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) 1996-2012, 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 "foreign/fdwapi.h"
  22 #include "nodes/nodeFuncs.h"
  23 #ifdef OPTIMIZER_DEBUG
  24 #include "nodes/print.h"
  25 #endif
  26 #include "optimizer/clauses.h"
  27 #include "optimizer/cost.h"
  28 #include "optimizer/geqo.h"
  29 #include "optimizer/pathnode.h"
  30 #include "optimizer/paths.h"
  31 #include "optimizer/plancat.h"
  32 #include "optimizer/planner.h"
  33 #include "optimizer/prep.h"
  34 #include "optimizer/restrictinfo.h"
  35 #include "optimizer/var.h"
  36 #include "parser/parse_clause.h"
  37 #include "parser/parsetree.h"
  38 #include "rewrite/rewriteManip.h"
  39 #include "utils/lsyscache.h"
  40
  41
  42 /* These parameters are set by GUC */
  43 bool            enable_geqo = false;    /* just in case GUC doesn't set it */
  44 int                     geqo_threshold;
  45
  46 /* Hook for plugins to replace standard_join_search() */
  47 join_search_hook_type join_search_hook = NULL;
  48
  49
  50 static void set_base_rel_sizes(PlannerInfo *root);
  51 static void set_base_rel_pathlists(PlannerInfo *root);
  52 static void set_rel_size(PlannerInfo *root, RelOptInfo *rel,
  53                                  Index rti, RangeTblEntry *rte);
  54 static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  55                                  Index rti, RangeTblEntry *rte);
  56 static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
  57                                            RangeTblEntry *rte);
  58 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  59                                            RangeTblEntry *rte);
  60 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
  61                                          RangeTblEntry *rte);
  62 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
  63                                          RangeTblEntry *rte);
  64 static void set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
  65                                                 Index rti, RangeTblEntry *rte);
  66 static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  67                                                 Index rti, RangeTblEntry *rte);
  68 static void generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
  69                                                    List *live_childrels,
  70                                                    List *all_child_pathkeys);
  71 static List *accumulate_append_subpath(List *subpaths, Path *path);
  72 static void set_dummy_rel_pathlist(RelOptInfo *rel);
  73 static void set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
  74                                           Index rti, RangeTblEntry *rte);
  75 static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel,
  76                                           RangeTblEntry *rte);
  77 static void set_values_pathlist(PlannerInfo *root, RelOptInfo *rel,
  78                                         RangeTblEntry *rte);
  79 static void set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel,
  80                                  RangeTblEntry *rte);
  81 static void set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel,
  82                                            RangeTblEntry *rte);
  83 static RelOptInfo *make_rel_from_joinlist(PlannerInfo *root, List *joinlist);
  84 static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery,
  85                                                   bool *differentTypes);
  86 static bool recurse_pushdown_safe(Node *setOp, Query *topquery,
  87                                           bool *differentTypes);
  88 static void compare_tlist_datatypes(List *tlist, List *colTypes,
  89                                                 bool *differentTypes);
  90 static bool qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
  91                                           bool *differentTypes);
  92 static void subquery_push_qual(Query *subquery,
  93                                    RangeTblEntry *rte, Index rti, Node *qual);
  94 static void recurse_push_qual(Node *setOp, Query *topquery,
  95                                   RangeTblEntry *rte, Index rti, Node *qual);
  96
  97
  98 /*
  99  * make_one_rel
 100  *        Finds all possible access paths for executing a query, returning a
 101  *        single rel that represents the join of all base rels in the query.
 102  */
 103 RelOptInfo *
 104 make_one_rel(PlannerInfo *root, List *joinlist)
 105 {
 106         RelOptInfo *rel;
 107         Index           rti;
 108
 109         /*
 110          * Construct the all_baserels Relids set.
 111          */
 112         root->all_baserels = NULL;
 113         for (rti = 1; rti < root->simple_rel_array_size; rti++)
 114         {
 115                 RelOptInfo *brel = root->simple_rel_array[rti];
 116
 117                 /* there may be empty slots corresponding to non-baserel RTEs */
 118                 if (brel == NULL)
 119                         continue;
 120
 121                 Assert(brel->relid == rti); /* sanity check on array */
 122
 123                 /* ignore RTEs that are "other rels" */
 124                 if (brel->reloptkind != RELOPT_BASEREL)
 125                         continue;
 126
 127                 root->all_baserels = bms_add_member(root->all_baserels, brel->relid);
 128         }
 129
 130         /*
 131          * Generate access paths for the base rels.
 132          */
 133         set_base_rel_sizes(root);
 134         set_base_rel_pathlists(root);
 135
 136         /*
 137          * Generate access paths for the entire join tree.
 138          */
 139         rel = make_rel_from_joinlist(root, joinlist);
 140
 141         /*
 142          * The result should join all and only the query's base rels.
 143          */
 144         Assert(bms_equal(rel->relids, root->all_baserels));
 145
 146         return rel;
 147 }
 148
 149 /*
 150  * set_base_rel_sizes
 151  *        Set the size estimates (rows and widths) for each base-relation entry.
 152  *
 153  * We do this in a separate pass over the base rels so that rowcount
 154  * estimates are available for parameterized path generation.
 155  */
 156 static void
 157 set_base_rel_sizes(PlannerInfo *root)
 158 {
 159         Index           rti;
 160
 161         for (rti = 1; rti < root->simple_rel_array_size; rti++)
 162         {
 163                 RelOptInfo *rel = root->simple_rel_array[rti];
 164
 165                 /* there may be empty slots corresponding to non-baserel RTEs */
 166                 if (rel == NULL)
 167                         continue;
 168
 169                 Assert(rel->relid == rti);              /* sanity check on array */
 170
 171                 /* ignore RTEs that are "other rels" */
 172                 if (rel->reloptkind != RELOPT_BASEREL)
 173                         continue;
 174
 175                 set_rel_size(root, rel, rti, root->simple_rte_array[rti]);
 176         }
 177 }
 178
 179 /*
 180  * set_base_rel_pathlists
 181  *        Finds all paths available for scanning each base-relation entry.
 182  *        Sequential scan and any available indices are considered.
 183  *        Each useful path is attached to its relation's 'pathlist' field.
 184  */
 185 static void
 186 set_base_rel_pathlists(PlannerInfo *root)
 187 {
 188         Index           rti;
 189
 190         for (rti = 1; rti < root->simple_rel_array_size; rti++)
 191         {
 192                 RelOptInfo *rel = root->simple_rel_array[rti];
 193
 194                 /* there may be empty slots corresponding to non-baserel RTEs */
 195                 if (rel == NULL)
 196                         continue;
 197
 198                 Assert(rel->relid == rti);              /* sanity check on array */
 199
 200                 /* ignore RTEs that are "other rels" */
 201                 if (rel->reloptkind != RELOPT_BASEREL)
 202                         continue;
 203
 204                 set_rel_pathlist(root, rel, rti, root->simple_rte_array[rti]);
 205         }
 206 }
 207
 208 /*
 209  * set_rel_size
 210  *        Set size estimates for a base relation
 211  */
 212 static void
 213 set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 214                                  Index rti, RangeTblEntry *rte)
 215 {
 216         if (rel->reloptkind == RELOPT_BASEREL &&
 217                 relation_excluded_by_constraints(root, rel, rte))
 218         {
 219                 /*
 220                  * We proved we don't need to scan the rel via constraint exclusion,
 221                  * so set up a single dummy path for it.  Here we only check this for
 222                  * regular baserels; if it's an otherrel, CE was already checked in
 223                  * set_append_rel_pathlist().
 224                  *
 225                  * In this case, we go ahead and set up the relation's path right away
 226                  * instead of leaving it for set_rel_pathlist to do.  This is because
 227                  * we don't have a convention for marking a rel as dummy except by
 228                  * assigning a dummy path to it.
 229                  */
 230                 set_dummy_rel_pathlist(rel);
 231         }
 232         else if (rte->inh)
 233         {
 234                 /* It's an "append relation", process accordingly */
 235                 set_append_rel_size(root, rel, rti, rte);
 236         }
 237         else
 238         {
 239                 switch (rel->rtekind)
 240                 {
 241                         case RTE_RELATION:
 242                                 if (rte->relkind == RELKIND_FOREIGN_TABLE)
 243                                 {
 244                                         /* Foreign table */
 245                                         set_foreign_size(root, rel, rte);
 246                                 }
 247                                 else
 248                                 {
 249                                         /* Plain relation */
 250                                         set_plain_rel_size(root, rel, rte);
 251                                 }
 252                                 break;
 253                         case RTE_SUBQUERY:
 254                                 /*
 255                                  * Subqueries don't support parameterized paths, so just go
 256                                  * ahead and build their paths immediately.
 257                                  */
 258                                 set_subquery_pathlist(root, rel, rti, rte);
 259                                 break;
 260                         case RTE_FUNCTION:
 261                                 set_function_size_estimates(root, rel);
 262                                 break;
 263                         case RTE_VALUES:
 264                                 set_values_size_estimates(root, rel);
 265                                 break;
 266                         case RTE_CTE:
 267                                 /*
 268                                  * CTEs don't support parameterized paths, so just go ahead
 269                                  * and build their paths immediately.
 270                                  */
 271                                 if (rte->self_reference)
 272                                         set_worktable_pathlist(root, rel, rte);
 273                                 else
 274                                         set_cte_pathlist(root, rel, rte);
 275                                 break;
 276                         default:
 277                                 elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
 278                                 break;
 279                 }
 280         }
 281 }
 282
 283 /*
 284  * set_rel_pathlist
 285  *        Build access paths for a base relation
 286  */
 287 static void
 288 set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 289                                  Index rti, RangeTblEntry *rte)
 290 {
 291         if (IS_DUMMY_REL(rel))
 292         {
 293                 /* We already proved the relation empty, so nothing more to do */
 294         }
 295         else if (rte->inh)
 296         {
 297                 /* It's an "append relation", process accordingly */
 298                 set_append_rel_pathlist(root, rel, rti, rte);
 299         }
 300         else
 301         {
 302                 switch (rel->rtekind)
 303                 {
 304                         case RTE_RELATION:
 305                                 if (rte->relkind == RELKIND_FOREIGN_TABLE)
 306                                 {
 307                                         /* Foreign table */
 308                                         set_foreign_pathlist(root, rel, rte);
 309                                 }
 310                                 else
 311                                 {
 312                                         /* Plain relation */
 313                                         set_plain_rel_pathlist(root, rel, rte);
 314                                 }
 315                                 break;
 316                         case RTE_SUBQUERY:
 317                                 /* Subquery --- fully handled during set_rel_size */
 318                                 break;
 319                         case RTE_FUNCTION:
 320                                 /* RangeFunction */
 321                                 set_function_pathlist(root, rel, rte);
 322                                 break;
 323                         case RTE_VALUES:
 324                                 /* Values list */
 325                                 set_values_pathlist(root, rel, rte);
 326                                 break;
 327                         case RTE_CTE:
 328                                 /* CTE reference --- fully handled during set_rel_size */
 329                                 break;
 330                         default:
 331                                 elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
 332                                 break;
 333                 }
 334         }
 335
 336 #ifdef OPTIMIZER_DEBUG
 337         debug_print_rel(root, rel);
 338 #endif
 339 }
 340
 341 /*
 342  * set_plain_rel_size
 343  *        Set size estimates for a plain relation (no subquery, no inheritance)
 344  */
 345 static void
 346 set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 347 {
 348         /*
 349          * Test any partial indexes of rel for applicability.  We must do this
 350          * first since partial unique indexes can affect size estimates.
 351          */
 352         check_partial_indexes(root, rel);
 353
 354         /* Mark rel with estimated output rows, width, etc */
 355         set_baserel_size_estimates(root, rel);
 356
 357         /*
 358          * Check to see if we can extract any restriction conditions from join
 359          * quals that are OR-of-AND structures.  If so, add them to the rel's
 360          * restriction list, and redo the above steps.
 361          */
 362         if (create_or_index_quals(root, rel))
 363         {
 364                 check_partial_indexes(root, rel);
 365                 set_baserel_size_estimates(root, rel);
 366         }
 367 }
 368
 369 /*
 370  * set_plain_rel_pathlist
 371  *        Build access paths for a plain relation (no subquery, no inheritance)
 372  */
 373 static void
 374 set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 375 {
 376         /* Consider sequential scan */
 377         add_path(rel, create_seqscan_path(root, rel, NULL));
 378
 379         /* Consider index scans */
 380         create_index_paths(root, rel);
 381
 382         /* Consider TID scans */
 383         create_tidscan_paths(root, rel);
 384
 385         /* Now find the cheapest of the paths for this rel */
 386         set_cheapest(rel);
 387 }
 388
 389 /*
 390  * set_foreign_size
 391  *              Set size estimates for a foreign table RTE
 392  */
 393 static void
 394 set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 395 {
 396         /* Mark rel with estimated output rows, width, etc */
 397         set_foreign_size_estimates(root, rel);
 398
 399         /* Get FDW routine pointers for the rel */
 400         rel->fdwroutine = GetFdwRoutineByRelId(rte->relid);
 401
 402         /* Let FDW adjust the size estimates, if it can */
 403         rel->fdwroutine->GetForeignRelSize(root, rel, rte->relid);
 404 }
 405
 406 /*
 407  * set_foreign_pathlist
 408  *              Build access paths for a foreign table RTE
 409  */
 410 static void
 411 set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 412 {
 413         /* Call the FDW's GetForeignPaths function to generate path(s) */
 414         rel->fdwroutine->GetForeignPaths(root, rel, rte->relid);
 415
 416         /* Select cheapest path */
 417         set_cheapest(rel);
 418 }
 419
 420 /*
 421  * set_append_rel_size
 422  *        Set size estimates for an "append relation"
 423  *
 424  * The passed-in rel and RTE represent the entire append relation.      The
 425  * relation's contents are computed by appending together the output of
 426  * the individual member relations.  Note that in the inheritance case,
 427  * the first member relation is actually the same table as is mentioned in
 428  * the parent RTE ... but it has a different RTE and RelOptInfo.  This is
 429  * a good thing because their outputs are not the same size.
 430  */
 431 static void
 432 set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
 433                                         Index rti, RangeTblEntry *rte)
 434 {
 435         int                     parentRTindex = rti;
 436         double          parent_rows;
 437         double          parent_size;
 438         double     *parent_attrsizes;
 439         int                     nattrs;
 440         ListCell   *l;
 441
 442         /*
 443          * Initialize to compute size estimates for whole append relation.
 444          *
 445          * We handle width estimates by weighting the widths of different child
 446          * rels proportionally to their number of rows.  This is sensible because
 447          * the use of width estimates is mainly to compute the total relation
 448          * "footprint" if we have to sort or hash it.  To do this, we sum the
 449          * total equivalent size (in "double" arithmetic) and then divide by the
 450          * total rowcount estimate.  This is done separately for the total rel
 451          * width and each attribute.
 452          *
 453          * Note: if you consider changing this logic, beware that child rels could
 454          * have zero rows and/or width, if they were excluded by constraints.
 455          */
 456         parent_rows = 0;
 457         parent_size = 0;
 458         nattrs = rel->max_attr - rel->min_attr + 1;
 459         parent_attrsizes = (double *) palloc0(nattrs * sizeof(double));
 460
 461         foreach(l, root->append_rel_list)
 462         {
 463                 AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
 464                 int                     childRTindex;
 465                 RangeTblEntry *childRTE;
 466                 RelOptInfo *childrel;
 467                 List       *childquals;
 468                 Node       *childqual;
 469                 ListCell   *parentvars;
 470                 ListCell   *childvars;
 471
 472                 /* append_rel_list contains all append rels; ignore others */
 473                 if (appinfo->parent_relid != parentRTindex)
 474                         continue;
 475
 476                 childRTindex = appinfo->child_relid;
 477                 childRTE = root->simple_rte_array[childRTindex];
 478
 479                 /*
 480                  * The child rel's RelOptInfo was already created during
 481                  * add_base_rels_to_query.
 482                  */
 483                 childrel = find_base_rel(root, childRTindex);
 484                 Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
 485
 486                 /*
 487                  * We have to copy the parent's targetlist and quals to the child,
 488                  * with appropriate substitution of variables.  However, only the
 489                  * baserestrictinfo quals are needed before we can check for
 490                  * constraint exclusion; so do that first and then check to see if we
 491                  * can disregard this child.
 492                  *
 493                  * As of 8.4, the child rel's targetlist might contain non-Var
 494                  * expressions, which means that substitution into the quals could
 495                  * produce opportunities for const-simplification, and perhaps even
 496                  * pseudoconstant quals.  To deal with this, we strip the RestrictInfo
 497                  * nodes, do the substitution, do const-simplification, and then
 498                  * reconstitute the RestrictInfo layer.
 499                  */
 500                 childquals = get_all_actual_clauses(rel->baserestrictinfo);
 501                 childquals = (List *) adjust_appendrel_attrs(root,
 502                                                                                                          (Node *) childquals,
 503                                                                                                          appinfo);
 504                 childqual = eval_const_expressions(root, (Node *)
 505                                                                                    make_ands_explicit(childquals));
 506                 if (childqual && IsA(childqual, Const) &&
 507                         (((Const *) childqual)->constisnull ||
 508                          !DatumGetBool(((Const *) childqual)->constvalue)))
 509                 {
 510                         /*
 511                          * Restriction reduces to constant FALSE or constant NULL after
 512                          * substitution, so this child need not be scanned.
 513                          */
 514                         set_dummy_rel_pathlist(childrel);
 515                         continue;
 516                 }
 517                 childquals = make_ands_implicit((Expr *) childqual);
 518                 childquals = make_restrictinfos_from_actual_clauses(root,
 519                                                                                                                         childquals);
 520                 childrel->baserestrictinfo = childquals;
 521
 522                 if (relation_excluded_by_constraints(root, childrel, childRTE))
 523                 {
 524                         /*
 525                          * This child need not be scanned, so we can omit it from the
 526                          * appendrel.
 527                          */
 528                         set_dummy_rel_pathlist(childrel);
 529                         continue;
 530                 }
 531
 532                 /*
 533                  * CE failed, so finish copying/modifying targetlist and join quals.
 534                  *
 535                  * Note: the resulting childrel->reltargetlist may contain arbitrary
 536                  * expressions, which normally would not occur in a reltargetlist.
 537                  * That is okay because nothing outside of this routine will look at
 538                  * the child rel's reltargetlist.  We do have to cope with the case
 539                  * while constructing attr_widths estimates below, though.
 540                  */
 541                 childrel->joininfo = (List *)
 542                         adjust_appendrel_attrs(root,
 543                                                                    (Node *) rel->joininfo,
 544                                                                    appinfo);
 545                 childrel->reltargetlist = (List *)
 546                         adjust_appendrel_attrs(root,
 547                                                                    (Node *) rel->reltargetlist,
 548                                                                    appinfo);
 549
 550                 /*
 551                  * We have to make child entries in the EquivalenceClass data
 552                  * structures as well.  This is needed either if the parent
 553                  * participates in some eclass joins (because we will want to consider
 554                  * inner-indexscan joins on the individual children) or if the parent
 555                  * has useful pathkeys (because we should try to build MergeAppend
 556                  * paths that produce those sort orderings).
 557                  */
 558                 if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
 559                         add_child_rel_equivalences(root, appinfo, rel, childrel);
 560                 childrel->has_eclass_joins = rel->has_eclass_joins;
 561
 562                 /*
 563                  * Note: we could compute appropriate attr_needed data for the child's
 564                  * variables, by transforming the parent's attr_needed through the
 565                  * translated_vars mapping.  However, currently there's no need
 566                  * because attr_needed is only examined for base relations not
 567                  * otherrels.  So we just leave the child's attr_needed empty.
 568                  */
 569
 570                 /*
 571                  * Compute the child's size.
 572                  */
 573                 set_rel_size(root, childrel, childRTindex, childRTE);
 574
 575                 /*
 576                  * It is possible that constraint exclusion detected a contradiction
 577                  * within a child subquery, even though we didn't prove one above.
 578                  * If so, we can skip this child.
 579                  */
 580                 if (IS_DUMMY_REL(childrel))
 581                         continue;
 582
 583                 /*
 584                  * Accumulate size information from each live child.
 585                  */
 586                 if (childrel->rows > 0)
 587                 {
 588                         parent_rows += childrel->rows;
 589                         parent_size += childrel->width * childrel->rows;
 590
 591                         /*
 592                          * Accumulate per-column estimates too.  We need not do anything
 593                          * for PlaceHolderVars in the parent list.  If child expression
 594                          * isn't a Var, or we didn't record a width estimate for it, we
 595                          * have to fall back on a datatype-based estimate.
 596                          *
 597                          * By construction, child's reltargetlist is 1-to-1 with parent's.
 598                          */
 599                         forboth(parentvars, rel->reltargetlist,
 600                                         childvars, childrel->reltargetlist)
 601                         {
 602                                 Var                *parentvar = (Var *) lfirst(parentvars);
 603                                 Node       *childvar = (Node *) lfirst(childvars);
 604
 605                                 if (IsA(parentvar, Var))
 606                                 {
 607                                         int                     pndx = parentvar->varattno - rel->min_attr;
 608                                         int32           child_width = 0;
 609
 610                                         if (IsA(childvar, Var))
 611                                         {
 612                                                 int             cndx = ((Var *) childvar)->varattno - childrel->min_attr;
 613
 614                                                 child_width = childrel->attr_widths[cndx];
 615                                         }
 616                                         if (child_width <= 0)
 617                                                 child_width = get_typavgwidth(exprType(childvar),
 618                                                                                                           exprTypmod(childvar));
 619                                         Assert(child_width > 0);
 620                                         parent_attrsizes[pndx] += child_width * childrel->rows;
 621                                 }
 622                         }
 623                 }
 624         }
 625
 626         /*
 627          * Save the finished size estimates.
 628          */
 629         rel->rows = parent_rows;
 630         if (parent_rows > 0)
 631         {
 632                 int                     i;
 633
 634                 rel->width = rint(parent_size / parent_rows);
 635                 for (i = 0; i < nattrs; i++)
 636                         rel->attr_widths[i] = rint(parent_attrsizes[i] / parent_rows);
 637         }
 638         else
 639                 rel->width = 0;                 /* attr_widths should be zero already */
 640
 641         /*
 642          * Set "raw tuples" count equal to "rows" for the appendrel; needed
 643          * because some places assume rel->tuples is valid for any baserel.
 644          */
 645         rel->tuples = parent_rows;
 646
 647         pfree(parent_attrsizes);
 648 }
 649
 650 /*
 651  * set_append_rel_pathlist
 652  *        Build access paths for an "append relation"
 653  */
 654 static void
 655 set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 656                                                 Index rti, RangeTblEntry *rte)
 657 {
 658         int                     parentRTindex = rti;
 659         List       *live_childrels = NIL;
 660         List       *subpaths = NIL;
 661         List       *all_child_pathkeys = NIL;
 662         List       *all_child_outers = NIL;
 663         ListCell   *l;
 664
 665         /*
 666          * Generate access paths for each member relation, and remember the
 667          * cheapest path for each one.  Also, identify all pathkeys (orderings)
 668          * and parameterizations (required_outer sets) available for the member
 669          * relations.
 670          */
 671         foreach(l, root->append_rel_list)
 672         {
 673                 AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
 674                 int                     childRTindex;
 675                 RangeTblEntry *childRTE;
 676                 RelOptInfo *childrel;
 677                 ListCell   *lcp;
 678
 679                 /* append_rel_list contains all append rels; ignore others */
 680                 if (appinfo->parent_relid != parentRTindex)
 681                         continue;
 682
 683                 /* Re-locate the child RTE and RelOptInfo */
 684                 childRTindex = appinfo->child_relid;
 685                 childRTE = root->simple_rte_array[childRTindex];
 686                 childrel = root->simple_rel_array[childRTindex];
 687
 688                 /*
 689                  * Compute the child's access paths.
 690                  */
 691                 set_rel_pathlist(root, childrel, childRTindex, childRTE);
 692
 693                 /*
 694                  * If child is dummy, ignore it.
 695                  */
 696                 if (IS_DUMMY_REL(childrel))
 697                         continue;
 698
 699                 /*
 700                  * Child is live, so add its cheapest access path to the Append path
 701                  * we are constructing for the parent.
 702                  */
 703                 subpaths = accumulate_append_subpath(subpaths,
 704                                                                                          childrel->cheapest_total_path);
 705
 706                 /* Remember which childrels are live, for logic below */
 707                 live_childrels = lappend(live_childrels, childrel);
 708
 709                 /*
 710                  * Collect lists of all the available path orderings and
 711                  * parameterizations for all the children.  We use these as a
 712                  * heuristic to indicate which sort orderings and parameterizations we
 713                  * should build Append and MergeAppend paths for.
 714                  */
 715                 foreach(lcp, childrel->pathlist)
 716                 {
 717                         Path       *childpath = (Path *) lfirst(lcp);
 718                         List       *childkeys = childpath->pathkeys;
 719                         Relids          childouter = PATH_REQ_OUTER(childpath);
 720
 721                         /* Unsorted paths don't contribute to pathkey list */
 722                         if (childkeys != NIL)
 723                         {
 724                                 ListCell   *lpk;
 725                                 bool            found = false;
 726
 727                                 /* Have we already seen this ordering? */
 728                                 foreach(lpk, all_child_pathkeys)
 729                                 {
 730                                         List       *existing_pathkeys = (List *) lfirst(lpk);
 731
 732                                         if (compare_pathkeys(existing_pathkeys,
 733                                                                                  childkeys) == PATHKEYS_EQUAL)
 734                                         {
 735                                                 found = true;
 736                                                 break;
 737                                         }
 738                                 }
 739                                 if (!found)
 740                                 {
 741                                         /* No, so add it to all_child_pathkeys */
 742                                         all_child_pathkeys = lappend(all_child_pathkeys,
 743                                                                                                  childkeys);
 744                                 }
 745                         }
 746
 747                         /* Unparameterized paths don't contribute to param-set list */
 748                         if (childouter)
 749                         {
 750                                 ListCell   *lco;
 751                                 bool            found = false;
 752
 753                                 /* Have we already seen this param set? */
 754                                 foreach(lco, all_child_outers)
 755                                 {
 756                                         Relids  existing_outers = (Relids) lfirst(lco);
 757
 758                                         if (bms_equal(existing_outers, childouter))
 759                                         {
 760                                                 found = true;
 761                                                 break;
 762                                         }
 763                                 }
 764                                 if (!found)
 765                                 {
 766                                         /* No, so add it to all_child_outers */
 767                                         all_child_outers = lappend(all_child_outers,
 768                                                                                            childouter);
 769                                 }
 770                         }
 771                 }
 772         }
 773
 774         /*
 775          * Next, build an unordered, unparameterized Append path for the rel.
 776          * (Note: this is correct even if we have zero or one live subpath due to
 777          * constraint exclusion.)
 778          */
 779         add_path(rel, (Path *) create_append_path(rel, subpaths, NULL));
 780
 781         /*
 782          * Build unparameterized MergeAppend paths based on the collected list of
 783          * child pathkeys.
 784          */
 785         generate_mergeappend_paths(root, rel, live_childrels, all_child_pathkeys);
 786
 787         /*
 788          * Build Append paths for each parameterization seen among the child rels.
 789          * (This may look pretty expensive, but in most cases of practical
 790          * interest, the child rels will expose mostly the same parameterizations,
 791          * so that not that many cases actually get considered here.)
 792          *
 793          * The Append node itself cannot enforce quals, so all qual checking must
 794          * be done in the child paths.  This means that to have a parameterized
 795          * Append path, we must have the exact same parameterization for each
 796          * child path; otherwise some children might be failing to check the
 797          * moved-down quals.  To make them match up, we can try to increase the
 798          * parameterization of lesser-parameterized paths.
 799          */
 800         foreach(l, all_child_outers)
 801         {
 802                 Relids  required_outer = (Relids) lfirst(l);
 803                 bool            ok = true;
 804                 ListCell   *lcr;
 805
 806                 /* Select the child paths for an Append with this parameterization */
 807                 subpaths = NIL;
 808                 foreach(lcr, live_childrels)
 809                 {
 810                         RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
 811                         Path       *cheapest_total;
 812
 813                         cheapest_total =
 814                                 get_cheapest_path_for_pathkeys(childrel->pathlist,
 815                                                                                            NIL,
 816                                                                                            required_outer,
 817                                                                                            TOTAL_COST);
 818                         Assert(cheapest_total != NULL);
 819
 820                         /* Children must have exactly the desired parameterization */
 821                         if (!bms_equal(PATH_REQ_OUTER(cheapest_total), required_outer))
 822                         {
 823                                 cheapest_total = reparameterize_path(root, cheapest_total,
 824                                                                                                          required_outer, 1.0);
 825                                 if (cheapest_total == NULL)
 826                                 {
 827                                         ok = false;
 828                                         break;
 829                                 }
 830                         }
 831
 832                         subpaths = accumulate_append_subpath(subpaths, cheapest_total);
 833                 }
 834
 835                 if (ok)
 836                         add_path(rel, (Path *)
 837                                          create_append_path(rel, subpaths, required_outer));
 838         }
 839
 840         /* Select cheapest paths */
 841         set_cheapest(rel);
 842 }
 843
 844 /*
 845  * generate_mergeappend_paths
 846  *              Generate MergeAppend paths for an append relation
 847  *
 848  * Generate a path for each ordering (pathkey list) appearing in
 849  * all_child_pathkeys.
 850  *
 851  * We consider both cheapest-startup and cheapest-total cases, ie, for each
 852  * interesting ordering, collect all the cheapest startup subpaths and all the
 853  * cheapest total paths, and build a MergeAppend path for each case.
 854  *
 855  * We don't currently generate any parameterized MergeAppend paths.  While
 856  * it would not take much more code here to do so, it's very unclear that it
 857  * is worth the planning cycles to investigate such paths: there's little
 858  * use for an ordered path on the inside of a nestloop.  In fact, it's likely
 859  * that the current coding of add_path would reject such paths out of hand,
 860  * because add_path gives no credit for sort ordering of parameterized paths,
 861  * and a parameterized MergeAppend is going to be more expensive than the
 862  * corresponding parameterized Append path.  If we ever try harder to support
 863  * parameterized mergejoin plans, it might be worth adding support for
 864  * parameterized MergeAppends to feed such joins.  (See notes in
 865  * optimizer/README for why that might not ever happen, though.)
 866  */
 867 static void
 868 generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
 869                                                    List *live_childrels,
 870                                                    List *all_child_pathkeys)
 871 {
 872         ListCell   *lcp;
 873
 874         foreach(lcp, all_child_pathkeys)
 875         {
 876                 List       *pathkeys = (List *) lfirst(lcp);
 877                 List       *startup_subpaths = NIL;
 878                 List       *total_subpaths = NIL;
 879                 bool            startup_neq_total = false;
 880                 ListCell   *lcr;
 881
 882                 /* Select the child paths for this ordering... */
 883                 foreach(lcr, live_childrels)
 884                 {
 885                         RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
 886                         Path       *cheapest_startup,
 887                                            *cheapest_total;
 888
 889                         /* Locate the right paths, if they are available. */
 890                         cheapest_startup =
 891                                 get_cheapest_path_for_pathkeys(childrel->pathlist,
 892                                                                                            pathkeys,
 893                                                                                            NULL,
 894                                                                                            STARTUP_COST);
 895                         cheapest_total =
 896                                 get_cheapest_path_for_pathkeys(childrel->pathlist,
 897                                                                                            pathkeys,
 898                                                                                            NULL,
 899                                                                                            TOTAL_COST);
 900
 901                         /*
 902                          * If we can't find any paths with the right order just use the
 903                          * cheapest-total path; we'll have to sort it later.
 904                          */
 905                         if (cheapest_startup == NULL || cheapest_total == NULL)
 906                         {
 907                                 cheapest_startup = cheapest_total =
 908                                         childrel->cheapest_total_path;
 909                                 Assert(cheapest_total != NULL);
 910                         }
 911
 912                         /*
 913                          * Notice whether we actually have different paths for the
 914                          * "cheapest" and "total" cases; frequently there will be no point
 915                          * in two create_merge_append_path() calls.
 916                          */
 917                         if (cheapest_startup != cheapest_total)
 918                                 startup_neq_total = true;
 919
 920                         startup_subpaths =
 921                                 accumulate_append_subpath(startup_subpaths, cheapest_startup);
 922                         total_subpaths =
 923                                 accumulate_append_subpath(total_subpaths, cheapest_total);
 924                 }
 925
 926                 /* ... and build the MergeAppend paths */
 927                 add_path(rel, (Path *) create_merge_append_path(root,
 928                                                                                                                 rel,
 929                                                                                                                 startup_subpaths,
 930                                                                                                                 pathkeys,
 931                                                                                                                 NULL));
 932                 if (startup_neq_total)
 933                         add_path(rel, (Path *) create_merge_append_path(root,
 934                                                                                                                         rel,
 935                                                                                                                         total_subpaths,
 936                                                                                                                         pathkeys,
 937                                                                                                                         NULL));
 938         }
 939 }
 940
 941 /*
 942  * accumulate_append_subpath
 943  *              Add a subpath to the list being built for an Append or MergeAppend
 944  *
 945  * It's possible that the child is itself an Append path, in which case
 946  * we can "cut out the middleman" and just add its child paths to our
 947  * own list.  (We don't try to do this earlier because we need to
 948  * apply both levels of transformation to the quals.)
 949  */
 950 static List *
 951 accumulate_append_subpath(List *subpaths, Path *path)
 952 {
 953         if (IsA(path, AppendPath))
 954         {
 955                 AppendPath *apath = (AppendPath *) path;
 956
 957                 /* list_copy is important here to avoid sharing list substructure */
 958                 return list_concat(subpaths, list_copy(apath->subpaths));
 959         }
 960         else
 961                 return lappend(subpaths, path);
 962 }
 963
 964 /*
 965  * set_dummy_rel_pathlist
 966  *        Build a dummy path for a relation that's been excluded by constraints
 967  *
 968  * Rather than inventing a special "dummy" path type, we represent this as an
 969  * AppendPath with no members (see also IS_DUMMY_PATH/IS_DUMMY_REL macros).
 970  */
 971 static void
 972 set_dummy_rel_pathlist(RelOptInfo *rel)
 973 {
 974         /* Set dummy size estimates --- we leave attr_widths[] as zeroes */
 975         rel->rows = 0;
 976         rel->width = 0;
 977
 978         /* Discard any pre-existing paths; no further need for them */
 979         rel->pathlist = NIL;
 980
 981         add_path(rel, (Path *) create_append_path(rel, NIL, NULL));
 982
 983         /* Select cheapest path (pretty easy in this case...) */
 984         set_cheapest(rel);
 985 }
 986
 987 /* quick-and-dirty test to see if any joining is needed */
 988 static bool
 989 has_multiple_baserels(PlannerInfo *root)
 990 {
 991         int                     num_base_rels = 0;
 992         Index           rti;
 993
 994         for (rti = 1; rti < root->simple_rel_array_size; rti++)
 995         {
 996                 RelOptInfo *brel = root->simple_rel_array[rti];
 997
 998                 if (brel == NULL)
 999                         continue;
1000
1001                 /* ignore RTEs that are "other rels" */
1002                 if (brel->reloptkind == RELOPT_BASEREL)
1003                         if (++num_base_rels > 1)
1004                                 return true;
1005         }
1006         return false;
1007 }
1008
1009 /*
1010  * set_subquery_pathlist
1011  *              Build the (single) access path for a subquery RTE
1012  *
1013  * There's no need for a separate set_subquery_size phase, since we don't
1014  * support parameterized paths for subqueries.
1015  */
1016 static void
1017 set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
1018                                           Index rti, RangeTblEntry *rte)
1019 {
1020         Query      *parse = root->parse;
1021         Query      *subquery = rte->subquery;
1022         bool       *differentTypes;
1023         double          tuple_fraction;
1024         PlannerInfo *subroot;
1025         List       *pathkeys;
1026
1027         /*
1028          * Must copy the Query so that planning doesn't mess up the RTE contents
1029          * (really really need to fix the planner to not scribble on its input,
1030          * someday).
1031          */
1032         subquery = copyObject(subquery);
1033
1034         /* We need a workspace for keeping track of set-op type coercions */
1035         differentTypes = (bool *)
1036                 palloc0((list_length(subquery->targetList) + 1) * sizeof(bool));
1037
1038         /*
1039          * If there are any restriction clauses that have been attached to the
1040          * subquery relation, consider pushing them down to become WHERE or HAVING
1041          * quals of the subquery itself.  This transformation is useful because it
1042          * may allow us to generate a better plan for the subquery than evaluating
1043          * all the subquery output rows and then filtering them.
1044          *
1045          * There are several cases where we cannot push down clauses. Restrictions
1046          * involving the subquery are checked by subquery_is_pushdown_safe().
1047          * Restrictions on individual clauses are checked by
1048          * qual_is_pushdown_safe().  Also, we don't want to push down
1049          * pseudoconstant clauses; better to have the gating node above the
1050          * subquery.
1051          *
1052          * Also, if the sub-query has "security_barrier" flag, it means the
1053          * sub-query originated from a view that must enforce row-level security.
1054          * We must not push down quals in order to avoid information leaks, either
1055          * via side-effects or error output.
1056          *
1057          * Non-pushed-down clauses will get evaluated as qpquals of the
1058          * SubqueryScan node.
1059          *
1060          * XXX Are there any cases where we want to make a policy decision not to
1061          * push down a pushable qual, because it'd result in a worse plan?
1062          */
1063         if (rel->baserestrictinfo != NIL &&
1064                 subquery_is_pushdown_safe(subquery, subquery, differentTypes))
1065         {
1066                 /* OK to consider pushing down individual quals */
1067                 List       *upperrestrictlist = NIL;
1068                 ListCell   *l;
1069
1070                 foreach(l, rel->baserestrictinfo)
1071                 {
1072                         RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
1073                         Node       *clause = (Node *) rinfo->clause;
1074
1075                         if (!rinfo->pseudoconstant &&
1076                                 (!rte->security_barrier ||
1077                                  !contain_leaky_functions(clause)) &&
1078                                 qual_is_pushdown_safe(subquery, rti, clause, differentTypes))
1079                         {
1080                                 /* Push it down */
1081                                 subquery_push_qual(subquery, rte, rti, clause);
1082                         }
1083                         else
1084                         {
1085                                 /* Keep it in the upper query */
1086                                 upperrestrictlist = lappend(upperrestrictlist, rinfo);
1087                         }
1088                 }
1089                 rel->baserestrictinfo = upperrestrictlist;
1090         }
1091
1092         pfree(differentTypes);
1093
1094         /*
1095          * We can safely pass the outer tuple_fraction down to the subquery if the
1096          * outer level has no joining, aggregation, or sorting to do. Otherwise
1097          * we'd better tell the subquery to plan for full retrieval. (XXX This
1098          * could probably be made more intelligent ...)
1099          */
1100         if (parse->hasAggs ||
1101                 parse->groupClause ||
1102                 parse->havingQual ||
1103                 parse->distinctClause ||
1104                 parse->sortClause ||
1105                 has_multiple_baserels(root))
1106                 tuple_fraction = 0.0;   /* default case */
1107         else
1108                 tuple_fraction = root->tuple_fraction;
1109
1110         /* Generate the plan for the subquery */
1111         rel->subplan = subquery_planner(root->glob, subquery,
1112                                                                         root,
1113                                                                         false, tuple_fraction,
1114                                                                         &subroot);
1115         rel->subroot = subroot;
1116
1117         /*
1118          * It's possible that constraint exclusion proved the subquery empty.
1119          * If so, it's convenient to turn it back into a dummy path so that we
1120          * will recognize appropriate optimizations at this level.
1121          */
1122         if (is_dummy_plan(rel->subplan))
1123         {
1124                 set_dummy_rel_pathlist(rel);
1125                 return;
1126         }
1127
1128         /* Mark rel with estimated output rows, width, etc */
1129         set_subquery_size_estimates(root, rel);
1130
1131         /* Convert subquery pathkeys to outer representation */
1132         pathkeys = convert_subquery_pathkeys(root, rel, subroot->query_pathkeys);
1133
1134         /* Generate appropriate path */
1135         add_path(rel, create_subqueryscan_path(root, rel, pathkeys, NULL));
1136
1137         /* Select cheapest path (pretty easy in this case...) */
1138         set_cheapest(rel);
1139 }
1140
1141 /*
1142  * set_function_pathlist
1143  *              Build the (single) access path for a function RTE
1144  */
1145 static void
1146 set_function_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
1147 {
1148         /* Generate appropriate path */
1149         add_path(rel, create_functionscan_path(root, rel));
1150
1151         /* Select cheapest path (pretty easy in this case...) */
1152         set_cheapest(rel);
1153 }
1154
1155 /*
1156  * set_values_pathlist
1157  *              Build the (single) access path for a VALUES RTE
1158  */
1159 static void
1160 set_values_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
1161 {
1162         /* Generate appropriate path */
1163         add_path(rel, create_valuesscan_path(root, rel));
1164
1165         /* Select cheapest path (pretty easy in this case...) */
1166         set_cheapest(rel);
1167 }
1168
1169 /*
1170  * set_cte_pathlist
1171  *              Build the (single) access path for a non-self-reference CTE RTE
1172  *
1173  * There's no need for a separate set_cte_size phase, since we don't
1174  * support parameterized paths for CTEs.
1175  */
1176 static void
1177 set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
1178 {
1179         Plan       *cteplan;
1180         PlannerInfo *cteroot;
1181         Index           levelsup;
1182         int                     ndx;
1183         ListCell   *lc;
1184         int                     plan_id;
1185
1186         /*
1187          * Find the referenced CTE, and locate the plan previously made for it.
1188          */
1189         levelsup = rte->ctelevelsup;
1190         cteroot = root;
1191         while (levelsup-- > 0)
1192         {
1193                 cteroot = cteroot->parent_root;
1194                 if (!cteroot)                   /* shouldn't happen */
1195                         elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
1196         }
1197
1198         /*
1199          * Note: cte_plan_ids can be shorter than cteList, if we are still working
1200          * on planning the CTEs (ie, this is a side-reference from another CTE).
1201          * So we mustn't use forboth here.
1202          */
1203         ndx = 0;
1204         foreach(lc, cteroot->parse->cteList)
1205         {
1206                 CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
1207
1208                 if (strcmp(cte->ctename, rte->ctename) == 0)
1209                         break;
1210                 ndx++;
1211         }
1212         if (lc == NULL)                         /* shouldn't happen */
1213                 elog(ERROR, "could not find CTE \"%s\"", rte->ctename);
1214         if (ndx >= list_length(cteroot->cte_plan_ids))
1215                 elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
1216         plan_id = list_nth_int(cteroot->cte_plan_ids, ndx);
1217         Assert(plan_id > 0);
1218         cteplan = (Plan *) list_nth(root->glob->subplans, plan_id - 1);
1219
1220         /* Mark rel with estimated output rows, width, etc */
1221         set_cte_size_estimates(root, rel, cteplan);
1222
1223         /* Generate appropriate path */
1224         add_path(rel, create_ctescan_path(root, rel));
1225
1226         /* Select cheapest path (pretty easy in this case...) */
1227         set_cheapest(rel);
1228 }
1229
1230 /*
1231  * set_worktable_pathlist
1232  *              Build the (single) access path for a self-reference CTE RTE
1233  *
1234  * There's no need for a separate set_worktable_size phase, since we don't
1235  * support parameterized paths for CTEs.
1236  */
1237 static void
1238 set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
1239 {
1240         Plan       *cteplan;
1241         PlannerInfo *cteroot;
1242         Index           levelsup;
1243
1244         /*
1245          * We need to find the non-recursive term's plan, which is in the plan
1246          * level that's processing the recursive UNION, which is one level *below*
1247          * where the CTE comes from.
1248          */
1249         levelsup = rte->ctelevelsup;
1250         if (levelsup == 0)                      /* shouldn't happen */
1251                 elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
1252         levelsup--;
1253         cteroot = root;
1254         while (levelsup-- > 0)
1255         {
1256                 cteroot = cteroot->parent_root;
1257                 if (!cteroot)                   /* shouldn't happen */
1258                         elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
1259         }
1260         cteplan = cteroot->non_recursive_plan;
1261         if (!cteplan)                           /* shouldn't happen */
1262                 elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
1263
1264         /* Mark rel with estimated output rows, width, etc */
1265         set_cte_size_estimates(root, rel, cteplan);
1266
1267         /* Generate appropriate path */
1268         add_path(rel, create_worktablescan_path(root, rel));
1269
1270         /* Select cheapest path (pretty easy in this case...) */
1271         set_cheapest(rel);
1272 }
1273
1274 /*
1275  * make_rel_from_joinlist
1276  *        Build access paths using a "joinlist" to guide the join path search.
1277  *
1278  * See comments for deconstruct_jointree() for definition of the joinlist
1279  * data structure.
1280  */
1281 static RelOptInfo *
1282 make_rel_from_joinlist(PlannerInfo *root, List *joinlist)
1283 {
1284         int                     levels_needed;
1285         List       *initial_rels;
1286         ListCell   *jl;
1287
1288         /*
1289          * Count the number of child joinlist nodes.  This is the depth of the
1290          * dynamic-programming algorithm we must employ to consider all ways of
1291          * joining the child nodes.
1292          */
1293         levels_needed = list_length(joinlist);
1294
1295         if (levels_needed <= 0)
1296                 return NULL;                    /* nothing to do? */
1297
1298         /*
1299          * Construct a list of rels corresponding to the child joinlist nodes.
1300          * This may contain both base rels and rels constructed according to
1301          * sub-joinlists.
1302          */
1303         initial_rels = NIL;
1304         foreach(jl, joinlist)
1305         {
1306                 Node       *jlnode = (Node *) lfirst(jl);
1307                 RelOptInfo *thisrel;
1308
1309                 if (IsA(jlnode, RangeTblRef))
1310                 {
1311                         int                     varno = ((RangeTblRef *) jlnode)->rtindex;
1312
1313                         thisrel = find_base_rel(root, varno);
1314                 }
1315                 else if (IsA(jlnode, List))
1316                 {
1317                         /* Recurse to handle subproblem */
1318                         thisrel = make_rel_from_joinlist(root, (List *) jlnode);
1319                 }
1320                 else
1321                 {
1322                         elog(ERROR, "unrecognized joinlist node type: %d",
1323                                  (int) nodeTag(jlnode));
1324                         thisrel = NULL;         /* keep compiler quiet */
1325                 }
1326
1327                 initial_rels = lappend(initial_rels, thisrel);
1328         }
1329
1330         if (levels_needed == 1)
1331         {
1332                 /*
1333                  * Single joinlist node, so we're done.
1334                  */
1335                 return (RelOptInfo *) linitial(initial_rels);
1336         }
1337         else
1338         {
1339                 /*
1340                  * Consider the different orders in which we could join the rels,
1341                  * using a plugin, GEQO, or the regular join search code.
1342                  *
1343                  * We put the initial_rels list into a PlannerInfo field because
1344                  * has_legal_joinclause() needs to look at it (ugly :-().
1345                  */
1346                 root->initial_rels = initial_rels;
1347
1348                 if (join_search_hook)
1349                         return (*join_search_hook) (root, levels_needed, initial_rels);
1350                 else if (enable_geqo && levels_needed >= geqo_threshold)
1351                         return geqo(root, levels_needed, initial_rels);
1352                 else
1353                         return standard_join_search(root, levels_needed, initial_rels);
1354         }
1355 }
1356
1357 /*
1358  * standard_join_search
1359  *        Find possible joinpaths for a query by successively finding ways
1360  *        to join component relations into join relations.
1361  *
1362  * 'levels_needed' is the number of iterations needed, ie, the number of
1363  *              independent jointree items in the query.  This is > 1.
1364  *
1365  * 'initial_rels' is a list of RelOptInfo nodes for each independent
1366  *              jointree item.  These are the components to be joined together.
1367  *              Note that levels_needed == list_length(initial_rels).
1368  *
1369  * Returns the final level of join relations, i.e., the relation that is
1370  * the result of joining all the original relations together.
1371  * At least one implementation path must be provided for this relation and
1372  * all required sub-relations.
1373  *
1374  * To support loadable plugins that modify planner behavior by changing the
1375  * join searching algorithm, we provide a hook variable that lets a plugin
1376  * replace or supplement this function.  Any such hook must return the same
1377  * final join relation as the standard code would, but it might have a
1378  * different set of implementation paths attached, and only the sub-joinrels
1379  * needed for these paths need have been instantiated.
1380  *
1381  * Note to plugin authors: the functions invoked during standard_join_search()
1382  * modify root->join_rel_list and root->join_rel_hash.  If you want to do more
1383  * than one join-order search, you'll probably need to save and restore the
1384  * original states of those data structures.  See geqo_eval() for an example.
1385  */
1386 RelOptInfo *
1387 standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
1388 {
1389         int                     lev;
1390         RelOptInfo *rel;
1391
1392         /*
1393          * This function cannot be invoked recursively within any one planning
1394          * problem, so join_rel_level[] can't be in use already.
1395          */
1396         Assert(root->join_rel_level == NULL);
1397
1398         /*
1399          * We employ a simple "dynamic programming" algorithm: we first find all
1400          * ways to build joins of two jointree items, then all ways to build joins
1401          * of three items (from two-item joins and single items), then four-item
1402          * joins, and so on until we have considered all ways to join all the
1403          * items into one rel.
1404          *
1405          * root->join_rel_level[j] is a list of all the j-item rels.  Initially we
1406          * set root->join_rel_level[1] to represent all the single-jointree-item
1407          * relations.
1408          */
1409         root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));
1410
1411         root->join_rel_level[1] = initial_rels;
1412
1413         for (lev = 2; lev <= levels_needed; lev++)
1414         {
1415                 ListCell   *lc;
1416
1417                 /*
1418                  * Determine all possible pairs of relations to be joined at this
1419                  * level, and build paths for making each one from every available
1420                  * pair of lower-level relations.
1421                  */
1422                 join_search_one_level(root, lev);
1423
1424                 /*
1425                  * Do cleanup work on each just-processed rel.
1426                  */
1427                 foreach(lc, root->join_rel_level[lev])
1428                 {
1429                         rel = (RelOptInfo *) lfirst(lc);
1430
1431                         /* Find and save the cheapest paths for this rel */
1432                         set_cheapest(rel);
1433
1434 #ifdef OPTIMIZER_DEBUG
1435                         debug_print_rel(root, rel);
1436 #endif
1437                 }
1438         }
1439
1440         /*
1441          * We should have a single rel at the final level.
1442          */
1443         if (root->join_rel_level[levels_needed] == NIL)
1444                 elog(ERROR, "failed to build any %d-way joins", levels_needed);
1445         Assert(list_length(root->join_rel_level[levels_needed]) == 1);
1446
1447         rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);
1448
1449         root->join_rel_level = NULL;
1450
1451         return rel;
1452 }
1453
1454 /*****************************************************************************
1455  *                      PUSHING QUALS DOWN INTO SUBQUERIES
1456  *****************************************************************************/
1457
1458 /*
1459  * subquery_is_pushdown_safe - is a subquery safe for pushing down quals?
1460  *
1461  * subquery is the particular component query being checked.  topquery
1462  * is the top component of a set-operations tree (the same Query if no
1463  * set-op is involved).
1464  *
1465  * Conditions checked here:
1466  *
1467  * 1. If the subquery has a LIMIT clause, we must not push down any quals,
1468  * since that could change the set of rows returned.
1469  *
1470  * 2. If the subquery contains any window functions, we can't push quals
1471  * into it, because that could change the results.
1472  *
1473  * 3. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
1474  * quals into it, because that could change the results.
1475  *
1476  * 4. For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
1477  * push quals into each component query, but the quals can only reference
1478  * subquery columns that suffer no type coercions in the set operation.
1479  * Otherwise there are possible semantic gotchas.  So, we check the
1480  * component queries to see if any of them have different output types;
1481  * differentTypes[k] is set true if column k has different type in any
1482  * component.
1483  */
1484 static bool
1485 subquery_is_pushdown_safe(Query *subquery, Query *topquery,
1486                                                   bool *differentTypes)
1487 {
1488         SetOperationStmt *topop;
1489
1490         /* Check point 1 */
1491         if (subquery->limitOffset != NULL || subquery->limitCount != NULL)
1492                 return false;
1493
1494         /* Check point 2 */
1495         if (subquery->hasWindowFuncs)
1496                 return false;
1497
1498         /* Are we at top level, or looking at a setop component? */
1499         if (subquery == topquery)
1500         {
1501                 /* Top level, so check any component queries */
1502                 if (subquery->setOperations != NULL)
1503                         if (!recurse_pushdown_safe(subquery->setOperations, topquery,
1504                                                                            differentTypes))
1505                                 return false;
1506         }
1507         else
1508         {
1509                 /* Setop component must not have more components (too weird) */
1510                 if (subquery->setOperations != NULL)
1511                         return false;
1512                 /* Check whether setop component output types match top level */
1513                 topop = (SetOperationStmt *) topquery->setOperations;
1514                 Assert(topop && IsA(topop, SetOperationStmt));
1515                 compare_tlist_datatypes(subquery->targetList,
1516                                                                 topop->colTypes,
1517                                                                 differentTypes);
1518         }
1519         return true;
1520 }
1521
1522 /*
1523  * Helper routine to recurse through setOperations tree
1524  */
1525 static bool
1526 recurse_pushdown_safe(Node *setOp, Query *topquery,
1527                                           bool *differentTypes)
1528 {
1529         if (IsA(setOp, RangeTblRef))
1530         {
1531                 RangeTblRef *rtr = (RangeTblRef *) setOp;
1532                 RangeTblEntry *rte = rt_fetch(rtr->rtindex, topquery->rtable);
1533                 Query      *subquery = rte->subquery;
1534
1535                 Assert(subquery != NULL);
1536                 return subquery_is_pushdown_safe(subquery, topquery, differentTypes);
1537         }
1538         else if (IsA(setOp, SetOperationStmt))
1539         {
1540                 SetOperationStmt *op = (SetOperationStmt *) setOp;
1541
1542                 /* EXCEPT is no good */
1543                 if (op->op == SETOP_EXCEPT)
1544                         return false;
1545                 /* Else recurse */
1546                 if (!recurse_pushdown_safe(op->larg, topquery, differentTypes))
1547                         return false;
1548                 if (!recurse_pushdown_safe(op->rarg, topquery, differentTypes))
1549                         return false;
1550         }
1551         else
1552         {
1553                 elog(ERROR, "unrecognized node type: %d",
1554                          (int) nodeTag(setOp));
1555         }
1556         return true;
1557 }
1558
1559 /*
1560  * Compare tlist's datatypes against the list of set-operation result types.
1561  * For any items that are different, mark the appropriate element of
1562  * differentTypes[] to show that this column will have type conversions.
1563  *
1564  * We don't have to care about typmods here: the only allowed difference
1565  * between set-op input and output typmods is input is a specific typmod
1566  * and output is -1, and that does not require a coercion.
1567  */
1568 static void
1569 compare_tlist_datatypes(List *tlist, List *colTypes,
1570                                                 bool *differentTypes)
1571 {
1572         ListCell   *l;
1573         ListCell   *colType = list_head(colTypes);
1574
1575         foreach(l, tlist)
1576         {
1577                 TargetEntry *tle = (TargetEntry *) lfirst(l);
1578
1579                 if (tle->resjunk)
1580                         continue;                       /* ignore resjunk columns */
1581                 if (colType == NULL)
1582                         elog(ERROR, "wrong number of tlist entries");
1583                 if (exprType((Node *) tle->expr) != lfirst_oid(colType))
1584                         differentTypes[tle->resno] = true;
1585                 colType = lnext(colType);
1586         }
1587         if (colType != NULL)
1588                 elog(ERROR, "wrong number of tlist entries");
1589 }
1590
1591 /*
1592  * qual_is_pushdown_safe - is a particular qual safe to push down?
1593  *
1594  * qual is a restriction clause applying to the given subquery (whose RTE
1595  * has index rti in the parent query).
1596  *
1597  * Conditions checked here:
1598  *
1599  * 1. The qual must not contain any subselects (mainly because I'm not sure
1600  * it will work correctly: sublinks will already have been transformed into
1601  * subplans in the qual, but not in the subquery).
1602  *
1603  * 2. The qual must not refer to the whole-row output of the subquery
1604  * (since there is no easy way to name that within the subquery itself).
1605  *
1606  * 3. The qual must not refer to any subquery output columns that were
1607  * found to have inconsistent types across a set operation tree by
1608  * subquery_is_pushdown_safe().
1609  *
1610  * 4. If the subquery uses DISTINCT ON, we must not push down any quals that
1611  * refer to non-DISTINCT output columns, because that could change the set
1612  * of rows returned.  (This condition is vacuous for DISTINCT, because then
1613  * there are no non-DISTINCT output columns, so we needn't check.  But note
1614  * we are assuming that the qual can't distinguish values that the DISTINCT
1615  * operator sees as equal.      This is a bit shaky but we have no way to test
1616  * for the case, and it's unlikely enough that we shouldn't refuse the
1617  * optimization just because it could theoretically happen.)
1618  *
1619  * 5. We must not push down any quals that refer to subselect outputs that
1620  * return sets, else we'd introduce functions-returning-sets into the
1621  * subquery's WHERE/HAVING quals.
1622  *
1623  * 6. We must not push down any quals that refer to subselect outputs that
1624  * contain volatile functions, for fear of introducing strange results due
1625  * to multiple evaluation of a volatile function.
1626  */
1627 static bool
1628 qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
1629                                           bool *differentTypes)
1630 {
1631         bool            safe = true;
1632         List       *vars;
1633         ListCell   *vl;
1634         Bitmapset  *tested = NULL;
1635
1636         /* Refuse subselects (point 1) */
1637         if (contain_subplans(qual))
1638                 return false;
1639
1640         /*
1641          * It would be unsafe to push down window function calls, but at least for
1642          * the moment we could never see any in a qual anyhow.  (The same applies
1643          * to aggregates, which we check for in pull_var_clause below.)
1644          */
1645         Assert(!contain_window_function(qual));
1646
1647         /*
1648          * Examine all Vars used in clause; since it's a restriction clause, all
1649          * such Vars must refer to subselect output columns.
1650          */
1651         vars = pull_var_clause(qual,
1652                                                    PVC_REJECT_AGGREGATES,
1653                                                    PVC_INCLUDE_PLACEHOLDERS);
1654         foreach(vl, vars)
1655         {
1656                 Var                *var = (Var *) lfirst(vl);
1657                 TargetEntry *tle;
1658
1659                 /*
1660                  * XXX Punt if we find any PlaceHolderVars in the restriction clause.
1661                  * It's not clear whether a PHV could safely be pushed down, and even
1662                  * less clear whether such a situation could arise in any cases of
1663                  * practical interest anyway.  So for the moment, just refuse to push
1664                  * down.
1665                  */
1666                 if (!IsA(var, Var))
1667                 {
1668                         safe = false;
1669                         break;
1670                 }
1671
1672                 Assert(var->varno == rti);
1673
1674                 /* Check point 2 */
1675                 if (var->varattno == 0)
1676                 {
1677                         safe = false;
1678                         break;
1679                 }
1680
1681                 /*
1682                  * We use a bitmapset to avoid testing the same attno more than once.
1683                  * (NB: this only works because subquery outputs can't have negative
1684                  * attnos.)
1685                  */
1686                 if (bms_is_member(var->varattno, tested))
1687                         continue;
1688                 tested = bms_add_member(tested, var->varattno);
1689
1690                 /* Check point 3 */
1691                 if (differentTypes[var->varattno])
1692                 {
1693                         safe = false;
1694                         break;
1695                 }
1696
1697                 /* Must find the tlist element referenced by the Var */
1698                 tle = get_tle_by_resno(subquery->targetList, var->varattno);
1699                 Assert(tle != NULL);
1700                 Assert(!tle->resjunk);
1701
1702                 /* If subquery uses DISTINCT ON, check point 4 */
1703                 if (subquery->hasDistinctOn &&
1704                         !targetIsInSortList(tle, InvalidOid, subquery->distinctClause))
1705                 {
1706                         /* non-DISTINCT column, so fail */
1707                         safe = false;
1708                         break;
1709                 }
1710
1711                 /* Refuse functions returning sets (point 5) */
1712                 if (expression_returns_set((Node *) tle->expr))
1713                 {
1714                         safe = false;
1715                         break;
1716                 }
1717
1718                 /* Refuse volatile functions (point 6) */
1719                 if (contain_volatile_functions((Node *) tle->expr))
1720                 {
1721                         safe = false;
1722                         break;
1723                 }
1724         }
1725
1726         list_free(vars);
1727         bms_free(tested);
1728
1729         return safe;
1730 }
1731
1732 /*
1733  * subquery_push_qual - push down a qual that we have determined is safe
1734  */
1735 static void
1736 subquery_push_qual(Query *subquery, RangeTblEntry *rte, Index rti, Node *qual)
1737 {
1738         if (subquery->setOperations != NULL)
1739         {
1740                 /* Recurse to push it separately to each component query */
1741                 recurse_push_qual(subquery->setOperations, subquery,
1742                                                   rte, rti, qual);
1743         }
1744         else
1745         {
1746                 /*
1747                  * We need to replace Vars in the qual (which must refer to outputs of
1748                  * the subquery) with copies of the subquery's targetlist expressions.
1749                  * Note that at this point, any uplevel Vars in the qual should have
1750                  * been replaced with Params, so they need no work.
1751                  *
1752                  * This step also ensures that when we are pushing into a setop tree,
1753                  * each component query gets its own copy of the qual.
1754                  */
1755                 qual = ResolveNew(qual, rti, 0, rte,
1756                                                   subquery->targetList,
1757                                                   CMD_SELECT, 0,
1758                                                   &subquery->hasSubLinks);
1759
1760                 /*
1761                  * Now attach the qual to the proper place: normally WHERE, but if the
1762                  * subquery uses grouping or aggregation, put it in HAVING (since the
1763                  * qual really refers to the group-result rows).
1764                  */
1765                 if (subquery->hasAggs || subquery->groupClause || subquery->havingQual)
1766                         subquery->havingQual = make_and_qual(subquery->havingQual, qual);
1767                 else
1768                         subquery->jointree->quals =
1769                                 make_and_qual(subquery->jointree->quals, qual);
1770
1771                 /*
1772                  * We need not change the subquery's hasAggs or hasSublinks flags,
1773                  * since we can't be pushing down any aggregates that weren't there
1774                  * before, and we don't push down subselects at all.
1775                  */
1776         }
1777 }
1778
1779 /*
1780  * Helper routine to recurse through setOperations tree
1781  */
1782 static void
1783 recurse_push_qual(Node *setOp, Query *topquery,
1784                                   RangeTblEntry *rte, Index rti, Node *qual)
1785 {
1786         if (IsA(setOp, RangeTblRef))
1787         {
1788                 RangeTblRef *rtr = (RangeTblRef *) setOp;
1789                 RangeTblEntry *subrte = rt_fetch(rtr->rtindex, topquery->rtable);
1790                 Query      *subquery = subrte->subquery;
1791
1792                 Assert(subquery != NULL);
1793                 subquery_push_qual(subquery, rte, rti, qual);
1794         }
1795         else if (IsA(setOp, SetOperationStmt))
1796         {
1797                 SetOperationStmt *op = (SetOperationStmt *) setOp;
1798
1799                 recurse_push_qual(op->larg, topquery, rte, rti, qual);
1800                 recurse_push_qual(op->rarg, topquery, rte, rti, qual);
1801         }
1802         else
1803         {
1804                 elog(ERROR, "unrecognized node type: %d",
1805                          (int) nodeTag(setOp));
1806         }
1807 }
1808
1809 /*****************************************************************************
1810  *                      DEBUG SUPPORT
1811  *****************************************************************************/
1812
1813 #ifdef OPTIMIZER_DEBUG
1814
1815 static void
1816 print_relids(Relids relids)
1817 {
1818         Relids          tmprelids;
1819         int                     x;
1820         bool            first = true;
1821
1822         tmprelids = bms_copy(relids);
1823         while ((x = bms_first_member(tmprelids)) >= 0)
1824         {
1825                 if (!first)
1826                         printf(" ");
1827                 printf("%d", x);
1828                 first = false;
1829         }
1830         bms_free(tmprelids);
1831 }
1832
1833 static void
1834 print_restrictclauses(PlannerInfo *root, List *clauses)
1835 {
1836         ListCell   *l;
1837
1838         foreach(l, clauses)
1839         {
1840                 RestrictInfo *c = lfirst(l);
1841
1842                 print_expr((Node *) c->clause, root->parse->rtable);
1843                 if (lnext(l))
1844                         printf(", ");
1845         }
1846 }
1847
1848 static void
1849 print_path(PlannerInfo *root, Path *path, int indent)
1850 {
1851         const char *ptype;
1852         bool            join = false;
1853         Path       *subpath = NULL;
1854         int                     i;
1855
1856         switch (nodeTag(path))
1857         {
1858                 case T_Path:
1859                         ptype = "SeqScan";
1860                         break;
1861                 case T_IndexPath:
1862                         ptype = "IdxScan";
1863                         break;
1864                 case T_BitmapHeapPath:
1865                         ptype = "BitmapHeapScan";
1866                         break;
1867                 case T_BitmapAndPath:
1868                         ptype = "BitmapAndPath";
1869                         break;
1870                 case T_BitmapOrPath:
1871                         ptype = "BitmapOrPath";
1872                         break;
1873                 case T_TidPath:
1874                         ptype = "TidScan";
1875                         break;
1876                 case T_ForeignPath:
1877                         ptype = "ForeignScan";
1878                         break;
1879                 case T_AppendPath:
1880                         ptype = "Append";
1881                         break;
1882                 case T_MergeAppendPath:
1883                         ptype = "MergeAppend";
1884                         break;
1885                 case T_ResultPath:
1886                         ptype = "Result";
1887                         break;
1888                 case T_MaterialPath:
1889                         ptype = "Material";
1890                         subpath = ((MaterialPath *) path)->subpath;
1891                         break;
1892                 case T_UniquePath:
1893                         ptype = "Unique";
1894                         subpath = ((UniquePath *) path)->subpath;
1895                         break;
1896                 case T_NestPath:
1897                         ptype = "NestLoop";
1898                         join = true;
1899                         break;
1900                 case T_MergePath:
1901                         ptype = "MergeJoin";
1902                         join = true;
1903                         break;
1904                 case T_HashPath:
1905                         ptype = "HashJoin";
1906                         join = true;
1907                         break;
1908                 default:
1909                         ptype = "???Path";
1910                         break;
1911         }
1912
1913         for (i = 0; i < indent; i++)
1914                 printf("\t");
1915         printf("%s", ptype);
1916
1917         if (path->parent)
1918         {
1919                 printf("(");
1920                 print_relids(path->parent->relids);
1921                 printf(") rows=%.0f", path->parent->rows);
1922         }
1923         printf(" cost=%.2f..%.2f\n", path->startup_cost, path->total_cost);
1924
1925         if (path->pathkeys)
1926         {
1927                 for (i = 0; i < indent; i++)
1928                         printf("\t");
1929                 printf("  pathkeys: ");
1930                 print_pathkeys(path->pathkeys, root->parse->rtable);
1931         }
1932
1933         if (join)
1934         {
1935                 JoinPath   *jp = (JoinPath *) path;
1936
1937                 for (i = 0; i < indent; i++)
1938                         printf("\t");
1939                 printf("  clauses: ");
1940                 print_restrictclauses(root, jp->joinrestrictinfo);
1941                 printf("\n");
1942
1943                 if (IsA(path, MergePath))
1944                 {
1945                         MergePath  *mp = (MergePath *) path;
1946
1947                         for (i = 0; i < indent; i++)
1948                                 printf("\t");
1949                         printf("  sortouter=%d sortinner=%d materializeinner=%d\n",
1950                                    ((mp->outersortkeys) ? 1 : 0),
1951                                    ((mp->innersortkeys) ? 1 : 0),
1952                                    ((mp->materialize_inner) ? 1 : 0));
1953                 }
1954
1955                 print_path(root, jp->outerjoinpath, indent + 1);
1956                 print_path(root, jp->innerjoinpath, indent + 1);
1957         }
1958
1959         if (subpath)
1960                 print_path(root, subpath, indent + 1);
1961 }
1962
1963 void
1964 debug_print_rel(PlannerInfo *root, RelOptInfo *rel)
1965 {
1966         ListCell   *l;
1967
1968         printf("RELOPTINFO (");
1969         print_relids(rel->relids);
1970         printf("): rows=%.0f width=%d\n", rel->rows, rel->width);
1971
1972         if (rel->baserestrictinfo)
1973         {
1974                 printf("\tbaserestrictinfo: ");
1975                 print_restrictclauses(root, rel->baserestrictinfo);
1976                 printf("\n");
1977         }
1978
1979         if (rel->joininfo)
1980         {
1981                 printf("\tjoininfo: ");
1982                 print_restrictclauses(root, rel->joininfo);
1983                 printf("\n");
1984         }
1985
1986         printf("\tpath list:\n");
1987         foreach(l, rel->pathlist)
1988                 print_path(root, lfirst(l), 1);
1989         printf("\n\tcheapest startup path:\n");
1990         print_path(root, rel->cheapest_startup_path, 1);
1991         printf("\n\tcheapest total path:\n");
1992         print_path(root, rel->cheapest_total_path, 1);
1993         printf("\n");
1994         fflush(stdout);
1995 }
1996
1997 #endif   /* OPTIMIZER_DEBUG */