);
        return node;
    }
}

static Node *
fix_scan_expr_mutator(Node *node, fix_scan_expr_context *context)
{
    if (node == NULL)
        return NULL;
    if (IsA(node, Var))
    {
        Var        *var = copyVar((Var *) node);

        Assert(var->varlevelsup == 0);

        /*
         * We should not see any Vars marked INNER_VAR or OUTER_VAR.  But an
         * indexqual expression could contain INDEX_VAR Vars.
         */
        Assert(var->varno != INNER_VAR);
        Assert(var->varno != OUTER_VAR);
        if (!IS_SPECIAL_VARNO(var->varno))
            var->varno += context->rtoffset;
        if (var->varnoold > 0)
            var->varnoold += context->rtoffset;
        return (Node *) var;
    }
    if (IsA(node, CurrentOfExpr))
    {
        CurrentOfExpr *cexpr = (CurrentOfExpr *) copyObject(node);

        Assert(cexpr->cvarno != INNER_VAR);
        Assert(cexpr->cvarno != OUTER_VAR);
        if (!IS_SPECIAL_VARNO(cexpr->cvarno))
            cexpr->cvarno += context->rtoffset;
        return (Node *) cexpr;
    }
    if (IsA(node, PlaceHolderVar))
    {
        /* At scan level, we should always just evaluate the contained expr */
        PlaceHolderVar *phv = (PlaceHolderVar *) node;

        return fix_scan_expr_mutator((Node *) phv->phexpr, context);
    }
    fix_expr_common(context->root, node);
    return expression_tree_mutator(node, fix_scan_expr_mutator,
                                   (void *) context);
}

static bool
fix_scan_expr_walker(Node *node, fix_scan_expr_context *context)
{
    if (node == NULL)
        return false;
    Assert(!IsA(node, PlaceHolderVar));
    fix_expr_common(context->root, node);
    return expression_tree_walker(node, fix_scan_expr_walker,
                                  (void *) context);
}

/*
 * set_join_references
 *    Modify the target list and quals of a join node to reference its
 *    subplans, by setting the varnos to OUTER_VAR or INNER_VAR and setting
 *    attno values to the result domain number of either the corresponding
 *    outer or inner join tuple item.  Also perform opcode lookup for these
 *    expressions. and add regclass OIDs to root->glob->relationOids.
 */
static void
set_join_references(PlannerInfo *root, Join *join, int rtoffset)
{
    Plan       *outer_plan = join->plan.lefttree;
    Plan       *inner_plan = join->plan.righttree;
    indexed_tlist *outer_itlist;
    indexed_tlist *inner_itlist;

    outer_itlist = build_tlist_index(outer_plan->targetlist);
    inner_itlist = build_tlist_index(inner_plan->targetlist);

    /* All join plans have tlist, qual, and joinqual */
    join->plan.targetlist = fix_join_expr(root,
                                          join->plan.targetlist,
                                          outer_itlist,
                                          inner_itlist,
                                          (Index) 0,
                                          rtoffset);
    join->plan.qual = fix_join_expr(root,
                                    join->plan.qual,
                                    outer_itlist,
                                    inner_itlist,
                                    (Index) 0,
                                    rtoffset);
    join->joinqual = fix_join_expr(root,
                                   join->joinqual,
                                   outer_itlist,
                                   inner_itlist,
                                   (Index) 0,
                                   rtoffset);

    /* Now do join-type-specific stuff */
    if (IsA(join, NestLoop))
    {
        NestLoop   *nl = (NestLoop *) join;
        ListCell   *lc;

        foreach(lc, nl->nestParams)
        {
            NestLoopParam *nlp = (NestLoopParam *) lfirst(lc);

            nlp->paramval = (Var *) fix_upper_expr(root,
                                                   (Node *) nlp->paramval,
                                                   outer_itlist,
                                                   OUTER_VAR,
                                                   rtoffset);
            /* Check we replaced any PlaceHolderVar with simple Var */
            if (!(IsA(nlp->paramval, Var) &&
                  nlp->paramval->varno == OUTER_VAR))
                elog(ERROR, "NestLoopParam was not reduced to a simple Var");
        }
    }
    else if (IsA(join, MergeJoin))
    {
        MergeJoin  *mj = (MergeJoin *) join;

        mj->mergeclauses = fix_join_expr(root,
                                         mj->mergeclauses,
                                         outer_itlist,
                                         inner_itlist,
                                         (Index) 0,
                                         rtoffset);
    }
    else if (IsA(join, HashJoin))
    {
        HashJoin   *hj = (HashJoin *) join;

        hj->hashclauses = fix_join_expr(root,
                                        hj->hashclauses,
                                        outer_itlist,
                                        inner_itlist,
                                        (Index) 0,
                                        rtoffset);
    }

    pfree(outer_itlist);
    pfree(inner_itlist);
}

/*
 * set_upper_references
 *    Update the targetlist and quals of an upper-level plan node
 *    to refer to the tuples returned by its lefttree subplan.
 *    Also perform opcode lookup for these expressions, and
 *    add regclass OIDs to root->glob->relationOids.
 *
 * This is used for single-input plan types like Agg, Group, Result.
 *
 * In most cases, we have to match up individual Vars in the tlist and
 * qual expressions with elements of the subplan's tlist (which was
 * generated by flatten_tlist() from these selfsame expressions, so it
 * should have all the required variables).  There is an important exception,
 * however: GROUP BY and ORDER BY expressions will have been pushed into the
 * subplan tlist unflattened.  If these values are also needed in the output
 * then we want to reference the subplan tlist element rather than recomputing
 * the expression.
 */
static void
set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
{
    Plan       *subplan = plan->lefttree;
    indexed_tlist *subplan_itlist;
    List       *output_targetlist;
    ListCell   *l;

    subplan_itlist = build_tlist_index(subplan->targetlist);

    output_targetlist = NIL;
    foreach(l, plan->targetlist)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(l);
        Node       *newexpr;

        /* If it's a non-Var sort/group item, first try to match by sortref */
        if (tle->ressortgroupref != 0 && !IsA(tle->expr, Var))
        {
            newexpr = (Node *)
                search_indexed_tlist_for_sortgroupref((Node *) tle->expr,
                                                      tle->ressortgroupref,
                                                      subplan_itlist,
                                                      OUTER_VAR);
            if (!newexpr)
                newexpr = fix_upper_expr(root,
                                         (Node *) tle->expr,
                                         subplan_itlist,
                                         OUTER_VAR,
                                         rtoffset);
        }
        else
            newexpr = fix_upper_expr(root,
                                     (Node *) tle->expr,
                                     subplan_itlist,
                                     OUTER_VAR,
                                     rtoffset);
        tle = flatCopyTargetEntry(tle);
        tle->expr = (Expr *) newexpr;
        output_targetlist = lappend(output_targetlist, tle);
    }
    plan->targetlist = output_targetlist;

    plan->qual = (List *)
        fix_upper_expr(root,
                       (Node *) plan->qual,
                       subplan_itlist,
                       OUTER_VAR,
                       rtoffset);

    pfree(subplan_itlist);
}

/*
 * set_dummy_tlist_references
 *    Replace the targetlist of an upper-level plan node with a simple
 *    list of OUTER_VAR references to its child.
 *
 * This is used for plan types like Sort and Append that don't evaluate
 * their targetlists.  Although the executor doesn't care at all what's in
 * the tlist, EXPLAIN needs it to be realistic.
 *
 * Note: we could almost use set_upper_references() here, but it fails for
 * Append for lack of a lefttree subplan.  Single-purpose code is faster
 * anyway.
 */
static void
set_dummy_tlist_references(Plan *plan, int rtoffset)
{
    List       *output_targetlist;
    ListCell   *l;

    output_targetlist = NIL;
    foreach(l, plan->targetlist)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(l);
        Var        *oldvar = (Var *) tle->expr;
        Var        *newvar;

        newvar = makeVar(OUTER_VAR,
                         tle->resno,
                         exprType((Node *) oldvar),
                         exprTypmod((Node *) oldvar),
                         exprCollation((Node *) oldvar),
                         0);
        if (IsA(oldvar, Var))
        {
            newvar->varnoold = oldvar->varno + rtoffset;
            newvar->varoattno = oldvar->varattno;
        }
        else
        {
            newvar->varnoold = 0;       /* wasn't ever a plain Var */
            newvar->varoattno = 0;
        }

        tle = flatCopyTargetEntry(tle);
        tle->expr = (Expr *) newvar;
        output_targetlist = lappend(output_targetlist, tle);
    }
    plan->targetlist = output_targetlist;

    /* We don't touch plan->qual here */
}


/*
 * build_tlist_index --- build an index data structure for a child tlist
 *
 * In most cases, subplan tlists will be "flat" tlists with only Vars,
 * so we try to optimize that case by extracting information about Vars
 * in advance.  Matching a parent tlist to a child is still an O(N^2)
 * operation, but at least with a much smaller constant factor than plain
 * tlist_member() searches.
 *
 * The result of this function is an indexed_tlist struct to pass to
 * search_indexed_tlist_for_var() or search_indexed_tlist_for_non_var().
 * When done, the indexed_tlist may be freed with a single pfree().
 */
static indexed_tlist *
build_tlist_index(List *tlist)
{
    indexed_tlist *itlist;
    tlist_vinfo *vinfo;
    ListCell   *l;

    /* Create data structure with enough slots for all tlist entries */
    itlist = (indexed_tlist *)
        palloc(offsetof(indexed_tlist, vars) +
               list_length(tlist) * sizeof(tlist_vinfo));

    itlist->tlist = tlist;
    itlist->has_ph_vars = false;
    itlist->has_non_vars = false;

    /* Find the Vars and fill in the index array */
    vinfo = itlist->vars;
    foreach(l, tlist)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(l);

        if (tle->expr && IsA(tle->expr, Var))
        {
            Var        *var = (Var *) tle->expr;

            vinfo->varno = var->varno;
            vinfo->varattno = var->varattno;
            vinfo->resno = tle->resno;
            vinfo++;
        }
        else if (tle->expr && IsA(tle->expr, PlaceHolderVar))
            itlist->has_ph_vars = true;
        else
            itlist->has_non_vars = true;
    }

    itlist->num_vars = (vinfo - itlist->vars);

    return itlist;
}

/*
 * build_tlist_index_other_vars --- build a restricted tlist index
 *
 * This is like build_tlist_index, but we only index tlist entries that
 * are Vars belonging to some rel other than the one specified.  We will set
 * has_ph_vars (allowing PlaceHolderVars to be matched), but not has_non_vars
 * (so nothing other than Vars and PlaceHolderVars can be matched).
 */
static indexed_tlist *
build_tlist_index_other_vars(List *tlist, Index ignore_rel)
{
    indexed_tlist *itlist;
    tlist_vinfo *vinfo;
    ListCell   *l;

    /* Create data structure with enough slots for all tlist entries */
    itlist = (indexed_tlist *)
        palloc(offsetof(indexed_tlist, vars) +
               list_length(tlist) * sizeof(tlist_vinfo));

    itlist->tlist = tlist;
    itlist->has_ph_vars = false;
    itlist->has_non_vars = false;

    /* Find the desired Vars and fill in the index array */
    vinfo = itlist->vars;
    foreach(l, tlist)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(l);

        if (tle->expr && IsA(tle->expr, Var))
        {
            Var        *var = (Var *) tle->expr;

            if (var->varno != ignore_rel)
            {
                vinfo->varno = var->varno;
                vinfo->varattno = var->varattno;
                vinfo->resno = tle->resno;
                vinfo++;
            }
        }
        else if (tle->expr && IsA(tle->expr, PlaceHolderVar))
            itlist->has_ph_vars = true;
    }

    itlist->num_vars = (vinfo - itlist->vars);

    return itlist;
}

/*
 * search_indexed_tlist_for_var --- find a Var in an indexed tlist
 *
 * If a match is found, return a copy of the given Var with suitably
 * modified varno/varattno (to wit, newvarno and the resno of the TLE entry).
 * Also ensure that varnoold is incremented by rtoffset.
 * If no match, return NULL.
 */
static Var *
search_indexed_tlist_for_var(Var *var, indexed_tlist *itlist,
                             Index newvarno, int rtoffset)
{
    Index       varno = var->varno;
    AttrNumber  varattno = var->varattno;
    tlist_vinfo *vinfo;
    int         i;

    vinfo = itlist->vars;
    i = itlist->num_vars;
    while (i-- > 0)
    {
        if (vinfo->varno == varno && vinfo->varattno == varattno)
        {
            /* Found a match */
            Var        *newvar = copyVar(var);

            newvar->varno = newvarno;
            newvar->varattno = vinfo->resno;
            if (newvar->varnoold > 0)
                newvar->varnoold += rtoffset;
            return newvar;
        }
        vinfo++;
    }
    return NULL;                /* no match */
}

/*
 * search_indexed_tlist_for_non_var --- find a non-Var in an indexed tlist
 *
 * If a match is found, return a Var constructed to reference the tlist item.
 * If no match, return NULL.
 *
 * NOTE: it is a waste of time to call this unless itlist->has_ph_vars or
 * itlist->has_non_vars
 */
static Var *
search_indexed_tlist_for_non_var(Node *node,
                                 indexed_tlist *itlist, Index newvarno)
{
    TargetEntry *tle;

    tle = tlist_member(node, itlist->tlist);
    if (tle)
    {
        /* Found a matching subplan output expression */
        Var        *newvar;

        newvar = makeVarFromTargetEntry(newvarno, tle);
        newvar->varnoold = 0;   /* wasn't ever a plain Var */
        newvar->varoattno = 0;
        return newvar;
    }
    return NULL;                /* no match */
}

/*
 * search_indexed_tlist_for_sortgroupref --- find a sort/group expression
 *      (which is assumed not to be just a Var)
 *
 * If a match is found, return a Var constructed to reference the tlist item.
 * If no match, return NULL.
 *
 * This is needed to ensure that we select the right subplan TLE in cases
 * where there are multiple textually-equal()-but-volatile sort expressions.
 * And it's also faster than search_indexed_tlist_for_non_var.
 */
static Var *
search_indexed_tlist_for_sortgroupref(Node *node,
                                      Index sortgroupref,
                                      indexed_tlist *itlist,
                                      Index newvarno)
{
    ListCell   *lc;

    foreach(lc, itlist->tlist)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(lc);

        /* The equal() check should be redundant, but let's be paranoid */
        if (tle->ressortgroupref == sortgroupref &&
            equal(node, tle->expr))
        {
            /* Found a matching subplan output expression */
            Var        *newvar;

            newvar = makeVarFromTargetEntry(newvarno, tle);
            newvar->varnoold = 0;       /* wasn't ever a plain Var */
            newvar->varoattno = 0;
            return newvar;
        }
    }
    return NULL;                /* no match */
}

/*
 * fix_join_expr
 *     Create a new set of targetlist entries or join qual clauses by
 *     changing the varno/varattno values of variables in the clauses
 *     to reference target list values from the outer and inner join
 *     relation target lists.  Also perform opcode lookup and add
 *     regclass OIDs to root->glob->relationOids.
 *
 * This is used in two different scenarios: a normal join clause, where all
 * the Vars in the clause *must* be replaced by OUTER_VAR or INNER_VAR
 * references; and a RETURNING clause, which may contain both Vars of the
 * target relation and Vars of other relations.  In the latter case we want
 * to replace the other-relation Vars by OUTER_VAR references, while leaving
 * target Vars alone.
 *
 * For a normal join, acceptable_rel should be zero so that any failure to
 * match a Var will be reported as an error.  For the RETURNING case, pass
 * inner_itlist = NULL and acceptable_rel = the ID of the target relation.
 *
 * 'clauses' is the targetlist or list of join clauses
 * 'outer_itlist' is the indexed target list of the outer join relation
 * 'inner_itlist' is the indexed target list of the inner join relation,
 *      or NULL
 * 'acceptable_rel' is either zero or the rangetable index of a relation
 *      whose Vars may appear in the clause without provoking an error
 * 'rtoffset': how much to increment varnoold by
 *
 * Returns the new expression tree.  The original clause structure is
 * not modified.
 */
static List *
fix_join_expr(PlannerInfo *root,
              List *clauses,
              indexed_tlist *outer_itlist,
              indexed_tlist *inner_itlist,
              Index acceptable_rel,
              int rtoffset)
{
    fix_join_expr_context context;

    context.root = root;
    context.outer_itlist = outer_itlist;
    context.inner_itlist = inner_itlist;
    context.acceptable_rel = acceptable_rel;
    context.rtoffset = rtoffset;
    return (List *) fix_join_expr_mutator((Node *) clauses, &context);
}

static Node *
fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
{
    Var        *newvar;

    if (node == NULL)
        return NULL;
    if (IsA(node, Var))
    {
        Var        *var = (Var *) node;

        /* First look for the var in the input tlists */
        newvar = search_indexed_tlist_for_var(var,
                                              context->outer_itlist,
                                              OUTER_VAR,
                                              context->rtoffset);
        if (newvar)
            return (Node *) newvar;
        if (context->inner_itlist)
        {
            newvar = search_indexed_tlist_for_var(var,
                                                  context->inner_itlist,
                                                  INNER_VAR,
                                                  context->rtoffset);
            if (newvar)
                return (Node *) newvar;
        }

        /* If it's for acceptable_rel, adjust and return it */
        if (var->varno == context->acceptable_rel)
        {
            var = copyVar(var);
            var->varno += context->rtoffset;
            if (var->varnoold > 0)
                var->varnoold += context->rtoffset;
            return (Node *) var;
        }

        /* No referent found for Var */
        elog(ERROR, "variable not found in subplan target lists");
    }
    if (IsA(node, PlaceHolderVar))
    {
        PlaceHolderVar *phv = (PlaceHolderVar *) node;

        /* See if the PlaceHolderVar has bubbled up from a lower plan node */
        if (context->outer_itlist->has_ph_vars)
        {
            newvar = search_indexed_tlist_for_non_var((Node *) phv,
                                                      context->outer_itlist,
                                                      OUTER_VAR);
            if (newvar)
                return (Node *) newvar;
        }
        if (context->inner_itlist && context->inner_itlist->has_ph_vars)
        {
            newvar = search_indexed_tlist_for_non_var((Node *) phv,
                                                      context->inner_itlist,
                                                      INNER_VAR);
            if (newvar)
                return (Node *) newvar;
        }

        /* If not supplied by input plans, evaluate the contained expr */
        return fix_join_expr_mutator((Node *) phv->phexpr, context);
    }
    /* Try matching more complex expressions too, if tlists have any */
    if (context->outer_itlist->has_non_vars)
    {
        newvar = search_indexed_tlist_for_non_var(node,
                                                  context->outer_itlist,
                                                  OUTER_VAR);
        if (newvar)
            return (Node *) newvar;
    }
    if (context->inner_itlist && context->inner_itlist->has_non_vars)
    {
        newvar = search_indexed_tlist_for_non_var(node,
                                                  context->inner_itlist,
                                                  INNER_VAR);
        if (newvar)
            return (Node *) newvar;
    }
    fix_expr_common(context->root, node);
    return expression_tree_mutator(node,
                                   fix_join_expr_mutator,
                                   (void *) context);
}

/*
 * fix_upper_expr
 *      Modifies an expression tree so that all Var nodes reference outputs
 *      of a subplan.  Also performs opcode lookup, and adds regclass OIDs to
 *      root->glob->relationOids.
 *
 * This is used to fix up target and qual expressions of non-join upper-level
 * plan nodes, as well as index-only scan nodes.
 *
 * An error is raised if no matching var can be found in the subplan tlist
 * --- so this routine should only be applied to nodes whose subplans'
 * targetlists were generated via flatten_tlist() or some such method.
 *
 * If itlist->has_non_vars is true, then we try to match whole subexpressions
 * against elements of the subplan tlist, so that we can avoid recomputing
 * expressions that were already computed by the subplan.  (This is relatively
 * expensive, so we don't want to try it in the common case where the
 * subplan tlist is just a flattened list of Vars.)
 *
 * 'node': the tree to be fixed (a target item or qual)
 * 'subplan_itlist': indexed target list for subplan (or index)
 * 'newvarno': varno to use for Vars referencing tlist elements
 * 'rtoffset': how much to increment varnoold by
 *
 * The resulting tree is a copy of the original in which all Var nodes have
 * varno = newvarno, varattno = resno of corresponding targetlist element.
 * The original tree is not modified.
 */
static Node *
fix_upper_expr(PlannerInfo *root,
               Node *node,
               indexed_tlist *subplan_itlist,
               Index newvarno,
               int rtoffset)
{
    fix_upper_expr_context context;

    context.root = root;
    context.subplan_itlist = subplan_itlist;
    context.newvarno = newvarno;
    context.rtoffset = rtoffset;
    return fix_upper_expr_mutator(node, &context);
}

static Node *
fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
{
    Var        *newvar;

    if (node == NULL)
        return NULL;
    if (IsA(node, Var))
    {
        Var        *var = (Var *) node;

        newvar = search_indexed_tlist_for_var(var,
                                              context->subplan_itlist,
                                              context->newvarno,
                                              context->rtoffset);
        if (!newvar)
            elog(ERROR, "variable not found in subplan target list");
        return (Node *) newvar;
    }
    if (IsA(node, PlaceHolderVar))
    {
        PlaceHolderVar *phv = (PlaceHolderVar *) node;

        /* See if the PlaceHolderVar has bubbled up from a lower plan node */
        if (context->subplan_itlist->has_ph_vars)
        {
            newvar = search_indexed_tlist_for_non_var((Node *) phv,
                                                      context->subplan_itlist,
                                                      context->newvarno);
            if (newvar)
                return (Node *) newvar;
        }
        /* If not supplied by input plan, evaluate the contained expr */
        return fix_upper_expr_mutator((Node *) phv->phexpr, context);
    }
    /* Try matching more complex expressions too, if tlist has any */
    if (context->subplan_itlist->has_non_vars)
    {
        newvar = search_indexed_tlist_for_non_var(node,
                                                  context->subplan_itlist,
                                                  context->newvarno);
        if (newvar)
            return (Node *) newvar;
    }
    fix_expr_common(context->root, node);
    return expression_tree_mutator(node,
                                   fix_upper_expr_mutator,
                                   (void *) context);
}

/*
 * set_returning_clause_references
 *      Perform setrefs.c's work on a RETURNING targetlist
 *
 * If the query involves more than just the result table, we have to
 * adjust any Vars that refer to other tables to reference junk tlist
 * entries in the top subplan's targetlist.  Vars referencing the result
 * table should be left alone, however (the executor will evaluate them
 * using the actual heap tuple, after firing triggers if any).  In the
 * adjusted RETURNING list, result-table Vars will have their original
 * varno (plus rtoffset), but Vars for other rels will have varno OUTER_VAR.
 *
 * We also must perform opcode lookup and add regclass OIDs to
 * root->glob->relationOids.
 *
 * 'rlist': the RETURNING targetlist to be fixed
 * 'topplan': the top subplan node that will be just below the ModifyTable
 *      node (note it's not yet passed through set_plan_refs)
 * 'resultRelation': RT index of the associated result relation
 * 'rtoffset': how much to increment varnos by
 *
 * Note: the given 'root' is for the parent query level, not the 'topplan'.
 * This does not matter currently since we only access the dependency-item
 * lists in root->glob, but it would need some hacking if we wanted a root
 * that actually matches the subplan.
 *
 * Note: resultRelation is not yet adjusted by rtoffset.
 */
static List *
set_returning_clause_references(PlannerInfo *root,
                                List *rlist,
                                Plan *topplan,
                                Index resultRelation,
                                int rtoffset)
{
    indexed_tlist *itlist;

    /*
     * We can perform the desired Var fixup by abusing the fix_join_expr
     * machinery that formerly handled inner indexscan fixup.  We search the
     * top plan's targetlist for Vars of non-result relations, and use
     * fix_join_expr to convert RETURNING Vars into references to those tlist
     * entries, while leaving result-rel Vars as-is.
     *
     * PlaceHolderVars will also be sought in the targetlist, but no
     * more-complex expressions will be.  Note that it is not possible for a
     * PlaceHolderVar to refer to the result relation, since the result is
     * never below an outer join.  If that case could happen, we'd have to be
     * prepared to pick apart the PlaceHolderVar and evaluate its contained
     * expression instead.
     */
    itlist = build_tlist_index_other_vars(topplan->targetlist, resultRelation);

    rlist = fix_join_expr(root,
                          rlist,
                          itlist,
                          NULL,
                          resultRelation,
                          rtoffset);

    pfree(itlist);

    return rlist;
}

/*****************************************************************************
 *                  OPERATOR REGPROC LOOKUP
 *****************************************************************************/

/*
 * fix_opfuncids
 *    Calculate opfuncid field from opno for each OpExpr node in given tree.
 *    The given tree can be anything expression_tree_walker handles.
 *
 * The argument is modified in-place.  (This is OK since we'd want the
 * same change for any node, even if it gets visited more than once due to
 * shared structure.)
 */
void
fix_opfuncids(Node *node)
{
    /* This tree walk requires no special setup, so away we go... */
    fix_opfuncids_walker(node, NULL);
}

static bool
fix_opfuncids_walker(Node *node, void *context)
{
    if (node == NULL)
        return false;
    if (IsA(node, OpExpr))
        set_opfuncid((OpExpr *) node);
    else if (IsA(node, DistinctExpr))
        set_opfuncid((OpExpr *) node);  /* rely on struct equivalence */
    else if (IsA(node, NullIfExpr))
        set_opfuncid((OpExpr *) node);  /* rely on struct equivalence */
    else if (IsA(node, ScalarArrayOpExpr))
        set_sa_opfuncid((ScalarArrayOpExpr *) node);
    return expression_tree_walker(node, fix_opfuncids_walker, context);
}

/*
 * set_opfuncid
 *      Set the opfuncid (procedure OID) in an OpExpr node,
 *      if it hasn't been set already.
 *
 * Because of struct equivalence, this can also be used for
 * DistinctExpr and NullIfExpr nodes.
 */
void
set_opfuncid(OpExpr *opexpr)
{
    if (opexpr->opfuncid == InvalidOid)
        opexpr->opfuncid = get_opcode(opexpr->opno);
}

/*
 * set_sa_opfuncid
 *      As above, for ScalarArrayOpExpr nodes.
 */
void
set_sa_opfuncid(ScalarArrayOpExpr *opexpr)
{
    if (opexpr->opfuncid == InvalidOid)
        opexpr->opfuncid = get_opcode(opexpr->opno);
}

/*****************************************************************************
 *                  QUERY DEPENDENCY MANAGEMENT
 *****************************************************************************/

/*
 * record_plan_function_dependency
 *      Mark the current plan as depending on a particular function.
 *
 * This is exported so that the function-inlining code can record a
 * dependency on a function that it's removed from the plan tree.
 */
void
record_plan_function_dependency(PlannerInfo *root, Oid funcid)
{
    /*
     * For performance reasons, we don't bother to track built-in functions;
     * we just assume they'll never change (or at least not in ways that'd
     * invalidate plans using them).  For this purpose we can consider a
     * built-in function to be one with OID less than FirstBootstrapObjectId.
     * Note that the OID generator guarantees never to generate such an OID
     * after startup, even at OID wraparound.
     */
    if (funcid >= (Oid) FirstBootstrapObjectId)
    {
        PlanInvalItem *inval_item = makeNode(PlanInvalItem);

        /*
         * It would work to use any syscache on pg_proc, but the easiest is
         * PROCOID since we already have the function's OID at hand.  Note
         * that plancache.c knows we use PROCOID.
         */
        inval_item->cacheId = PROCOID;
        inval_item->hashValue = GetSysCacheHashValue1(PROCOID,
                                                   ObjectIdGetDatum(funcid));

        root->glob->invalItems = lappend(root->glob->invalItems, inval_item);
    }
}

/*
 * extract_query_dependencies
 *      Given a not-yet-planned query or queries (i.e. a Query node or list
 *      of Query nodes), extract dependencies just as set_plan_references
 *      would do.
 *
 * This is needed by plancache.c to handle invalidation of cached unplanned
 * queries.
 */
void
extract_query_dependencies(Node *query,
                           List **relationOids,
                           List **invalItems)
{
    PlannerGlobal glob;
    PlannerInfo root;

    /* Make up dummy planner state so we can use this module's machinery */
    MemSet(&glob, 0, sizeof(glob));
    glob.type = T_PlannerGlobal;
    glob.relationOids = NIL;
    glob.invalItems = NIL;

    MemSet(&root, 0, sizeof(root));
    root.type = T_PlannerInfo;
    root.glob = &glob;

    (void) extract_query_dependencies_walker(query, &root);

    *relationOids = glob.relationOids;
    *invalItems = glob.invalItems;
}

static bool
extract_query_dependencies_walker(Node *node, PlannerInfo *context)
{
    if (node == NULL)
        return false;
    Assert(!IsA(node, PlaceHolderVar));
    /* Extract function dependencies and check for regclass Consts */
    fix_expr_common(context, node);
    if (IsA(node, Query))
    {
        Query      *query = (Query *) node;
        ListCell   *lc;

        if (query->commandType == CMD_UTILITY)
        {
            /*
             * Ignore utility statements, except those (such as EXPLAIN) that
             * contain a parsed-but-not-planned query.
             */
            query = UtilityContainsQuery(query->utilityStmt);
            if (query == NULL)
                return false;
        }

        /* Collect relation OIDs in this Query's rtable */
        foreach(lc, query->rtable)
        {
            RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);

            if (rte->rtekind == RTE_RELATION)
                context->glob->relationOids =
                    lappend_oid(context->glob->relationOids, rte->relid);
        }

        /* And recurse into the query's subexpressions */
        return query_tree_walker(query, extract_query_dependencies_walker,
                                 (void *) context, 0);
    }
    return expression_tree_walker(node, extract_query_dependencies_walker,
                                  (void *) context);
}