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) 1996-2003, 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 1.170 2004/05/26 04:41:24 neilc Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 #include "postgres.h"
  17
  18 #include <limits.h>
  19
  20 #include "catalog/pg_operator.h"
  21 #include "catalog/pg_type.h"
  22 #include "executor/executor.h"
  23 #include "miscadmin.h"
  24 #include "nodes/makefuncs.h"
  25 #ifdef OPTIMIZER_DEBUG
  26 #include "nodes/print.h"
  27 #endif
  28 #include "optimizer/clauses.h"
  29 #include "optimizer/cost.h"
  30 #include "optimizer/pathnode.h"
  31 #include "optimizer/paths.h"
  32 #include "optimizer/planmain.h"
  33 #include "optimizer/planner.h"
  34 #include "optimizer/prep.h"
  35 #include "optimizer/subselect.h"
  36 #include "optimizer/tlist.h"
  37 #include "optimizer/var.h"
  38 #include "parser/analyze.h"
  39 #include "parser/parsetree.h"
  40 #include "parser/parse_expr.h"
  41 #include "parser/parse_oper.h"
  42 #include "utils/selfuncs.h"
  43 #include "utils/syscache.h"
  44
  45
  46 /* Expression kind codes for preprocess_expression */
  47 #define EXPRKIND_QUAL   0
  48 #define EXPRKIND_TARGET 1
  49 #define EXPRKIND_RTFUNC 2
  50 #define EXPRKIND_LIMIT  3
  51 #define EXPRKIND_ININFO 4
  52
  53
  54 static Node *preprocess_expression(Query *parse, Node *expr, int kind);
  55 static void preprocess_qual_conditions(Query *parse, Node *jtnode);
  56 static Plan *inheritance_planner(Query *parse, List *inheritlist);
  57 static Plan *grouping_planner(Query *parse, double tuple_fraction);
  58 static bool hash_safe_grouping(Query *parse);
  59 static List *make_subplanTargetList(Query *parse, List *tlist,
  60                                            AttrNumber **groupColIdx, bool *need_tlist_eval);
  61 static void locate_grouping_columns(Query *parse,
  62                                                 List *tlist,
  63                                                 List *sub_tlist,
  64                                                 AttrNumber *groupColIdx);
  65 static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
  66
  67
  68 /*****************************************************************************
  69  *
  70  *         Query optimizer entry point
  71  *
  72  *****************************************************************************/
  73 Plan *
  74 planner(Query *parse, bool isCursor, int cursorOptions)
  75 {
  76         double          tuple_fraction;
  77         Plan       *result_plan;
  78         Index           save_PlannerQueryLevel;
  79         List       *save_PlannerParamList;
  80
  81         /*
  82          * The planner can be called recursively (an example is when
  83          * eval_const_expressions tries to pre-evaluate an SQL function). So,
  84          * these global state variables must be saved and restored.
  85          *
  86          * These vars cannot be moved into the Query structure since their whole
  87          * purpose is communication across multiple sub-Queries.
  88          *
  89          * Note we do NOT save and restore PlannerPlanId: it exists to assign
  90          * unique IDs to SubPlan nodes, and we want those IDs to be unique for
  91          * the life of a backend.  Also, PlannerInitPlan is saved/restored in
  92          * subquery_planner, not here.
  93          */
  94         save_PlannerQueryLevel = PlannerQueryLevel;
  95         save_PlannerParamList = PlannerParamList;
  96
  97         /* Initialize state for handling outer-level references and params */
  98         PlannerQueryLevel = 0;          /* will be 1 in top-level subquery_planner */
  99         PlannerParamList = NIL;
 100
 101         /* Determine what fraction of the plan is likely to be scanned */
 102         if (isCursor)
 103         {
 104                 /*
 105                  * We have no real idea how many tuples the user will ultimately
 106                  * FETCH from a cursor, but it seems a good bet that he doesn't
 107                  * want 'em all.  Optimize for 10% retrieval (you gotta better
 108                  * number?      Should this be a SETtable parameter?)
 109                  */
 110                 tuple_fraction = 0.10;
 111         }
 112         else
 113         {
 114                 /* Default assumption is we need all the tuples */
 115                 tuple_fraction = 0.0;
 116         }
 117
 118         /* primary planning entry point (may recurse for subqueries) */
 119         result_plan = subquery_planner(parse, tuple_fraction);
 120
 121         Assert(PlannerQueryLevel == 0);
 122
 123         /*
 124          * If creating a plan for a scrollable cursor, make sure it can run
 125          * backwards on demand.  Add a Material node at the top at need.
 126          */
 127         if (isCursor && (cursorOptions & CURSOR_OPT_SCROLL))
 128         {
 129                 if (!ExecSupportsBackwardScan(result_plan))
 130                         result_plan = materialize_finished_plan(result_plan);
 131         }
 132
 133         /* executor wants to know total number of Params used overall */
 134         result_plan->nParamExec = length(PlannerParamList);
 135
 136         /* final cleanup of the plan */
 137         set_plan_references(result_plan, parse->rtable);
 138
 139         /* restore state for outer planner, if any */
 140         PlannerQueryLevel = save_PlannerQueryLevel;
 141         PlannerParamList = save_PlannerParamList;
 142
 143         return result_plan;
 144 }
 145
 146
 147 /*--------------------
 148  * subquery_planner
 149  *        Invokes the planner on a subquery.  We recurse to here for each
 150  *        sub-SELECT found in the query tree.
 151  *
 152  * parse is the querytree produced by the parser & rewriter.
 153  * tuple_fraction is the fraction of tuples we expect will be retrieved.
 154  * tuple_fraction is interpreted as explained for grouping_planner, below.
 155  *
 156  * Basically, this routine does the stuff that should only be done once
 157  * per Query object.  It then calls grouping_planner.  At one time,
 158  * grouping_planner could be invoked recursively on the same Query object;
 159  * that's not currently true, but we keep the separation between the two
 160  * routines anyway, in case we need it again someday.
 161  *
 162  * subquery_planner will be called recursively to handle sub-Query nodes
 163  * found within the query's expressions and rangetable.
 164  *
 165  * Returns a query plan.
 166  *--------------------
 167  */
 168 Plan *
 169 subquery_planner(Query *parse, double tuple_fraction)
 170 {
 171         List       *saved_initplan = PlannerInitPlan;
 172         int                     saved_planid = PlannerPlanId;
 173         bool            hasOuterJoins;
 174         Plan       *plan;
 175         List       *newHaving;
 176         List       *lst;
 177         ListCell   *l;
 178
 179         /* Set up for a new level of subquery */
 180         PlannerQueryLevel++;
 181         PlannerInitPlan = NIL;
 182
 183         /*
 184          * Look for IN clauses at the top level of WHERE, and transform them
 185          * into joins.  Note that this step only handles IN clauses originally
 186          * at top level of WHERE; if we pull up any subqueries in the next
 187          * step, their INs are processed just before pulling them up.
 188          */
 189         parse->in_info_list = NIL;
 190         if (parse->hasSubLinks)
 191                 parse->jointree->quals = pull_up_IN_clauses(parse,
 192                                                                                                  parse->jointree->quals);
 193
 194         /*
 195          * Check to see if any subqueries in the rangetable can be merged into
 196          * this query.
 197          */
 198         parse->jointree = (FromExpr *)
 199                 pull_up_subqueries(parse, (Node *) parse->jointree, false);
 200
 201         /*
 202          * Detect whether any rangetable entries are RTE_JOIN kind; if not, we
 203          * can avoid the expense of doing flatten_join_alias_vars().  Also
 204          * check for outer joins --- if none, we can skip
 205          * reduce_outer_joins(). This must be done after we have done
 206          * pull_up_subqueries, of course.
 207          */
 208         parse->hasJoinRTEs = false;
 209         hasOuterJoins = false;
 210         foreach(l, parse->rtable)
 211         {
 212                 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 213
 214                 if (rte->rtekind == RTE_JOIN)
 215                 {
 216                         parse->hasJoinRTEs = true;
 217                         if (IS_OUTER_JOIN(rte->jointype))
 218                         {
 219                                 hasOuterJoins = true;
 220                                 /* Can quit scanning once we find an outer join */
 221                                 break;
 222                         }
 223                 }
 224         }
 225
 226         /*
 227          * Do expression preprocessing on targetlist and quals.
 228          */
 229         parse->targetList = (List *)
 230                 preprocess_expression(parse, (Node *) parse->targetList,
 231                                                           EXPRKIND_TARGET);
 232
 233         preprocess_qual_conditions(parse, (Node *) parse->jointree);
 234
 235         parse->havingQual = preprocess_expression(parse, parse->havingQual,
 236                                                                                           EXPRKIND_QUAL);
 237
 238         parse->limitOffset = preprocess_expression(parse, parse->limitOffset,
 239                                                                                            EXPRKIND_LIMIT);
 240         parse->limitCount = preprocess_expression(parse, parse->limitCount,
 241                                                                                           EXPRKIND_LIMIT);
 242
 243         parse->in_info_list = (List *)
 244                 preprocess_expression(parse, (Node *) parse->in_info_list,
 245                                                           EXPRKIND_ININFO);
 246
 247         /* Also need to preprocess expressions for function RTEs */
 248         foreach(l, parse->rtable)
 249         {
 250                 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 251
 252                 if (rte->rtekind == RTE_FUNCTION)
 253                         rte->funcexpr = preprocess_expression(parse, rte->funcexpr,
 254                                                                                                   EXPRKIND_RTFUNC);
 255         }
 256
 257         /*
 258          * A HAVING clause without aggregates is equivalent to a WHERE clause
 259          * (except it can only refer to grouped fields).  Transfer any
 260          * agg-free clauses of the HAVING qual into WHERE.      This may seem like
 261          * wasting cycles to cater to stupidly-written queries, but there are
 262          * other reasons for doing it.  Firstly, if the query contains no aggs
 263          * at all, then we aren't going to generate an Agg plan node, and so
 264          * there'll be no place to execute HAVING conditions; without this
 265          * transfer, we'd lose the HAVING condition entirely, which is wrong.
 266          * Secondly, when we push down a qual condition into a sub-query, it's
 267          * easiest to push the qual into HAVING always, in case it contains
 268          * aggs, and then let this code sort it out.
 269          *
 270          * Note that both havingQual and parse->jointree->quals are in
 271          * implicitly-ANDed-list form at this point, even though they are
 272          * declared as Node *.
 273          */
 274         newHaving = NIL;
 275         foreach(l, (List *) parse->havingQual)
 276         {
 277                 Node       *havingclause = (Node *) lfirst(l);
 278
 279                 if (contain_agg_clause(havingclause))
 280                         newHaving = lappend(newHaving, havingclause);
 281                 else
 282                         parse->jointree->quals = (Node *)
 283                                 lappend((List *) parse->jointree->quals, havingclause);
 284         }
 285         parse->havingQual = (Node *) newHaving;
 286
 287         /*
 288          * If we have any outer joins, try to reduce them to plain inner
 289          * joins. This step is most easily done after we've done expression
 290          * preprocessing.
 291          */
 292         if (hasOuterJoins)
 293                 reduce_outer_joins(parse);
 294
 295         /*
 296          * See if we can simplify the jointree; opportunities for this may
 297          * come from having pulled up subqueries, or from flattening explicit
 298          * JOIN syntax.  We must do this after flattening JOIN alias
 299          * variables, since eliminating explicit JOIN nodes from the jointree
 300          * will cause get_relids_for_join() to fail.  But it should happen
 301          * after reduce_outer_joins, anyway.
 302          */
 303         parse->jointree = (FromExpr *)
 304                 simplify_jointree(parse, (Node *) parse->jointree);
 305
 306         /*
 307          * Do the main planning.  If we have an inherited target relation,
 308          * that needs special processing, else go straight to
 309          * grouping_planner.
 310          */
 311         if (parse->resultRelation &&
 312                 (lst = expand_inherited_rtentry(parse, parse->resultRelation,
 313                                                                                 false)) != NIL)
 314                 plan = inheritance_planner(parse, lst);
 315         else
 316                 plan = grouping_planner(parse, tuple_fraction);
 317
 318         /*
 319          * If any subplans were generated, or if we're inside a subplan, build
 320          * initPlan list and extParam/allParam sets for plan nodes.
 321          */
 322         if (PlannerPlanId != saved_planid || PlannerQueryLevel > 1)
 323         {
 324                 Cost            initplan_cost = 0;
 325
 326                 /* Prepare extParam/allParam sets for all nodes in tree */
 327                 SS_finalize_plan(plan, parse->rtable);
 328
 329                 /*
 330                  * SS_finalize_plan doesn't handle initPlans, so we have to
 331                  * manually attach them to the topmost plan node, and add their
 332                  * extParams to the topmost node's, too.
 333                  *
 334                  * We also add the total_cost of each initPlan to the startup cost of
 335                  * the top node.  This is a conservative overestimate, since in
 336                  * fact each initPlan might be executed later than plan startup,
 337                  * or even not at all.
 338                  */
 339                 plan->initPlan = PlannerInitPlan;
 340
 341                 foreach(l, plan->initPlan)
 342                 {
 343                         SubPlan    *initplan = (SubPlan *) lfirst(l);
 344
 345                         plan->extParam = bms_add_members(plan->extParam,
 346                                                                                          initplan->plan->extParam);
 347                         /* allParam must include all members of extParam */
 348                         plan->allParam = bms_add_members(plan->allParam,
 349                                                                                          plan->extParam);
 350                         initplan_cost += initplan->plan->total_cost;
 351                 }
 352
 353                 plan->startup_cost += initplan_cost;
 354                 plan->total_cost += initplan_cost;
 355         }
 356
 357         /* Return to outer subquery context */
 358         PlannerQueryLevel--;
 359         PlannerInitPlan = saved_initplan;
 360         /* we do NOT restore PlannerPlanId; that's not an oversight! */
 361
 362         return plan;
 363 }
 364
 365 /*
 366  * preprocess_expression
 367  *              Do subquery_planner's preprocessing work for an expression,
 368  *              which can be a targetlist, a WHERE clause (including JOIN/ON
 369  *              conditions), or a HAVING clause.
 370  */
 371 static Node *
 372 preprocess_expression(Query *parse, Node *expr, int kind)
 373 {
 374         /*
 375          * If the query has any join RTEs, replace join alias variables with
 376          * base-relation variables. We must do this before sublink processing,
 377          * else sublinks expanded out from join aliases wouldn't get
 378          * processed.
 379          */
 380         if (parse->hasJoinRTEs)
 381                 expr = flatten_join_alias_vars(parse, expr);
 382
 383         /*
 384          * If it's a qual or havingQual, canonicalize it.  It seems most useful
 385          * to do this before applying eval_const_expressions, since the latter
 386          * can optimize flattened AND/ORs better than unflattened ones.
 387          *
 388          * Note: all processing of a qual expression after this point must be
 389          * careful to maintain AND/OR flatness --- that is, do not generate a
 390          * tree with AND directly under AND, nor OR directly under OR.
 391          */
 392         if (kind == EXPRKIND_QUAL)
 393         {
 394                 expr = (Node *) canonicalize_qual((Expr *) expr);
 395
 396 #ifdef OPTIMIZER_DEBUG
 397                 printf("After canonicalize_qual()\n");
 398                 pprint(expr);
 399 #endif
 400         }
 401
 402         /*
 403          * Simplify constant expressions.
 404          */
 405         expr = eval_const_expressions(expr);
 406
 407         /* Expand SubLinks to SubPlans */
 408         if (parse->hasSubLinks)
 409                 expr = SS_process_sublinks(expr, (kind == EXPRKIND_QUAL));
 410
 411         /*
 412          * XXX do not insert anything here unless you have grokked the
 413          * comments in SS_replace_correlation_vars ...
 414          */
 415
 416         /* Replace uplevel vars with Param nodes */
 417         if (PlannerQueryLevel > 1)
 418                 expr = SS_replace_correlation_vars(expr);
 419
 420         /*
 421          * If it's a qual or havingQual, convert it to implicit-AND format.
 422          * (We don't want to do this before eval_const_expressions, since the
 423          * latter would be unable to simplify a top-level AND correctly.  Also,
 424          * SS_process_sublinks expects explicit-AND format.)
 425          */
 426         if (kind == EXPRKIND_QUAL)
 427                 expr = (Node *) make_ands_implicit((Expr *) expr);
 428
 429         return expr;
 430 }
 431
 432 /*
 433  * preprocess_qual_conditions
 434  *              Recursively scan the query's jointree and do subquery_planner's
 435  *              preprocessing work on each qual condition found therein.
 436  */
 437 static void
 438 preprocess_qual_conditions(Query *parse, Node *jtnode)
 439 {
 440         if (jtnode == NULL)
 441                 return;
 442         if (IsA(jtnode, RangeTblRef))
 443         {
 444                 /* nothing to do here */
 445         }
 446         else if (IsA(jtnode, FromExpr))
 447         {
 448                 FromExpr   *f = (FromExpr *) jtnode;
 449                 ListCell   *l;
 450
 451                 foreach(l, f->fromlist)
 452                         preprocess_qual_conditions(parse, lfirst(l));
 453
 454                 f->quals = preprocess_expression(parse, f->quals, EXPRKIND_QUAL);
 455         }
 456         else if (IsA(jtnode, JoinExpr))
 457         {
 458                 JoinExpr   *j = (JoinExpr *) jtnode;
 459
 460                 preprocess_qual_conditions(parse, j->larg);
 461                 preprocess_qual_conditions(parse, j->rarg);
 462
 463                 j->quals = preprocess_expression(parse, j->quals, EXPRKIND_QUAL);
 464         }
 465         else
 466                 elog(ERROR, "unrecognized node type: %d",
 467                          (int) nodeTag(jtnode));
 468 }
 469
 470 /*--------------------
 471  * inheritance_planner
 472  *        Generate a plan in the case where the result relation is an
 473  *        inheritance set.
 474  *
 475  * We have to handle this case differently from cases where a source
 476  * relation is an inheritance set.      Source inheritance is expanded at
 477  * the bottom of the plan tree (see allpaths.c), but target inheritance
 478  * has to be expanded at the top.  The reason is that for UPDATE, each
 479  * target relation needs a different targetlist matching its own column
 480  * set.  (This is not so critical for DELETE, but for simplicity we treat
 481  * inherited DELETE the same way.)      Fortunately, the UPDATE/DELETE target
 482  * can never be the nullable side of an outer join, so it's OK to generate
 483  * the plan this way.
 484  *
 485  * parse is the querytree produced by the parser & rewriter.
 486  * inheritlist is an integer list of RT indexes for the result relation set.
 487  *
 488  * Returns a query plan.
 489  *--------------------
 490  */
 491 static Plan *
 492 inheritance_planner(Query *parse, List *inheritlist)
 493 {
 494         int                     parentRTindex = parse->resultRelation;
 495         Oid                     parentOID = getrelid(parentRTindex, parse->rtable);
 496         int                     mainrtlength = length(parse->rtable);
 497         List       *subplans = NIL;
 498         List       *tlist = NIL;
 499         ListCell   *l;
 500
 501         foreach(l, inheritlist)
 502         {
 503                 int                     childRTindex = lfirsti(l);
 504                 Oid                     childOID = getrelid(childRTindex, parse->rtable);
 505                 int                     subrtlength;
 506                 Query      *subquery;
 507                 Plan       *subplan;
 508
 509                 /* Generate modified query with this rel as target */
 510                 subquery = (Query *) adjust_inherited_attrs((Node *) parse,
 511                                                                                                 parentRTindex, parentOID,
 512                                                                                                  childRTindex, childOID);
 513                 /* Generate plan */
 514                 subplan = grouping_planner(subquery, 0.0 /* retrieve all tuples */ );
 515                 subplans = lappend(subplans, subplan);
 516
 517                 /*
 518                  * It's possible that additional RTEs got added to the rangetable
 519                  * due to expansion of inherited source tables (see allpaths.c).
 520                  * If so, we must copy 'em back to the main parse tree's rtable.
 521                  *
 522                  * XXX my goodness this is ugly.  Really need to think about ways to
 523                  * rein in planner's habit of scribbling on its input.
 524                  */
 525                 subrtlength = length(subquery->rtable);
 526                 if (subrtlength > mainrtlength)
 527                 {
 528                         List       *subrt;
 529
 530                         subrt = list_copy_tail(subquery->rtable, mainrtlength);
 531                         parse->rtable = nconc(parse->rtable, subrt);
 532                         mainrtlength = subrtlength;
 533                 }
 534                 /* Save preprocessed tlist from first rel for use in Append */
 535                 if (tlist == NIL)
 536                         tlist = subplan->targetlist;
 537         }
 538
 539         /* Save the target-relations list for the executor, too */
 540         parse->resultRelations = inheritlist;
 541
 542         /* Mark result as unordered (probably unnecessary) */
 543         parse->query_pathkeys = NIL;
 544
 545         return (Plan *) make_append(subplans, true, tlist);
 546 }
 547
 548 /*--------------------
 549  * grouping_planner
 550  *        Perform planning steps related to grouping, aggregation, etc.
 551  *        This primarily means adding top-level processing to the basic
 552  *        query plan produced by query_planner.
 553  *
 554  * parse is the querytree produced by the parser & rewriter.
 555  * tuple_fraction is the fraction of tuples we expect will be retrieved
 556  *
 557  * tuple_fraction is interpreted as follows:
 558  *        0: expect all tuples to be retrieved (normal case)
 559  *        0 < tuple_fraction < 1: expect the given fraction of tuples available
 560  *              from the plan to be retrieved
 561  *        tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
 562  *              expected to be retrieved (ie, a LIMIT specification)
 563  *
 564  * Returns a query plan.  Also, parse->query_pathkeys is returned as the
 565  * actual output ordering of the plan (in pathkey format).
 566  *--------------------
 567  */
 568 static Plan *
 569 grouping_planner(Query *parse, double tuple_fraction)
 570 {
 571         List       *tlist = parse->targetList;
 572         Plan       *result_plan;
 573         List       *current_pathkeys;
 574         List       *sort_pathkeys;
 575
 576         if (parse->setOperations)
 577         {
 578                 List   *set_sortclauses;
 579
 580                 /*
 581                  * Construct the plan for set operations.  The result will not
 582                  * need any work except perhaps a top-level sort and/or LIMIT.
 583                  */
 584                 result_plan = plan_set_operations(parse,
 585                                                                                   &set_sortclauses);
 586
 587                 /*
 588                  * Calculate pathkeys representing the sort order (if any) of the
 589                  * set operation's result.  We have to do this before overwriting
 590                  * the sort key information...
 591                  */
 592                 current_pathkeys = make_pathkeys_for_sortclauses(set_sortclauses,
 593                                                                                                         result_plan->targetlist);
 594                 current_pathkeys = canonicalize_pathkeys(parse, current_pathkeys);
 595
 596                 /*
 597                  * We should not need to call preprocess_targetlist, since we must
 598                  * be in a SELECT query node.  Instead, use the targetlist
 599                  * returned by plan_set_operations (since this tells whether it
 600                  * returned any resjunk columns!), and transfer any sort key
 601                  * information from the original tlist.
 602                  */
 603                 Assert(parse->commandType == CMD_SELECT);
 604
 605                 tlist = postprocess_setop_tlist(result_plan->targetlist, tlist);
 606
 607                 /*
 608                  * Can't handle FOR UPDATE here (parser should have checked
 609                  * already, but let's make sure).
 610                  */
 611                 if (parse->rowMarks)
 612                         ereport(ERROR,
 613                                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 614                                          errmsg("SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT")));
 615
 616                 /*
 617                  * Calculate pathkeys that represent result ordering requirements
 618                  */
 619                 sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
 620                                                                                                           tlist);
 621                 sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
 622         }
 623         else
 624         {
 625                 /* No set operations, do regular planning */
 626                 List       *sub_tlist;
 627                 List       *group_pathkeys;
 628                 AttrNumber *groupColIdx = NULL;
 629                 bool            need_tlist_eval = true;
 630                 QualCost        tlist_cost;
 631                 double          sub_tuple_fraction;
 632                 Path       *cheapest_path;
 633                 Path       *sorted_path;
 634                 double          dNumGroups = 0;
 635                 long            numGroups = 0;
 636                 int                     numAggs = 0;
 637                 int                     numGroupCols = length(parse->groupClause);
 638                 bool            use_hashed_grouping = false;
 639
 640                 /* Preprocess targetlist in case we are inside an INSERT/UPDATE. */
 641                 tlist = preprocess_targetlist(tlist,
 642                                                                           parse->commandType,
 643                                                                           parse->resultRelation,
 644                                                                           parse->rtable);
 645
 646                 /*
 647                  * Add TID targets for rels selected FOR UPDATE (should this be
 648                  * done in preprocess_targetlist?).  The executor uses the TID to
 649                  * know which rows to lock, much as for UPDATE or DELETE.
 650                  */
 651                 if (parse->rowMarks)
 652                 {
 653                         ListCell   *l;
 654
 655                         /*
 656                          * We've got trouble if the FOR UPDATE appears inside
 657                          * grouping, since grouping renders a reference to individual
 658                          * tuple CTIDs invalid.  This is also checked at parse time,
 659                          * but that's insufficient because of rule substitution, query
 660                          * pullup, etc.
 661                          */
 662                         CheckSelectForUpdate(parse);
 663
 664                         /*
 665                          * Currently the executor only supports FOR UPDATE at top
 666                          * level
 667                          */
 668                         if (PlannerQueryLevel > 1)
 669                                 ereport(ERROR,
 670                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 671                                                  errmsg("SELECT FOR UPDATE is not allowed in subqueries")));
 672
 673                         foreach(l, parse->rowMarks)
 674                         {
 675                                 Index           rti = lfirsti(l);
 676                                 char       *resname;
 677                                 Resdom     *resdom;
 678                                 Var                *var;
 679                                 TargetEntry *ctid;
 680
 681                                 resname = (char *) palloc(32);
 682                                 snprintf(resname, 32, "ctid%u", rti);
 683                                 resdom = makeResdom(length(tlist) + 1,
 684                                                                         TIDOID,
 685                                                                         -1,
 686                                                                         resname,
 687                                                                         true);
 688
 689                                 var = makeVar(rti,
 690                                                           SelfItemPointerAttributeNumber,
 691                                                           TIDOID,
 692                                                           -1,
 693                                                           0);
 694
 695                                 ctid = makeTargetEntry(resdom, (Expr *) var);
 696                                 tlist = lappend(tlist, ctid);
 697                         }
 698                 }
 699
 700                 /*
 701                  * Generate appropriate target list for subplan; may be different
 702                  * from tlist if grouping or aggregation is needed.
 703                  */
 704                 sub_tlist = make_subplanTargetList(parse, tlist,
 705                                                                                  &groupColIdx, &need_tlist_eval);
 706
 707                 /*
 708                  * Calculate pathkeys that represent grouping/ordering
 709                  * requirements
 710                  */
 711                 group_pathkeys = make_pathkeys_for_sortclauses(parse->groupClause,
 712                                                                                                            tlist);
 713                 sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
 714                                                                                                           tlist);
 715
 716                 /*
 717                  * Will need actual number of aggregates for estimating costs.
 718                  *
 719                  * Note: we do not attempt to detect duplicate aggregates here; a
 720                  * somewhat-overestimated count is okay for our present purposes.
 721                  *
 722                  * Note: think not that we can turn off hasAggs if we find no aggs.
 723                  * It is possible for constant-expression simplification to remove
 724                  * all explicit references to aggs, but we still have to follow the
 725                  * aggregate semantics (eg, producing only one output row).
 726                  */
 727                 if (parse->hasAggs)
 728                         numAggs = count_agg_clause((Node *) tlist) +
 729                                 count_agg_clause(parse->havingQual);
 730
 731                 /*
 732                  * Figure out whether we need a sorted result from query_planner.
 733                  *
 734                  * If we have a GROUP BY clause, then we want a result sorted
 735                  * properly for grouping.  Otherwise, if there is an ORDER BY
 736                  * clause, we want to sort by the ORDER BY clause.      (Note: if we
 737                  * have both, and ORDER BY is a superset of GROUP BY, it would be
 738                  * tempting to request sort by ORDER BY --- but that might just
 739                  * leave us failing to exploit an available sort order at all.
 740                  * Needs more thought...)
 741                  */
 742                 if (parse->groupClause)
 743                         parse->query_pathkeys = group_pathkeys;
 744                 else if (parse->sortClause)
 745                         parse->query_pathkeys = sort_pathkeys;
 746                 else
 747                         parse->query_pathkeys = NIL;
 748
 749                 /*
 750                  * Adjust tuple_fraction if we see that we are going to apply
 751                  * limiting/grouping/aggregation/etc.  This is not overridable by
 752                  * the caller, since it reflects plan actions that this routine
 753                  * will certainly take, not assumptions about context.
 754                  */
 755                 if (parse->limitCount != NULL)
 756                 {
 757                         /*
 758                          * A LIMIT clause limits the absolute number of tuples
 759                          * returned. However, if it's not a constant LIMIT then we
 760                          * have to punt; for lack of a better idea, assume 10% of the
 761                          * plan's result is wanted.
 762                          */
 763                         double          limit_fraction = 0.0;
 764
 765                         if (IsA(parse->limitCount, Const))
 766                         {
 767                                 Const      *limitc = (Const *) parse->limitCount;
 768                                 int32           count = DatumGetInt32(limitc->constvalue);
 769
 770                                 /*
 771                                  * A NULL-constant LIMIT represents "LIMIT ALL", which we
 772                                  * treat the same as no limit (ie, expect to retrieve all
 773                                  * the tuples).
 774                                  */
 775                                 if (!limitc->constisnull && count > 0)
 776                                 {
 777                                         limit_fraction = (double) count;
 778                                         /* We must also consider the OFFSET, if present */
 779                                         if (parse->limitOffset != NULL)
 780                                         {
 781                                                 if (IsA(parse->limitOffset, Const))
 782                                                 {
 783                                                         int32           offset;
 784
 785                                                         limitc = (Const *) parse->limitOffset;
 786                                                         offset = DatumGetInt32(limitc->constvalue);
 787                                                         if (!limitc->constisnull && offset > 0)
 788                                                                 limit_fraction += (double) offset;
 789                                                 }
 790                                                 else
 791                                                 {
 792                                                         /* OFFSET is an expression ... punt ... */
 793                                                         limit_fraction = 0.10;
 794                                                 }
 795                                         }
 796                                 }
 797                         }
 798                         else
 799                         {
 800                                 /* LIMIT is an expression ... punt ... */
 801                                 limit_fraction = 0.10;
 802                         }
 803
 804                         if (limit_fraction > 0.0)
 805                         {
 806                                 /*
 807                                  * If we have absolute limits from both caller and LIMIT,
 808                                  * use the smaller value; if one is fractional and the
 809                                  * other absolute, treat the fraction as a fraction of the
 810                                  * absolute value; else we can multiply the two fractions
 811                                  * together.
 812                                  */
 813                                 if (tuple_fraction >= 1.0)
 814                                 {
 815                                         if (limit_fraction >= 1.0)
 816                                         {
 817                                                 /* both absolute */
 818                                                 tuple_fraction = Min(tuple_fraction, limit_fraction);
 819                                         }
 820                                         else
 821                                         {
 822                                                 /* caller absolute, limit fractional */
 823                                                 tuple_fraction *= limit_fraction;
 824                                                 if (tuple_fraction < 1.0)
 825                                                         tuple_fraction = 1.0;
 826                                         }
 827                                 }
 828                                 else if (tuple_fraction > 0.0)
 829                                 {
 830                                         if (limit_fraction >= 1.0)
 831                                         {
 832                                                 /* caller fractional, limit absolute */
 833                                                 tuple_fraction *= limit_fraction;
 834                                                 if (tuple_fraction < 1.0)
 835                                                         tuple_fraction = 1.0;
 836                                         }
 837                                         else
 838                                         {
 839                                                 /* both fractional */
 840                                                 tuple_fraction *= limit_fraction;
 841                                         }
 842                                 }
 843                                 else
 844                                 {
 845                                         /* no info from caller, just use limit */
 846                                         tuple_fraction = limit_fraction;
 847                                 }
 848                         }
 849                 }
 850
 851                 /*
 852                  * With grouping or aggregation, the tuple fraction to pass to
 853                  * query_planner() may be different from what it is at top level.
 854                  */
 855                 sub_tuple_fraction = tuple_fraction;
 856
 857                 if (parse->groupClause)
 858                 {
 859                         /*
 860                          * In GROUP BY mode, we have the little problem that we don't
 861                          * really know how many input tuples will be needed to make a
 862                          * group, so we can't translate an output LIMIT count into an
 863                          * input count.  For lack of a better idea, assume 25% of the
 864                          * input data will be processed if there is any output limit.
 865                          * However, if the caller gave us a fraction rather than an
 866                          * absolute count, we can keep using that fraction (which
 867                          * amounts to assuming that all the groups are about the same
 868                          * size).
 869                          */
 870                         if (sub_tuple_fraction >= 1.0)
 871                                 sub_tuple_fraction = 0.25;
 872
 873                         /*
 874                          * If both GROUP BY and ORDER BY are specified, we will need
 875                          * two levels of sort --- and, therefore, certainly need to
 876                          * read all the input tuples --- unless ORDER BY is a subset
 877                          * of GROUP BY.  (We have not yet canonicalized the pathkeys,
 878                          * so must use the slower noncanonical comparison method.)
 879                          */
 880                         if (parse->groupClause && parse->sortClause &&
 881                                 !noncanonical_pathkeys_contained_in(sort_pathkeys,
 882                                                                                                         group_pathkeys))
 883                                 sub_tuple_fraction = 0.0;
 884                 }
 885                 else if (parse->hasAggs)
 886                 {
 887                         /*
 888                          * Ungrouped aggregate will certainly want all the input
 889                          * tuples.
 890                          */
 891                         sub_tuple_fraction = 0.0;
 892                 }
 893                 else if (parse->distinctClause)
 894                 {
 895                         /*
 896                          * SELECT DISTINCT, like GROUP, will absorb an unpredictable
 897                          * number of input tuples per output tuple.  Handle the same
 898                          * way.
 899                          */
 900                         if (sub_tuple_fraction >= 1.0)
 901                                 sub_tuple_fraction = 0.25;
 902                 }
 903
 904                 /*
 905                  * Generate the best unsorted and presorted paths for this Query
 906                  * (but note there may not be any presorted path).
 907                  */
 908                 query_planner(parse, sub_tlist, sub_tuple_fraction,
 909                                           &cheapest_path, &sorted_path);
 910
 911                 /*
 912                  * We couldn't canonicalize group_pathkeys and sort_pathkeys
 913                  * before running query_planner(), so do it now.
 914                  */
 915                 group_pathkeys = canonicalize_pathkeys(parse, group_pathkeys);
 916                 sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
 917
 918                 /*
 919                  * Consider whether we might want to use hashed grouping.
 920                  */
 921                 if (parse->groupClause)
 922                 {
 923                         List       *groupExprs;
 924                         double          cheapest_path_rows;
 925                         int                     cheapest_path_width;
 926
 927                         /*
 928                          * Beware in this section of the possibility that
 929                          * cheapest_path->parent is NULL.  This could happen if user
 930                          * does something silly like SELECT 'foo' GROUP BY 1;
 931                          */
 932                         if (cheapest_path->parent)
 933                         {
 934                                 cheapest_path_rows = cheapest_path->parent->rows;
 935                                 cheapest_path_width = cheapest_path->parent->width;
 936                         }
 937                         else
 938                         {
 939                                 cheapest_path_rows = 1; /* assume non-set result */
 940                                 cheapest_path_width = 100;              /* arbitrary */
 941                         }
 942
 943                         /*
 944                          * Always estimate the number of groups.  We can't do this
 945                          * until after running query_planner(), either.
 946                          */
 947                         groupExprs = get_sortgrouplist_exprs(parse->groupClause,
 948                                                                                                  parse->targetList);
 949                         dNumGroups = estimate_num_groups(parse,
 950                                                                                          groupExprs,
 951                                                                                          cheapest_path_rows);
 952                         /* Also want it as a long int --- but 'ware overflow! */
 953                         numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
 954
 955                         /*
 956                          * Check can't-do-it conditions, including whether the
 957                          * grouping operators are hashjoinable.
 958                          *
 959                          * Executor doesn't support hashed aggregation with DISTINCT
 960                          * aggregates.  (Doing so would imply storing *all* the input
 961                          * values in the hash table, which seems like a certain
 962                          * loser.)
 963                          */
 964                         if (!enable_hashagg || !hash_safe_grouping(parse))
 965                                 use_hashed_grouping = false;
 966                         else if (parse->hasAggs &&
 967                                          (contain_distinct_agg_clause((Node *) tlist) ||
 968                                           contain_distinct_agg_clause(parse->havingQual)))
 969                                 use_hashed_grouping = false;
 970                         else
 971                         {
 972                                 /*
 973                                  * Use hashed grouping if (a) we think we can fit the
 974                                  * hashtable into work_mem, *and* (b) the estimated cost is
 975                                  * no more than doing it the other way.  While avoiding
 976                                  * the need for sorted input is usually a win, the fact
 977                                  * that the output won't be sorted may be a loss; so we
 978                                  * need to do an actual cost comparison.
 979                                  *
 980                                  * In most cases we have no good way to estimate the size of
 981                                  * the transition value needed by an aggregate;
 982                                  * arbitrarily assume it is 100 bytes.  Also set the
 983                                  * overhead per hashtable entry at 64 bytes.
 984                                  */
 985                                 int                     hashentrysize = cheapest_path_width + 64 + numAggs * 100;
 986
 987                                 if (hashentrysize * dNumGroups <= work_mem * 1024L)
 988                                 {
 989                                         /*
 990                                          * Okay, do the cost comparison.  We need to consider
 991                                          * cheapest_path + hashagg [+ final sort] versus
 992                                          * either cheapest_path [+ sort] + group or agg [+
 993                                          * final sort] or presorted_path + group or agg [+
 994                                          * final sort] where brackets indicate a step that may
 995                                          * not be needed. We assume query_planner() will have
 996                                          * returned a presorted path only if it's a winner
 997                                          * compared to cheapest_path for this purpose.
 998                                          *
 999                                          * These path variables are dummies that just hold cost
1000                                          * fields; we don't make actual Paths for these steps.
1001                                          */
1002                                         Path            hashed_p;
1003                                         Path            sorted_p;
1004
1005                                         cost_agg(&hashed_p, parse,
1006                                                          AGG_HASHED, numAggs,
1007                                                          numGroupCols, dNumGroups,
1008                                                          cheapest_path->startup_cost,
1009                                                          cheapest_path->total_cost,
1010                                                          cheapest_path_rows);
1011                                         /* Result of hashed agg is always unsorted */
1012                                         if (sort_pathkeys)
1013                                                 cost_sort(&hashed_p, parse, sort_pathkeys,
1014                                                                   hashed_p.total_cost,
1015                                                                   dNumGroups,
1016                                                                   cheapest_path_width);
1017
1018                                         if (sorted_path)
1019                                         {
1020                                                 sorted_p.startup_cost = sorted_path->startup_cost;
1021                                                 sorted_p.total_cost = sorted_path->total_cost;
1022                                                 current_pathkeys = sorted_path->pathkeys;
1023                                         }
1024                                         else
1025                                         {
1026                                                 sorted_p.startup_cost = cheapest_path->startup_cost;
1027                                                 sorted_p.total_cost = cheapest_path->total_cost;
1028                                                 current_pathkeys = cheapest_path->pathkeys;
1029                                         }
1030                                         if (!pathkeys_contained_in(group_pathkeys,
1031                                                                                            current_pathkeys))
1032                                         {
1033                                                 cost_sort(&sorted_p, parse, group_pathkeys,
1034                                                                   sorted_p.total_cost,
1035                                                                   cheapest_path_rows,
1036                                                                   cheapest_path_width);
1037                                                 current_pathkeys = group_pathkeys;
1038                                         }
1039                                         if (parse->hasAggs)
1040                                                 cost_agg(&sorted_p, parse,
1041                                                                  AGG_SORTED, numAggs,
1042                                                                  numGroupCols, dNumGroups,
1043                                                                  sorted_p.startup_cost,
1044                                                                  sorted_p.total_cost,
1045                                                                  cheapest_path_rows);
1046                                         else
1047                                                 cost_group(&sorted_p, parse,
1048                                                                    numGroupCols, dNumGroups,
1049                                                                    sorted_p.startup_cost,
1050                                                                    sorted_p.total_cost,
1051                                                                    cheapest_path_rows);
1052                                         /* The Agg or Group node will preserve ordering */
1053                                         if (sort_pathkeys &&
1054                                                 !pathkeys_contained_in(sort_pathkeys,
1055                                                                                            current_pathkeys))
1056                                         {
1057                                                 cost_sort(&sorted_p, parse, sort_pathkeys,
1058                                                                   sorted_p.total_cost,
1059                                                                   dNumGroups,
1060                                                                   cheapest_path_width);
1061                                         }
1062
1063                                         /*
1064                                          * Now make the decision using the top-level tuple
1065                                          * fraction.  First we have to convert an absolute
1066                                          * count (LIMIT) into fractional form.
1067                                          */
1068                                         if (tuple_fraction >= 1.0)
1069                                                 tuple_fraction /= dNumGroups;
1070
1071                                         if (compare_fractional_path_costs(&hashed_p, &sorted_p,
1072                                                                                                           tuple_fraction) < 0)
1073                                         {
1074                                                 /* Hashed is cheaper, so use it */
1075                                                 use_hashed_grouping = true;
1076                                         }
1077                                 }
1078                         }
1079                 }
1080
1081                 /*
1082                  * Select the best path and create a plan to execute it.
1083                  *
1084                  * If we are doing hashed grouping, we will always read all the input
1085                  * tuples, so use the cheapest-total path.      Otherwise, trust
1086                  * query_planner's decision about which to use.
1087                  */
1088                 if (sorted_path && !use_hashed_grouping)
1089                 {
1090                         result_plan = create_plan(parse, sorted_path);
1091                         current_pathkeys = sorted_path->pathkeys;
1092                 }
1093                 else
1094                 {
1095                         result_plan = create_plan(parse, cheapest_path);
1096                         current_pathkeys = cheapest_path->pathkeys;
1097                 }
1098
1099                 /*
1100                  * create_plan() returns a plan with just a "flat" tlist of
1101                  * required Vars.  Usually we need to insert the sub_tlist as the
1102                  * tlist of the top plan node.  However, we can skip that if we
1103                  * determined that whatever query_planner chose to return will be
1104                  * good enough.
1105                  */
1106                 if (need_tlist_eval)
1107                 {
1108                         /*
1109                          * If the top-level plan node is one that cannot do expression
1110                          * evaluation, we must insert a Result node to project the
1111                          * desired tlist.
1112                          */
1113                         if (!is_projection_capable_plan(result_plan))
1114                         {
1115                                 result_plan = (Plan *) make_result(sub_tlist, NULL,
1116                                                                                                    result_plan);
1117                         }
1118                         else
1119                         {
1120                                 /*
1121                                  * Otherwise, just replace the subplan's flat tlist with
1122                                  * the desired tlist.
1123                                  */
1124                                 result_plan->targetlist = sub_tlist;
1125                         }
1126
1127                         /*
1128                          * Also, account for the cost of evaluation of the sub_tlist.
1129                          *
1130                          * Up to now, we have only been dealing with "flat" tlists,
1131                          * containing just Vars.  So their evaluation cost is zero
1132                          * according to the model used by cost_qual_eval() (or if you
1133                          * prefer, the cost is factored into cpu_tuple_cost).  Thus we
1134                          * can avoid accounting for tlist cost throughout
1135                          * query_planner() and subroutines.  But now we've inserted a
1136                          * tlist that might contain actual operators, sub-selects, etc
1137                          * --- so we'd better account for its cost.
1138                          *
1139                          * Below this point, any tlist eval cost for added-on nodes
1140                          * should be accounted for as we create those nodes.
1141                          * Presently, of the node types we can add on, only Agg and
1142                          * Group project new tlists (the rest just copy their input
1143                          * tuples) --- so make_agg() and make_group() are responsible
1144                          * for computing the added cost.
1145                          */
1146                         cost_qual_eval(&tlist_cost, sub_tlist);
1147                         result_plan->startup_cost += tlist_cost.startup;
1148                         result_plan->total_cost += tlist_cost.startup +
1149                                 tlist_cost.per_tuple * result_plan->plan_rows;
1150                 }
1151                 else
1152                 {
1153                         /*
1154                          * Since we're using query_planner's tlist and not the one
1155                          * make_subplanTargetList calculated, we have to refigure any
1156                          * grouping-column indexes make_subplanTargetList computed.
1157                          */
1158                         locate_grouping_columns(parse, tlist, result_plan->targetlist,
1159                                                                         groupColIdx);
1160                 }
1161
1162                 /*
1163                  * Insert AGG or GROUP node if needed, plus an explicit sort step
1164                  * if necessary.
1165                  *
1166                  * HAVING clause, if any, becomes qual of the Agg node
1167                  */
1168                 if (use_hashed_grouping)
1169                 {
1170                         /* Hashed aggregate plan --- no sort needed */
1171                         result_plan = (Plan *) make_agg(parse,
1172                                                                                         tlist,
1173                                                                                         (List *) parse->havingQual,
1174                                                                                         AGG_HASHED,
1175                                                                                         numGroupCols,
1176                                                                                         groupColIdx,
1177                                                                                         numGroups,
1178                                                                                         numAggs,
1179                                                                                         result_plan);
1180                         /* Hashed aggregation produces randomly-ordered results */
1181                         current_pathkeys = NIL;
1182                 }
1183                 else if (parse->hasAggs)
1184                 {
1185                         /* Plain aggregate plan --- sort if needed */
1186                         AggStrategy aggstrategy;
1187
1188                         if (parse->groupClause)
1189                         {
1190                                 if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
1191                                 {
1192                                         result_plan = (Plan *)
1193                                                 make_sort_from_groupcols(parse,
1194                                                                                                  parse->groupClause,
1195                                                                                                  groupColIdx,
1196                                                                                                  result_plan);
1197                                         current_pathkeys = group_pathkeys;
1198                                 }
1199                                 aggstrategy = AGG_SORTED;
1200
1201                                 /*
1202                                  * The AGG node will not change the sort ordering of its
1203                                  * groups, so current_pathkeys describes the result too.
1204                                  */
1205                         }
1206                         else
1207                         {
1208                                 aggstrategy = AGG_PLAIN;
1209                                 /* Result will be only one row anyway; no sort order */
1210                                 current_pathkeys = NIL;
1211                         }
1212
1213                         result_plan = (Plan *) make_agg(parse,
1214                                                                                         tlist,
1215                                                                                         (List *) parse->havingQual,
1216                                                                                         aggstrategy,
1217                                                                                         numGroupCols,
1218                                                                                         groupColIdx,
1219                                                                                         numGroups,
1220                                                                                         numAggs,
1221                                                                                         result_plan);
1222                 }
1223                 else
1224                 {
1225                         /*
1226                          * If there are no Aggs, we shouldn't have any HAVING qual
1227                          * anymore
1228                          */
1229                         Assert(parse->havingQual == NULL);
1230
1231                         /*
1232                          * If we have a GROUP BY clause, insert a group node (plus the
1233                          * appropriate sort node, if necessary).
1234                          */
1235                         if (parse->groupClause)
1236                         {
1237                                 /*
1238                                  * Add an explicit sort if we couldn't make the path come
1239                                  * out the way the GROUP node needs it.
1240                                  */
1241                                 if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
1242                                 {
1243                                         result_plan = (Plan *)
1244                                                 make_sort_from_groupcols(parse,
1245                                                                                                  parse->groupClause,
1246                                                                                                  groupColIdx,
1247                                                                                                  result_plan);
1248                                         current_pathkeys = group_pathkeys;
1249                                 }
1250
1251                                 result_plan = (Plan *) make_group(parse,
1252                                                                                                   tlist,
1253                                                                                                   numGroupCols,
1254                                                                                                   groupColIdx,
1255                                                                                                   dNumGroups,
1256                                                                                                   result_plan);
1257                                 /* The Group node won't change sort ordering */
1258                         }
1259                 }
1260         }                                                       /* end of if (setOperations) */
1261
1262         /*
1263          * If we were not able to make the plan come out in the right order,
1264          * add an explicit sort step.
1265          */
1266         if (parse->sortClause)
1267         {
1268                 if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
1269                 {
1270                         result_plan = (Plan *)
1271                                 make_sort_from_sortclauses(parse,
1272                                                                                    parse->sortClause,
1273                                                                                    result_plan);
1274                         current_pathkeys = sort_pathkeys;
1275                 }
1276         }
1277
1278         /*
1279          * If there is a DISTINCT clause, add the UNIQUE node.
1280          */
1281         if (parse->distinctClause)
1282         {
1283                 result_plan = (Plan *) make_unique(result_plan, parse->distinctClause);
1284
1285                 /*
1286                  * If there was grouping or aggregation, leave plan_rows as-is
1287                  * (ie, assume the result was already mostly unique).  If not,
1288                  * it's reasonable to assume the UNIQUE filter has effects
1289                  * comparable to GROUP BY.
1290                  */
1291                 if (!parse->groupClause && !parse->hasAggs)
1292                 {
1293                         List       *distinctExprs;
1294
1295                         distinctExprs = get_sortgrouplist_exprs(parse->distinctClause,
1296                                                                                                         parse->targetList);
1297                         result_plan->plan_rows = estimate_num_groups(parse,
1298                                                                                                                  distinctExprs,
1299                                                                                                  result_plan->plan_rows);
1300                 }
1301         }
1302
1303         /*
1304          * Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
1305          */
1306         if (parse->limitOffset || parse->limitCount)
1307         {
1308                 result_plan = (Plan *) make_limit(result_plan,
1309                                                                                   parse->limitOffset,
1310                                                                                   parse->limitCount);
1311         }
1312
1313         /*
1314          * Return the actual output ordering in query_pathkeys for possible
1315          * use by an outer query level.
1316          */
1317         parse->query_pathkeys = current_pathkeys;
1318
1319         return result_plan;
1320 }
1321
1322 /*
1323  * hash_safe_grouping - are grouping operators hashable?
1324  *
1325  * We assume hashed aggregation will work if the datatype's equality operator
1326  * is marked hashjoinable.
1327  */
1328 static bool
1329 hash_safe_grouping(Query *parse)
1330 {
1331         ListCell   *gl;
1332
1333         foreach(gl, parse->groupClause)
1334         {
1335                 GroupClause *grpcl = (GroupClause *) lfirst(gl);
1336                 TargetEntry *tle = get_sortgroupclause_tle(grpcl, parse->targetList);
1337                 Operator        optup;
1338                 bool            oprcanhash;
1339
1340                 optup = equality_oper(tle->resdom->restype, true);
1341                 if (!optup)
1342                         return false;
1343                 oprcanhash = ((Form_pg_operator) GETSTRUCT(optup))->oprcanhash;
1344                 ReleaseSysCache(optup);
1345                 if (!oprcanhash)
1346                         return false;
1347         }
1348         return true;
1349 }
1350
1351 /*---------------
1352  * make_subplanTargetList
1353  *        Generate appropriate target list when grouping is required.
1354  *
1355  * When grouping_planner inserts Aggregate or Group plan nodes above
1356  * the result of query_planner, we typically want to pass a different
1357  * target list to query_planner than the outer plan nodes should have.
1358  * This routine generates the correct target list for the subplan.
1359  *
1360  * The initial target list passed from the parser already contains entries
1361  * for all ORDER BY and GROUP BY expressions, but it will not have entries
1362  * for variables used only in HAVING clauses; so we need to add those
1363  * variables to the subplan target list.  Also, if we are doing either
1364  * grouping or aggregation, we flatten all expressions except GROUP BY items
1365  * into their component variables; the other expressions will be computed by
1366  * the inserted nodes rather than by the subplan.  For example,
1367  * given a query like
1368  *              SELECT a+b,SUM(c+d) FROM table GROUP BY a+b;
1369  * we want to pass this targetlist to the subplan:
1370  *              a,b,c,d,a+b
1371  * where the a+b target will be used by the Sort/Group steps, and the
1372  * other targets will be used for computing the final results.  (In the
1373  * above example we could theoretically suppress the a and b targets and
1374  * pass down only c,d,a+b, but it's not really worth the trouble to
1375  * eliminate simple var references from the subplan.  We will avoid doing
1376  * the extra computation to recompute a+b at the outer level; see
1377  * replace_vars_with_subplan_refs() in setrefs.c.)
1378  *
1379  * If we are grouping or aggregating, *and* there are no non-Var grouping
1380  * expressions, then the returned tlist is effectively dummy; we do not
1381  * need to force it to be evaluated, because all the Vars it contains
1382  * should be present in the output of query_planner anyway.
1383  *
1384  * 'parse' is the query being processed.
1385  * 'tlist' is the query's target list.
1386  * 'groupColIdx' receives an array of column numbers for the GROUP BY
1387  *                      expressions (if there are any) in the subplan's target list.
1388  * 'need_tlist_eval' is set true if we really need to evaluate the
1389  *                      result tlist.
1390  *
1391  * The result is the targetlist to be passed to the subplan.
1392  *---------------
1393  */
1394 static List *
1395 make_subplanTargetList(Query *parse,
1396                                            List *tlist,
1397                                            AttrNumber **groupColIdx,
1398                                            bool *need_tlist_eval)
1399 {
1400         List       *sub_tlist;
1401         List       *extravars;
1402         int                     numCols;
1403
1404         *groupColIdx = NULL;
1405
1406         /*
1407          * If we're not grouping or aggregating, nothing to do here;
1408          * query_planner should receive the unmodified target list.
1409          */
1410         if (!parse->hasAggs && !parse->groupClause)
1411         {
1412                 *need_tlist_eval = true;
1413                 return tlist;
1414         }
1415
1416         /*
1417          * Otherwise, start with a "flattened" tlist (having just the vars
1418          * mentioned in the targetlist and HAVING qual --- but not upper-
1419          * level Vars; they will be replaced by Params later on).
1420          */
1421         sub_tlist = flatten_tlist(tlist);
1422         extravars = pull_var_clause(parse->havingQual, false);
1423         sub_tlist = add_to_flat_tlist(sub_tlist, extravars);
1424         freeList(extravars);
1425         *need_tlist_eval = false;       /* only eval if not flat tlist */
1426
1427         /*
1428          * If grouping, create sub_tlist entries for all GROUP BY expressions
1429          * (GROUP BY items that are simple Vars should be in the list
1430          * already), and make an array showing where the group columns are in
1431          * the sub_tlist.
1432          */
1433         numCols = length(parse->groupClause);
1434         if (numCols > 0)
1435         {
1436                 int                     keyno = 0;
1437                 AttrNumber *grpColIdx;
1438                 ListCell   *gl;
1439
1440                 grpColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
1441                 *groupColIdx = grpColIdx;
1442
1443                 foreach(gl, parse->groupClause)
1444                 {
1445                         GroupClause             *grpcl = (GroupClause *) lfirst(gl);
1446                         Node                    *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1447                         TargetEntry             *te = NULL;
1448                         ListCell                *sl;
1449
1450                         /* Find or make a matching sub_tlist entry */
1451                         foreach(sl, sub_tlist)
1452                         {
1453                                 te = (TargetEntry *) lfirst(sl);
1454                                 if (equal(groupexpr, te->expr))
1455                                         break;
1456                         }
1457                         if (!sl)
1458                         {
1459                                 te = makeTargetEntry(makeResdom(length(sub_tlist) + 1,
1460                                                                                                 exprType(groupexpr),
1461                                                                                                 exprTypmod(groupexpr),
1462                                                                                                 NULL,
1463                                                                                                 false),
1464                                                                          (Expr *) groupexpr);
1465                                 sub_tlist = lappend(sub_tlist, te);
1466                                 *need_tlist_eval = true;                /* it's not flat anymore */
1467                         }
1468
1469                         /* and save its resno */
1470                         grpColIdx[keyno++] = te->resdom->resno;
1471                 }
1472         }
1473
1474         return sub_tlist;
1475 }
1476
1477 /*
1478  * locate_grouping_columns
1479  *              Locate grouping columns in the tlist chosen by query_planner.
1480  *
1481  * This is only needed if we don't use the sub_tlist chosen by
1482  * make_subplanTargetList.      We have to forget the column indexes found
1483  * by that routine and re-locate the grouping vars in the real sub_tlist.
1484  */
1485 static void
1486 locate_grouping_columns(Query *parse,
1487                                                 List *tlist,
1488                                                 List *sub_tlist,
1489                                                 AttrNumber *groupColIdx)
1490 {
1491         int                     keyno = 0;
1492         ListCell   *gl;
1493
1494         /*
1495          * No work unless grouping.
1496          */
1497         if (!parse->groupClause)
1498         {
1499                 Assert(groupColIdx == NULL);
1500                 return;
1501         }
1502         Assert(groupColIdx != NULL);
1503
1504         foreach(gl, parse->groupClause)
1505         {
1506                 GroupClause             *grpcl = (GroupClause *) lfirst(gl);
1507                 Node                    *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1508                 TargetEntry             *te = NULL;
1509                 ListCell                *sl;
1510
1511                 foreach(sl, sub_tlist)
1512                 {
1513                         te = (TargetEntry *) lfirst(sl);
1514                         if (equal(groupexpr, te->expr))
1515                                 break;
1516                 }
1517                 if (!sl)
1518                         elog(ERROR, "failed to locate grouping columns");
1519
1520                 groupColIdx[keyno++] = te->resdom->resno;
1521         }
1522 }
1523
1524 /*
1525  * postprocess_setop_tlist
1526  *        Fix up targetlist returned by plan_set_operations().
1527  *
1528  * We need to transpose sort key info from the orig_tlist into new_tlist.
1529  * NOTE: this would not be good enough if we supported resjunk sort keys
1530  * for results of set operations --- then, we'd need to project a whole
1531  * new tlist to evaluate the resjunk columns.  For now, just ereport if we
1532  * find any resjunk columns in orig_tlist.
1533  */
1534 static List *
1535 postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
1536 {
1537         ListCell   *l;
1538         ListCell   *orig_tlist_item = list_head(orig_tlist);
1539
1540         foreach(l, new_tlist)
1541         {
1542                 TargetEntry *new_tle = (TargetEntry *) lfirst(l);
1543                 TargetEntry *orig_tle;
1544
1545                 /* ignore resjunk columns in setop result */
1546                 if (new_tle->resdom->resjunk)
1547                         continue;
1548
1549                 Assert(orig_tlist_item != NULL);
1550                 orig_tle = (TargetEntry *) lfirst(orig_tlist_item);
1551                 orig_tlist_item = lnext(orig_tlist_item);
1552                 if (orig_tle->resdom->resjunk)  /* should not happen */
1553                         elog(ERROR, "resjunk output columns are not implemented");
1554                 Assert(new_tle->resdom->resno == orig_tle->resdom->resno);
1555                 Assert(new_tle->resdom->restype == orig_tle->resdom->restype);
1556                 new_tle->resdom->ressortgroupref = orig_tle->resdom->ressortgroupref;
1557         }
1558         if (orig_tlist_item != NULL)
1559                 elog(ERROR, "resjunk output columns are not implemented");
1560         return new_tlist;
1561 }