granicus.if.org Git - postgresql/blob - src/backend/optimizer/plan/planner.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * planner.c
   4  *        The query optimizer external interface.
   5  *
   6  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.236 2008/08/02 21:32:00 tgl Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 #include "postgres.h"
  17
  18 #include <limits.h>
  19
  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"
  37 #endif
  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"
  43
  44
  45 /* GUC parameter */
  46 double cursor_tuple_fraction = DEFAULT_CURSOR_TUPLE_FRACTION;
  47
  48 /* Hook for plugins to get control in planner() */
  49 planner_hook_type planner_hook = NULL;
  50
  51
  52 /* Expression kind codes for preprocess_expression */
  53 #define EXPRKIND_QUAL           0
  54 #define EXPRKIND_TARGET         1
  55 #define EXPRKIND_RTFUNC         2
  56 #define EXPRKIND_VALUES         3
  57 #define EXPRKIND_LIMIT          4
  58 #define EXPRKIND_ININFO         5
  59 #define EXPRKIND_APPINFO        6
  60
  61
  62 static Node *preprocess_expression(PlannerInfo *root, Node *expr, int kind);
  63 static void preprocess_qual_conditions(PlannerInfo *root, Node *jtnode);
  64 static Plan *inheritance_planner(PlannerInfo *root);
  65 static Plan *grouping_planner(PlannerInfo *root, double tuple_fraction);
  66 static bool is_dummy_plan(Plan *plan);
  67 static double preprocess_limit(PlannerInfo *root,
  68                                  double tuple_fraction,
  69                                  int64 *offset_est, int64 *count_est);
  70 static void preprocess_groupclause(PlannerInfo *root);
  71 static Oid *extract_grouping_ops(List *groupClause);
  72 static bool choose_hashed_grouping(PlannerInfo *root,
  73                                            double tuple_fraction, double limit_tuples,
  74                                            Path *cheapest_path, Path *sorted_path,
  75                                            Oid *groupOperators, double dNumGroups,
  76                                            AggClauseCounts *agg_counts);
  77 static List *make_subplanTargetList(PlannerInfo *root, List *tlist,
  78                                            AttrNumber **groupColIdx, bool *need_tlist_eval);
  79 static void locate_grouping_columns(PlannerInfo *root,
  80                                                 List *tlist,
  81                                                 List *sub_tlist,
  82                                                 AttrNumber *groupColIdx);
  83 static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
  84
  85
  86 /*****************************************************************************
  87  *
  88  *         Query optimizer entry point
  89  *
  90  * To support loadable plugins that monitor or modify planner behavior,
  91  * we provide a hook variable that lets a plugin get control before and
  92  * after the standard planning process.  The plugin would normally call
  93  * standard_planner().
  94  *
  95  * Note to plugin authors: standard_planner() scribbles on its Query input,
  96  * so you'd better copy that data structure if you want to plan more than once.
  97  *
  98  *****************************************************************************/
  99 PlannedStmt *
 100 planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 101 {
 102         PlannedStmt *result;
 103
 104         if (planner_hook)
 105                 result = (*planner_hook) (parse, cursorOptions, boundParams);
 106         else
 107                 result = standard_planner(parse, cursorOptions, boundParams);
 108         return result;
 109 }
 110
 111 PlannedStmt *
 112 standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 113 {
 114         PlannedStmt *result;
 115         PlannerGlobal *glob;
 116         double          tuple_fraction;
 117         PlannerInfo *root;
 118         Plan       *top_plan;
 119         ListCell   *lp,
 120                            *lr;
 121
 122         /* Cursor options may come from caller or from DECLARE CURSOR stmt */
 123         if (parse->utilityStmt &&
 124                 IsA(parse->utilityStmt, DeclareCursorStmt))
 125                 cursorOptions |= ((DeclareCursorStmt *) parse->utilityStmt)->options;
 126
 127         /*
 128          * Set up global state for this planner invocation.  This data is needed
 129          * across all levels of sub-Query that might exist in the given command,
 130          * so we keep it in a separate struct that's linked to by each per-Query
 131          * PlannerInfo.
 132          */
 133         glob = makeNode(PlannerGlobal);
 134
 135         glob->boundParams = boundParams;
 136         glob->paramlist = NIL;
 137         glob->subplans = NIL;
 138         glob->subrtables = NIL;
 139         glob->rewindPlanIDs = NULL;
 140         glob->finalrtable = NIL;
 141         glob->relationOids = NIL;
 142         glob->transientPlan = false;
 143
 144         /* Determine what fraction of the plan is likely to be scanned */
 145         if (cursorOptions & CURSOR_OPT_FAST_PLAN)
 146         {
 147                 /*
 148                  * We have no real idea how many tuples the user will ultimately FETCH
 149                  * from a cursor, but it is often the case that he doesn't want 'em
 150                  * all, or would prefer a fast-start plan anyway so that he can
 151                  * process some of the tuples sooner.  Use a GUC parameter to decide
 152                  * what fraction to optimize for.
 153                  */
 154                 tuple_fraction = cursor_tuple_fraction;
 155
 156                 /*
 157                  * We document cursor_tuple_fraction as simply being a fraction,
 158                  * which means the edge cases 0 and 1 have to be treated specially
 159                  * here.  We convert 1 to 0 ("all the tuples") and 0 to a very small
 160                  * fraction.
 161                  */
 162                 if (tuple_fraction >= 1.0)
 163                         tuple_fraction = 0.0;
 164                 else if (tuple_fraction <= 0.0)
 165                         tuple_fraction = 1e-10;
 166         }
 167         else
 168         {
 169                 /* Default assumption is we need all the tuples */
 170                 tuple_fraction = 0.0;
 171         }
 172
 173         /* primary planning entry point (may recurse for subqueries) */
 174         top_plan = subquery_planner(glob, parse, 1, tuple_fraction, &root);
 175
 176         /*
 177          * If creating a plan for a scrollable cursor, make sure it can run
 178          * backwards on demand.  Add a Material node at the top at need.
 179          */
 180         if (cursorOptions & CURSOR_OPT_SCROLL)
 181         {
 182                 if (!ExecSupportsBackwardScan(top_plan))
 183                         top_plan = materialize_finished_plan(top_plan);
 184         }
 185
 186         /* final cleanup of the plan */
 187         Assert(glob->finalrtable == NIL);
 188         top_plan = set_plan_references(glob, top_plan, root->parse->rtable);
 189         /* ... and the subplans (both regular subplans and initplans) */
 190         Assert(list_length(glob->subplans) == list_length(glob->subrtables));
 191         forboth(lp, glob->subplans, lr, glob->subrtables)
 192         {
 193                 Plan       *subplan = (Plan *) lfirst(lp);
 194                 List       *subrtable = (List *) lfirst(lr);
 195
 196                 lfirst(lp) = set_plan_references(glob, subplan, subrtable);
 197         }
 198
 199         /* build the PlannedStmt result */
 200         result = makeNode(PlannedStmt);
 201
 202         result->commandType = parse->commandType;
 203         result->canSetTag = parse->canSetTag;
 204         result->transientPlan = glob->transientPlan;
 205         result->planTree = top_plan;
 206         result->rtable = glob->finalrtable;
 207         result->resultRelations = root->resultRelations;
 208         result->utilityStmt = parse->utilityStmt;
 209         result->intoClause = parse->intoClause;
 210         result->subplans = glob->subplans;
 211         result->rewindPlanIDs = glob->rewindPlanIDs;
 212         result->returningLists = root->returningLists;
 213         result->rowMarks = parse->rowMarks;
 214         result->relationOids = glob->relationOids;
 215         result->nParamExec = list_length(glob->paramlist);
 216
 217         return result;
 218 }
 219
 220
 221 /*--------------------
 222  * subquery_planner
 223  *        Invokes the planner on a subquery.  We recurse to here for each
 224  *        sub-SELECT found in the query tree.
 225  *
 226  * glob is the global state for the current planner run.
 227  * parse is the querytree produced by the parser & rewriter.
 228  * level is the current recursion depth (1 at the top-level Query).
 229  * tuple_fraction is the fraction of tuples we expect will be retrieved.
 230  * tuple_fraction is interpreted as explained for grouping_planner, below.
 231  *
 232  * If subroot isn't NULL, we pass back the query's final PlannerInfo struct;
 233  * among other things this tells the output sort ordering of the plan.
 234  *
 235  * Basically, this routine does the stuff that should only be done once
 236  * per Query object.  It then calls grouping_planner.  At one time,
 237  * grouping_planner could be invoked recursively on the same Query object;
 238  * that's not currently true, but we keep the separation between the two
 239  * routines anyway, in case we need it again someday.
 240  *
 241  * subquery_planner will be called recursively to handle sub-Query nodes
 242  * found within the query's expressions and rangetable.
 243  *
 244  * Returns a query plan.
 245  *--------------------
 246  */
 247 Plan *
 248 subquery_planner(PlannerGlobal *glob, Query *parse,
 249                                  Index level, double tuple_fraction,
 250                                  PlannerInfo **subroot)
 251 {
 252         int                     num_old_subplans = list_length(glob->subplans);
 253         PlannerInfo *root;
 254         Plan       *plan;
 255         List       *newHaving;
 256         ListCell   *l;
 257
 258         /* Create a PlannerInfo data structure for this subquery */
 259         root = makeNode(PlannerInfo);
 260         root->parse = parse;
 261         root->glob = glob;
 262         root->query_level = level;
 263         root->planner_cxt = CurrentMemoryContext;
 264         root->init_plans = NIL;
 265         root->eq_classes = NIL;
 266         root->in_info_list = NIL;
 267         root->append_rel_list = NIL;
 268
 269         /*
 270          * Look for IN clauses at the top level of WHERE, and transform them into
 271          * joins.  Note that this step only handles IN clauses originally at top
 272          * level of WHERE; if we pull up any subqueries below, their INs are
 273          * processed just before pulling them up.
 274          */
 275         if (parse->hasSubLinks)
 276                 parse->jointree->quals = pull_up_IN_clauses(root,
 277                                                                                                         parse->jointree->quals);
 278
 279         /*
 280          * Scan the rangetable for set-returning functions, and inline them
 281          * if possible (producing subqueries that might get pulled up next).
 282          * Recursion issues here are handled in the same way as for IN clauses.
 283          */
 284         inline_set_returning_functions(root);
 285
 286         /*
 287          * Check to see if any subqueries in the rangetable can be merged into
 288          * this query.
 289          */
 290         parse->jointree = (FromExpr *)
 291                 pull_up_subqueries(root, (Node *) parse->jointree, false, false);
 292
 293         /*
 294          * Detect whether any rangetable entries are RTE_JOIN kind; if not, we can
 295          * avoid the expense of doing flatten_join_alias_vars().  Also check for
 296          * outer joins --- if none, we can skip reduce_outer_joins() and some
 297          * other processing.  This must be done after we have done
 298          * pull_up_subqueries, of course.
 299          *
 300          * Note: if reduce_outer_joins manages to eliminate all outer joins,
 301          * root->hasOuterJoins is not reset currently.  This is OK since its
 302          * purpose is merely to suppress unnecessary processing in simple cases.
 303          */
 304         root->hasJoinRTEs = false;
 305         root->hasOuterJoins = false;
 306         foreach(l, parse->rtable)
 307         {
 308                 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 309
 310                 if (rte->rtekind == RTE_JOIN)
 311                 {
 312                         root->hasJoinRTEs = true;
 313                         if (IS_OUTER_JOIN(rte->jointype))
 314                         {
 315                                 root->hasOuterJoins = true;
 316                                 /* Can quit scanning once we find an outer join */
 317                                 break;
 318                         }
 319                 }
 320         }
 321
 322         /*
 323          * Expand any rangetable entries that are inheritance sets into "append
 324          * relations".  This can add entries to the rangetable, but they must be
 325          * plain base relations not joins, so it's OK (and marginally more
 326          * efficient) to do it after checking for join RTEs.  We must do it after
 327          * pulling up subqueries, else we'd fail to handle inherited tables in
 328          * subqueries.
 329          */
 330         expand_inherited_tables(root);
 331
 332         /*
 333          * Set hasHavingQual to remember if HAVING clause is present.  Needed
 334          * because preprocess_expression will reduce a constant-true condition to
 335          * an empty qual list ... but "HAVING TRUE" is not a semantic no-op.
 336          */
 337         root->hasHavingQual = (parse->havingQual != NULL);
 338
 339         /* Clear this flag; might get set in distribute_qual_to_rels */
 340         root->hasPseudoConstantQuals = false;
 341
 342         /*
 343          * Do expression preprocessing on targetlist and quals.
 344          */
 345         parse->targetList = (List *)
 346                 preprocess_expression(root, (Node *) parse->targetList,
 347                                                           EXPRKIND_TARGET);
 348
 349         parse->returningList = (List *)
 350                 preprocess_expression(root, (Node *) parse->returningList,
 351                                                           EXPRKIND_TARGET);
 352
 353         preprocess_qual_conditions(root, (Node *) parse->jointree);
 354
 355         parse->havingQual = preprocess_expression(root, parse->havingQual,
 356                                                                                           EXPRKIND_QUAL);
 357
 358         parse->limitOffset = preprocess_expression(root, parse->limitOffset,
 359                                                                                            EXPRKIND_LIMIT);
 360         parse->limitCount = preprocess_expression(root, parse->limitCount,
 361                                                                                           EXPRKIND_LIMIT);
 362
 363         root->in_info_list = (List *)
 364                 preprocess_expression(root, (Node *) root->in_info_list,
 365                                                           EXPRKIND_ININFO);
 366         root->append_rel_list = (List *)
 367                 preprocess_expression(root, (Node *) root->append_rel_list,
 368                                                           EXPRKIND_APPINFO);
 369
 370         /* Also need to preprocess expressions for function and values RTEs */
 371         foreach(l, parse->rtable)
 372         {
 373                 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 374
 375                 if (rte->rtekind == RTE_FUNCTION)
 376                         rte->funcexpr = preprocess_expression(root, rte->funcexpr,
 377                                                                                                   EXPRKIND_RTFUNC);
 378                 else if (rte->rtekind == RTE_VALUES)
 379                         rte->values_lists = (List *)
 380                                 preprocess_expression(root, (Node *) rte->values_lists,
 381                                                                           EXPRKIND_VALUES);
 382         }
 383
 384         /*
 385          * In some cases we may want to transfer a HAVING clause into WHERE. We
 386          * cannot do so if the HAVING clause contains aggregates (obviously) or
 387          * volatile functions (since a HAVING clause is supposed to be executed
 388          * only once per group).  Also, it may be that the clause is so expensive
 389          * to execute that we're better off doing it only once per group, despite
 390          * the loss of selectivity.  This is hard to estimate short of doing the
 391          * entire planning process twice, so we use a heuristic: clauses
 392          * containing subplans are left in HAVING.      Otherwise, we move or copy the
 393          * HAVING clause into WHERE, in hopes of eliminating tuples before
 394          * aggregation instead of after.
 395          *
 396          * If the query has explicit grouping then we can simply move such a
 397          * clause into WHERE; any group that fails the clause will not be in the
 398          * output because none of its tuples will reach the grouping or
 399          * aggregation stage.  Otherwise we must have a degenerate (variable-free)
 400          * HAVING clause, which we put in WHERE so that query_planner() can use it
 401          * in a gating Result node, but also keep in HAVING to ensure that we
 402          * don't emit a bogus aggregated row. (This could be done better, but it
 403          * seems not worth optimizing.)
 404          *
 405          * Note that both havingQual and parse->jointree->quals are in
 406          * implicitly-ANDed-list form at this point, even though they are declared
 407          * as Node *.
 408          */
 409         newHaving = NIL;
 410         foreach(l, (List *) parse->havingQual)
 411         {
 412                 Node       *havingclause = (Node *) lfirst(l);
 413
 414                 if (contain_agg_clause(havingclause) ||
 415                         contain_volatile_functions(havingclause) ||
 416                         contain_subplans(havingclause))
 417                 {
 418                         /* keep it in HAVING */
 419                         newHaving = lappend(newHaving, havingclause);
 420                 }
 421                 else if (parse->groupClause)
 422                 {
 423                         /* move it to WHERE */
 424                         parse->jointree->quals = (Node *)
 425                                 lappend((List *) parse->jointree->quals, havingclause);
 426                 }
 427                 else
 428                 {
 429                         /* put a copy in WHERE, keep it in HAVING */
 430                         parse->jointree->quals = (Node *)
 431                                 lappend((List *) parse->jointree->quals,
 432                                                 copyObject(havingclause));
 433                         newHaving = lappend(newHaving, havingclause);
 434                 }
 435         }
 436         parse->havingQual = (Node *) newHaving;
 437
 438         /*
 439          * If we have any outer joins, try to reduce them to plain inner joins.
 440          * This step is most easily done after we've done expression
 441          * preprocessing.
 442          */
 443         if (root->hasOuterJoins)
 444                 reduce_outer_joins(root);
 445
 446         /*
 447          * Do the main planning.  If we have an inherited target relation, that
 448          * needs special processing, else go straight to grouping_planner.
 449          */
 450         if (parse->resultRelation &&
 451                 rt_fetch(parse->resultRelation, parse->rtable)->inh)
 452                 plan = inheritance_planner(root);
 453         else
 454                 plan = grouping_planner(root, tuple_fraction);
 455
 456         /*
 457          * If any subplans were generated, or if we're inside a subplan, build
 458          * initPlan list and extParam/allParam sets for plan nodes, and attach the
 459          * initPlans to the top plan node.
 460          */
 461         if (list_length(glob->subplans) != num_old_subplans ||
 462                 root->query_level > 1)
 463                 SS_finalize_plan(root, plan, true);
 464
 465         /* Return internal info if caller wants it */
 466         if (subroot)
 467                 *subroot = root;
 468
 469         return plan;
 470 }
 471
 472 /*
 473  * preprocess_expression
 474  *              Do subquery_planner's preprocessing work for an expression,
 475  *              which can be a targetlist, a WHERE clause (including JOIN/ON
 476  *              conditions), or a HAVING clause.
 477  */
 478 static Node *
 479 preprocess_expression(PlannerInfo *root, Node *expr, int kind)
 480 {
 481         /*
 482          * Fall out quickly if expression is empty.  This occurs often enough to
 483          * be worth checking.  Note that null->null is the correct conversion for
 484          * implicit-AND result format, too.
 485          */
 486         if (expr == NULL)
 487                 return NULL;
 488
 489         /*
 490          * If the query has any join RTEs, replace join alias variables with
 491          * base-relation variables. We must do this before sublink processing,
 492          * else sublinks expanded out from join aliases wouldn't get processed. We
 493          * can skip it in VALUES lists, however, since they can't contain any Vars
 494          * at all.
 495          */
 496         if (root->hasJoinRTEs && kind != EXPRKIND_VALUES)
 497                 expr = flatten_join_alias_vars(root, expr);
 498
 499         /*
 500          * Simplify constant expressions.
 501          *
 502          * Note: this also flattens nested AND and OR expressions into N-argument
 503          * form.  All processing of a qual expression after this point must be
 504          * careful to maintain AND/OR flatness --- that is, do not generate a tree
 505          * with AND directly under AND, nor OR directly under OR.
 506          *
 507          * Because this is a relatively expensive process, we skip it when the
 508          * query is trivial, such as "SELECT 2+2;" or "INSERT ... VALUES()". The
 509          * expression will only be evaluated once anyway, so no point in
 510          * pre-simplifying; we can't execute it any faster than the executor can,
 511          * and we will waste cycles copying the tree.  Notice however that we
 512          * still must do it for quals (to get AND/OR flatness); and if we are in a
 513          * subquery we should not assume it will be done only once.
 514          *
 515          * For VALUES lists we never do this at all, again on the grounds that we
 516          * should optimize for one-time evaluation.
 517          */
 518         if (kind != EXPRKIND_VALUES &&
 519                 (root->parse->jointree->fromlist != NIL ||
 520                  kind == EXPRKIND_QUAL ||
 521                  root->query_level > 1))
 522                 expr = eval_const_expressions(root, expr);
 523
 524         /*
 525          * If it's a qual or havingQual, canonicalize it.
 526          */
 527         if (kind == EXPRKIND_QUAL)
 528         {
 529                 expr = (Node *) canonicalize_qual((Expr *) expr);
 530
 531 #ifdef OPTIMIZER_DEBUG
 532                 printf("After canonicalize_qual()\n");
 533                 pprint(expr);
 534 #endif
 535         }
 536
 537         /* Expand SubLinks to SubPlans */
 538         if (root->parse->hasSubLinks)
 539                 expr = SS_process_sublinks(root, expr, (kind == EXPRKIND_QUAL));
 540
 541         /*
 542          * XXX do not insert anything here unless you have grokked the comments in
 543          * SS_replace_correlation_vars ...
 544          */
 545
 546         /* Replace uplevel vars with Param nodes (this IS possible in VALUES) */
 547         if (root->query_level > 1)
 548                 expr = SS_replace_correlation_vars(root, expr);
 549
 550         /*
 551          * If it's a qual or havingQual, convert it to implicit-AND format. (We
 552          * don't want to do this before eval_const_expressions, since the latter
 553          * would be unable to simplify a top-level AND correctly. Also,
 554          * SS_process_sublinks expects explicit-AND format.)
 555          */
 556         if (kind == EXPRKIND_QUAL)
 557                 expr = (Node *) make_ands_implicit((Expr *) expr);
 558
 559         return expr;
 560 }
 561
 562 /*
 563  * preprocess_qual_conditions
 564  *              Recursively scan the query's jointree and do subquery_planner's
 565  *              preprocessing work on each qual condition found therein.
 566  */
 567 static void
 568 preprocess_qual_conditions(PlannerInfo *root, Node *jtnode)
 569 {
 570         if (jtnode == NULL)
 571                 return;
 572         if (IsA(jtnode, RangeTblRef))
 573         {
 574                 /* nothing to do here */
 575         }
 576         else if (IsA(jtnode, FromExpr))
 577         {
 578                 FromExpr   *f = (FromExpr *) jtnode;
 579                 ListCell   *l;
 580
 581                 foreach(l, f->fromlist)
 582                         preprocess_qual_conditions(root, lfirst(l));
 583
 584                 f->quals = preprocess_expression(root, f->quals, EXPRKIND_QUAL);
 585         }
 586         else if (IsA(jtnode, JoinExpr))
 587         {
 588                 JoinExpr   *j = (JoinExpr *) jtnode;
 589
 590                 preprocess_qual_conditions(root, j->larg);
 591                 preprocess_qual_conditions(root, j->rarg);
 592
 593                 j->quals = preprocess_expression(root, j->quals, EXPRKIND_QUAL);
 594         }
 595         else
 596                 elog(ERROR, "unrecognized node type: %d",
 597                          (int) nodeTag(jtnode));
 598 }
 599
 600 /*
 601  * inheritance_planner
 602  *        Generate a plan in the case where the result relation is an
 603  *        inheritance set.
 604  *
 605  * We have to handle this case differently from cases where a source relation
 606  * is an inheritance set. Source inheritance is expanded at the bottom of the
 607  * plan tree (see allpaths.c), but target inheritance has to be expanded at
 608  * the top.  The reason is that for UPDATE, each target relation needs a
 609  * different targetlist matching its own column set.  Also, for both UPDATE
 610  * and DELETE, the executor needs the Append plan node at the top, else it
 611  * can't keep track of which table is the current target table.  Fortunately,
 612  * the UPDATE/DELETE target can never be the nullable side of an outer join,
 613  * so it's OK to generate the plan this way.
 614  *
 615  * Returns a query plan.
 616  */
 617 static Plan *
 618 inheritance_planner(PlannerInfo *root)
 619 {
 620         Query      *parse = root->parse;
 621         int                     parentRTindex = parse->resultRelation;
 622         List       *subplans = NIL;
 623         List       *resultRelations = NIL;
 624         List       *returningLists = NIL;
 625         List       *rtable = NIL;
 626         List       *tlist = NIL;
 627         PlannerInfo subroot;
 628         ListCell   *l;
 629
 630         foreach(l, root->append_rel_list)
 631         {
 632                 AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
 633                 Plan       *subplan;
 634
 635                 /* append_rel_list contains all append rels; ignore others */
 636                 if (appinfo->parent_relid != parentRTindex)
 637                         continue;
 638
 639                 /*
 640                  * Generate modified query with this rel as target.  We have to be
 641                  * prepared to translate varnos in in_info_list as well as in the
 642                  * Query proper.
 643                  */
 644                 memcpy(&subroot, root, sizeof(PlannerInfo));
 645                 subroot.parse = (Query *)
 646                         adjust_appendrel_attrs((Node *) parse,
 647                                                                    appinfo);
 648                 subroot.in_info_list = (List *)
 649                         adjust_appendrel_attrs((Node *) root->in_info_list,
 650                                                                    appinfo);
 651                 subroot.init_plans = NIL;
 652                 /* There shouldn't be any OJ info to translate, as yet */
 653                 Assert(subroot.oj_info_list == NIL);
 654
 655                 /* Generate plan */
 656                 subplan = grouping_planner(&subroot, 0.0 /* retrieve all tuples */ );
 657
 658                 /*
 659                  * If this child rel was excluded by constraint exclusion, exclude it
 660                  * from the plan.
 661                  */
 662                 if (is_dummy_plan(subplan))
 663                         continue;
 664
 665                 /* Save rtable and tlist from first rel for use below */
 666                 if (subplans == NIL)
 667                 {
 668                         rtable = subroot.parse->rtable;
 669                         tlist = subplan->targetlist;
 670                 }
 671
 672                 subplans = lappend(subplans, subplan);
 673
 674                 /* Make sure any initplans from this rel get into the outer list */
 675                 root->init_plans = list_concat(root->init_plans, subroot.init_plans);
 676
 677                 /* Build target-relations list for the executor */
 678                 resultRelations = lappend_int(resultRelations, appinfo->child_relid);
 679
 680                 /* Build list of per-relation RETURNING targetlists */
 681                 if (parse->returningList)
 682                 {
 683                         Assert(list_length(subroot.returningLists) == 1);
 684                         returningLists = list_concat(returningLists,
 685                                                                                  subroot.returningLists);
 686                 }
 687         }
 688
 689         root->resultRelations = resultRelations;
 690         root->returningLists = returningLists;
 691
 692         /* Mark result as unordered (probably unnecessary) */
 693         root->query_pathkeys = NIL;
 694
 695         /*
 696          * If we managed to exclude every child rel, return a dummy plan
 697          */
 698         if (subplans == NIL)
 699         {
 700                 root->resultRelations = list_make1_int(parentRTindex);
 701                 /* although dummy, it must have a valid tlist for executor */
 702                 tlist = preprocess_targetlist(root, parse->targetList);
 703                 return (Plan *) make_result(root,
 704                                                                         tlist,
 705                                                                         (Node *) list_make1(makeBoolConst(false,
 706                                                                                                                                           false)),
 707                                                                         NULL);
 708         }
 709
 710         /*
 711          * Planning might have modified the rangetable, due to changes of the
 712          * Query structures inside subquery RTEs.  We have to ensure that this
 713          * gets propagated back to the master copy.  But can't do this until we
 714          * are done planning, because all the calls to grouping_planner need
 715          * virgin sub-Queries to work from.  (We are effectively assuming that
 716          * sub-Queries will get planned identically each time, or at least that
 717          * the impacts on their rangetables will be the same each time.)
 718          *
 719          * XXX should clean this up someday
 720          */
 721         parse->rtable = rtable;
 722
 723         /* Suppress Append if there's only one surviving child rel */
 724         if (list_length(subplans) == 1)
 725                 return (Plan *) linitial(subplans);
 726
 727         return (Plan *) make_append(subplans, true, tlist);
 728 }
 729
 730 /*--------------------
 731  * grouping_planner
 732  *        Perform planning steps related to grouping, aggregation, etc.
 733  *        This primarily means adding top-level processing to the basic
 734  *        query plan produced by query_planner.
 735  *
 736  * tuple_fraction is the fraction of tuples we expect will be retrieved
 737  *
 738  * tuple_fraction is interpreted as follows:
 739  *        0: expect all tuples to be retrieved (normal case)
 740  *        0 < tuple_fraction < 1: expect the given fraction of tuples available
 741  *              from the plan to be retrieved
 742  *        tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
 743  *              expected to be retrieved (ie, a LIMIT specification)
 744  *
 745  * Returns a query plan.  Also, root->query_pathkeys is returned as the
 746  * actual output ordering of the plan (in pathkey format).
 747  *--------------------
 748  */
 749 static Plan *
 750 grouping_planner(PlannerInfo *root, double tuple_fraction)
 751 {
 752         Query      *parse = root->parse;
 753         List       *tlist = parse->targetList;
 754         int64           offset_est = 0;
 755         int64           count_est = 0;
 756         double          limit_tuples = -1.0;
 757         Plan       *result_plan;
 758         List       *current_pathkeys;
 759         List       *sort_pathkeys;
 760         double          dNumGroups = 0;
 761
 762         /* Tweak caller-supplied tuple_fraction if have LIMIT/OFFSET */
 763         if (parse->limitCount || parse->limitOffset)
 764         {
 765                 tuple_fraction = preprocess_limit(root, tuple_fraction,
 766                                                                                   &offset_est, &count_est);
 767
 768                 /*
 769                  * If we have a known LIMIT, and don't have an unknown OFFSET, we can
 770                  * estimate the effects of using a bounded sort.
 771                  */
 772                 if (count_est > 0 && offset_est >= 0)
 773                         limit_tuples = (double) count_est + (double) offset_est;
 774         }
 775
 776         if (parse->setOperations)
 777         {
 778                 List       *set_sortclauses;
 779
 780                 /*
 781                  * If there's a top-level ORDER BY, assume we have to fetch all the
 782                  * tuples.      This might seem too simplistic given all the hackery below
 783                  * to possibly avoid the sort ... but a nonzero tuple_fraction is only
 784                  * of use to plan_set_operations() when the setop is UNION ALL, and
 785                  * the result of UNION ALL is always unsorted.
 786                  */
 787                 if (parse->sortClause)
 788                         tuple_fraction = 0.0;
 789
 790                 /*
 791                  * Construct the plan for set operations.  The result will not need
 792                  * any work except perhaps a top-level sort and/or LIMIT.
 793                  */
 794                 result_plan = plan_set_operations(root, tuple_fraction,
 795                                                                                   &set_sortclauses);
 796
 797                 /*
 798                  * Calculate pathkeys representing the sort order (if any) of the set
 799                  * operation's result.  We have to do this before overwriting the sort
 800                  * key information...
 801                  */
 802                 current_pathkeys = make_pathkeys_for_sortclauses(root,
 803                                                                                                                  set_sortclauses,
 804                                                                                                          result_plan->targetlist,
 805                                                                                                                  true);
 806
 807                 /*
 808                  * We should not need to call preprocess_targetlist, since we must be
 809                  * in a SELECT query node.      Instead, use the targetlist returned by
 810                  * plan_set_operations (since this tells whether it returned any
 811                  * resjunk columns!), and transfer any sort key information from the
 812                  * original tlist.
 813                  */
 814                 Assert(parse->commandType == CMD_SELECT);
 815
 816                 tlist = postprocess_setop_tlist(result_plan->targetlist, tlist);
 817
 818                 /*
 819                  * Can't handle FOR UPDATE/SHARE here (parser should have checked
 820                  * already, but let's make sure).
 821                  */
 822                 if (parse->rowMarks)
 823                         ereport(ERROR,
 824                                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 825                                          errmsg("SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT")));
 826
 827                 /*
 828                  * Calculate pathkeys that represent result ordering requirements
 829                  */
 830                 Assert(parse->distinctClause == NIL);
 831                 sort_pathkeys = make_pathkeys_for_sortclauses(root,
 832                                                                                                           parse->sortClause,
 833                                                                                                           tlist,
 834                                                                                                           true);
 835         }
 836         else
 837         {
 838                 /* No set operations, do regular planning */
 839                 List       *sub_tlist;
 840                 List       *group_pathkeys;
 841                 AttrNumber *groupColIdx = NULL;
 842                 Oid                *groupOperators = NULL;
 843                 bool            need_tlist_eval = true;
 844                 QualCost        tlist_cost;
 845                 Path       *cheapest_path;
 846                 Path       *sorted_path;
 847                 Path       *best_path;
 848                 long            numGroups = 0;
 849                 AggClauseCounts agg_counts;
 850                 int                     numGroupCols;
 851                 bool            use_hashed_grouping = false;
 852
 853                 MemSet(&agg_counts, 0, sizeof(AggClauseCounts));
 854
 855                 /* Preprocess GROUP BY clause, if any */
 856                 if (parse->groupClause)
 857                         preprocess_groupclause(root);
 858                 numGroupCols = list_length(parse->groupClause);
 859
 860                 /* Preprocess targetlist */
 861                 tlist = preprocess_targetlist(root, tlist);
 862
 863                 /*
 864                  * Generate appropriate target list for subplan; may be different from
 865                  * tlist if grouping or aggregation is needed.
 866                  */
 867                 sub_tlist = make_subplanTargetList(root, tlist,
 868                                                                                    &groupColIdx, &need_tlist_eval);
 869
 870                 /*
 871                  * Calculate pathkeys that represent grouping/ordering requirements.
 872                  * Stash them in PlannerInfo so that query_planner can canonicalize
 873                  * them after EquivalenceClasses have been formed.
 874                  *
 875                  * Note: for the moment, DISTINCT is always implemented via sort/uniq,
 876                  * and we set the sort_pathkeys to be the more rigorous of the
 877                  * DISTINCT and ORDER BY requirements.  This should be changed
 878                  * someday, but DISTINCT ON is a bit of a problem ...
 879                  */
 880                 root->group_pathkeys =
 881                         make_pathkeys_for_sortclauses(root,
 882                                                                                   parse->groupClause,
 883                                                                                   tlist,
 884                                                                                   false);
 885                 if (list_length(parse->distinctClause) > list_length(parse->sortClause))
 886                         root->sort_pathkeys =
 887                                 make_pathkeys_for_sortclauses(root,
 888                                                                                           parse->distinctClause,
 889                                                                                           tlist,
 890                                                                                           false);
 891                 else
 892                         root->sort_pathkeys =
 893                                 make_pathkeys_for_sortclauses(root,
 894                                                                                           parse->sortClause,
 895                                                                                           tlist,
 896                                                                                           false);
 897
 898                 /*
 899                  * Will need actual number of aggregates for estimating costs.
 900                  *
 901                  * Note: we do not attempt to detect duplicate aggregates here; a
 902                  * somewhat-overestimated count is okay for our present purposes.
 903                  *
 904                  * Note: think not that we can turn off hasAggs if we find no aggs. It
 905                  * is possible for constant-expression simplification to remove all
 906                  * explicit references to aggs, but we still have to follow the
 907                  * aggregate semantics (eg, producing only one output row).
 908                  */
 909                 if (parse->hasAggs)
 910                 {
 911                         count_agg_clauses((Node *) tlist, &agg_counts);
 912                         count_agg_clauses(parse->havingQual, &agg_counts);
 913                 }
 914
 915                 /*
 916                  * Figure out whether we need a sorted result from query_planner.
 917                  *
 918                  * If we have a GROUP BY clause, then we want a result sorted properly
 919                  * for grouping.  Otherwise, if there is an ORDER BY clause, we want
 920                  * to sort by the ORDER BY clause.      (Note: if we have both, and ORDER
 921                  * BY is a superset of GROUP BY, it would be tempting to request sort
 922                  * by ORDER BY --- but that might just leave us failing to exploit an
 923                  * available sort order at all. Needs more thought...)
 924                  */
 925                 if (root->group_pathkeys)
 926                         root->query_pathkeys = root->group_pathkeys;
 927                 else if (root->sort_pathkeys)
 928                         root->query_pathkeys = root->sort_pathkeys;
 929                 else
 930                         root->query_pathkeys = NIL;
 931
 932                 /*
 933                  * Generate the best unsorted and presorted paths for this Query (but
 934                  * note there may not be any presorted path).  query_planner will also
 935                  * estimate the number of groups in the query, and canonicalize all
 936                  * the pathkeys.
 937                  */
 938                 query_planner(root, sub_tlist, tuple_fraction, limit_tuples,
 939                                           &cheapest_path, &sorted_path, &dNumGroups);
 940
 941                 group_pathkeys = root->group_pathkeys;
 942                 sort_pathkeys = root->sort_pathkeys;
 943
 944                 /*
 945                  * If grouping, extract the grouping operators and decide whether we
 946                  * want to use hashed grouping.
 947                  */
 948                 if (parse->groupClause)
 949                 {
 950                         groupOperators = extract_grouping_ops(parse->groupClause);
 951                         use_hashed_grouping =
 952                                 choose_hashed_grouping(root, tuple_fraction, limit_tuples,
 953                                                                            cheapest_path, sorted_path,
 954                                                                            groupOperators, dNumGroups,
 955                                                                            &agg_counts);
 956
 957                         /* Also convert # groups to long int --- but 'ware overflow! */
 958                         numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
 959                 }
 960
 961                 /*
 962                  * Select the best path.  If we are doing hashed grouping, we will
 963                  * always read all the input tuples, so use the cheapest-total path.
 964                  * Otherwise, trust query_planner's decision about which to use.
 965                  */
 966                 if (use_hashed_grouping || !sorted_path)
 967                         best_path = cheapest_path;
 968                 else
 969                         best_path = sorted_path;
 970
 971                 /*
 972                  * Check to see if it's possible to optimize MIN/MAX aggregates. If
 973                  * so, we will forget all the work we did so far to choose a "regular"
 974                  * path ... but we had to do it anyway to be able to tell which way is
 975                  * cheaper.
 976                  */
 977                 result_plan = optimize_minmax_aggregates(root,
 978                                                                                                  tlist,
 979                                                                                                  best_path);
 980                 if (result_plan != NULL)
 981                 {
 982                         /*
 983                          * optimize_minmax_aggregates generated the full plan, with the
 984                          * right tlist, and it has no sort order.
 985                          */
 986                         current_pathkeys = NIL;
 987                 }
 988                 else
 989                 {
 990                         /*
 991                          * Normal case --- create a plan according to query_planner's
 992                          * results.
 993                          */
 994                         bool    need_sort_for_grouping = false;
 995
 996                         result_plan = create_plan(root, best_path);
 997                         current_pathkeys = best_path->pathkeys;
 998
 999                         /* Detect if we'll need an explicit sort for grouping */
1000                         if (parse->groupClause && !use_hashed_grouping &&
1001                                 !pathkeys_contained_in(group_pathkeys, current_pathkeys))
1002                         {
1003                                 need_sort_for_grouping = true;
1004                                 /*
1005                                  * Always override query_planner's tlist, so that we don't
1006                                  * sort useless data from a "physical" tlist.
1007                                  */
1008                                 need_tlist_eval = true;
1009                         }
1010
1011                         /*
1012                          * create_plan() returns a plan with just a "flat" tlist of
1013                          * required Vars.  Usually we need to insert the sub_tlist as the
1014                          * tlist of the top plan node.  However, we can skip that if we
1015                          * determined that whatever query_planner chose to return will be
1016                          * good enough.
1017                          */
1018                         if (need_tlist_eval)
1019                         {
1020                                 /*
1021                                  * If the top-level plan node is one that cannot do expression
1022                                  * evaluation, we must insert a Result node to project the
1023                                  * desired tlist.
1024                                  */
1025                                 if (!is_projection_capable_plan(result_plan))
1026                                 {
1027                                         result_plan = (Plan *) make_result(root,
1028                                                                                                            sub_tlist,
1029                                                                                                            NULL,
1030                                                                                                            result_plan);
1031                                 }
1032                                 else
1033                                 {
1034                                         /*
1035                                          * Otherwise, just replace the subplan's flat tlist with
1036                                          * the desired tlist.
1037                                          */
1038                                         result_plan->targetlist = sub_tlist;
1039                                 }
1040
1041                                 /*
1042                                  * Also, account for the cost of evaluation of the sub_tlist.
1043                                  *
1044                                  * Up to now, we have only been dealing with "flat" tlists,
1045                                  * containing just Vars.  So their evaluation cost is zero
1046                                  * according to the model used by cost_qual_eval() (or if you
1047                                  * prefer, the cost is factored into cpu_tuple_cost).  Thus we
1048                                  * can avoid accounting for tlist cost throughout
1049                                  * query_planner() and subroutines.  But now we've inserted a
1050                                  * tlist that might contain actual operators, sub-selects, etc
1051                                  * --- so we'd better account for its cost.
1052                                  *
1053                                  * Below this point, any tlist eval cost for added-on nodes
1054                                  * should be accounted for as we create those nodes.
1055                                  * Presently, of the node types we can add on, only Agg and
1056                                  * Group project new tlists (the rest just copy their input
1057                                  * tuples) --- so make_agg() and make_group() are responsible
1058                                  * for computing the added cost.
1059                                  */
1060                                 cost_qual_eval(&tlist_cost, sub_tlist, root);
1061                                 result_plan->startup_cost += tlist_cost.startup;
1062                                 result_plan->total_cost += tlist_cost.startup +
1063                                         tlist_cost.per_tuple * result_plan->plan_rows;
1064                         }
1065                         else
1066                         {
1067                                 /*
1068                                  * Since we're using query_planner's tlist and not the one
1069                                  * make_subplanTargetList calculated, we have to refigure any
1070                                  * grouping-column indexes make_subplanTargetList computed.
1071                                  */
1072                                 locate_grouping_columns(root, tlist, result_plan->targetlist,
1073                                                                                 groupColIdx);
1074                         }
1075
1076                         /*
1077                          * Insert AGG or GROUP node if needed, plus an explicit sort step
1078                          * if necessary.
1079                          *
1080                          * HAVING clause, if any, becomes qual of the Agg or Group node.
1081                          */
1082                         if (use_hashed_grouping)
1083                         {
1084                                 /* Hashed aggregate plan --- no sort needed */
1085                                 result_plan = (Plan *) make_agg(root,
1086                                                                                                 tlist,
1087                                                                                                 (List *) parse->havingQual,
1088                                                                                                 AGG_HASHED,
1089                                                                                                 numGroupCols,
1090                                                                                                 groupColIdx,
1091                                                                                                 groupOperators,
1092                                                                                                 numGroups,
1093                                                                                                 agg_counts.numAggs,
1094                                                                                                 result_plan);
1095                                 /* Hashed aggregation produces randomly-ordered results */
1096                                 current_pathkeys = NIL;
1097                         }
1098                         else if (parse->hasAggs)
1099                         {
1100                                 /* Plain aggregate plan --- sort if needed */
1101                                 AggStrategy aggstrategy;
1102
1103                                 if (parse->groupClause)
1104                                 {
1105                                         if (need_sort_for_grouping)
1106                                         {
1107                                                 result_plan = (Plan *)
1108                                                         make_sort_from_groupcols(root,
1109                                                                                                          parse->groupClause,
1110                                                                                                          groupColIdx,
1111                                                                                                          result_plan);
1112                                                 current_pathkeys = group_pathkeys;
1113                                         }
1114                                         aggstrategy = AGG_SORTED;
1115
1116                                         /*
1117                                          * The AGG node will not change the sort ordering of its
1118                                          * groups, so current_pathkeys describes the result too.
1119                                          */
1120                                 }
1121                                 else
1122                                 {
1123                                         aggstrategy = AGG_PLAIN;
1124                                         /* Result will be only one row anyway; no sort order */
1125                                         current_pathkeys = NIL;
1126                                 }
1127
1128                                 result_plan = (Plan *) make_agg(root,
1129                                                                                                 tlist,
1130                                                                                                 (List *) parse->havingQual,
1131                                                                                                 aggstrategy,
1132                                                                                                 numGroupCols,
1133                                                                                                 groupColIdx,
1134                                                                                                 groupOperators,
1135                                                                                                 numGroups,
1136                                                                                                 agg_counts.numAggs,
1137                                                                                                 result_plan);
1138                         }
1139                         else if (parse->groupClause)
1140                         {
1141                                 /*
1142                                  * GROUP BY without aggregation, so insert a group node (plus
1143                                  * the appropriate sort node, if necessary).
1144                                  *
1145                                  * Add an explicit sort if we couldn't make the path come out
1146                                  * the way the GROUP node needs it.
1147                                  */
1148                                 if (need_sort_for_grouping)
1149                                 {
1150                                         result_plan = (Plan *)
1151                                                 make_sort_from_groupcols(root,
1152                                                                                                  parse->groupClause,
1153                                                                                                  groupColIdx,
1154                                                                                                  result_plan);
1155                                         current_pathkeys = group_pathkeys;
1156                                 }
1157
1158                                 result_plan = (Plan *) make_group(root,
1159                                                                                                   tlist,
1160                                                                                                   (List *) parse->havingQual,
1161                                                                                                   numGroupCols,
1162                                                                                                   groupColIdx,
1163                                                                                                   groupOperators,
1164                                                                                                   dNumGroups,
1165                                                                                                   result_plan);
1166                                 /* The Group node won't change sort ordering */
1167                         }
1168                         else if (root->hasHavingQual)
1169                         {
1170                                 /*
1171                                  * No aggregates, and no GROUP BY, but we have a HAVING qual.
1172                                  * This is a degenerate case in which we are supposed to emit
1173                                  * either 0 or 1 row depending on whether HAVING succeeds.
1174                                  * Furthermore, there cannot be any variables in either HAVING
1175                                  * or the targetlist, so we actually do not need the FROM
1176                                  * table at all!  We can just throw away the plan-so-far and
1177                                  * generate a Result node.      This is a sufficiently unusual
1178                                  * corner case that it's not worth contorting the structure of
1179                                  * this routine to avoid having to generate the plan in the
1180                                  * first place.
1181                                  */
1182                                 result_plan = (Plan *) make_result(root,
1183                                                                                                    tlist,
1184                                                                                                    parse->havingQual,
1185                                                                                                    NULL);
1186                         }
1187                 }                                               /* end of non-minmax-aggregate case */
1188         }                                                       /* end of if (setOperations) */
1189
1190         /*
1191          * If we were not able to make the plan come out in the right order, add
1192          * an explicit sort step.
1193          */
1194         if (sort_pathkeys)
1195         {
1196                 if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
1197                 {
1198                         result_plan = (Plan *) make_sort_from_pathkeys(root,
1199                                                                                                                    result_plan,
1200                                                                                                                    sort_pathkeys,
1201                                                                                                                    limit_tuples);
1202                         current_pathkeys = sort_pathkeys;
1203                 }
1204         }
1205
1206         /*
1207          * If there is a DISTINCT clause, add the UNIQUE node.
1208          */
1209         if (parse->distinctClause)
1210         {
1211                 result_plan = (Plan *) make_unique(result_plan, parse->distinctClause);
1212
1213                 /*
1214                  * If there was grouping or aggregation, leave plan_rows as-is (ie,
1215                  * assume the result was already mostly unique).  If not, use the
1216                  * number of distinct-groups calculated by query_planner.
1217                  */
1218                 if (!parse->groupClause && !root->hasHavingQual && !parse->hasAggs)
1219                         result_plan->plan_rows = dNumGroups;
1220         }
1221
1222         /*
1223          * Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
1224          */
1225         if (parse->limitCount || parse->limitOffset)
1226         {
1227                 result_plan = (Plan *) make_limit(result_plan,
1228                                                                                   parse->limitOffset,
1229                                                                                   parse->limitCount,
1230                                                                                   offset_est,
1231                                                                                   count_est);
1232         }
1233
1234         /*
1235          * Deal with the RETURNING clause if any.  It's convenient to pass the
1236          * returningList through setrefs.c now rather than at top level (if we
1237          * waited, handling inherited UPDATE/DELETE would be much harder).
1238          */
1239         if (parse->returningList)
1240         {
1241                 List       *rlist;
1242
1243                 Assert(parse->resultRelation);
1244                 rlist = set_returning_clause_references(root->glob,
1245                                                                                                 parse->returningList,
1246                                                                                                 result_plan,
1247                                                                                                 parse->resultRelation);
1248                 root->returningLists = list_make1(rlist);
1249         }
1250         else
1251                 root->returningLists = NIL;
1252
1253         /* Compute result-relations list if needed */
1254         if (parse->resultRelation)
1255                 root->resultRelations = list_make1_int(parse->resultRelation);
1256         else
1257                 root->resultRelations = NIL;
1258
1259         /*
1260          * Return the actual output ordering in query_pathkeys for possible use by
1261          * an outer query level.
1262          */
1263         root->query_pathkeys = current_pathkeys;
1264
1265         return result_plan;
1266 }
1267
1268 /*
1269  * Detect whether a plan node is a "dummy" plan created when a relation
1270  * is deemed not to need scanning due to constraint exclusion.
1271  *
1272  * Currently, such dummy plans are Result nodes with constant FALSE
1273  * filter quals.
1274  */
1275 static bool
1276 is_dummy_plan(Plan *plan)
1277 {
1278         if (IsA(plan, Result))
1279         {
1280                 List       *rcqual = (List *) ((Result *) plan)->resconstantqual;
1281
1282                 if (list_length(rcqual) == 1)
1283                 {
1284                         Const      *constqual = (Const *) linitial(rcqual);
1285
1286                         if (constqual && IsA(constqual, Const))
1287                         {
1288                                 if (!constqual->constisnull &&
1289                                         !DatumGetBool(constqual->constvalue))
1290                                         return true;
1291                         }
1292                 }
1293         }
1294         return false;
1295 }
1296
1297 /*
1298  * preprocess_limit - do pre-estimation for LIMIT and/or OFFSET clauses
1299  *
1300  * We try to estimate the values of the LIMIT/OFFSET clauses, and pass the
1301  * results back in *count_est and *offset_est.  These variables are set to
1302  * 0 if the corresponding clause is not present, and -1 if it's present
1303  * but we couldn't estimate the value for it.  (The "0" convention is OK
1304  * for OFFSET but a little bit bogus for LIMIT: effectively we estimate
1305  * LIMIT 0 as though it were LIMIT 1.  But this is in line with the planner's
1306  * usual practice of never estimating less than one row.)  These values will
1307  * be passed to make_limit, which see if you change this code.
1308  *
1309  * The return value is the suitably adjusted tuple_fraction to use for
1310  * planning the query.  This adjustment is not overridable, since it reflects
1311  * plan actions that grouping_planner() will certainly take, not assumptions
1312  * about context.
1313  */
1314 static double
1315 preprocess_limit(PlannerInfo *root, double tuple_fraction,
1316                                  int64 *offset_est, int64 *count_est)
1317 {
1318         Query      *parse = root->parse;
1319         Node       *est;
1320         double          limit_fraction;
1321
1322         /* Should not be called unless LIMIT or OFFSET */
1323         Assert(parse->limitCount || parse->limitOffset);
1324
1325         /*
1326          * Try to obtain the clause values.  We use estimate_expression_value
1327          * primarily because it can sometimes do something useful with Params.
1328          */
1329         if (parse->limitCount)
1330         {
1331                 est = estimate_expression_value(root, parse->limitCount);
1332                 if (est && IsA(est, Const))
1333                 {
1334                         if (((Const *) est)->constisnull)
1335                         {
1336                                 /* NULL indicates LIMIT ALL, ie, no limit */
1337                                 *count_est = 0; /* treat as not present */
1338                         }
1339                         else
1340                         {
1341                                 *count_est = DatumGetInt64(((Const *) est)->constvalue);
1342                                 if (*count_est <= 0)
1343                                         *count_est = 1;         /* force to at least 1 */
1344                         }
1345                 }
1346                 else
1347                         *count_est = -1;        /* can't estimate */
1348         }
1349         else
1350                 *count_est = 0;                 /* not present */
1351
1352         if (parse->limitOffset)
1353         {
1354                 est = estimate_expression_value(root, parse->limitOffset);
1355                 if (est && IsA(est, Const))
1356                 {
1357                         if (((Const *) est)->constisnull)
1358                         {
1359                                 /* Treat NULL as no offset; the executor will too */
1360                                 *offset_est = 0;        /* treat as not present */
1361                         }
1362                         else
1363                         {
1364                                 *offset_est = DatumGetInt64(((Const *) est)->constvalue);
1365                                 if (*offset_est < 0)
1366                                         *offset_est = 0;        /* less than 0 is same as 0 */
1367                         }
1368                 }
1369                 else
1370                         *offset_est = -1;       /* can't estimate */
1371         }
1372         else
1373                 *offset_est = 0;                /* not present */
1374
1375         if (*count_est != 0)
1376         {
1377                 /*
1378                  * A LIMIT clause limits the absolute number of tuples returned.
1379                  * However, if it's not a constant LIMIT then we have to guess; for
1380                  * lack of a better idea, assume 10% of the plan's result is wanted.
1381                  */
1382                 if (*count_est < 0 || *offset_est < 0)
1383                 {
1384                         /* LIMIT or OFFSET is an expression ... punt ... */
1385                         limit_fraction = 0.10;
1386                 }
1387                 else
1388                 {
1389                         /* LIMIT (plus OFFSET, if any) is max number of tuples needed */
1390                         limit_fraction = (double) *count_est + (double) *offset_est;
1391                 }
1392
1393                 /*
1394                  * If we have absolute limits from both caller and LIMIT, use the
1395                  * smaller value; likewise if they are both fractional.  If one is
1396                  * fractional and the other absolute, we can't easily determine which
1397                  * is smaller, but we use the heuristic that the absolute will usually
1398                  * be smaller.
1399                  */
1400                 if (tuple_fraction >= 1.0)
1401                 {
1402                         if (limit_fraction >= 1.0)
1403                         {
1404                                 /* both absolute */
1405                                 tuple_fraction = Min(tuple_fraction, limit_fraction);
1406                         }
1407                         else
1408                         {
1409                                 /* caller absolute, limit fractional; use caller's value */
1410                         }
1411                 }
1412                 else if (tuple_fraction > 0.0)
1413                 {
1414                         if (limit_fraction >= 1.0)
1415                         {
1416                                 /* caller fractional, limit absolute; use limit */
1417                                 tuple_fraction = limit_fraction;
1418                         }
1419                         else
1420                         {
1421                                 /* both fractional */
1422                                 tuple_fraction = Min(tuple_fraction, limit_fraction);
1423                         }
1424                 }
1425                 else
1426                 {
1427                         /* no info from caller, just use limit */
1428                         tuple_fraction = limit_fraction;
1429                 }
1430         }
1431         else if (*offset_est != 0 && tuple_fraction > 0.0)
1432         {
1433                 /*
1434                  * We have an OFFSET but no LIMIT.      This acts entirely differently
1435                  * from the LIMIT case: here, we need to increase rather than decrease
1436                  * the caller's tuple_fraction, because the OFFSET acts to cause more
1437                  * tuples to be fetched instead of fewer.  This only matters if we got
1438                  * a tuple_fraction > 0, however.
1439                  *
1440                  * As above, use 10% if OFFSET is present but unestimatable.
1441                  */
1442                 if (*offset_est < 0)
1443                         limit_fraction = 0.10;
1444                 else
1445                         limit_fraction = (double) *offset_est;
1446
1447                 /*
1448                  * If we have absolute counts from both caller and OFFSET, add them
1449                  * together; likewise if they are both fractional.      If one is
1450                  * fractional and the other absolute, we want to take the larger, and
1451                  * we heuristically assume that's the fractional one.
1452                  */
1453                 if (tuple_fraction >= 1.0)
1454                 {
1455                         if (limit_fraction >= 1.0)
1456                         {
1457                                 /* both absolute, so add them together */
1458                                 tuple_fraction += limit_fraction;
1459                         }
1460                         else
1461                         {
1462                                 /* caller absolute, limit fractional; use limit */
1463                                 tuple_fraction = limit_fraction;
1464                         }
1465                 }
1466                 else
1467                 {
1468                         if (limit_fraction >= 1.0)
1469                         {
1470                                 /* caller fractional, limit absolute; use caller's value */
1471                         }
1472                         else
1473                         {
1474                                 /* both fractional, so add them together */
1475                                 tuple_fraction += limit_fraction;
1476                                 if (tuple_fraction >= 1.0)
1477                                         tuple_fraction = 0.0;           /* assume fetch all */
1478                         }
1479                 }
1480         }
1481
1482         return tuple_fraction;
1483 }
1484
1485
1486 /*
1487  * preprocess_groupclause - do preparatory work on GROUP BY clause
1488  *
1489  * The idea here is to adjust the ordering of the GROUP BY elements
1490  * (which in itself is semantically insignificant) to match ORDER BY,
1491  * thereby allowing a single sort operation to both implement the ORDER BY
1492  * requirement and set up for a Unique step that implements GROUP BY.
1493  *
1494  * In principle it might be interesting to consider other orderings of the
1495  * GROUP BY elements, which could match the sort ordering of other
1496  * possible plans (eg an indexscan) and thereby reduce cost.  We don't
1497  * bother with that, though.  Hashed grouping will frequently win anyway.
1498  */
1499 static void
1500 preprocess_groupclause(PlannerInfo *root)
1501 {
1502         Query      *parse = root->parse;
1503         List       *new_groupclause;
1504         bool            partial_match;
1505         ListCell   *sl;
1506         ListCell   *gl;
1507
1508         /* If no ORDER BY, nothing useful to do here anyway */
1509         if (parse->sortClause == NIL)
1510                 return;
1511
1512         /*
1513          * Scan the ORDER BY clause and construct a list of matching GROUP BY
1514          * items, but only as far as we can make a matching prefix.
1515          *
1516          * This code assumes that the sortClause contains no duplicate items.
1517          */
1518         new_groupclause = NIL;
1519         foreach(sl, parse->sortClause)
1520         {
1521                 SortGroupClause *sc = (SortGroupClause *) lfirst(sl);
1522
1523                 foreach(gl, parse->groupClause)
1524                 {
1525                         SortGroupClause *gc = (SortGroupClause *) lfirst(gl);
1526
1527                         if (equal(gc, sc))
1528                         {
1529                                 new_groupclause = lappend(new_groupclause, gc);
1530                                 break;
1531                         }
1532                 }
1533                 if (gl == NULL)
1534                         break;                          /* no match, so stop scanning */
1535         }
1536
1537         /* Did we match all of the ORDER BY list, or just some of it? */
1538         partial_match = (sl != NULL);
1539
1540         /* If no match at all, no point in reordering GROUP BY */
1541         if (new_groupclause == NIL)
1542                 return;
1543
1544         /*
1545          * Add any remaining GROUP BY items to the new list, but only if we
1546          * were able to make a complete match.  In other words, we only
1547          * rearrange the GROUP BY list if the result is that one list is a
1548          * prefix of the other --- otherwise there's no possibility of a
1549          * common sort.
1550          */
1551         foreach(gl, parse->groupClause)
1552         {
1553                 SortGroupClause *gc = (SortGroupClause *) lfirst(gl);
1554
1555                 if (list_member_ptr(new_groupclause, gc))
1556                         continue;                       /* it matched an ORDER BY item */
1557                 if (partial_match)
1558                         return;                         /* give up, no common sort possible */
1559                 new_groupclause = lappend(new_groupclause, gc);
1560         }
1561
1562         /* Success --- install the rearranged GROUP BY list */
1563         Assert(list_length(parse->groupClause) == list_length(new_groupclause));
1564         parse->groupClause = new_groupclause;
1565 }
1566
1567 /*
1568  * extract_grouping_ops - make an array of the equality operator OIDs
1569  *              for the GROUP BY clause
1570  */
1571 static Oid *
1572 extract_grouping_ops(List *groupClause)
1573 {
1574         int                     numCols = list_length(groupClause);
1575         int                     colno = 0;
1576         Oid                *groupOperators;
1577         ListCell   *glitem;
1578
1579         groupOperators = (Oid *) palloc(sizeof(Oid) * numCols);
1580
1581         foreach(glitem, groupClause)
1582         {
1583                 SortGroupClause *groupcl = (SortGroupClause *) lfirst(glitem);
1584
1585                 groupOperators[colno] = groupcl->eqop;
1586                 Assert(OidIsValid(groupOperators[colno]));
1587                 colno++;
1588         }
1589
1590         return groupOperators;
1591 }
1592
1593 /*
1594  * choose_hashed_grouping - should we use hashed grouping?
1595  */
1596 static bool
1597 choose_hashed_grouping(PlannerInfo *root,
1598                                            double tuple_fraction, double limit_tuples,
1599                                            Path *cheapest_path, Path *sorted_path,
1600                                            Oid *groupOperators, double dNumGroups,
1601                                            AggClauseCounts *agg_counts)
1602 {
1603         int                     numGroupCols = list_length(root->parse->groupClause);
1604         double          cheapest_path_rows;
1605         int                     cheapest_path_width;
1606         Size            hashentrysize;
1607         List       *current_pathkeys;
1608         Path            hashed_p;
1609         Path            sorted_p;
1610         int                     i;
1611
1612         /*
1613          * Check can't-do-it conditions, including whether the grouping operators
1614          * are hashjoinable.  (We assume hashing is OK if they are marked
1615          * oprcanhash.  If there isn't actually a supporting hash function, the
1616          * executor will complain at runtime.)
1617          *
1618          * Executor doesn't support hashed aggregation with DISTINCT aggregates.
1619          * (Doing so would imply storing *all* the input values in the hash table,
1620          * which seems like a certain loser.)
1621          */
1622         if (!enable_hashagg)
1623                 return false;
1624         if (agg_counts->numDistinctAggs != 0)
1625                 return false;
1626         for (i = 0; i < numGroupCols; i++)
1627         {
1628                 if (!op_hashjoinable(groupOperators[i]))
1629                         return false;
1630         }
1631
1632         /*
1633          * Don't do it if it doesn't look like the hashtable will fit into
1634          * work_mem.
1635          *
1636          * Beware here of the possibility that cheapest_path->parent is NULL. This
1637          * could happen if user does something silly like SELECT 'foo' GROUP BY 1;
1638          */
1639         if (cheapest_path->parent)
1640         {
1641                 cheapest_path_rows = cheapest_path->parent->rows;
1642                 cheapest_path_width = cheapest_path->parent->width;
1643         }
1644         else
1645         {
1646                 cheapest_path_rows = 1; /* assume non-set result */
1647                 cheapest_path_width = 100;              /* arbitrary */
1648         }
1649
1650         /* Estimate per-hash-entry space at tuple width... */
1651         hashentrysize = MAXALIGN(cheapest_path_width) + MAXALIGN(sizeof(MinimalTupleData));
1652         /* plus space for pass-by-ref transition values... */
1653         hashentrysize += agg_counts->transitionSpace;
1654         /* plus the per-hash-entry overhead */
1655         hashentrysize += hash_agg_entry_size(agg_counts->numAggs);
1656
1657         if (hashentrysize * dNumGroups > work_mem * 1024L)
1658                 return false;
1659
1660         /*
1661          * See if the estimated cost is no more than doing it the other way. While
1662          * avoiding the need for sorted input is usually a win, the fact that the
1663          * output won't be sorted may be a loss; so we need to do an actual cost
1664          * comparison.
1665          *
1666          * We need to consider cheapest_path + hashagg [+ final sort] versus
1667          * either cheapest_path [+ sort] + group or agg [+ final sort] or
1668          * presorted_path + group or agg [+ final sort] where brackets indicate a
1669          * step that may not be needed. We assume query_planner() will have
1670          * returned a presorted path only if it's a winner compared to
1671          * cheapest_path for this purpose.
1672          *
1673          * These path variables are dummies that just hold cost fields; we don't
1674          * make actual Paths for these steps.
1675          */
1676         cost_agg(&hashed_p, root, AGG_HASHED, agg_counts->numAggs,
1677                          numGroupCols, dNumGroups,
1678                          cheapest_path->startup_cost, cheapest_path->total_cost,
1679                          cheapest_path_rows);
1680         /* Result of hashed agg is always unsorted */
1681         if (root->sort_pathkeys)
1682                 cost_sort(&hashed_p, root, root->sort_pathkeys, hashed_p.total_cost,
1683                                   dNumGroups, cheapest_path_width, limit_tuples);
1684
1685         if (sorted_path)
1686         {
1687                 sorted_p.startup_cost = sorted_path->startup_cost;
1688                 sorted_p.total_cost = sorted_path->total_cost;
1689                 current_pathkeys = sorted_path->pathkeys;
1690         }
1691         else
1692         {
1693                 sorted_p.startup_cost = cheapest_path->startup_cost;
1694                 sorted_p.total_cost = cheapest_path->total_cost;
1695                 current_pathkeys = cheapest_path->pathkeys;
1696         }
1697         if (!pathkeys_contained_in(root->group_pathkeys, current_pathkeys))
1698         {
1699                 cost_sort(&sorted_p, root, root->group_pathkeys, sorted_p.total_cost,
1700                                   cheapest_path_rows, cheapest_path_width, -1.0);
1701                 current_pathkeys = root->group_pathkeys;
1702         }
1703
1704         if (root->parse->hasAggs)
1705                 cost_agg(&sorted_p, root, AGG_SORTED, agg_counts->numAggs,
1706                                  numGroupCols, dNumGroups,
1707                                  sorted_p.startup_cost, sorted_p.total_cost,
1708                                  cheapest_path_rows);
1709         else
1710                 cost_group(&sorted_p, root, numGroupCols, dNumGroups,
1711                                    sorted_p.startup_cost, sorted_p.total_cost,
1712                                    cheapest_path_rows);
1713         /* The Agg or Group node will preserve ordering */
1714         if (root->sort_pathkeys &&
1715                 !pathkeys_contained_in(root->sort_pathkeys, current_pathkeys))
1716                 cost_sort(&sorted_p, root, root->sort_pathkeys, sorted_p.total_cost,
1717                                   dNumGroups, cheapest_path_width, limit_tuples);
1718
1719         /*
1720          * Now make the decision using the top-level tuple fraction.  First we
1721          * have to convert an absolute count (LIMIT) into fractional form.
1722          */
1723         if (tuple_fraction >= 1.0)
1724                 tuple_fraction /= dNumGroups;
1725
1726         if (compare_fractional_path_costs(&hashed_p, &sorted_p,
1727                                                                           tuple_fraction) < 0)
1728         {
1729                 /* Hashed is cheaper, so use it */
1730                 return true;
1731         }
1732         return false;
1733 }
1734
1735 /*---------------
1736  * make_subplanTargetList
1737  *        Generate appropriate target list when grouping is required.
1738  *
1739  * When grouping_planner inserts Aggregate, Group, or Result plan nodes
1740  * above the result of query_planner, we typically want to pass a different
1741  * target list to query_planner than the outer plan nodes should have.
1742  * This routine generates the correct target list for the subplan.
1743  *
1744  * The initial target list passed from the parser already contains entries
1745  * for all ORDER BY and GROUP BY expressions, but it will not have entries
1746  * for variables used only in HAVING clauses; so we need to add those
1747  * variables to the subplan target list.  Also, we flatten all expressions
1748  * except GROUP BY items into their component variables; the other expressions
1749  * will be computed by the inserted nodes rather than by the subplan.
1750  * For example, given a query like
1751  *              SELECT a+b,SUM(c+d) FROM table GROUP BY a+b;
1752  * we want to pass this targetlist to the subplan:
1753  *              a,b,c,d,a+b
1754  * where the a+b target will be used by the Sort/Group steps, and the
1755  * other targets will be used for computing the final results.  (In the
1756  * above example we could theoretically suppress the a and b targets and
1757  * pass down only c,d,a+b, but it's not really worth the trouble to
1758  * eliminate simple var references from the subplan.  We will avoid doing
1759  * the extra computation to recompute a+b at the outer level; see
1760  * fix_upper_expr() in setrefs.c.)
1761  *
1762  * If we are grouping or aggregating, *and* there are no non-Var grouping
1763  * expressions, then the returned tlist is effectively dummy; we do not
1764  * need to force it to be evaluated, because all the Vars it contains
1765  * should be present in the output of query_planner anyway.
1766  *
1767  * 'tlist' is the query's target list.
1768  * 'groupColIdx' receives an array of column numbers for the GROUP BY
1769  *                      expressions (if there are any) in the subplan's target list.
1770  * 'need_tlist_eval' is set true if we really need to evaluate the
1771  *                      result tlist.
1772  *
1773  * The result is the targetlist to be passed to the subplan.
1774  *---------------
1775  */
1776 static List *
1777 make_subplanTargetList(PlannerInfo *root,
1778                                            List *tlist,
1779                                            AttrNumber **groupColIdx,
1780                                            bool *need_tlist_eval)
1781 {
1782         Query      *parse = root->parse;
1783         List       *sub_tlist;
1784         List       *extravars;
1785         int                     numCols;
1786
1787         *groupColIdx = NULL;
1788
1789         /*
1790          * If we're not grouping or aggregating, there's nothing to do here;
1791          * query_planner should receive the unmodified target list.
1792          */
1793         if (!parse->hasAggs && !parse->groupClause && !root->hasHavingQual)
1794         {
1795                 *need_tlist_eval = true;
1796                 return tlist;
1797         }
1798
1799         /*
1800          * Otherwise, start with a "flattened" tlist (having just the vars
1801          * mentioned in the targetlist and HAVING qual --- but not upper- level
1802          * Vars; they will be replaced by Params later on).
1803          */
1804         sub_tlist = flatten_tlist(tlist);
1805         extravars = pull_var_clause(parse->havingQual, false);
1806         sub_tlist = add_to_flat_tlist(sub_tlist, extravars);
1807         list_free(extravars);
1808         *need_tlist_eval = false;       /* only eval if not flat tlist */
1809
1810         /*
1811          * If grouping, create sub_tlist entries for all GROUP BY expressions
1812          * (GROUP BY items that are simple Vars should be in the list already),
1813          * and make an array showing where the group columns are in the sub_tlist.
1814          */
1815         numCols = list_length(parse->groupClause);
1816         if (numCols > 0)
1817         {
1818                 int                     keyno = 0;
1819                 AttrNumber *grpColIdx;
1820                 ListCell   *gl;
1821
1822                 grpColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
1823                 *groupColIdx = grpColIdx;
1824
1825                 foreach(gl, parse->groupClause)
1826                 {
1827                         SortGroupClause *grpcl = (SortGroupClause *) lfirst(gl);
1828                         Node       *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1829                         TargetEntry *te = NULL;
1830                         ListCell   *sl;
1831
1832                         /* Find or make a matching sub_tlist entry */
1833                         foreach(sl, sub_tlist)
1834                         {
1835                                 te = (TargetEntry *) lfirst(sl);
1836                                 if (equal(groupexpr, te->expr))
1837                                         break;
1838                         }
1839                         if (!sl)
1840                         {
1841                                 te = makeTargetEntry((Expr *) groupexpr,
1842                                                                          list_length(sub_tlist) + 1,
1843                                                                          NULL,
1844                                                                          false);
1845                                 sub_tlist = lappend(sub_tlist, te);
1846                                 *need_tlist_eval = true;                /* it's not flat anymore */
1847                         }
1848
1849                         /* and save its resno */
1850                         grpColIdx[keyno++] = te->resno;
1851                 }
1852         }
1853
1854         return sub_tlist;
1855 }
1856
1857 /*
1858  * locate_grouping_columns
1859  *              Locate grouping columns in the tlist chosen by query_planner.
1860  *
1861  * This is only needed if we don't use the sub_tlist chosen by
1862  * make_subplanTargetList.      We have to forget the column indexes found
1863  * by that routine and re-locate the grouping vars in the real sub_tlist.
1864  */
1865 static void
1866 locate_grouping_columns(PlannerInfo *root,
1867                                                 List *tlist,
1868                                                 List *sub_tlist,
1869                                                 AttrNumber *groupColIdx)
1870 {
1871         int                     keyno = 0;
1872         ListCell   *gl;
1873
1874         /*
1875          * No work unless grouping.
1876          */
1877         if (!root->parse->groupClause)
1878         {
1879                 Assert(groupColIdx == NULL);
1880                 return;
1881         }
1882         Assert(groupColIdx != NULL);
1883
1884         foreach(gl, root->parse->groupClause)
1885         {
1886                 SortGroupClause *grpcl = (SortGroupClause *) lfirst(gl);
1887                 Node       *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1888                 TargetEntry *te = NULL;
1889                 ListCell   *sl;
1890
1891                 foreach(sl, sub_tlist)
1892                 {
1893                         te = (TargetEntry *) lfirst(sl);
1894                         if (equal(groupexpr, te->expr))
1895                                 break;
1896                 }
1897                 if (!sl)
1898                         elog(ERROR, "failed to locate grouping columns");
1899
1900                 groupColIdx[keyno++] = te->resno;
1901         }
1902 }
1903
1904 /*
1905  * postprocess_setop_tlist
1906  *        Fix up targetlist returned by plan_set_operations().
1907  *
1908  * We need to transpose sort key info from the orig_tlist into new_tlist.
1909  * NOTE: this would not be good enough if we supported resjunk sort keys
1910  * for results of set operations --- then, we'd need to project a whole
1911  * new tlist to evaluate the resjunk columns.  For now, just ereport if we
1912  * find any resjunk columns in orig_tlist.
1913  */
1914 static List *
1915 postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
1916 {
1917         ListCell   *l;
1918         ListCell   *orig_tlist_item = list_head(orig_tlist);
1919
1920         foreach(l, new_tlist)
1921         {
1922                 TargetEntry *new_tle = (TargetEntry *) lfirst(l);
1923                 TargetEntry *orig_tle;
1924
1925                 /* ignore resjunk columns in setop result */
1926                 if (new_tle->resjunk)
1927                         continue;
1928
1929                 Assert(orig_tlist_item != NULL);
1930                 orig_tle = (TargetEntry *) lfirst(orig_tlist_item);
1931                 orig_tlist_item = lnext(orig_tlist_item);
1932                 if (orig_tle->resjunk)  /* should not happen */
1933                         elog(ERROR, "resjunk output columns are not implemented");
1934                 Assert(new_tle->resno == orig_tle->resno);
1935                 new_tle->ressortgroupref = orig_tle->ressortgroupref;
1936         }
1937         if (orig_tlist_item != NULL)
1938                 elog(ERROR, "resjunk output columns are not implemented");
1939         return new_tlist;
1940 }