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) 1996-2002, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.153 2003/05/06 00:20:32 tgl 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_ININFO 3
  51
  52
  53 static Node *preprocess_expression(Query *parse, Node *expr, int kind);
  54 static void preprocess_qual_conditions(Query *parse, Node *jtnode);
  55 static Plan *inheritance_planner(Query *parse, List *inheritlist);
  56 static Plan *grouping_planner(Query *parse, double tuple_fraction);
  57 static bool hash_safe_grouping(Query *parse);
  58 static List *make_subplanTargetList(Query *parse, List *tlist,
  59                                            AttrNumber **groupColIdx, bool *need_tlist_eval);
  60 static void locate_grouping_columns(Query *parse,
  61                                                                         List *tlist,
  62                                                                         List *sub_tlist,
  63                                                                         AttrNumber *groupColIdx);
  64 static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
  65
  66
  67 /*****************************************************************************
  68  *
  69  *         Query optimizer entry point
  70  *
  71  *****************************************************************************/
  72 Plan *
  73 planner(Query *parse, bool isCursor, int cursorOptions)
  74 {
  75         double          tuple_fraction;
  76         Plan       *result_plan;
  77         Index           save_PlannerQueryLevel;
  78         List       *save_PlannerParamVar;
  79
  80         /*
  81          * The planner can be called recursively (an example is when
  82          * eval_const_expressions tries to pre-evaluate an SQL function). So,
  83          * these global state variables must be saved and restored.
  84          *
  85          * These vars cannot be moved into the Query structure since their whole
  86          * purpose is communication across multiple sub-Queries.
  87          *
  88          * Note we do NOT save and restore PlannerPlanId: it exists to assign
  89          * unique IDs to SubPlan nodes, and we want those IDs to be unique for
  90          * the life of a backend.  Also, PlannerInitPlan is saved/restored in
  91          * subquery_planner, not here.
  92          */
  93         save_PlannerQueryLevel = PlannerQueryLevel;
  94         save_PlannerParamVar = PlannerParamVar;
  95
  96         /* Initialize state for handling outer-level references and params */
  97         PlannerQueryLevel = 0;          /* will be 1 in top-level subquery_planner */
  98         PlannerParamVar = NIL;
  99
 100         /* Determine what fraction of the plan is likely to be scanned */
 101         if (isCursor)
 102         {
 103                 /*
 104                  * We have no real idea how many tuples the user will ultimately
 105                  * FETCH from a cursor, but it seems a good bet that he
 106                  * doesn't want 'em all.  Optimize for 10% retrieval (you
 107                  * gotta better number?  Should this be a SETtable parameter?)
 108                  */
 109                 tuple_fraction = 0.10;
 110         }
 111         else
 112         {
 113                 /* Default assumption is we need all the tuples */
 114                 tuple_fraction = 0.0;
 115         }
 116
 117         /* primary planning entry point (may recurse for subqueries) */
 118         result_plan = subquery_planner(parse, tuple_fraction);
 119
 120         Assert(PlannerQueryLevel == 0);
 121
 122         /*
 123          * If creating a plan for a scrollable cursor, make sure it can
 124          * run backwards on demand.  Add a Material node at the top at need.
 125          */
 126         if (isCursor && (cursorOptions & CURSOR_OPT_SCROLL))
 127         {
 128                 if (!ExecSupportsBackwardScan(result_plan))
 129                         result_plan = materialize_finished_plan(result_plan);
 130         }
 131
 132         /* executor wants to know total number of Params used overall */
 133         result_plan->nParamExec = length(PlannerParamVar);
 134
 135         /* final cleanup of the plan */
 136         set_plan_references(result_plan, parse->rtable);
 137
 138         /* restore state for outer planner, if any */
 139         PlannerQueryLevel = save_PlannerQueryLevel;
 140         PlannerParamVar = save_PlannerParamVar;
 141
 142         return result_plan;
 143 }
 144
 145
 146 /*--------------------
 147  * subquery_planner
 148  *        Invokes the planner on a subquery.  We recurse to here for each
 149  *        sub-SELECT found in the query tree.
 150  *
 151  * parse is the querytree produced by the parser & rewriter.
 152  * tuple_fraction is the fraction of tuples we expect will be retrieved.
 153  * tuple_fraction is interpreted as explained for grouping_planner, below.
 154  *
 155  * Basically, this routine does the stuff that should only be done once
 156  * per Query object.  It then calls grouping_planner.  At one time,
 157  * grouping_planner could be invoked recursively on the same Query object;
 158  * that's not currently true, but we keep the separation between the two
 159  * routines anyway, in case we need it again someday.
 160  *
 161  * subquery_planner will be called recursively to handle sub-Query nodes
 162  * found within the query's expressions and rangetable.
 163  *
 164  * Returns a query plan.
 165  *--------------------
 166  */
 167 Plan *
 168 subquery_planner(Query *parse, double tuple_fraction)
 169 {
 170         List       *saved_initplan = PlannerInitPlan;
 171         int                     saved_planid = PlannerPlanId;
 172         bool            hasOuterJoins;
 173         Plan       *plan;
 174         List       *newHaving;
 175         List       *lst;
 176
 177         /* Set up for a new level of subquery */
 178         PlannerQueryLevel++;
 179         PlannerInitPlan = NIL;
 180
 181         /*
 182          * Look for IN clauses at the top level of WHERE, and transform them
 183          * into joins.  Note that this step only handles IN clauses originally
 184          * at top level of WHERE; if we pull up any subqueries in the next step,
 185          * their INs are processed just before pulling them up.
 186          */
 187         parse->in_info_list = NIL;
 188         if (parse->hasSubLinks)
 189                 parse->jointree->quals = pull_up_IN_clauses(parse,
 190                                                                                                         parse->jointree->quals);
 191
 192         /*
 193          * Check to see if any subqueries in the rangetable can be merged into
 194          * this query.
 195          */
 196         parse->jointree = (FromExpr *)
 197                 pull_up_subqueries(parse, (Node *) parse->jointree, false);
 198
 199         /*
 200          * Detect whether any rangetable entries are RTE_JOIN kind; if not,
 201          * we can avoid the expense of doing flatten_join_alias_vars().  Also
 202          * check for outer joins --- if none, we can skip reduce_outer_joins().
 203          * This must be done after we have done pull_up_subqueries, of course.
 204          */
 205         parse->hasJoinRTEs = false;
 206         hasOuterJoins = false;
 207         foreach(lst, parse->rtable)
 208         {
 209                 RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
 210
 211                 if (rte->rtekind == RTE_JOIN)
 212                 {
 213                         parse->hasJoinRTEs = true;
 214                         if (IS_OUTER_JOIN(rte->jointype))
 215                         {
 216                                 hasOuterJoins = true;
 217                                 /* Can quit scanning once we find an outer join */
 218                                 break;
 219                         }
 220                 }
 221         }
 222
 223         /*
 224          * Do expression preprocessing on targetlist and quals.
 225          */
 226         parse->targetList = (List *)
 227                 preprocess_expression(parse, (Node *) parse->targetList,
 228                                                           EXPRKIND_TARGET);
 229
 230         preprocess_qual_conditions(parse, (Node *) parse->jointree);
 231
 232         parse->havingQual = preprocess_expression(parse, parse->havingQual,
 233                                                                                           EXPRKIND_QUAL);
 234
 235         parse->in_info_list = (List *)
 236                 preprocess_expression(parse, (Node *) parse->in_info_list,
 237                                                           EXPRKIND_ININFO);
 238
 239         /* Also need to preprocess expressions for function RTEs */
 240         foreach(lst, parse->rtable)
 241         {
 242                 RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
 243
 244                 if (rte->rtekind == RTE_FUNCTION)
 245                         rte->funcexpr = preprocess_expression(parse, rte->funcexpr,
 246                                                                                                   EXPRKIND_RTFUNC);
 247         }
 248
 249         /*
 250          * A HAVING clause without aggregates is equivalent to a WHERE clause
 251          * (except it can only refer to grouped fields).  Transfer any
 252          * agg-free clauses of the HAVING qual into WHERE.      This may seem like
 253          * wasting cycles to cater to stupidly-written queries, but there are
 254          * other reasons for doing it.  Firstly, if the query contains no aggs
 255          * at all, then we aren't going to generate an Agg plan node, and so
 256          * there'll be no place to execute HAVING conditions; without this
 257          * transfer, we'd lose the HAVING condition entirely, which is wrong.
 258          * Secondly, when we push down a qual condition into a sub-query, it's
 259          * easiest to push the qual into HAVING always, in case it contains
 260          * aggs, and then let this code sort it out.
 261          *
 262          * Note that both havingQual and parse->jointree->quals are in
 263          * implicitly-ANDed-list form at this point, even though they are
 264          * declared as Node *.  Also note that contain_agg_clause does not
 265          * recurse into sub-selects, which is exactly what we need here.
 266          */
 267         newHaving = NIL;
 268         foreach(lst, (List *) parse->havingQual)
 269         {
 270                 Node       *havingclause = (Node *) lfirst(lst);
 271
 272                 if (contain_agg_clause(havingclause))
 273                         newHaving = lappend(newHaving, havingclause);
 274                 else
 275                         parse->jointree->quals = (Node *)
 276                                 lappend((List *) parse->jointree->quals, havingclause);
 277         }
 278         parse->havingQual = (Node *) newHaving;
 279
 280         /*
 281          * If we have any outer joins, try to reduce them to plain inner joins.
 282          * This step is most easily done after we've done expression preprocessing.
 283          */
 284         if (hasOuterJoins)
 285                 reduce_outer_joins(parse);
 286
 287         /*
 288          * See if we can simplify the jointree; opportunities for this may come
 289          * from having pulled up subqueries, or from flattening explicit JOIN
 290          * syntax.  We must do this after flattening JOIN alias variables, since
 291          * eliminating explicit JOIN nodes from the jointree will cause
 292          * get_relids_for_join() to fail.  But it should happen after
 293          * reduce_outer_joins, anyway.
 294          */
 295         parse->jointree = (FromExpr *)
 296                 simplify_jointree(parse, (Node *) parse->jointree);
 297
 298         /*
 299          * Do the main planning.  If we have an inherited target relation,
 300          * that needs special processing, else go straight to
 301          * grouping_planner.
 302          */
 303         if (parse->resultRelation &&
 304                 (lst = expand_inherited_rtentry(parse, parse->resultRelation,
 305                                                                                 false)) != NIL)
 306                 plan = inheritance_planner(parse, lst);
 307         else
 308                 plan = grouping_planner(parse, tuple_fraction);
 309
 310         /*
 311          * If any subplans were generated, or if we're inside a subplan, build
 312          * initPlan list and extParam/allParam sets for plan nodes.
 313          */
 314         if (PlannerPlanId != saved_planid || PlannerQueryLevel > 1)
 315         {
 316                 Cost    initplan_cost = 0;
 317
 318                 /* Prepare extParam/allParam sets for all nodes in tree */
 319                 SS_finalize_plan(plan, parse->rtable);
 320
 321                 /*
 322                  * SS_finalize_plan doesn't handle initPlans, so we have to manually
 323                  * attach them to the topmost plan node, and add their extParams to
 324                  * the topmost node's, too.
 325                  *
 326                  * We also add the total_cost of each initPlan to the startup cost
 327                  * of the top node.  This is a conservative overestimate, since in
 328                  * fact each initPlan might be executed later than plan startup, or
 329                  * even not at all.
 330                  */
 331                 plan->initPlan = PlannerInitPlan;
 332
 333                 foreach(lst, plan->initPlan)
 334                 {
 335                         SubPlan    *initplan = (SubPlan *) lfirst(lst);
 336
 337                         plan->extParam = bms_add_members(plan->extParam,
 338                                                                                          initplan->plan->extParam);
 339                         initplan_cost += initplan->plan->total_cost;
 340                 }
 341
 342                 plan->startup_cost += initplan_cost;
 343                 plan->total_cost += initplan_cost;
 344         }
 345
 346         /* Return to outer subquery context */
 347         PlannerQueryLevel--;
 348         PlannerInitPlan = saved_initplan;
 349         /* we do NOT restore PlannerPlanId; that's not an oversight! */
 350
 351         return plan;
 352 }
 353
 354 /*
 355  * preprocess_expression
 356  *              Do subquery_planner's preprocessing work for an expression,
 357  *              which can be a targetlist, a WHERE clause (including JOIN/ON
 358  *              conditions), or a HAVING clause.
 359  */
 360 static Node *
 361 preprocess_expression(Query *parse, Node *expr, int kind)
 362 {
 363         /*
 364          * If the query has any join RTEs, replace join alias variables with
 365          * base-relation variables. We must do this before sublink processing,
 366          * else sublinks expanded out from join aliases wouldn't get processed.
 367          */
 368         if (parse->hasJoinRTEs)
 369                 expr = flatten_join_alias_vars(parse, expr);
 370
 371         /*
 372          * Simplify constant expressions.
 373          *
 374          * Note that at this point quals have not yet been converted to
 375          * implicit-AND form, so we can apply eval_const_expressions directly.
 376          */
 377         expr = eval_const_expressions(expr);
 378
 379         /*
 380          * If it's a qual or havingQual, canonicalize it, and convert it to
 381          * implicit-AND format.
 382          *
 383          * XXX Is there any value in re-applying eval_const_expressions after
 384          * canonicalize_qual?
 385          */
 386         if (kind == EXPRKIND_QUAL)
 387         {
 388                 expr = (Node *) canonicalize_qual((Expr *) expr, true);
 389
 390 #ifdef OPTIMIZER_DEBUG
 391                 printf("After canonicalize_qual()\n");
 392                 pprint(expr);
 393 #endif
 394         }
 395
 396         /* Expand SubLinks to SubPlans */
 397         if (parse->hasSubLinks)
 398                 expr = SS_process_sublinks(expr, (kind == EXPRKIND_QUAL));
 399
 400         /* Replace uplevel vars with Param nodes */
 401         if (PlannerQueryLevel > 1)
 402                 expr = SS_replace_correlation_vars(expr);
 403
 404         return expr;
 405 }
 406
 407 /*
 408  * preprocess_qual_conditions
 409  *              Recursively scan the query's jointree and do subquery_planner's
 410  *              preprocessing work on each qual condition found therein.
 411  */
 412 static void
 413 preprocess_qual_conditions(Query *parse, Node *jtnode)
 414 {
 415         if (jtnode == NULL)
 416                 return;
 417         if (IsA(jtnode, RangeTblRef))
 418         {
 419                 /* nothing to do here */
 420         }
 421         else if (IsA(jtnode, FromExpr))
 422         {
 423                 FromExpr   *f = (FromExpr *) jtnode;
 424                 List       *l;
 425
 426                 foreach(l, f->fromlist)
 427                         preprocess_qual_conditions(parse, lfirst(l));
 428
 429                 f->quals = preprocess_expression(parse, f->quals, EXPRKIND_QUAL);
 430         }
 431         else if (IsA(jtnode, JoinExpr))
 432         {
 433                 JoinExpr   *j = (JoinExpr *) jtnode;
 434
 435                 preprocess_qual_conditions(parse, j->larg);
 436                 preprocess_qual_conditions(parse, j->rarg);
 437
 438                 j->quals = preprocess_expression(parse, j->quals, EXPRKIND_QUAL);
 439         }
 440         else
 441                 elog(ERROR, "preprocess_qual_conditions: unexpected node type %d",
 442                          nodeTag(jtnode));
 443 }
 444
 445 /*--------------------
 446  * inheritance_planner
 447  *        Generate a plan in the case where the result relation is an
 448  *        inheritance set.
 449  *
 450  * We have to handle this case differently from cases where a source
 451  * relation is an inheritance set.      Source inheritance is expanded at
 452  * the bottom of the plan tree (see allpaths.c), but target inheritance
 453  * has to be expanded at the top.  The reason is that for UPDATE, each
 454  * target relation needs a different targetlist matching its own column
 455  * set.  (This is not so critical for DELETE, but for simplicity we treat
 456  * inherited DELETE the same way.)      Fortunately, the UPDATE/DELETE target
 457  * can never be the nullable side of an outer join, so it's OK to generate
 458  * the plan this way.
 459  *
 460  * parse is the querytree produced by the parser & rewriter.
 461  * inheritlist is an integer list of RT indexes for the result relation set.
 462  *
 463  * Returns a query plan.
 464  *--------------------
 465  */
 466 static Plan *
 467 inheritance_planner(Query *parse, List *inheritlist)
 468 {
 469         int                     parentRTindex = parse->resultRelation;
 470         Oid                     parentOID = getrelid(parentRTindex, parse->rtable);
 471         int                     mainrtlength = length(parse->rtable);
 472         List       *subplans = NIL;
 473         List       *tlist = NIL;
 474         List       *l;
 475
 476         foreach(l, inheritlist)
 477         {
 478                 int                     childRTindex = lfirsti(l);
 479                 Oid                     childOID = getrelid(childRTindex, parse->rtable);
 480                 int                     subrtlength;
 481                 Query      *subquery;
 482                 Plan       *subplan;
 483
 484                 /* Generate modified query with this rel as target */
 485                 subquery = (Query *) adjust_inherited_attrs((Node *) parse,
 486                                                                                                 parentRTindex, parentOID,
 487                                                                                                  childRTindex, childOID);
 488                 /* Generate plan */
 489                 subplan = grouping_planner(subquery, 0.0 /* retrieve all tuples */ );
 490                 subplans = lappend(subplans, subplan);
 491                 /*
 492                  * It's possible that additional RTEs got added to the rangetable
 493                  * due to expansion of inherited source tables (see allpaths.c).
 494                  * If so, we must copy 'em back to the main parse tree's rtable.
 495                  *
 496                  * XXX my goodness this is ugly.  Really need to think about ways
 497                  * to rein in planner's habit of scribbling on its input.
 498                  */
 499                 subrtlength = length(subquery->rtable);
 500                 if (subrtlength > mainrtlength)
 501                 {
 502                         List   *subrt = subquery->rtable;
 503
 504                         while (mainrtlength-- > 0) /* wish we had nthcdr() */
 505                                 subrt = lnext(subrt);
 506                         parse->rtable = nconc(parse->rtable, subrt);
 507                         mainrtlength = subrtlength;
 508                 }
 509                 /* Save preprocessed tlist from first rel for use in Append */
 510                 if (tlist == NIL)
 511                         tlist = subplan->targetlist;
 512         }
 513
 514         /* Save the target-relations list for the executor, too */
 515         parse->resultRelations = inheritlist;
 516
 517         /* Mark result as unordered (probably unnecessary) */
 518         parse->query_pathkeys = NIL;
 519
 520         return (Plan *) make_append(subplans, true, tlist);
 521 }
 522
 523 /*--------------------
 524  * grouping_planner
 525  *        Perform planning steps related to grouping, aggregation, etc.
 526  *        This primarily means adding top-level processing to the basic
 527  *        query plan produced by query_planner.
 528  *
 529  * parse is the querytree produced by the parser & rewriter.
 530  * tuple_fraction is the fraction of tuples we expect will be retrieved
 531  *
 532  * tuple_fraction is interpreted as follows:
 533  *        0: expect all tuples to be retrieved (normal case)
 534  *        0 < tuple_fraction < 1: expect the given fraction of tuples available
 535  *              from the plan to be retrieved
 536  *        tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
 537  *              expected to be retrieved (ie, a LIMIT specification)
 538  *
 539  * Returns a query plan.  Also, parse->query_pathkeys is returned as the
 540  * actual output ordering of the plan (in pathkey format).
 541  *--------------------
 542  */
 543 static Plan *
 544 grouping_planner(Query *parse, double tuple_fraction)
 545 {
 546         List       *tlist = parse->targetList;
 547         Plan       *result_plan;
 548         List       *current_pathkeys;
 549         List       *sort_pathkeys;
 550
 551         if (parse->setOperations)
 552         {
 553                 /*
 554                  * Construct the plan for set operations.  The result will not
 555                  * need any work except perhaps a top-level sort and/or LIMIT.
 556                  */
 557                 result_plan = plan_set_operations(parse);
 558
 559                 /*
 560                  * We should not need to call preprocess_targetlist, since we must
 561                  * be in a SELECT query node.  Instead, use the targetlist
 562                  * returned by plan_set_operations (since this tells whether it
 563                  * returned any resjunk columns!), and transfer any sort key
 564                  * information from the original tlist.
 565                  */
 566                 Assert(parse->commandType == CMD_SELECT);
 567
 568                 tlist = postprocess_setop_tlist(result_plan->targetlist, tlist);
 569
 570                 /*
 571                  * Can't handle FOR UPDATE here (parser should have checked
 572                  * already, but let's make sure).
 573                  */
 574                 if (parse->rowMarks)
 575                         elog(ERROR, "SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT");
 576
 577                 /*
 578                  * We set current_pathkeys NIL indicating we do not know sort
 579                  * order.  This is correct when the top set operation is UNION
 580                  * ALL, since the appended-together results are unsorted even if
 581                  * the subplans were sorted.  For other set operations we could be
 582                  * smarter --- room for future improvement!
 583                  */
 584                 current_pathkeys = NIL;
 585
 586                 /*
 587                  * Calculate pathkeys that represent ordering requirements
 588                  */
 589                 sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
 590                                                                                                           tlist);
 591                 sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
 592         }
 593         else
 594         {
 595                 /* No set operations, do regular planning */
 596                 List       *sub_tlist;
 597                 List       *group_pathkeys;
 598                 AttrNumber *groupColIdx = NULL;
 599                 bool            need_tlist_eval = true;
 600                 QualCost        tlist_cost;
 601                 double          sub_tuple_fraction;
 602                 Path       *cheapest_path;
 603                 Path       *sorted_path;
 604                 double          dNumGroups = 0;
 605                 long            numGroups = 0;
 606                 int                     numAggs = 0;
 607                 int                     numGroupCols = length(parse->groupClause);
 608                 bool            use_hashed_grouping = false;
 609
 610                 /* Preprocess targetlist in case we are inside an INSERT/UPDATE. */
 611                 tlist = preprocess_targetlist(tlist,
 612                                                                           parse->commandType,
 613                                                                           parse->resultRelation,
 614                                                                           parse->rtable);
 615
 616                 /*
 617                  * Add TID targets for rels selected FOR UPDATE (should this be
 618                  * done in preprocess_targetlist?).  The executor uses the TID to
 619                  * know which rows to lock, much as for UPDATE or DELETE.
 620                  */
 621                 if (parse->rowMarks)
 622                 {
 623                         List       *l;
 624
 625                         /*
 626                          * We've got trouble if the FOR UPDATE appears inside
 627                          * grouping, since grouping renders a reference to individual
 628                          * tuple CTIDs invalid.  This is also checked at parse time,
 629                          * but that's insufficient because of rule substitution, query
 630                          * pullup, etc.
 631                          */
 632                         CheckSelectForUpdate(parse);
 633
 634                         /*
 635                          * Currently the executor only supports FOR UPDATE at top
 636                          * level
 637                          */
 638                         if (PlannerQueryLevel > 1)
 639                                 elog(ERROR, "SELECT FOR UPDATE is not allowed in subselects");
 640
 641                         foreach(l, parse->rowMarks)
 642                         {
 643                                 Index           rti = lfirsti(l);
 644                                 char       *resname;
 645                                 Resdom     *resdom;
 646                                 Var                *var;
 647                                 TargetEntry *ctid;
 648
 649                                 resname = (char *) palloc(32);
 650                                 snprintf(resname, 32, "ctid%u", rti);
 651                                 resdom = makeResdom(length(tlist) + 1,
 652                                                                         TIDOID,
 653                                                                         -1,
 654                                                                         resname,
 655                                                                         true);
 656
 657                                 var = makeVar(rti,
 658                                                           SelfItemPointerAttributeNumber,
 659                                                           TIDOID,
 660                                                           -1,
 661                                                           0);
 662
 663                                 ctid = makeTargetEntry(resdom, (Expr *) var);
 664                                 tlist = lappend(tlist, ctid);
 665                         }
 666                 }
 667
 668                 /*
 669                  * Generate appropriate target list for subplan; may be different
 670                  * from tlist if grouping or aggregation is needed.
 671                  */
 672                 sub_tlist = make_subplanTargetList(parse, tlist,
 673                                                                                    &groupColIdx, &need_tlist_eval);
 674
 675                 /*
 676                  * Calculate pathkeys that represent grouping/ordering
 677                  * requirements
 678                  */
 679                 group_pathkeys = make_pathkeys_for_sortclauses(parse->groupClause,
 680                                                                                                            tlist);
 681                 sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
 682                                                                                                           tlist);
 683
 684                 /*
 685                  * Will need actual number of aggregates for estimating costs.
 686                  * Also, it's possible that optimization has eliminated all
 687                  * aggregates, and we may as well check for that here.
 688                  *
 689                  * Note: we do not attempt to detect duplicate aggregates here;
 690                  * a somewhat-overestimated count is okay for our present purposes.
 691                  */
 692                 if (parse->hasAggs)
 693                 {
 694                         numAggs = count_agg_clause((Node *) tlist) +
 695                                 count_agg_clause(parse->havingQual);
 696                         if (numAggs == 0)
 697                                 parse->hasAggs = false;
 698                 }
 699
 700                 /*
 701                  * Figure out whether we need a sorted result from query_planner.
 702                  *
 703                  * If we have a GROUP BY clause, then we want a result sorted
 704                  * properly for grouping.  Otherwise, if there is an ORDER BY
 705                  * clause, we want to sort by the ORDER BY clause.      (Note: if we
 706                  * have both, and ORDER BY is a superset of GROUP BY, it would be
 707                  * tempting to request sort by ORDER BY --- but that might just
 708                  * leave us failing to exploit an available sort order at all.
 709                  * Needs more thought...)
 710                  */
 711                 if (parse->groupClause)
 712                         parse->query_pathkeys = group_pathkeys;
 713                 else if (parse->sortClause)
 714                         parse->query_pathkeys = sort_pathkeys;
 715                 else
 716                         parse->query_pathkeys = NIL;
 717
 718                 /*
 719                  * Adjust tuple_fraction if we see that we are going to apply
 720                  * limiting/grouping/aggregation/etc.  This is not overridable by
 721                  * the caller, since it reflects plan actions that this routine
 722                  * will certainly take, not assumptions about context.
 723                  */
 724                 if (parse->limitCount != NULL)
 725                 {
 726                         /*
 727                          * A LIMIT clause limits the absolute number of tuples
 728                          * returned. However, if it's not a constant LIMIT then we
 729                          * have to punt; for lack of a better idea, assume 10% of the
 730                          * plan's result is wanted.
 731                          */
 732                         double          limit_fraction = 0.0;
 733
 734                         if (IsA(parse->limitCount, Const))
 735                         {
 736                                 Const      *limitc = (Const *) parse->limitCount;
 737                                 int32           count = DatumGetInt32(limitc->constvalue);
 738
 739                                 /*
 740                                  * A NULL-constant LIMIT represents "LIMIT ALL", which we
 741                                  * treat the same as no limit (ie, expect to retrieve all
 742                                  * the tuples).
 743                                  */
 744                                 if (!limitc->constisnull && count > 0)
 745                                 {
 746                                         limit_fraction = (double) count;
 747                                         /* We must also consider the OFFSET, if present */
 748                                         if (parse->limitOffset != NULL)
 749                                         {
 750                                                 if (IsA(parse->limitOffset, Const))
 751                                                 {
 752                                                         int32           offset;
 753
 754                                                         limitc = (Const *) parse->limitOffset;
 755                                                         offset = DatumGetInt32(limitc->constvalue);
 756                                                         if (!limitc->constisnull && offset > 0)
 757                                                                 limit_fraction += (double) offset;
 758                                                 }
 759                                                 else
 760                                                 {
 761                                                         /* OFFSET is an expression ... punt ... */
 762                                                         limit_fraction = 0.10;
 763                                                 }
 764                                         }
 765                                 }
 766                         }
 767                         else
 768                         {
 769                                 /* LIMIT is an expression ... punt ... */
 770                                 limit_fraction = 0.10;
 771                         }
 772
 773                         if (limit_fraction > 0.0)
 774                         {
 775                                 /*
 776                                  * If we have absolute limits from both caller and LIMIT,
 777                                  * use the smaller value; if one is fractional and the
 778                                  * other absolute, treat the fraction as a fraction of the
 779                                  * absolute value; else we can multiply the two fractions
 780                                  * together.
 781                                  */
 782                                 if (tuple_fraction >= 1.0)
 783                                 {
 784                                         if (limit_fraction >= 1.0)
 785                                         {
 786                                                 /* both absolute */
 787                                                 tuple_fraction = Min(tuple_fraction, limit_fraction);
 788                                         }
 789                                         else
 790                                         {
 791                                                 /* caller absolute, limit fractional */
 792                                                 tuple_fraction *= limit_fraction;
 793                                                 if (tuple_fraction < 1.0)
 794                                                         tuple_fraction = 1.0;
 795                                         }
 796                                 }
 797                                 else if (tuple_fraction > 0.0)
 798                                 {
 799                                         if (limit_fraction >= 1.0)
 800                                         {
 801                                                 /* caller fractional, limit absolute */
 802                                                 tuple_fraction *= limit_fraction;
 803                                                 if (tuple_fraction < 1.0)
 804                                                         tuple_fraction = 1.0;
 805                                         }
 806                                         else
 807                                         {
 808                                                 /* both fractional */
 809                                                 tuple_fraction *= limit_fraction;
 810                                         }
 811                                 }
 812                                 else
 813                                 {
 814                                         /* no info from caller, just use limit */
 815                                         tuple_fraction = limit_fraction;
 816                                 }
 817                         }
 818                 }
 819
 820                 /*
 821                  * With grouping or aggregation, the tuple fraction to pass to
 822                  * query_planner() may be different from what it is at top level.
 823                  */
 824                 sub_tuple_fraction = tuple_fraction;
 825
 826                 if (parse->groupClause)
 827                 {
 828                         /*
 829                          * In GROUP BY mode, we have the little problem that we don't
 830                          * really know how many input tuples will be needed to make a
 831                          * group, so we can't translate an output LIMIT count into an
 832                          * input count.  For lack of a better idea, assume 25% of the
 833                          * input data will be processed if there is any output limit.
 834                          * However, if the caller gave us a fraction rather than an
 835                          * absolute count, we can keep using that fraction (which
 836                          * amounts to assuming that all the groups are about the same
 837                          * size).
 838                          */
 839                         if (sub_tuple_fraction >= 1.0)
 840                                 sub_tuple_fraction = 0.25;
 841
 842                         /*
 843                          * If both GROUP BY and ORDER BY are specified, we will need
 844                          * two levels of sort --- and, therefore, certainly need to
 845                          * read all the input tuples --- unless ORDER BY is a subset
 846                          * of GROUP BY.  (We have not yet canonicalized the pathkeys,
 847                          * so must use the slower noncanonical comparison method.)
 848                          */
 849                         if (parse->groupClause && parse->sortClause &&
 850                                 !noncanonical_pathkeys_contained_in(sort_pathkeys,
 851                                                                                                         group_pathkeys))
 852                                 sub_tuple_fraction = 0.0;
 853                 }
 854                 else if (parse->hasAggs)
 855                 {
 856                         /*
 857                          * Ungrouped aggregate will certainly want all the input
 858                          * tuples.
 859                          */
 860                         sub_tuple_fraction = 0.0;
 861                 }
 862                 else if (parse->distinctClause)
 863                 {
 864                         /*
 865                          * SELECT DISTINCT, like GROUP, will absorb an unpredictable
 866                          * number of input tuples per output tuple.  Handle the same
 867                          * way.
 868                          */
 869                         if (sub_tuple_fraction >= 1.0)
 870                                 sub_tuple_fraction = 0.25;
 871                 }
 872
 873                 /*
 874                  * Generate the best unsorted and presorted paths for this Query
 875                  * (but note there may not be any presorted path).
 876                  */
 877                 query_planner(parse, sub_tlist, sub_tuple_fraction,
 878                                           &cheapest_path, &sorted_path);
 879
 880                 /*
 881                  * We couldn't canonicalize group_pathkeys and sort_pathkeys before
 882                  * running query_planner(), so do it now.
 883                  */
 884                 group_pathkeys = canonicalize_pathkeys(parse, group_pathkeys);
 885                 sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
 886
 887                 /*
 888                  * Consider whether we might want to use hashed grouping.
 889                  */
 890                 if (parse->groupClause)
 891                 {
 892                         List   *groupExprs;
 893
 894                         /*
 895                          * Always estimate the number of groups.  We can't do this until
 896                          * after running query_planner(), either.
 897                          */
 898                         groupExprs = get_sortgrouplist_exprs(parse->groupClause,
 899                                                                                                  parse->targetList);
 900                         dNumGroups = estimate_num_groups(parse,
 901                                                                                          groupExprs,
 902                                                                                          cheapest_path->parent->rows);
 903                         /* Also want it as a long int --- but 'ware overflow! */
 904                         numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
 905
 906                         /*
 907                          * Check can't-do-it conditions, including whether the grouping
 908                          * operators are hashjoinable.
 909                          *
 910                          * Executor doesn't support hashed aggregation with DISTINCT
 911                          * aggregates.  (Doing so would imply storing *all* the input
 912                          * values in the hash table, which seems like a certain loser.)
 913                          */
 914                         if (!enable_hashagg || !hash_safe_grouping(parse))
 915                                 use_hashed_grouping = false;
 916                         else if (parse->hasAggs &&
 917                                          (contain_distinct_agg_clause((Node *) tlist) ||
 918                                           contain_distinct_agg_clause(parse->havingQual)))
 919                                 use_hashed_grouping = false;
 920                         else
 921                         {
 922                                 /*
 923                                  * Use hashed grouping if (a) we think we can fit the
 924                                  * hashtable into SortMem, *and* (b) the estimated cost
 925                                  * is no more than doing it the other way.  While avoiding
 926                                  * the need for sorted input is usually a win, the fact
 927                                  * that the output won't be sorted may be a loss; so we
 928                                  * need to do an actual cost comparison.
 929                                  *
 930                                  * In most cases we have no good way to estimate the size of
 931                                  * the transition value needed by an aggregate; arbitrarily
 932                                  * assume it is 100 bytes.  Also set the overhead per hashtable
 933                                  * entry at 64 bytes.
 934                                  */
 935                                 int             hashentrysize = cheapest_path->parent->width + 64 +
 936                                         numAggs * 100;
 937
 938                                 if (hashentrysize * dNumGroups <= SortMem * 1024L)
 939                                 {
 940                                         /*
 941                                          * Okay, do the cost comparison.  We need to consider
 942                                          *      cheapest_path + hashagg [+ final sort]
 943                                          * versus either
 944                                          *      cheapest_path [+ sort] + group or agg [+ final sort]
 945                                          * or
 946                                          *      presorted_path + group or agg [+ final sort]
 947                                          * where brackets indicate a step that may not be needed.
 948                                          * We assume query_planner() will have returned a
 949                                          * presorted path only if it's a winner compared to
 950                                          * cheapest_path for this purpose.
 951                                          *
 952                                          * These path variables are dummies that just hold cost
 953                                          * fields; we don't make actual Paths for these steps.
 954                                          */
 955                                         Path            hashed_p;
 956                                         Path            sorted_p;
 957
 958                                         cost_agg(&hashed_p, parse,
 959                                                          AGG_HASHED, numAggs,
 960                                                          numGroupCols, dNumGroups,
 961                                                          cheapest_path->startup_cost,
 962                                                          cheapest_path->total_cost,
 963                                                          cheapest_path->parent->rows);
 964                                         /* Result of hashed agg is always unsorted */
 965                                         if (sort_pathkeys)
 966                                                 cost_sort(&hashed_p, parse, sort_pathkeys,
 967                                                                   hashed_p.total_cost,
 968                                                                   dNumGroups,
 969                                                                   cheapest_path->parent->width);
 970
 971                                         if (sorted_path)
 972                                         {
 973                                                 sorted_p.startup_cost = sorted_path->startup_cost;
 974                                                 sorted_p.total_cost = sorted_path->total_cost;
 975                                                 current_pathkeys = sorted_path->pathkeys;
 976                                         }
 977                                         else
 978                                         {
 979                                                 sorted_p.startup_cost = cheapest_path->startup_cost;
 980                                                 sorted_p.total_cost = cheapest_path->total_cost;
 981                                                 current_pathkeys = cheapest_path->pathkeys;
 982                                         }
 983                                         if (!pathkeys_contained_in(group_pathkeys,
 984                                                                                            current_pathkeys))
 985                                         {
 986                                                 cost_sort(&sorted_p, parse, group_pathkeys,
 987                                                                   sorted_p.total_cost,
 988                                                                   cheapest_path->parent->rows,
 989                                                                   cheapest_path->parent->width);
 990                                                 current_pathkeys = group_pathkeys;
 991                                         }
 992                                         if (parse->hasAggs)
 993                                                 cost_agg(&sorted_p, parse,
 994                                                                  AGG_SORTED, numAggs,
 995                                                                  numGroupCols, dNumGroups,
 996                                                                  sorted_p.startup_cost,
 997                                                                  sorted_p.total_cost,
 998                                                                  cheapest_path->parent->rows);
 999                                         else
1000                                                 cost_group(&sorted_p, parse,
1001                                                                    numGroupCols, dNumGroups,
1002                                                                    sorted_p.startup_cost,
1003                                                                    sorted_p.total_cost,
1004                                                                    cheapest_path->parent->rows);
1005                                         /* The Agg or Group node will preserve ordering */
1006                                         if (sort_pathkeys &&
1007                                                 !pathkeys_contained_in(sort_pathkeys,
1008                                                                                            current_pathkeys))
1009                                         {
1010                                                 cost_sort(&sorted_p, parse, sort_pathkeys,
1011                                                                   sorted_p.total_cost,
1012                                                                   dNumGroups,
1013                                                                   cheapest_path->parent->width);
1014                                         }
1015
1016                                         /*
1017                                          * Now make the decision using the top-level tuple
1018                                          * fraction.  First we have to convert an absolute
1019                                          * count (LIMIT) into fractional form.
1020                                          */
1021                                         if (tuple_fraction >= 1.0)
1022                                                 tuple_fraction /= dNumGroups;
1023
1024                                         if (compare_fractional_path_costs(&hashed_p, &sorted_p,
1025                                                                                                           tuple_fraction) < 0)
1026                                         {
1027                                                 /* Hashed is cheaper, so use it */
1028                                                 use_hashed_grouping = true;
1029                                         }
1030                                 }
1031                         }
1032                 }
1033
1034                 /*
1035                  * Select the best path and create a plan to execute it.
1036                  *
1037                  * If we are doing hashed grouping, we will always read all the
1038                  * input tuples, so use the cheapest-total path.  Otherwise,
1039                  * trust query_planner's decision about which to use.
1040                  */
1041                 if (sorted_path && !use_hashed_grouping)
1042                 {
1043                         result_plan = create_plan(parse, sorted_path);
1044                         current_pathkeys = sorted_path->pathkeys;
1045                 }
1046                 else
1047                 {
1048                         result_plan = create_plan(parse, cheapest_path);
1049                         current_pathkeys = cheapest_path->pathkeys;
1050                 }
1051
1052                 /*
1053                  * create_plan() returns a plan with just a "flat" tlist of required
1054                  * Vars.  Usually we need to insert the sub_tlist as the tlist of the
1055                  * top plan node.  However, we can skip that if we determined that
1056                  * whatever query_planner chose to return will be good enough.
1057                  */
1058                 if (need_tlist_eval)
1059                 {
1060                         /*
1061                          * If the top-level plan node is one that cannot do expression
1062                          * evaluation, we must insert a Result node to project the desired
1063                          * tlist.
1064                          * Currently, the only plan node we might see here that falls into
1065                          * that category is Append.
1066                          */
1067                         if (IsA(result_plan, Append))
1068                         {
1069                                 result_plan = (Plan *) make_result(sub_tlist, NULL,
1070                                                                                                    result_plan);
1071                         }
1072                         else
1073                         {
1074                                 /*
1075                                  * Otherwise, just replace the subplan's flat tlist with
1076                                  * the desired tlist.
1077                                  */
1078                                 result_plan->targetlist = sub_tlist;
1079                         }
1080                         /*
1081                          * Also, account for the cost of evaluation of the sub_tlist.
1082                          *
1083                          * Up to now, we have only been dealing with "flat" tlists,
1084                          * containing just Vars.  So their evaluation cost is zero
1085                          * according to the model used by cost_qual_eval() (or if you
1086                          * prefer, the cost is factored into cpu_tuple_cost).  Thus we can
1087                          * avoid accounting for tlist cost throughout query_planner() and
1088                          * subroutines.  But now we've inserted a tlist that might contain
1089                          * actual operators, sub-selects, etc --- so we'd better account
1090                          * for its cost.
1091                          *
1092                          * Below this point, any tlist eval cost for added-on nodes should
1093                          * be accounted for as we create those nodes.  Presently, of the
1094                          * node types we can add on, only Agg and Group project new tlists
1095                          * (the rest just copy their input tuples) --- so make_agg() and
1096                          * make_group() are responsible for computing the added cost.
1097                          */
1098                         cost_qual_eval(&tlist_cost, sub_tlist);
1099                         result_plan->startup_cost += tlist_cost.startup;
1100                         result_plan->total_cost += tlist_cost.startup +
1101                                 tlist_cost.per_tuple * result_plan->plan_rows;
1102                 }
1103                 else
1104                 {
1105                         /*
1106                          * Since we're using query_planner's tlist and not the one
1107                          * make_subplanTargetList calculated, we have to refigure
1108                          * any grouping-column indexes make_subplanTargetList computed.
1109                          */
1110                         locate_grouping_columns(parse, tlist, result_plan->targetlist,
1111                                                                         groupColIdx);
1112                 }
1113
1114                 /*
1115                  * Insert AGG or GROUP node if needed, plus an explicit sort step
1116                  * if necessary.
1117                  *
1118                  * HAVING clause, if any, becomes qual of the Agg node
1119                  */
1120                 if (use_hashed_grouping)
1121                 {
1122                         /* Hashed aggregate plan --- no sort needed */
1123                         result_plan = (Plan *) make_agg(parse,
1124                                                                                         tlist,
1125                                                                                         (List *) parse->havingQual,
1126                                                                                         AGG_HASHED,
1127                                                                                         numGroupCols,
1128                                                                                         groupColIdx,
1129                                                                                         numGroups,
1130                                                                                         numAggs,
1131                                                                                         result_plan);
1132                         /* Hashed aggregation produces randomly-ordered results */
1133                         current_pathkeys = NIL;
1134                 }
1135                 else if (parse->hasAggs)
1136                 {
1137                         /* Plain aggregate plan --- sort if needed */
1138                         AggStrategy aggstrategy;
1139
1140                         if (parse->groupClause)
1141                         {
1142                                 if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
1143                                 {
1144                                         result_plan = (Plan *)
1145                                                 make_sort_from_groupcols(parse,
1146                                                                                                  parse->groupClause,
1147                                                                                                  groupColIdx,
1148                                                                                                  result_plan);
1149                                         current_pathkeys = group_pathkeys;
1150                                 }
1151                                 aggstrategy = AGG_SORTED;
1152                                 /*
1153                                  * The AGG node will not change the sort ordering of its
1154                                  * groups, so current_pathkeys describes the result too.
1155                                  */
1156                         }
1157                         else
1158                         {
1159                                 aggstrategy = AGG_PLAIN;
1160                                 /* Result will be only one row anyway; no sort order */
1161                                 current_pathkeys = NIL;
1162                         }
1163
1164                         result_plan = (Plan *) make_agg(parse,
1165                                                                                         tlist,
1166                                                                                         (List *) parse->havingQual,
1167                                                                                         aggstrategy,
1168                                                                                         numGroupCols,
1169                                                                                         groupColIdx,
1170                                                                                         numGroups,
1171                                                                                         numAggs,
1172                                                                                         result_plan);
1173                 }
1174                 else
1175                 {
1176                         /*
1177                          * If there are no Aggs, we shouldn't have any HAVING qual anymore
1178                          */
1179                         Assert(parse->havingQual == NULL);
1180
1181                         /*
1182                          * If we have a GROUP BY clause, insert a group node (plus the
1183                          * appropriate sort node, if necessary).
1184                          */
1185                         if (parse->groupClause)
1186                         {
1187                                 /*
1188                                  * Add an explicit sort if we couldn't make the path come out
1189                                  * the way the GROUP node needs it.
1190                                  */
1191                                 if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
1192                                 {
1193                                         result_plan = (Plan *)
1194                                                 make_sort_from_groupcols(parse,
1195                                                                                                  parse->groupClause,
1196                                                                                                  groupColIdx,
1197                                                                                                  result_plan);
1198                                         current_pathkeys = group_pathkeys;
1199                                 }
1200
1201                                 result_plan = (Plan *) make_group(parse,
1202                                                                                                   tlist,
1203                                                                                                   numGroupCols,
1204                                                                                                   groupColIdx,
1205                                                                                                   dNumGroups,
1206                                                                                                   result_plan);
1207                                 /* The Group node won't change sort ordering */
1208                         }
1209                 }
1210         } /* end of if (setOperations) */
1211
1212         /*
1213          * If we were not able to make the plan come out in the right order,
1214          * add an explicit sort step.
1215          */
1216         if (parse->sortClause)
1217         {
1218                 if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
1219                 {
1220                         result_plan = (Plan *)
1221                                 make_sort_from_sortclauses(parse,
1222                                                                                    tlist,
1223                                                                                    result_plan,
1224                                                                                    parse->sortClause);
1225                         current_pathkeys = sort_pathkeys;
1226                 }
1227         }
1228
1229         /*
1230          * If there is a DISTINCT clause, add the UNIQUE node.
1231          */
1232         if (parse->distinctClause)
1233         {
1234                 result_plan = (Plan *) make_unique(tlist, result_plan,
1235                                                                                    parse->distinctClause);
1236                 /*
1237                  * If there was grouping or aggregation, leave plan_rows as-is
1238                  * (ie, assume the result was already mostly unique).  If not,
1239                  * it's reasonable to assume the UNIQUE filter has effects
1240                  * comparable to GROUP BY.
1241                  */
1242                 if (!parse->groupClause && !parse->hasAggs)
1243                 {
1244                         List   *distinctExprs;
1245
1246                         distinctExprs = get_sortgrouplist_exprs(parse->distinctClause,
1247                                                                                                         parse->targetList);
1248                         result_plan->plan_rows = estimate_num_groups(parse,
1249                                                                                                                  distinctExprs,
1250                                                                                                                  result_plan->plan_rows);
1251                 }
1252         }
1253
1254         /*
1255          * Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
1256          */
1257         if (parse->limitOffset || parse->limitCount)
1258         {
1259                 result_plan = (Plan *) make_limit(tlist, result_plan,
1260                                                                                   parse->limitOffset,
1261                                                                                   parse->limitCount);
1262         }
1263
1264         /*
1265          * Return the actual output ordering in query_pathkeys for possible
1266          * use by an outer query level.
1267          */
1268         parse->query_pathkeys = current_pathkeys;
1269
1270         return result_plan;
1271 }
1272
1273 /*
1274  * hash_safe_grouping - are grouping operators hashable?
1275  *
1276  * We assume hashed aggregation will work if the datatype's equality operator
1277  * is marked hashjoinable.
1278  */
1279 static bool
1280 hash_safe_grouping(Query *parse)
1281 {
1282         List       *gl;
1283
1284         foreach(gl, parse->groupClause)
1285         {
1286                 GroupClause *grpcl = (GroupClause *) lfirst(gl);
1287                 TargetEntry *tle = get_sortgroupclause_tle(grpcl, parse->targetList);
1288                 Operator        optup;
1289                 bool            oprcanhash;
1290
1291                 optup = equality_oper(tle->resdom->restype, false);
1292                 oprcanhash = ((Form_pg_operator) GETSTRUCT(optup))->oprcanhash;
1293                 ReleaseSysCache(optup);
1294                 if (!oprcanhash)
1295                         return false;
1296         }
1297         return true;
1298 }
1299
1300 /*---------------
1301  * make_subplanTargetList
1302  *        Generate appropriate target list when grouping is required.
1303  *
1304  * When grouping_planner inserts Aggregate or Group plan nodes above
1305  * the result of query_planner, we typically want to pass a different
1306  * target list to query_planner than the outer plan nodes should have.
1307  * This routine generates the correct target list for the subplan.
1308  *
1309  * The initial target list passed from the parser already contains entries
1310  * for all ORDER BY and GROUP BY expressions, but it will not have entries
1311  * for variables used only in HAVING clauses; so we need to add those
1312  * variables to the subplan target list.  Also, if we are doing either
1313  * grouping or aggregation, we flatten all expressions except GROUP BY items
1314  * into their component variables; the other expressions will be computed by
1315  * the inserted nodes rather than by the subplan.  For example,
1316  * given a query like
1317  *              SELECT a+b,SUM(c+d) FROM table GROUP BY a+b;
1318  * we want to pass this targetlist to the subplan:
1319  *              a,b,c,d,a+b
1320  * where the a+b target will be used by the Sort/Group steps, and the
1321  * other targets will be used for computing the final results.  (In the
1322  * above example we could theoretically suppress the a and b targets and
1323  * pass down only c,d,a+b, but it's not really worth the trouble to
1324  * eliminate simple var references from the subplan.  We will avoid doing
1325  * the extra computation to recompute a+b at the outer level; see
1326  * replace_vars_with_subplan_refs() in setrefs.c.)
1327  *
1328  * If we are grouping or aggregating, *and* there are no non-Var grouping
1329  * expressions, then the returned tlist is effectively dummy; we do not
1330  * need to force it to be evaluated, because all the Vars it contains
1331  * should be present in the output of query_planner anyway.
1332  *
1333  * 'parse' is the query being processed.
1334  * 'tlist' is the query's target list.
1335  * 'groupColIdx' receives an array of column numbers for the GROUP BY
1336  *                      expressions (if there are any) in the subplan's target list.
1337  * 'need_tlist_eval' is set true if we really need to evaluate the
1338  *                      result tlist.
1339  *
1340  * The result is the targetlist to be passed to the subplan.
1341  *---------------
1342  */
1343 static List *
1344 make_subplanTargetList(Query *parse,
1345                                            List *tlist,
1346                                            AttrNumber **groupColIdx,
1347                                            bool *need_tlist_eval)
1348 {
1349         List       *sub_tlist;
1350         List       *extravars;
1351         int                     numCols;
1352
1353         *groupColIdx = NULL;
1354
1355         /*
1356          * If we're not grouping or aggregating, nothing to do here;
1357          * query_planner should receive the unmodified target list.
1358          */
1359         if (!parse->hasAggs && !parse->groupClause && !parse->havingQual)
1360         {
1361                 *need_tlist_eval = true;
1362                 return tlist;
1363         }
1364
1365         /*
1366          * Otherwise, start with a "flattened" tlist (having just the vars
1367          * mentioned in the targetlist and HAVING qual --- but not upper-
1368          * level Vars; they will be replaced by Params later on).
1369          */
1370         sub_tlist = flatten_tlist(tlist);
1371         extravars = pull_var_clause(parse->havingQual, false);
1372         sub_tlist = add_to_flat_tlist(sub_tlist, extravars);
1373         freeList(extravars);
1374         *need_tlist_eval = false;       /* only eval if not flat tlist */
1375
1376         /*
1377          * If grouping, create sub_tlist entries for all GROUP BY expressions
1378          * (GROUP BY items that are simple Vars should be in the list
1379          * already), and make an array showing where the group columns are in
1380          * the sub_tlist.
1381          */
1382         numCols = length(parse->groupClause);
1383         if (numCols > 0)
1384         {
1385                 int                     keyno = 0;
1386                 AttrNumber *grpColIdx;
1387                 List       *gl;
1388
1389                 grpColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
1390                 *groupColIdx = grpColIdx;
1391
1392                 foreach(gl, parse->groupClause)
1393                 {
1394                         GroupClause *grpcl = (GroupClause *) lfirst(gl);
1395                         Node       *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1396                         TargetEntry *te = NULL;
1397                         List       *sl;
1398
1399                         /* Find or make a matching sub_tlist entry */
1400                         foreach(sl, sub_tlist)
1401                         {
1402                                 te = (TargetEntry *) lfirst(sl);
1403                                 if (equal(groupexpr, te->expr))
1404                                         break;
1405                         }
1406                         if (!sl)
1407                         {
1408                                 te = makeTargetEntry(makeResdom(length(sub_tlist) + 1,
1409                                                                                                 exprType(groupexpr),
1410                                                                                                 exprTypmod(groupexpr),
1411                                                                                                 NULL,
1412                                                                                                 false),
1413                                                                          (Expr *) groupexpr);
1414                                 sub_tlist = lappend(sub_tlist, te);
1415                                 *need_tlist_eval = true; /* it's not flat anymore */
1416                         }
1417
1418                         /* and save its resno */
1419                         grpColIdx[keyno++] = te->resdom->resno;
1420                 }
1421         }
1422
1423         return sub_tlist;
1424 }
1425
1426 /*
1427  * locate_grouping_columns
1428  *              Locate grouping columns in the tlist chosen by query_planner.
1429  *
1430  * This is only needed if we don't use the sub_tlist chosen by
1431  * make_subplanTargetList.  We have to forget the column indexes found
1432  * by that routine and re-locate the grouping vars in the real sub_tlist.
1433  */
1434 static void
1435 locate_grouping_columns(Query *parse,
1436                                                 List *tlist,
1437                                                 List *sub_tlist,
1438                                                 AttrNumber *groupColIdx)
1439 {
1440         int                     keyno = 0;
1441         List       *gl;
1442
1443         /*
1444          * No work unless grouping.
1445          */
1446         if (!parse->groupClause)
1447         {
1448                 Assert(groupColIdx == NULL);
1449                 return;
1450         }
1451         Assert(groupColIdx != NULL);
1452
1453         foreach(gl, parse->groupClause)
1454         {
1455                 GroupClause *grpcl = (GroupClause *) lfirst(gl);
1456                 Node       *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
1457                 TargetEntry *te = NULL;
1458                 List       *sl;
1459
1460                 foreach(sl, sub_tlist)
1461                 {
1462                         te = (TargetEntry *) lfirst(sl);
1463                         if (equal(groupexpr, te->expr))
1464                                 break;
1465                 }
1466                 if (!sl)
1467                         elog(ERROR, "locate_grouping_columns: failed");
1468
1469                 groupColIdx[keyno++] = te->resdom->resno;
1470         }
1471 }
1472
1473 /*
1474  * postprocess_setop_tlist
1475  *        Fix up targetlist returned by plan_set_operations().
1476  *
1477  * We need to transpose sort key info from the orig_tlist into new_tlist.
1478  * NOTE: this would not be good enough if we supported resjunk sort keys
1479  * for results of set operations --- then, we'd need to project a whole
1480  * new tlist to evaluate the resjunk columns.  For now, just elog if we
1481  * find any resjunk columns in orig_tlist.
1482  */
1483 static List *
1484 postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
1485 {
1486         List       *l;
1487
1488         foreach(l, new_tlist)
1489         {
1490                 TargetEntry *new_tle = (TargetEntry *) lfirst(l);
1491                 TargetEntry *orig_tle;
1492
1493                 /* ignore resjunk columns in setop result */
1494                 if (new_tle->resdom->resjunk)
1495                         continue;
1496
1497                 Assert(orig_tlist != NIL);
1498                 orig_tle = (TargetEntry *) lfirst(orig_tlist);
1499                 orig_tlist = lnext(orig_tlist);
1500                 if (orig_tle->resdom->resjunk)
1501                         elog(ERROR, "postprocess_setop_tlist: resjunk output columns not implemented");
1502                 Assert(new_tle->resdom->resno == orig_tle->resdom->resno);
1503                 Assert(new_tle->resdom->restype == orig_tle->resdom->restype);
1504                 new_tle->resdom->ressortgroupref = orig_tle->resdom->ressortgroupref;
1505         }
1506         if (orig_tlist != NIL)
1507                 elog(ERROR, "postprocess_setop_tlist: resjunk output columns not implemented");
1508         return new_tlist;
1509 }