[postgresql] / src / backend / optimizer / path / allpaths.c

/*-------------------------------------------------------------------------
 *
 * allpaths.c
 *        Routines to find possible search paths for processing a query
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.127 2005/04/21 19:18:12 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#ifdef OPTIMIZER_DEBUG
#include "nodes/print.h"
#endif
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/plancat.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "parser/parse_clause.h"
#include "parser/parse_expr.h"
#include "rewrite/rewriteManip.h"


/* These parameters are set by GUC */
bool            enable_geqo = false;    /* just in case GUC doesn't set it */
int                     geqo_threshold;


static void set_base_rel_pathlists(Query *root);
static void set_plain_rel_pathlist(Query *root, RelOptInfo *rel,
                                           RangeTblEntry *rte);
static void set_inherited_rel_pathlist(Query *root, RelOptInfo *rel,
                                                   Index rti, RangeTblEntry *rte,
                                                   List *inheritlist);
static void set_subquery_pathlist(Query *root, RelOptInfo *rel,
                                          Index rti, RangeTblEntry *rte);
static void set_function_pathlist(Query *root, RelOptInfo *rel,
                                          RangeTblEntry *rte);
static RelOptInfo *make_one_rel_by_joins(Query *root, int levels_needed,
                                          List *initial_rels);
static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery,
                                                  bool *differentTypes);
static bool recurse_pushdown_safe(Node *setOp, Query *topquery,
                                          bool *differentTypes);
static void compare_tlist_datatypes(List *tlist, List *colTypes,
                                                bool *differentTypes);
static bool qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
                                          bool *differentTypes);
static void subquery_push_qual(Query *subquery, List *rtable,
                                   Index rti, Node *qual);
static void recurse_push_qual(Node *setOp, Query *topquery,
                                  List *rtable, Index rti, Node *qual);


/*
 * make_one_rel
 *        Finds all possible access paths for executing a query, returning a
 *        single rel that represents the join of all base rels in the query.
 */
RelOptInfo *
make_one_rel(Query *root)
{
        RelOptInfo *rel;

        /*
         * Generate access paths for the base rels.
         */
        set_base_rel_pathlists(root);

        /*
         * Generate access paths for the entire join tree.
         */
        Assert(root->jointree != NULL && IsA(root->jointree, FromExpr));

        rel = make_fromexpr_rel(root, root->jointree);

        /*
         * The result should join all the query's base rels.
         */
        Assert(bms_num_members(rel->relids) == list_length(root->base_rel_list));

        return rel;
}

/*
 * set_base_rel_pathlists
 *        Finds all paths available for scanning each base-relation entry.
 *        Sequential scan and any available indices are considered.
 *        Each useful path is attached to its relation's 'pathlist' field.
 */
static void
set_base_rel_pathlists(Query *root)
{
        ListCell   *l;

        foreach(l, root->base_rel_list)
        {
                RelOptInfo *rel = (RelOptInfo *) lfirst(l);
                Index           rti = rel->relid;
                RangeTblEntry *rte;
                List       *inheritlist;

                Assert(rti > 0);                /* better be base rel */
                rte = rt_fetch(rti, root->rtable);

                if (rel->rtekind == RTE_SUBQUERY)
                {
                        /* Subquery --- generate a separate plan for it */
                        set_subquery_pathlist(root, rel, rti, rte);
                }
                else if (rel->rtekind == RTE_FUNCTION)
                {
                        /* RangeFunction --- generate a separate plan for it */
                        set_function_pathlist(root, rel, rte);
                }
                else if ((inheritlist = expand_inherited_rtentry(root, rti)) != NIL)
                {
                        /* Relation is root of an inheritance tree, process specially */
                        set_inherited_rel_pathlist(root, rel, rti, rte, inheritlist);
                }
                else
                {
                        /* Plain relation */
                        set_plain_rel_pathlist(root, rel, rte);
                }

#ifdef OPTIMIZER_DEBUG
                debug_print_rel(root, rel);
#endif
        }
}

/*
 * set_plain_rel_pathlist
 *        Build access paths for a plain relation (no subquery, no inheritance)
 */
static void
set_plain_rel_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte)
{
        /* Mark rel with estimated output rows, width, etc */
        set_baserel_size_estimates(root, rel);

        /* Test any partial indexes of rel for applicability */
        check_partial_indexes(root, rel);

        /*
         * Check to see if we can extract any restriction conditions from join
         * quals that are OR-of-AND structures.  If so, add them to the rel's
         * restriction list, and recompute the size estimates.
         */
        if (create_or_index_quals(root, rel))
                set_baserel_size_estimates(root, rel);

        /*
         * Generate paths and add them to the rel's pathlist.
         *
         * Note: add_path() will discard any paths that are dominated by another
         * available path, keeping only those paths that are superior along at
         * least one dimension of cost or sortedness.
         */

        /* Consider sequential scan */
        add_path(rel, create_seqscan_path(root, rel));

        /* Consider TID scans */
        create_tidscan_paths(root, rel);

        /* Consider index paths for both simple and OR index clauses */
        create_index_paths(root, rel);
        create_or_index_paths(root, rel);

        /* Now find the cheapest of the paths for this rel */
        set_cheapest(rel);
}

/*
 * set_inherited_rel_pathlist
 *        Build access paths for a inheritance tree rooted at rel
 *
 * inheritlist is a list of RT indexes of all tables in the inheritance tree,
 * including a duplicate of the parent itself.  Note we will not come here
 * unless there's at least one child in addition to the parent.
 *
 * NOTE: the passed-in rel and RTE will henceforth represent the appended
 * result of the whole inheritance tree.  The members of inheritlist represent
 * the individual tables --- in particular, the inheritlist member that is a
 * duplicate of the parent RTE represents the parent table alone.
 * We will generate plans to scan the individual tables that refer to
 * the inheritlist RTEs, whereas Vars elsewhere in the plan tree that
 * refer to the original RTE are taken to refer to the append output.
 * In particular, this means we have separate RelOptInfos for the parent
 * table and for the append output, which is a good thing because they're
 * not the same size.
 */
static void
set_inherited_rel_pathlist(Query *root, RelOptInfo *rel,
                                                   Index rti, RangeTblEntry *rte,
                                                   List *inheritlist)
{
        int                     parentRTindex = rti;
        Oid                     parentOID = rte->relid;
        List       *subpaths = NIL;
        ListCell   *il;

        /*
         * XXX for now, can't handle inherited expansion of FOR UPDATE; can we
         * do better?
         */
        if (list_member_int(root->rowMarks, parentRTindex))
                ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("SELECT FOR UPDATE is not supported for inheritance queries")));

        /*
         * Initialize to compute size estimates for whole inheritance tree
         */
        rel->rows = 0;
        rel->width = 0;

        /*
         * Generate access paths for each table in the tree (parent AND
         * children), and pick the cheapest path for each table.
         */
        foreach(il, inheritlist)
        {
                int                     childRTindex = lfirst_int(il);
                RangeTblEntry *childrte;
                Oid                     childOID;
                RelOptInfo *childrel;
                ListCell   *parentvars;
                ListCell   *childvars;

                childrte = rt_fetch(childRTindex, root->rtable);
                childOID = childrte->relid;

                /*
                 * Make a RelOptInfo for the child so we can do planning.  Do NOT
                 * attach the RelOptInfo to the query's base_rel_list, however,
                 * since the child is not part of the main join tree.  Instead,
                 * the child RelOptInfo is added to other_rel_list.
                 */
                childrel = build_other_rel(root, childRTindex);

                /*
                 * Copy the parent's targetlist and restriction quals to the
                 * child, with attribute-number adjustment as needed.  We don't
                 * bother to copy the join quals, since we can't do any joining of
                 * the individual tables.  Also, we just zap attr_needed rather
                 * than trying to adjust it; it won't be looked at in the child.
                 */
                childrel->reltargetlist = (List *)
                        adjust_inherited_attrs((Node *) rel->reltargetlist,
                                                                   parentRTindex,
                                                                   parentOID,
                                                                   childRTindex,
                                                                   childOID);
                childrel->attr_needed = NULL;
                childrel->baserestrictinfo = (List *)
                        adjust_inherited_attrs((Node *) rel->baserestrictinfo,
                                                                   parentRTindex,
                                                                   parentOID,
                                                                   childRTindex,
                                                                   childOID);

                /*
                 * Now compute child access paths, and save the cheapest.
                 */
                set_plain_rel_pathlist(root, childrel, childrte);

                subpaths = lappend(subpaths, childrel->cheapest_total_path);

                /*
                 * Propagate size information from the child back to the parent.
                 * For simplicity, we use the largest widths from any child as the
                 * parent estimates.
                 */
                rel->rows += childrel->rows;
                if (childrel->width > rel->width)
                        rel->width = childrel->width;

                forboth(parentvars, rel->reltargetlist,
                                childvars, childrel->reltargetlist)
                {
                        Var                *parentvar = (Var *) lfirst(parentvars);
                        Var                *childvar = (Var *) lfirst(childvars);

                        if (IsA(parentvar, Var) &&IsA(childvar, Var))
                        {
                                int                     pndx = parentvar->varattno - rel->min_attr;
                                int                     cndx = childvar->varattno - childrel->min_attr;

                                if (childrel->attr_widths[cndx] > rel->attr_widths[pndx])
                                        rel->attr_widths[pndx] = childrel->attr_widths[cndx];
                        }
                }
        }

        /*
         * Finally, build Append path and install it as the only access path
         * for the parent rel.
         */
        add_path(rel, (Path *) create_append_path(rel, subpaths));

        /* Select cheapest path (pretty easy in this case...) */
        set_cheapest(rel);
}

/*
 * set_subquery_pathlist
 *              Build the (single) access path for a subquery RTE
 */
static void
set_subquery_pathlist(Query *root, RelOptInfo *rel,
                                          Index rti, RangeTblEntry *rte)
{
        Query      *subquery = rte->subquery;
        bool       *differentTypes;
        List       *pathkeys;

        /* We need a workspace for keeping track of set-op type coercions */
        differentTypes = (bool *)
                palloc0((list_length(subquery->targetList) + 1) * sizeof(bool));

        /*
         * If there are any restriction clauses that have been attached to the
         * subquery relation, consider pushing them down to become WHERE or
         * HAVING quals of the subquery itself.  This transformation is useful
         * because it may allow us to generate a better plan for the subquery
         * than evaluating all the subquery output rows and then filtering them.
         *
         * There are several cases where we cannot push down clauses.
         * Restrictions involving the subquery are checked by
         * subquery_is_pushdown_safe().  Restrictions on individual clauses
         * are checked by qual_is_pushdown_safe().
         *
         * Non-pushed-down clauses will get evaluated as qpquals of the
         * SubqueryScan node.
         *
         * XXX Are there any cases where we want to make a policy decision not to
         * push down a pushable qual, because it'd result in a worse plan?
         */
        if (rel->baserestrictinfo != NIL &&
                subquery_is_pushdown_safe(subquery, subquery, differentTypes))
        {
                /* OK to consider pushing down individual quals */
                List       *upperrestrictlist = NIL;
                ListCell   *l;

                foreach(l, rel->baserestrictinfo)
                {
                        RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
                        Node       *clause = (Node *) rinfo->clause;

                        if (qual_is_pushdown_safe(subquery, rti, clause, differentTypes))
                        {
                                /* Push it down */
                                subquery_push_qual(subquery, root->rtable, rti, clause);
                        }
                        else
                        {
                                /* Keep it in the upper query */
                                upperrestrictlist = lappend(upperrestrictlist, rinfo);
                        }
                }
                rel->baserestrictinfo = upperrestrictlist;
        }

        pfree(differentTypes);

        /* Generate the plan for the subquery */
        rel->subplan = subquery_planner(subquery, 0.0 /* default case */ );

        /* Copy number of output rows from subplan */
        rel->tuples = rel->subplan->plan_rows;

        /* Mark rel with estimated output rows, width, etc */
        set_baserel_size_estimates(root, rel);

        /* Convert subquery pathkeys to outer representation */
        pathkeys = build_subquery_pathkeys(root, rel, subquery);

        /* Generate appropriate path */
        add_path(rel, create_subqueryscan_path(rel, pathkeys));

        /* Select cheapest path (pretty easy in this case...) */
        set_cheapest(rel);
}

/*
 * set_function_pathlist
 *              Build the (single) access path for a function RTE
 */
static void
set_function_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte)
{
        /* Mark rel with estimated output rows, width, etc */
        set_function_size_estimates(root, rel);

        /* Generate appropriate path */
        add_path(rel, create_functionscan_path(root, rel));

        /* Select cheapest path (pretty easy in this case...) */
        set_cheapest(rel);
}

/*
 * make_fromexpr_rel
 *        Build access paths for a FromExpr jointree node.
 */
RelOptInfo *
make_fromexpr_rel(Query *root, FromExpr *from)
{
        int                     levels_needed;
        List       *initial_rels = NIL;
        ListCell   *jt;

        /*
         * Count the number of child jointree nodes.  This is the depth of the
         * dynamic-programming algorithm we must employ to consider all ways
         * of joining the child nodes.
         */
        levels_needed = list_length(from->fromlist);

        if (levels_needed <= 0)
                return NULL;                    /* nothing to do? */

        /*
         * Construct a list of rels corresponding to the child jointree nodes.
         * This may contain both base rels and rels constructed according to
         * explicit JOIN directives.
         */
        foreach(jt, from->fromlist)
        {
                Node       *jtnode = (Node *) lfirst(jt);

                initial_rels = lappend(initial_rels,
                                                           make_jointree_rel(root, jtnode));
        }

        if (levels_needed == 1)
        {
                /*
                 * Single jointree node, so we're done.
                 */
                return (RelOptInfo *) linitial(initial_rels);
        }
        else
        {
                /*
                 * Consider the different orders in which we could join the rels,
                 * using either GEQO or regular optimizer.
                 */
                if (enable_geqo && levels_needed >= geqo_threshold)
                        return geqo(root, levels_needed, initial_rels);
                else
                        return make_one_rel_by_joins(root, levels_needed, initial_rels);
        }
}

/*
 * make_one_rel_by_joins
 *        Find all possible joinpaths for a query by successively finding ways
 *        to join component relations into join relations.
 *
 * 'levels_needed' is the number of iterations needed, ie, the number of
 *              independent jointree items in the query.  This is > 1.
 *
 * 'initial_rels' is a list of RelOptInfo nodes for each independent
 *              jointree item.  These are the components to be joined together.
 *
 * Returns the final level of join relations, i.e., the relation that is
 * the result of joining all the original relations together.
 */
static RelOptInfo *
make_one_rel_by_joins(Query *root, int levels_needed, List *initial_rels)
{
        List      **joinitems;
        int                     lev;
        RelOptInfo *rel;

        /*
         * We employ a simple "dynamic programming" algorithm: we first find
         * all ways to build joins of two jointree items, then all ways to
         * build joins of three items (from two-item joins and single items),
         * then four-item joins, and so on until we have considered all ways
         * to join all the items into one rel.
         *
         * joinitems[j] is a list of all the j-item rels.  Initially we set
         * joinitems[1] to represent all the single-jointree-item relations.
         */
        joinitems = (List **) palloc0((levels_needed + 1) * sizeof(List *));

        joinitems[1] = initial_rels;

        for (lev = 2; lev <= levels_needed; lev++)
        {
                ListCell   *x;

                /*
                 * Determine all possible pairs of relations to be joined at this
                 * level, and build paths for making each one from every available
                 * pair of lower-level relations.
                 */
                joinitems[lev] = make_rels_by_joins(root, lev, joinitems);

                /*
                 * Do cleanup work on each just-processed rel.
                 */
                foreach(x, joinitems[lev])
                {
                        rel = (RelOptInfo *) lfirst(x);

                        /* Find and save the cheapest paths for this rel */
                        set_cheapest(rel);

#ifdef OPTIMIZER_DEBUG
                        debug_print_rel(root, rel);
#endif
                }
        }

        /*
         * We should have a single rel at the final level.
         */
        if (joinitems[levels_needed] == NIL)
                elog(ERROR, "failed to build any %d-way joins", levels_needed);
        Assert(list_length(joinitems[levels_needed]) == 1);

        rel = (RelOptInfo *) linitial(joinitems[levels_needed]);

        return rel;
}

/*****************************************************************************
 *                      PUSHING QUALS DOWN INTO SUBQUERIES
 *****************************************************************************/

/*
 * subquery_is_pushdown_safe - is a subquery safe for pushing down quals?
 *
 * subquery is the particular component query being checked.  topquery
 * is the top component of a set-operations tree (the same Query if no
 * set-op is involved).
 *
 * Conditions checked here:
 *
 * 1. If the subquery has a LIMIT clause, we must not push down any quals,
 * since that could change the set of rows returned.
 *
 * 2. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
 * quals into it, because that would change the results.
 *
 * 3. For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
 * push quals into each component query, but the quals can only reference
 * subquery columns that suffer no type coercions in the set operation.
 * Otherwise there are possible semantic gotchas.  So, we check the
 * component queries to see if any of them have different output types;
 * differentTypes[k] is set true if column k has different type in any
 * component.
 */
static bool
subquery_is_pushdown_safe(Query *subquery, Query *topquery,
                                                  bool *differentTypes)
{
        SetOperationStmt *topop;

        /* Check point 1 */
        if (subquery->limitOffset != NULL || subquery->limitCount != NULL)
                return false;

        /* Are we at top level, or looking at a setop component? */
        if (subquery == topquery)
        {
                /* Top level, so check any component queries */
                if (subquery->setOperations != NULL)
                        if (!recurse_pushdown_safe(subquery->setOperations, topquery,
                                                                           differentTypes))
                                return false;
        }
        else
        {
                /* Setop component must not have more components (too weird) */
                if (subquery->setOperations != NULL)
                        return false;
                /* Check whether setop component output types match top level */
                topop = (SetOperationStmt *) topquery->setOperations;
                Assert(topop && IsA(topop, SetOperationStmt));
                compare_tlist_datatypes(subquery->targetList,
                                                                topop->colTypes,
                                                                differentTypes);
        }
        return true;
}

/*
 * Helper routine to recurse through setOperations tree
 */
static bool
recurse_pushdown_safe(Node *setOp, Query *topquery,
                                          bool *differentTypes)
{
        if (IsA(setOp, RangeTblRef))
        {
                RangeTblRef *rtr = (RangeTblRef *) setOp;
                RangeTblEntry *rte = rt_fetch(rtr->rtindex, topquery->rtable);
                Query      *subquery = rte->subquery;

                Assert(subquery != NULL);
                return subquery_is_pushdown_safe(subquery, topquery, differentTypes);
        }
        else if (IsA(setOp, SetOperationStmt))
        {
                SetOperationStmt *op = (SetOperationStmt *) setOp;

                /* EXCEPT is no good */
                if (op->op == SETOP_EXCEPT)
                        return false;
                /* Else recurse */
                if (!recurse_pushdown_safe(op->larg, topquery, differentTypes))
                        return false;
                if (!recurse_pushdown_safe(op->rarg, topquery, differentTypes))
                        return false;
        }
        else
        {
                elog(ERROR, "unrecognized node type: %d",
                         (int) nodeTag(setOp));
        }
        return true;
}

/*
 * Compare tlist's datatypes against the list of set-operation result types.
 * For any items that are different, mark the appropriate element of
 * differentTypes[] to show that this column will have type conversions.
 */
static void
compare_tlist_datatypes(List *tlist, List *colTypes,
                                                bool *differentTypes)
{
        ListCell   *l;
        ListCell   *colType = list_head(colTypes);

        foreach(l, tlist)
        {
                TargetEntry *tle = (TargetEntry *) lfirst(l);

                if (tle->resjunk)
                        continue;                       /* ignore resjunk columns */
                if (colType == NULL)
                        elog(ERROR, "wrong number of tlist entries");
                if (exprType((Node *) tle->expr) != lfirst_oid(colType))
                        differentTypes[tle->resno] = true;
                colType = lnext(colType);
        }
        if (colType != NULL)
                elog(ERROR, "wrong number of tlist entries");
}

/*
 * qual_is_pushdown_safe - is a particular qual safe to push down?
 *
 * qual is a restriction clause applying to the given subquery (whose RTE
 * has index rti in the parent query).
 *
 * Conditions checked here:
 *
 * 1. The qual must not contain any subselects (mainly because I'm not sure
 * it will work correctly: sublinks will already have been transformed into
 * subplans in the qual, but not in the subquery).
 *
 * 2. The qual must not refer to any subquery output columns that were
 * found to have inconsistent types across a set operation tree by
 * subquery_is_pushdown_safe().
 *
 * 3. If the subquery uses DISTINCT ON, we must not push down any quals that
 * refer to non-DISTINCT output columns, because that could change the set
 * of rows returned.  This condition is vacuous for DISTINCT, because then
 * there are no non-DISTINCT output columns, but unfortunately it's fairly
 * expensive to tell the difference between DISTINCT and DISTINCT ON in the
 * parsetree representation.  It's cheaper to just make sure all the Vars
 * in the qual refer to DISTINCT columns.
 *
 * 4. We must not push down any quals that refer to subselect outputs that
 * return sets, else we'd introduce functions-returning-sets into the
 * subquery's WHERE/HAVING quals.
 */
static bool
qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
                                          bool *differentTypes)
{
        bool            safe = true;
        List       *vars;
        ListCell   *vl;
        Bitmapset  *tested = NULL;

        /* Refuse subselects (point 1) */
        if (contain_subplans(qual))
                return false;

        /*
         * Examine all Vars used in clause; since it's a restriction clause,
         * all such Vars must refer to subselect output columns.
         */
        vars = pull_var_clause(qual, false);
        foreach(vl, vars)
        {
                Var                *var = (Var *) lfirst(vl);
                TargetEntry *tle;

                Assert(var->varno == rti);

                /*
                 * We use a bitmapset to avoid testing the same attno more than
                 * once.  (NB: this only works because subquery outputs can't have
                 * negative attnos.)
                 */
                if (bms_is_member(var->varattno, tested))
                        continue;
                tested = bms_add_member(tested, var->varattno);

                /* Check point 2 */
                if (differentTypes[var->varattno])
                {
                        safe = false;
                        break;
                }

                /* Must find the tlist element referenced by the Var */
                tle = get_tle_by_resno(subquery->targetList, var->varattno);
                Assert(tle != NULL);
                Assert(!tle->resjunk);

                /* If subquery uses DISTINCT or DISTINCT ON, check point 3 */
                if (subquery->distinctClause != NIL &&
                        !targetIsInSortList(tle, subquery->distinctClause))
                {
                        /* non-DISTINCT column, so fail */
                        safe = false;
                        break;
                }

                /* Refuse functions returning sets (point 4) */
                if (expression_returns_set((Node *) tle->expr))
                {
                        safe = false;
                        break;
                }
        }

        list_free(vars);
        bms_free(tested);

        return safe;
}

/*
 * subquery_push_qual - push down a qual that we have determined is safe
 */
static void
subquery_push_qual(Query *subquery, List *rtable, Index rti, Node *qual)
{
        if (subquery->setOperations != NULL)
        {
                /* Recurse to push it separately to each component query */
                recurse_push_qual(subquery->setOperations, subquery,
                                                  rtable, rti, qual);
        }
        else
        {
                /*
                 * We need to replace Vars in the qual (which must refer to
                 * outputs of the subquery) with copies of the subquery's
                 * targetlist expressions.      Note that at this point, any uplevel
                 * Vars in the qual should have been replaced with Params, so they
                 * need no work.
                 *
                 * This step also ensures that when we are pushing into a setop tree,
                 * each component query gets its own copy of the qual.
                 */
                qual = ResolveNew(qual, rti, 0, rtable,
                                                  subquery->targetList,
                                                  CMD_SELECT, 0);

                /*
                 * Now attach the qual to the proper place: normally WHERE, but
                 * if the subquery uses grouping or aggregation, put it in HAVING
                 * (since the qual really refers to the group-result rows).
                 */
                if (subquery->hasAggs || subquery->groupClause || subquery->havingQual)
                        subquery->havingQual = make_and_qual(subquery->havingQual, qual);
                else
                        subquery->jointree->quals =
                                make_and_qual(subquery->jointree->quals, qual);

                /*
                 * We need not change the subquery's hasAggs or hasSublinks flags,
                 * since we can't be pushing down any aggregates that weren't
                 * there before, and we don't push down subselects at all.
                 */
        }
}

/*
 * Helper routine to recurse through setOperations tree
 */
static void
recurse_push_qual(Node *setOp, Query *topquery,
                                  List *rtable, Index rti, Node *qual)
{
        if (IsA(setOp, RangeTblRef))
        {
                RangeTblRef *rtr = (RangeTblRef *) setOp;
                RangeTblEntry *subrte = rt_fetch(rtr->rtindex, topquery->rtable);
                Query      *subquery = subrte->subquery;

                Assert(subquery != NULL);
                subquery_push_qual(subquery, rtable, rti, qual);
        }
        else if (IsA(setOp, SetOperationStmt))
        {
                SetOperationStmt *op = (SetOperationStmt *) setOp;

                recurse_push_qual(op->larg, topquery, rtable, rti, qual);
                recurse_push_qual(op->rarg, topquery, rtable, rti, qual);
        }
        else
        {
                elog(ERROR, "unrecognized node type: %d",
                         (int) nodeTag(setOp));
        }
}

/*****************************************************************************
 *                      DEBUG SUPPORT
 *****************************************************************************/

#ifdef OPTIMIZER_DEBUG

static void
print_relids(Relids relids)
{
        Relids          tmprelids;
        int                     x;
        bool            first = true;

        tmprelids = bms_copy(relids);
        while ((x = bms_first_member(tmprelids)) >= 0)
        {
                if (!first)
                        printf(" ");
                printf("%d", x);
                first = false;
        }
        bms_free(tmprelids);
}

static void
print_restrictclauses(Query *root, List *clauses)
{
        ListCell   *l;

        foreach(l, clauses)
        {
                RestrictInfo *c = lfirst(l);

                print_expr((Node *) c->clause, root->rtable);
                if (lnext(l))
                        printf(", ");
        }
}

static void
print_path(Query *root, Path *path, int indent)
{
        const char *ptype;
        bool            join = false;
        Path       *subpath = NULL;
        int                     i;

        switch (nodeTag(path))
        {
                case T_Path:
                        ptype = "SeqScan";
                        break;
                case T_IndexPath:
                        ptype = "IdxScan";
                        break;
                case T_BitmapHeapPath:
                        ptype = "BitmapHeapScan";
                        break;
                case T_BitmapAndPath:
                        ptype = "BitmapAndPath";
                        break;
                case T_BitmapOrPath:
                        ptype = "BitmapOrPath";
                        break;
                case T_TidPath:
                        ptype = "TidScan";
                        break;
                case T_AppendPath:
                        ptype = "Append";
                        break;
                case T_ResultPath:
                        ptype = "Result";
                        subpath = ((ResultPath *) path)->subpath;
                        break;
                case T_MaterialPath:
                        ptype = "Material";
                        subpath = ((MaterialPath *) path)->subpath;
                        break;
                case T_UniquePath:
                        ptype = "Unique";
                        subpath = ((UniquePath *) path)->subpath;
                        break;
                case T_NestPath:
                        ptype = "NestLoop";
                        join = true;
                        break;
                case T_MergePath:
                        ptype = "MergeJoin";
                        join = true;
                        break;
                case T_HashPath:
                        ptype = "HashJoin";
                        join = true;
                        break;
                default:
                        ptype = "???Path";
                        break;
        }

        for (i = 0; i < indent; i++)
                printf("\t");
        printf("%s", ptype);

        if (path->parent)
        {
                printf("(");
                print_relids(path->parent->relids);
                printf(") rows=%.0f", path->parent->rows);
        }
        printf(" cost=%.2f..%.2f\n", path->startup_cost, path->total_cost);

        if (path->pathkeys)
        {
                for (i = 0; i < indent; i++)
                        printf("\t");
                printf("  pathkeys: ");
                print_pathkeys(path->pathkeys, root->rtable);
        }

        if (join)
        {
                JoinPath   *jp = (JoinPath *) path;

                for (i = 0; i < indent; i++)
                        printf("\t");
                printf("  clauses: ");
                print_restrictclauses(root, jp->joinrestrictinfo);
                printf("\n");

                if (IsA(path, MergePath))
                {
                        MergePath  *mp = (MergePath *) path;

                        if (mp->outersortkeys || mp->innersortkeys)
                        {
                                for (i = 0; i < indent; i++)
                                        printf("\t");
                                printf("  sortouter=%d sortinner=%d\n",
                                           ((mp->outersortkeys) ? 1 : 0),
                                           ((mp->innersortkeys) ? 1 : 0));
                        }
                }

                print_path(root, jp->outerjoinpath, indent + 1);
                print_path(root, jp->innerjoinpath, indent + 1);
        }

        if (subpath)
                print_path(root, subpath, indent + 1);
}

void
debug_print_rel(Query *root, RelOptInfo *rel)
{
        ListCell   *l;

        printf("RELOPTINFO (");
        print_relids(rel->relids);
        printf("): rows=%.0f width=%d\n", rel->rows, rel->width);

        if (rel->baserestrictinfo)
        {
                printf("\tbaserestrictinfo: ");
                print_restrictclauses(root, rel->baserestrictinfo);
                printf("\n");
        }

        foreach(l, rel->joininfo)
        {
                JoinInfo   *j = (JoinInfo *) lfirst(l);

                printf("\tjoininfo (");
                print_relids(j->unjoined_relids);
                printf("): ");
                print_restrictclauses(root, j->jinfo_restrictinfo);
                printf("\n");
        }

        printf("\tpath list:\n");
        foreach(l, rel->pathlist)
                print_path(root, lfirst(l), 1);
        printf("\n\tcheapest startup path:\n");
        print_path(root, rel->cheapest_startup_path, 1);
        printf("\n\tcheapest total path:\n");
        print_path(root, rel->cheapest_total_path, 1);
        printf("\n");
        fflush(stdout);
}

#endif   /* OPTIMIZER_DEBUG */