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 1.215 2007/02/22 22:00:24 tgl 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/lsyscache.h"
42 #include "utils/syscache.h"
45 /* Expression kind codes for preprocess_expression */
46 #define EXPRKIND_QUAL 0
47 #define EXPRKIND_TARGET 1
48 #define EXPRKIND_RTFUNC 2
49 #define EXPRKIND_VALUES 3
50 #define EXPRKIND_LIMIT 4
51 #define EXPRKIND_ININFO 5
52 #define EXPRKIND_APPINFO 6
55 static Node *preprocess_expression(PlannerInfo *root, Node *expr, int kind);
56 static void preprocess_qual_conditions(PlannerInfo *root, Node *jtnode);
57 static Plan *inheritance_planner(PlannerInfo *root);
58 static Plan *grouping_planner(PlannerInfo *root, double tuple_fraction);
59 static bool is_dummy_plan(Plan *plan);
60 static double preprocess_limit(PlannerInfo *root,
61 double tuple_fraction,
62 int64 *offset_est, int64 *count_est);
63 static Oid *extract_grouping_ops(List *groupClause);
64 static bool choose_hashed_grouping(PlannerInfo *root, double tuple_fraction,
65 Path *cheapest_path, Path *sorted_path,
66 Oid *groupOperators, double dNumGroups,
67 AggClauseCounts *agg_counts);
68 static List *make_subplanTargetList(PlannerInfo *root, List *tlist,
69 AttrNumber **groupColIdx, bool *need_tlist_eval);
70 static void locate_grouping_columns(PlannerInfo *root,
73 AttrNumber *groupColIdx);
74 static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
77 /*****************************************************************************
79 * Query optimizer entry point
81 *****************************************************************************/
83 planner(Query *parse, bool isCursor, int cursorOptions,
84 ParamListInfo boundParams)
88 double tuple_fraction;
95 * Set up global state for this planner invocation. This data is needed
96 * across all levels of sub-Query that might exist in the given command,
97 * so we keep it in a separate struct that's linked to by each per-Query
100 glob = makeNode(PlannerGlobal);
102 glob->boundParams = boundParams;
103 glob->paramlist = NIL;
104 glob->subplans = NIL;
105 glob->subrtables = NIL;
106 glob->finalrtable = NIL;
108 /* Determine what fraction of the plan is likely to be scanned */
112 * We have no real idea how many tuples the user will ultimately FETCH
113 * from a cursor, but it seems a good bet that he doesn't want 'em
114 * all. Optimize for 10% retrieval (you gotta better number? Should
115 * this be a SETtable parameter?)
117 tuple_fraction = 0.10;
121 /* Default assumption is we need all the tuples */
122 tuple_fraction = 0.0;
125 /* primary planning entry point (may recurse for subqueries) */
126 top_plan = subquery_planner(glob, parse, 1, tuple_fraction, &root);
129 * If creating a plan for a scrollable cursor, make sure it can run
130 * backwards on demand. Add a Material node at the top at need.
132 if (isCursor && (cursorOptions & CURSOR_OPT_SCROLL))
134 if (!ExecSupportsBackwardScan(top_plan))
135 top_plan = materialize_finished_plan(top_plan);
138 /* final cleanup of the plan */
139 Assert(glob->finalrtable == NIL);
140 top_plan = set_plan_references(glob, top_plan, root->parse->rtable);
141 /* ... and the subplans (both regular subplans and initplans) */
142 Assert(list_length(glob->subplans) == list_length(glob->subrtables));
143 forboth(lp, glob->subplans, lr, glob->subrtables)
145 Plan *subplan = (Plan *) lfirst(lp);
146 List *subrtable = (List *) lfirst(lr);
148 lfirst(lp) = set_plan_references(glob, subplan, subrtable);
151 /* build the PlannedStmt result */
152 result = makeNode(PlannedStmt);
154 result->commandType = parse->commandType;
155 result->canSetTag = parse->canSetTag;
156 result->planTree = top_plan;
157 result->rtable = glob->finalrtable;
158 result->resultRelations = root->resultRelations;
159 result->into = parse->into;
160 result->subplans = glob->subplans;
161 result->returningLists = root->returningLists;
162 result->rowMarks = parse->rowMarks;
163 result->nParamExec = list_length(glob->paramlist);
169 /*--------------------
171 * Invokes the planner on a subquery. We recurse to here for each
172 * sub-SELECT found in the query tree.
174 * glob is the global state for the current planner run.
175 * parse is the querytree produced by the parser & rewriter.
176 * level is the current recursion depth (1 at the top-level Query).
177 * tuple_fraction is the fraction of tuples we expect will be retrieved.
178 * tuple_fraction is interpreted as explained for grouping_planner, below.
180 * If subroot isn't NULL, we pass back the query's final PlannerInfo struct;
181 * among other things this tells the output sort ordering of the plan.
183 * Basically, this routine does the stuff that should only be done once
184 * per Query object. It then calls grouping_planner. At one time,
185 * grouping_planner could be invoked recursively on the same Query object;
186 * that's not currently true, but we keep the separation between the two
187 * routines anyway, in case we need it again someday.
189 * subquery_planner will be called recursively to handle sub-Query nodes
190 * found within the query's expressions and rangetable.
192 * Returns a query plan.
193 *--------------------
196 subquery_planner(PlannerGlobal *glob, Query *parse,
197 Index level, double tuple_fraction,
198 PlannerInfo **subroot)
200 int num_old_subplans = list_length(glob->subplans);
206 /* Create a PlannerInfo data structure for this subquery */
207 root = makeNode(PlannerInfo);
210 root->query_level = level;
211 root->planner_cxt = CurrentMemoryContext;
212 root->init_plans = NIL;
213 root->eq_classes = NIL;
214 root->in_info_list = NIL;
215 root->append_rel_list = NIL;
218 * Look for IN clauses at the top level of WHERE, and transform them into
219 * joins. Note that this step only handles IN clauses originally at top
220 * level of WHERE; if we pull up any subqueries in the next step, their
221 * INs are processed just before pulling them up.
223 if (parse->hasSubLinks)
224 parse->jointree->quals = pull_up_IN_clauses(root,
225 parse->jointree->quals);
228 * Check to see if any subqueries in the rangetable can be merged into
231 parse->jointree = (FromExpr *)
232 pull_up_subqueries(root, (Node *) parse->jointree, false, false);
235 * Detect whether any rangetable entries are RTE_JOIN kind; if not, we can
236 * avoid the expense of doing flatten_join_alias_vars(). Also check for
237 * outer joins --- if none, we can skip reduce_outer_joins() and some
238 * other processing. This must be done after we have done
239 * pull_up_subqueries, of course.
241 * Note: if reduce_outer_joins manages to eliminate all outer joins,
242 * root->hasOuterJoins is not reset currently. This is OK since its
243 * purpose is merely to suppress unnecessary processing in simple cases.
245 root->hasJoinRTEs = false;
246 root->hasOuterJoins = false;
247 foreach(l, parse->rtable)
249 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
251 if (rte->rtekind == RTE_JOIN)
253 root->hasJoinRTEs = true;
254 if (IS_OUTER_JOIN(rte->jointype))
256 root->hasOuterJoins = true;
257 /* Can quit scanning once we find an outer join */
264 * Expand any rangetable entries that are inheritance sets into "append
265 * relations". This can add entries to the rangetable, but they must be
266 * plain base relations not joins, so it's OK (and marginally more
267 * efficient) to do it after checking for join RTEs. We must do it after
268 * pulling up subqueries, else we'd fail to handle inherited tables in
271 expand_inherited_tables(root);
274 * Set hasHavingQual to remember if HAVING clause is present. Needed
275 * because preprocess_expression will reduce a constant-true condition to
276 * an empty qual list ... but "HAVING TRUE" is not a semantic no-op.
278 root->hasHavingQual = (parse->havingQual != NULL);
280 /* Clear this flag; might get set in distribute_qual_to_rels */
281 root->hasPseudoConstantQuals = false;
284 * Do expression preprocessing on targetlist and quals.
286 parse->targetList = (List *)
287 preprocess_expression(root, (Node *) parse->targetList,
290 parse->returningList = (List *)
291 preprocess_expression(root, (Node *) parse->returningList,
294 preprocess_qual_conditions(root, (Node *) parse->jointree);
296 parse->havingQual = preprocess_expression(root, parse->havingQual,
299 parse->limitOffset = preprocess_expression(root, parse->limitOffset,
301 parse->limitCount = preprocess_expression(root, parse->limitCount,
304 root->in_info_list = (List *)
305 preprocess_expression(root, (Node *) root->in_info_list,
307 root->append_rel_list = (List *)
308 preprocess_expression(root, (Node *) root->append_rel_list,
311 /* Also need to preprocess expressions for function and values RTEs */
312 foreach(l, parse->rtable)
314 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
316 if (rte->rtekind == RTE_FUNCTION)
317 rte->funcexpr = preprocess_expression(root, rte->funcexpr,
319 else if (rte->rtekind == RTE_VALUES)
320 rte->values_lists = (List *)
321 preprocess_expression(root, (Node *) rte->values_lists,
326 * In some cases we may want to transfer a HAVING clause into WHERE. We
327 * cannot do so if the HAVING clause contains aggregates (obviously) or
328 * volatile functions (since a HAVING clause is supposed to be executed
329 * only once per group). Also, it may be that the clause is so expensive
330 * to execute that we're better off doing it only once per group, despite
331 * the loss of selectivity. This is hard to estimate short of doing the
332 * entire planning process twice, so we use a heuristic: clauses
333 * containing subplans are left in HAVING. Otherwise, we move or copy the
334 * HAVING clause into WHERE, in hopes of eliminating tuples before
335 * aggregation instead of after.
337 * If the query has explicit grouping then we can simply move such a
338 * clause into WHERE; any group that fails the clause will not be in the
339 * output because none of its tuples will reach the grouping or
340 * aggregation stage. Otherwise we must have a degenerate (variable-free)
341 * HAVING clause, which we put in WHERE so that query_planner() can use it
342 * in a gating Result node, but also keep in HAVING to ensure that we
343 * don't emit a bogus aggregated row. (This could be done better, but it
344 * seems not worth optimizing.)
346 * Note that both havingQual and parse->jointree->quals are in
347 * implicitly-ANDed-list form at this point, even though they are declared
351 foreach(l, (List *) parse->havingQual)
353 Node *havingclause = (Node *) lfirst(l);
355 if (contain_agg_clause(havingclause) ||
356 contain_volatile_functions(havingclause) ||
357 contain_subplans(havingclause))
359 /* keep it in HAVING */
360 newHaving = lappend(newHaving, havingclause);
362 else if (parse->groupClause)
364 /* move it to WHERE */
365 parse->jointree->quals = (Node *)
366 lappend((List *) parse->jointree->quals, havingclause);
370 /* put a copy in WHERE, keep it in HAVING */
371 parse->jointree->quals = (Node *)
372 lappend((List *) parse->jointree->quals,
373 copyObject(havingclause));
374 newHaving = lappend(newHaving, havingclause);
377 parse->havingQual = (Node *) newHaving;
380 * If we have any outer joins, try to reduce them to plain inner joins.
381 * This step is most easily done after we've done expression
384 if (root->hasOuterJoins)
385 reduce_outer_joins(root);
388 * Do the main planning. If we have an inherited target relation, that
389 * needs special processing, else go straight to grouping_planner.
391 if (parse->resultRelation &&
392 rt_fetch(parse->resultRelation, parse->rtable)->inh)
393 plan = inheritance_planner(root);
395 plan = grouping_planner(root, tuple_fraction);
398 * If any subplans were generated, or if we're inside a subplan, build
399 * initPlan list and extParam/allParam sets for plan nodes, and attach the
400 * initPlans to the top plan node.
402 if (list_length(glob->subplans) != num_old_subplans ||
403 root->query_level > 1)
404 SS_finalize_plan(root, plan);
406 /* Return internal info if caller wants it */
414 * preprocess_expression
415 * Do subquery_planner's preprocessing work for an expression,
416 * which can be a targetlist, a WHERE clause (including JOIN/ON
417 * conditions), or a HAVING clause.
420 preprocess_expression(PlannerInfo *root, Node *expr, int kind)
423 * Fall out quickly if expression is empty. This occurs often enough to
424 * be worth checking. Note that null->null is the correct conversion for
425 * implicit-AND result format, too.
431 * If the query has any join RTEs, replace join alias variables with
432 * base-relation variables. We must do this before sublink processing,
433 * else sublinks expanded out from join aliases wouldn't get processed. We
434 * can skip it in VALUES lists, however, since they can't contain any Vars
437 if (root->hasJoinRTEs && kind != EXPRKIND_VALUES)
438 expr = flatten_join_alias_vars(root, expr);
441 * Simplify constant expressions.
443 * Note: this also flattens nested AND and OR expressions into N-argument
444 * form. All processing of a qual expression after this point must be
445 * careful to maintain AND/OR flatness --- that is, do not generate a tree
446 * with AND directly under AND, nor OR directly under OR.
448 * Because this is a relatively expensive process, we skip it when the
449 * query is trivial, such as "SELECT 2+2;" or "INSERT ... VALUES()". The
450 * expression will only be evaluated once anyway, so no point in
451 * pre-simplifying; we can't execute it any faster than the executor can,
452 * and we will waste cycles copying the tree. Notice however that we
453 * still must do it for quals (to get AND/OR flatness); and if we are in a
454 * subquery we should not assume it will be done only once.
456 * For VALUES lists we never do this at all, again on the grounds that we
457 * should optimize for one-time evaluation.
459 if (kind != EXPRKIND_VALUES &&
460 (root->parse->jointree->fromlist != NIL ||
461 kind == EXPRKIND_QUAL ||
462 root->query_level > 1))
463 expr = eval_const_expressions(expr);
466 * If it's a qual or havingQual, canonicalize it.
468 if (kind == EXPRKIND_QUAL)
470 expr = (Node *) canonicalize_qual((Expr *) expr);
472 #ifdef OPTIMIZER_DEBUG
473 printf("After canonicalize_qual()\n");
478 /* Expand SubLinks to SubPlans */
479 if (root->parse->hasSubLinks)
480 expr = SS_process_sublinks(root, expr, (kind == EXPRKIND_QUAL));
483 * XXX do not insert anything here unless you have grokked the comments in
484 * SS_replace_correlation_vars ...
487 /* Replace uplevel vars with Param nodes (this IS possible in VALUES) */
488 if (root->query_level > 1)
489 expr = SS_replace_correlation_vars(root, expr);
492 * If it's a qual or havingQual, convert it to implicit-AND format. (We
493 * don't want to do this before eval_const_expressions, since the latter
494 * would be unable to simplify a top-level AND correctly. Also,
495 * SS_process_sublinks expects explicit-AND format.)
497 if (kind == EXPRKIND_QUAL)
498 expr = (Node *) make_ands_implicit((Expr *) expr);
504 * preprocess_qual_conditions
505 * Recursively scan the query's jointree and do subquery_planner's
506 * preprocessing work on each qual condition found therein.
509 preprocess_qual_conditions(PlannerInfo *root, Node *jtnode)
513 if (IsA(jtnode, RangeTblRef))
515 /* nothing to do here */
517 else if (IsA(jtnode, FromExpr))
519 FromExpr *f = (FromExpr *) jtnode;
522 foreach(l, f->fromlist)
523 preprocess_qual_conditions(root, lfirst(l));
525 f->quals = preprocess_expression(root, f->quals, EXPRKIND_QUAL);
527 else if (IsA(jtnode, JoinExpr))
529 JoinExpr *j = (JoinExpr *) jtnode;
531 preprocess_qual_conditions(root, j->larg);
532 preprocess_qual_conditions(root, j->rarg);
534 j->quals = preprocess_expression(root, j->quals, EXPRKIND_QUAL);
537 elog(ERROR, "unrecognized node type: %d",
538 (int) nodeTag(jtnode));
542 * inheritance_planner
543 * Generate a plan in the case where the result relation is an
546 * We have to handle this case differently from cases where a source relation
547 * is an inheritance set. Source inheritance is expanded at the bottom of the
548 * plan tree (see allpaths.c), but target inheritance has to be expanded at
549 * the top. The reason is that for UPDATE, each target relation needs a
550 * different targetlist matching its own column set. Also, for both UPDATE
551 * and DELETE, the executor needs the Append plan node at the top, else it
552 * can't keep track of which table is the current target table. Fortunately,
553 * the UPDATE/DELETE target can never be the nullable side of an outer join,
554 * so it's OK to generate the plan this way.
556 * Returns a query plan.
559 inheritance_planner(PlannerInfo *root)
561 Query *parse = root->parse;
562 int parentRTindex = parse->resultRelation;
563 List *subplans = NIL;
564 List *resultRelations = NIL;
565 List *returningLists = NIL;
571 foreach(l, root->append_rel_list)
573 AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
576 /* append_rel_list contains all append rels; ignore others */
577 if (appinfo->parent_relid != parentRTindex)
581 * Generate modified query with this rel as target. We have to be
582 * prepared to translate varnos in in_info_list as well as in the
585 memcpy(&subroot, root, sizeof(PlannerInfo));
586 subroot.parse = (Query *)
587 adjust_appendrel_attrs((Node *) parse,
589 subroot.in_info_list = (List *)
590 adjust_appendrel_attrs((Node *) root->in_info_list,
592 subroot.init_plans = NIL;
593 /* There shouldn't be any OJ info to translate, as yet */
594 Assert(subroot.oj_info_list == NIL);
597 subplan = grouping_planner(&subroot, 0.0 /* retrieve all tuples */ );
600 * If this child rel was excluded by constraint exclusion, exclude it
603 if (is_dummy_plan(subplan))
606 /* Save rtable and tlist from first rel for use below */
609 rtable = subroot.parse->rtable;
610 tlist = subplan->targetlist;
613 subplans = lappend(subplans, subplan);
615 /* Make sure any initplans from this rel get into the outer list */
616 root->init_plans = list_concat(root->init_plans, subroot.init_plans);
618 /* Build target-relations list for the executor */
619 resultRelations = lappend_int(resultRelations, appinfo->child_relid);
621 /* Build list of per-relation RETURNING targetlists */
622 if (parse->returningList)
624 Assert(list_length(subroot.returningLists) == 1);
625 returningLists = list_concat(returningLists,
626 subroot.returningLists);
630 root->resultRelations = resultRelations;
631 root->returningLists = returningLists;
633 /* Mark result as unordered (probably unnecessary) */
634 root->query_pathkeys = NIL;
637 * If we managed to exclude every child rel, return a dummy plan
640 return (Plan *) make_result(root,
642 (Node *) list_make1(makeBoolConst(false,
647 * Planning might have modified the rangetable, due to changes of the
648 * Query structures inside subquery RTEs. We have to ensure that this
649 * gets propagated back to the master copy. But can't do this until we
650 * are done planning, because all the calls to grouping_planner need
651 * virgin sub-Queries to work from. (We are effectively assuming that
652 * sub-Queries will get planned identically each time, or at least that
653 * the impacts on their rangetables will be the same each time.)
655 * XXX should clean this up someday
657 parse->rtable = rtable;
659 /* Suppress Append if there's only one surviving child rel */
660 if (list_length(subplans) == 1)
661 return (Plan *) linitial(subplans);
663 return (Plan *) make_append(subplans, true, tlist);
666 /*--------------------
668 * Perform planning steps related to grouping, aggregation, etc.
669 * This primarily means adding top-level processing to the basic
670 * query plan produced by query_planner.
672 * tuple_fraction is the fraction of tuples we expect will be retrieved
674 * tuple_fraction is interpreted as follows:
675 * 0: expect all tuples to be retrieved (normal case)
676 * 0 < tuple_fraction < 1: expect the given fraction of tuples available
677 * from the plan to be retrieved
678 * tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
679 * expected to be retrieved (ie, a LIMIT specification)
681 * Returns a query plan. Also, root->query_pathkeys is returned as the
682 * actual output ordering of the plan (in pathkey format).
683 *--------------------
686 grouping_planner(PlannerInfo *root, double tuple_fraction)
688 Query *parse = root->parse;
689 List *tlist = parse->targetList;
690 int64 offset_est = 0;
693 List *current_pathkeys;
695 double dNumGroups = 0;
697 /* Tweak caller-supplied tuple_fraction if have LIMIT/OFFSET */
698 if (parse->limitCount || parse->limitOffset)
699 tuple_fraction = preprocess_limit(root, tuple_fraction,
700 &offset_est, &count_est);
702 if (parse->setOperations)
704 List *set_sortclauses;
707 * If there's a top-level ORDER BY, assume we have to fetch all the
708 * tuples. This might seem too simplistic given all the hackery below
709 * to possibly avoid the sort ... but a nonzero tuple_fraction is only
710 * of use to plan_set_operations() when the setop is UNION ALL, and
711 * the result of UNION ALL is always unsorted.
713 if (parse->sortClause)
714 tuple_fraction = 0.0;
717 * Construct the plan for set operations. The result will not need
718 * any work except perhaps a top-level sort and/or LIMIT.
720 result_plan = plan_set_operations(root, tuple_fraction,
724 * Calculate pathkeys representing the sort order (if any) of the set
725 * operation's result. We have to do this before overwriting the sort
728 current_pathkeys = make_pathkeys_for_sortclauses(root,
730 result_plan->targetlist,
734 * We should not need to call preprocess_targetlist, since we must be
735 * in a SELECT query node. Instead, use the targetlist returned by
736 * plan_set_operations (since this tells whether it returned any
737 * resjunk columns!), and transfer any sort key information from the
740 Assert(parse->commandType == CMD_SELECT);
742 tlist = postprocess_setop_tlist(result_plan->targetlist, tlist);
745 * Can't handle FOR UPDATE/SHARE here (parser should have checked
746 * already, but let's make sure).
750 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
751 errmsg("SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT")));
754 * Calculate pathkeys that represent result ordering requirements
756 sort_pathkeys = make_pathkeys_for_sortclauses(root,
763 /* No set operations, do regular planning */
765 List *group_pathkeys;
766 AttrNumber *groupColIdx = NULL;
767 Oid *groupOperators = NULL;
768 bool need_tlist_eval = true;
774 AggClauseCounts agg_counts;
775 int numGroupCols = list_length(parse->groupClause);
776 bool use_hashed_grouping = false;
778 MemSet(&agg_counts, 0, sizeof(AggClauseCounts));
780 /* Preprocess targetlist */
781 tlist = preprocess_targetlist(root, tlist);
784 * Generate appropriate target list for subplan; may be different from
785 * tlist if grouping or aggregation is needed.
787 sub_tlist = make_subplanTargetList(root, tlist,
788 &groupColIdx, &need_tlist_eval);
791 * Calculate pathkeys that represent grouping/ordering requirements.
792 * Stash them in PlannerInfo so that query_planner can canonicalize
793 * them after EquivalenceClasses have been formed.
795 root->group_pathkeys =
796 make_pathkeys_for_sortclauses(root,
800 root->sort_pathkeys =
801 make_pathkeys_for_sortclauses(root,
807 * Will need actual number of aggregates for estimating costs.
809 * Note: we do not attempt to detect duplicate aggregates here; a
810 * somewhat-overestimated count is okay for our present purposes.
812 * Note: think not that we can turn off hasAggs if we find no aggs. It
813 * is possible for constant-expression simplification to remove all
814 * explicit references to aggs, but we still have to follow the
815 * aggregate semantics (eg, producing only one output row).
819 count_agg_clauses((Node *) tlist, &agg_counts);
820 count_agg_clauses(parse->havingQual, &agg_counts);
824 * Figure out whether we need a sorted result from query_planner.
826 * If we have a GROUP BY clause, then we want a result sorted properly
827 * for grouping. Otherwise, if there is an ORDER BY clause, we want
828 * to sort by the ORDER BY clause. (Note: if we have both, and ORDER
829 * BY is a superset of GROUP BY, it would be tempting to request sort
830 * by ORDER BY --- but that might just leave us failing to exploit an
831 * available sort order at all. Needs more thought...)
833 if (parse->groupClause)
834 root->query_pathkeys = root->group_pathkeys;
835 else if (parse->sortClause)
836 root->query_pathkeys = root->sort_pathkeys;
838 root->query_pathkeys = NIL;
841 * Generate the best unsorted and presorted paths for this Query (but
842 * note there may not be any presorted path). query_planner will also
843 * estimate the number of groups in the query, and canonicalize all
846 query_planner(root, sub_tlist, tuple_fraction,
847 &cheapest_path, &sorted_path, &dNumGroups);
849 group_pathkeys = root->group_pathkeys;
850 sort_pathkeys = root->sort_pathkeys;
853 * If grouping, extract the grouping operators and decide whether we
854 * want to use hashed grouping.
856 if (parse->groupClause)
858 groupOperators = extract_grouping_ops(parse->groupClause);
859 use_hashed_grouping =
860 choose_hashed_grouping(root, tuple_fraction,
861 cheapest_path, sorted_path,
862 groupOperators, dNumGroups,
865 /* Also convert # groups to long int --- but 'ware overflow! */
866 numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
870 * Select the best path. If we are doing hashed grouping, we will
871 * always read all the input tuples, so use the cheapest-total path.
872 * Otherwise, trust query_planner's decision about which to use.
874 if (use_hashed_grouping || !sorted_path)
875 best_path = cheapest_path;
877 best_path = sorted_path;
880 * Check to see if it's possible to optimize MIN/MAX aggregates. If
881 * so, we will forget all the work we did so far to choose a "regular"
882 * path ... but we had to do it anyway to be able to tell which way is
885 result_plan = optimize_minmax_aggregates(root,
888 if (result_plan != NULL)
891 * optimize_minmax_aggregates generated the full plan, with the
892 * right tlist, and it has no sort order.
894 current_pathkeys = NIL;
899 * Normal case --- create a plan according to query_planner's
902 result_plan = create_plan(root, best_path);
903 current_pathkeys = best_path->pathkeys;
906 * create_plan() returns a plan with just a "flat" tlist of
907 * required Vars. Usually we need to insert the sub_tlist as the
908 * tlist of the top plan node. However, we can skip that if we
909 * determined that whatever query_planner chose to return will be
915 * If the top-level plan node is one that cannot do expression
916 * evaluation, we must insert a Result node to project the
919 if (!is_projection_capable_plan(result_plan))
921 result_plan = (Plan *) make_result(root,
929 * Otherwise, just replace the subplan's flat tlist with
932 result_plan->targetlist = sub_tlist;
936 * Also, account for the cost of evaluation of the sub_tlist.
938 * Up to now, we have only been dealing with "flat" tlists,
939 * containing just Vars. So their evaluation cost is zero
940 * according to the model used by cost_qual_eval() (or if you
941 * prefer, the cost is factored into cpu_tuple_cost). Thus we
942 * can avoid accounting for tlist cost throughout
943 * query_planner() and subroutines. But now we've inserted a
944 * tlist that might contain actual operators, sub-selects, etc
945 * --- so we'd better account for its cost.
947 * Below this point, any tlist eval cost for added-on nodes
948 * should be accounted for as we create those nodes.
949 * Presently, of the node types we can add on, only Agg and
950 * Group project new tlists (the rest just copy their input
951 * tuples) --- so make_agg() and make_group() are responsible
952 * for computing the added cost.
954 cost_qual_eval(&tlist_cost, sub_tlist, root);
955 result_plan->startup_cost += tlist_cost.startup;
956 result_plan->total_cost += tlist_cost.startup +
957 tlist_cost.per_tuple * result_plan->plan_rows;
962 * Since we're using query_planner's tlist and not the one
963 * make_subplanTargetList calculated, we have to refigure any
964 * grouping-column indexes make_subplanTargetList computed.
966 locate_grouping_columns(root, tlist, result_plan->targetlist,
971 * Insert AGG or GROUP node if needed, plus an explicit sort step
974 * HAVING clause, if any, becomes qual of the Agg or Group node.
976 if (use_hashed_grouping)
978 /* Hashed aggregate plan --- no sort needed */
979 result_plan = (Plan *) make_agg(root,
981 (List *) parse->havingQual,
989 /* Hashed aggregation produces randomly-ordered results */
990 current_pathkeys = NIL;
992 else if (parse->hasAggs)
994 /* Plain aggregate plan --- sort if needed */
995 AggStrategy aggstrategy;
997 if (parse->groupClause)
999 if (!pathkeys_contained_in(group_pathkeys,
1002 result_plan = (Plan *)
1003 make_sort_from_groupcols(root,
1007 current_pathkeys = group_pathkeys;
1009 aggstrategy = AGG_SORTED;
1012 * The AGG node will not change the sort ordering of its
1013 * groups, so current_pathkeys describes the result too.
1018 aggstrategy = AGG_PLAIN;
1019 /* Result will be only one row anyway; no sort order */
1020 current_pathkeys = NIL;
1023 result_plan = (Plan *) make_agg(root,
1025 (List *) parse->havingQual,
1034 else if (parse->groupClause)
1037 * GROUP BY without aggregation, so insert a group node (plus
1038 * the appropriate sort node, if necessary).
1040 * Add an explicit sort if we couldn't make the path come out
1041 * the way the GROUP node needs it.
1043 if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
1045 result_plan = (Plan *)
1046 make_sort_from_groupcols(root,
1050 current_pathkeys = group_pathkeys;
1053 result_plan = (Plan *) make_group(root,
1055 (List *) parse->havingQual,
1061 /* The Group node won't change sort ordering */
1063 else if (root->hasHavingQual)
1066 * No aggregates, and no GROUP BY, but we have a HAVING qual.
1067 * This is a degenerate case in which we are supposed to emit
1068 * either 0 or 1 row depending on whether HAVING succeeds.
1069 * Furthermore, there cannot be any variables in either HAVING
1070 * or the targetlist, so we actually do not need the FROM
1071 * table at all! We can just throw away the plan-so-far and
1072 * generate a Result node. This is a sufficiently unusual
1073 * corner case that it's not worth contorting the structure of
1074 * this routine to avoid having to generate the plan in the
1077 result_plan = (Plan *) make_result(root,
1082 } /* end of non-minmax-aggregate case */
1083 } /* end of if (setOperations) */
1086 * If we were not able to make the plan come out in the right order, add
1087 * an explicit sort step.
1089 if (parse->sortClause)
1091 if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
1093 result_plan = (Plan *) make_sort_from_pathkeys(root,
1096 current_pathkeys = sort_pathkeys;
1101 * If there is a DISTINCT clause, add the UNIQUE node.
1103 if (parse->distinctClause)
1105 result_plan = (Plan *) make_unique(result_plan, parse->distinctClause);
1108 * If there was grouping or aggregation, leave plan_rows as-is (ie,
1109 * assume the result was already mostly unique). If not, use the
1110 * number of distinct-groups calculated by query_planner.
1112 if (!parse->groupClause && !root->hasHavingQual && !parse->hasAggs)
1113 result_plan->plan_rows = dNumGroups;
1117 * Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
1119 if (parse->limitCount || parse->limitOffset)
1121 result_plan = (Plan *) make_limit(result_plan,
1129 * Deal with the RETURNING clause if any. It's convenient to pass the
1130 * returningList through setrefs.c now rather than at top level (if we
1131 * waited, handling inherited UPDATE/DELETE would be much harder).
1133 if (parse->returningList)
1137 Assert(parse->resultRelation);
1138 rlist = set_returning_clause_references(parse->returningList,
1140 parse->resultRelation);
1141 root->returningLists = list_make1(rlist);
1144 root->returningLists = NIL;
1146 /* Compute result-relations list if needed */
1147 if (parse->resultRelation)
1148 root->resultRelations = list_make1_int(parse->resultRelation);
1150 root->resultRelations = NIL;
1153 * Return the actual output ordering in query_pathkeys for possible use by
1154 * an outer query level.
1156 root->query_pathkeys = current_pathkeys;
1162 * Detect whether a plan node is a "dummy" plan created when a relation
1163 * is deemed not to need scanning due to constraint exclusion.
1165 * Currently, such dummy plans are Result nodes with constant FALSE
1169 is_dummy_plan(Plan *plan)
1171 if (IsA(plan, Result))
1173 List *rcqual = (List *) ((Result *) plan)->resconstantqual;
1175 if (list_length(rcqual) == 1)
1177 Const *constqual = (Const *) linitial(rcqual);
1179 if (constqual && IsA(constqual, Const))
1181 if (!constqual->constisnull &&
1182 !DatumGetBool(constqual->constvalue))
1191 * preprocess_limit - do pre-estimation for LIMIT and/or OFFSET clauses
1193 * We try to estimate the values of the LIMIT/OFFSET clauses, and pass the
1194 * results back in *count_est and *offset_est. These variables are set to
1195 * 0 if the corresponding clause is not present, and -1 if it's present
1196 * but we couldn't estimate the value for it. (The "0" convention is OK
1197 * for OFFSET but a little bit bogus for LIMIT: effectively we estimate
1198 * LIMIT 0 as though it were LIMIT 1. But this is in line with the planner's
1199 * usual practice of never estimating less than one row.) These values will
1200 * be passed to make_limit, which see if you change this code.
1202 * The return value is the suitably adjusted tuple_fraction to use for
1203 * planning the query. This adjustment is not overridable, since it reflects
1204 * plan actions that grouping_planner() will certainly take, not assumptions
1208 preprocess_limit(PlannerInfo *root, double tuple_fraction,
1209 int64 *offset_est, int64 *count_est)
1211 Query *parse = root->parse;
1213 double limit_fraction;
1215 /* Should not be called unless LIMIT or OFFSET */
1216 Assert(parse->limitCount || parse->limitOffset);
1219 * Try to obtain the clause values. We use estimate_expression_value
1220 * primarily because it can sometimes do something useful with Params.
1222 if (parse->limitCount)
1224 est = estimate_expression_value(root, parse->limitCount);
1225 if (est && IsA(est, Const))
1227 if (((Const *) est)->constisnull)
1229 /* NULL indicates LIMIT ALL, ie, no limit */
1230 *count_est = 0; /* treat as not present */
1234 *count_est = DatumGetInt64(((Const *) est)->constvalue);
1235 if (*count_est <= 0)
1236 *count_est = 1; /* force to at least 1 */
1240 *count_est = -1; /* can't estimate */
1243 *count_est = 0; /* not present */
1245 if (parse->limitOffset)
1247 est = estimate_expression_value(root, parse->limitOffset);
1248 if (est && IsA(est, Const))
1250 if (((Const *) est)->constisnull)
1252 /* Treat NULL as no offset; the executor will too */
1253 *offset_est = 0; /* treat as not present */
1257 *offset_est = DatumGetInt64(((Const *) est)->constvalue);
1258 if (*offset_est < 0)
1259 *offset_est = 0; /* less than 0 is same as 0 */
1263 *offset_est = -1; /* can't estimate */
1266 *offset_est = 0; /* not present */
1268 if (*count_est != 0)
1271 * A LIMIT clause limits the absolute number of tuples returned.
1272 * However, if it's not a constant LIMIT then we have to guess; for
1273 * lack of a better idea, assume 10% of the plan's result is wanted.
1275 if (*count_est < 0 || *offset_est < 0)
1277 /* LIMIT or OFFSET is an expression ... punt ... */
1278 limit_fraction = 0.10;
1282 /* LIMIT (plus OFFSET, if any) is max number of tuples needed */
1283 limit_fraction = (double) *count_est + (double) *offset_est;
1287 * If we have absolute limits from both caller and LIMIT, use the
1288 * smaller value; likewise if they are both fractional. If one is
1289 * fractional and the other absolute, we can't easily determine which
1290 * is smaller, but we use the heuristic that the absolute will usually
1293 if (tuple_fraction >= 1.0)
1295 if (limit_fraction >= 1.0)
1298 tuple_fraction = Min(tuple_fraction, limit_fraction);
1302 /* caller absolute, limit fractional; use caller's value */
1305 else if (tuple_fraction > 0.0)
1307 if (limit_fraction >= 1.0)
1309 /* caller fractional, limit absolute; use limit */
1310 tuple_fraction = limit_fraction;
1314 /* both fractional */
1315 tuple_fraction = Min(tuple_fraction, limit_fraction);
1320 /* no info from caller, just use limit */
1321 tuple_fraction = limit_fraction;
1324 else if (*offset_est != 0 && tuple_fraction > 0.0)
1327 * We have an OFFSET but no LIMIT. This acts entirely differently
1328 * from the LIMIT case: here, we need to increase rather than decrease
1329 * the caller's tuple_fraction, because the OFFSET acts to cause more
1330 * tuples to be fetched instead of fewer. This only matters if we got
1331 * a tuple_fraction > 0, however.
1333 * As above, use 10% if OFFSET is present but unestimatable.
1335 if (*offset_est < 0)
1336 limit_fraction = 0.10;
1338 limit_fraction = (double) *offset_est;
1341 * If we have absolute counts from both caller and OFFSET, add them
1342 * together; likewise if they are both fractional. If one is
1343 * fractional and the other absolute, we want to take the larger, and
1344 * we heuristically assume that's the fractional one.
1346 if (tuple_fraction >= 1.0)
1348 if (limit_fraction >= 1.0)
1350 /* both absolute, so add them together */
1351 tuple_fraction += limit_fraction;
1355 /* caller absolute, limit fractional; use limit */
1356 tuple_fraction = limit_fraction;
1361 if (limit_fraction >= 1.0)
1363 /* caller fractional, limit absolute; use caller's value */
1367 /* both fractional, so add them together */
1368 tuple_fraction += limit_fraction;
1369 if (tuple_fraction >= 1.0)
1370 tuple_fraction = 0.0; /* assume fetch all */
1375 return tuple_fraction;
1379 * extract_grouping_ops - make an array of the equality operator OIDs
1380 * for the GROUP BY clause
1383 extract_grouping_ops(List *groupClause)
1385 int numCols = list_length(groupClause);
1387 Oid *groupOperators;
1390 groupOperators = (Oid *) palloc(sizeof(Oid) * numCols);
1392 foreach(glitem, groupClause)
1394 GroupClause *groupcl = (GroupClause *) lfirst(glitem);
1396 groupOperators[colno] = get_equality_op_for_ordering_op(groupcl->sortop);
1397 if (!OidIsValid(groupOperators[colno])) /* shouldn't happen */
1398 elog(ERROR, "could not find equality operator for ordering operator %u",
1403 return groupOperators;
1407 * choose_hashed_grouping - should we use hashed grouping?
1410 choose_hashed_grouping(PlannerInfo *root, double tuple_fraction,
1411 Path *cheapest_path, Path *sorted_path,
1412 Oid *groupOperators, double dNumGroups,
1413 AggClauseCounts *agg_counts)
1415 int numGroupCols = list_length(root->parse->groupClause);
1416 double cheapest_path_rows;
1417 int cheapest_path_width;
1419 List *current_pathkeys;
1425 * Check can't-do-it conditions, including whether the grouping operators
1426 * are hashjoinable. (We assume hashing is OK if they are marked
1427 * oprcanhash. If there isn't actually a supporting hash function,
1428 * the executor will complain at runtime.)
1430 * Executor doesn't support hashed aggregation with DISTINCT aggregates.
1431 * (Doing so would imply storing *all* the input values in the hash table,
1432 * which seems like a certain loser.)
1434 if (!enable_hashagg)
1436 if (agg_counts->numDistinctAggs != 0)
1438 for (i = 0; i < numGroupCols; i++)
1440 if (!op_hashjoinable(groupOperators[i]))
1445 * Don't do it if it doesn't look like the hashtable will fit into
1448 * Beware here of the possibility that cheapest_path->parent is NULL. This
1449 * could happen if user does something silly like SELECT 'foo' GROUP BY 1;
1451 if (cheapest_path->parent)
1453 cheapest_path_rows = cheapest_path->parent->rows;
1454 cheapest_path_width = cheapest_path->parent->width;
1458 cheapest_path_rows = 1; /* assume non-set result */
1459 cheapest_path_width = 100; /* arbitrary */
1462 /* Estimate per-hash-entry space at tuple width... */
1463 hashentrysize = MAXALIGN(cheapest_path_width) + MAXALIGN(sizeof(MinimalTupleData));
1464 /* plus space for pass-by-ref transition values... */
1465 hashentrysize += agg_counts->transitionSpace;
1466 /* plus the per-hash-entry overhead */
1467 hashentrysize += hash_agg_entry_size(agg_counts->numAggs);
1469 if (hashentrysize * dNumGroups > work_mem * 1024L)
1473 * See if the estimated cost is no more than doing it the other way. While
1474 * avoiding the need for sorted input is usually a win, the fact that the
1475 * output won't be sorted may be a loss; so we need to do an actual cost
1478 * We need to consider cheapest_path + hashagg [+ final sort] versus
1479 * either cheapest_path [+ sort] + group or agg [+ final sort] or
1480 * presorted_path + group or agg [+ final sort] where brackets indicate a
1481 * step that may not be needed. We assume query_planner() will have
1482 * returned a presorted path only if it's a winner compared to
1483 * cheapest_path for this purpose.
1485 * These path variables are dummies that just hold cost fields; we don't
1486 * make actual Paths for these steps.
1488 cost_agg(&hashed_p, root, AGG_HASHED, agg_counts->numAggs,
1489 numGroupCols, dNumGroups,
1490 cheapest_path->startup_cost, cheapest_path->total_cost,
1491 cheapest_path_rows);
1492 /* Result of hashed agg is always unsorted */
1493 if (root->sort_pathkeys)
1494 cost_sort(&hashed_p, root, root->sort_pathkeys, hashed_p.total_cost,
1495 dNumGroups, cheapest_path_width);
1499 sorted_p.startup_cost = sorted_path->startup_cost;
1500 sorted_p.total_cost = sorted_path->total_cost;
1501 current_pathkeys = sorted_path->pathkeys;
1505 sorted_p.startup_cost = cheapest_path->startup_cost;
1506 sorted_p.total_cost = cheapest_path->total_cost;
1507 current_pathkeys = cheapest_path->pathkeys;
1509 if (!pathkeys_contained_in(root->group_pathkeys, current_pathkeys))
1511 cost_sort(&sorted_p, root, root->group_pathkeys, sorted_p.total_cost,
1512 cheapest_path_rows, cheapest_path_width);
1513 current_pathkeys = root->group_pathkeys;
1516 if (root->parse->hasAggs)
1517 cost_agg(&sorted_p, root, AGG_SORTED, agg_counts->numAggs,
1518 numGroupCols, dNumGroups,
1519 sorted_p.startup_cost, sorted_p.total_cost,
1520 cheapest_path_rows);
1522 cost_group(&sorted_p, root, numGroupCols, dNumGroups,
1523 sorted_p.startup_cost, sorted_p.total_cost,
1524 cheapest_path_rows);
1525 /* The Agg or Group node will preserve ordering */
1526 if (root->sort_pathkeys &&
1527 !pathkeys_contained_in(root->sort_pathkeys, current_pathkeys))
1528 cost_sort(&sorted_p, root, root->sort_pathkeys, sorted_p.total_cost,
1529 dNumGroups, cheapest_path_width);
1532 * Now make the decision using the top-level tuple fraction. First we
1533 * have to convert an absolute count (LIMIT) into fractional form.
1535 if (tuple_fraction >= 1.0)
1536 tuple_fraction /= dNumGroups;
1538 if (compare_fractional_path_costs(&hashed_p, &sorted_p,
1539 tuple_fraction) < 0)
1541 /* Hashed is cheaper, so use it */
1548 * make_subplanTargetList
1549 * Generate appropriate target list when grouping is required.
1551 * When grouping_planner inserts Aggregate, Group, or Result plan nodes
1552 * above the result of query_planner, we typically want to pass a different
1553 * target list to query_planner than the outer plan nodes should have.
1554 * This routine generates the correct target list for the subplan.
1556 * The initial target list passed from the parser already contains entries
1557 * for all ORDER BY and GROUP BY expressions, but it will not have entries
1558 * for variables used only in HAVING clauses; so we need to add those
1559 * variables to the subplan target list. Also, we flatten all expressions
1560 * except GROUP BY items into their component variables; the other expressions
1561 * will be computed by the inserted nodes rather than by the subplan.
1562 * For example, given a query like
1563 * SELECT a+b,SUM(c+d) FROM table GROUP BY a+b;
1564 * we want to pass this targetlist to the subplan:
1566 * where the a+b target will be used by the Sort/Group steps, and the
1567 * other targets will be used for computing the final results. (In the
1568 * above example we could theoretically suppress the a and b targets and
1569 * pass down only c,d,a+b, but it's not really worth the trouble to
1570 * eliminate simple var references from the subplan. We will avoid doing
1571 * the extra computation to recompute a+b at the outer level; see
1572 * fix_upper_expr() in setrefs.c.)
1574 * If we are grouping or aggregating, *and* there are no non-Var grouping
1575 * expressions, then the returned tlist is effectively dummy; we do not
1576 * need to force it to be evaluated, because all the Vars it contains
1577 * should be present in the output of query_planner anyway.
1579 * 'tlist' is the query's target list.
1580 * 'groupColIdx' receives an array of column numbers for the GROUP BY
1581 * expressions (if there are any) in the subplan's target list.
1582 * 'need_tlist_eval' is set true if we really need to evaluate the
1585 * The result is the targetlist to be passed to the subplan.
1589 make_subplanTargetList(PlannerInfo *root,
1591 AttrNumber **groupColIdx,
1592 bool *need_tlist_eval)
1594 Query *parse = root->parse;
1599 *groupColIdx = NULL;
1602 * If we're not grouping or aggregating, there's nothing to do here;
1603 * query_planner should receive the unmodified target list.
1605 if (!parse->hasAggs && !parse->groupClause && !root->hasHavingQual)
1607 *need_tlist_eval = true;
1612 * Otherwise, start with a "flattened" tlist (having just the vars
1613 * mentioned in the targetlist and HAVING qual --- but not upper- level
1614 * Vars; they will be replaced by Params later on).
1616 sub_tlist = flatten_tlist(tlist);
1617 extravars = pull_var_clause(parse->havingQual, false);
1618 sub_tlist = add_to_flat_tlist(sub_tlist, extravars);
1619 list_free(extravars);
1620 *need_tlist_eval = false; /* only eval if not flat tlist */
1623 * If grouping, create sub_tlist entries for all GROUP BY expressions
1624 * (GROUP BY items that are simple Vars should be in the list already),
1625 * and make an array showing where the group columns are in the sub_tlist.
1627 numCols = list_length(parse->groupClause);
1631 AttrNumber *grpColIdx;
1634 grpColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
1635 *groupColIdx = grpColIdx;
1637 foreach(gl, parse->groupClause)
1639 GroupClause *grpcl = (GroupClause *) lfirst(gl);
1640 Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1641 TargetEntry *te = NULL;
1644 /* Find or make a matching sub_tlist entry */
1645 foreach(sl, sub_tlist)
1647 te = (TargetEntry *) lfirst(sl);
1648 if (equal(groupexpr, te->expr))
1653 te = makeTargetEntry((Expr *) groupexpr,
1654 list_length(sub_tlist) + 1,
1657 sub_tlist = lappend(sub_tlist, te);
1658 *need_tlist_eval = true; /* it's not flat anymore */
1661 /* and save its resno */
1662 grpColIdx[keyno++] = te->resno;
1670 * locate_grouping_columns
1671 * Locate grouping columns in the tlist chosen by query_planner.
1673 * This is only needed if we don't use the sub_tlist chosen by
1674 * make_subplanTargetList. We have to forget the column indexes found
1675 * by that routine and re-locate the grouping vars in the real sub_tlist.
1678 locate_grouping_columns(PlannerInfo *root,
1681 AttrNumber *groupColIdx)
1687 * No work unless grouping.
1689 if (!root->parse->groupClause)
1691 Assert(groupColIdx == NULL);
1694 Assert(groupColIdx != NULL);
1696 foreach(gl, root->parse->groupClause)
1698 GroupClause *grpcl = (GroupClause *) lfirst(gl);
1699 Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1700 TargetEntry *te = NULL;
1703 foreach(sl, sub_tlist)
1705 te = (TargetEntry *) lfirst(sl);
1706 if (equal(groupexpr, te->expr))
1710 elog(ERROR, "failed to locate grouping columns");
1712 groupColIdx[keyno++] = te->resno;
1717 * postprocess_setop_tlist
1718 * Fix up targetlist returned by plan_set_operations().
1720 * We need to transpose sort key info from the orig_tlist into new_tlist.
1721 * NOTE: this would not be good enough if we supported resjunk sort keys
1722 * for results of set operations --- then, we'd need to project a whole
1723 * new tlist to evaluate the resjunk columns. For now, just ereport if we
1724 * find any resjunk columns in orig_tlist.
1727 postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
1730 ListCell *orig_tlist_item = list_head(orig_tlist);
1732 foreach(l, new_tlist)
1734 TargetEntry *new_tle = (TargetEntry *) lfirst(l);
1735 TargetEntry *orig_tle;
1737 /* ignore resjunk columns in setop result */
1738 if (new_tle->resjunk)
1741 Assert(orig_tlist_item != NULL);
1742 orig_tle = (TargetEntry *) lfirst(orig_tlist_item);
1743 orig_tlist_item = lnext(orig_tlist_item);
1744 if (orig_tle->resjunk) /* should not happen */
1745 elog(ERROR, "resjunk output columns are not implemented");
1746 Assert(new_tle->resno == orig_tle->resno);
1747 new_tle->ressortgroupref = orig_tle->ressortgroupref;
1749 if (orig_tlist_item != NULL)
1750 elog(ERROR, "resjunk output columns are not implemented");