granicus.if.org Git - postgresql/blob - src/backend/optimizer/path/allpaths.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * allpaths.c
   4  *        Routines to find possible search paths for processing a query
   5  *
   6  * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/backend/optimizer/path/allpaths.c
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 #include "postgres.h"
  17
  18 #include <math.h>
  19
  20 #include "catalog/pg_class.h"
  21 #include "nodes/nodeFuncs.h"
  22 #ifdef OPTIMIZER_DEBUG
  23 #include "nodes/print.h"
  24 #endif
  25 #include "optimizer/clauses.h"
  26 #include "optimizer/cost.h"
  27 #include "optimizer/geqo.h"
  28 #include "optimizer/pathnode.h"
  29 #include "optimizer/paths.h"
  30 #include "optimizer/plancat.h"
  31 #include "optimizer/planner.h"
  32 #include "optimizer/prep.h"
  33 #include "optimizer/restrictinfo.h"
  34 #include "optimizer/var.h"
  35 #include "parser/parse_clause.h"
  36 #include "parser/parsetree.h"
  37 #include "rewrite/rewriteManip.h"
  38 #include "utils/lsyscache.h"
  39
  40
  41 /* These parameters are set by GUC */
  42 bool            enable_geqo = false;    /* just in case GUC doesn't set it */
  43 int                     geqo_threshold;
  44
  45 /* Hook for plugins to replace standard_join_search() */
  46 join_search_hook_type join_search_hook = NULL;
  47
  48
  49 static void set_base_rel_pathlists(PlannerInfo *root);
  50 static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  51                                  Index rti, RangeTblEntry *rte);
  52 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  53                                            RangeTblEntry *rte);
  54 static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  55                                                 Index rti, RangeTblEntry *rte);
  56 static List *accumulate_append_subpath(List *subpaths, Path *path);
  57 static void set_dummy_rel_pathlist(RelOptInfo *rel);
  58 static void set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
  59                                           Index rti, RangeTblEntry *rte);
  60 static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel,
  61                                           RangeTblEntry *rte);
  62 static void set_values_pathlist(PlannerInfo *root, RelOptInfo *rel,
  63                                         RangeTblEntry *rte);
  64 static void set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel,
  65                                  RangeTblEntry *rte);
  66 static void set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel,
  67                                            RangeTblEntry *rte);
  68 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
  69                                          RangeTblEntry *rte);
  70 static RelOptInfo *make_rel_from_joinlist(PlannerInfo *root, List *joinlist);
  71 static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery,
  72                                                   bool *differentTypes);
  73 static bool recurse_pushdown_safe(Node *setOp, Query *topquery,
  74                                           bool *differentTypes);
  75 static void compare_tlist_datatypes(List *tlist, List *colTypes,
  76                                                 bool *differentTypes);
  77 static bool qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
  78                                           bool *differentTypes);
  79 static void subquery_push_qual(Query *subquery,
  80                                    RangeTblEntry *rte, Index rti, Node *qual);
  81 static void recurse_push_qual(Node *setOp, Query *topquery,
  82                                   RangeTblEntry *rte, Index rti, Node *qual);
  83
  84
  85 /*
  86  * make_one_rel
  87  *        Finds all possible access paths for executing a query, returning a
  88  *        single rel that represents the join of all base rels in the query.
  89  */
  90 RelOptInfo *
  91 make_one_rel(PlannerInfo *root, List *joinlist)
  92 {
  93         RelOptInfo *rel;
  94
  95         /*
  96          * Generate access paths for the base rels.
  97          */
  98         set_base_rel_pathlists(root);
  99
 100         /*
 101          * Generate access paths for the entire join tree.
 102          */
 103         rel = make_rel_from_joinlist(root, joinlist);
 104
 105         /*
 106          * The result should join all and only the query's base rels.
 107          */
 108 #ifdef USE_ASSERT_CHECKING
 109         {
 110                 int                     num_base_rels = 0;
 111                 Index           rti;
 112
 113                 for (rti = 1; rti < root->simple_rel_array_size; rti++)
 114                 {
 115                         RelOptInfo *brel = root->simple_rel_array[rti];
 116
 117                         if (brel == NULL)
 118                                 continue;
 119
 120                         Assert(brel->relid == rti); /* sanity check on array */
 121
 122                         /* ignore RTEs that are "other rels" */
 123                         if (brel->reloptkind != RELOPT_BASEREL)
 124                                 continue;
 125
 126                         Assert(bms_is_member(rti, rel->relids));
 127                         num_base_rels++;
 128                 }
 129
 130                 Assert(bms_num_members(rel->relids) == num_base_rels);
 131         }
 132 #endif
 133
 134         return rel;
 135 }
 136
 137 /*
 138  * set_base_rel_pathlists
 139  *        Finds all paths available for scanning each base-relation entry.
 140  *        Sequential scan and any available indices are considered.
 141  *        Each useful path is attached to its relation's 'pathlist' field.
 142  */
 143 static void
 144 set_base_rel_pathlists(PlannerInfo *root)
 145 {
 146         Index           rti;
 147
 148         for (rti = 1; rti < root->simple_rel_array_size; rti++)
 149         {
 150                 RelOptInfo *rel = root->simple_rel_array[rti];
 151
 152                 /* there may be empty slots corresponding to non-baserel RTEs */
 153                 if (rel == NULL)
 154                         continue;
 155
 156                 Assert(rel->relid == rti);              /* sanity check on array */
 157
 158                 /* ignore RTEs that are "other rels" */
 159                 if (rel->reloptkind != RELOPT_BASEREL)
 160                         continue;
 161
 162                 set_rel_pathlist(root, rel, rti, root->simple_rte_array[rti]);
 163         }
 164 }
 165
 166 /*
 167  * set_rel_pathlist
 168  *        Build access paths for a base relation
 169  */
 170 static void
 171 set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 172                                  Index rti, RangeTblEntry *rte)
 173 {
 174         if (rel->reloptkind == RELOPT_BASEREL &&
 175                 relation_excluded_by_constraints(root, rel, rte))
 176         {
 177                 /*
 178                  * We proved we don't need to scan the rel via constraint exclusion,
 179                  * so set up a single dummy path for it.  Here we only check this for
 180                  * regular baserels; if it's an otherrel, CE was already checked in
 181                  * set_append_rel_pathlist().
 182                  */
 183                 set_dummy_rel_pathlist(rel);
 184         }
 185         else if (rte->inh)
 186         {
 187                 /* It's an "append relation", process accordingly */
 188                 set_append_rel_pathlist(root, rel, rti, rte);
 189         }
 190         else
 191         {
 192                 switch (rel->rtekind)
 193                 {
 194                         case RTE_RELATION:
 195                                 if (rte->relkind == RELKIND_FOREIGN_TABLE)
 196                                 {
 197                                         /* Foreign table */
 198                                         set_foreign_pathlist(root, rel, rte);
 199                                 }
 200                                 else
 201                                 {
 202                                         /* Plain relation */
 203                                         set_plain_rel_pathlist(root, rel, rte);
 204                                 }
 205                                 break;
 206                         case RTE_SUBQUERY:
 207                                 /* Subquery --- generate a separate plan for it */
 208                                 set_subquery_pathlist(root, rel, rti, rte);
 209                                 break;
 210                         case RTE_FUNCTION:
 211                                 /* RangeFunction --- generate a suitable path for it */
 212                                 set_function_pathlist(root, rel, rte);
 213                                 break;
 214                         case RTE_VALUES:
 215                                 /* Values list --- generate a suitable path for it */
 216                                 set_values_pathlist(root, rel, rte);
 217                                 break;
 218                         case RTE_CTE:
 219                                 /* CTE reference --- generate a suitable path for it */
 220                                 if (rte->self_reference)
 221                                         set_worktable_pathlist(root, rel, rte);
 222                                 else
 223                                         set_cte_pathlist(root, rel, rte);
 224                                 break;
 225                         default:
 226                                 elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
 227                                 break;
 228                 }
 229         }
 230
 231 #ifdef OPTIMIZER_DEBUG
 232         debug_print_rel(root, rel);
 233 #endif
 234 }
 235
 236 /*
 237  * set_plain_rel_pathlist
 238  *        Build access paths for a plain relation (no subquery, no inheritance)
 239  */
 240 static void
 241 set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 242 {
 243         /*
 244          * Test any partial indexes of rel for applicability.  We must do this
 245          * first since partial unique indexes can affect size estimates.
 246          */
 247         check_partial_indexes(root, rel);
 248
 249         /* Mark rel with estimated output rows, width, etc */
 250         set_baserel_size_estimates(root, rel);
 251
 252         /*
 253          * Check to see if we can extract any restriction conditions from join
 254          * quals that are OR-of-AND structures.  If so, add them to the rel's
 255          * restriction list, and redo the above steps.
 256          */
 257         if (create_or_index_quals(root, rel))
 258         {
 259                 check_partial_indexes(root, rel);
 260                 set_baserel_size_estimates(root, rel);
 261         }
 262
 263         /*
 264          * Generate paths and add them to the rel's pathlist.
 265          *
 266          * Note: add_path() will discard any paths that are dominated by another
 267          * available path, keeping only those paths that are superior along at
 268          * least one dimension of cost or sortedness.
 269          */
 270
 271         /* Consider sequential scan */
 272         add_path(rel, create_seqscan_path(root, rel));
 273
 274         /* Consider index scans */
 275         create_index_paths(root, rel);
 276
 277         /* Consider TID scans */
 278         create_tidscan_paths(root, rel);
 279
 280         /* Now find the cheapest of the paths for this rel */
 281         set_cheapest(rel);
 282 }
 283
 284 /*
 285  * set_append_rel_pathlist
 286  *        Build access paths for an "append relation"
 287  *
 288  * The passed-in rel and RTE represent the entire append relation.      The
 289  * relation's contents are computed by appending together the output of
 290  * the individual member relations.  Note that in the inheritance case,
 291  * the first member relation is actually the same table as is mentioned in
 292  * the parent RTE ... but it has a different RTE and RelOptInfo.  This is
 293  * a good thing because their outputs are not the same size.
 294  */
 295 static void
 296 set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 297                                                 Index rti, RangeTblEntry *rte)
 298 {
 299         int                     parentRTindex = rti;
 300         List       *live_childrels = NIL;
 301         List       *subpaths = NIL;
 302         List       *all_child_pathkeys = NIL;
 303         double          parent_rows;
 304         double          parent_size;
 305         double     *parent_attrsizes;
 306         int                     nattrs;
 307         ListCell   *l;
 308
 309         /*
 310          * Initialize to compute size estimates for whole append relation.
 311          *
 312          * We handle width estimates by weighting the widths of different child
 313          * rels proportionally to their number of rows.  This is sensible because
 314          * the use of width estimates is mainly to compute the total relation
 315          * "footprint" if we have to sort or hash it.  To do this, we sum the
 316          * total equivalent size (in "double" arithmetic) and then divide by the
 317          * total rowcount estimate.  This is done separately for the total rel
 318          * width and each attribute.
 319          *
 320          * Note: if you consider changing this logic, beware that child rels could
 321          * have zero rows and/or width, if they were excluded by constraints.
 322          */
 323         parent_rows = 0;
 324         parent_size = 0;
 325         nattrs = rel->max_attr - rel->min_attr + 1;
 326         parent_attrsizes = (double *) palloc0(nattrs * sizeof(double));
 327
 328         /*
 329          * Generate access paths for each member relation, and pick the cheapest
 330          * path for each one.
 331          */
 332         foreach(l, root->append_rel_list)
 333         {
 334                 AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
 335                 int                     childRTindex;
 336                 RangeTblEntry *childRTE;
 337                 RelOptInfo *childrel;
 338                 List       *childquals;
 339                 Node       *childqual;
 340                 ListCell   *lcp;
 341                 ListCell   *parentvars;
 342                 ListCell   *childvars;
 343
 344                 /* append_rel_list contains all append rels; ignore others */
 345                 if (appinfo->parent_relid != parentRTindex)
 346                         continue;
 347
 348                 childRTindex = appinfo->child_relid;
 349                 childRTE = root->simple_rte_array[childRTindex];
 350
 351                 /*
 352                  * The child rel's RelOptInfo was already created during
 353                  * add_base_rels_to_query.
 354                  */
 355                 childrel = find_base_rel(root, childRTindex);
 356                 Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
 357
 358                 /*
 359                  * We have to copy the parent's targetlist and quals to the child,
 360                  * with appropriate substitution of variables.  However, only the
 361                  * baserestrictinfo quals are needed before we can check for
 362                  * constraint exclusion; so do that first and then check to see if we
 363                  * can disregard this child.
 364                  *
 365                  * As of 8.4, the child rel's targetlist might contain non-Var
 366                  * expressions, which means that substitution into the quals could
 367                  * produce opportunities for const-simplification, and perhaps even
 368                  * pseudoconstant quals.  To deal with this, we strip the RestrictInfo
 369                  * nodes, do the substitution, do const-simplification, and then
 370                  * reconstitute the RestrictInfo layer.
 371                  */
 372                 childquals = get_all_actual_clauses(rel->baserestrictinfo);
 373                 childquals = (List *) adjust_appendrel_attrs((Node *) childquals,
 374                                                                                                          appinfo);
 375                 childqual = eval_const_expressions(root, (Node *)
 376                                                                                    make_ands_explicit(childquals));
 377                 if (childqual && IsA(childqual, Const) &&
 378                         (((Const *) childqual)->constisnull ||
 379                          !DatumGetBool(((Const *) childqual)->constvalue)))
 380                 {
 381                         /*
 382                          * Restriction reduces to constant FALSE or constant NULL after
 383                          * substitution, so this child need not be scanned.
 384                          */
 385                         set_dummy_rel_pathlist(childrel);
 386                         continue;
 387                 }
 388                 childquals = make_ands_implicit((Expr *) childqual);
 389                 childquals = make_restrictinfos_from_actual_clauses(root,
 390                                                                                                                         childquals);
 391                 childrel->baserestrictinfo = childquals;
 392
 393                 if (relation_excluded_by_constraints(root, childrel, childRTE))
 394                 {
 395                         /*
 396                          * This child need not be scanned, so we can omit it from the
 397                          * appendrel.  Mark it with a dummy cheapest-path though, in case
 398                          * best_appendrel_indexscan() looks at it later.
 399                          */
 400                         set_dummy_rel_pathlist(childrel);
 401                         continue;
 402                 }
 403
 404                 /*
 405                  * CE failed, so finish copying/modifying targetlist and join quals.
 406                  *
 407                  * Note: the resulting childrel->reltargetlist may contain arbitrary
 408                  * expressions, which normally would not occur in a reltargetlist.
 409                  * That is okay because nothing outside of this routine will look at
 410                  * the child rel's reltargetlist.  We do have to cope with the case
 411                  * while constructing attr_widths estimates below, though.
 412                  */
 413                 childrel->joininfo = (List *)
 414                         adjust_appendrel_attrs((Node *) rel->joininfo,
 415                                                                    appinfo);
 416                 childrel->reltargetlist = (List *)
 417                         adjust_appendrel_attrs((Node *) rel->reltargetlist,
 418                                                                    appinfo);
 419
 420                 /*
 421                  * We have to make child entries in the EquivalenceClass data
 422                  * structures as well.  This is needed either if the parent
 423                  * participates in some eclass joins (because we will want to consider
 424                  * inner-indexscan joins on the individual children) or if the parent
 425                  * has useful pathkeys (because we should try to build MergeAppend
 426                  * paths that produce those sort orderings).
 427                  */
 428                 if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
 429                         add_child_rel_equivalences(root, appinfo, rel, childrel);
 430                 childrel->has_eclass_joins = rel->has_eclass_joins;
 431
 432                 /*
 433                  * Note: we could compute appropriate attr_needed data for the child's
 434                  * variables, by transforming the parent's attr_needed through the
 435                  * translated_vars mapping.  However, currently there's no need
 436                  * because attr_needed is only examined for base relations not
 437                  * otherrels.  So we just leave the child's attr_needed empty.
 438                  */
 439
 440                 /*
 441                  * Compute the child's access paths.
 442                  */
 443                 set_rel_pathlist(root, childrel, childRTindex, childRTE);
 444
 445                 /*
 446                  * It is possible that constraint exclusion detected a contradiction
 447                  * within a child subquery, even though we didn't prove one above.
 448                  * If what we got back was a dummy path, we can skip this child.
 449                  */
 450                 if (IS_DUMMY_PATH(childrel->cheapest_total_path))
 451                         continue;
 452
 453                 /*
 454                  * Child is live, so add its cheapest access path to the Append path
 455                  * we are constructing for the parent.
 456                  */
 457                 subpaths = accumulate_append_subpath(subpaths,
 458                                                                                          childrel->cheapest_total_path);
 459
 460                 /* Remember which childrels are live, for MergeAppend logic below */
 461                 live_childrels = lappend(live_childrels, childrel);
 462
 463                 /*
 464                  * Collect a list of all the available path orderings for all the
 465                  * children.  We use this as a heuristic to indicate which sort
 466                  * orderings we should build MergeAppend paths for.
 467                  */
 468                 foreach(lcp, childrel->pathlist)
 469                 {
 470                         Path       *childpath = (Path *) lfirst(lcp);
 471                         List       *childkeys = childpath->pathkeys;
 472                         ListCell   *lpk;
 473                         bool            found = false;
 474
 475                         /* Ignore unsorted paths */
 476                         if (childkeys == NIL)
 477                                 continue;
 478
 479                         /* Have we already seen this ordering? */
 480                         foreach(lpk, all_child_pathkeys)
 481                         {
 482                                 List       *existing_pathkeys = (List *) lfirst(lpk);
 483
 484                                 if (compare_pathkeys(existing_pathkeys,
 485                                                                          childkeys) == PATHKEYS_EQUAL)
 486                                 {
 487                                         found = true;
 488                                         break;
 489                                 }
 490                         }
 491                         if (!found)
 492                         {
 493                                 /* No, so add it to all_child_pathkeys */
 494                                 all_child_pathkeys = lappend(all_child_pathkeys, childkeys);
 495                         }
 496                 }
 497
 498                 /*
 499                  * Accumulate size information from each child.
 500                  */
 501                 if (childrel->rows > 0)
 502                 {
 503                         parent_rows += childrel->rows;
 504                         parent_size += childrel->width * childrel->rows;
 505
 506                         /*
 507                          * Accumulate per-column estimates too.  We need not do anything
 508                          * for PlaceHolderVars in the parent list.  If child expression
 509                          * isn't a Var, or we didn't record a width estimate for it, we
 510                          * have to fall back on a datatype-based estimate.
 511                          *
 512                          * By construction, child's reltargetlist is 1-to-1 with parent's.
 513                          */
 514                         forboth(parentvars, rel->reltargetlist,
 515                                         childvars, childrel->reltargetlist)
 516                         {
 517                                 Var                *parentvar = (Var *) lfirst(parentvars);
 518                                 Node       *childvar = (Node *) lfirst(childvars);
 519
 520                                 if (IsA(parentvar, Var))
 521                                 {
 522                                         int                     pndx = parentvar->varattno - rel->min_attr;
 523                                         int32           child_width = 0;
 524
 525                                         if (IsA(childvar, Var))
 526                                         {
 527                                                 int             cndx = ((Var *) childvar)->varattno - childrel->min_attr;
 528
 529                                                 child_width = childrel->attr_widths[cndx];
 530                                         }
 531                                         if (child_width <= 0)
 532                                                 child_width = get_typavgwidth(exprType(childvar),
 533                                                                                                           exprTypmod(childvar));
 534                                         Assert(child_width > 0);
 535                                         parent_attrsizes[pndx] += child_width * childrel->rows;
 536                                 }
 537                         }
 538                 }
 539         }
 540
 541         /*
 542          * Save the finished size estimates.
 543          */
 544         rel->rows = parent_rows;
 545         if (parent_rows > 0)
 546         {
 547                 int                     i;
 548
 549                 rel->width = rint(parent_size / parent_rows);
 550                 for (i = 0; i < nattrs; i++)
 551                         rel->attr_widths[i] = rint(parent_attrsizes[i] / parent_rows);
 552         }
 553         else
 554                 rel->width = 0;                 /* attr_widths should be zero already */
 555
 556         /*
 557          * Set "raw tuples" count equal to "rows" for the appendrel; needed
 558          * because some places assume rel->tuples is valid for any baserel.
 559          */
 560         rel->tuples = parent_rows;
 561
 562         pfree(parent_attrsizes);
 563
 564         /*
 565          * Next, build an unordered Append path for the rel.  (Note: this is
 566          * correct even if we have zero or one live subpath due to constraint
 567          * exclusion.)
 568          */
 569         add_path(rel, (Path *) create_append_path(rel, subpaths));
 570
 571         /*
 572          * Next, build MergeAppend paths based on the collected list of child
 573          * pathkeys.  We consider both cheapest-startup and cheapest-total cases,
 574          * ie, for each interesting ordering, collect all the cheapest startup
 575          * subpaths and all the cheapest total paths, and build a MergeAppend path
 576          * for each list.
 577          */
 578         foreach(l, all_child_pathkeys)
 579         {
 580                 List       *pathkeys = (List *) lfirst(l);
 581                 List       *startup_subpaths = NIL;
 582                 List       *total_subpaths = NIL;
 583                 bool            startup_neq_total = false;
 584                 ListCell   *lcr;
 585
 586                 /* Select the child paths for this ordering... */
 587                 foreach(lcr, live_childrels)
 588                 {
 589                         RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
 590                         Path       *cheapest_startup,
 591                                            *cheapest_total;
 592
 593                         /* Locate the right paths, if they are available. */
 594                         cheapest_startup =
 595                                 get_cheapest_path_for_pathkeys(childrel->pathlist,
 596                                                                                            pathkeys,
 597                                                                                            STARTUP_COST);
 598                         cheapest_total =
 599                                 get_cheapest_path_for_pathkeys(childrel->pathlist,
 600                                                                                            pathkeys,
 601                                                                                            TOTAL_COST);
 602
 603                         /*
 604                          * If we can't find any paths with the right order just add the
 605                          * cheapest-total path; we'll have to sort it.
 606                          */
 607                         if (cheapest_startup == NULL)
 608                                 cheapest_startup = childrel->cheapest_total_path;
 609                         if (cheapest_total == NULL)
 610                                 cheapest_total = childrel->cheapest_total_path;
 611
 612                         /*
 613                          * Notice whether we actually have different paths for the
 614                          * "cheapest" and "total" cases; frequently there will be no point
 615                          * in two create_merge_append_path() calls.
 616                          */
 617                         if (cheapest_startup != cheapest_total)
 618                                 startup_neq_total = true;
 619
 620                         startup_subpaths =
 621                                 accumulate_append_subpath(startup_subpaths, cheapest_startup);
 622                         total_subpaths =
 623                                 accumulate_append_subpath(total_subpaths, cheapest_total);
 624                 }
 625
 626                 /* ... and build the MergeAppend paths */
 627                 add_path(rel, (Path *) create_merge_append_path(root,
 628                                                                                                                 rel,
 629                                                                                                                 startup_subpaths,
 630                                                                                                                 pathkeys));
 631                 if (startup_neq_total)
 632                         add_path(rel, (Path *) create_merge_append_path(root,
 633                                                                                                                         rel,
 634                                                                                                                         total_subpaths,
 635                                                                                                                         pathkeys));
 636         }
 637
 638         /* Select cheapest path */
 639         set_cheapest(rel);
 640 }
 641
 642 /*
 643  * accumulate_append_subpath
 644  *              Add a subpath to the list being built for an Append or MergeAppend
 645  *
 646  * It's possible that the child is itself an Append path, in which case
 647  * we can "cut out the middleman" and just add its child paths to our
 648  * own list.  (We don't try to do this earlier because we need to
 649  * apply both levels of transformation to the quals.)
 650  */
 651 static List *
 652 accumulate_append_subpath(List *subpaths, Path *path)
 653 {
 654         if (IsA(path, AppendPath))
 655         {
 656                 AppendPath *apath = (AppendPath *) path;
 657
 658                 /* list_copy is important here to avoid sharing list substructure */
 659                 return list_concat(subpaths, list_copy(apath->subpaths));
 660         }
 661         else
 662                 return lappend(subpaths, path);
 663 }
 664
 665 /*
 666  * set_dummy_rel_pathlist
 667  *        Build a dummy path for a relation that's been excluded by constraints
 668  *
 669  * Rather than inventing a special "dummy" path type, we represent this as an
 670  * AppendPath with no members (see also IS_DUMMY_PATH macro).
 671  */
 672 static void
 673 set_dummy_rel_pathlist(RelOptInfo *rel)
 674 {
 675         /* Set dummy size estimates --- we leave attr_widths[] as zeroes */
 676         rel->rows = 0;
 677         rel->width = 0;
 678
 679         add_path(rel, (Path *) create_append_path(rel, NIL));
 680
 681         /* Select cheapest path (pretty easy in this case...) */
 682         set_cheapest(rel);
 683 }
 684
 685 /* quick-and-dirty test to see if any joining is needed */
 686 static bool
 687 has_multiple_baserels(PlannerInfo *root)
 688 {
 689         int                     num_base_rels = 0;
 690         Index           rti;
 691
 692         for (rti = 1; rti < root->simple_rel_array_size; rti++)
 693         {
 694                 RelOptInfo *brel = root->simple_rel_array[rti];
 695
 696                 if (brel == NULL)
 697                         continue;
 698
 699                 /* ignore RTEs that are "other rels" */
 700                 if (brel->reloptkind == RELOPT_BASEREL)
 701                         if (++num_base_rels > 1)
 702                                 return true;
 703         }
 704         return false;
 705 }
 706
 707 /*
 708  * set_subquery_pathlist
 709  *              Build the (single) access path for a subquery RTE
 710  */
 711 static void
 712 set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
 713                                           Index rti, RangeTblEntry *rte)
 714 {
 715         Query      *parse = root->parse;
 716         Query      *subquery = rte->subquery;
 717         bool       *differentTypes;
 718         double          tuple_fraction;
 719         PlannerInfo *subroot;
 720         List       *pathkeys;
 721
 722         /*
 723          * Must copy the Query so that planning doesn't mess up the RTE contents
 724          * (really really need to fix the planner to not scribble on its input,
 725          * someday).
 726          */
 727         subquery = copyObject(subquery);
 728
 729         /* We need a workspace for keeping track of set-op type coercions */
 730         differentTypes = (bool *)
 731                 palloc0((list_length(subquery->targetList) + 1) * sizeof(bool));
 732
 733         /*
 734          * If there are any restriction clauses that have been attached to the
 735          * subquery relation, consider pushing them down to become WHERE or HAVING
 736          * quals of the subquery itself.  This transformation is useful because it
 737          * may allow us to generate a better plan for the subquery than evaluating
 738          * all the subquery output rows and then filtering them.
 739          *
 740          * There are several cases where we cannot push down clauses. Restrictions
 741          * involving the subquery are checked by subquery_is_pushdown_safe().
 742          * Restrictions on individual clauses are checked by
 743          * qual_is_pushdown_safe().  Also, we don't want to push down
 744          * pseudoconstant clauses; better to have the gating node above the
 745          * subquery.
 746          *
 747          * Non-pushed-down clauses will get evaluated as qpquals of the
 748          * SubqueryScan node.
 749          *
 750          * XXX Are there any cases where we want to make a policy decision not to
 751          * push down a pushable qual, because it'd result in a worse plan?
 752          */
 753         if (rel->baserestrictinfo != NIL &&
 754                 subquery_is_pushdown_safe(subquery, subquery, differentTypes))
 755         {
 756                 /* OK to consider pushing down individual quals */
 757                 List       *upperrestrictlist = NIL;
 758                 ListCell   *l;
 759
 760                 foreach(l, rel->baserestrictinfo)
 761                 {
 762                         RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
 763                         Node       *clause = (Node *) rinfo->clause;
 764
 765                         if (!rinfo->pseudoconstant &&
 766                                 qual_is_pushdown_safe(subquery, rti, clause, differentTypes))
 767                         {
 768                                 /* Push it down */
 769                                 subquery_push_qual(subquery, rte, rti, clause);
 770                         }
 771                         else
 772                         {
 773                                 /* Keep it in the upper query */
 774                                 upperrestrictlist = lappend(upperrestrictlist, rinfo);
 775                         }
 776                 }
 777                 rel->baserestrictinfo = upperrestrictlist;
 778         }
 779
 780         pfree(differentTypes);
 781
 782         /*
 783          * We can safely pass the outer tuple_fraction down to the subquery if the
 784          * outer level has no joining, aggregation, or sorting to do. Otherwise
 785          * we'd better tell the subquery to plan for full retrieval. (XXX This
 786          * could probably be made more intelligent ...)
 787          */
 788         if (parse->hasAggs ||
 789                 parse->groupClause ||
 790                 parse->havingQual ||
 791                 parse->distinctClause ||
 792                 parse->sortClause ||
 793                 has_multiple_baserels(root))
 794                 tuple_fraction = 0.0;   /* default case */
 795         else
 796                 tuple_fraction = root->tuple_fraction;
 797
 798         /* Generate the plan for the subquery */
 799         rel->subplan = subquery_planner(root->glob, subquery,
 800                                                                         root,
 801                                                                         false, tuple_fraction,
 802                                                                         &subroot);
 803         rel->subroot = subroot;
 804
 805         /*
 806          * It's possible that constraint exclusion proved the subquery empty.
 807          * If so, it's convenient to turn it back into a dummy path so that we
 808          * will recognize appropriate optimizations at this level.
 809          */
 810         if (is_dummy_plan(rel->subplan))
 811         {
 812                 set_dummy_rel_pathlist(rel);
 813                 return;
 814         }
 815
 816         /* Mark rel with estimated output rows, width, etc */
 817         set_subquery_size_estimates(root, rel);
 818
 819         /* Convert subquery pathkeys to outer representation */
 820         pathkeys = convert_subquery_pathkeys(root, rel, subroot->query_pathkeys);
 821
 822         /* Generate appropriate path */
 823         add_path(rel, create_subqueryscan_path(rel, pathkeys));
 824
 825         /* Select cheapest path (pretty easy in this case...) */
 826         set_cheapest(rel);
 827 }
 828
 829 /*
 830  * set_function_pathlist
 831  *              Build the (single) access path for a function RTE
 832  */
 833 static void
 834 set_function_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 835 {
 836         /* Mark rel with estimated output rows, width, etc */
 837         set_function_size_estimates(root, rel);
 838
 839         /* Generate appropriate path */
 840         add_path(rel, create_functionscan_path(root, rel));
 841
 842         /* Select cheapest path (pretty easy in this case...) */
 843         set_cheapest(rel);
 844 }
 845
 846 /*
 847  * set_values_pathlist
 848  *              Build the (single) access path for a VALUES RTE
 849  */
 850 static void
 851 set_values_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 852 {
 853         /* Mark rel with estimated output rows, width, etc */
 854         set_values_size_estimates(root, rel);
 855
 856         /* Generate appropriate path */
 857         add_path(rel, create_valuesscan_path(root, rel));
 858
 859         /* Select cheapest path (pretty easy in this case...) */
 860         set_cheapest(rel);
 861 }
 862
 863 /*
 864  * set_cte_pathlist
 865  *              Build the (single) access path for a non-self-reference CTE RTE
 866  */
 867 static void
 868 set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 869 {
 870         Plan       *cteplan;
 871         PlannerInfo *cteroot;
 872         Index           levelsup;
 873         int                     ndx;
 874         ListCell   *lc;
 875         int                     plan_id;
 876
 877         /*
 878          * Find the referenced CTE, and locate the plan previously made for it.
 879          */
 880         levelsup = rte->ctelevelsup;
 881         cteroot = root;
 882         while (levelsup-- > 0)
 883         {
 884                 cteroot = cteroot->parent_root;
 885                 if (!cteroot)                   /* shouldn't happen */
 886                         elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
 887         }
 888
 889         /*
 890          * Note: cte_plan_ids can be shorter than cteList, if we are still working
 891          * on planning the CTEs (ie, this is a side-reference from another CTE).
 892          * So we mustn't use forboth here.
 893          */
 894         ndx = 0;
 895         foreach(lc, cteroot->parse->cteList)
 896         {
 897                 CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
 898
 899                 if (strcmp(cte->ctename, rte->ctename) == 0)
 900                         break;
 901                 ndx++;
 902         }
 903         if (lc == NULL)                         /* shouldn't happen */
 904                 elog(ERROR, "could not find CTE \"%s\"", rte->ctename);
 905         if (ndx >= list_length(cteroot->cte_plan_ids))
 906                 elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
 907         plan_id = list_nth_int(cteroot->cte_plan_ids, ndx);
 908         Assert(plan_id > 0);
 909         cteplan = (Plan *) list_nth(root->glob->subplans, plan_id - 1);
 910
 911         /* Mark rel with estimated output rows, width, etc */
 912         set_cte_size_estimates(root, rel, cteplan);
 913
 914         /* Generate appropriate path */
 915         add_path(rel, create_ctescan_path(root, rel));
 916
 917         /* Select cheapest path (pretty easy in this case...) */
 918         set_cheapest(rel);
 919 }
 920
 921 /*
 922  * set_worktable_pathlist
 923  *              Build the (single) access path for a self-reference CTE RTE
 924  */
 925 static void
 926 set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 927 {
 928         Plan       *cteplan;
 929         PlannerInfo *cteroot;
 930         Index           levelsup;
 931
 932         /*
 933          * We need to find the non-recursive term's plan, which is in the plan
 934          * level that's processing the recursive UNION, which is one level *below*
 935          * where the CTE comes from.
 936          */
 937         levelsup = rte->ctelevelsup;
 938         if (levelsup == 0)                      /* shouldn't happen */
 939                 elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
 940         levelsup--;
 941         cteroot = root;
 942         while (levelsup-- > 0)
 943         {
 944                 cteroot = cteroot->parent_root;
 945                 if (!cteroot)                   /* shouldn't happen */
 946                         elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
 947         }
 948         cteplan = cteroot->non_recursive_plan;
 949         if (!cteplan)                           /* shouldn't happen */
 950                 elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
 951
 952         /* Mark rel with estimated output rows, width, etc */
 953         set_cte_size_estimates(root, rel, cteplan);
 954
 955         /* Generate appropriate path */
 956         add_path(rel, create_worktablescan_path(root, rel));
 957
 958         /* Select cheapest path (pretty easy in this case...) */
 959         set_cheapest(rel);
 960 }
 961
 962 /*
 963  * set_foreign_pathlist
 964  *              Build the (single) access path for a foreign table RTE
 965  */
 966 static void
 967 set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 968 {
 969         /* Mark rel with estimated output rows, width, etc */
 970         set_foreign_size_estimates(root, rel);
 971
 972         /* Generate appropriate path */
 973         add_path(rel, (Path *) create_foreignscan_path(root, rel));
 974
 975         /* Select cheapest path (pretty easy in this case...) */
 976         set_cheapest(rel);
 977 }
 978
 979 /*
 980  * make_rel_from_joinlist
 981  *        Build access paths using a "joinlist" to guide the join path search.
 982  *
 983  * See comments for deconstruct_jointree() for definition of the joinlist
 984  * data structure.
 985  */
 986 static RelOptInfo *
 987 make_rel_from_joinlist(PlannerInfo *root, List *joinlist)
 988 {
 989         int                     levels_needed;
 990         List       *initial_rels;
 991         ListCell   *jl;
 992
 993         /*
 994          * Count the number of child joinlist nodes.  This is the depth of the
 995          * dynamic-programming algorithm we must employ to consider all ways of
 996          * joining the child nodes.
 997          */
 998         levels_needed = list_length(joinlist);
 999
1000         if (levels_needed <= 0)
1001                 return NULL;                    /* nothing to do? */
1002
1003         /*
1004          * Construct a list of rels corresponding to the child joinlist nodes.
1005          * This may contain both base rels and rels constructed according to
1006          * sub-joinlists.
1007          */
1008         initial_rels = NIL;
1009         foreach(jl, joinlist)
1010         {
1011                 Node       *jlnode = (Node *) lfirst(jl);
1012                 RelOptInfo *thisrel;
1013
1014                 if (IsA(jlnode, RangeTblRef))
1015                 {
1016                         int                     varno = ((RangeTblRef *) jlnode)->rtindex;
1017
1018                         thisrel = find_base_rel(root, varno);
1019                 }
1020                 else if (IsA(jlnode, List))
1021                 {
1022                         /* Recurse to handle subproblem */
1023                         thisrel = make_rel_from_joinlist(root, (List *) jlnode);
1024                 }
1025                 else
1026                 {
1027                         elog(ERROR, "unrecognized joinlist node type: %d",
1028                                  (int) nodeTag(jlnode));
1029                         thisrel = NULL;         /* keep compiler quiet */
1030                 }
1031
1032                 initial_rels = lappend(initial_rels, thisrel);
1033         }
1034
1035         if (levels_needed == 1)
1036         {
1037                 /*
1038                  * Single joinlist node, so we're done.
1039                  */
1040                 return (RelOptInfo *) linitial(initial_rels);
1041         }
1042         else
1043         {
1044                 /*
1045                  * Consider the different orders in which we could join the rels,
1046                  * using a plugin, GEQO, or the regular join search code.
1047                  *
1048                  * We put the initial_rels list into a PlannerInfo field because
1049                  * has_legal_joinclause() needs to look at it (ugly :-().
1050                  */
1051                 root->initial_rels = initial_rels;
1052
1053                 if (join_search_hook)
1054                         return (*join_search_hook) (root, levels_needed, initial_rels);
1055                 else if (enable_geqo && levels_needed >= geqo_threshold)
1056                         return geqo(root, levels_needed, initial_rels);
1057                 else
1058                         return standard_join_search(root, levels_needed, initial_rels);
1059         }
1060 }
1061
1062 /*
1063  * standard_join_search
1064  *        Find possible joinpaths for a query by successively finding ways
1065  *        to join component relations into join relations.
1066  *
1067  * 'levels_needed' is the number of iterations needed, ie, the number of
1068  *              independent jointree items in the query.  This is > 1.
1069  *
1070  * 'initial_rels' is a list of RelOptInfo nodes for each independent
1071  *              jointree item.  These are the components to be joined together.
1072  *              Note that levels_needed == list_length(initial_rels).
1073  *
1074  * Returns the final level of join relations, i.e., the relation that is
1075  * the result of joining all the original relations together.
1076  * At least one implementation path must be provided for this relation and
1077  * all required sub-relations.
1078  *
1079  * To support loadable plugins that modify planner behavior by changing the
1080  * join searching algorithm, we provide a hook variable that lets a plugin
1081  * replace or supplement this function.  Any such hook must return the same
1082  * final join relation as the standard code would, but it might have a
1083  * different set of implementation paths attached, and only the sub-joinrels
1084  * needed for these paths need have been instantiated.
1085  *
1086  * Note to plugin authors: the functions invoked during standard_join_search()
1087  * modify root->join_rel_list and root->join_rel_hash.  If you want to do more
1088  * than one join-order search, you'll probably need to save and restore the
1089  * original states of those data structures.  See geqo_eval() for an example.
1090  */
1091 RelOptInfo *
1092 standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
1093 {
1094         int                     lev;
1095         RelOptInfo *rel;
1096
1097         /*
1098          * This function cannot be invoked recursively within any one planning
1099          * problem, so join_rel_level[] can't be in use already.
1100          */
1101         Assert(root->join_rel_level == NULL);
1102
1103         /*
1104          * We employ a simple "dynamic programming" algorithm: we first find all
1105          * ways to build joins of two jointree items, then all ways to build joins
1106          * of three items (from two-item joins and single items), then four-item
1107          * joins, and so on until we have considered all ways to join all the
1108          * items into one rel.
1109          *
1110          * root->join_rel_level[j] is a list of all the j-item rels.  Initially we
1111          * set root->join_rel_level[1] to represent all the single-jointree-item
1112          * relations.
1113          */
1114         root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));
1115
1116         root->join_rel_level[1] = initial_rels;
1117
1118         for (lev = 2; lev <= levels_needed; lev++)
1119         {
1120                 ListCell   *lc;
1121
1122                 /*
1123                  * Determine all possible pairs of relations to be joined at this
1124                  * level, and build paths for making each one from every available
1125                  * pair of lower-level relations.
1126                  */
1127                 join_search_one_level(root, lev);
1128
1129                 /*
1130                  * Do cleanup work on each just-processed rel.
1131                  */
1132                 foreach(lc, root->join_rel_level[lev])
1133                 {
1134                         rel = (RelOptInfo *) lfirst(lc);
1135
1136                         /* Find and save the cheapest paths for this rel */
1137                         set_cheapest(rel);
1138
1139 #ifdef OPTIMIZER_DEBUG
1140                         debug_print_rel(root, rel);
1141 #endif
1142                 }
1143         }
1144
1145         /*
1146          * We should have a single rel at the final level.
1147          */
1148         if (root->join_rel_level[levels_needed] == NIL)
1149                 elog(ERROR, "failed to build any %d-way joins", levels_needed);
1150         Assert(list_length(root->join_rel_level[levels_needed]) == 1);
1151
1152         rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);
1153
1154         root->join_rel_level = NULL;
1155
1156         return rel;
1157 }
1158
1159 /*****************************************************************************
1160  *                      PUSHING QUALS DOWN INTO SUBQUERIES
1161  *****************************************************************************/
1162
1163 /*
1164  * subquery_is_pushdown_safe - is a subquery safe for pushing down quals?
1165  *
1166  * subquery is the particular component query being checked.  topquery
1167  * is the top component of a set-operations tree (the same Query if no
1168  * set-op is involved).
1169  *
1170  * Conditions checked here:
1171  *
1172  * 1. If the subquery has a LIMIT clause, we must not push down any quals,
1173  * since that could change the set of rows returned.
1174  *
1175  * 2. If the subquery contains any window functions, we can't push quals
1176  * into it, because that could change the results.
1177  *
1178  * 3. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
1179  * quals into it, because that could change the results.
1180  *
1181  * 4. For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
1182  * push quals into each component query, but the quals can only reference
1183  * subquery columns that suffer no type coercions in the set operation.
1184  * Otherwise there are possible semantic gotchas.  So, we check the
1185  * component queries to see if any of them have different output types;
1186  * differentTypes[k] is set true if column k has different type in any
1187  * component.
1188  */
1189 static bool
1190 subquery_is_pushdown_safe(Query *subquery, Query *topquery,
1191                                                   bool *differentTypes)
1192 {
1193         SetOperationStmt *topop;
1194
1195         /* Check point 1 */
1196         if (subquery->limitOffset != NULL || subquery->limitCount != NULL)
1197                 return false;
1198
1199         /* Check point 2 */
1200         if (subquery->hasWindowFuncs)
1201                 return false;
1202
1203         /* Are we at top level, or looking at a setop component? */
1204         if (subquery == topquery)
1205         {
1206                 /* Top level, so check any component queries */
1207                 if (subquery->setOperations != NULL)
1208                         if (!recurse_pushdown_safe(subquery->setOperations, topquery,
1209                                                                            differentTypes))
1210                                 return false;
1211         }
1212         else
1213         {
1214                 /* Setop component must not have more components (too weird) */
1215                 if (subquery->setOperations != NULL)
1216                         return false;
1217                 /* Check whether setop component output types match top level */
1218                 topop = (SetOperationStmt *) topquery->setOperations;
1219                 Assert(topop && IsA(topop, SetOperationStmt));
1220                 compare_tlist_datatypes(subquery->targetList,
1221                                                                 topop->colTypes,
1222                                                                 differentTypes);
1223         }
1224         return true;
1225 }
1226
1227 /*
1228  * Helper routine to recurse through setOperations tree
1229  */
1230 static bool
1231 recurse_pushdown_safe(Node *setOp, Query *topquery,
1232                                           bool *differentTypes)
1233 {
1234         if (IsA(setOp, RangeTblRef))
1235         {
1236                 RangeTblRef *rtr = (RangeTblRef *) setOp;
1237                 RangeTblEntry *rte = rt_fetch(rtr->rtindex, topquery->rtable);
1238                 Query      *subquery = rte->subquery;
1239
1240                 Assert(subquery != NULL);
1241                 return subquery_is_pushdown_safe(subquery, topquery, differentTypes);
1242         }
1243         else if (IsA(setOp, SetOperationStmt))
1244         {
1245                 SetOperationStmt *op = (SetOperationStmt *) setOp;
1246
1247                 /* EXCEPT is no good */
1248                 if (op->op == SETOP_EXCEPT)
1249                         return false;
1250                 /* Else recurse */
1251                 if (!recurse_pushdown_safe(op->larg, topquery, differentTypes))
1252                         return false;
1253                 if (!recurse_pushdown_safe(op->rarg, topquery, differentTypes))
1254                         return false;
1255         }
1256         else
1257         {
1258                 elog(ERROR, "unrecognized node type: %d",
1259                          (int) nodeTag(setOp));
1260         }
1261         return true;
1262 }
1263
1264 /*
1265  * Compare tlist's datatypes against the list of set-operation result types.
1266  * For any items that are different, mark the appropriate element of
1267  * differentTypes[] to show that this column will have type conversions.
1268  *
1269  * We don't have to care about typmods here: the only allowed difference
1270  * between set-op input and output typmods is input is a specific typmod
1271  * and output is -1, and that does not require a coercion.
1272  */
1273 static void
1274 compare_tlist_datatypes(List *tlist, List *colTypes,
1275                                                 bool *differentTypes)
1276 {
1277         ListCell   *l;
1278         ListCell   *colType = list_head(colTypes);
1279
1280         foreach(l, tlist)
1281         {
1282                 TargetEntry *tle = (TargetEntry *) lfirst(l);
1283
1284                 if (tle->resjunk)
1285                         continue;                       /* ignore resjunk columns */
1286                 if (colType == NULL)
1287                         elog(ERROR, "wrong number of tlist entries");
1288                 if (exprType((Node *) tle->expr) != lfirst_oid(colType))
1289                         differentTypes[tle->resno] = true;
1290                 colType = lnext(colType);
1291         }
1292         if (colType != NULL)
1293                 elog(ERROR, "wrong number of tlist entries");
1294 }
1295
1296 /*
1297  * qual_is_pushdown_safe - is a particular qual safe to push down?
1298  *
1299  * qual is a restriction clause applying to the given subquery (whose RTE
1300  * has index rti in the parent query).
1301  *
1302  * Conditions checked here:
1303  *
1304  * 1. The qual must not contain any subselects (mainly because I'm not sure
1305  * it will work correctly: sublinks will already have been transformed into
1306  * subplans in the qual, but not in the subquery).
1307  *
1308  * 2. The qual must not refer to the whole-row output of the subquery
1309  * (since there is no easy way to name that within the subquery itself).
1310  *
1311  * 3. The qual must not refer to any subquery output columns that were
1312  * found to have inconsistent types across a set operation tree by
1313  * subquery_is_pushdown_safe().
1314  *
1315  * 4. If the subquery uses DISTINCT ON, we must not push down any quals that
1316  * refer to non-DISTINCT output columns, because that could change the set
1317  * of rows returned.  (This condition is vacuous for DISTINCT, because then
1318  * there are no non-DISTINCT output columns, so we needn't check.  But note
1319  * we are assuming that the qual can't distinguish values that the DISTINCT
1320  * operator sees as equal.      This is a bit shaky but we have no way to test
1321  * for the case, and it's unlikely enough that we shouldn't refuse the
1322  * optimization just because it could theoretically happen.)
1323  *
1324  * 5. We must not push down any quals that refer to subselect outputs that
1325  * return sets, else we'd introduce functions-returning-sets into the
1326  * subquery's WHERE/HAVING quals.
1327  *
1328  * 6. We must not push down any quals that refer to subselect outputs that
1329  * contain volatile functions, for fear of introducing strange results due
1330  * to multiple evaluation of a volatile function.
1331  */
1332 static bool
1333 qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
1334                                           bool *differentTypes)
1335 {
1336         bool            safe = true;
1337         List       *vars;
1338         ListCell   *vl;
1339         Bitmapset  *tested = NULL;
1340
1341         /* Refuse subselects (point 1) */
1342         if (contain_subplans(qual))
1343                 return false;
1344
1345         /*
1346          * It would be unsafe to push down window function calls, but at least for
1347          * the moment we could never see any in a qual anyhow.  (The same applies
1348          * to aggregates, which we check for in pull_var_clause below.)
1349          */
1350         Assert(!contain_window_function(qual));
1351
1352         /*
1353          * Examine all Vars used in clause; since it's a restriction clause, all
1354          * such Vars must refer to subselect output columns.
1355          */
1356         vars = pull_var_clause(qual,
1357                                                    PVC_REJECT_AGGREGATES,
1358                                                    PVC_INCLUDE_PLACEHOLDERS);
1359         foreach(vl, vars)
1360         {
1361                 Var                *var = (Var *) lfirst(vl);
1362                 TargetEntry *tle;
1363
1364                 /*
1365                  * XXX Punt if we find any PlaceHolderVars in the restriction clause.
1366                  * It's not clear whether a PHV could safely be pushed down, and even
1367                  * less clear whether such a situation could arise in any cases of
1368                  * practical interest anyway.  So for the moment, just refuse to push
1369                  * down.
1370                  */
1371                 if (!IsA(var, Var))
1372                 {
1373                         safe = false;
1374                         break;
1375                 }
1376
1377                 Assert(var->varno == rti);
1378
1379                 /* Check point 2 */
1380                 if (var->varattno == 0)
1381                 {
1382                         safe = false;
1383                         break;
1384                 }
1385
1386                 /*
1387                  * We use a bitmapset to avoid testing the same attno more than once.
1388                  * (NB: this only works because subquery outputs can't have negative
1389                  * attnos.)
1390                  */
1391                 if (bms_is_member(var->varattno, tested))
1392                         continue;
1393                 tested = bms_add_member(tested, var->varattno);
1394
1395                 /* Check point 3 */
1396                 if (differentTypes[var->varattno])
1397                 {
1398                         safe = false;
1399                         break;
1400                 }
1401
1402                 /* Must find the tlist element referenced by the Var */
1403                 tle = get_tle_by_resno(subquery->targetList, var->varattno);
1404                 Assert(tle != NULL);
1405                 Assert(!tle->resjunk);
1406
1407                 /* If subquery uses DISTINCT ON, check point 4 */
1408                 if (subquery->hasDistinctOn &&
1409                         !targetIsInSortList(tle, InvalidOid, subquery->distinctClause))
1410                 {
1411                         /* non-DISTINCT column, so fail */
1412                         safe = false;
1413                         break;
1414                 }
1415
1416                 /* Refuse functions returning sets (point 5) */
1417                 if (expression_returns_set((Node *) tle->expr))
1418                 {
1419                         safe = false;
1420                         break;
1421                 }
1422
1423                 /* Refuse volatile functions (point 6) */
1424                 if (contain_volatile_functions((Node *) tle->expr))
1425                 {
1426                         safe = false;
1427                         break;
1428                 }
1429         }
1430
1431         list_free(vars);
1432         bms_free(tested);
1433
1434         return safe;
1435 }
1436
1437 /*
1438  * subquery_push_qual - push down a qual that we have determined is safe
1439  */
1440 static void
1441 subquery_push_qual(Query *subquery, RangeTblEntry *rte, Index rti, Node *qual)
1442 {
1443         if (subquery->setOperations != NULL)
1444         {
1445                 /* Recurse to push it separately to each component query */
1446                 recurse_push_qual(subquery->setOperations, subquery,
1447                                                   rte, rti, qual);
1448         }
1449         else
1450         {
1451                 /*
1452                  * We need to replace Vars in the qual (which must refer to outputs of
1453                  * the subquery) with copies of the subquery's targetlist expressions.
1454                  * Note that at this point, any uplevel Vars in the qual should have
1455                  * been replaced with Params, so they need no work.
1456                  *
1457                  * This step also ensures that when we are pushing into a setop tree,
1458                  * each component query gets its own copy of the qual.
1459                  */
1460                 qual = ResolveNew(qual, rti, 0, rte,
1461                                                   subquery->targetList,
1462                                                   CMD_SELECT, 0,
1463                                                   &subquery->hasSubLinks);
1464
1465                 /*
1466                  * Now attach the qual to the proper place: normally WHERE, but if the
1467                  * subquery uses grouping or aggregation, put it in HAVING (since the
1468                  * qual really refers to the group-result rows).
1469                  */
1470                 if (subquery->hasAggs || subquery->groupClause || subquery->havingQual)
1471                         subquery->havingQual = make_and_qual(subquery->havingQual, qual);
1472                 else
1473                         subquery->jointree->quals =
1474                                 make_and_qual(subquery->jointree->quals, qual);
1475
1476                 /*
1477                  * We need not change the subquery's hasAggs or hasSublinks flags,
1478                  * since we can't be pushing down any aggregates that weren't there
1479                  * before, and we don't push down subselects at all.
1480                  */
1481         }
1482 }
1483
1484 /*
1485  * Helper routine to recurse through setOperations tree
1486  */
1487 static void
1488 recurse_push_qual(Node *setOp, Query *topquery,
1489                                   RangeTblEntry *rte, Index rti, Node *qual)
1490 {
1491         if (IsA(setOp, RangeTblRef))
1492         {
1493                 RangeTblRef *rtr = (RangeTblRef *) setOp;
1494                 RangeTblEntry *subrte = rt_fetch(rtr->rtindex, topquery->rtable);
1495                 Query      *subquery = subrte->subquery;
1496
1497                 Assert(subquery != NULL);
1498                 subquery_push_qual(subquery, rte, rti, qual);
1499         }
1500         else if (IsA(setOp, SetOperationStmt))
1501         {
1502                 SetOperationStmt *op = (SetOperationStmt *) setOp;
1503
1504                 recurse_push_qual(op->larg, topquery, rte, rti, qual);
1505                 recurse_push_qual(op->rarg, topquery, rte, rti, qual);
1506         }
1507         else
1508         {
1509                 elog(ERROR, "unrecognized node type: %d",
1510                          (int) nodeTag(setOp));
1511         }
1512 }
1513
1514 /*****************************************************************************
1515  *                      DEBUG SUPPORT
1516  *****************************************************************************/
1517
1518 #ifdef OPTIMIZER_DEBUG
1519
1520 static void
1521 print_relids(Relids relids)
1522 {
1523         Relids          tmprelids;
1524         int                     x;
1525         bool            first = true;
1526
1527         tmprelids = bms_copy(relids);
1528         while ((x = bms_first_member(tmprelids)) >= 0)
1529         {
1530                 if (!first)
1531                         printf(" ");
1532                 printf("%d", x);
1533                 first = false;
1534         }
1535         bms_free(tmprelids);
1536 }
1537
1538 static void
1539 print_restrictclauses(PlannerInfo *root, List *clauses)
1540 {
1541         ListCell   *l;
1542
1543         foreach(l, clauses)
1544         {
1545                 RestrictInfo *c = lfirst(l);
1546
1547                 print_expr((Node *) c->clause, root->parse->rtable);
1548                 if (lnext(l))
1549                         printf(", ");
1550         }
1551 }
1552
1553 static void
1554 print_path(PlannerInfo *root, Path *path, int indent)
1555 {
1556         const char *ptype;
1557         bool            join = false;
1558         Path       *subpath = NULL;
1559         int                     i;
1560
1561         switch (nodeTag(path))
1562         {
1563                 case T_Path:
1564                         ptype = "SeqScan";
1565                         break;
1566                 case T_IndexPath:
1567                         ptype = "IdxScan";
1568                         break;
1569                 case T_BitmapHeapPath:
1570                         ptype = "BitmapHeapScan";
1571                         break;
1572                 case T_BitmapAndPath:
1573                         ptype = "BitmapAndPath";
1574                         break;
1575                 case T_BitmapOrPath:
1576                         ptype = "BitmapOrPath";
1577                         break;
1578                 case T_TidPath:
1579                         ptype = "TidScan";
1580                         break;
1581                 case T_ForeignPath:
1582                         ptype = "ForeignScan";
1583                         break;
1584                 case T_AppendPath:
1585                         ptype = "Append";
1586                         break;
1587                 case T_MergeAppendPath:
1588                         ptype = "MergeAppend";
1589                         break;
1590                 case T_ResultPath:
1591                         ptype = "Result";
1592                         break;
1593                 case T_MaterialPath:
1594                         ptype = "Material";
1595                         subpath = ((MaterialPath *) path)->subpath;
1596                         break;
1597                 case T_UniquePath:
1598                         ptype = "Unique";
1599                         subpath = ((UniquePath *) path)->subpath;
1600                         break;
1601                 case T_NestPath:
1602                         ptype = "NestLoop";
1603                         join = true;
1604                         break;
1605                 case T_MergePath:
1606                         ptype = "MergeJoin";
1607                         join = true;
1608                         break;
1609                 case T_HashPath:
1610                         ptype = "HashJoin";
1611                         join = true;
1612                         break;
1613                 default:
1614                         ptype = "???Path";
1615                         break;
1616         }
1617
1618         for (i = 0; i < indent; i++)
1619                 printf("\t");
1620         printf("%s", ptype);
1621
1622         if (path->parent)
1623         {
1624                 printf("(");
1625                 print_relids(path->parent->relids);
1626                 printf(") rows=%.0f", path->parent->rows);
1627         }
1628         printf(" cost=%.2f..%.2f\n", path->startup_cost, path->total_cost);
1629
1630         if (path->pathkeys)
1631         {
1632                 for (i = 0; i < indent; i++)
1633                         printf("\t");
1634                 printf("  pathkeys: ");
1635                 print_pathkeys(path->pathkeys, root->parse->rtable);
1636         }
1637
1638         if (join)
1639         {
1640                 JoinPath   *jp = (JoinPath *) path;
1641
1642                 for (i = 0; i < indent; i++)
1643                         printf("\t");
1644                 printf("  clauses: ");
1645                 print_restrictclauses(root, jp->joinrestrictinfo);
1646                 printf("\n");
1647
1648                 if (IsA(path, MergePath))
1649                 {
1650                         MergePath  *mp = (MergePath *) path;
1651
1652                         for (i = 0; i < indent; i++)
1653                                 printf("\t");
1654                         printf("  sortouter=%d sortinner=%d materializeinner=%d\n",
1655                                    ((mp->outersortkeys) ? 1 : 0),
1656                                    ((mp->innersortkeys) ? 1 : 0),
1657                                    ((mp->materialize_inner) ? 1 : 0));
1658                 }
1659
1660                 print_path(root, jp->outerjoinpath, indent + 1);
1661                 print_path(root, jp->innerjoinpath, indent + 1);
1662         }
1663
1664         if (subpath)
1665                 print_path(root, subpath, indent + 1);
1666 }
1667
1668 void
1669 debug_print_rel(PlannerInfo *root, RelOptInfo *rel)
1670 {
1671         ListCell   *l;
1672
1673         printf("RELOPTINFO (");
1674         print_relids(rel->relids);
1675         printf("): rows=%.0f width=%d\n", rel->rows, rel->width);
1676
1677         if (rel->baserestrictinfo)
1678         {
1679                 printf("\tbaserestrictinfo: ");
1680                 print_restrictclauses(root, rel->baserestrictinfo);
1681                 printf("\n");
1682         }
1683
1684         if (rel->joininfo)
1685         {
1686                 printf("\tjoininfo: ");
1687                 print_restrictclauses(root, rel->joininfo);
1688                 printf("\n");
1689         }
1690
1691         printf("\tpath list:\n");
1692         foreach(l, rel->pathlist)
1693                 print_path(root, lfirst(l), 1);
1694         printf("\n\tcheapest startup path:\n");
1695         print_path(root, rel->cheapest_startup_path, 1);
1696         printf("\n\tcheapest total path:\n");
1697         print_path(root, rel->cheapest_total_path, 1);
1698         printf("\n");
1699         fflush(stdout);
1700 }
1701
1702 #endif   /* OPTIMIZER_DEBUG */