1 /*-------------------------------------------------------------------------
4 * The query optimizer external interface.
6 * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
11 * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.210 2007/01/05 22:19:32 momjian Exp $
13 *-------------------------------------------------------------------------
20 #include "catalog/pg_operator.h"
21 #include "executor/executor.h"
22 #include "executor/nodeAgg.h"
23 #include "miscadmin.h"
24 #include "nodes/makefuncs.h"
25 #include "optimizer/clauses.h"
26 #include "optimizer/cost.h"
27 #include "optimizer/pathnode.h"
28 #include "optimizer/paths.h"
29 #include "optimizer/planmain.h"
30 #include "optimizer/planner.h"
31 #include "optimizer/prep.h"
32 #include "optimizer/subselect.h"
33 #include "optimizer/tlist.h"
34 #include "optimizer/var.h"
35 #ifdef OPTIMIZER_DEBUG
36 #include "nodes/print.h"
38 #include "parser/parse_expr.h"
39 #include "parser/parse_oper.h"
40 #include "parser/parsetree.h"
41 #include "utils/syscache.h"
44 ParamListInfo PlannerBoundParamList = NULL; /* current boundParams */
47 /* Expression kind codes for preprocess_expression */
48 #define EXPRKIND_QUAL 0
49 #define EXPRKIND_TARGET 1
50 #define EXPRKIND_RTFUNC 2
51 #define EXPRKIND_VALUES 3
52 #define EXPRKIND_LIMIT 4
53 #define EXPRKIND_ININFO 5
54 #define EXPRKIND_APPINFO 6
57 static Node *preprocess_expression(PlannerInfo *root, Node *expr, int kind);
58 static void preprocess_qual_conditions(PlannerInfo *root, Node *jtnode);
59 static Plan *inheritance_planner(PlannerInfo *root);
60 static Plan *grouping_planner(PlannerInfo *root, double tuple_fraction);
61 static bool is_dummy_plan(Plan *plan);
62 static double preprocess_limit(PlannerInfo *root,
63 double tuple_fraction,
64 int64 *offset_est, int64 *count_est);
65 static bool choose_hashed_grouping(PlannerInfo *root, double tuple_fraction,
66 Path *cheapest_path, Path *sorted_path,
67 double dNumGroups, AggClauseCounts *agg_counts);
68 static bool hash_safe_grouping(PlannerInfo *root);
69 static List *make_subplanTargetList(PlannerInfo *root, List *tlist,
70 AttrNumber **groupColIdx, bool *need_tlist_eval);
71 static void locate_grouping_columns(PlannerInfo *root,
74 AttrNumber *groupColIdx);
75 static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
78 /*****************************************************************************
80 * Query optimizer entry point
82 *****************************************************************************/
84 planner(Query *parse, bool isCursor, int cursorOptions,
85 ParamListInfo boundParams)
87 double tuple_fraction;
89 Index save_PlannerQueryLevel;
90 List *save_PlannerParamList;
91 ParamListInfo save_PlannerBoundParamList;
94 * The planner can be called recursively (an example is when
95 * eval_const_expressions tries to pre-evaluate an SQL function). So,
96 * these global state variables must be saved and restored.
98 * Query level and the param list cannot be moved into the per-query
99 * PlannerInfo structure since their whole purpose is communication across
100 * multiple sub-queries. Also, boundParams is explicitly info from outside
101 * the query, and so is likewise better handled as a global variable.
103 * Note we do NOT save and restore PlannerPlanId: it exists to assign
104 * unique IDs to SubPlan nodes, and we want those IDs to be unique for the
105 * life of a backend. Also, PlannerInitPlan is saved/restored in
106 * subquery_planner, not here.
108 save_PlannerQueryLevel = PlannerQueryLevel;
109 save_PlannerParamList = PlannerParamList;
110 save_PlannerBoundParamList = PlannerBoundParamList;
112 /* Initialize state for handling outer-level references and params */
113 PlannerQueryLevel = 0; /* will be 1 in top-level subquery_planner */
114 PlannerParamList = NIL;
115 PlannerBoundParamList = boundParams;
117 /* Determine what fraction of the plan is likely to be scanned */
121 * We have no real idea how many tuples the user will ultimately FETCH
122 * from a cursor, but it seems a good bet that he doesn't want 'em
123 * all. Optimize for 10% retrieval (you gotta better number? Should
124 * this be a SETtable parameter?)
126 tuple_fraction = 0.10;
130 /* Default assumption is we need all the tuples */
131 tuple_fraction = 0.0;
134 /* primary planning entry point (may recurse for subqueries) */
135 result_plan = subquery_planner(parse, tuple_fraction, NULL);
137 /* check we popped out the right number of levels */
138 Assert(PlannerQueryLevel == 0);
141 * If creating a plan for a scrollable cursor, make sure it can run
142 * backwards on demand. Add a Material node at the top at need.
144 if (isCursor && (cursorOptions & CURSOR_OPT_SCROLL))
146 if (!ExecSupportsBackwardScan(result_plan))
147 result_plan = materialize_finished_plan(result_plan);
150 /* final cleanup of the plan */
151 result_plan = set_plan_references(result_plan, parse->rtable);
153 /* executor wants to know total number of Params used overall */
154 result_plan->nParamExec = list_length(PlannerParamList);
156 /* restore state for outer planner, if any */
157 PlannerQueryLevel = save_PlannerQueryLevel;
158 PlannerParamList = save_PlannerParamList;
159 PlannerBoundParamList = save_PlannerBoundParamList;
165 /*--------------------
167 * Invokes the planner on a subquery. We recurse to here for each
168 * sub-SELECT found in the query tree.
170 * parse is the querytree produced by the parser & rewriter.
171 * tuple_fraction is the fraction of tuples we expect will be retrieved.
172 * tuple_fraction is interpreted as explained for grouping_planner, below.
174 * If subquery_pathkeys isn't NULL, it receives a list of pathkeys indicating
175 * the output sort ordering of the completed plan.
177 * Basically, this routine does the stuff that should only be done once
178 * per Query object. It then calls grouping_planner. At one time,
179 * grouping_planner could be invoked recursively on the same Query object;
180 * that's not currently true, but we keep the separation between the two
181 * routines anyway, in case we need it again someday.
183 * subquery_planner will be called recursively to handle sub-Query nodes
184 * found within the query's expressions and rangetable.
186 * Returns a query plan.
187 *--------------------
190 subquery_planner(Query *parse, double tuple_fraction,
191 List **subquery_pathkeys)
193 List *saved_initplan = PlannerInitPlan;
194 int saved_planid = PlannerPlanId;
200 /* Set up for a new level of subquery */
202 PlannerInitPlan = NIL;
204 /* Create a PlannerInfo data structure for this subquery */
205 root = makeNode(PlannerInfo);
207 root->in_info_list = NIL;
208 root->append_rel_list = NIL;
211 * Look for IN clauses at the top level of WHERE, and transform them into
212 * joins. Note that this step only handles IN clauses originally at top
213 * level of WHERE; if we pull up any subqueries in the next step, their
214 * INs are processed just before pulling them up.
216 if (parse->hasSubLinks)
217 parse->jointree->quals = pull_up_IN_clauses(root,
218 parse->jointree->quals);
221 * Check to see if any subqueries in the rangetable can be merged into
224 parse->jointree = (FromExpr *)
225 pull_up_subqueries(root, (Node *) parse->jointree, false, false);
228 * Detect whether any rangetable entries are RTE_JOIN kind; if not, we can
229 * avoid the expense of doing flatten_join_alias_vars(). Also check for
230 * outer joins --- if none, we can skip reduce_outer_joins() and some
231 * other processing. This must be done after we have done
232 * pull_up_subqueries, of course.
234 * Note: if reduce_outer_joins manages to eliminate all outer joins,
235 * root->hasOuterJoins is not reset currently. This is OK since its
236 * purpose is merely to suppress unnecessary processing in simple cases.
238 root->hasJoinRTEs = false;
239 root->hasOuterJoins = false;
240 foreach(l, parse->rtable)
242 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
244 if (rte->rtekind == RTE_JOIN)
246 root->hasJoinRTEs = true;
247 if (IS_OUTER_JOIN(rte->jointype))
249 root->hasOuterJoins = true;
250 /* Can quit scanning once we find an outer join */
257 * Expand any rangetable entries that are inheritance sets into "append
258 * relations". This can add entries to the rangetable, but they must be
259 * plain base relations not joins, so it's OK (and marginally more
260 * efficient) to do it after checking for join RTEs. We must do it after
261 * pulling up subqueries, else we'd fail to handle inherited tables in
264 expand_inherited_tables(root);
267 * Set hasHavingQual to remember if HAVING clause is present. Needed
268 * because preprocess_expression will reduce a constant-true condition to
269 * an empty qual list ... but "HAVING TRUE" is not a semantic no-op.
271 root->hasHavingQual = (parse->havingQual != NULL);
273 /* Clear this flag; might get set in distribute_qual_to_rels */
274 root->hasPseudoConstantQuals = false;
277 * Do expression preprocessing on targetlist and quals.
279 parse->targetList = (List *)
280 preprocess_expression(root, (Node *) parse->targetList,
283 parse->returningList = (List *)
284 preprocess_expression(root, (Node *) parse->returningList,
287 preprocess_qual_conditions(root, (Node *) parse->jointree);
289 parse->havingQual = preprocess_expression(root, parse->havingQual,
292 parse->limitOffset = preprocess_expression(root, parse->limitOffset,
294 parse->limitCount = preprocess_expression(root, parse->limitCount,
297 root->in_info_list = (List *)
298 preprocess_expression(root, (Node *) root->in_info_list,
300 root->append_rel_list = (List *)
301 preprocess_expression(root, (Node *) root->append_rel_list,
304 /* Also need to preprocess expressions for function and values RTEs */
305 foreach(l, parse->rtable)
307 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
309 if (rte->rtekind == RTE_FUNCTION)
310 rte->funcexpr = preprocess_expression(root, rte->funcexpr,
312 else if (rte->rtekind == RTE_VALUES)
313 rte->values_lists = (List *)
314 preprocess_expression(root, (Node *) rte->values_lists,
319 * In some cases we may want to transfer a HAVING clause into WHERE. We
320 * cannot do so if the HAVING clause contains aggregates (obviously) or
321 * volatile functions (since a HAVING clause is supposed to be executed
322 * only once per group). Also, it may be that the clause is so expensive
323 * to execute that we're better off doing it only once per group, despite
324 * the loss of selectivity. This is hard to estimate short of doing the
325 * entire planning process twice, so we use a heuristic: clauses
326 * containing subplans are left in HAVING. Otherwise, we move or copy the
327 * HAVING clause into WHERE, in hopes of eliminating tuples before
328 * aggregation instead of after.
330 * If the query has explicit grouping then we can simply move such a
331 * clause into WHERE; any group that fails the clause will not be in the
332 * output because none of its tuples will reach the grouping or
333 * aggregation stage. Otherwise we must have a degenerate (variable-free)
334 * HAVING clause, which we put in WHERE so that query_planner() can use it
335 * in a gating Result node, but also keep in HAVING to ensure that we
336 * don't emit a bogus aggregated row. (This could be done better, but it
337 * seems not worth optimizing.)
339 * Note that both havingQual and parse->jointree->quals are in
340 * implicitly-ANDed-list form at this point, even though they are declared
344 foreach(l, (List *) parse->havingQual)
346 Node *havingclause = (Node *) lfirst(l);
348 if (contain_agg_clause(havingclause) ||
349 contain_volatile_functions(havingclause) ||
350 contain_subplans(havingclause))
352 /* keep it in HAVING */
353 newHaving = lappend(newHaving, havingclause);
355 else if (parse->groupClause)
357 /* move it to WHERE */
358 parse->jointree->quals = (Node *)
359 lappend((List *) parse->jointree->quals, havingclause);
363 /* put a copy in WHERE, keep it in HAVING */
364 parse->jointree->quals = (Node *)
365 lappend((List *) parse->jointree->quals,
366 copyObject(havingclause));
367 newHaving = lappend(newHaving, havingclause);
370 parse->havingQual = (Node *) newHaving;
373 * If we have any outer joins, try to reduce them to plain inner joins.
374 * This step is most easily done after we've done expression
377 if (root->hasOuterJoins)
378 reduce_outer_joins(root);
381 * Do the main planning. If we have an inherited target relation, that
382 * needs special processing, else go straight to grouping_planner.
384 if (parse->resultRelation &&
385 rt_fetch(parse->resultRelation, parse->rtable)->inh)
386 plan = inheritance_planner(root);
388 plan = grouping_planner(root, tuple_fraction);
391 * If any subplans were generated, or if we're inside a subplan, build
392 * initPlan list and extParam/allParam sets for plan nodes, and attach the
393 * initPlans to the top plan node.
395 if (PlannerPlanId != saved_planid || PlannerQueryLevel > 1)
396 SS_finalize_plan(plan, parse->rtable);
398 /* Return sort ordering info if caller wants it */
399 if (subquery_pathkeys)
400 *subquery_pathkeys = root->query_pathkeys;
402 /* Return to outer subquery context */
404 PlannerInitPlan = saved_initplan;
405 /* we do NOT restore PlannerPlanId; that's not an oversight! */
411 * preprocess_expression
412 * Do subquery_planner's preprocessing work for an expression,
413 * which can be a targetlist, a WHERE clause (including JOIN/ON
414 * conditions), or a HAVING clause.
417 preprocess_expression(PlannerInfo *root, Node *expr, int kind)
420 * Fall out quickly if expression is empty. This occurs often enough to
421 * be worth checking. Note that null->null is the correct conversion for
422 * implicit-AND result format, too.
428 * If the query has any join RTEs, replace join alias variables with
429 * base-relation variables. We must do this before sublink processing,
430 * else sublinks expanded out from join aliases wouldn't get processed. We
431 * can skip it in VALUES lists, however, since they can't contain any Vars
434 if (root->hasJoinRTEs && kind != EXPRKIND_VALUES)
435 expr = flatten_join_alias_vars(root, expr);
438 * Simplify constant expressions.
440 * Note: this also flattens nested AND and OR expressions into N-argument
441 * form. All processing of a qual expression after this point must be
442 * careful to maintain AND/OR flatness --- that is, do not generate a tree
443 * with AND directly under AND, nor OR directly under OR.
445 * Because this is a relatively expensive process, we skip it when the
446 * query is trivial, such as "SELECT 2+2;" or "INSERT ... VALUES()". The
447 * expression will only be evaluated once anyway, so no point in
448 * pre-simplifying; we can't execute it any faster than the executor can,
449 * and we will waste cycles copying the tree. Notice however that we
450 * still must do it for quals (to get AND/OR flatness); and if we are in a
451 * subquery we should not assume it will be done only once.
453 * For VALUES lists we never do this at all, again on the grounds that we
454 * should optimize for one-time evaluation.
456 if (kind != EXPRKIND_VALUES &&
457 (root->parse->jointree->fromlist != NIL ||
458 kind == EXPRKIND_QUAL ||
459 PlannerQueryLevel > 1))
460 expr = eval_const_expressions(expr);
463 * If it's a qual or havingQual, canonicalize it.
465 if (kind == EXPRKIND_QUAL)
467 expr = (Node *) canonicalize_qual((Expr *) expr);
469 #ifdef OPTIMIZER_DEBUG
470 printf("After canonicalize_qual()\n");
475 /* Expand SubLinks to SubPlans */
476 if (root->parse->hasSubLinks)
477 expr = SS_process_sublinks(expr, (kind == EXPRKIND_QUAL));
480 * XXX do not insert anything here unless you have grokked the comments in
481 * SS_replace_correlation_vars ...
484 /* Replace uplevel vars with Param nodes (this IS possible in VALUES) */
485 if (PlannerQueryLevel > 1)
486 expr = SS_replace_correlation_vars(expr);
489 * If it's a qual or havingQual, convert it to implicit-AND format. (We
490 * don't want to do this before eval_const_expressions, since the latter
491 * would be unable to simplify a top-level AND correctly. Also,
492 * SS_process_sublinks expects explicit-AND format.)
494 if (kind == EXPRKIND_QUAL)
495 expr = (Node *) make_ands_implicit((Expr *) expr);
501 * preprocess_qual_conditions
502 * Recursively scan the query's jointree and do subquery_planner's
503 * preprocessing work on each qual condition found therein.
506 preprocess_qual_conditions(PlannerInfo *root, Node *jtnode)
510 if (IsA(jtnode, RangeTblRef))
512 /* nothing to do here */
514 else if (IsA(jtnode, FromExpr))
516 FromExpr *f = (FromExpr *) jtnode;
519 foreach(l, f->fromlist)
520 preprocess_qual_conditions(root, lfirst(l));
522 f->quals = preprocess_expression(root, f->quals, EXPRKIND_QUAL);
524 else if (IsA(jtnode, JoinExpr))
526 JoinExpr *j = (JoinExpr *) jtnode;
528 preprocess_qual_conditions(root, j->larg);
529 preprocess_qual_conditions(root, j->rarg);
531 j->quals = preprocess_expression(root, j->quals, EXPRKIND_QUAL);
534 elog(ERROR, "unrecognized node type: %d",
535 (int) nodeTag(jtnode));
539 * inheritance_planner
540 * Generate a plan in the case where the result relation is an
543 * We have to handle this case differently from cases where a source relation
544 * is an inheritance set. Source inheritance is expanded at the bottom of the
545 * plan tree (see allpaths.c), but target inheritance has to be expanded at
546 * the top. The reason is that for UPDATE, each target relation needs a
547 * different targetlist matching its own column set. Also, for both UPDATE
548 * and DELETE, the executor needs the Append plan node at the top, else it
549 * can't keep track of which table is the current target table. Fortunately,
550 * the UPDATE/DELETE target can never be the nullable side of an outer join,
551 * so it's OK to generate the plan this way.
553 * Returns a query plan.
556 inheritance_planner(PlannerInfo *root)
558 Query *parse = root->parse;
559 int parentRTindex = parse->resultRelation;
560 List *subplans = NIL;
561 List *resultRelations = NIL;
562 List *returningLists = NIL;
568 foreach(l, root->append_rel_list)
570 AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
573 /* append_rel_list contains all append rels; ignore others */
574 if (appinfo->parent_relid != parentRTindex)
578 * Generate modified query with this rel as target. We have to be
579 * prepared to translate varnos in in_info_list as well as in the
582 memcpy(&subroot, root, sizeof(PlannerInfo));
583 subroot.parse = (Query *)
584 adjust_appendrel_attrs((Node *) parse,
586 subroot.in_info_list = (List *)
587 adjust_appendrel_attrs((Node *) root->in_info_list,
589 /* There shouldn't be any OJ info to translate, as yet */
590 Assert(subroot.oj_info_list == NIL);
593 subplan = grouping_planner(&subroot, 0.0 /* retrieve all tuples */ );
596 * If this child rel was excluded by constraint exclusion, exclude it
599 if (is_dummy_plan(subplan))
602 /* Save rtable and tlist from first rel for use below */
605 rtable = subroot.parse->rtable;
606 tlist = subplan->targetlist;
609 subplans = lappend(subplans, subplan);
611 /* Build target-relations list for the executor */
612 resultRelations = lappend_int(resultRelations, appinfo->child_relid);
614 /* Build list of per-relation RETURNING targetlists */
615 if (parse->returningList)
617 Assert(list_length(subroot.parse->returningLists) == 1);
618 returningLists = list_concat(returningLists,
619 subroot.parse->returningLists);
623 parse->resultRelations = resultRelations;
624 parse->returningLists = returningLists;
626 /* Mark result as unordered (probably unnecessary) */
627 root->query_pathkeys = NIL;
630 * If we managed to exclude every child rel, return a dummy plan
633 return (Plan *) make_result(tlist,
634 (Node *) list_make1(makeBoolConst(false,
639 * Planning might have modified the rangetable, due to changes of the
640 * Query structures inside subquery RTEs. We have to ensure that this
641 * gets propagated back to the master copy. But can't do this until we
642 * are done planning, because all the calls to grouping_planner need
643 * virgin sub-Queries to work from. (We are effectively assuming that
644 * sub-Queries will get planned identically each time, or at least that
645 * the impacts on their rangetables will be the same each time.)
647 * XXX should clean this up someday
649 parse->rtable = rtable;
651 return (Plan *) make_append(subplans, true, tlist);
654 /*--------------------
656 * Perform planning steps related to grouping, aggregation, etc.
657 * This primarily means adding top-level processing to the basic
658 * query plan produced by query_planner.
660 * tuple_fraction is the fraction of tuples we expect will be retrieved
662 * tuple_fraction is interpreted as follows:
663 * 0: expect all tuples to be retrieved (normal case)
664 * 0 < tuple_fraction < 1: expect the given fraction of tuples available
665 * from the plan to be retrieved
666 * tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
667 * expected to be retrieved (ie, a LIMIT specification)
669 * Returns a query plan. Also, root->query_pathkeys is returned as the
670 * actual output ordering of the plan (in pathkey format).
671 *--------------------
674 grouping_planner(PlannerInfo *root, double tuple_fraction)
676 Query *parse = root->parse;
677 List *tlist = parse->targetList;
678 int64 offset_est = 0;
681 List *current_pathkeys;
683 double dNumGroups = 0;
685 /* Tweak caller-supplied tuple_fraction if have LIMIT/OFFSET */
686 if (parse->limitCount || parse->limitOffset)
687 tuple_fraction = preprocess_limit(root, tuple_fraction,
688 &offset_est, &count_est);
690 if (parse->setOperations)
692 List *set_sortclauses;
695 * If there's a top-level ORDER BY, assume we have to fetch all the
696 * tuples. This might seem too simplistic given all the hackery below
697 * to possibly avoid the sort ... but a nonzero tuple_fraction is only
698 * of use to plan_set_operations() when the setop is UNION ALL, and
699 * the result of UNION ALL is always unsorted.
701 if (parse->sortClause)
702 tuple_fraction = 0.0;
705 * Construct the plan for set operations. The result will not need
706 * any work except perhaps a top-level sort and/or LIMIT.
708 result_plan = plan_set_operations(root, tuple_fraction,
712 * Calculate pathkeys representing the sort order (if any) of the set
713 * operation's result. We have to do this before overwriting the sort
716 current_pathkeys = make_pathkeys_for_sortclauses(set_sortclauses,
717 result_plan->targetlist);
718 current_pathkeys = canonicalize_pathkeys(root, current_pathkeys);
721 * We should not need to call preprocess_targetlist, since we must be
722 * in a SELECT query node. Instead, use the targetlist returned by
723 * plan_set_operations (since this tells whether it returned any
724 * resjunk columns!), and transfer any sort key information from the
727 Assert(parse->commandType == CMD_SELECT);
729 tlist = postprocess_setop_tlist(result_plan->targetlist, tlist);
732 * Can't handle FOR UPDATE/SHARE here (parser should have checked
733 * already, but let's make sure).
737 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
738 errmsg("SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT")));
741 * Calculate pathkeys that represent result ordering requirements
743 sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
745 sort_pathkeys = canonicalize_pathkeys(root, sort_pathkeys);
749 /* No set operations, do regular planning */
751 List *group_pathkeys;
752 AttrNumber *groupColIdx = NULL;
753 bool need_tlist_eval = true;
759 AggClauseCounts agg_counts;
760 int numGroupCols = list_length(parse->groupClause);
761 bool use_hashed_grouping = false;
763 MemSet(&agg_counts, 0, sizeof(AggClauseCounts));
765 /* Preprocess targetlist */
766 tlist = preprocess_targetlist(root, tlist);
769 * Generate appropriate target list for subplan; may be different from
770 * tlist if grouping or aggregation is needed.
772 sub_tlist = make_subplanTargetList(root, tlist,
773 &groupColIdx, &need_tlist_eval);
776 * Calculate pathkeys that represent grouping/ordering requirements.
777 * Stash them in PlannerInfo so that query_planner can canonicalize
780 root->group_pathkeys =
781 make_pathkeys_for_sortclauses(parse->groupClause, tlist);
782 root->sort_pathkeys =
783 make_pathkeys_for_sortclauses(parse->sortClause, tlist);
786 * Will need actual number of aggregates for estimating costs.
788 * Note: we do not attempt to detect duplicate aggregates here; a
789 * somewhat-overestimated count is okay for our present purposes.
791 * Note: think not that we can turn off hasAggs if we find no aggs. It
792 * is possible for constant-expression simplification to remove all
793 * explicit references to aggs, but we still have to follow the
794 * aggregate semantics (eg, producing only one output row).
798 count_agg_clauses((Node *) tlist, &agg_counts);
799 count_agg_clauses(parse->havingQual, &agg_counts);
803 * Figure out whether we need a sorted result from query_planner.
805 * If we have a GROUP BY clause, then we want a result sorted properly
806 * for grouping. Otherwise, if there is an ORDER BY clause, we want
807 * to sort by the ORDER BY clause. (Note: if we have both, and ORDER
808 * BY is a superset of GROUP BY, it would be tempting to request sort
809 * by ORDER BY --- but that might just leave us failing to exploit an
810 * available sort order at all. Needs more thought...)
812 if (parse->groupClause)
813 root->query_pathkeys = root->group_pathkeys;
814 else if (parse->sortClause)
815 root->query_pathkeys = root->sort_pathkeys;
817 root->query_pathkeys = NIL;
820 * Generate the best unsorted and presorted paths for this Query (but
821 * note there may not be any presorted path). query_planner will also
822 * estimate the number of groups in the query, and canonicalize all
825 query_planner(root, sub_tlist, tuple_fraction,
826 &cheapest_path, &sorted_path, &dNumGroups);
828 group_pathkeys = root->group_pathkeys;
829 sort_pathkeys = root->sort_pathkeys;
832 * If grouping, decide whether we want to use hashed grouping.
834 if (parse->groupClause)
836 use_hashed_grouping =
837 choose_hashed_grouping(root, tuple_fraction,
838 cheapest_path, sorted_path,
839 dNumGroups, &agg_counts);
841 /* Also convert # groups to long int --- but 'ware overflow! */
842 numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
846 * Select the best path. If we are doing hashed grouping, we will
847 * always read all the input tuples, so use the cheapest-total path.
848 * Otherwise, trust query_planner's decision about which to use.
850 if (use_hashed_grouping || !sorted_path)
851 best_path = cheapest_path;
853 best_path = sorted_path;
856 * Check to see if it's possible to optimize MIN/MAX aggregates. If
857 * so, we will forget all the work we did so far to choose a "regular"
858 * path ... but we had to do it anyway to be able to tell which way is
861 result_plan = optimize_minmax_aggregates(root,
864 if (result_plan != NULL)
867 * optimize_minmax_aggregates generated the full plan, with the
868 * right tlist, and it has no sort order.
870 current_pathkeys = NIL;
875 * Normal case --- create a plan according to query_planner's
878 result_plan = create_plan(root, best_path);
879 current_pathkeys = best_path->pathkeys;
882 * create_plan() returns a plan with just a "flat" tlist of
883 * required Vars. Usually we need to insert the sub_tlist as the
884 * tlist of the top plan node. However, we can skip that if we
885 * determined that whatever query_planner chose to return will be
891 * If the top-level plan node is one that cannot do expression
892 * evaluation, we must insert a Result node to project the
895 if (!is_projection_capable_plan(result_plan))
897 result_plan = (Plan *) make_result(sub_tlist, NULL,
903 * Otherwise, just replace the subplan's flat tlist with
906 result_plan->targetlist = sub_tlist;
910 * Also, account for the cost of evaluation of the sub_tlist.
912 * Up to now, we have only been dealing with "flat" tlists,
913 * containing just Vars. So their evaluation cost is zero
914 * according to the model used by cost_qual_eval() (or if you
915 * prefer, the cost is factored into cpu_tuple_cost). Thus we
916 * can avoid accounting for tlist cost throughout
917 * query_planner() and subroutines. But now we've inserted a
918 * tlist that might contain actual operators, sub-selects, etc
919 * --- so we'd better account for its cost.
921 * Below this point, any tlist eval cost for added-on nodes
922 * should be accounted for as we create those nodes.
923 * Presently, of the node types we can add on, only Agg and
924 * Group project new tlists (the rest just copy their input
925 * tuples) --- so make_agg() and make_group() are responsible
926 * for computing the added cost.
928 cost_qual_eval(&tlist_cost, sub_tlist);
929 result_plan->startup_cost += tlist_cost.startup;
930 result_plan->total_cost += tlist_cost.startup +
931 tlist_cost.per_tuple * result_plan->plan_rows;
936 * Since we're using query_planner's tlist and not the one
937 * make_subplanTargetList calculated, we have to refigure any
938 * grouping-column indexes make_subplanTargetList computed.
940 locate_grouping_columns(root, tlist, result_plan->targetlist,
945 * Insert AGG or GROUP node if needed, plus an explicit sort step
948 * HAVING clause, if any, becomes qual of the Agg or Group node.
950 if (use_hashed_grouping)
952 /* Hashed aggregate plan --- no sort needed */
953 result_plan = (Plan *) make_agg(root,
955 (List *) parse->havingQual,
962 /* Hashed aggregation produces randomly-ordered results */
963 current_pathkeys = NIL;
965 else if (parse->hasAggs)
967 /* Plain aggregate plan --- sort if needed */
968 AggStrategy aggstrategy;
970 if (parse->groupClause)
972 if (!pathkeys_contained_in(group_pathkeys,
975 result_plan = (Plan *)
976 make_sort_from_groupcols(root,
980 current_pathkeys = group_pathkeys;
982 aggstrategy = AGG_SORTED;
985 * The AGG node will not change the sort ordering of its
986 * groups, so current_pathkeys describes the result too.
991 aggstrategy = AGG_PLAIN;
992 /* Result will be only one row anyway; no sort order */
993 current_pathkeys = NIL;
996 result_plan = (Plan *) make_agg(root,
998 (List *) parse->havingQual,
1006 else if (parse->groupClause)
1009 * GROUP BY without aggregation, so insert a group node (plus
1010 * the appropriate sort node, if necessary).
1012 * Add an explicit sort if we couldn't make the path come out
1013 * the way the GROUP node needs it.
1015 if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
1017 result_plan = (Plan *)
1018 make_sort_from_groupcols(root,
1022 current_pathkeys = group_pathkeys;
1025 result_plan = (Plan *) make_group(root,
1027 (List *) parse->havingQual,
1032 /* The Group node won't change sort ordering */
1034 else if (root->hasHavingQual)
1037 * No aggregates, and no GROUP BY, but we have a HAVING qual.
1038 * This is a degenerate case in which we are supposed to emit
1039 * either 0 or 1 row depending on whether HAVING succeeds.
1040 * Furthermore, there cannot be any variables in either HAVING
1041 * or the targetlist, so we actually do not need the FROM
1042 * table at all! We can just throw away the plan-so-far and
1043 * generate a Result node. This is a sufficiently unusual
1044 * corner case that it's not worth contorting the structure of
1045 * this routine to avoid having to generate the plan in the
1048 result_plan = (Plan *) make_result(tlist,
1052 } /* end of non-minmax-aggregate case */
1053 } /* end of if (setOperations) */
1056 * If we were not able to make the plan come out in the right order, add
1057 * an explicit sort step.
1059 if (parse->sortClause)
1061 if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
1063 result_plan = (Plan *)
1064 make_sort_from_sortclauses(root,
1067 current_pathkeys = sort_pathkeys;
1072 * If there is a DISTINCT clause, add the UNIQUE node.
1074 if (parse->distinctClause)
1076 result_plan = (Plan *) make_unique(result_plan, parse->distinctClause);
1079 * If there was grouping or aggregation, leave plan_rows as-is (ie,
1080 * assume the result was already mostly unique). If not, use the
1081 * number of distinct-groups calculated by query_planner.
1083 if (!parse->groupClause && !root->hasHavingQual && !parse->hasAggs)
1084 result_plan->plan_rows = dNumGroups;
1088 * Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
1090 if (parse->limitCount || parse->limitOffset)
1092 result_plan = (Plan *) make_limit(result_plan,
1100 * Deal with the RETURNING clause if any. It's convenient to pass the
1101 * returningList through setrefs.c now rather than at top level (if we
1102 * waited, handling inherited UPDATE/DELETE would be much harder).
1104 if (parse->returningList)
1108 rlist = set_returning_clause_references(parse->returningList,
1110 parse->resultRelation);
1111 parse->returningLists = list_make1(rlist);
1115 * Return the actual output ordering in query_pathkeys for possible use by
1116 * an outer query level.
1118 root->query_pathkeys = current_pathkeys;
1124 * Detect whether a plan node is a "dummy" plan created when a relation
1125 * is deemed not to need scanning due to constraint exclusion.
1127 * Currently, such dummy plans are Result nodes with constant FALSE
1131 is_dummy_plan(Plan *plan)
1133 if (IsA(plan, Result))
1135 List *rcqual = (List *) ((Result *) plan)->resconstantqual;
1137 if (list_length(rcqual) == 1)
1139 Const *constqual = (Const *) linitial(rcqual);
1141 if (constqual && IsA(constqual, Const))
1143 if (!constqual->constisnull &&
1144 !DatumGetBool(constqual->constvalue))
1153 * preprocess_limit - do pre-estimation for LIMIT and/or OFFSET clauses
1155 * We try to estimate the values of the LIMIT/OFFSET clauses, and pass the
1156 * results back in *count_est and *offset_est. These variables are set to
1157 * 0 if the corresponding clause is not present, and -1 if it's present
1158 * but we couldn't estimate the value for it. (The "0" convention is OK
1159 * for OFFSET but a little bit bogus for LIMIT: effectively we estimate
1160 * LIMIT 0 as though it were LIMIT 1. But this is in line with the planner's
1161 * usual practice of never estimating less than one row.) These values will
1162 * be passed to make_limit, which see if you change this code.
1164 * The return value is the suitably adjusted tuple_fraction to use for
1165 * planning the query. This adjustment is not overridable, since it reflects
1166 * plan actions that grouping_planner() will certainly take, not assumptions
1170 preprocess_limit(PlannerInfo *root, double tuple_fraction,
1171 int64 *offset_est, int64 *count_est)
1173 Query *parse = root->parse;
1175 double limit_fraction;
1177 /* Should not be called unless LIMIT or OFFSET */
1178 Assert(parse->limitCount || parse->limitOffset);
1181 * Try to obtain the clause values. We use estimate_expression_value
1182 * primarily because it can sometimes do something useful with Params.
1184 if (parse->limitCount)
1186 est = estimate_expression_value(parse->limitCount);
1187 if (est && IsA(est, Const))
1189 if (((Const *) est)->constisnull)
1191 /* NULL indicates LIMIT ALL, ie, no limit */
1192 *count_est = 0; /* treat as not present */
1196 *count_est = DatumGetInt64(((Const *) est)->constvalue);
1197 if (*count_est <= 0)
1198 *count_est = 1; /* force to at least 1 */
1202 *count_est = -1; /* can't estimate */
1205 *count_est = 0; /* not present */
1207 if (parse->limitOffset)
1209 est = estimate_expression_value(parse->limitOffset);
1210 if (est && IsA(est, Const))
1212 if (((Const *) est)->constisnull)
1214 /* Treat NULL as no offset; the executor will too */
1215 *offset_est = 0; /* treat as not present */
1219 *offset_est = DatumGetInt64(((Const *) est)->constvalue);
1220 if (*offset_est < 0)
1221 *offset_est = 0; /* less than 0 is same as 0 */
1225 *offset_est = -1; /* can't estimate */
1228 *offset_est = 0; /* not present */
1230 if (*count_est != 0)
1233 * A LIMIT clause limits the absolute number of tuples returned.
1234 * However, if it's not a constant LIMIT then we have to guess; for
1235 * lack of a better idea, assume 10% of the plan's result is wanted.
1237 if (*count_est < 0 || *offset_est < 0)
1239 /* LIMIT or OFFSET is an expression ... punt ... */
1240 limit_fraction = 0.10;
1244 /* LIMIT (plus OFFSET, if any) is max number of tuples needed */
1245 limit_fraction = (double) *count_est + (double) *offset_est;
1249 * If we have absolute limits from both caller and LIMIT, use the
1250 * smaller value; likewise if they are both fractional. If one is
1251 * fractional and the other absolute, we can't easily determine which
1252 * is smaller, but we use the heuristic that the absolute will usually
1255 if (tuple_fraction >= 1.0)
1257 if (limit_fraction >= 1.0)
1260 tuple_fraction = Min(tuple_fraction, limit_fraction);
1264 /* caller absolute, limit fractional; use caller's value */
1267 else if (tuple_fraction > 0.0)
1269 if (limit_fraction >= 1.0)
1271 /* caller fractional, limit absolute; use limit */
1272 tuple_fraction = limit_fraction;
1276 /* both fractional */
1277 tuple_fraction = Min(tuple_fraction, limit_fraction);
1282 /* no info from caller, just use limit */
1283 tuple_fraction = limit_fraction;
1286 else if (*offset_est != 0 && tuple_fraction > 0.0)
1289 * We have an OFFSET but no LIMIT. This acts entirely differently
1290 * from the LIMIT case: here, we need to increase rather than decrease
1291 * the caller's tuple_fraction, because the OFFSET acts to cause more
1292 * tuples to be fetched instead of fewer. This only matters if we got
1293 * a tuple_fraction > 0, however.
1295 * As above, use 10% if OFFSET is present but unestimatable.
1297 if (*offset_est < 0)
1298 limit_fraction = 0.10;
1300 limit_fraction = (double) *offset_est;
1303 * If we have absolute counts from both caller and OFFSET, add them
1304 * together; likewise if they are both fractional. If one is
1305 * fractional and the other absolute, we want to take the larger, and
1306 * we heuristically assume that's the fractional one.
1308 if (tuple_fraction >= 1.0)
1310 if (limit_fraction >= 1.0)
1312 /* both absolute, so add them together */
1313 tuple_fraction += limit_fraction;
1317 /* caller absolute, limit fractional; use limit */
1318 tuple_fraction = limit_fraction;
1323 if (limit_fraction >= 1.0)
1325 /* caller fractional, limit absolute; use caller's value */
1329 /* both fractional, so add them together */
1330 tuple_fraction += limit_fraction;
1331 if (tuple_fraction >= 1.0)
1332 tuple_fraction = 0.0; /* assume fetch all */
1337 return tuple_fraction;
1341 * choose_hashed_grouping - should we use hashed grouping?
1344 choose_hashed_grouping(PlannerInfo *root, double tuple_fraction,
1345 Path *cheapest_path, Path *sorted_path,
1346 double dNumGroups, AggClauseCounts *agg_counts)
1348 int numGroupCols = list_length(root->parse->groupClause);
1349 double cheapest_path_rows;
1350 int cheapest_path_width;
1352 List *current_pathkeys;
1357 * Check can't-do-it conditions, including whether the grouping operators
1360 * Executor doesn't support hashed aggregation with DISTINCT aggregates.
1361 * (Doing so would imply storing *all* the input values in the hash table,
1362 * which seems like a certain loser.)
1364 if (!enable_hashagg)
1366 if (agg_counts->numDistinctAggs != 0)
1368 if (!hash_safe_grouping(root))
1372 * Don't do it if it doesn't look like the hashtable will fit into
1375 * Beware here of the possibility that cheapest_path->parent is NULL. This
1376 * could happen if user does something silly like SELECT 'foo' GROUP BY 1;
1378 if (cheapest_path->parent)
1380 cheapest_path_rows = cheapest_path->parent->rows;
1381 cheapest_path_width = cheapest_path->parent->width;
1385 cheapest_path_rows = 1; /* assume non-set result */
1386 cheapest_path_width = 100; /* arbitrary */
1389 /* Estimate per-hash-entry space at tuple width... */
1390 hashentrysize = MAXALIGN(cheapest_path_width) + MAXALIGN(sizeof(MinimalTupleData));
1391 /* plus space for pass-by-ref transition values... */
1392 hashentrysize += agg_counts->transitionSpace;
1393 /* plus the per-hash-entry overhead */
1394 hashentrysize += hash_agg_entry_size(agg_counts->numAggs);
1396 if (hashentrysize * dNumGroups > work_mem * 1024L)
1400 * See if the estimated cost is no more than doing it the other way. While
1401 * avoiding the need for sorted input is usually a win, the fact that the
1402 * output won't be sorted may be a loss; so we need to do an actual cost
1405 * We need to consider cheapest_path + hashagg [+ final sort] versus
1406 * either cheapest_path [+ sort] + group or agg [+ final sort] or
1407 * presorted_path + group or agg [+ final sort] where brackets indicate a
1408 * step that may not be needed. We assume query_planner() will have
1409 * returned a presorted path only if it's a winner compared to
1410 * cheapest_path for this purpose.
1412 * These path variables are dummies that just hold cost fields; we don't
1413 * make actual Paths for these steps.
1415 cost_agg(&hashed_p, root, AGG_HASHED, agg_counts->numAggs,
1416 numGroupCols, dNumGroups,
1417 cheapest_path->startup_cost, cheapest_path->total_cost,
1418 cheapest_path_rows);
1419 /* Result of hashed agg is always unsorted */
1420 if (root->sort_pathkeys)
1421 cost_sort(&hashed_p, root, root->sort_pathkeys, hashed_p.total_cost,
1422 dNumGroups, cheapest_path_width);
1426 sorted_p.startup_cost = sorted_path->startup_cost;
1427 sorted_p.total_cost = sorted_path->total_cost;
1428 current_pathkeys = sorted_path->pathkeys;
1432 sorted_p.startup_cost = cheapest_path->startup_cost;
1433 sorted_p.total_cost = cheapest_path->total_cost;
1434 current_pathkeys = cheapest_path->pathkeys;
1436 if (!pathkeys_contained_in(root->group_pathkeys, current_pathkeys))
1438 cost_sort(&sorted_p, root, root->group_pathkeys, sorted_p.total_cost,
1439 cheapest_path_rows, cheapest_path_width);
1440 current_pathkeys = root->group_pathkeys;
1443 if (root->parse->hasAggs)
1444 cost_agg(&sorted_p, root, AGG_SORTED, agg_counts->numAggs,
1445 numGroupCols, dNumGroups,
1446 sorted_p.startup_cost, sorted_p.total_cost,
1447 cheapest_path_rows);
1449 cost_group(&sorted_p, root, numGroupCols, dNumGroups,
1450 sorted_p.startup_cost, sorted_p.total_cost,
1451 cheapest_path_rows);
1452 /* The Agg or Group node will preserve ordering */
1453 if (root->sort_pathkeys &&
1454 !pathkeys_contained_in(root->sort_pathkeys, current_pathkeys))
1455 cost_sort(&sorted_p, root, root->sort_pathkeys, sorted_p.total_cost,
1456 dNumGroups, cheapest_path_width);
1459 * Now make the decision using the top-level tuple fraction. First we
1460 * have to convert an absolute count (LIMIT) into fractional form.
1462 if (tuple_fraction >= 1.0)
1463 tuple_fraction /= dNumGroups;
1465 if (compare_fractional_path_costs(&hashed_p, &sorted_p,
1466 tuple_fraction) < 0)
1468 /* Hashed is cheaper, so use it */
1475 * hash_safe_grouping - are grouping operators hashable?
1477 * We assume hashed aggregation will work if the datatype's equality operator
1478 * is marked hashjoinable.
1481 hash_safe_grouping(PlannerInfo *root)
1485 foreach(gl, root->parse->groupClause)
1487 GroupClause *grpcl = (GroupClause *) lfirst(gl);
1488 TargetEntry *tle = get_sortgroupclause_tle(grpcl,
1489 root->parse->targetList);
1493 optup = equality_oper(exprType((Node *) tle->expr), true);
1496 oprcanhash = ((Form_pg_operator) GETSTRUCT(optup))->oprcanhash;
1497 ReleaseSysCache(optup);
1505 * make_subplanTargetList
1506 * Generate appropriate target list when grouping is required.
1508 * When grouping_planner inserts Aggregate, Group, or Result plan nodes
1509 * above the result of query_planner, we typically want to pass a different
1510 * target list to query_planner than the outer plan nodes should have.
1511 * This routine generates the correct target list for the subplan.
1513 * The initial target list passed from the parser already contains entries
1514 * for all ORDER BY and GROUP BY expressions, but it will not have entries
1515 * for variables used only in HAVING clauses; so we need to add those
1516 * variables to the subplan target list. Also, we flatten all expressions
1517 * except GROUP BY items into their component variables; the other expressions
1518 * will be computed by the inserted nodes rather than by the subplan.
1519 * For example, given a query like
1520 * SELECT a+b,SUM(c+d) FROM table GROUP BY a+b;
1521 * we want to pass this targetlist to the subplan:
1523 * where the a+b target will be used by the Sort/Group steps, and the
1524 * other targets will be used for computing the final results. (In the
1525 * above example we could theoretically suppress the a and b targets and
1526 * pass down only c,d,a+b, but it's not really worth the trouble to
1527 * eliminate simple var references from the subplan. We will avoid doing
1528 * the extra computation to recompute a+b at the outer level; see
1529 * replace_vars_with_subplan_refs() in setrefs.c.)
1531 * If we are grouping or aggregating, *and* there are no non-Var grouping
1532 * expressions, then the returned tlist is effectively dummy; we do not
1533 * need to force it to be evaluated, because all the Vars it contains
1534 * should be present in the output of query_planner anyway.
1536 * 'tlist' is the query's target list.
1537 * 'groupColIdx' receives an array of column numbers for the GROUP BY
1538 * expressions (if there are any) in the subplan's target list.
1539 * 'need_tlist_eval' is set true if we really need to evaluate the
1542 * The result is the targetlist to be passed to the subplan.
1546 make_subplanTargetList(PlannerInfo *root,
1548 AttrNumber **groupColIdx,
1549 bool *need_tlist_eval)
1551 Query *parse = root->parse;
1556 *groupColIdx = NULL;
1559 * If we're not grouping or aggregating, there's nothing to do here;
1560 * query_planner should receive the unmodified target list.
1562 if (!parse->hasAggs && !parse->groupClause && !root->hasHavingQual)
1564 *need_tlist_eval = true;
1569 * Otherwise, start with a "flattened" tlist (having just the vars
1570 * mentioned in the targetlist and HAVING qual --- but not upper- level
1571 * Vars; they will be replaced by Params later on).
1573 sub_tlist = flatten_tlist(tlist);
1574 extravars = pull_var_clause(parse->havingQual, false);
1575 sub_tlist = add_to_flat_tlist(sub_tlist, extravars);
1576 list_free(extravars);
1577 *need_tlist_eval = false; /* only eval if not flat tlist */
1580 * If grouping, create sub_tlist entries for all GROUP BY expressions
1581 * (GROUP BY items that are simple Vars should be in the list already),
1582 * and make an array showing where the group columns are in the sub_tlist.
1584 numCols = list_length(parse->groupClause);
1588 AttrNumber *grpColIdx;
1591 grpColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
1592 *groupColIdx = grpColIdx;
1594 foreach(gl, parse->groupClause)
1596 GroupClause *grpcl = (GroupClause *) lfirst(gl);
1597 Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1598 TargetEntry *te = NULL;
1601 /* Find or make a matching sub_tlist entry */
1602 foreach(sl, sub_tlist)
1604 te = (TargetEntry *) lfirst(sl);
1605 if (equal(groupexpr, te->expr))
1610 te = makeTargetEntry((Expr *) groupexpr,
1611 list_length(sub_tlist) + 1,
1614 sub_tlist = lappend(sub_tlist, te);
1615 *need_tlist_eval = true; /* it's not flat anymore */
1618 /* and save its resno */
1619 grpColIdx[keyno++] = te->resno;
1627 * locate_grouping_columns
1628 * Locate grouping columns in the tlist chosen by query_planner.
1630 * This is only needed if we don't use the sub_tlist chosen by
1631 * make_subplanTargetList. We have to forget the column indexes found
1632 * by that routine and re-locate the grouping vars in the real sub_tlist.
1635 locate_grouping_columns(PlannerInfo *root,
1638 AttrNumber *groupColIdx)
1644 * No work unless grouping.
1646 if (!root->parse->groupClause)
1648 Assert(groupColIdx == NULL);
1651 Assert(groupColIdx != NULL);
1653 foreach(gl, root->parse->groupClause)
1655 GroupClause *grpcl = (GroupClause *) lfirst(gl);
1656 Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1657 TargetEntry *te = NULL;
1660 foreach(sl, sub_tlist)
1662 te = (TargetEntry *) lfirst(sl);
1663 if (equal(groupexpr, te->expr))
1667 elog(ERROR, "failed to locate grouping columns");
1669 groupColIdx[keyno++] = te->resno;
1674 * postprocess_setop_tlist
1675 * Fix up targetlist returned by plan_set_operations().
1677 * We need to transpose sort key info from the orig_tlist into new_tlist.
1678 * NOTE: this would not be good enough if we supported resjunk sort keys
1679 * for results of set operations --- then, we'd need to project a whole
1680 * new tlist to evaluate the resjunk columns. For now, just ereport if we
1681 * find any resjunk columns in orig_tlist.
1684 postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
1687 ListCell *orig_tlist_item = list_head(orig_tlist);
1689 foreach(l, new_tlist)
1691 TargetEntry *new_tle = (TargetEntry *) lfirst(l);
1692 TargetEntry *orig_tle;
1694 /* ignore resjunk columns in setop result */
1695 if (new_tle->resjunk)
1698 Assert(orig_tlist_item != NULL);
1699 orig_tle = (TargetEntry *) lfirst(orig_tlist_item);
1700 orig_tlist_item = lnext(orig_tlist_item);
1701 if (orig_tle->resjunk) /* should not happen */
1702 elog(ERROR, "resjunk output columns are not implemented");
1703 Assert(new_tle->resno == orig_tle->resno);
1704 new_tle->ressortgroupref = orig_tle->ressortgroupref;
1706 if (orig_tlist_item != NULL)
1707 elog(ERROR, "resjunk output columns are not implemented");