core.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * core.c
   4  *        Routines copied from PostgreSQL core distribution.
   5  *
   6  * The main purpose of this files is having access to static functions in core.
   7  * Another purpose is tweaking functions behavior by replacing part of them by
   8  * macro definitions. See at the end of pg_hint_plan.c for details. Anyway,
   9  * this file *must* contain required functions without making any change.
  10  *
  11  * This file contains the following functions from corresponding files.
  12  *
  13  * src/backend/optimizer/path/allpaths.c
  14  *
  15  *  public functions:
  16  *     standard_join_search(): This funcion is not static. The reason for
  17  *        including this function is make_rels_by_clause_joins. In order to
  18  *        avoid generating apparently unwanted join combination, we decided to
  19  *        change the behavior of make_join_rel, which is called under this
  20  *        function.
  21  *
  22  *      static functions:
  23  *         set_plain_rel_pathlist()
  24  *         set_append_rel_pathlist()
  25  *         create_plain_partial_paths()
  26  *
  27  * src/backend/optimizer/path/joinrels.c
  28  *
  29  *      public functions:
  30  *     join_search_one_level(): We have to modify this to call my definition of
  31  *                  make_rels_by_clause_joins.
  32  *
  33  *      static functions:
  34  *     make_rels_by_clause_joins()
  35  *     make_rels_by_clauseless_joins()
  36  *     join_is_legal()
  37  *     has_join_restriction()
  38  *     restriction_is_constant_false()
  39  *     build_child_join_sjinfo()
  40  *     get_matching_part_pairs()
  41  *     compute_partition_bounds()
  42  *     try_partitionwise_join()
  43  *
  44  * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  45  * Portions Copyright (c) 1994, Regents of the University of California
  46  *
  47  *-------------------------------------------------------------------------
  48  */
  49
  50 static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
  51                                                                                 RelOptInfo *rel2, RelOptInfo *joinrel,
  52                                                                                 SpecialJoinInfo *sjinfo, List *restrictlist);
  53
  54 /*
  55  * set_plain_rel_pathlist
  56  *        Build access paths for a plain relation (no subquery, no inheritance)
  57  */
  58 static void
  59 set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  60 {
  61         Relids          required_outer;
  62
  63         /*
  64          * We don't support pushing join clauses into the quals of a seqscan, but
  65          * it could still have required parameterization due to LATERAL refs in
  66          * its tlist.
  67          */
  68         required_outer = rel->lateral_relids;
  69
  70         /* Consider sequential scan */
  71         add_path(rel, create_seqscan_path(root, rel, required_outer, 0));
  72
  73         /* If appropriate, consider parallel sequential scan */
  74         if (rel->consider_parallel && required_outer == NULL)
  75                 create_plain_partial_paths(root, rel);
  76
  77         /* Consider index scans */
  78         create_index_paths(root, rel);
  79
  80         /* Consider TID scans */
  81         create_tidscan_paths(root, rel);
  82 }
  83
  84
  85 /*
  86  * set_append_rel_pathlist
  87  *        Build access paths for an "append relation"
  88  */
  89 static void
  90 set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  91                                                 Index rti, RangeTblEntry *rte)
  92 {
  93         int                     parentRTindex = rti;
  94         List       *live_childrels = NIL;
  95         ListCell   *l;
  96
  97         /*
  98          * Generate access paths for each member relation, and remember the
  99          * non-dummy children.
 100          */
 101         foreach(l, root->append_rel_list)
 102         {
 103                 AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
 104                 int                     childRTindex;
 105                 RangeTblEntry *childRTE;
 106                 RelOptInfo *childrel;
 107
 108                 /* append_rel_list contains all append rels; ignore others */
 109                 if (appinfo->parent_relid != parentRTindex)
 110                         continue;
 111
 112                 /* Re-locate the child RTE and RelOptInfo */
 113                 childRTindex = appinfo->child_relid;
 114                 childRTE = root->simple_rte_array[childRTindex];
 115                 childrel = root->simple_rel_array[childRTindex];
 116
 117                 /*
 118                  * If set_append_rel_size() decided the parent appendrel was
 119                  * parallel-unsafe at some point after visiting this child rel, we
 120                  * need to propagate the unsafety marking down to the child, so that
 121                  * we don't generate useless partial paths for it.
 122                  */
 123                 if (!rel->consider_parallel)
 124                         childrel->consider_parallel = false;
 125
 126                 /*
 127                  * Compute the child's access paths.
 128                  */
 129                 set_rel_pathlist(root, childrel, childRTindex, childRTE);
 130
 131                 /*
 132                  * If child is dummy, ignore it.
 133                  */
 134                 if (IS_DUMMY_REL(childrel))
 135                         continue;
 136
 137                 /* Bubble up childrel's partitioned children. */
 138                 if (rel->part_scheme)
 139                         rel->partitioned_child_rels =
 140                                 list_concat(rel->partitioned_child_rels,
 141                                                         childrel->partitioned_child_rels);
 142
 143                 /*
 144                  * Child is live, so add it to the live_childrels list for use below.
 145                  */
 146                 live_childrels = lappend(live_childrels, childrel);
 147         }
 148
 149         /* Add paths to the append relation. */
 150         add_paths_to_append_rel(root, rel, live_childrels);
 151 }
 152
 153
 154 /*
 155  * standard_join_search
 156  *        Find possible joinpaths for a query by successively finding ways
 157  *        to join component relations into join relations.
 158  *
 159  * 'levels_needed' is the number of iterations needed, ie, the number of
 160  *              independent jointree items in the query.  This is > 1.
 161  *
 162  * 'initial_rels' is a list of RelOptInfo nodes for each independent
 163  *              jointree item.  These are the components to be joined together.
 164  *              Note that levels_needed == list_length(initial_rels).
 165  *
 166  * Returns the final level of join relations, i.e., the relation that is
 167  * the result of joining all the original relations together.
 168  * At least one implementation path must be provided for this relation and
 169  * all required sub-relations.
 170  *
 171  * To support loadable plugins that modify planner behavior by changing the
 172  * join searching algorithm, we provide a hook variable that lets a plugin
 173  * replace or supplement this function.  Any such hook must return the same
 174  * final join relation as the standard code would, but it might have a
 175  * different set of implementation paths attached, and only the sub-joinrels
 176  * needed for these paths need have been instantiated.
 177  *
 178  * Note to plugin authors: the functions invoked during standard_join_search()
 179  * modify root->join_rel_list and root->join_rel_hash.  If you want to do more
 180  * than one join-order search, you'll probably need to save and restore the
 181  * original states of those data structures.  See geqo_eval() for an example.
 182  */
 183 RelOptInfo *
 184 standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
 185 {
 186         int                     lev;
 187         RelOptInfo *rel;
 188
 189         /*
 190          * This function cannot be invoked recursively within any one planning
 191          * problem, so join_rel_level[] can't be in use already.
 192          */
 193         Assert(root->join_rel_level == NULL);
 194
 195         /*
 196          * We employ a simple "dynamic programming" algorithm: we first find all
 197          * ways to build joins of two jointree items, then all ways to build joins
 198          * of three items (from two-item joins and single items), then four-item
 199          * joins, and so on until we have considered all ways to join all the
 200          * items into one rel.
 201          *
 202          * root->join_rel_level[j] is a list of all the j-item rels.  Initially we
 203          * set root->join_rel_level[1] to represent all the single-jointree-item
 204          * relations.
 205          */
 206         root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));
 207
 208         root->join_rel_level[1] = initial_rels;
 209
 210         for (lev = 2; lev <= levels_needed; lev++)
 211         {
 212                 ListCell   *lc;
 213
 214                 /*
 215                  * Determine all possible pairs of relations to be joined at this
 216                  * level, and build paths for making each one from every available
 217                  * pair of lower-level relations.
 218                  */
 219                 join_search_one_level(root, lev);
 220
 221                 /*
 222                  * Run generate_partitionwise_join_paths() and generate_gather_paths()
 223                  * for each just-processed joinrel.  We could not do this earlier
 224                  * because both regular and partial paths can get added to a
 225                  * particular joinrel at multiple times within join_search_one_level.
 226                  *
 227                  * After that, we're done creating paths for the joinrel, so run
 228                  * set_cheapest().
 229                  */
 230                 foreach(lc, root->join_rel_level[lev])
 231                 {
 232                         rel = (RelOptInfo *) lfirst(lc);
 233
 234                         /* Create paths for partitionwise joins. */
 235                         generate_partitionwise_join_paths(root, rel);
 236
 237                         /*
 238                          * Except for the topmost scan/join rel, consider gathering
 239                          * partial paths.  We'll do the same for the topmost scan/join rel
 240                          * once we know the final targetlist (see grouping_planner).
 241                          */
 242                         if (lev < levels_needed)
 243                                 generate_useful_gather_paths(root, rel, false);
 244
 245                         /* Find and save the cheapest paths for this rel */
 246                         set_cheapest(rel);
 247
 248 #ifdef OPTIMIZER_DEBUG
 249                         debug_print_rel(root, rel);
 250 #endif
 251                 }
 252         }
 253
 254         /*
 255          * We should have a single rel at the final level.
 256          */
 257         if (root->join_rel_level[levels_needed] == NIL)
 258                 elog(ERROR, "failed to build any %d-way joins", levels_needed);
 259         Assert(list_length(root->join_rel_level[levels_needed]) == 1);
 260
 261         rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);
 262
 263         root->join_rel_level = NULL;
 264
 265         return rel;
 266 }
 267
 268
 269 /*
 270  * create_plain_partial_paths
 271  *        Build partial access paths for parallel scan of a plain relation
 272  */
 273 static void
 274 create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
 275 {
 276         int                     parallel_workers;
 277
 278         parallel_workers = compute_parallel_worker(rel, rel->pages, -1,
 279                                                                                            max_parallel_workers_per_gather);
 280
 281         /* If any limit was set to zero, the user doesn't want a parallel scan. */
 282         if (parallel_workers <= 0)
 283                 return;
 284
 285         /* Add an unordered partial path based on a parallel sequential scan. */
 286         add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_workers));
 287 }
 288
 289
 290 /*
 291  * join_search_one_level
 292  *        Consider ways to produce join relations containing exactly 'level'
 293  *        jointree items.  (This is one step of the dynamic-programming method
 294  *        embodied in standard_join_search.)  Join rel nodes for each feasible
 295  *        combination of lower-level rels are created and returned in a list.
 296  *        Implementation paths are created for each such joinrel, too.
 297  *
 298  * level: level of rels we want to make this time
 299  * root->join_rel_level[j], 1 <= j < level, is a list of rels containing j items
 300  *
 301  * The result is returned in root->join_rel_level[level].
 302  */
 303 void
 304 join_search_one_level(PlannerInfo *root, int level)
 305 {
 306         List      **joinrels = root->join_rel_level;
 307         ListCell   *r;
 308         int                     k;
 309
 310         Assert(joinrels[level] == NIL);
 311
 312         /* Set join_cur_level so that new joinrels are added to proper list */
 313         root->join_cur_level = level;
 314
 315         /*
 316          * First, consider left-sided and right-sided plans, in which rels of
 317          * exactly level-1 member relations are joined against initial relations.
 318          * We prefer to join using join clauses, but if we find a rel of level-1
 319          * members that has no join clauses, we will generate Cartesian-product
 320          * joins against all initial rels not already contained in it.
 321          */
 322         foreach(r, joinrels[level - 1])
 323         {
 324                 RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
 325
 326                 if (old_rel->joininfo != NIL || old_rel->has_eclass_joins ||
 327                         has_join_restriction(root, old_rel))
 328                 {
 329                         /*
 330                          * There are join clauses or join order restrictions relevant to
 331                          * this rel, so consider joins between this rel and (only) those
 332                          * initial rels it is linked to by a clause or restriction.
 333                          *
 334                          * At level 2 this condition is symmetric, so there is no need to
 335                          * look at initial rels before this one in the list; we already
 336                          * considered such joins when we were at the earlier rel.  (The
 337                          * mirror-image joins are handled automatically by make_join_rel.)
 338                          * In later passes (level > 2), we join rels of the previous level
 339                          * to each initial rel they don't already include but have a join
 340                          * clause or restriction with.
 341                          */
 342                         List       *other_rels_list;
 343                         ListCell   *other_rels;
 344
 345                         if (level == 2)         /* consider remaining initial rels */
 346                         {
 347                                 other_rels_list = joinrels[level - 1];
 348                                 other_rels = lnext(other_rels_list, r);
 349                         }
 350                         else                            /* consider all initial rels */
 351                         {
 352                                 other_rels_list = joinrels[1];
 353                                 other_rels = list_head(other_rels_list);
 354                         }
 355
 356                         make_rels_by_clause_joins(root,
 357                                                                           old_rel,
 358                                                                           other_rels_list,
 359                                                                           other_rels);
 360                 }
 361                 else
 362                 {
 363                         /*
 364                          * Oops, we have a relation that is not joined to any other
 365                          * relation, either directly or by join-order restrictions.
 366                          * Cartesian product time.
 367                          *
 368                          * We consider a cartesian product with each not-already-included
 369                          * initial rel, whether it has other join clauses or not.  At
 370                          * level 2, if there are two or more clauseless initial rels, we
 371                          * will redundantly consider joining them in both directions; but
 372                          * such cases aren't common enough to justify adding complexity to
 373                          * avoid the duplicated effort.
 374                          */
 375                         make_rels_by_clauseless_joins(root,
 376                                                                                   old_rel,
 377                                                                                   joinrels[1]);
 378                 }
 379         }
 380
 381         /*
 382          * Now, consider "bushy plans" in which relations of k initial rels are
 383          * joined to relations of level-k initial rels, for 2 <= k <= level-2.
 384          *
 385          * We only consider bushy-plan joins for pairs of rels where there is a
 386          * suitable join clause (or join order restriction), in order to avoid
 387          * unreasonable growth of planning time.
 388          */
 389         for (k = 2;; k++)
 390         {
 391                 int                     other_level = level - k;
 392
 393                 /*
 394                  * Since make_join_rel(x, y) handles both x,y and y,x cases, we only
 395                  * need to go as far as the halfway point.
 396                  */
 397                 if (k > other_level)
 398                         break;
 399
 400                 foreach(r, joinrels[k])
 401                 {
 402                         RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
 403                         List       *other_rels_list;
 404                         ListCell   *other_rels;
 405                         ListCell   *r2;
 406
 407                         /*
 408                          * We can ignore relations without join clauses here, unless they
 409                          * participate in join-order restrictions --- then we might have
 410                          * to force a bushy join plan.
 411                          */
 412                         if (old_rel->joininfo == NIL && !old_rel->has_eclass_joins &&
 413                                 !has_join_restriction(root, old_rel))
 414                                 continue;
 415
 416                         if (k == other_level)
 417                         {
 418                                 /* only consider remaining rels */
 419                                 other_rels_list = joinrels[k];
 420                                 other_rels = lnext(other_rels_list, r);
 421                         }
 422                         else
 423                         {
 424                                 other_rels_list = joinrels[other_level];
 425                                 other_rels = list_head(other_rels_list);
 426                         }
 427
 428                         for_each_cell(r2, other_rels_list, other_rels)
 429                         {
 430                                 RelOptInfo *new_rel = (RelOptInfo *) lfirst(r2);
 431
 432                                 if (!bms_overlap(old_rel->relids, new_rel->relids))
 433                                 {
 434                                         /*
 435                                          * OK, we can build a rel of the right level from this
 436                                          * pair of rels.  Do so if there is at least one relevant
 437                                          * join clause or join order restriction.
 438                                          */
 439                                         if (have_relevant_joinclause(root, old_rel, new_rel) ||
 440                                                 have_join_order_restriction(root, old_rel, new_rel))
 441                                         {
 442                                                 (void) make_join_rel(root, old_rel, new_rel);
 443                                         }
 444                                 }
 445                         }
 446                 }
 447         }
 448
 449         /*----------
 450          * Last-ditch effort: if we failed to find any usable joins so far, force
 451          * a set of cartesian-product joins to be generated.  This handles the
 452          * special case where all the available rels have join clauses but we
 453          * cannot use any of those clauses yet.  This can only happen when we are
 454          * considering a join sub-problem (a sub-joinlist) and all the rels in the
 455          * sub-problem have only join clauses with rels outside the sub-problem.
 456          * An example is
 457          *
 458          *              SELECT ... FROM a INNER JOIN b ON TRUE, c, d, ...
 459          *              WHERE a.w = c.x and b.y = d.z;
 460          *
 461          * If the "a INNER JOIN b" sub-problem does not get flattened into the
 462          * upper level, we must be willing to make a cartesian join of a and b;
 463          * but the code above will not have done so, because it thought that both
 464          * a and b have joinclauses.  We consider only left-sided and right-sided
 465          * cartesian joins in this case (no bushy).
 466          *----------
 467          */
 468         if (joinrels[level] == NIL)
 469         {
 470                 /*
 471                  * This loop is just like the first one, except we always call
 472                  * make_rels_by_clauseless_joins().
 473                  */
 474                 foreach(r, joinrels[level - 1])
 475                 {
 476                         RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
 477
 478                         make_rels_by_clauseless_joins(root,
 479                                                                                   old_rel,
 480                                                                                   joinrels[1]);
 481                 }
 482
 483                 /*----------
 484                  * When special joins are involved, there may be no legal way
 485                  * to make an N-way join for some values of N.  For example consider
 486                  *
 487                  * SELECT ... FROM t1 WHERE
 488                  *       x IN (SELECT ... FROM t2,t3 WHERE ...) AND
 489                  *       y IN (SELECT ... FROM t4,t5 WHERE ...)
 490                  *
 491                  * We will flatten this query to a 5-way join problem, but there are
 492                  * no 4-way joins that join_is_legal() will consider legal.  We have
 493                  * to accept failure at level 4 and go on to discover a workable
 494                  * bushy plan at level 5.
 495                  *
 496                  * However, if there are no special joins and no lateral references
 497                  * then join_is_legal() should never fail, and so the following sanity
 498                  * check is useful.
 499                  *----------
 500                  */
 501                 if (joinrels[level] == NIL &&
 502                         root->join_info_list == NIL &&
 503                         !root->hasLateralRTEs)
 504                         elog(ERROR, "failed to build any %d-way joins", level);
 505         }
 506 }
 507
 508
 509 /*
 510  * make_rels_by_clause_joins
 511  *        Build joins between the given relation 'old_rel' and other relations
 512  *        that participate in join clauses that 'old_rel' also participates in
 513  *        (or participate in join-order restrictions with it).
 514  *        The join rels are returned in root->join_rel_level[join_cur_level].
 515  *
 516  * Note: at levels above 2 we will generate the same joined relation in
 517  * multiple ways --- for example (a join b) join c is the same RelOptInfo as
 518  * (b join c) join a, though the second case will add a different set of Paths
 519  * to it.  This is the reason for using the join_rel_level mechanism, which
 520  * automatically ensures that each new joinrel is only added to the list once.
 521  *
 522  * 'old_rel' is the relation entry for the relation to be joined
 523  * 'other_rels_list': a list containing the other
 524  * rels to be considered for joining
 525  * 'other_rels': the first cell to be considered
 526  *
 527  * Currently, this is only used with initial rels in other_rels, but it
 528  * will work for joining to joinrels too.
 529  */
 530 static void
 531 make_rels_by_clause_joins(PlannerInfo *root,
 532                                                   RelOptInfo *old_rel,
 533                                                   List *other_rels_list,
 534                                                   ListCell *other_rels)
 535 {
 536         ListCell   *l;
 537
 538         for_each_cell(l, other_rels_list, other_rels)
 539         {
 540                 RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);
 541
 542                 if (!bms_overlap(old_rel->relids, other_rel->relids) &&
 543                         (have_relevant_joinclause(root, old_rel, other_rel) ||
 544                          have_join_order_restriction(root, old_rel, other_rel)))
 545                 {
 546                         (void) make_join_rel(root, old_rel, other_rel);
 547                 }
 548         }
 549 }
 550
 551
 552 /*
 553  * make_rels_by_clauseless_joins
 554  *        Given a relation 'old_rel' and a list of other relations
 555  *        'other_rels', create a join relation between 'old_rel' and each
 556  *        member of 'other_rels' that isn't already included in 'old_rel'.
 557  *        The join rels are returned in root->join_rel_level[join_cur_level].
 558  *
 559  * 'old_rel' is the relation entry for the relation to be joined
 560  * 'other_rels': a list containing the other rels to be considered for joining
 561  *
 562  * Currently, this is only used with initial rels in other_rels, but it would
 563  * work for joining to joinrels too.
 564  */
 565 static void
 566 make_rels_by_clauseless_joins(PlannerInfo *root,
 567                                                           RelOptInfo *old_rel,
 568                                                           List *other_rels)
 569 {
 570         ListCell   *l;
 571
 572         foreach(l, other_rels)
 573         {
 574                 RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);
 575
 576                 if (!bms_overlap(other_rel->relids, old_rel->relids))
 577                 {
 578                         (void) make_join_rel(root, old_rel, other_rel);
 579                 }
 580         }
 581 }
 582
 583
 584 /*
 585  * join_is_legal
 586  *         Determine whether a proposed join is legal given the query's
 587  *         join order constraints; and if it is, determine the join type.
 588  *
 589  * Caller must supply not only the two rels, but the union of their relids.
 590  * (We could simplify the API by computing joinrelids locally, but this
 591  * would be redundant work in the normal path through make_join_rel.)
 592  *
 593  * On success, *sjinfo_p is set to NULL if this is to be a plain inner join,
 594  * else it's set to point to the associated SpecialJoinInfo node.  Also,
 595  * *reversed_p is set true if the given relations need to be swapped to
 596  * match the SpecialJoinInfo node.
 597  */
 598 static bool
 599 join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
 600                           Relids joinrelids,
 601                           SpecialJoinInfo **sjinfo_p, bool *reversed_p)
 602 {
 603         SpecialJoinInfo *match_sjinfo;
 604         bool            reversed;
 605         bool            unique_ified;
 606         bool            must_be_leftjoin;
 607         ListCell   *l;
 608
 609         /*
 610          * Ensure output params are set on failure return.  This is just to
 611          * suppress uninitialized-variable warnings from overly anal compilers.
 612          */
 613         *sjinfo_p = NULL;
 614         *reversed_p = false;
 615
 616         /*
 617          * If we have any special joins, the proposed join might be illegal; and
 618          * in any case we have to determine its join type.  Scan the join info
 619          * list for matches and conflicts.
 620          */
 621         match_sjinfo = NULL;
 622         reversed = false;
 623         unique_ified = false;
 624         must_be_leftjoin = false;
 625
 626         foreach(l, root->join_info_list)
 627         {
 628                 SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
 629
 630                 /*
 631                  * This special join is not relevant unless its RHS overlaps the
 632                  * proposed join.  (Check this first as a fast path for dismissing
 633                  * most irrelevant SJs quickly.)
 634                  */
 635                 if (!bms_overlap(sjinfo->min_righthand, joinrelids))
 636                         continue;
 637
 638                 /*
 639                  * Also, not relevant if proposed join is fully contained within RHS
 640                  * (ie, we're still building up the RHS).
 641                  */
 642                 if (bms_is_subset(joinrelids, sjinfo->min_righthand))
 643                         continue;
 644
 645                 /*
 646                  * Also, not relevant if SJ is already done within either input.
 647                  */
 648                 if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
 649                         bms_is_subset(sjinfo->min_righthand, rel1->relids))
 650                         continue;
 651                 if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
 652                         bms_is_subset(sjinfo->min_righthand, rel2->relids))
 653                         continue;
 654
 655                 /*
 656                  * If it's a semijoin and we already joined the RHS to any other rels
 657                  * within either input, then we must have unique-ified the RHS at that
 658                  * point (see below).  Therefore the semijoin is no longer relevant in
 659                  * this join path.
 660                  */
 661                 if (sjinfo->jointype == JOIN_SEMI)
 662                 {
 663                         if (bms_is_subset(sjinfo->syn_righthand, rel1->relids) &&
 664                                 !bms_equal(sjinfo->syn_righthand, rel1->relids))
 665                                 continue;
 666                         if (bms_is_subset(sjinfo->syn_righthand, rel2->relids) &&
 667                                 !bms_equal(sjinfo->syn_righthand, rel2->relids))
 668                                 continue;
 669                 }
 670
 671                 /*
 672                  * If one input contains min_lefthand and the other contains
 673                  * min_righthand, then we can perform the SJ at this join.
 674                  *
 675                  * Reject if we get matches to more than one SJ; that implies we're
 676                  * considering something that's not really valid.
 677                  */
 678                 if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
 679                         bms_is_subset(sjinfo->min_righthand, rel2->relids))
 680                 {
 681                         if (match_sjinfo)
 682                                 return false;   /* invalid join path */
 683                         match_sjinfo = sjinfo;
 684                         reversed = false;
 685                 }
 686                 else if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
 687                                  bms_is_subset(sjinfo->min_righthand, rel1->relids))
 688                 {
 689                         if (match_sjinfo)
 690                                 return false;   /* invalid join path */
 691                         match_sjinfo = sjinfo;
 692                         reversed = true;
 693                 }
 694                 else if (sjinfo->jointype == JOIN_SEMI &&
 695                                  bms_equal(sjinfo->syn_righthand, rel2->relids) &&
 696                                  create_unique_path(root, rel2, rel2->cheapest_total_path,
 697                                                                         sjinfo) != NULL)
 698                 {
 699                         /*----------
 700                          * For a semijoin, we can join the RHS to anything else by
 701                          * unique-ifying the RHS (if the RHS can be unique-ified).
 702                          * We will only get here if we have the full RHS but less
 703                          * than min_lefthand on the LHS.
 704                          *
 705                          * The reason to consider such a join path is exemplified by
 706                          *      SELECT ... FROM a,b WHERE (a.x,b.y) IN (SELECT c1,c2 FROM c)
 707                          * If we insist on doing this as a semijoin we will first have
 708                          * to form the cartesian product of A*B.  But if we unique-ify
 709                          * C then the semijoin becomes a plain innerjoin and we can join
 710                          * in any order, eg C to A and then to B.  When C is much smaller
 711                          * than A and B this can be a huge win.  So we allow C to be
 712                          * joined to just A or just B here, and then make_join_rel has
 713                          * to handle the case properly.
 714                          *
 715                          * Note that actually we'll allow unique-ified C to be joined to
 716                          * some other relation D here, too.  That is legal, if usually not
 717                          * very sane, and this routine is only concerned with legality not
 718                          * with whether the join is good strategy.
 719                          *----------
 720                          */
 721                         if (match_sjinfo)
 722                                 return false;   /* invalid join path */
 723                         match_sjinfo = sjinfo;
 724                         reversed = false;
 725                         unique_ified = true;
 726                 }
 727                 else if (sjinfo->jointype == JOIN_SEMI &&
 728                                  bms_equal(sjinfo->syn_righthand, rel1->relids) &&
 729                                  create_unique_path(root, rel1, rel1->cheapest_total_path,
 730                                                                         sjinfo) != NULL)
 731                 {
 732                         /* Reversed semijoin case */
 733                         if (match_sjinfo)
 734                                 return false;   /* invalid join path */
 735                         match_sjinfo = sjinfo;
 736                         reversed = true;
 737                         unique_ified = true;
 738                 }
 739                 else
 740                 {
 741                         /*
 742                          * Otherwise, the proposed join overlaps the RHS but isn't a valid
 743                          * implementation of this SJ.  But don't panic quite yet: the RHS
 744                          * violation might have occurred previously, in one or both input
 745                          * relations, in which case we must have previously decided that
 746                          * it was OK to commute some other SJ with this one.  If we need
 747                          * to perform this join to finish building up the RHS, rejecting
 748                          * it could lead to not finding any plan at all.  (This can occur
 749                          * because of the heuristics elsewhere in this file that postpone
 750                          * clauseless joins: we might not consider doing a clauseless join
 751                          * within the RHS until after we've performed other, validly
 752                          * commutable SJs with one or both sides of the clauseless join.)
 753                          * This consideration boils down to the rule that if both inputs
 754                          * overlap the RHS, we can allow the join --- they are either
 755                          * fully within the RHS, or represent previously-allowed joins to
 756                          * rels outside it.
 757                          */
 758                         if (bms_overlap(rel1->relids, sjinfo->min_righthand) &&
 759                                 bms_overlap(rel2->relids, sjinfo->min_righthand))
 760                                 continue;               /* assume valid previous violation of RHS */
 761
 762                         /*
 763                          * The proposed join could still be legal, but only if we're
 764                          * allowed to associate it into the RHS of this SJ.  That means
 765                          * this SJ must be a LEFT join (not SEMI or ANTI, and certainly
 766                          * not FULL) and the proposed join must not overlap the LHS.
 767                          */
 768                         if (sjinfo->jointype != JOIN_LEFT ||
 769                                 bms_overlap(joinrelids, sjinfo->min_lefthand))
 770                                 return false;   /* invalid join path */
 771
 772                         /*
 773                          * To be valid, the proposed join must be a LEFT join; otherwise
 774                          * it can't associate into this SJ's RHS.  But we may not yet have
 775                          * found the SpecialJoinInfo matching the proposed join, so we
 776                          * can't test that yet.  Remember the requirement for later.
 777                          */
 778                         must_be_leftjoin = true;
 779                 }
 780         }
 781
 782         /*
 783          * Fail if violated any SJ's RHS and didn't match to a LEFT SJ: the
 784          * proposed join can't associate into an SJ's RHS.
 785          *
 786          * Also, fail if the proposed join's predicate isn't strict; we're
 787          * essentially checking to see if we can apply outer-join identity 3, and
 788          * that's a requirement.  (This check may be redundant with checks in
 789          * make_outerjoininfo, but I'm not quite sure, and it's cheap to test.)
 790          */
 791         if (must_be_leftjoin &&
 792                 (match_sjinfo == NULL ||
 793                  match_sjinfo->jointype != JOIN_LEFT ||
 794                  !match_sjinfo->lhs_strict))
 795                 return false;                   /* invalid join path */
 796
 797         /*
 798          * We also have to check for constraints imposed by LATERAL references.
 799          */
 800         if (root->hasLateralRTEs)
 801         {
 802                 bool            lateral_fwd;
 803                 bool            lateral_rev;
 804                 Relids          join_lateral_rels;
 805
 806                 /*
 807                  * The proposed rels could each contain lateral references to the
 808                  * other, in which case the join is impossible.  If there are lateral
 809                  * references in just one direction, then the join has to be done with
 810                  * a nestloop with the lateral referencer on the inside.  If the join
 811                  * matches an SJ that cannot be implemented by such a nestloop, the
 812                  * join is impossible.
 813                  *
 814                  * Also, if the lateral reference is only indirect, we should reject
 815                  * the join; whatever rel(s) the reference chain goes through must be
 816                  * joined to first.
 817                  *
 818                  * Another case that might keep us from building a valid plan is the
 819                  * implementation restriction described by have_dangerous_phv().
 820                  */
 821                 lateral_fwd = bms_overlap(rel1->relids, rel2->lateral_relids);
 822                 lateral_rev = bms_overlap(rel2->relids, rel1->lateral_relids);
 823                 if (lateral_fwd && lateral_rev)
 824                         return false;           /* have lateral refs in both directions */
 825                 if (lateral_fwd)
 826                 {
 827                         /* has to be implemented as nestloop with rel1 on left */
 828                         if (match_sjinfo &&
 829                                 (reversed ||
 830                                  unique_ified ||
 831                                  match_sjinfo->jointype == JOIN_FULL))
 832                                 return false;   /* not implementable as nestloop */
 833                         /* check there is a direct reference from rel2 to rel1 */
 834                         if (!bms_overlap(rel1->relids, rel2->direct_lateral_relids))
 835                                 return false;   /* only indirect refs, so reject */
 836                         /* check we won't have a dangerous PHV */
 837                         if (have_dangerous_phv(root, rel1->relids, rel2->lateral_relids))
 838                                 return false;   /* might be unable to handle required PHV */
 839                 }
 840                 else if (lateral_rev)
 841                 {
 842                         /* has to be implemented as nestloop with rel2 on left */
 843                         if (match_sjinfo &&
 844                                 (!reversed ||
 845                                  unique_ified ||
 846                                  match_sjinfo->jointype == JOIN_FULL))
 847                                 return false;   /* not implementable as nestloop */
 848                         /* check there is a direct reference from rel1 to rel2 */
 849                         if (!bms_overlap(rel2->relids, rel1->direct_lateral_relids))
 850                                 return false;   /* only indirect refs, so reject */
 851                         /* check we won't have a dangerous PHV */
 852                         if (have_dangerous_phv(root, rel2->relids, rel1->lateral_relids))
 853                                 return false;   /* might be unable to handle required PHV */
 854                 }
 855
 856                 /*
 857                  * LATERAL references could also cause problems later on if we accept
 858                  * this join: if the join's minimum parameterization includes any rels
 859                  * that would have to be on the inside of an outer join with this join
 860                  * rel, then it's never going to be possible to build the complete
 861                  * query using this join.  We should reject this join not only because
 862                  * it'll save work, but because if we don't, the clauseless-join
 863                  * heuristics might think that legality of this join means that some
 864                  * other join rel need not be formed, and that could lead to failure
 865                  * to find any plan at all.  We have to consider not only rels that
 866                  * are directly on the inner side of an OJ with the joinrel, but also
 867                  * ones that are indirectly so, so search to find all such rels.
 868                  */
 869                 join_lateral_rels = min_join_parameterization(root, joinrelids,
 870                                                                                                           rel1, rel2);
 871                 if (join_lateral_rels)
 872                 {
 873                         Relids          join_plus_rhs = bms_copy(joinrelids);
 874                         bool            more;
 875
 876                         do
 877                         {
 878                                 more = false;
 879                                 foreach(l, root->join_info_list)
 880                                 {
 881                                         SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
 882
 883                                         /* ignore full joins --- their ordering is predetermined */
 884                                         if (sjinfo->jointype == JOIN_FULL)
 885                                                 continue;
 886
 887                                         if (bms_overlap(sjinfo->min_lefthand, join_plus_rhs) &&
 888                                                 !bms_is_subset(sjinfo->min_righthand, join_plus_rhs))
 889                                         {
 890                                                 join_plus_rhs = bms_add_members(join_plus_rhs,
 891                                                                                                                 sjinfo->min_righthand);
 892                                                 more = true;
 893                                         }
 894                                 }
 895                         } while (more);
 896                         if (bms_overlap(join_plus_rhs, join_lateral_rels))
 897                                 return false;   /* will not be able to join to some RHS rel */
 898                 }
 899         }
 900
 901         /* Otherwise, it's a valid join */
 902         *sjinfo_p = match_sjinfo;
 903         *reversed_p = reversed;
 904         return true;
 905 }
 906
 907
 908 /*
 909  * has_join_restriction
 910  *              Detect whether the specified relation has join-order restrictions,
 911  *              due to being inside an outer join or an IN (sub-SELECT),
 912  *              or participating in any LATERAL references or multi-rel PHVs.
 913  *
 914  * Essentially, this tests whether have_join_order_restriction() could
 915  * succeed with this rel and some other one.  It's OK if we sometimes
 916  * say "true" incorrectly.  (Therefore, we don't bother with the relatively
 917  * expensive has_legal_joinclause test.)
 918  */
 919 static bool
 920 has_join_restriction(PlannerInfo *root, RelOptInfo *rel)
 921 {
 922         ListCell   *l;
 923
 924         if (rel->lateral_relids != NULL || rel->lateral_referencers != NULL)
 925                 return true;
 926
 927         foreach(l, root->placeholder_list)
 928         {
 929                 PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
 930
 931                 if (bms_is_subset(rel->relids, phinfo->ph_eval_at) &&
 932                         !bms_equal(rel->relids, phinfo->ph_eval_at))
 933                         return true;
 934         }
 935
 936         foreach(l, root->join_info_list)
 937         {
 938                 SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
 939
 940                 /* ignore full joins --- other mechanisms preserve their ordering */
 941                 if (sjinfo->jointype == JOIN_FULL)
 942                         continue;
 943
 944                 /* ignore if SJ is already contained in rel */
 945                 if (bms_is_subset(sjinfo->min_lefthand, rel->relids) &&
 946                         bms_is_subset(sjinfo->min_righthand, rel->relids))
 947                         continue;
 948
 949                 /* restricted if it overlaps LHS or RHS, but doesn't contain SJ */
 950                 if (bms_overlap(sjinfo->min_lefthand, rel->relids) ||
 951                         bms_overlap(sjinfo->min_righthand, rel->relids))
 952                         return true;
 953         }
 954
 955         return false;
 956 }
 957
 958
 959 /*
 960  * restriction_is_constant_false --- is a restrictlist just FALSE?
 961  *
 962  * In cases where a qual is provably constant FALSE, eval_const_expressions
 963  * will generally have thrown away anything that's ANDed with it.  In outer
 964  * join situations this will leave us computing cartesian products only to
 965  * decide there's no match for an outer row, which is pretty stupid.  So,
 966  * we need to detect the case.
 967  *
 968  * If only_pushed_down is true, then consider only quals that are pushed-down
 969  * from the point of view of the joinrel.
 970  */
 971 static bool
 972 restriction_is_constant_false(List *restrictlist,
 973                                                           RelOptInfo *joinrel,
 974                                                           bool only_pushed_down)
 975 {
 976         ListCell   *lc;
 977
 978         /*
 979          * Despite the above comment, the restriction list we see here might
 980          * possibly have other members besides the FALSE constant, since other
 981          * quals could get "pushed down" to the outer join level.  So we check
 982          * each member of the list.
 983          */
 984         foreach(lc, restrictlist)
 985         {
 986                 RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
 987
 988                 if (only_pushed_down && !RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
 989                         continue;
 990
 991                 if (rinfo->clause && IsA(rinfo->clause, Const))
 992                 {
 993                         Const      *con = (Const *) rinfo->clause;
 994
 995                         /* constant NULL is as good as constant FALSE for our purposes */
 996                         if (con->constisnull)
 997                                 return true;
 998                         if (!DatumGetBool(con->constvalue))
 999                                 return true;
1000                 }
1001         }
1002         return false;
1003 }
1004
1005
1006 /*
1007  * Construct the SpecialJoinInfo for a child-join by translating
1008  * SpecialJoinInfo for the join between parents. left_relids and right_relids
1009  * are the relids of left and right side of the join respectively.
1010  */
1011 static SpecialJoinInfo *
1012 build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo,
1013                                                 Relids left_relids, Relids right_relids)
1014 {
1015         SpecialJoinInfo *sjinfo = makeNode(SpecialJoinInfo);
1016         AppendRelInfo **left_appinfos;
1017         int                     left_nappinfos;
1018         AppendRelInfo **right_appinfos;
1019         int                     right_nappinfos;
1020
1021         memcpy(sjinfo, parent_sjinfo, sizeof(SpecialJoinInfo));
1022         left_appinfos = find_appinfos_by_relids(root, left_relids,
1023                                                                                         &left_nappinfos);
1024         right_appinfos = find_appinfos_by_relids(root, right_relids,
1025                                                                                          &right_nappinfos);
1026
1027         sjinfo->min_lefthand = adjust_child_relids(sjinfo->min_lefthand,
1028                                                                                            left_nappinfos, left_appinfos);
1029         sjinfo->min_righthand = adjust_child_relids(sjinfo->min_righthand,
1030                                                                                                 right_nappinfos,
1031                                                                                                 right_appinfos);
1032         sjinfo->syn_lefthand = adjust_child_relids(sjinfo->syn_lefthand,
1033                                                                                            left_nappinfos, left_appinfos);
1034         sjinfo->syn_righthand = adjust_child_relids(sjinfo->syn_righthand,
1035                                                                                                 right_nappinfos,
1036                                                                                                 right_appinfos);
1037         sjinfo->semi_rhs_exprs = (List *) adjust_appendrel_attrs(root,
1038                                                                                                                          (Node *) sjinfo->semi_rhs_exprs,
1039                                                                                                                          right_nappinfos,
1040                                                                                                                          right_appinfos);
1041
1042         pfree(left_appinfos);
1043         pfree(right_appinfos);
1044
1045         return sjinfo;
1046 }
1047
1048
1049 /*
1050  * get_matching_part_pairs
1051  *              Generate pairs of partitions to be joined from inputs
1052  */
1053 static void
1054 get_matching_part_pairs(PlannerInfo *root, RelOptInfo *joinrel,
1055                                                 RelOptInfo *rel1, RelOptInfo *rel2,
1056                                                 List **parts1, List **parts2)
1057 {
1058         bool            rel1_is_simple = IS_SIMPLE_REL(rel1);
1059         bool            rel2_is_simple = IS_SIMPLE_REL(rel2);
1060         int                     cnt_parts;
1061
1062         *parts1 = NIL;
1063         *parts2 = NIL;
1064
1065         for (cnt_parts = 0; cnt_parts < joinrel->nparts; cnt_parts++)
1066         {
1067                 RelOptInfo *child_joinrel = joinrel->part_rels[cnt_parts];
1068                 RelOptInfo *child_rel1;
1069                 RelOptInfo *child_rel2;
1070                 Relids          child_relids1;
1071                 Relids          child_relids2;
1072
1073                 /*
1074                  * If this segment of the join is empty, it means that this segment
1075                  * was ignored when previously creating child-join paths for it in
1076                  * try_partitionwise_join() as it would not contribute to the join
1077                  * result, due to one or both inputs being empty; add NULL to each of
1078                  * the given lists so that this segment will be ignored again in that
1079                  * function.
1080                  */
1081                 if (!child_joinrel)
1082                 {
1083                         *parts1 = lappend(*parts1, NULL);
1084                         *parts2 = lappend(*parts2, NULL);
1085                         continue;
1086                 }
1087
1088                 /*
1089                  * Get a relids set of partition(s) involved in this join segment that
1090                  * are from the rel1 side.
1091                  */
1092                 child_relids1 = bms_intersect(child_joinrel->relids,
1093                                                                           rel1->all_partrels);
1094                 Assert(bms_num_members(child_relids1) == bms_num_members(rel1->relids));
1095
1096                 /*
1097                  * Get a child rel for rel1 with the relids.  Note that we should have
1098                  * the child rel even if rel1 is a join rel, because in that case the
1099                  * partitions specified in the relids would have matching/overlapping
1100                  * boundaries, so the specified partitions should be considered as
1101                  * ones to be joined when planning partitionwise joins of rel1,
1102                  * meaning that the child rel would have been built by the time we get
1103                  * here.
1104                  */
1105                 if (rel1_is_simple)
1106                 {
1107                         int                     varno = bms_singleton_member(child_relids1);
1108
1109                         child_rel1 = find_base_rel(root, varno);
1110                 }
1111                 else
1112                         child_rel1 = find_join_rel(root, child_relids1);
1113                 Assert(child_rel1);
1114
1115                 /*
1116                  * Get a relids set of partition(s) involved in this join segment that
1117                  * are from the rel2 side.
1118                  */
1119                 child_relids2 = bms_intersect(child_joinrel->relids,
1120                                                                           rel2->all_partrels);
1121                 Assert(bms_num_members(child_relids2) == bms_num_members(rel2->relids));
1122
1123                 /*
1124                  * Get a child rel for rel2 with the relids.  See above comments.
1125                  */
1126                 if (rel2_is_simple)
1127                 {
1128                         int                     varno = bms_singleton_member(child_relids2);
1129
1130                         child_rel2 = find_base_rel(root, varno);
1131                 }
1132                 else
1133                         child_rel2 = find_join_rel(root, child_relids2);
1134                 Assert(child_rel2);
1135
1136                 /*
1137                  * The join of rel1 and rel2 is legal, so is the join of the child
1138                  * rels obtained above; add them to the given lists as a join pair
1139                  * producing this join segment.
1140                  */
1141                 *parts1 = lappend(*parts1, child_rel1);
1142                 *parts2 = lappend(*parts2, child_rel2);
1143         }
1144 }
1145
1146
1147 /*
1148  * compute_partition_bounds
1149  *              Compute the partition bounds for a join rel from those for inputs
1150  */
1151 static void
1152 compute_partition_bounds(PlannerInfo *root, RelOptInfo *rel1,
1153                                                  RelOptInfo *rel2, RelOptInfo *joinrel,
1154                                                  SpecialJoinInfo *parent_sjinfo,
1155                                                  List **parts1, List **parts2)
1156 {
1157         /*
1158          * If we don't have the partition bounds for the join rel yet, try to
1159          * compute those along with pairs of partitions to be joined.
1160          */
1161         if (joinrel->nparts == -1)
1162         {
1163                 PartitionScheme part_scheme = joinrel->part_scheme;
1164                 PartitionBoundInfo boundinfo = NULL;
1165                 int                     nparts = 0;
1166
1167                 Assert(joinrel->boundinfo == NULL);
1168                 Assert(joinrel->part_rels == NULL);
1169
1170                 /*
1171                  * See if the partition bounds for inputs are exactly the same, in
1172                  * which case we don't need to work hard: the join rel have the same
1173                  * partition bounds as inputs, and the partitions with the same
1174                  * cardinal positions form the pairs.
1175                  *
1176                  * Note: even in cases where one or both inputs have merged bounds, it
1177                  * would be possible for both the bounds to be exactly the same, but
1178                  * it seems unlikely to be worth the cycles to check.
1179                  */
1180                 if (!rel1->partbounds_merged &&
1181                         !rel2->partbounds_merged &&
1182                         rel1->nparts == rel2->nparts &&
1183                         partition_bounds_equal(part_scheme->partnatts,
1184                                                                    part_scheme->parttyplen,
1185                                                                    part_scheme->parttypbyval,
1186                                                                    rel1->boundinfo, rel2->boundinfo))
1187                 {
1188                         boundinfo = rel1->boundinfo;
1189                         nparts = rel1->nparts;
1190                 }
1191                 else
1192                 {
1193                         /* Try merging the partition bounds for inputs. */
1194                         boundinfo = partition_bounds_merge(part_scheme->partnatts,
1195                                                                                            part_scheme->partsupfunc,
1196                                                                                            part_scheme->partcollation,
1197                                                                                            rel1, rel2,
1198                                                                                            parent_sjinfo->jointype,
1199                                                                                            parts1, parts2);
1200                         if (boundinfo == NULL)
1201                         {
1202                                 joinrel->nparts = 0;
1203                                 return;
1204                         }
1205                         nparts = list_length(*parts1);
1206                         joinrel->partbounds_merged = true;
1207                 }
1208
1209                 Assert(nparts > 0);
1210                 joinrel->boundinfo = boundinfo;
1211                 joinrel->nparts = nparts;
1212                 joinrel->part_rels =
1213                         (RelOptInfo **) palloc0(sizeof(RelOptInfo *) * nparts);
1214         }
1215         else
1216         {
1217                 Assert(joinrel->nparts > 0);
1218                 Assert(joinrel->boundinfo);
1219                 Assert(joinrel->part_rels);
1220
1221                 /*
1222                  * If the join rel's partbounds_merged flag is true, it means inputs
1223                  * are not guaranteed to have the same partition bounds, therefore we
1224                  * can't assume that the partitions at the same cardinal positions
1225                  * form the pairs; let get_matching_part_pairs() generate the pairs.
1226                  * Otherwise, nothing to do since we can assume that.
1227                  */
1228                 if (joinrel->partbounds_merged)
1229                 {
1230                         get_matching_part_pairs(root, joinrel, rel1, rel2,
1231                                                                         parts1, parts2);
1232                         Assert(list_length(*parts1) == joinrel->nparts);
1233                         Assert(list_length(*parts2) == joinrel->nparts);
1234                 }
1235         }
1236 }
1237
1238
1239 /*
1240  * Assess whether join between given two partitioned relations can be broken
1241  * down into joins between matching partitions; a technique called
1242  * "partitionwise join"
1243  *
1244  * Partitionwise join is possible when a. Joining relations have same
1245  * partitioning scheme b. There exists an equi-join between the partition keys
1246  * of the two relations.
1247  *
1248  * Partitionwise join is planned as follows (details: optimizer/README.)
1249  *
1250  * 1. Create the RelOptInfos for joins between matching partitions i.e
1251  * child-joins and add paths to them.
1252  *
1253  * 2. Construct Append or MergeAppend paths across the set of child joins.
1254  * This second phase is implemented by generate_partitionwise_join_paths().
1255  *
1256  * The RelOptInfo, SpecialJoinInfo and restrictlist for each child join are
1257  * obtained by translating the respective parent join structures.
1258  */
1259 static void
1260 try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
1261                                            RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo,
1262                                            List *parent_restrictlist)
1263 {
1264         bool            rel1_is_simple = IS_SIMPLE_REL(rel1);
1265         bool            rel2_is_simple = IS_SIMPLE_REL(rel2);
1266         List       *parts1 = NIL;
1267         List       *parts2 = NIL;
1268         ListCell   *lcr1 = NULL;
1269         ListCell   *lcr2 = NULL;
1270         int                     cnt_parts;
1271
1272         /* Guard against stack overflow due to overly deep partition hierarchy. */
1273         check_stack_depth();
1274
1275         /* Nothing to do, if the join relation is not partitioned. */
1276         if (joinrel->part_scheme == NULL || joinrel->nparts == 0)
1277                 return;
1278
1279         /* The join relation should have consider_partitionwise_join set. */
1280         Assert(joinrel->consider_partitionwise_join);
1281
1282         /*
1283          * We can not perform partitionwise join if either of the joining
1284          * relations is not partitioned.
1285          */
1286         if (!IS_PARTITIONED_REL(rel1) || !IS_PARTITIONED_REL(rel2))
1287                 return;
1288
1289         Assert(REL_HAS_ALL_PART_PROPS(rel1) && REL_HAS_ALL_PART_PROPS(rel2));
1290
1291         /* The joining relations should have consider_partitionwise_join set. */
1292         Assert(rel1->consider_partitionwise_join &&
1293                    rel2->consider_partitionwise_join);
1294
1295         /*
1296          * The partition scheme of the join relation should match that of the
1297          * joining relations.
1298          */
1299         Assert(joinrel->part_scheme == rel1->part_scheme &&
1300                    joinrel->part_scheme == rel2->part_scheme);
1301
1302         Assert(!(joinrel->partbounds_merged && (joinrel->nparts <= 0)));
1303
1304         compute_partition_bounds(root, rel1, rel2, joinrel, parent_sjinfo,
1305                                                          &parts1, &parts2);
1306
1307         if (joinrel->partbounds_merged)
1308         {
1309                 lcr1 = list_head(parts1);
1310                 lcr2 = list_head(parts2);
1311         }
1312
1313         /*
1314          * Create child-join relations for this partitioned join, if those don't
1315          * exist. Add paths to child-joins for a pair of child relations
1316          * corresponding to the given pair of parent relations.
1317          */
1318         for (cnt_parts = 0; cnt_parts < joinrel->nparts; cnt_parts++)
1319         {
1320                 RelOptInfo *child_rel1;
1321                 RelOptInfo *child_rel2;
1322                 bool            rel1_empty;
1323                 bool            rel2_empty;
1324                 SpecialJoinInfo *child_sjinfo;
1325                 List       *child_restrictlist;
1326                 RelOptInfo *child_joinrel;
1327                 Relids          child_joinrelids;
1328                 AppendRelInfo **appinfos;
1329                 int                     nappinfos;
1330
1331                 if (joinrel->partbounds_merged)
1332                 {
1333                         child_rel1 = lfirst_node(RelOptInfo, lcr1);
1334                         child_rel2 = lfirst_node(RelOptInfo, lcr2);
1335                         lcr1 = lnext(parts1, lcr1);
1336                         lcr2 = lnext(parts2, lcr2);
1337                 }
1338                 else
1339                 {
1340                         child_rel1 = rel1->part_rels[cnt_parts];
1341                         child_rel2 = rel2->part_rels[cnt_parts];
1342                 }
1343
1344                 rel1_empty = (child_rel1 == NULL || IS_DUMMY_REL(child_rel1));
1345                 rel2_empty = (child_rel2 == NULL || IS_DUMMY_REL(child_rel2));
1346
1347                 /*
1348                  * Check for cases where we can prove that this segment of the join
1349                  * returns no rows, due to one or both inputs being empty (including
1350                  * inputs that have been pruned away entirely).  If so just ignore it.
1351                  * These rules are equivalent to populate_joinrel_with_paths's rules
1352                  * for dummy input relations.
1353                  */
1354                 switch (parent_sjinfo->jointype)
1355                 {
1356                         case JOIN_INNER:
1357                         case JOIN_SEMI:
1358                                 if (rel1_empty || rel2_empty)
1359                                         continue;       /* ignore this join segment */
1360                                 break;
1361                         case JOIN_LEFT:
1362                         case JOIN_ANTI:
1363                                 if (rel1_empty)
1364                                         continue;       /* ignore this join segment */
1365                                 break;
1366                         case JOIN_FULL:
1367                                 if (rel1_empty && rel2_empty)
1368                                         continue;       /* ignore this join segment */
1369                                 break;
1370                         default:
1371                                 /* other values not expected here */
1372                                 elog(ERROR, "unrecognized join type: %d",
1373                                          (int) parent_sjinfo->jointype);
1374                                 break;
1375                 }
1376
1377                 /*
1378                  * If a child has been pruned entirely then we can't generate paths
1379                  * for it, so we have to reject partitionwise joining unless we were
1380                  * able to eliminate this partition above.
1381                  */
1382                 if (child_rel1 == NULL || child_rel2 == NULL)
1383                 {
1384                         /*
1385                          * Mark the joinrel as unpartitioned so that later functions treat
1386                          * it correctly.
1387                          */
1388                         joinrel->nparts = 0;
1389                         return;
1390                 }
1391
1392                 /*
1393                  * If a leaf relation has consider_partitionwise_join=false, it means
1394                  * that it's a dummy relation for which we skipped setting up tlist
1395                  * expressions and adding EC members in set_append_rel_size(), so
1396                  * again we have to fail here.
1397                  */
1398                 if (rel1_is_simple && !child_rel1->consider_partitionwise_join)
1399                 {
1400                         Assert(child_rel1->reloptkind == RELOPT_OTHER_MEMBER_REL);
1401                         Assert(IS_DUMMY_REL(child_rel1));
1402                         joinrel->nparts = 0;
1403                         return;
1404                 }
1405                 if (rel2_is_simple && !child_rel2->consider_partitionwise_join)
1406                 {
1407                         Assert(child_rel2->reloptkind == RELOPT_OTHER_MEMBER_REL);
1408                         Assert(IS_DUMMY_REL(child_rel2));
1409                         joinrel->nparts = 0;
1410                         return;
1411                 }
1412
1413                 /* We should never try to join two overlapping sets of rels. */
1414                 Assert(!bms_overlap(child_rel1->relids, child_rel2->relids));
1415                 child_joinrelids = bms_union(child_rel1->relids, child_rel2->relids);
1416                 appinfos = find_appinfos_by_relids(root, child_joinrelids, &nappinfos);
1417
1418                 /*
1419                  * Construct SpecialJoinInfo from parent join relations's
1420                  * SpecialJoinInfo.
1421                  */
1422                 child_sjinfo = build_child_join_sjinfo(root, parent_sjinfo,
1423                                                                                            child_rel1->relids,
1424                                                                                            child_rel2->relids);
1425
1426                 /*
1427                  * Construct restrictions applicable to the child join from those
1428                  * applicable to the parent join.
1429                  */
1430                 child_restrictlist =
1431                         (List *) adjust_appendrel_attrs(root,
1432                                                                                         (Node *) parent_restrictlist,
1433                                                                                         nappinfos, appinfos);
1434                 pfree(appinfos);
1435
1436                 child_joinrel = joinrel->part_rels[cnt_parts];
1437                 if (!child_joinrel)
1438                 {
1439                         child_joinrel = build_child_join_rel(root, child_rel1, child_rel2,
1440                                                                                                  joinrel, child_restrictlist,
1441                                                                                                  child_sjinfo,
1442                                                                                                  child_sjinfo->jointype);
1443                         joinrel->part_rels[cnt_parts] = child_joinrel;
1444                         joinrel->all_partrels = bms_add_members(joinrel->all_partrels,
1445                                                                                                         child_joinrel->relids);
1446                 }
1447
1448                 Assert(bms_equal(child_joinrel->relids, child_joinrelids));
1449
1450                 populate_joinrel_with_paths(root, child_rel1, child_rel2,
1451                                                                         child_joinrel, child_sjinfo,
1452                                                                         child_restrictlist);
1453         }
1454 }