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allpaths.c
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1 /*-------------------------------------------------------------------------
2  *
3  * allpaths.c
4  * Routines to find possible search paths for processing a query
5  *
6  * Portions Copyright (c) 1996-2020, 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 <limits.h>
19 #include <math.h>
20 
21 #include "access/sysattr.h"
22 #include "access/tsmapi.h"
23 #include "catalog/pg_class.h"
24 #include "catalog/pg_operator.h"
25 #include "catalog/pg_proc.h"
26 #include "foreign/fdwapi.h"
27 #include "miscadmin.h"
28 #include "nodes/makefuncs.h"
29 #include "nodes/nodeFuncs.h"
30 #ifdef OPTIMIZER_DEBUG
31 #include "nodes/print.h"
32 #endif
33 #include "optimizer/appendinfo.h"
34 #include "optimizer/clauses.h"
35 #include "optimizer/cost.h"
36 #include "optimizer/geqo.h"
37 #include "optimizer/inherit.h"
38 #include "optimizer/optimizer.h"
39 #include "optimizer/pathnode.h"
40 #include "optimizer/paths.h"
41 #include "optimizer/plancat.h"
42 #include "optimizer/planner.h"
43 #include "optimizer/restrictinfo.h"
44 #include "optimizer/tlist.h"
45 #include "parser/parse_clause.h"
46 #include "parser/parsetree.h"
47 #include "partitioning/partbounds.h"
48 #include "partitioning/partprune.h"
49 #include "rewrite/rewriteManip.h"
50 #include "utils/lsyscache.h"
51 
52 
53 /* results of subquery_is_pushdown_safe */
54 typedef struct pushdown_safety_info
55 {
56  bool *unsafeColumns; /* which output columns are unsafe to use */
57  bool unsafeVolatile; /* don't push down volatile quals */
58  bool unsafeLeaky; /* don't push down leaky quals */
59 } pushdown_safety_info;
60 
61 /* These parameters are set by GUC */
62 bool enable_geqo = false; /* just in case GUC doesn't set it */
63 int geqo_threshold;
64 int min_parallel_table_scan_size;
65 int min_parallel_index_scan_size;
66 
67 /* Hook for plugins to get control in set_rel_pathlist() */
68 set_rel_pathlist_hook_type set_rel_pathlist_hook = NULL;
69 
70 /* Hook for plugins to replace standard_join_search() */
71 join_search_hook_type join_search_hook = NULL;
72 
73 
74 static void set_base_rel_consider_startup(PlannerInfo *root);
75 static void set_base_rel_sizes(PlannerInfo *root);
76 static void set_base_rel_pathlists(PlannerInfo *root);
77 static void set_rel_size(PlannerInfo *root, RelOptInfo *rel,
78  Index rti, RangeTblEntry *rte);
79 static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
80  Index rti, RangeTblEntry *rte);
81 static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
82  RangeTblEntry *rte);
83 static void create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel);
84 static void set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
85  RangeTblEntry *rte);
86 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
87  RangeTblEntry *rte);
88 static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
89  RangeTblEntry *rte);
90 static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
91  RangeTblEntry *rte);
92 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
93  RangeTblEntry *rte);
94 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
95  RangeTblEntry *rte);
96 static void set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
97  Index rti, RangeTblEntry *rte);
98 static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
99  Index rti, RangeTblEntry *rte);
100 static void generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel,
101  List *live_childrels,
102  List *all_child_pathkeys,
103  List *partitioned_rels);
104 static Path *get_cheapest_parameterized_child_path(PlannerInfo *root,
105  RelOptInfo *rel,
106  Relids required_outer);
107 static void accumulate_append_subpath(Path *path,
108  List **subpaths, List **special_subpaths);
109 static Path *get_singleton_append_subpath(Path *path);
110 static void set_dummy_rel_pathlist(RelOptInfo *rel);
111 static void set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
112  Index rti, RangeTblEntry *rte);
113 static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel,
114  RangeTblEntry *rte);
115 static void set_values_pathlist(PlannerInfo *root, RelOptInfo *rel,
116  RangeTblEntry *rte);
117 static void set_tablefunc_pathlist(PlannerInfo *root, RelOptInfo *rel,
118  RangeTblEntry *rte);
119 static void set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel,
120  RangeTblEntry *rte);
121 static void set_namedtuplestore_pathlist(PlannerInfo *root, RelOptInfo *rel,
122  RangeTblEntry *rte);
123 static void set_result_pathlist(PlannerInfo *root, RelOptInfo *rel,
124  RangeTblEntry *rte);
125 static void set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel,
126  RangeTblEntry *rte);
127 static RelOptInfo *make_rel_from_joinlist(PlannerInfo *root, List *joinlist);
128 static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery,
129  pushdown_safety_info *safetyInfo);
130 static bool recurse_pushdown_safe(Node *setOp, Query *topquery,
131  pushdown_safety_info *safetyInfo);
132 static void check_output_expressions(Query *subquery,
133  pushdown_safety_info *safetyInfo);
134 static void compare_tlist_datatypes(List *tlist, List *colTypes,
135  pushdown_safety_info *safetyInfo);
136 static bool targetIsInAllPartitionLists(TargetEntry *tle, Query *query);
137 static bool qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
138  pushdown_safety_info *safetyInfo);
139 static void subquery_push_qual(Query *subquery,
140  RangeTblEntry *rte, Index rti, Node *qual);
141 static void recurse_push_qual(Node *setOp, Query *topquery,
142  RangeTblEntry *rte, Index rti, Node *qual);
143 static void remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel);
144 
145 
146 /*
147  * make_one_rel
148  * Finds all possible access paths for executing a query, returning a
149  * single rel that represents the join of all base rels in the query.
150  */
151 RelOptInfo *
152 make_one_rel(PlannerInfo *root, List *joinlist)
153 {
154  RelOptInfo *rel;
155  Index rti;
156  double total_pages;
157 
158  /*
159  * Construct the all_baserels Relids set.
160  */
161  root->all_baserels = NULL;
162  for (rti = 1; rti < root->simple_rel_array_size; rti++)
163  {
164  RelOptInfo *brel = root->simple_rel_array[rti];
165 
166  /* there may be empty slots corresponding to non-baserel RTEs */
167  if (brel == NULL)
168  continue;
169 
170  Assert(brel->relid == rti); /* sanity check on array */
171 
172  /* ignore RTEs that are "other rels" */
173  if (brel->reloptkind != RELOPT_BASEREL)
174  continue;
175 
176  root->all_baserels = bms_add_member(root->all_baserels, brel->relid);
177  }
178 
179  /* Mark base rels as to whether we care about fast-start plans */
180  set_base_rel_consider_startup(root);
181 
182  /*
183  * Compute size estimates and consider_parallel flags for each base rel.
184  */
185  set_base_rel_sizes(root);
186 
187  /*
188  * We should now have size estimates for every actual table involved in
189  * the query, and we also know which if any have been deleted from the
190  * query by join removal, pruned by partition pruning, or eliminated by
191  * constraint exclusion. So we can now compute total_table_pages.
192  *
193  * Note that appendrels are not double-counted here, even though we don't
194  * bother to distinguish RelOptInfos for appendrel parents, because the
195  * parents will have pages = 0.
196  *
197  * XXX if a table is self-joined, we will count it once per appearance,
198  * which perhaps is the wrong thing ... but that's not completely clear,
199  * and detecting self-joins here is difficult, so ignore it for now.
200  */
201  total_pages = 0;
202  for (rti = 1; rti < root->simple_rel_array_size; rti++)
203  {
204  RelOptInfo *brel = root->simple_rel_array[rti];
205 
206  if (brel == NULL)
207  continue;
208 
209  Assert(brel->relid == rti); /* sanity check on array */
210 
211  if (IS_DUMMY_REL(brel))
212  continue;
213 
214  if (IS_SIMPLE_REL(brel))
215  total_pages += (double) brel->pages;
216  }
217  root->total_table_pages = total_pages;
218 
219  /*
220  * Generate access paths for each base rel.
221  */
222  set_base_rel_pathlists(root);
223 
224  /*
225  * Generate access paths for the entire join tree.
226  */
227  rel = make_rel_from_joinlist(root, joinlist);
228 
229  /*
230  * The result should join all and only the query's base rels.
231  */
232  Assert(bms_equal(rel->relids, root->all_baserels));
233 
234  return rel;
235 }
236 
237 /*
238  * set_base_rel_consider_startup
239  * Set the consider_[param_]startup flags for each base-relation entry.
240  *
241  * For the moment, we only deal with consider_param_startup here; because the
242  * logic for consider_startup is pretty trivial and is the same for every base
243  * relation, we just let build_simple_rel() initialize that flag correctly to
244  * start with. If that logic ever gets more complicated it would probably
245  * be better to move it here.
246  */
247 static void
248 set_base_rel_consider_startup(PlannerInfo *root)
249 {
250  /*
251  * Since parameterized paths can only be used on the inside of a nestloop
252  * join plan, there is usually little value in considering fast-start
253  * plans for them. However, for relations that are on the RHS of a SEMI
254  * or ANTI join, a fast-start plan can be useful because we're only going
255  * to care about fetching one tuple anyway.
256  *
257  * To minimize growth of planning time, we currently restrict this to
258  * cases where the RHS is a single base relation, not a join; there is no
259  * provision for consider_param_startup to get set at all on joinrels.
260  * Also we don't worry about appendrels. costsize.c's costing rules for
261  * nestloop semi/antijoins don't consider such cases either.
262  */
263  ListCell *lc;
264 
265  foreach(lc, root->join_info_list)
266  {
267  SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
268  int varno;
269 
270  if ((sjinfo->jointype == JOIN_SEMI || sjinfo->jointype == JOIN_ANTI) &&
271  bms_get_singleton_member(sjinfo->syn_righthand, &varno))
272  {
273  RelOptInfo *rel = find_base_rel(root, varno);
274 
275  rel->consider_param_startup = true;
276  }
277  }
278 }
279 
280 /*
281  * set_base_rel_sizes
282  * Set the size estimates (rows and widths) for each base-relation entry.
283  * Also determine whether to consider parallel paths for base relations.
284  *
285  * We do this in a separate pass over the base rels so that rowcount
286  * estimates are available for parameterized path generation, and also so
287  * that each rel's consider_parallel flag is set correctly before we begin to
288  * generate paths.
289  */
290 static void
291 set_base_rel_sizes(PlannerInfo *root)
292 {
293  Index rti;
294 
295  for (rti = 1; rti < root->simple_rel_array_size; rti++)
296  {
297  RelOptInfo *rel = root->simple_rel_array[rti];
298  RangeTblEntry *rte;
299 
300  /* there may be empty slots corresponding to non-baserel RTEs */
301  if (rel == NULL)
302  continue;
303 
304  Assert(rel->relid == rti); /* sanity check on array */
305 
306  /* ignore RTEs that are "other rels" */
307  if (rel->reloptkind != RELOPT_BASEREL)
308  continue;
309 
310  rte = root->simple_rte_array[rti];
311 
312  /*
313  * If parallelism is allowable for this query in general, see whether
314  * it's allowable for this rel in particular. We have to do this
315  * before set_rel_size(), because (a) if this rel is an inheritance
316  * parent, set_append_rel_size() will use and perhaps change the rel's
317  * consider_parallel flag, and (b) for some RTE types, set_rel_size()
318  * goes ahead and makes paths immediately.
319  */
320  if (root->glob->parallelModeOK)
321  set_rel_consider_parallel(root, rel, rte);
322 
323  set_rel_size(root, rel, rti, rte);
324  }
325 }
326 
327 /*
328  * set_base_rel_pathlists
329  * Finds all paths available for scanning each base-relation entry.
330  * Sequential scan and any available indices are considered.
331  * Each useful path is attached to its relation's 'pathlist' field.
332  */
333 static void
334 set_base_rel_pathlists(PlannerInfo *root)
335 {
336  Index rti;
337 
338  for (rti = 1; rti < root->simple_rel_array_size; rti++)
339  {
340  RelOptInfo *rel = root->simple_rel_array[rti];
341 
342  /* there may be empty slots corresponding to non-baserel RTEs */
343  if (rel == NULL)
344  continue;
345 
346  Assert(rel->relid == rti); /* sanity check on array */
347 
348  /* ignore RTEs that are "other rels" */
349  if (rel->reloptkind != RELOPT_BASEREL)
350  continue;
351 
352  set_rel_pathlist(root, rel, rti, root->simple_rte_array[rti]);
353  }
354 }
355 
356 /*
357  * set_rel_size
358  * Set size estimates for a base relation
359  */
360 static void
361 set_rel_size(PlannerInfo *root, RelOptInfo *rel,
362  Index rti, RangeTblEntry *rte)
363 {
364  if (rel->reloptkind == RELOPT_BASEREL &&
365  relation_excluded_by_constraints(root, rel, rte))
366  {
367  /*
368  * We proved we don't need to scan the rel via constraint exclusion,
369  * so set up a single dummy path for it. Here we only check this for
370  * regular baserels; if it's an otherrel, CE was already checked in
371  * set_append_rel_size().
372  *
373  * In this case, we go ahead and set up the relation's path right away
374  * instead of leaving it for set_rel_pathlist to do. This is because
375  * we don't have a convention for marking a rel as dummy except by
376  * assigning a dummy path to it.
377  */
378  set_dummy_rel_pathlist(rel);
379  }
380  else if (rte->inh)
381  {
382  /* It's an "append relation", process accordingly */
383  set_append_rel_size(root, rel, rti, rte);
384  }
385  else
386  {
387  switch (rel->rtekind)
388  {
389  case RTE_RELATION:
390  if (rte->relkind == RELKIND_FOREIGN_TABLE)
391  {
392  /* Foreign table */
393  set_foreign_size(root, rel, rte);
394  }
395  else if (rte->relkind == RELKIND_PARTITIONED_TABLE)
396  {
397  /*
398  * We could get here if asked to scan a partitioned table
399  * with ONLY. In that case we shouldn't scan any of the
400  * partitions, so mark it as a dummy rel.
401  */
402  set_dummy_rel_pathlist(rel);
403  }
404  else if (rte->tablesample != NULL)
405  {
406  /* Sampled relation */
407  set_tablesample_rel_size(root, rel, rte);
408  }
409  else
410  {
411  /* Plain relation */
412  set_plain_rel_size(root, rel, rte);
413  }
414  break;
415  case RTE_SUBQUERY:
416 
417  /*
418  * Subqueries don't support making a choice between
419  * parameterized and unparameterized paths, so just go ahead
420  * and build their paths immediately.
421  */
422  set_subquery_pathlist(root, rel, rti, rte);
423  break;
424  case RTE_FUNCTION:
425  set_function_size_estimates(root, rel);
426  break;
427  case RTE_TABLEFUNC:
428  set_tablefunc_size_estimates(root, rel);
429  break;
430  case RTE_VALUES:
431  set_values_size_estimates(root, rel);
432  break;
433  case RTE_CTE:
434 
435  /*
436  * CTEs don't support making a choice between parameterized
437  * and unparameterized paths, so just go ahead and build their
438  * paths immediately.
439  */
440  if (rte->self_reference)
441  set_worktable_pathlist(root, rel, rte);
442  else
443  set_cte_pathlist(root, rel, rte);
444  break;
445  case RTE_NAMEDTUPLESTORE:
446  /* Might as well just build the path immediately */
447  set_namedtuplestore_pathlist(root, rel, rte);
448  break;
449  case RTE_RESULT:
450  /* Might as well just build the path immediately */
451  set_result_pathlist(root, rel, rte);
452  break;
453  default:
454  elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
455  break;
456  }
457  }
458 
459  /*
460  * We insist that all non-dummy rels have a nonzero rowcount estimate.
461  */
462  Assert(rel->rows > 0 || IS_DUMMY_REL(rel));
463 }
464 
465 /*
466  * set_rel_pathlist
467  * Build access paths for a base relation
468  */
469 static void
470 set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
471  Index rti, RangeTblEntry *rte)
472 {
473  if (IS_DUMMY_REL(rel))
474  {
475  /* We already proved the relation empty, so nothing more to do */
476  }
477  else if (rte->inh)
478  {
479  /* It's an "append relation", process accordingly */
480  set_append_rel_pathlist(root, rel, rti, rte);
481  }
482  else
483  {
484  switch (rel->rtekind)
485  {
486  case RTE_RELATION:
487  if (rte->relkind == RELKIND_FOREIGN_TABLE)
488  {
489  /* Foreign table */
490  set_foreign_pathlist(root, rel, rte);
491  }
492  else if (rte->tablesample != NULL)
493  {
494  /* Sampled relation */
495  set_tablesample_rel_pathlist(root, rel, rte);
496  }
497  else
498  {
499  /* Plain relation */
500  set_plain_rel_pathlist(root, rel, rte);
501  }
502  break;
503  case RTE_SUBQUERY:
504  /* Subquery --- fully handled during set_rel_size */
505  break;
506  case RTE_FUNCTION:
507  /* RangeFunction */
508  set_function_pathlist(root, rel, rte);
509  break;
510  case RTE_TABLEFUNC:
511  /* Table Function */
512  set_tablefunc_pathlist(root, rel, rte);
513  break;
514  case RTE_VALUES:
515  /* Values list */
516  set_values_pathlist(root, rel, rte);
517  break;
518  case RTE_CTE:
519  /* CTE reference --- fully handled during set_rel_size */
520  break;
521  case RTE_NAMEDTUPLESTORE:
522  /* tuplestore reference --- fully handled during set_rel_size */
523  break;
524  case RTE_RESULT:
525  /* simple Result --- fully handled during set_rel_size */
526  break;
527  default:
528  elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
529  break;
530  }
531  }
532 
533  /*
534  * Allow a plugin to editorialize on the set of Paths for this base
535  * relation. It could add new paths (such as CustomPaths) by calling
536  * add_path(), or add_partial_path() if parallel aware. It could also
537  * delete or modify paths added by the core code.
538  */
539  if (set_rel_pathlist_hook)
540  (*set_rel_pathlist_hook) (root, rel, rti, rte);
541 
542  /*
543  * If this is a baserel, we should normally consider gathering any partial
544  * paths we may have created for it. We have to do this after calling the
545  * set_rel_pathlist_hook, else it cannot add partial paths to be included
546  * here.
547  *
548  * However, if this is an inheritance child, skip it. Otherwise, we could
549  * end up with a very large number of gather nodes, each trying to grab
550  * its own pool of workers. Instead, we'll consider gathering partial
551  * paths for the parent appendrel.
552  *
553  * Also, if this is the topmost scan/join rel (that is, the only baserel),
554  * we postpone gathering until the final scan/join targetlist is available
555  * (see grouping_planner).
556  */
557  if (rel->reloptkind == RELOPT_BASEREL &&
558  bms_membership(root->all_baserels) != BMS_SINGLETON)
559  generate_useful_gather_paths(root, rel, false);
560 
561  /* Now find the cheapest of the paths for this rel */
562  set_cheapest(rel);
563 
564 #ifdef OPTIMIZER_DEBUG
565  debug_print_rel(root, rel);
566 #endif
567 }
568 
569 /*
570  * set_plain_rel_size
571  * Set size estimates for a plain relation (no subquery, no inheritance)
572  */
573 static void
574 set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
575 {
576  /*
577  * Test any partial indexes of rel for applicability. We must do this
578  * first since partial unique indexes can affect size estimates.
579  */
580  check_index_predicates(root, rel);
581 
582  /* Mark rel with estimated output rows, width, etc */
583  set_baserel_size_estimates(root, rel);
584 }
585 
586 /*
587  * If this relation could possibly be scanned from within a worker, then set
588  * its consider_parallel flag.
589  */
590 static void
591 set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
592  RangeTblEntry *rte)
593 {
594  /*
595  * The flag has previously been initialized to false, so we can just
596  * return if it becomes clear that we can't safely set it.
597  */
598  Assert(!rel->consider_parallel);
599 
600  /* Don't call this if parallelism is disallowed for the entire query. */
601  Assert(root->glob->parallelModeOK);
602 
603  /* This should only be called for baserels and appendrel children. */
604  Assert(IS_SIMPLE_REL(rel));
605 
606  /* Assorted checks based on rtekind. */
607  switch (rte->rtekind)
608  {
609  case RTE_RELATION:
610 
611  /*
612  * Currently, parallel workers can't access the leader's temporary
613  * tables. We could possibly relax this if we wrote all of its
614  * local buffers at the start of the query and made no changes
615  * thereafter (maybe we could allow hint bit changes), and if we
616  * taught the workers to read them. Writing a large number of
617  * temporary buffers could be expensive, though, and we don't have
618  * the rest of the necessary infrastructure right now anyway. So
619  * for now, bail out if we see a temporary table.
620  */
621  if (get_rel_persistence(rte->relid) == RELPERSISTENCE_TEMP)
622  return;
623 
624  /*
625  * Table sampling can be pushed down to workers if the sample
626  * function and its arguments are safe.
627  */
628  if (rte->tablesample != NULL)
629  {
630  char proparallel = func_parallel(rte->tablesample->tsmhandler);
631 
632  if (proparallel != PROPARALLEL_SAFE)
633  return;
634  if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
635  return;
636  }
637 
638  /*
639  * Ask FDWs whether they can support performing a ForeignScan
640  * within a worker. Most often, the answer will be no. For
641  * example, if the nature of the FDW is such that it opens a TCP
642  * connection with a remote server, each parallel worker would end
643  * up with a separate connection, and these connections might not
644  * be appropriately coordinated between workers and the leader.
645  */
646  if (rte->relkind == RELKIND_FOREIGN_TABLE)
647  {
648  Assert(rel->fdwroutine);
649  if (!rel->fdwroutine->IsForeignScanParallelSafe)
650  return;
651  if (!rel->fdwroutine->IsForeignScanParallelSafe(root, rel, rte))
652  return;
653  }
654 
655  /*
656  * There are additional considerations for appendrels, which we'll
657  * deal with in set_append_rel_size and set_append_rel_pathlist.
658  * For now, just set consider_parallel based on the rel's own
659  * quals and targetlist.
660  */
661  break;
662 
663  case RTE_SUBQUERY:
664 
665  /*
666  * There's no intrinsic problem with scanning a subquery-in-FROM
667  * (as distinct from a SubPlan or InitPlan) in a parallel worker.
668  * If the subquery doesn't happen to have any parallel-safe paths,
669  * then flagging it as consider_parallel won't change anything,
670  * but that's true for plain tables, too. We must set
671  * consider_parallel based on the rel's own quals and targetlist,
672  * so that if a subquery path is parallel-safe but the quals and
673  * projection we're sticking onto it are not, we correctly mark
674  * the SubqueryScanPath as not parallel-safe. (Note that
675  * set_subquery_pathlist() might push some of these quals down
676  * into the subquery itself, but that doesn't change anything.)
677  *
678  * We can't push sub-select containing LIMIT/OFFSET to workers as
679  * there is no guarantee that the row order will be fully
680  * deterministic, and applying LIMIT/OFFSET will lead to
681  * inconsistent results at the top-level. (In some cases, where
682  * the result is ordered, we could relax this restriction. But it
683  * doesn't currently seem worth expending extra effort to do so.)
684  */
685  {
686  Query *subquery = castNode(Query, rte->subquery);
687 
688  if (limit_needed(subquery))
689  return;
690  }
691  break;
692 
693  case RTE_JOIN:
694  /* Shouldn't happen; we're only considering baserels here. */
695  Assert(false);
696  return;
697 
698  case RTE_FUNCTION:
699  /* Check for parallel-restricted functions. */
700  if (!is_parallel_safe(root, (Node *) rte->functions))
701  return;
702  break;
703 
704  case RTE_TABLEFUNC:
705  /* not parallel safe */
706  return;
707 
708  case RTE_VALUES:
709  /* Check for parallel-restricted functions. */
710  if (!is_parallel_safe(root, (Node *) rte->values_lists))
711  return;
712  break;
713 
714  case RTE_CTE:
715 
716  /*
717  * CTE tuplestores aren't shared among parallel workers, so we
718  * force all CTE scans to happen in the leader. Also, populating
719  * the CTE would require executing a subplan that's not available
720  * in the worker, might be parallel-restricted, and must get
721  * executed only once.
722  */
723  return;
724 
725  case RTE_NAMEDTUPLESTORE:
726 
727  /*
728  * tuplestore cannot be shared, at least without more
729  * infrastructure to support that.
730  */
731  return;
732 
733  case RTE_RESULT:
734  /* RESULT RTEs, in themselves, are no problem. */
735  break;
736  }
737 
738  /*
739  * If there's anything in baserestrictinfo that's parallel-restricted, we
740  * give up on parallelizing access to this relation. We could consider
741  * instead postponing application of the restricted quals until we're
742  * above all the parallelism in the plan tree, but it's not clear that
743  * that would be a win in very many cases, and it might be tricky to make
744  * outer join clauses work correctly. It would likely break equivalence
745  * classes, too.
746  */
747  if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
748  return;
749 
750  /*
751  * Likewise, if the relation's outputs are not parallel-safe, give up.
752  * (Usually, they're just Vars, but sometimes they're not.)
753  */
754  if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
755  return;
756 
757  /* We have a winner. */
758  rel->consider_parallel = true;
759 }
760 
761 /*
762  * set_plain_rel_pathlist
763  * Build access paths for a plain relation (no subquery, no inheritance)
764  */
765 static void
766 set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
767 {
768  Relids required_outer;
769 
770  /*
771  * We don't support pushing join clauses into the quals of a seqscan, but
772  * it could still have required parameterization due to LATERAL refs in
773  * its tlist.
774  */
775  required_outer = rel->lateral_relids;
776 
777  /* Consider sequential scan */
778  add_path(rel, create_seqscan_path(root, rel, required_outer, 0));
779 
780  /* If appropriate, consider parallel sequential scan */
781  if (rel->consider_parallel && required_outer == NULL)
782  create_plain_partial_paths(root, rel);
783 
784  /* Consider index scans */
785  create_index_paths(root, rel);
786 
787  /* Consider TID scans */
788  create_tidscan_paths(root, rel);
789 }
790 
791 /*
792  * create_plain_partial_paths
793  * Build partial access paths for parallel scan of a plain relation
794  */
795 static void
796 create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
797 {
798  int parallel_workers;
799 
800  parallel_workers = compute_parallel_worker(rel, rel->pages, -1,
801  max_parallel_workers_per_gather);
802 
803  /* If any limit was set to zero, the user doesn't want a parallel scan. */
804  if (parallel_workers <= 0)
805  return;
806 
807  /* Add an unordered partial path based on a parallel sequential scan. */
808  add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_workers));
809 }
810 
811 /*
812  * set_tablesample_rel_size
813  * Set size estimates for a sampled relation
814  */
815 static void
816 set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
817 {
818  TableSampleClause *tsc = rte->tablesample;
819  TsmRoutine *tsm;
820  BlockNumber pages;
821  double tuples;
822 
823  /*
824  * Test any partial indexes of rel for applicability. We must do this
825  * first since partial unique indexes can affect size estimates.
826  */
827  check_index_predicates(root, rel);
828 
829  /*
830  * Call the sampling method's estimation function to estimate the number
831  * of pages it will read and the number of tuples it will return. (Note:
832  * we assume the function returns sane values.)
833  */
834  tsm = GetTsmRoutine(tsc->tsmhandler);
835  tsm->SampleScanGetSampleSize(root, rel, tsc->args,
836  &pages, &tuples);
837 
838  /*
839  * For the moment, because we will only consider a SampleScan path for the
840  * rel, it's okay to just overwrite the pages and tuples estimates for the
841  * whole relation. If we ever consider multiple path types for sampled
842  * rels, we'll need more complication.
843  */
844  rel->pages = pages;
845  rel->tuples = tuples;
846 
847  /* Mark rel with estimated output rows, width, etc */
848  set_baserel_size_estimates(root, rel);
849 }
850 
851 /*
852  * set_tablesample_rel_pathlist
853  * Build access paths for a sampled relation
854  */
855 static void
856 set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
857 {
858  Relids required_outer;
859  Path *path;
860 
861  /*
862  * We don't support pushing join clauses into the quals of a samplescan,
863  * but it could still have required parameterization due to LATERAL refs
864  * in its tlist or TABLESAMPLE arguments.
865  */
866  required_outer = rel->lateral_relids;
867 
868  /* Consider sampled scan */
869  path = create_samplescan_path(root, rel, required_outer);
870 
871  /*
872  * If the sampling method does not support repeatable scans, we must avoid
873  * plans that would scan the rel multiple times. Ideally, we'd simply
874  * avoid putting the rel on the inside of a nestloop join; but adding such
875  * a consideration to the planner seems like a great deal of complication
876  * to support an uncommon usage of second-rate sampling methods. Instead,
877  * if there is a risk that the query might perform an unsafe join, just
878  * wrap the SampleScan in a Materialize node. We can check for joins by
879  * counting the membership of all_baserels (note that this correctly
880  * counts inheritance trees as single rels). If we're inside a subquery,
881  * we can't easily check whether a join might occur in the outer query, so
882  * just assume one is possible.
883  *
884  * GetTsmRoutine is relatively expensive compared to the other tests here,
885  * so check repeatable_across_scans last, even though that's a bit odd.
886  */
887  if ((root->query_level > 1 ||
888  bms_membership(root->all_baserels) != BMS_SINGLETON) &&
889  !(GetTsmRoutine(rte->tablesample->tsmhandler)->repeatable_across_scans))
890  {
891  path = (Path *) create_material_path(rel, path);
892  }
893 
894  add_path(rel, path);
895 
896  /* For the moment, at least, there are no other paths to consider */
897 }
898 
899 /*
900  * set_foreign_size
901  * Set size estimates for a foreign table RTE
902  */
903 static void
904 set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
905 {
906  /* Mark rel with estimated output rows, width, etc */
907  set_foreign_size_estimates(root, rel);
908 
909  /* Let FDW adjust the size estimates, if it can */
910  rel->fdwroutine->GetForeignRelSize(root, rel, rte->relid);
911 
912  /* ... but do not let it set the rows estimate to zero */
913  rel->rows = clamp_row_est(rel->rows);
914 
915  /* also, make sure rel->tuples is not insane relative to rel->rows */
916  rel->tuples = Max(rel->tuples, rel->rows);
917 }
918 
919 /*
920  * set_foreign_pathlist
921  * Build access paths for a foreign table RTE
922  */
923 static void
924 set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
925 {
926  /* Call the FDW's GetForeignPaths function to generate path(s) */
927  rel->fdwroutine->GetForeignPaths(root, rel, rte->relid);
928 }
929 
930 /*
931  * set_append_rel_size
932  * Set size estimates for a simple "append relation"
933  *
934  * The passed-in rel and RTE represent the entire append relation. The
935  * relation's contents are computed by appending together the output of the
936  * individual member relations. Note that in the non-partitioned inheritance
937  * case, the first member relation is actually the same table as is mentioned
938  * in the parent RTE ... but it has a different RTE and RelOptInfo. This is
939  * a good thing because their outputs are not the same size.
940  */
941 static void
942 set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
943  Index rti, RangeTblEntry *rte)
944 {
945  int parentRTindex = rti;
946  bool has_live_children;
947  double parent_rows;
948  double parent_size;
949  double *parent_attrsizes;
950  int nattrs;
951  ListCell *l;
952 
953  /* Guard against stack overflow due to overly deep inheritance tree. */
954  check_stack_depth();
955 
956  Assert(IS_SIMPLE_REL(rel));
957 
958  /*
959  * Initialize partitioned_child_rels to contain this RT index.
960  *
961  * Note that during the set_append_rel_pathlist() phase, we will bubble up
962  * the indexes of partitioned relations that appear down in the tree, so
963  * that when we've created Paths for all the children, the root
964  * partitioned table's list will contain all such indexes.
965  */
966  if (rte->relkind == RELKIND_PARTITIONED_TABLE)
967  rel->partitioned_child_rels = list_make1_int(rti);
968 
969  /*
970  * If this is a partitioned baserel, set the consider_partitionwise_join
971  * flag; currently, we only consider partitionwise joins with the baserel
972  * if its targetlist doesn't contain a whole-row Var.
973  */
974  if (enable_partitionwise_join &&
975  rel->reloptkind == RELOPT_BASEREL &&
976  rte->relkind == RELKIND_PARTITIONED_TABLE &&
977  rel->attr_needed[InvalidAttrNumber - rel->min_attr] == NULL)
978  rel->consider_partitionwise_join = true;
979 
980  /*
981  * Initialize to compute size estimates for whole append relation.
982  *
983  * We handle width estimates by weighting the widths of different child
984  * rels proportionally to their number of rows. This is sensible because
985  * the use of width estimates is mainly to compute the total relation
986  * "footprint" if we have to sort or hash it. To do this, we sum the
987  * total equivalent size (in "double" arithmetic) and then divide by the
988  * total rowcount estimate. This is done separately for the total rel
989  * width and each attribute.
990  *
991  * Note: if you consider changing this logic, beware that child rels could
992  * have zero rows and/or width, if they were excluded by constraints.
993  */
994  has_live_children = false;
995  parent_rows = 0;
996  parent_size = 0;
997  nattrs = rel->max_attr - rel->min_attr + 1;
998  parent_attrsizes = (double *) palloc0(nattrs * sizeof(double));
999 
1000  foreach(l, root->append_rel_list)
1001  {
1002  AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
1003  int childRTindex;
1004  RangeTblEntry *childRTE;
1005  RelOptInfo *childrel;
1006  ListCell *parentvars;
1007  ListCell *childvars;
1008 
1009  /* append_rel_list contains all append rels; ignore others */
1010  if (appinfo->parent_relid != parentRTindex)
1011  continue;
1012 
1013  childRTindex = appinfo->child_relid;
1014  childRTE = root->simple_rte_array[childRTindex];
1015 
1016  /*
1017  * The child rel's RelOptInfo was already created during
1018  * add_other_rels_to_query.
1019  */
1020  childrel = find_base_rel(root, childRTindex);
1021  Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
1022 
1023  /* We may have already proven the child to be dummy. */
1024  if (IS_DUMMY_REL(childrel))
1025  continue;
1026 
1027  /*
1028  * We have to copy the parent's targetlist and quals to the child,
1029  * with appropriate substitution of variables. However, the
1030  * baserestrictinfo quals were already copied/substituted when the
1031  * child RelOptInfo was built. So we don't need any additional setup
1032  * before applying constraint exclusion.
1033  */
1034  if (relation_excluded_by_constraints(root, childrel, childRTE))
1035  {
1036  /*
1037  * This child need not be scanned, so we can omit it from the
1038  * appendrel.
1039  */
1040  set_dummy_rel_pathlist(childrel);
1041  continue;
1042  }
1043 
1044  /*
1045  * Constraint exclusion failed, so copy the parent's join quals and
1046  * targetlist to the child, with appropriate variable substitutions.
1047  *
1048  * NB: the resulting childrel->reltarget->exprs may contain arbitrary
1049  * expressions, which otherwise would not occur in a rel's targetlist.
1050  * Code that might be looking at an appendrel child must cope with
1051  * such. (Normally, a rel's targetlist would only include Vars and
1052  * PlaceHolderVars.) XXX we do not bother to update the cost or width
1053  * fields of childrel->reltarget; not clear if that would be useful.
1054  */
1055  childrel->joininfo = (List *)
1056  adjust_appendrel_attrs(root,
1057  (Node *) rel->joininfo,
1058  1, &appinfo);
1059  childrel->reltarget->exprs = (List *)
1060  adjust_appendrel_attrs(root,
1061  (Node *) rel->reltarget->exprs,
1062  1, &appinfo);
1063 
1064  /*
1065  * We have to make child entries in the EquivalenceClass data
1066  * structures as well. This is needed either if the parent
1067  * participates in some eclass joins (because we will want to consider
1068  * inner-indexscan joins on the individual children) or if the parent
1069  * has useful pathkeys (because we should try to build MergeAppend
1070  * paths that produce those sort orderings).
1071  */
1072  if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
1073  add_child_rel_equivalences(root, appinfo, rel, childrel);
1074  childrel->has_eclass_joins = rel->has_eclass_joins;
1075 
1076  /*
1077  * Note: we could compute appropriate attr_needed data for the child's
1078  * variables, by transforming the parent's attr_needed through the
1079  * translated_vars mapping. However, currently there's no need
1080  * because attr_needed is only examined for base relations not
1081  * otherrels. So we just leave the child's attr_needed empty.
1082  */
1083 
1084  /*
1085  * If we consider partitionwise joins with the parent rel, do the same
1086  * for partitioned child rels.
1087  *
1088  * Note: here we abuse the consider_partitionwise_join flag by setting
1089  * it for child rels that are not themselves partitioned. We do so to
1090  * tell try_partitionwise_join() that the child rel is sufficiently
1091  * valid to be used as a per-partition input, even if it later gets
1092  * proven to be dummy. (It's not usable until we've set up the
1093  * reltarget and EC entries, which we just did.)
1094  */
1095  if (rel->consider_partitionwise_join)
1096  childrel->consider_partitionwise_join = true;
1097 
1098  /*
1099  * If parallelism is allowable for this query in general, see whether
1100  * it's allowable for this childrel in particular. But if we've
1101  * already decided the appendrel is not parallel-safe as a whole,
1102  * there's no point in considering parallelism for this child. For
1103  * consistency, do this before calling set_rel_size() for the child.
1104  */
1105  if (root->glob->parallelModeOK && rel->consider_parallel)
1106  set_rel_consider_parallel(root, childrel, childRTE);
1107 
1108  /*
1109  * Compute the child's size.
1110  */
1111  set_rel_size(root, childrel, childRTindex, childRTE);
1112 
1113  /*
1114  * It is possible that constraint exclusion detected a contradiction
1115  * within a child subquery, even though we didn't prove one above. If
1116  * so, we can skip this child.
1117  */
1118  if (IS_DUMMY_REL(childrel))
1119  continue;
1120 
1121  /* We have at least one live child. */
1122  has_live_children = true;
1123 
1124  /*
1125  * If any live child is not parallel-safe, treat the whole appendrel
1126  * as not parallel-safe. In future we might be able to generate plans
1127  * in which some children are farmed out to workers while others are
1128  * not; but we don't have that today, so it's a waste to consider
1129  * partial paths anywhere in the appendrel unless it's all safe.
1130  * (Child rels visited before this one will be unmarked in
1131  * set_append_rel_pathlist().)
1132  */
1133  if (!childrel->consider_parallel)
1134  rel->consider_parallel = false;
1135 
1136  /*
1137  * Accumulate size information from each live child.
1138  */
1139  Assert(childrel->rows > 0);
1140 
1141  parent_rows += childrel->rows;
1142  parent_size += childrel->reltarget->width * childrel->rows;
1143 
1144  /*
1145  * Accumulate per-column estimates too. We need not do anything for
1146  * PlaceHolderVars in the parent list. If child expression isn't a
1147  * Var, or we didn't record a width estimate for it, we have to fall
1148  * back on a datatype-based estimate.
1149  *
1150  * By construction, child's targetlist is 1-to-1 with parent's.
1151  */
1152  forboth(parentvars, rel->reltarget->exprs,
1153  childvars, childrel->reltarget->exprs)
1154  {
1155  Var *parentvar = (Var *) lfirst(parentvars);
1156  Node *childvar = (Node *) lfirst(childvars);
1157 
1158  if (IsA(parentvar, Var))
1159  {
1160  int pndx = parentvar->varattno - rel->min_attr;
1161  int32 child_width = 0;
1162 
1163  if (IsA(childvar, Var) &&
1164  ((Var *) childvar)->varno == childrel->relid)
1165  {
1166  int cndx = ((Var *) childvar)->varattno - childrel->min_attr;
1167 
1168  child_width = childrel->attr_widths[cndx];
1169  }
1170  if (child_width <= 0)
1171  child_width = get_typavgwidth(exprType(childvar),
1172  exprTypmod(childvar));
1173  Assert(child_width > 0);
1174  parent_attrsizes[pndx] += child_width * childrel->rows;
1175  }
1176  }
1177  }
1178 
1179  if (has_live_children)
1180  {
1181  /*
1182  * Save the finished size estimates.
1183  */
1184  int i;
1185 
1186  Assert(parent_rows > 0);
1187  rel->rows = parent_rows;
1188  rel->reltarget->width = rint(parent_size / parent_rows);
1189  for (i = 0; i < nattrs; i++)
1190  rel->attr_widths[i] = rint(parent_attrsizes[i] / parent_rows);
1191 
1192  /*
1193  * Set "raw tuples" count equal to "rows" for the appendrel; needed
1194  * because some places assume rel->tuples is valid for any baserel.
1195  */
1196  rel->tuples = parent_rows;
1197 
1198  /*
1199  * Note that we leave rel->pages as zero; this is important to avoid
1200  * double-counting the appendrel tree in total_table_pages.
1201  */
1202  }
1203  else
1204  {
1205  /*
1206  * All children were excluded by constraints, so mark the whole
1207  * appendrel dummy. We must do this in this phase so that the rel's
1208  * dummy-ness is visible when we generate paths for other rels.
1209  */
1210  set_dummy_rel_pathlist(rel);
1211  }
1212 
1213  pfree(parent_attrsizes);
1214 }
1215 
1216 /*
1217  * set_append_rel_pathlist
1218  * Build access paths for an "append relation"
1219  */
1220 static void
1221 set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
1222  Index rti, RangeTblEntry *rte)
1223 {
1224  int parentRTindex = rti;
1225  List *live_childrels = NIL;
1226  ListCell *l;
1227 
1228  /*
1229  * Generate access paths for each member relation, and remember the
1230  * non-dummy children.
1231  */
1232  foreach(l, root->append_rel_list)
1233  {
1234  AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
1235  int childRTindex;
1236  RangeTblEntry *childRTE;
1237  RelOptInfo *childrel;
1238 
1239  /* append_rel_list contains all append rels; ignore others */
1240  if (appinfo->parent_relid != parentRTindex)
1241  continue;
1242 
1243  /* Re-locate the child RTE and RelOptInfo */
1244  childRTindex = appinfo->child_relid;
1245  childRTE = root->simple_rte_array[childRTindex];
1246  childrel = root->simple_rel_array[childRTindex];
1247 
1248  /*
1249  * If set_append_rel_size() decided the parent appendrel was
1250  * parallel-unsafe at some point after visiting this child rel, we
1251  * need to propagate the unsafety marking down to the child, so that
1252  * we don't generate useless partial paths for it.
1253  */
1254  if (!rel->consider_parallel)
1255  childrel->consider_parallel = false;
1256 
1257  /*
1258  * Compute the child's access paths.
1259  */
1260  set_rel_pathlist(root, childrel, childRTindex, childRTE);
1261 
1262  /*
1263  * If child is dummy, ignore it.
1264  */
1265  if (IS_DUMMY_REL(childrel))
1266  continue;
1267 
1268  /* Bubble up childrel's partitioned children. */
1269  if (rel->part_scheme)
1270  rel->partitioned_child_rels =
1271  list_concat(rel->partitioned_child_rels,
1272  childrel->partitioned_child_rels);
1273 
1274  /*
1275  * Child is live, so add it to the live_childrels list for use below.
1276  */
1277  live_childrels = lappend(live_childrels, childrel);
1278  }
1279 
1280  /* Add paths to the append relation. */
1281  add_paths_to_append_rel(root, rel, live_childrels);
1282 }
1283 
1284 
1285 /*
1286  * add_paths_to_append_rel
1287  * Generate paths for the given append relation given the set of non-dummy
1288  * child rels.
1289  *
1290  * The function collects all parameterizations and orderings supported by the
1291  * non-dummy children. For every such parameterization or ordering, it creates
1292  * an append path collecting one path from each non-dummy child with given
1293  * parameterization or ordering. Similarly it collects partial paths from
1294  * non-dummy children to create partial append paths.
1295  */
1296 void
1297 add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
1298  List *live_childrels)
1299 {
1300  List *subpaths = NIL;
1301  bool subpaths_valid = true;
1302  List *partial_subpaths = NIL;
1303  List *pa_partial_subpaths = NIL;
1304  List *pa_nonpartial_subpaths = NIL;
1305  bool partial_subpaths_valid = true;
1306  bool pa_subpaths_valid;
1307  List *all_child_pathkeys = NIL;
1308  List *all_child_outers = NIL;
1309  ListCell *l;
1310  List *partitioned_rels = NIL;
1311  double partial_rows = -1;
1312 
1313  /* If appropriate, consider parallel append */
1314  pa_subpaths_valid = enable_parallel_append && rel->consider_parallel;
1315 
1316  /*
1317  * AppendPath generated for partitioned tables must record the RT indexes
1318  * of partitioned tables that are direct or indirect children of this
1319  * Append rel.
1320  *
1321  * AppendPath may be for a sub-query RTE (UNION ALL), in which case, 'rel'
1322  * itself does not represent a partitioned relation, but the child sub-
1323  * queries may contain references to partitioned relations. The loop
1324  * below will look for such children and collect them in a list to be
1325  * passed to the path creation function. (This assumes that we don't need
1326  * to look through multiple levels of subquery RTEs; if we ever do, we
1327  * could consider stuffing the list we generate here into sub-query RTE's
1328  * RelOptInfo, just like we do for partitioned rels, which would be used
1329  * when populating our parent rel with paths. For the present, that
1330  * appears to be unnecessary.)
1331  */
1332  if (rel->part_scheme != NULL)
1333  {
1334  if (IS_SIMPLE_REL(rel))
1335  partitioned_rels = list_make1(rel->partitioned_child_rels);
1336  else if (IS_JOIN_REL(rel))
1337  {
1338  int relid = -1;
1339  List *partrels = NIL;
1340 
1341  /*
1342  * For a partitioned joinrel, concatenate the component rels'
1343  * partitioned_child_rels lists.
1344  */
1345  while ((relid = bms_next_member(rel->relids, relid)) >= 0)
1346  {
1347  RelOptInfo *component;
1348 
1349  Assert(relid >= 1 && relid < root->simple_rel_array_size);
1350  component = root->simple_rel_array[relid];
1351  Assert(component->part_scheme != NULL);
1352  Assert(list_length(component->partitioned_child_rels) >= 1);
1353  partrels = list_concat(partrels,
1354  component->partitioned_child_rels);
1355  }
1356 
1357  partitioned_rels = list_make1(partrels);
1358  }
1359 
1360  Assert(list_length(partitioned_rels) >= 1);
1361  }
1362 
1363  /*
1364  * For every non-dummy child, remember the cheapest path. Also, identify
1365  * all pathkeys (orderings) and parameterizations (required_outer sets)
1366  * available for the non-dummy member relations.
1367  */
1368  foreach(l, live_childrels)
1369  {
1370  RelOptInfo *childrel = lfirst(l);
1371  ListCell *lcp;
1372  Path *cheapest_partial_path = NULL;
1373 
1374  /*
1375  * For UNION ALLs with non-empty partitioned_child_rels, accumulate
1376  * the Lists of child relations.
1377  */
1378  if (rel->rtekind == RTE_SUBQUERY && childrel->partitioned_child_rels != NIL)
1379  partitioned_rels = lappend(partitioned_rels,
1380  childrel->partitioned_child_rels);
1381 
1382  /*
1383  * If child has an unparameterized cheapest-total path, add that to
1384  * the unparameterized Append path we are constructing for the parent.
1385  * If not, there's no workable unparameterized path.
1386  *
1387  * With partitionwise aggregates, the child rel's pathlist may be
1388  * empty, so don't assume that a path exists here.
1389  */
1390  if (childrel->pathlist != NIL &&
1391  childrel->cheapest_total_path->param_info == NULL)
1392  accumulate_append_subpath(childrel->cheapest_total_path,
1393  &subpaths, NULL);
1394  else
1395  subpaths_valid = false;
1396 
1397  /* Same idea, but for a partial plan. */
1398  if (childrel->partial_pathlist != NIL)
1399  {
1400  cheapest_partial_path = linitial(childrel->partial_pathlist);
1401  accumulate_append_subpath(cheapest_partial_path,
1402  &partial_subpaths, NULL);
1403  }
1404  else
1405  partial_subpaths_valid = false;
1406 
1407  /*
1408  * Same idea, but for a parallel append mixing partial and non-partial
1409  * paths.
1410  */
1411  if (pa_subpaths_valid)
1412  {
1413  Path *nppath = NULL;
1414 
1415  nppath =
1416  get_cheapest_parallel_safe_total_inner(childrel->pathlist);
1417 
1418  if (cheapest_partial_path == NULL && nppath == NULL)
1419  {
1420  /* Neither a partial nor a parallel-safe path? Forget it. */
1421  pa_subpaths_valid = false;
1422  }
1423  else if (nppath == NULL ||
1424  (cheapest_partial_path != NULL &&
1425  cheapest_partial_path->total_cost < nppath->total_cost))
1426  {
1427  /* Partial path is cheaper or the only option. */
1428  Assert(cheapest_partial_path != NULL);
1429  accumulate_append_subpath(cheapest_partial_path,
1430  &pa_partial_subpaths,
1431  &pa_nonpartial_subpaths);
1432 
1433  }
1434  else
1435  {
1436  /*
1437  * Either we've got only a non-partial path, or we think that
1438  * a single backend can execute the best non-partial path
1439  * faster than all the parallel backends working together can
1440  * execute the best partial path.
1441  *
1442  * It might make sense to be more aggressive here. Even if
1443  * the best non-partial path is more expensive than the best
1444  * partial path, it could still be better to choose the
1445  * non-partial path if there are several such paths that can
1446  * be given to different workers. For now, we don't try to
1447  * figure that out.
1448  */
1449  accumulate_append_subpath(nppath,
1450  &pa_nonpartial_subpaths,
1451  NULL);
1452  }
1453  }
1454 
1455  /*
1456  * Collect lists of all the available path orderings and
1457  * parameterizations for all the children. We use these as a
1458  * heuristic to indicate which sort orderings and parameterizations we
1459  * should build Append and MergeAppend paths for.
1460  */
1461  foreach(lcp, childrel->pathlist)
1462  {
1463  Path *childpath = (Path *) lfirst(lcp);
1464  List *childkeys = childpath->pathkeys;
1465  Relids childouter = PATH_REQ_OUTER(childpath);
1466 
1467  /* Unsorted paths don't contribute to pathkey list */
1468  if (childkeys != NIL)
1469  {
1470  ListCell *lpk;
1471  bool found = false;
1472 
1473  /* Have we already seen this ordering? */
1474  foreach(lpk, all_child_pathkeys)
1475  {
1476  List *existing_pathkeys = (List *) lfirst(lpk);
1477 
1478  if (compare_pathkeys(existing_pathkeys,
1479  childkeys) == PATHKEYS_EQUAL)
1480  {
1481  found = true;
1482  break;
1483  }
1484  }
1485  if (!found)
1486  {
1487  /* No, so add it to all_child_pathkeys */
1488  all_child_pathkeys = lappend(all_child_pathkeys,
1489  childkeys);
1490  }
1491  }
1492 
1493  /* Unparameterized paths don't contribute to param-set list */
1494  if (childouter)
1495  {
1496  ListCell *lco;
1497  bool found = false;
1498 
1499  /* Have we already seen this param set? */
1500  foreach(lco, all_child_outers)
1501  {
1502  Relids existing_outers = (Relids) lfirst(lco);
1503 
1504  if (bms_equal(existing_outers, childouter))
1505  {
1506  found = true;
1507  break;
1508  }
1509  }
1510  if (!found)
1511  {
1512  /* No, so add it to all_child_outers */
1513  all_child_outers = lappend(all_child_outers,
1514  childouter);
1515  }
1516  }
1517  }
1518  }
1519 
1520  /*
1521  * If we found unparameterized paths for all children, build an unordered,
1522  * unparameterized Append path for the rel. (Note: this is correct even
1523  * if we have zero or one live subpath due to constraint exclusion.)
1524  */
1525  if (subpaths_valid)
1526  add_path(rel, (Path *) create_append_path(root, rel, subpaths, NIL,
1527  NIL, NULL, 0, false,
1528  partitioned_rels, -1));
1529 
1530  /*
1531  * Consider an append of unordered, unparameterized partial paths. Make
1532  * it parallel-aware if possible.
1533  */
1534  if (partial_subpaths_valid && partial_subpaths != NIL)
1535  {
1536  AppendPath *appendpath;
1537  ListCell *lc;
1538  int parallel_workers = 0;
1539 
1540  /* Find the highest number of workers requested for any subpath. */
1541  foreach(lc, partial_subpaths)
1542  {
1543  Path *path = lfirst(lc);
1544 
1545  parallel_workers = Max(parallel_workers, path->parallel_workers);
1546  }
1547  Assert(parallel_workers > 0);
1548 
1549  /*
1550  * If the use of parallel append is permitted, always request at least
1551  * log2(# of children) workers. We assume it can be useful to have
1552  * extra workers in this case because they will be spread out across
1553  * the children. The precise formula is just a guess, but we don't
1554  * want to end up with a radically different answer for a table with N
1555  * partitions vs. an unpartitioned table with the same data, so the
1556  * use of some kind of log-scaling here seems to make some sense.
1557  */
1558  if (enable_parallel_append)
1559  {
1560  parallel_workers = Max(parallel_workers,
1561  fls(list_length(live_childrels)));
1562  parallel_workers = Min(parallel_workers,
1563  max_parallel_workers_per_gather);
1564  }
1565  Assert(parallel_workers > 0);
1566 
1567  /* Generate a partial append path. */
1568  appendpath = create_append_path(root, rel, NIL, partial_subpaths,
1569  NIL, NULL, parallel_workers,
1570  enable_parallel_append,
1571  partitioned_rels, -1);
1572 
1573  /*
1574  * Make sure any subsequent partial paths use the same row count
1575  * estimate.
1576  */
1577  partial_rows = appendpath->path.rows;
1578 
1579  /* Add the path. */
1580  add_partial_path(rel, (Path *) appendpath);
1581  }
1582 
1583  /*
1584  * Consider a parallel-aware append using a mix of partial and non-partial
1585  * paths. (This only makes sense if there's at least one child which has
1586  * a non-partial path that is substantially cheaper than any partial path;
1587  * otherwise, we should use the append path added in the previous step.)
1588  */
1589  if (pa_subpaths_valid && pa_nonpartial_subpaths != NIL)
1590  {
1591  AppendPath *appendpath;
1592  ListCell *lc;
1593  int parallel_workers = 0;
1594 
1595  /*
1596  * Find the highest number of workers requested for any partial
1597  * subpath.
1598  */
1599  foreach(lc, pa_partial_subpaths)
1600  {
1601  Path *path = lfirst(lc);
1602 
1603  parallel_workers = Max(parallel_workers, path->parallel_workers);
1604  }
1605 
1606  /*
1607  * Same formula here as above. It's even more important in this
1608  * instance because the non-partial paths won't contribute anything to
1609  * the planned number of parallel workers.
1610  */
1611  parallel_workers = Max(parallel_workers,
1612  fls(list_length(live_childrels)));
1613  parallel_workers = Min(parallel_workers,
1614  max_parallel_workers_per_gather);
1615  Assert(parallel_workers > 0);
1616 
1617  appendpath = create_append_path(root, rel, pa_nonpartial_subpaths,
1618  pa_partial_subpaths,
1619  NIL, NULL, parallel_workers, true,
1620  partitioned_rels, partial_rows);
1621  add_partial_path(rel, (Path *) appendpath);
1622  }
1623 
1624  /*
1625  * Also build unparameterized ordered append paths based on the collected
1626  * list of child pathkeys.
1627  */
1628  if (subpaths_valid)
1629  generate_orderedappend_paths(root, rel, live_childrels,
1630  all_child_pathkeys,
1631  partitioned_rels);
1632 
1633  /*
1634  * Build Append paths for each parameterization seen among the child rels.
1635  * (This may look pretty expensive, but in most cases of practical
1636  * interest, the child rels will expose mostly the same parameterizations,
1637  * so that not that many cases actually get considered here.)
1638  *
1639  * The Append node itself cannot enforce quals, so all qual checking must
1640  * be done in the child paths. This means that to have a parameterized
1641  * Append path, we must have the exact same parameterization for each
1642  * child path; otherwise some children might be failing to check the
1643  * moved-down quals. To make them match up, we can try to increase the
1644  * parameterization of lesser-parameterized paths.
1645  */
1646  foreach(l, all_child_outers)
1647  {
1648  Relids required_outer = (Relids) lfirst(l);
1649  ListCell *lcr;
1650 
1651  /* Select the child paths for an Append with this parameterization */
1652  subpaths = NIL;
1653  subpaths_valid = true;
1654  foreach(lcr, live_childrels)
1655  {
1656  RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
1657  Path *subpath;
1658 
1659  if (childrel->pathlist == NIL)
1660  {
1661  /* failed to make a suitable path for this child */
1662  subpaths_valid = false;
1663  break;
1664  }
1665 
1666  subpath = get_cheapest_parameterized_child_path(root,
1667  childrel,
1668  required_outer);
1669  if (subpath == NULL)
1670  {
1671  /* failed to make a suitable path for this child */
1672  subpaths_valid = false;
1673  break;
1674  }
1675  accumulate_append_subpath(subpath, &subpaths, NULL);
1676  }
1677 
1678  if (subpaths_valid)
1679  add_path(rel, (Path *)
1680  create_append_path(root, rel, subpaths, NIL,
1681  NIL, required_outer, 0, false,
1682  partitioned_rels, -1));
1683  }
1684 
1685  /*
1686  * When there is only a single child relation, the Append path can inherit
1687  * any ordering available for the child rel's path, so that it's useful to
1688  * consider ordered partial paths. Above we only considered the cheapest
1689  * partial path for each child, but let's also make paths using any
1690  * partial paths that have pathkeys.
1691  */
1692  if (list_length(live_childrels) == 1)
1693  {
1694  RelOptInfo *childrel = (RelOptInfo *) linitial(live_childrels);
1695 
1696  foreach(l, childrel->partial_pathlist)
1697  {
1698  Path *path = (Path *) lfirst(l);
1699  AppendPath *appendpath;
1700 
1701  /*
1702  * Skip paths with no pathkeys. Also skip the cheapest partial
1703  * path, since we already used that above.
1704  */
1705  if (path->pathkeys == NIL ||
1706  path == linitial(childrel->partial_pathlist))
1707  continue;
1708 
1709  appendpath = create_append_path(root, rel, NIL, list_make1(path),
1710  NIL, NULL,
1711  path->parallel_workers, true,
1712  partitioned_rels, partial_rows);
1713  add_partial_path(rel, (Path *) appendpath);
1714  }
1715  }
1716 }
1717 
1718 /*
1719  * generate_orderedappend_paths
1720  * Generate ordered append paths for an append relation
1721  *
1722  * Usually we generate MergeAppend paths here, but there are some special
1723  * cases where we can generate simple Append paths, because the subpaths
1724  * can provide tuples in the required order already.
1725  *
1726  * We generate a path for each ordering (pathkey list) appearing in
1727  * all_child_pathkeys.
1728  *
1729  * We consider both cheapest-startup and cheapest-total cases, ie, for each
1730  * interesting ordering, collect all the cheapest startup subpaths and all the
1731  * cheapest total paths, and build a suitable path for each case.
1732  *
1733  * We don't currently generate any parameterized ordered paths here. While
1734  * it would not take much more code here to do so, it's very unclear that it
1735  * is worth the planning cycles to investigate such paths: there's little
1736  * use for an ordered path on the inside of a nestloop. In fact, it's likely
1737  * that the current coding of add_path would reject such paths out of hand,
1738  * because add_path gives no credit for sort ordering of parameterized paths,
1739  * and a parameterized MergeAppend is going to be more expensive than the
1740  * corresponding parameterized Append path. If we ever try harder to support
1741  * parameterized mergejoin plans, it might be worth adding support for
1742  * parameterized paths here to feed such joins. (See notes in
1743  * optimizer/README for why that might not ever happen, though.)
1744  */
1745 static void
1746 generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel,
1747  List *live_childrels,
1748  List *all_child_pathkeys,
1749  List *partitioned_rels)
1750 {
1751  ListCell *lcp;
1752  List *partition_pathkeys = NIL;
1753  List *partition_pathkeys_desc = NIL;
1754  bool partition_pathkeys_partial = true;
1755  bool partition_pathkeys_desc_partial = true;
1756 
1757  /*
1758  * Some partitioned table setups may allow us to use an Append node
1759  * instead of a MergeAppend. This is possible in cases such as RANGE
1760  * partitioned tables where it's guaranteed that an earlier partition must
1761  * contain rows which come earlier in the sort order. To detect whether
1762  * this is relevant, build pathkey descriptions of the partition ordering,
1763  * for both forward and reverse scans.
1764  */
1765  if (rel->part_scheme != NULL && IS_SIMPLE_REL(rel) &&
1766  partitions_are_ordered(rel->boundinfo, rel->nparts))
1767  {
1768  partition_pathkeys = build_partition_pathkeys(root, rel,
1769  ForwardScanDirection,
1770  &partition_pathkeys_partial);
1771 
1772  partition_pathkeys_desc = build_partition_pathkeys(root, rel,
1773  BackwardScanDirection,
1774  &partition_pathkeys_desc_partial);
1775 
1776  /*
1777  * You might think we should truncate_useless_pathkeys here, but
1778  * allowing partition keys which are a subset of the query's pathkeys
1779  * can often be useful. For example, consider a table partitioned by
1780  * RANGE (a, b), and a query with ORDER BY a, b, c. If we have child
1781  * paths that can produce the a, b, c ordering (perhaps via indexes on
1782  * (a, b, c)) then it works to consider the appendrel output as
1783  * ordered by a, b, c.
1784  */
1785  }
1786 
1787  /* Now consider each interesting sort ordering */
1788  foreach(lcp, all_child_pathkeys)
1789  {
1790  List *pathkeys = (List *) lfirst(lcp);
1791  List *startup_subpaths = NIL;
1792  List *total_subpaths = NIL;
1793  bool startup_neq_total = false;
1794  ListCell *lcr;
1795  bool match_partition_order;
1796  bool match_partition_order_desc;
1797 
1798  /*
1799  * Determine if this sort ordering matches any partition pathkeys we
1800  * have, for both ascending and descending partition order. If the
1801  * partition pathkeys happen to be contained in pathkeys then it still
1802  * works, as described above, providing that the partition pathkeys
1803  * are complete and not just a prefix of the partition keys. (In such
1804  * cases we'll be relying on the child paths to have sorted the
1805  * lower-order columns of the required pathkeys.)
1806  */
1807  match_partition_order =
1808  pathkeys_contained_in(pathkeys, partition_pathkeys) ||
1809  (!partition_pathkeys_partial &&
1810  pathkeys_contained_in(partition_pathkeys, pathkeys));
1811 
1812  match_partition_order_desc = !match_partition_order &&
1813  (pathkeys_contained_in(pathkeys, partition_pathkeys_desc) ||
1814  (!partition_pathkeys_desc_partial &&
1815  pathkeys_contained_in(partition_pathkeys_desc, pathkeys)));
1816 
1817  /* Select the child paths for this ordering... */
1818  foreach(lcr, live_childrels)
1819  {
1820  RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
1821  Path *cheapest_startup,
1822  *cheapest_total;
1823 
1824  /* Locate the right paths, if they are available. */
1825  cheapest_startup =
1826  get_cheapest_path_for_pathkeys(childrel->pathlist,
1827  pathkeys,
1828  NULL,
1829  STARTUP_COST,
1830  false);
1831  cheapest_total =
1832  get_cheapest_path_for_pathkeys(childrel->pathlist,
1833  pathkeys,
1834  NULL,
1835  TOTAL_COST,
1836  false);
1837 
1838  /*
1839  * If we can't find any paths with the right order just use the
1840  * cheapest-total path; we'll have to sort it later.
1841  */
1842  if (cheapest_startup == NULL || cheapest_total == NULL)
1843  {
1844  cheapest_startup = cheapest_total =
1845  childrel->cheapest_total_path;
1846  /* Assert we do have an unparameterized path for this child */
1847  Assert(cheapest_total->param_info == NULL);
1848  }
1849 
1850  /*
1851  * Notice whether we actually have different paths for the
1852  * "cheapest" and "total" cases; frequently there will be no point
1853  * in two create_merge_append_path() calls.
1854  */
1855  if (cheapest_startup != cheapest_total)
1856  startup_neq_total = true;
1857 
1858  /*
1859  * Collect the appropriate child paths. The required logic varies
1860  * for the Append and MergeAppend cases.
1861  */
1862  if (match_partition_order)
1863  {
1864  /*
1865  * We're going to make a plain Append path. We don't need
1866  * most of what accumulate_append_subpath would do, but we do
1867  * want to cut out child Appends or MergeAppends if they have
1868  * just a single subpath (and hence aren't doing anything
1869  * useful).
1870  */
1871  cheapest_startup = get_singleton_append_subpath(cheapest_startup);
1872  cheapest_total = get_singleton_append_subpath(cheapest_total);
1873 
1874  startup_subpaths = lappend(startup_subpaths, cheapest_startup);
1875  total_subpaths = lappend(total_subpaths, cheapest_total);
1876  }
1877  else if (match_partition_order_desc)
1878  {
1879  /*
1880  * As above, but we need to reverse the order of the children,
1881  * because nodeAppend.c doesn't know anything about reverse
1882  * ordering and will scan the children in the order presented.
1883  */
1884  cheapest_startup = get_singleton_append_subpath(cheapest_startup);
1885  cheapest_total = get_singleton_append_subpath(cheapest_total);
1886 
1887  startup_subpaths = lcons(cheapest_startup, startup_subpaths);
1888  total_subpaths = lcons(cheapest_total, total_subpaths);
1889  }
1890  else
1891  {
1892  /*
1893  * Otherwise, rely on accumulate_append_subpath to collect the
1894  * child paths for the MergeAppend.
1895  */
1896  accumulate_append_subpath(cheapest_startup,
1897  &startup_subpaths, NULL);
1898  accumulate_append_subpath(cheapest_total,
1899  &total_subpaths, NULL);
1900  }
1901  }
1902 
1903  /* ... and build the Append or MergeAppend paths */
1904  if (match_partition_order || match_partition_order_desc)
1905  {
1906  /* We only need Append */
1907  add_path(rel, (Path *) create_append_path(root,
1908  rel,
1909  startup_subpaths,
1910  NIL,
1911  pathkeys,
1912  NULL,
1913  0,
1914  false,
1915  partitioned_rels,
1916  -1));
1917  if (startup_neq_total)
1918  add_path(rel, (Path *) create_append_path(root,
1919  rel,
1920  total_subpaths,
1921  NIL,
1922  pathkeys,
1923  NULL,
1924  0,
1925  false,
1926  partitioned_rels,
1927  -1));
1928  }
1929  else
1930  {
1931  /* We need MergeAppend */
1932  add_path(rel, (Path *) create_merge_append_path(root,
1933  rel,
1934  startup_subpaths,
1935  pathkeys,
1936  NULL,
1937  partitioned_rels));
1938  if (startup_neq_total)
1939  add_path(rel, (Path *) create_merge_append_path(root,
1940  rel,
1941  total_subpaths,
1942  pathkeys,
1943  NULL,
1944  partitioned_rels));
1945  }
1946  }
1947 }
1948 
1949 /*
1950  * get_cheapest_parameterized_child_path
1951  * Get cheapest path for this relation that has exactly the requested
1952  * parameterization.
1953  *
1954  * Returns NULL if unable to create such a path.
1955  */
1956 static Path *
1957 get_cheapest_parameterized_child_path(PlannerInfo *root, RelOptInfo *rel,
1958  Relids required_outer)
1959 {
1960  Path *cheapest;
1961  ListCell *lc;
1962 
1963  /*
1964  * Look up the cheapest existing path with no more than the needed
1965  * parameterization. If it has exactly the needed parameterization, we're
1966  * done.
1967  */
1968  cheapest = get_cheapest_path_for_pathkeys(rel->pathlist,
1969  NIL,
1970  required_outer,
1971  TOTAL_COST,
1972  false);
1973  Assert(cheapest != NULL);
1974  if (bms_equal(PATH_REQ_OUTER(cheapest), required_outer))
1975  return cheapest;
1976 
1977  /*
1978  * Otherwise, we can "reparameterize" an existing path to match the given
1979  * parameterization, which effectively means pushing down additional
1980  * joinquals to be checked within the path's scan. However, some existing
1981  * paths might check the available joinquals already while others don't;
1982  * therefore, it's not clear which existing path will be cheapest after
1983  * reparameterization. We have to go through them all and find out.
1984  */
1985  cheapest = NULL;
1986  foreach(lc, rel->pathlist)
1987  {
1988  Path *path = (Path *) lfirst(lc);
1989 
1990  /* Can't use it if it needs more than requested parameterization */
1991  if (!bms_is_subset(PATH_REQ_OUTER(path), required_outer))
1992  continue;
1993 
1994  /*
1995  * Reparameterization can only increase the path's cost, so if it's
1996  * already more expensive than the current cheapest, forget it.
1997  */
1998  if (cheapest != NULL &&
1999  compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
2000  continue;
2001 
2002  /* Reparameterize if needed, then recheck cost */
2003  if (!bms_equal(PATH_REQ_OUTER(path), required_outer))
2004  {
2005  path = reparameterize_path(root, path, required_outer, 1.0);
2006  if (path == NULL)
2007  continue; /* failed to reparameterize this one */
2008  Assert(bms_equal(PATH_REQ_OUTER(path), required_outer));
2009 
2010  if (cheapest != NULL &&
2011  compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
2012  continue;
2013  }
2014 
2015  /* We have a new best path */
2016  cheapest = path;
2017  }
2018 
2019  /* Return the best path, or NULL if we found no suitable candidate */
2020  return cheapest;
2021 }
2022 
2023 /*
2024  * accumulate_append_subpath
2025  * Add a subpath to the list being built for an Append or MergeAppend.
2026  *
2027  * It's possible that the child is itself an Append or MergeAppend path, in
2028  * which case we can "cut out the middleman" and just add its child paths to
2029  * our own list. (We don't try to do this earlier because we need to apply
2030  * both levels of transformation to the quals.)
2031  *
2032  * Note that if we omit a child MergeAppend in this way, we are effectively
2033  * omitting a sort step, which seems fine: if the parent is to be an Append,
2034  * its result would be unsorted anyway, while if the parent is to be a
2035  * MergeAppend, there's no point in a separate sort on a child.
2036  *
2037  * Normally, either path is a partial path and subpaths is a list of partial
2038  * paths, or else path is a non-partial plan and subpaths is a list of those.
2039  * However, if path is a parallel-aware Append, then we add its partial path
2040  * children to subpaths and the rest to special_subpaths. If the latter is
2041  * NULL, we don't flatten the path at all (unless it contains only partial
2042  * paths).
2043  */
2044 static void
2045 accumulate_append_subpath(Path *path, List **subpaths, List **special_subpaths)
2046 {
2047  if (IsA(path, AppendPath))
2048  {
2049  AppendPath *apath = (AppendPath *) path;
2050 
2051  if (!apath->path.parallel_aware || apath->first_partial_path == 0)
2052  {
2053  *subpaths = list_concat(*subpaths, apath->subpaths);
2054  return;
2055  }
2056  else if (special_subpaths != NULL)
2057  {
2058  List *new_special_subpaths;
2059 
2060  /* Split Parallel Append into partial and non-partial subpaths */
2061  *subpaths = list_concat(*subpaths,
2062  list_copy_tail(apath->subpaths,
2063  apath->first_partial_path));
2064  new_special_subpaths =
2065  list_truncate(list_copy(apath->subpaths),
2066  apath->first_partial_path);
2067  *special_subpaths = list_concat(*special_subpaths,
2068  new_special_subpaths);
2069  return;
2070  }
2071  }
2072  else if (IsA(path, MergeAppendPath))
2073  {
2074  MergeAppendPath *mpath = (MergeAppendPath *) path;
2075 
2076  *subpaths = list_concat(*subpaths, mpath->subpaths);
2077  return;
2078  }
2079 
2080  *subpaths = lappend(*subpaths, path);
2081 }
2082 
2083 /*
2084  * get_singleton_append_subpath
2085  * Returns the single subpath of an Append/MergeAppend, or just
2086  * return 'path' if it's not a single sub-path Append/MergeAppend.
2087  *
2088  * Note: 'path' must not be a parallel-aware path.
2089  */
2090 static Path *
2091 get_singleton_append_subpath(Path *path)
2092 {
2093  Assert(!path->parallel_aware);
2094 
2095  if (IsA(path, AppendPath))
2096  {
2097  AppendPath *apath = (AppendPath *) path;
2098 
2099  if (list_length(apath->subpaths) == 1)
2100  return (Path *) linitial(apath->subpaths);
2101  }
2102  else if (IsA(path, MergeAppendPath))
2103  {
2104  MergeAppendPath *mpath = (MergeAppendPath *) path;
2105 
2106  if (list_length(mpath->subpaths) == 1)
2107  return (Path *) linitial(mpath->subpaths);
2108  }
2109 
2110  return path;
2111 }
2112 
2113 /*
2114  * set_dummy_rel_pathlist
2115  * Build a dummy path for a relation that's been excluded by constraints
2116  *
2117  * Rather than inventing a special "dummy" path type, we represent this as an
2118  * AppendPath with no members (see also IS_DUMMY_APPEND/IS_DUMMY_REL macros).
2119  *
2120  * (See also mark_dummy_rel, which does basically the same thing, but is
2121  * typically used to change a rel into dummy state after we already made
2122  * paths for it.)
2123  */
2124 static void
2125 set_dummy_rel_pathlist(RelOptInfo *rel)
2126 {
2127  /* Set dummy size estimates --- we leave attr_widths[] as zeroes */
2128  rel->rows = 0;
2129  rel->reltarget->width = 0;
2130 
2131  /* Discard any pre-existing paths; no further need for them */
2132  rel->pathlist = NIL;
2133  rel->partial_pathlist = NIL;
2134 
2135  /* Set up the dummy path */
2136  add_path(rel, (Path *) create_append_path(NULL, rel, NIL, NIL,
2137  NIL, rel->lateral_relids,
2138  0, false, NIL, -1));
2139 
2140  /*
2141  * We set the cheapest-path fields immediately, just in case they were
2142  * pointing at some discarded path. This is redundant when we're called
2143  * from set_rel_size(), but not when called from elsewhere, and doing it
2144  * twice is harmless anyway.
2145  */
2146  set_cheapest(rel);
2147 }
2148 
2149 /* quick-and-dirty test to see if any joining is needed */
2150 static bool
2151 has_multiple_baserels(PlannerInfo *root)
2152 {
2153  int num_base_rels = 0;
2154  Index rti;
2155 
2156  for (rti = 1; rti < root->simple_rel_array_size; rti++)
2157  {
2158  RelOptInfo *brel = root->simple_rel_array[rti];
2159 
2160  if (brel == NULL)
2161  continue;
2162 
2163  /* ignore RTEs that are "other rels" */
2164  if (brel->reloptkind == RELOPT_BASEREL)
2165  if (++num_base_rels > 1)
2166  return true;
2167  }
2168  return false;
2169 }
2170 
2171 /*
2172  * set_subquery_pathlist
2173  * Generate SubqueryScan access paths for a subquery RTE
2174  *
2175  * We don't currently support generating parameterized paths for subqueries
2176  * by pushing join clauses down into them; it seems too expensive to re-plan
2177  * the subquery multiple times to consider different alternatives.
2178  * (XXX that could stand to be reconsidered, now that we use Paths.)
2179  * So the paths made here will be parameterized if the subquery contains
2180  * LATERAL references, otherwise not. As long as that's true, there's no need
2181  * for a separate set_subquery_size phase: just make the paths right away.
2182  */
2183 static void
2184 set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
2185  Index rti, RangeTblEntry *rte)
2186 {
2187  Query *parse = root->parse;
2188  Query *subquery = rte->subquery;
2189  Relids required_outer;
2190  pushdown_safety_info safetyInfo;
2191  double tuple_fraction;
2192  RelOptInfo *sub_final_rel;
2193  ListCell *lc;
2194 
2195  /*
2196  * Must copy the Query so that planning doesn't mess up the RTE contents
2197  * (really really need to fix the planner to not scribble on its input,
2198  * someday ... but see remove_unused_subquery_outputs to start with).
2199  */
2200  subquery = copyObject(subquery);
2201 
2202  /*
2203  * If it's a LATERAL subquery, it might contain some Vars of the current
2204  * query level, requiring it to be treated as parameterized, even though
2205  * we don't support pushing down join quals into subqueries.
2206  */
2207  required_outer = rel->lateral_relids;
2208 
2209  /*
2210  * Zero out result area for subquery_is_pushdown_safe, so that it can set
2211  * flags as needed while recursing. In particular, we need a workspace
2212  * for keeping track of unsafe-to-reference columns. unsafeColumns[i]
2213  * will be set true if we find that output column i of the subquery is
2214  * unsafe to use in a pushed-down qual.
2215  */
2216  memset(&safetyInfo, 0, sizeof(safetyInfo));
2217  safetyInfo.unsafeColumns = (bool *)
2218  palloc0((list_length(subquery->targetList) + 1) * sizeof(bool));
2219 
2220  /*
2221  * If the subquery has the "security_barrier" flag, it means the subquery
2222  * originated from a view that must enforce row level security. Then we
2223  * must not push down quals that contain leaky functions. (Ideally this
2224  * would be checked inside subquery_is_pushdown_safe, but since we don't
2225  * currently pass the RTE to that function, we must do it here.)
2226  */
2227  safetyInfo.unsafeLeaky = rte->security_barrier;
2228 
2229  /*
2230  * If there are any restriction clauses that have been attached to the
2231  * subquery relation, consider pushing them down to become WHERE or HAVING
2232  * quals of the subquery itself. This transformation is useful because it
2233  * may allow us to generate a better plan for the subquery than evaluating
2234  * all the subquery output rows and then filtering them.
2235  *
2236  * There are several cases where we cannot push down clauses. Restrictions
2237  * involving the subquery are checked by subquery_is_pushdown_safe().
2238  * Restrictions on individual clauses are checked by
2239  * qual_is_pushdown_safe(). Also, we don't want to push down
2240  * pseudoconstant clauses; better to have the gating node above the
2241  * subquery.
2242  *
2243  * Non-pushed-down clauses will get evaluated as qpquals of the
2244  * SubqueryScan node.
2245  *
2246  * XXX Are there any cases where we want to make a policy decision not to
2247  * push down a pushable qual, because it'd result in a worse plan?
2248  */
2249  if (rel->baserestrictinfo != NIL &&
2250  subquery_is_pushdown_safe(subquery, subquery, &safetyInfo))
2251  {
2252  /* OK to consider pushing down individual quals */
2253  List *upperrestrictlist = NIL;
2254  ListCell *l;
2255 
2256  foreach(l, rel->baserestrictinfo)
2257  {
2258  RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
2259  Node *clause = (Node *) rinfo->clause;
2260 
2261  if (!rinfo->pseudoconstant &&
2262  qual_is_pushdown_safe(subquery, rti, clause, &safetyInfo))
2263  {
2264  /* Push it down */
2265  subquery_push_qual(subquery, rte, rti, clause);
2266  }
2267  else
2268  {
2269  /* Keep it in the upper query */
2270  upperrestrictlist = lappend(upperrestrictlist, rinfo);
2271  }
2272  }
2273  rel->baserestrictinfo = upperrestrictlist;
2274  /* We don't bother recomputing baserestrict_min_security */
2275  }
2276 
2277  pfree(safetyInfo.unsafeColumns);
2278 
2279  /*
2280  * The upper query might not use all the subquery's output columns; if
2281  * not, we can simplify.
2282  */
2283  remove_unused_subquery_outputs(subquery, rel);
2284 
2285  /*
2286  * We can safely pass the outer tuple_fraction down to the subquery if the
2287  * outer level has no joining, aggregation, or sorting to do. Otherwise
2288  * we'd better tell the subquery to plan for full retrieval. (XXX This
2289  * could probably be made more intelligent ...)
2290  */
2291  if (parse->hasAggs ||
2292  parse->groupClause ||
2293  parse->groupingSets ||
2294  parse->havingQual ||
2295  parse->distinctClause ||
2296  parse->sortClause ||
2297  has_multiple_baserels(root))
2298  tuple_fraction = 0.0; /* default case */
2299  else
2300  tuple_fraction = root->tuple_fraction;
2301 
2302  /* plan_params should not be in use in current query level */
2303  Assert(root->plan_params == NIL);
2304 
2305  /* Generate a subroot and Paths for the subquery */
2306  rel->subroot = subquery_planner(root->glob, subquery,
2307  root,
2308  false, tuple_fraction);
2309 
2310  /* Isolate the params needed by this specific subplan */
2311  rel->subplan_params = root->plan_params;
2312  root->plan_params = NIL;
2313 
2314  /*
2315  * It's possible that constraint exclusion proved the subquery empty. If
2316  * so, it's desirable to produce an unadorned dummy path so that we will
2317  * recognize appropriate optimizations at this query level.
2318  */
2319  sub_final_rel = fetch_upper_rel(rel->subroot, UPPERREL_FINAL, NULL);
2320 
2321  if (IS_DUMMY_REL(sub_final_rel))
2322  {
2323  set_dummy_rel_pathlist(rel);
2324  return;
2325  }
2326 
2327  /*
2328  * Mark rel with estimated output rows, width, etc. Note that we have to
2329  * do this before generating outer-query paths, else cost_subqueryscan is
2330  * not happy.
2331  */
2332  set_subquery_size_estimates(root, rel);
2333 
2334  /*
2335  * For each Path that subquery_planner produced, make a SubqueryScanPath
2336  * in the outer query.
2337  */
2338  foreach(lc, sub_final_rel->pathlist)
2339  {
2340  Path *subpath = (Path *) lfirst(lc);
2341  List *pathkeys;
2342 
2343  /* Convert subpath's pathkeys to outer representation */
2344  pathkeys = convert_subquery_pathkeys(root,
2345  rel,
2346  subpath->pathkeys,
2347  make_tlist_from_pathtarget(subpath->pathtarget));
2348 
2349  /* Generate outer path using this subpath */
2350  add_path(rel, (Path *)
2351  create_subqueryscan_path(root, rel, subpath,
2352  pathkeys, required_outer));
2353  }
2354 
2355  /* If outer rel allows parallelism, do same for partial paths. */
2356  if (rel->consider_parallel && bms_is_empty(required_outer))
2357  {
2358  /* If consider_parallel is false, there should be no partial paths. */
2359  Assert(sub_final_rel->consider_parallel ||
2360  sub_final_rel->partial_pathlist == NIL);
2361 
2362  /* Same for partial paths. */
2363  foreach(lc, sub_final_rel->partial_pathlist)
2364  {
2365  Path *subpath = (Path *) lfirst(lc);
2366  List *pathkeys;
2367 
2368  /* Convert subpath's pathkeys to outer representation */
2369  pathkeys = convert_subquery_pathkeys(root,
2370  rel,
2371  subpath->pathkeys,
2372  make_tlist_from_pathtarget(subpath->pathtarget));
2373 
2374  /* Generate outer path using this subpath */
2375  add_partial_path(rel, (Path *)
2376  create_subqueryscan_path(root, rel, subpath,
2377  pathkeys,
2378  required_outer));
2379  }
2380  }
2381 }
2382 
2383 /*
2384  * set_function_pathlist
2385  * Build the (single) access path for a function RTE
2386  */
2387 static void
2388 set_function_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
2389 {
2390  Relids required_outer;
2391  List *pathkeys = NIL;
2392 
2393  /*
2394  * We don't support pushing join clauses into the quals of a function
2395  * scan, but it could still have required parameterization due to LATERAL
2396  * refs in the function expression.
2397  */
2398  required_outer = rel->lateral_relids;
2399 
2400  /*
2401  * The result is considered unordered unless ORDINALITY was used, in which
2402  * case it is ordered by the ordinal column (the last one). See if we
2403  * care, by checking for uses of that Var in equivalence classes.
2404  */
2405  if (rte->funcordinality)
2406  {
2407  AttrNumber ordattno = rel->max_attr;
2408  Var *var = NULL;
2409  ListCell *lc;
2410 
2411  /*
2412  * Is there a Var for it in rel's targetlist? If not, the query did
2413  * not reference the ordinality column, or at least not in any way
2414  * that would be interesting for sorting.
2415  */
2416  foreach(lc, rel->reltarget->exprs)
2417  {
2418  Var *node = (Var *) lfirst(lc);
2419 
2420  /* checking varno/varlevelsup is just paranoia */
2421  if (IsA(node, Var) &&
2422  node->varattno == ordattno &&
2423  node->varno == rel->relid &&
2424  node->varlevelsup == 0)
2425  {
2426  var = node;
2427  break;
2428  }
2429  }
2430 
2431  /*
2432  * Try to build pathkeys for this Var with int8 sorting. We tell
2433  * build_expression_pathkey not to build any new equivalence class; if
2434  * the Var isn't already mentioned in some EC, it means that nothing
2435  * cares about the ordering.
2436  */
2437  if (var)
2438  pathkeys = build_expression_pathkey(root,
2439  (Expr *) var,
2440  NULL, /* below outer joins */
2441  Int8LessOperator,
2442  rel->relids,
2443  false);
2444  }
2445 
2446  /* Generate appropriate path */
2447  add_path(rel, create_functionscan_path(root, rel,
2448  pathkeys, required_outer));
2449 }
2450 
2451 /*
2452  * set_values_pathlist
2453  * Build the (single) access path for a VALUES RTE
2454  */
2455 static void
2456 set_values_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
2457 {
2458  Relids required_outer;
2459 
2460  /*
2461  * We don't support pushing join clauses into the quals of a values scan,
2462  * but it could still have required parameterization due to LATERAL refs
2463  * in the values expressions.
2464  */
2465  required_outer = rel->lateral_relids;
2466 
2467  /* Generate appropriate path */
2468  add_path(rel, create_valuesscan_path(root, rel, required_outer));
2469 }
2470 
2471 /*
2472  * set_tablefunc_pathlist
2473  * Build the (single) access path for a table func RTE
2474  */
2475 static void
2476 set_tablefunc_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
2477 {
2478  Relids required_outer;
2479 
2480  /*
2481  * We don't support pushing join clauses into the quals of a tablefunc
2482  * scan, but it could still have required parameterization due to LATERAL
2483  * refs in the function expression.
2484  */
2485  required_outer = rel->lateral_relids;
2486 
2487  /* Generate appropriate path */
2488  add_path(rel, create_tablefuncscan_path(root, rel,
2489  required_outer));
2490 }
2491 
2492 /*
2493  * set_cte_pathlist
2494  * Build the (single) access path for a non-self-reference CTE RTE
2495  *
2496  * There's no need for a separate set_cte_size phase, since we don't
2497  * support join-qual-parameterized paths for CTEs.
2498  */
2499 static void
2500 set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
2501 {
2502  Plan *cteplan;
2503  PlannerInfo *cteroot;
2504  Index levelsup;
2505  int ndx;
2506  ListCell *lc;
2507  int plan_id;
2508  Relids required_outer;
2509 
2510  /*
2511  * Find the referenced CTE, and locate the plan previously made for it.
2512  */
2513  levelsup = rte->ctelevelsup;
2514  cteroot = root;
2515  while (levelsup-- > 0)
2516  {
2517  cteroot = cteroot->parent_root;
2518  if (!cteroot) /* shouldn't happen */
2519  elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
2520  }
2521 
2522  /*
2523  * Note: cte_plan_ids can be shorter than cteList, if we are still working
2524  * on planning the CTEs (ie, this is a side-reference from another CTE).
2525  * So we mustn't use forboth here.
2526  */
2527  ndx = 0;
2528  foreach(lc, cteroot->parse->cteList)
2529  {
2530  CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
2531 
2532  if (strcmp(cte->ctename, rte->ctename) == 0)
2533  break;
2534  ndx++;
2535  }
2536  if (lc == NULL) /* shouldn't happen */
2537  elog(ERROR, "could not find CTE \"%s\"", rte->ctename);
2538  if (ndx >= list_length(cteroot->cte_plan_ids))
2539  elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
2540  plan_id = list_nth_int(cteroot->cte_plan_ids, ndx);
2541  Assert(plan_id > 0);
2542  cteplan = (Plan *) list_nth(root->glob->subplans, plan_id - 1);
2543 
2544  /* Mark rel with estimated output rows, width, etc */
2545  set_cte_size_estimates(root, rel, cteplan->plan_rows);
2546 
2547  /*
2548  * We don't support pushing join clauses into the quals of a CTE scan, but
2549  * it could still have required parameterization due to LATERAL refs in
2550  * its tlist.
2551  */
2552  required_outer = rel->lateral_relids;
2553 
2554  /* Generate appropriate path */
2555  add_path(rel, create_ctescan_path(root, rel, required_outer));
2556 }
2557 
2558 /*
2559  * set_namedtuplestore_pathlist
2560  * Build the (single) access path for a named tuplestore RTE
2561  *
2562  * There's no need for a separate set_namedtuplestore_size phase, since we
2563  * don't support join-qual-parameterized paths for tuplestores.
2564  */
2565 static void
2566 set_namedtuplestore_pathlist(PlannerInfo *root, RelOptInfo *rel,
2567  RangeTblEntry *rte)
2568 {
2569  Relids required_outer;
2570 
2571  /* Mark rel with estimated output rows, width, etc */
2572  set_namedtuplestore_size_estimates(root, rel);
2573 
2574  /*
2575  * We don't support pushing join clauses into the quals of a tuplestore
2576  * scan, but it could still have required parameterization due to LATERAL
2577  * refs in its tlist.
2578  */
2579  required_outer = rel->lateral_relids;
2580 
2581  /* Generate appropriate path */
2582  add_path(rel, create_namedtuplestorescan_path(root, rel, required_outer));
2583 
2584  /* Select cheapest path (pretty easy in this case...) */
2585  set_cheapest(rel);
2586 }
2587 
2588 /*
2589  * set_result_pathlist
2590  * Build the (single) access path for an RTE_RESULT RTE
2591  *
2592  * There's no need for a separate set_result_size phase, since we
2593  * don't support join-qual-parameterized paths for these RTEs.
2594  */
2595 static void
2596 set_result_pathlist(PlannerInfo *root, RelOptInfo *rel,
2597  RangeTblEntry *rte)
2598 {
2599  Relids required_outer;
2600 
2601  /* Mark rel with estimated output rows, width, etc */
2602  set_result_size_estimates(root, rel);
2603 
2604  /*
2605  * We don't support pushing join clauses into the quals of a Result scan,
2606  * but it could still have required parameterization due to LATERAL refs
2607  * in its tlist.
2608  */
2609  required_outer = rel->lateral_relids;
2610 
2611  /* Generate appropriate path */
2612  add_path(rel, create_resultscan_path(root, rel, required_outer));
2613 
2614  /* Select cheapest path (pretty easy in this case...) */
2615  set_cheapest(rel);
2616 }
2617 
2618 /*
2619  * set_worktable_pathlist
2620  * Build the (single) access path for a self-reference CTE RTE
2621  *
2622  * There's no need for a separate set_worktable_size phase, since we don't
2623  * support join-qual-parameterized paths for CTEs.
2624  */
2625 static void
2626 set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
2627 {
2628  Path *ctepath;
2629  PlannerInfo *cteroot;
2630  Index levelsup;
2631  Relids required_outer;
2632 
2633  /*
2634  * We need to find the non-recursive term's path, which is in the plan
2635  * level that's processing the recursive UNION, which is one level *below*
2636  * where the CTE comes from.
2637  */
2638  levelsup = rte->ctelevelsup;
2639  if (levelsup == 0) /* shouldn't happen */
2640  elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
2641  levelsup--;
2642  cteroot = root;
2643  while (levelsup-- > 0)
2644  {
2645  cteroot = cteroot->parent_root;
2646  if (!cteroot) /* shouldn't happen */
2647  elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
2648  }
2649  ctepath = cteroot->non_recursive_path;
2650  if (!ctepath) /* shouldn't happen */
2651  elog(ERROR, "could not find path for CTE \"%s\"", rte->ctename);
2652 
2653  /* Mark rel with estimated output rows, width, etc */
2654  set_cte_size_estimates(root, rel, ctepath->rows);
2655 
2656  /*
2657  * We don't support pushing join clauses into the quals of a worktable
2658  * scan, but it could still have required parameterization due to LATERAL
2659  * refs in its tlist. (I'm not sure this is actually possible given the
2660  * restrictions on recursive references, but it's easy enough to support.)
2661  */
2662  required_outer = rel->lateral_relids;
2663 
2664  /* Generate appropriate path */
2665  add_path(rel, create_worktablescan_path(root, rel, required_outer));
2666 }
2667 
2668 /*
2669  * generate_gather_paths
2670  * Generate parallel access paths for a relation by pushing a Gather or
2671  * Gather Merge on top of a partial path.
2672  *
2673  * This must not be called until after we're done creating all partial paths
2674  * for the specified relation. (Otherwise, add_partial_path might delete a
2675  * path that some GatherPath or GatherMergePath has a reference to.)
2676  *
2677  * If we're generating paths for a scan or join relation, override_rows will
2678  * be false, and we'll just use the relation's size estimate. When we're
2679  * being called for a partially-grouped path, though, we need to override
2680  * the rowcount estimate. (It's not clear that the particular value we're
2681  * using here is actually best, but the underlying rel has no estimate so
2682  * we must do something.)
2683  */
2684 void
2685 generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
2686 {
2687  Path *cheapest_partial_path;
2688  Path *simple_gather_path;
2689  ListCell *lc;
2690  double rows;
2691  double *rowsp = NULL;
2692 
2693  /* If there are no partial paths, there's nothing to do here. */
2694  if (rel->partial_pathlist == NIL)
2695  return;
2696 
2697  /* Should we override the rel's rowcount estimate? */
2698  if (override_rows)
2699  rowsp = &rows;
2700 
2701  /*
2702  * The output of Gather is always unsorted, so there's only one partial
2703  * path of interest: the cheapest one. That will be the one at the front
2704  * of partial_pathlist because of the way add_partial_path works.
2705  */
2706  cheapest_partial_path = linitial(rel->partial_pathlist);
2707  rows =
2708  cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
2709  simple_gather_path = (Path *)
2710  create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
2711  NULL, rowsp);
2712  add_path(rel, simple_gather_path);
2713 
2714  /*
2715  * For each useful ordering, we can consider an order-preserving Gather
2716  * Merge.
2717  */
2718  foreach(lc, rel->partial_pathlist)
2719  {
2720  Path *subpath = (Path *) lfirst(lc);
2721  GatherMergePath *path;
2722 
2723  if (subpath->pathkeys == NIL)
2724  continue;
2725 
2726  rows = subpath->rows * subpath->parallel_workers;
2727  path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
2728  subpath->pathkeys, NULL, rowsp);
2729  add_path(rel, &path->path);
2730  }
2731 }
2732 
2733 /*
2734  * get_useful_pathkeys_for_relation
2735  * Determine which orderings of a relation might be useful.
2736  *
2737  * Getting data in sorted order can be useful either because the requested
2738  * order matches the final output ordering for the overall query we're
2739  * planning, or because it enables an efficient merge join. Here, we try
2740  * to figure out which pathkeys to consider.
2741  *
2742  * This allows us to do incremental sort on top of an index scan under a gather
2743  * merge node, i.e. parallelized.
2744  *
2745  * XXX At the moment this can only ever return a list with a single element,
2746  * because it looks at query_pathkeys only. So we might return the pathkeys
2747  * directly, but it seems plausible we'll want to consider other orderings
2748  * in the future. For example, we might want to consider pathkeys useful for
2749  * merge joins.
2750  */
2751 static List *
2752 get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel)
2753 {
2754  List *useful_pathkeys_list = NIL;
2755 
2756  /*
2757  * Considering query_pathkeys is always worth it, because it might allow
2758  * us to avoid a total sort when we have a partially presorted path
2759  * available.
2760  */
2761  if (root->query_pathkeys)
2762  {
2763  ListCell *lc;
2764  int npathkeys = 0; /* useful pathkeys */
2765 
2766  foreach(lc, root->query_pathkeys)
2767  {
2768  PathKey *pathkey = (PathKey *) lfirst(lc);
2769  EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
2770 
2771  /*
2772  * We can only build an Incremental Sort for pathkeys which
2773  * contain an EC member in the current relation, so ignore any
2774  * suffix of the list as soon as we find a pathkey without an EC
2775  * member the relation.
2776  *
2777  * By still returning the prefix of the pathkeys list that does
2778  * meet criteria of EC membership in the current relation, we
2779  * enable not just an incremental sort on the entirety of
2780  * query_pathkeys but also incremental sort below a JOIN.
2781  */
2782  if (!find_em_expr_for_rel(pathkey_ec, rel))
2783  break;
2784 
2785  npathkeys++;
2786  }
2787 
2788  /*
2789  * The whole query_pathkeys list matches, so append it directly, to
2790  * allow comparing pathkeys easily by comparing list pointer. If we
2791  * have to truncate the pathkeys, we gotta do a copy though.
2792  */
2793  if (npathkeys == list_length(root->query_pathkeys))
2794  useful_pathkeys_list = lappend(useful_pathkeys_list,
2795  root->query_pathkeys);
2796  else if (npathkeys > 0)
2797  useful_pathkeys_list = lappend(useful_pathkeys_list,
2798  list_truncate(list_copy(root->query_pathkeys),
2799  npathkeys));
2800  }
2801 
2802  return useful_pathkeys_list;
2803 }
2804 
2805 /*
2806  * generate_useful_gather_paths
2807  * Generate parallel access paths for a relation by pushing a Gather or
2808  * Gather Merge on top of a partial path.
2809  *
2810  * Unlike plain generate_gather_paths, this looks both at pathkeys of input
2811  * paths (aiming to preserve the ordering), but also considers ordering that
2812  * might be useful for nodes above the gather merge node, and tries to add
2813  * a sort (regular or incremental) to provide that.
2814  */
2815 void
2816 generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
2817 {
2818  ListCell *lc;
2819  double rows;
2820  double *rowsp = NULL;
2821  List *useful_pathkeys_list = NIL;
2822  Path *cheapest_partial_path = NULL;
2823 
2824  /* If there are no partial paths, there's nothing to do here. */
2825  if (rel->partial_pathlist == NIL)
2826  return;
2827 
2828  /* Should we override the rel's rowcount estimate? */
2829  if (override_rows)
2830  rowsp = &rows;
2831 
2832  /* generate the regular gather (merge) paths */
2833  generate_gather_paths(root, rel, override_rows);
2834 
2835  /* consider incremental sort for interesting orderings */
2836  useful_pathkeys_list = get_useful_pathkeys_for_relation(root, rel);
2837 
2838  /* used for explicit (full) sort paths */
2839  cheapest_partial_path = linitial(rel->partial_pathlist);
2840 
2841  /*
2842  * Consider incremental sort paths for each interesting ordering.
2843  */
2844  foreach(lc, useful_pathkeys_list)
2845  {
2846  List *useful_pathkeys = lfirst(lc);
2847  ListCell *lc2;
2848  bool is_sorted;
2849  int presorted_keys;
2850 
2851  foreach(lc2, rel->partial_pathlist)
2852  {
2853  Path *subpath = (Path *) lfirst(lc2);
2854  GatherMergePath *path;
2855 
2856  /*
2857  * If the path has no ordering at all, then we can't use either
2858  * incremental sort or rely on implict sorting with a gather
2859  * merge.
2860  */
2861  if (subpath->pathkeys == NIL)
2862  continue;
2863 
2864  is_sorted = pathkeys_count_contained_in(useful_pathkeys,
2865  subpath->pathkeys,
2866  &presorted_keys);
2867 
2868  /*
2869  * We don't need to consider the case where a subpath is already
2870  * fully sorted because generate_gather_paths already creates a
2871  * gather merge path for every subpath that has pathkeys present.
2872  *
2873  * But since the subpath is already sorted, we know we don't need
2874  * to consider adding a sort (other either kind) on top of it, so
2875  * we can continue here.
2876  */
2877  if (is_sorted)
2878  continue;
2879 
2880  /*
2881  * Consider regular sort for the cheapest partial path (for each
2882  * useful pathkeys). We know the path is not sorted, because we'd
2883  * not get here otherwise.
2884  *
2885  * This is not redundant with the gather paths created in
2886  * generate_gather_paths, because that doesn't generate ordered
2887  * output. Here we add an explicit sort to match the useful
2888  * ordering.
2889  */
2890  if (cheapest_partial_path == subpath)
2891  {
2892  Path *tmp;
2893 
2894  tmp = (Path *) create_sort_path(root,
2895  rel,
2896  subpath,
2897  useful_pathkeys,
2898  -1.0);
2899 
2900  rows = tmp->rows * tmp->parallel_workers;
2901 
2902  path = create_gather_merge_path(root, rel,
2903  tmp,
2904  rel->reltarget,
2905  tmp->pathkeys,
2906  NULL,
2907  rowsp);
2908 
2909  add_path(rel, &path->path);
2910 
2911  /* Fall through */
2912  }
2913 
2914  /*
2915  * Consider incremental sort, but only when the subpath is already
2916  * partially sorted on a pathkey prefix.
2917  */
2918  if (enable_incremental_sort && presorted_keys > 0)
2919  {
2920  Path *tmp;
2921 
2922  /*
2923  * We should have already excluded pathkeys of length 1
2924  * because then presorted_keys > 0 would imply is_sorted was
2925  * true.
2926  */
2927  Assert(list_length(useful_pathkeys) != 1);
2928 
2929  tmp = (Path *) create_incremental_sort_path(root,
2930  rel,
2931  subpath,
2932  useful_pathkeys,
2933  presorted_keys,
2934  -1);
2935 
2936  path = create_gather_merge_path(root, rel,
2937  tmp,
2938  rel->reltarget,
2939  tmp->pathkeys,
2940  NULL,
2941  rowsp);
2942 
2943  add_path(rel, &path->path);
2944  }
2945  }
2946  }
2947 }
2948 
2949 /*
2950  * make_rel_from_joinlist
2951  * Build access paths using a "joinlist" to guide the join path search.
2952  *
2953  * See comments for deconstruct_jointree() for definition of the joinlist
2954  * data structure.
2955  */
2956 static RelOptInfo *
2957 make_rel_from_joinlist(PlannerInfo *root, List *joinlist)
2958 {
2959  int levels_needed;
2960  List *initial_rels;
2961  ListCell *jl;
2962 
2963  /*
2964  * Count the number of child joinlist nodes. This is the depth of the
2965  * dynamic-programming algorithm we must employ to consider all ways of
2966  * joining the child nodes.
2967  */
2968  levels_needed = list_length(joinlist);
2969 
2970  if (levels_needed <= 0)
2971  return NULL; /* nothing to do? */
2972 
2973  /*
2974  * Construct a list of rels corresponding to the child joinlist nodes.
2975  * This may contain both base rels and rels constructed according to
2976  * sub-joinlists.
2977  */
2978  initial_rels = NIL;
2979  foreach(jl, joinlist)
2980  {
2981  Node *jlnode = (Node *) lfirst(jl);
2982  RelOptInfo *thisrel;
2983 
2984  if (IsA(jlnode, RangeTblRef))
2985  {
2986  int varno = ((RangeTblRef *) jlnode)->rtindex;
2987 
2988  thisrel = find_base_rel(root, varno);
2989  }
2990  else if (IsA(jlnode, List))
2991  {
2992  /* Recurse to handle subproblem */
2993  thisrel = make_rel_from_joinlist(root, (List *) jlnode);
2994  }
2995  else
2996  {
2997  elog(ERROR, "unrecognized joinlist node type: %d",
2998  (int) nodeTag(jlnode));
2999  thisrel = NULL; /* keep compiler quiet */
3000  }
3001 
3002  initial_rels = lappend(initial_rels, thisrel);
3003  }
3004 
3005  if (levels_needed == 1)
3006  {
3007  /*
3008  * Single joinlist node, so we're done.
3009  */
3010  return (RelOptInfo *) linitial(initial_rels);
3011  }
3012  else
3013  {
3014  /*
3015  * Consider the different orders in which we could join the rels,
3016  * using a plugin, GEQO, or the regular join search code.
3017  *
3018  * We put the initial_rels list into a PlannerInfo field because
3019  * has_legal_joinclause() needs to look at it (ugly :-().
3020  */
3021  root->initial_rels = initial_rels;
3022 
3023  if (join_search_hook)
3024  return (*join_search_hook) (root, levels_needed, initial_rels);
3025  else if (enable_geqo && levels_needed >= geqo_threshold)
3026  return geqo(root, levels_needed, initial_rels);
3027  else
3028  return standard_join_search(root, levels_needed, initial_rels);
3029  }
3030 }
3031 
3032 /*
3033  * standard_join_search
3034  * Find possible joinpaths for a query by successively finding ways
3035  * to join component relations into join relations.
3036  *
3037  * 'levels_needed' is the number of iterations needed, ie, the number of
3038  * independent jointree items in the query. This is > 1.
3039  *
3040  * 'initial_rels' is a list of RelOptInfo nodes for each independent
3041  * jointree item. These are the components to be joined together.
3042  * Note that levels_needed == list_length(initial_rels).
3043  *
3044  * Returns the final level of join relations, i.e., the relation that is
3045  * the result of joining all the original relations together.
3046  * At least one implementation path must be provided for this relation and
3047  * all required sub-relations.
3048  *
3049  * To support loadable plugins that modify planner behavior by changing the
3050  * join searching algorithm, we provide a hook variable that lets a plugin
3051  * replace or supplement this function. Any such hook must return the same
3052  * final join relation as the standard code would, but it might have a
3053  * different set of implementation paths attached, and only the sub-joinrels
3054  * needed for these paths need have been instantiated.
3055  *
3056  * Note to plugin authors: the functions invoked during standard_join_search()
3057  * modify root->join_rel_list and root->join_rel_hash. If you want to do more
3058  * than one join-order search, you'll probably need to save and restore the
3059  * original states of those data structures. See geqo_eval() for an example.
3060  */
3061 RelOptInfo *
3062 standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
3063 {
3064  int lev;
3065  RelOptInfo *rel;
3066 
3067  /*
3068  * This function cannot be invoked recursively within any one planning
3069  * problem, so join_rel_level[] can't be in use already.
3070  */
3071  Assert(root->join_rel_level == NULL);
3072 
3073  /*
3074  * We employ a simple "dynamic programming" algorithm: we first find all
3075  * ways to build joins of two jointree items, then all ways to build joins
3076  * of three items (from two-item joins and single items), then four-item
3077  * joins, and so on until we have considered all ways to join all the
3078  * items into one rel.
3079  *
3080  * root->join_rel_level[j] is a list of all the j-item rels. Initially we
3081  * set root->join_rel_level[1] to represent all the single-jointree-item
3082  * relations.
3083  */
3084  root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));
3085 
3086  root->join_rel_level[1] = initial_rels;
3087 
3088  for (lev = 2; lev <= levels_needed; lev++)
3089  {
3090  ListCell *lc;
3091 
3092  /*
3093  * Determine all possible pairs of relations to be joined at this
3094  * level, and build paths for making each one from every available
3095  * pair of lower-level relations.
3096  */
3097  join_search_one_level(root, lev);
3098 
3099  /*
3100  * Run generate_partitionwise_join_paths() and generate_gather_paths()
3101  * for each just-processed joinrel. We could not do this earlier
3102  * because both regular and partial paths can get added to a
3103  * particular joinrel at multiple times within join_search_one_level.
3104  *
3105  * After that, we're done creating paths for the joinrel, so run
3106  * set_cheapest().
3107  */
3108  foreach(lc, root->join_rel_level[lev])
3109  {
3110  rel = (RelOptInfo *) lfirst(lc);
3111 
3112  /* Create paths for partitionwise joins. */
3113  generate_partitionwise_join_paths(root, rel);
3114 
3115  /*
3116  * Except for the topmost scan/join rel, consider gathering
3117  * partial paths. We'll do the same for the topmost scan/join rel
3118  * once we know the final targetlist (see grouping_planner).
3119  */
3120  if (lev < levels_needed)
3121  generate_useful_gather_paths(root, rel, false);
3122 
3123  /* Find and save the cheapest paths for this rel */
3124  set_cheapest(rel);
3125 
3126 #ifdef OPTIMIZER_DEBUG
3127  debug_print_rel(root, rel);
3128 #endif
3129  }
3130  }
3131 
3132  /*
3133  * We should have a single rel at the final level.
3134  */
3135  if (root->join_rel_level[levels_needed] == NIL)
3136  elog(ERROR, "failed to build any %d-way joins", levels_needed);
3137  Assert(list_length(root->join_rel_level[levels_needed]) == 1);
3138 
3139  rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);
3140 
3141  root->join_rel_level = NULL;
3142 
3143  return rel;
3144 }
3145 
3146 /*****************************************************************************
3147  * PUSHING QUALS DOWN INTO SUBQUERIES
3148  *****************************************************************************/
3149 
3150 /*
3151  * subquery_is_pushdown_safe - is a subquery safe for pushing down quals?
3152  *
3153  * subquery is the particular component query being checked. topquery
3154  * is the top component of a set-operations tree (the same Query if no
3155  * set-op is involved).
3156  *
3157  * Conditions checked here:
3158  *
3159  * 1. If the subquery has a LIMIT clause, we must not push down any quals,
3160  * since that could change the set of rows returned.
3161  *
3162  * 2. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
3163  * quals into it, because that could change the results.
3164  *
3165  * 3. If the subquery uses DISTINCT, we cannot push volatile quals into it.
3166  * This is because upper-level quals should semantically be evaluated only
3167  * once per distinct row, not once per original row, and if the qual is
3168  * volatile then extra evaluations could change the results. (This issue
3169  * does not apply to other forms of aggregation such as GROUP BY, because
3170  * when those are present we push into HAVING not WHERE, so that the quals
3171  * are still applied after aggregation.)
3172  *
3173  * 4. If the subquery contains window functions, we cannot push volatile quals
3174  * into it. The issue here is a bit different from DISTINCT: a volatile qual
3175  * might succeed for some rows of a window partition and fail for others,
3176  * thereby changing the partition contents and thus the window functions'
3177  * results for rows that remain.
3178  *
3179  * 5. If the subquery contains any set-returning functions in its targetlist,
3180  * we cannot push volatile quals into it. That would push them below the SRFs
3181  * and thereby change the number of times they are evaluated. Also, a
3182  * volatile qual could succeed for some SRF output rows and fail for others,
3183  * a behavior that cannot occur if it's evaluated before SRF expansion.
3184  *
3185  * In addition, we make several checks on the subquery's output columns to see
3186  * if it is safe to reference them in pushed-down quals. If output column k
3187  * is found to be unsafe to reference, we set safetyInfo->unsafeColumns[k]
3188  * to true, but we don't reject the subquery overall since column k might not
3189  * be referenced by some/all quals. The unsafeColumns[] array will be
3190  * consulted later by qual_is_pushdown_safe(). It's better to do it this way
3191  * than to make the checks directly in qual_is_pushdown_safe(), because when
3192  * the subquery involves set operations we have to check the output
3193  * expressions in each arm of the set op.
3194  *
3195  * Note: pushing quals into a DISTINCT subquery is theoretically dubious:
3196  * we're effectively assuming that the quals cannot distinguish values that
3197  * the DISTINCT's equality operator sees as equal, yet there are many
3198  * counterexamples to that assumption. However use of such a qual with a
3199  * DISTINCT subquery would be unsafe anyway, since there's no guarantee which
3200  * "equal" value will be chosen as the output value by the DISTINCT operation.
3201  * So we don't worry too much about that. Another objection is that if the
3202  * qual is expensive to evaluate, running it for each original row might cost
3203  * more than we save by eliminating rows before the DISTINCT step. But it
3204  * would be very hard to estimate that at this stage, and in practice pushdown
3205  * seldom seems to make things worse, so we ignore that problem too.
3206  *
3207  * Note: likewise, pushing quals into a subquery with window functions is a
3208  * bit dubious: the quals might remove some rows of a window partition while
3209  * leaving others, causing changes in the window functions' results for the
3210  * surviving rows. We insist that such a qual reference only partitioning
3211  * columns, but again that only protects us if the qual does not distinguish
3212  * values that the partitioning equality operator sees as equal. The risks
3213  * here are perhaps larger than for DISTINCT, since no de-duplication of rows
3214  * occurs and thus there is no theoretical problem with such a qual. But
3215  * we'll do this anyway because the potential performance benefits are very
3216  * large, and we've seen no field complaints about the longstanding comparable
3217  * behavior with DISTINCT.
3218  */
3219 static bool
3220 subquery_is_pushdown_safe(Query *subquery, Query *topquery,
3221  pushdown_safety_info *safetyInfo)
3222 {
3223  SetOperationStmt *topop;
3224 
3225  /* Check point 1 */
3226  if (subquery->limitOffset != NULL || subquery->limitCount != NULL)
3227  return false;
3228 
3229  /* Check points 3, 4, and 5 */
3230  if (subquery->distinctClause ||
3231  subquery->hasWindowFuncs ||
3232  subquery->hasTargetSRFs)
3233  safetyInfo->unsafeVolatile = true;
3234 
3235  /*
3236  * If we're at a leaf query, check for unsafe expressions in its target
3237  * list, and mark any unsafe ones in unsafeColumns[]. (Non-leaf nodes in
3238  * setop trees have only simple Vars in their tlists, so no need to check
3239  * them.)
3240  */
3241  if (subquery->setOperations == NULL)
3242  check_output_expressions(subquery, safetyInfo);
3243 
3244  /* Are we at top level, or looking at a setop component? */
3245  if (subquery == topquery)
3246  {
3247  /* Top level, so check any component queries */
3248  if (subquery->setOperations != NULL)
3249  if (!recurse_pushdown_safe(subquery->setOperations, topquery,
3250  safetyInfo))
3251  return false;
3252  }
3253  else
3254  {
3255  /* Setop component must not have more components (too weird) */
3256  if (subquery->setOperations != NULL)
3257  return false;
3258  /* Check whether setop component output types match top level */
3259  topop = castNode(SetOperationStmt, topquery->setOperations);
3260  Assert(topop);
3261  compare_tlist_datatypes(subquery->targetList,
3262  topop->colTypes,
3263  safetyInfo);
3264  }
3265  return true;
3266 }
3267 
3268 /*
3269  * Helper routine to recurse through setOperations tree
3270  */
3271 static bool
3272 recurse_pushdown_safe(Node *setOp, Query *topquery,
3273  pushdown_safety_info *safetyInfo)
3274 {
3275  if (IsA(setOp, RangeTblRef))
3276  {
3277  RangeTblRef *rtr = (RangeTblRef *) setOp;
3278  RangeTblEntry *rte = rt_fetch(rtr->rtindex, topquery->rtable);
3279  Query *subquery = rte->subquery;
3280 
3281  Assert(subquery != NULL);
3282  return subquery_is_pushdown_safe(subquery, topquery, safetyInfo);
3283  }
3284  else if (IsA(setOp, SetOperationStmt))
3285  {
3286  SetOperationStmt *op = (SetOperationStmt *) setOp;
3287 
3288  /* EXCEPT is no good (point 2 for subquery_is_pushdown_safe) */
3289  if (op->op == SETOP_EXCEPT)
3290  return false;
3291  /* Else recurse */
3292  if (!recurse_pushdown_safe(op->larg, topquery, safetyInfo))
3293  return false;
3294  if (!recurse_pushdown_safe(op->rarg, topquery, safetyInfo))
3295  return false;
3296  }
3297  else
3298  {
3299  elog(ERROR, "unrecognized node type: %d",
3300  (int) nodeTag(setOp));
3301  }
3302  return true;
3303 }
3304 
3305 /*
3306  * check_output_expressions - check subquery's output expressions for safety
3307  *
3308  * There are several cases in which it's unsafe to push down an upper-level
3309  * qual if it references a particular output column of a subquery. We check
3310  * each output column of the subquery and set unsafeColumns[k] to true if
3311  * that column is unsafe for a pushed-down qual to reference. The conditions
3312  * checked here are:
3313  *
3314  * 1. We must not push down any quals that refer to subselect outputs that
3315  * return sets, else we'd introduce functions-returning-sets into the
3316  * subquery's WHERE/HAVING quals.
3317  *
3318  * 2. We must not push down any quals that refer to subselect outputs that
3319  * contain volatile functions, for fear of introducing strange results due
3320  * to multiple evaluation of a volatile function.
3321  *
3322  * 3. If the subquery uses DISTINCT ON, we must not push down any quals that
3323  * refer to non-DISTINCT output columns, because that could change the set
3324  * of rows returned. (This condition is vacuous for DISTINCT, because then
3325  * there are no non-DISTINCT output columns, so we needn't check. Note that
3326  * subquery_is_pushdown_safe already reported that we can't use volatile
3327  * quals if there's DISTINCT or DISTINCT ON.)
3328  *
3329  * 4. If the subquery has any window functions, we must not push down quals
3330  * that reference any output columns that are not listed in all the subquery's
3331  * window PARTITION BY clauses. We can push down quals that use only
3332  * partitioning columns because they should succeed or fail identically for
3333  * every row of any one window partition, and totally excluding some
3334  * partitions will not change a window function's results for remaining
3335  * partitions. (Again, this also requires nonvolatile quals, but
3336  * subquery_is_pushdown_safe handles that.)
3337  */
3338 static void
3339 check_output_expressions(Query *subquery, pushdown_safety_info *safetyInfo)
3340 {
3341  ListCell *lc;
3342 
3343  foreach(lc, subquery->targetList)
3344  {
3345  TargetEntry *tle = (TargetEntry *) lfirst(lc);
3346 
3347  if (tle->resjunk)
3348  continue; /* ignore resjunk columns */
3349 
3350  /* We need not check further if output col is already known unsafe */
3351  if (safetyInfo->unsafeColumns[tle->resno])
3352  continue;
3353 
3354  /* Functions returning sets are unsafe (point 1) */
3355  if (subquery->hasTargetSRFs &&
3356  expression_returns_set((Node *) tle->expr))
3357  {
3358  safetyInfo->unsafeColumns[tle->resno] = true;
3359  continue;
3360  }
3361 
3362  /* Volatile functions are unsafe (point 2) */
3363  if (contain_volatile_functions((Node *) tle->expr))
3364  {
3365  safetyInfo->unsafeColumns[tle->resno] = true;
3366  continue;
3367  }
3368 
3369  /* If subquery uses DISTINCT ON, check point 3 */
3370  if (subquery->hasDistinctOn &&
3371  !targetIsInSortList(tle, InvalidOid, subquery->distinctClause))
3372  {
3373  /* non-DISTINCT column, so mark it unsafe */
3374  safetyInfo->unsafeColumns[tle->resno] = true;
3375  continue;
3376  }
3377 
3378  /* If subquery uses window functions, check point 4 */
3379  if (subquery->hasWindowFuncs &&
3380  !targetIsInAllPartitionLists(tle, subquery))
3381  {
3382  /* not present in all PARTITION BY clauses, so mark it unsafe */
3383  safetyInfo->unsafeColumns[tle->resno] = true;
3384  continue;
3385  }
3386  }
3387 }
3388 
3389 /*
3390  * For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
3391  * push quals into each component query, but the quals can only reference
3392  * subquery columns that suffer no type coercions in the set operation.
3393  * Otherwise there are possible semantic gotchas. So, we check the
3394  * component queries to see if any of them have output types different from
3395  * the top-level setop outputs. unsafeColumns[k] is set true if column k
3396  * has different type in any component.
3397  *
3398  * We don't have to care about typmods here: the only allowed difference
3399  * between set-op input and output typmods is input is a specific typmod
3400  * and output is -1, and that does not require a coercion.
3401  *
3402  * tlist is a subquery tlist.
3403  * colTypes is an OID list of the top-level setop's output column types.
3404  * safetyInfo->unsafeColumns[] is the result array.
3405  */
3406 static void
3407 compare_tlist_datatypes(List *tlist, List *colTypes,
3408  pushdown_safety_info *safetyInfo)
3409 {
3410  ListCell *l;
3411  ListCell *colType = list_head(colTypes);
3412 
3413  foreach(l, tlist)
3414  {
3415  TargetEntry *tle = (TargetEntry *) lfirst(l);
3416 
3417  if (tle->resjunk)
3418  continue; /* ignore resjunk columns */
3419  if (colType == NULL)
3420  elog(ERROR, "wrong number of tlist entries");
3421  if (exprType((Node *) tle->expr) != lfirst_oid(colType))
3422  safetyInfo->unsafeColumns[tle->resno] = true;
3423  colType = lnext(colTypes, colType);
3424  }
3425  if (colType != NULL)
3426  elog(ERROR, "wrong number of tlist entries");
3427 }
3428 
3429 /*
3430  * targetIsInAllPartitionLists
3431  * True if the TargetEntry is listed in the PARTITION BY clause
3432  * of every window defined in the query.
3433  *
3434  * It would be safe to ignore windows not actually used by any window
3435  * function, but it's not easy to get that info at this stage; and it's
3436  * unlikely to be useful to spend any extra cycles getting it, since
3437  * unreferenced window definitions are probably infrequent in practice.
3438  */
3439 static bool
3440 targetIsInAllPartitionLists(TargetEntry *tle, Query *query)
3441 {
3442  ListCell *lc;
3443 
3444  foreach(lc, query->windowClause)
3445  {
3446  WindowClause *wc = (WindowClause *) lfirst(lc);
3447 
3448  if (!targetIsInSortList(tle, InvalidOid, wc->partitionClause))
3449  return false;
3450  }
3451  return true;
3452 }
3453 
3454 /*
3455  * qual_is_pushdown_safe - is a particular qual safe to push down?
3456  *
3457  * qual is a restriction clause applying to the given subquery (whose RTE
3458  * has index rti in the parent query).
3459  *
3460  * Conditions checked here:
3461  *
3462  * 1. The qual must not contain any SubPlans (mainly because I'm not sure
3463  * it will work correctly: SubLinks will already have been transformed into
3464  * SubPlans in the qual, but not in the subquery). Note that SubLinks that
3465  * transform to initplans are safe, and will be accepted here because what
3466  * we'll see in the qual is just a Param referencing the initplan output.
3467  *
3468  * 2. If unsafeVolatile is set, the qual must not contain any volatile
3469  * functions.
3470  *
3471  * 3. If unsafeLeaky is set, the qual must not contain any leaky functions
3472  * that are passed Var nodes, and therefore might reveal values from the
3473  * subquery as side effects.
3474  *
3475  * 4. The qual must not refer to the whole-row output of the subquery
3476  * (since there is no easy way to name that within the subquery itself).
3477  *
3478  * 5. The qual must not refer to any subquery output columns that were
3479  * found to be unsafe to reference by subquery_is_pushdown_safe().
3480  */
3481 static bool
3482 qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
3483  pushdown_safety_info *safetyInfo)
3484 {
3485  bool safe = true;
3486  List *vars;
3487  ListCell *vl;
3488 
3489  /* Refuse subselects (point 1) */
3490  if (contain_subplans(qual))
3491  return false;
3492 
3493  /* Refuse volatile quals if we found they'd be unsafe (point 2) */
3494  if (safetyInfo->unsafeVolatile &&
3495  contain_volatile_functions(qual))
3496  return false;
3497 
3498  /* Refuse leaky quals if told to (point 3) */
3499  if (safetyInfo->unsafeLeaky &&
3500  contain_leaked_vars(qual))
3501  return false;
3502 
3503  /*
3504  * It would be unsafe to push down window function calls, but at least for
3505  * the moment we could never see any in a qual anyhow. (The same applies
3506  * to aggregates, which we check for in pull_var_clause below.)
3507  */
3508  Assert(!contain_window_function(qual));
3509 
3510  /*
3511  * Examine all Vars used in clause. Since it's a restriction clause, all
3512  * such Vars must refer to subselect output columns ... unless this is
3513  * part of a LATERAL subquery, in which case there could be lateral
3514  * references.
3515  */
3516  vars = pull_var_clause(qual, PVC_INCLUDE_PLACEHOLDERS);
3517  foreach(vl, vars)
3518  {
3519  Var *var = (Var *) lfirst(vl);
3520 
3521  /*
3522  * XXX Punt if we find any PlaceHolderVars in the restriction clause.
3523  * It's not clear whether a PHV could safely be pushed down, and even
3524  * less clear whether such a situation could arise in any cases of
3525  * practical interest anyway. So for the moment, just refuse to push
3526  * down.
3527  */
3528  if (!IsA(var, Var))
3529  {
3530  safe = false;
3531  break;
3532  }
3533 
3534  /*
3535  * Punt if we find any lateral references. It would be safe to push
3536  * these down, but we'd have to convert them into outer references,
3537  * which subquery_push_qual lacks the infrastructure to do. The case
3538  * arises so seldom that it doesn't seem worth working hard on.
3539  */
3540  if (var->varno != rti)
3541  {
3542  safe = false;
3543  break;
3544  }
3545 
3546  /* Subqueries have no system columns */
3547  Assert(var->varattno >= 0);
3548 
3549  /* Check point 4 */
3550  if (var->varattno == 0)
3551  {
3552  safe = false;
3553  break;
3554  }
3555 
3556  /* Check point 5 */
3557  if (safetyInfo->unsafeColumns[var->varattno])
3558  {
3559  safe = false;
3560  break;
3561  }
3562  }
3563 
3564  list_free(vars);
3565 
3566  return safe;
3567 }
3568 
3569 /*
3570  * subquery_push_qual - push down a qual that we have determined is safe
3571  */
3572 static void
3573 subquery_push_qual(Query *subquery, RangeTblEntry *rte, Index rti, Node *qual)
3574 {
3575  if (subquery->setOperations != NULL)
3576  {
3577  /* Recurse to push it separately to each component query */
3578  recurse_push_qual(subquery->setOperations, subquery,
3579  rte, rti, qual);
3580  }
3581  else
3582  {
3583  /*
3584  * We need to replace Vars in the qual (which must refer to outputs of
3585  * the subquery) with copies of the subquery's targetlist expressions.
3586  * Note that at this point, any uplevel Vars in the qual should have
3587  * been replaced with Params, so they need no work.
3588  *
3589  * This step also ensures that when we are pushing into a setop tree,
3590  * each component query gets its own copy of the qual.
3591  */
3592  qual = ReplaceVarsFromTargetList(qual, rti, 0, rte,
3593  subquery->targetList,
3594  REPLACEVARS_REPORT_ERROR, 0,
3595  &subquery->hasSubLinks);
3596 
3597  /*
3598  * Now attach the qual to the proper place: normally WHERE, but if the
3599  * subquery uses grouping or aggregation, put it in HAVING (since the
3600  * qual really refers to the group-result rows).
3601  */
3602  if (subquery->hasAggs || subquery->groupClause || subquery->groupingSets || subquery->havingQual)
3603  subquery->havingQual = make_and_qual(subquery->havingQual, qual);
3604  else
3605  subquery->jointree->quals =
3606  make_and_qual(subquery->jointree->quals, qual);
3607 
3608  /*
3609  * We need not change the subquery's hasAggs or hasSubLinks flags,
3610  * since we can't be pushing down any aggregates that weren't there
3611  * before, and we don't push down subselects at all.
3612  */
3613  }
3614 }
3615 
3616 /*
3617  * Helper routine to recurse through setOperations tree
3618  */
3619 static void
3620 recurse_push_qual(Node *setOp, Query *topquery,
3621  RangeTblEntry *rte, Index rti, Node *qual)
3622 {
3623  if (IsA(setOp, RangeTblRef))
3624  {
3625  RangeTblRef *rtr = (RangeTblRef *) setOp;
3626  RangeTblEntry *subrte = rt_fetch(rtr->rtindex, topquery->rtable);
3627  Query *subquery = subrte->subquery;
3628 
3629  Assert(subquery != NULL);
3630  subquery_push_qual(subquery, rte, rti, qual);
3631  }
3632  else if (IsA(setOp, SetOperationStmt))
3633  {
3634  SetOperationStmt *op = (SetOperationStmt *) setOp;
3635 
3636  recurse_push_qual(op->larg, topquery, rte, rti, qual);
3637  recurse_push_qual(op->rarg, topquery, rte, rti, qual);
3638  }
3639  else
3640  {
3641  elog(ERROR, "unrecognized node type: %d",
3642  (int) nodeTag(setOp));
3643  }
3644 }
3645 
3646 /*****************************************************************************
3647  * SIMPLIFYING SUBQUERY TARGETLISTS
3648  *****************************************************************************/
3649 
3650 /*
3651  * remove_unused_subquery_outputs
3652  * Remove subquery targetlist items we don't need
3653  *
3654  * It's possible, even likely, that the upper query does not read all the
3655  * output columns of the subquery. We can remove any such outputs that are
3656  * not needed by the subquery itself (e.g., as sort/group columns) and do not
3657  * affect semantics otherwise (e.g., volatile functions can't be removed).
3658  * This is useful not only because we might be able to remove expensive-to-
3659  * compute expressions, but because deletion of output columns might allow
3660  * optimizations such as join removal to occur within the subquery.
3661  *
3662  * To avoid affecting column numbering in the targetlist, we don't physically
3663  * remove unused tlist entries, but rather replace their expressions with NULL
3664  * constants. This is implemented by modifying subquery->targetList.
3665  */
3666 static void
3667 remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel)
3668 {
3669  Bitmapset *attrs_used = NULL;
3670  ListCell *lc;
3671 
3672  /*
3673  * Do nothing if subquery has UNION/INTERSECT/EXCEPT: in principle we
3674  * could update all the child SELECTs' tlists, but it seems not worth the
3675  * trouble presently.
3676  */
3677  if (subquery->setOperations)
3678  return;
3679 
3680  /*
3681  * If subquery has regular DISTINCT (not DISTINCT ON), we're wasting our
3682  * time: all its output columns must be used in the distinctClause.
3683  */
3684  if (subquery->distinctClause && !subquery->hasDistinctOn)
3685  return;
3686 
3687  /*
3688  * Collect a bitmap of all the output column numbers used by the upper
3689  * query.
3690  *
3691  * Add all the attributes needed for joins or final output. Note: we must
3692  * look at rel's targetlist, not the attr_needed data, because attr_needed
3693  * isn't computed for inheritance child rels, cf set_append_rel_size().
3694  * (XXX might be worth changing that sometime.)
3695  */
3696  pull_varattnos((Node *) rel->reltarget->exprs, rel->relid, &attrs_used);
3697 
3698  /* Add all the attributes used by un-pushed-down restriction clauses. */
3699  foreach(lc, rel->baserestrictinfo)
3700  {
3701  RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
3702 
3703  pull_varattnos((Node *) rinfo->clause, rel->relid, &attrs_used);
3704  }
3705 
3706  /*
3707  * If there's a whole-row reference to the subquery, we can't remove
3708  * anything.
3709  */
3710  if (bms_is_member(0 - FirstLowInvalidHeapAttributeNumber, attrs_used))
3711  return;
3712 
3713  /*
3714  * Run through the tlist and zap entries we don't need. It's okay to
3715  * modify the tlist items in-place because set_subquery_pathlist made a
3716  * copy of the subquery.
3717  */
3718  foreach(lc, subquery->targetList)
3719  {
3720  TargetEntry *tle = (TargetEntry *) lfirst(lc);
3721  Node *texpr = (Node *) tle->expr;
3722 
3723  /*
3724  * If it has a sortgroupref number, it's used in some sort/group
3725  * clause so we'd better not remove it. Also, don't remove any
3726  * resjunk columns, since their reason for being has nothing to do
3727  * with anybody reading the subquery's output. (It's likely that
3728  * resjunk columns in a sub-SELECT would always have ressortgroupref
3729  * set, but even if they don't, it seems imprudent to remove them.)
3730  */
3731  if (tle->ressortgroupref || tle->resjunk)
3732  continue;
3733 
3734  /*
3735  * If it's used by the upper query, we can't remove it.
3736  */
3737  if (bms_is_member(tle->resno - FirstLowInvalidHeapAttributeNumber,
3738  attrs_used))
3739  continue;
3740 
3741  /*
3742  * If it contains a set-returning function, we can't remove it since
3743  * that could change the number of rows returned by the subquery.
3744  */
3745  if (subquery->hasTargetSRFs &&
3746  expression_returns_set(texpr))
3747  continue;
3748 
3749  /*
3750  * If it contains volatile functions, we daren't remove it for fear
3751  * that the user is expecting their side-effects to happen.
3752  */
3753  if (contain_volatile_functions(texpr))
3754  continue;
3755 
3756  /*
3757  * OK, we don't need it. Replace the expression with a NULL constant.
3758  * Preserve the exposed type of the expression, in case something
3759  * looks at the rowtype of the subquery's result.
3760  */
3761  tle->expr = (Expr *) makeNullConst(exprType(texpr),
3762  exprTypmod(texpr),
3763  exprCollation(texpr));
3764  }
3765 }
3766 
3767 /*
3768  * create_partial_bitmap_paths
3769  * Build partial bitmap heap path for the relation
3770  */
3771 void
3772 create_partial_bitmap_paths(PlannerInfo *root, RelOptInfo *rel,
3773  Path *bitmapqual)
3774 {
3775  int parallel_workers;
3776  double pages_fetched;
3777 
3778  /* Compute heap pages for bitmap heap scan */
3779  pages_fetched = compute_bitmap_pages(root, rel, bitmapqual, 1.0,
3780  NULL, NULL);
3781 
3782  parallel_workers = compute_parallel_worker(rel, pages_fetched, -1,
3783  max_parallel_workers_per_gather);
3784 
3785  if (parallel_workers <= 0)
3786  return;
3787 
3788  add_partial_path(rel, (Path *) create_bitmap_heap_path(root, rel,
3789  bitmapqual, rel->lateral_relids, 1.0, parallel_workers));
3790 }
3791 
3792 /*
3793  * Compute the number of parallel workers that should be used to scan a
3794  * relation. We compute the parallel workers based on the size of the heap to
3795  * be scanned and the size of the index to be scanned, then choose a minimum
3796  * of those.
3797  *
3798  * "heap_pages" is the number of pages from the table that we expect to scan, or
3799  * -1 if we don't expect to scan any.
3800  *
3801  * "index_pages" is the number of pages from the index that we expect to scan, or
3802  * -1 if we don't expect to scan any.
3803  *
3804  * "max_workers" is caller's limit on the number of workers. This typically
3805  * comes from a GUC.
3806  */
3807 int
3808 compute_parallel_worker(RelOptInfo *rel, double heap_pages, double index_pages,
3809  int max_workers)
3810 {
3811  int parallel_workers = 0;
3812 
3813  /*
3814  * If the user has set the parallel_workers reloption, use that; otherwise
3815  * select a default number of workers.
3816  */
3817  if (rel->rel_parallel_workers != -1)
3818  parallel_workers = rel->rel_parallel_workers;
3819  else
3820  {
3821  /*
3822  * If the number of pages being scanned is insufficient to justify a
3823  * parallel scan, just return zero ... unless it's an inheritance
3824  * child. In that case, we want to generate a parallel path here
3825  * anyway. It might not be worthwhile just for this relation, but
3826  * when combined with all of its inheritance siblings it may well pay
3827  * off.
3828  */
3829  if (rel->reloptkind == RELOPT_BASEREL &&
3830  ((heap_pages >= 0 && heap_pages < min_parallel_table_scan_size) ||
3831  (index_pages >= 0 && index_pages < min_parallel_index_scan_size)))
3832  return 0;
3833 
3834  if (heap_pages >= 0)
3835  {
3836  int heap_parallel_threshold;
3837  int heap_parallel_workers = 1;
3838 
3839  /*
3840  * Select the number of workers based on the log of the size of
3841  * the relation. This probably needs to be a good deal more
3842  * sophisticated, but we need something here for now. Note that
3843  * the upper limit of the min_parallel_table_scan_size GUC is
3844  * chosen to prevent overflow here.
3845  */
3846  heap_parallel_threshold = Max(min_parallel_table_scan_size, 1);
3847  while (heap_pages >= (BlockNumber) (heap_parallel_threshold * 3))
3848  {
3849  heap_parallel_workers++;
3850  heap_parallel_threshold *= 3;
3851  if (heap_parallel_threshold > INT_MAX / 3)
3852  break; /* avoid overflow */
3853  }
3854 
3855  parallel_workers = heap_parallel_workers;
3856  }
3857 
3858  if (index_pages >= 0)
3859  {
3860  int index_parallel_workers = 1;
3861  int index_parallel_threshold;
3862 
3863  /* same calculation as for heap_pages above */
3864  index_parallel_threshold = Max(min_parallel_index_scan_size, 1);
3865  while (index_pages >= (BlockNumber) (index_parallel_threshold * 3))
3866  {
3867  index_parallel_workers++;
3868  index_parallel_threshold *= 3;
3869  if (index_parallel_threshold > INT_MAX / 3)
3870  break; /* avoid overflow */
3871  }
3872 
3873  if (parallel_workers > 0)
3874  parallel_workers = Min(parallel_workers, index_parallel_workers);
3875  else
3876  parallel_workers = index_parallel_workers;
3877  }
3878  }
3879 
3880  /* In no case use more than caller supplied maximum number of workers */
3881  parallel_workers = Min(parallel_workers, max_workers);
3882 
3883  return parallel_workers;
3884 }
3885 
3886 /*
3887  * generate_partitionwise_join_paths
3888  * Create paths representing partitionwise join for given partitioned
3889  * join relation.
3890  *
3891  * This must not be called until after we are done adding paths for all
3892  * child-joins. Otherwise, add_path might delete a path to which some path
3893  * generated here has a reference.
3894  */
3895 void
3896 generate_partitionwise_join_paths(PlannerInfo *root, RelOptInfo *rel)
3897 {
3898  List *live_children = NIL;
3899  int cnt_parts;
3900  int num_parts;
3901  RelOptInfo **part_rels;
3902 
3903  /* Handle only join relations here. */
3904  if (!IS_JOIN_REL(rel))
3905  return;
3906 
3907  /* We've nothing to do if the relation is not partitioned. */
3908  if (!IS_PARTITIONED_REL(rel))
3909  return;
3910 
3911  /* The relation should have consider_partitionwise_join set. */
3912  Assert(rel->consider_partitionwise_join);
3913 
3914  /* Guard against stack overflow due to overly deep partition hierarchy. */
3915  check_stack_depth();
3916 
3917  num_parts = rel->nparts;
3918  part_rels = rel->part_rels;
3919 
3920  /* Collect non-dummy child-joins. */
3921  for (cnt_parts = 0; cnt_parts < num_parts; cnt_parts++)
3922  {
3923  RelOptInfo *child_rel = part_rels[cnt_parts];
3924 
3925  /* If it's been pruned entirely, it's certainly dummy. */
3926  if (child_rel == NULL)
3927  continue;
3928 
3929  /* Add partitionwise join paths for partitioned child-joins. */
3930  generate_partitionwise_join_paths(root, child_rel);
3931 
3932  set_cheapest(child_rel);
3933 
3934  /* Dummy children will not be scanned, so ignore those. */
3935  if (IS_DUMMY_REL(child_rel))
3936  continue;
3937 
3938 #ifdef OPTIMIZER_DEBUG
3939  debug_print_rel(root, child_rel);
3940 #endif
3941 
3942  live_children = lappend(live_children, child_rel);
3943  }
3944 
3945  /* If all child-joins are dummy, parent join is also dummy. */
3946  if (!live_children)
3947  {
3948  mark_dummy_rel(rel);
3949  return;
3950  }
3951 
3952  /* Build additional paths for this rel from child-join paths. */
3953  add_paths_to_append_rel(root, rel, live_children);
3954  list_free(live_children);
3955 }
3956 
3957 
3958 /*****************************************************************************
3959  * DEBUG SUPPORT
3960  *****************************************************************************/
3961 
3962 #ifdef OPTIMIZER_DEBUG
3963 
3964 static void
3965 print_relids(PlannerInfo *root, Relids relids)
3966 {
3967  int x;
3968  bool first = true;
3969 
3970  x = -1;
3971  while ((x = bms_next_member(relids, x)) >= 0)
3972  {
3973  if (!first)
3974  printf(" ");
3975  if (x < root->simple_rel_array_size &&
3976  root->simple_rte_array[x])
3977  printf("%s", root->simple_rte_array[x]->eref->aliasname);
3978  else
3979  printf("%d", x);
3980  first = false;
3981  }
3982 }
3983 
3984 static void
3985 print_restrictclauses(PlannerInfo *root, List *clauses)
3986 {
3987  ListCell *l;
3988 
3989  foreach(l, clauses)
3990  {
3991  RestrictInfo *c = lfirst(l);
3992 
3993  print_expr((Node *) c->clause, root->parse->rtable);
3994  if (lnext(clauses, l))
3995  printf(", ");
3996  }
3997 }
3998 
3999 static void
4000 print_path(PlannerInfo *root, Path *path, int indent)
4001 {
4002  const char *ptype;
4003  bool join = false;
4004  Path *subpath = NULL;
4005  int i;
4006 
4007  switch (nodeTag(path))
4008  {
4009  case T_Path:
4010  switch (path->pathtype)
4011  {
4012  case T_SeqScan:
4013  ptype = "SeqScan";
4014  break;
4015  case T_SampleScan:
4016  ptype = "SampleScan";
4017  break;
4018  case T_FunctionScan:
4019  ptype = "FunctionScan";
4020  break;
4021  case T_TableFuncScan:
4022  ptype = "TableFuncScan";
4023  break;
4024  case T_ValuesScan:
4025  ptype = "ValuesScan";
4026  break;
4027  case T_CteScan:
4028  ptype = "CteScan";
4029  break;
4030  case T_NamedTuplestoreScan:
4031  ptype = "NamedTuplestoreScan";
4032  break;
4033  case T_Result:
4034  ptype = "Result";
4035  break;
4036  case T_WorkTableScan:
4037  ptype = "WorkTableScan";
4038  break;
4039  default:
4040  ptype = "???Path";
4041  break;
4042  }
4043  break;
4044  case T_IndexPath:
4045  ptype = "IdxScan";
4046  break;
4047  case T_BitmapHeapPath:
4048  ptype = "BitmapHeapScan";
4049  break;
4050  case T_BitmapAndPath:
4051  ptype = "BitmapAndPath";
4052  break;
4053  case T_BitmapOrPath:
4054  ptype = "BitmapOrPath";
4055  break;
4056  case T_TidPath:
4057  ptype = "TidScan";
4058  break;
4059  case T_SubqueryScanPath:
4060  ptype = "SubqueryScan";
4061  break;
4062  case T_ForeignPath:
4063  ptype = "ForeignScan";
4064  break;
4065  case T_CustomPath:
4066  ptype = "CustomScan";
4067  break;
4068  case T_NestPath:
4069  ptype = "NestLoop";
4070  join = true;
4071  break;
4072  case T_MergePath:
4073  ptype = "MergeJoin";
4074  join = true;
4075  break;
4076  case T_HashPath:
4077  ptype = "HashJoin";
4078  join = true;
4079  break;
4080  case T_AppendPath:
4081  ptype = "Append";
4082  break;
4083  case T_MergeAppendPath:
4084  ptype = "MergeAppend";
4085  break;
4086  case T_GroupResultPath:
4087  ptype = "GroupResult";
4088  break;
4089  case T_MaterialPath:
4090  ptype = "Material";
4091  subpath = ((MaterialPath *) path)->subpath;
4092  break;
4093  case T_UniquePath:
4094  ptype = "Unique";
4095  subpath = ((UniquePath *) path)->subpath;
4096  break;
4097  case T_GatherPath:
4098  ptype = "Gather";
4099  subpath = ((GatherPath *) path)->subpath;
4100  break;
4101  case T_GatherMergePath:
4102  ptype = "GatherMerge";
4103  subpath = ((GatherMergePath *) path)->subpath;
4104  break;
4105  case T_ProjectionPath:
4106  ptype = "Projection";
4107  subpath = ((ProjectionPath *) path)->subpath;
4108  break;
4109  case T_ProjectSetPath:
4110  ptype = "ProjectSet";
4111  subpath = ((ProjectSetPath *) path)->subpath;
4112  break;
4113  case T_SortPath:
4114  ptype = "Sort";
4115  subpath = ((SortPath *) path)->subpath;
4116  break;
4117  case T_IncrementalSortPath:
4118  ptype = "IncrementalSort";
4119  subpath = ((SortPath *) path)->subpath;
4120  break;
4121  case T_GroupPath:
4122  ptype = "Group";
4123  subpath = ((GroupPath *) path)->subpath;
4124  break;
4125  case T_UpperUniquePath:
4126  ptype = "UpperUnique";
4127  subpath = ((UpperUniquePath *) path)->subpath;
4128  break;
4129  case T_AggPath:
4130  ptype = "Agg";
4131  subpath = ((AggPath *) path)->subpath;
4132  break;
4133  case T_GroupingSetsPath:
4134  ptype = "GroupingSets";
4135  subpath = ((GroupingSetsPath *) path)->subpath;
4136  break;
4137  case T_MinMaxAggPath:
4138  ptype = "MinMaxAgg";
4139  break;
4140  case T_WindowAggPath:
4141  ptype = "WindowAgg";
4142  subpath = ((WindowAggPath *) path)->subpath;
4143  break;
4144  case T_SetOpPath:
4145  ptype = "SetOp";
4146  subpath = ((SetOpPath *) path)->subpath;
4147  break;
4148  case T_RecursiveUnionPath:
4149  ptype = "RecursiveUnion";
4150  break;
4151  case T_LockRowsPath:
4152  ptype = "LockRows";
4153  subpath = ((LockRowsPath *) path)->subpath;
4154  break;
4155  case T_ModifyTablePath:
4156  ptype = "ModifyTable";
4157  break;
4158  case T_LimitPath:
4159  ptype = "Limit";
4160  subpath = ((LimitPath *) path)->subpath;
4161  break;
4162  default:
4163  ptype = "???Path";
4164  break;
4165  }
4166 
4167  for (i = 0; i < indent; i++)
4168  printf("\t");
4169  printf("%s", ptype);
4170 
4171  if (path->parent)
4172  {
4173  printf("(");
4174  print_relids(root, path->parent->relids);
4175  printf(")");
4176  }
4177  if (path->param_info)
4178  {
4179  printf(" required_outer (");
4180  print_relids(root, path->param_info->ppi_req_outer);
4181  printf(")");
4182  }
4183  printf(" rows=%.0f cost=%.2f..%.2f\n",
4184  path->rows, path->startup_cost, path->total_cost);
4185 
4186  if (path->pathkeys)
4187  {
4188  for (i = 0; i < indent; i++)
4189  printf("\t");
4190  printf(" pathkeys: ");
4191  print_pathkeys(path->pathkeys, root->parse->rtable);
4192  }
4193 
4194  if (join)
4195  {
4196  JoinPath *jp = (JoinPath *) path;
4197 
4198  for (i = 0; i < indent; i++)
4199  printf("\t");
4200  printf(" clauses: ");
4201  print_restrictclauses(root, jp->joinrestrictinfo);
4202  printf("\n");
4203 
4204  if (IsA(path, MergePath))
4205  {
4206  MergePath *mp = (MergePath *) path;
4207 
4208  for (i = 0; i < indent; i++)
4209  printf("\t");
4210  printf(" sortouter=%d sortinner=%d materializeinner=%d\n",
4211  ((mp->outersortkeys) ? 1 : 0),
4212  ((mp->innersortkeys) ? 1 : 0),
4213  ((mp->materialize_inner) ? 1 : 0));
4214  }
4215 
4216  print_path(root, jp->outerjoinpath, indent + 1);
4217  print_path(root, jp->innerjoinpath, indent + 1);
4218  }
4219 
4220  if (subpath)
4221  print_path(root, subpath, indent + 1);
4222 }
4223 
4224 void
4225 debug_print_rel(PlannerInfo *root, RelOptInfo *rel)
4226 {
4227  ListCell *l;
4228 
4229  printf("RELOPTINFO (");
4230  print_relids(root, rel->relids);
4231  printf("): rows=%.0f width=%d\n", rel->rows, rel->reltarget->width);
4232 
4233  if (rel->baserestrictinfo)
4234  {
4235  printf("\tbaserestrictinfo: ");
4236  print_restrictclauses(root, rel->baserestrictinfo);
4237  printf("\n");
4238  }
4239 
4240  if (rel->joininfo)
4241  {
4242  printf("\tjoininfo: ");
4243  print_restrictclauses(root, rel->joininfo);
4244  printf("\n");
4245  }
4246 
4247  printf("\tpath list:\n");
4248  foreach(l, rel->pathlist)
4249  print_path(root, lfirst(l), 1);
4250  if (rel->cheapest_parameterized_paths)
4251  {
4252  printf("\n\tcheapest parameterized paths:\n");
4253  foreach(l, rel->cheapest_parameterized_paths)
4254  print_path(root, lfirst(l), 1);
4255  }
4256  if (rel->cheapest_startup_path)
4257  {
4258  printf("\n\tcheapest startup path:\n");
4259  print_path(root, rel->cheapest_startup_path, 1);
4260  }
4261  if (rel->cheapest_total_path)
4262  {
4263  printf("\n\tcheapest total path:\n");
4264  print_path(root, rel->cheapest_total_path, 1);
4265  }
4266  printf("\n");
4267  fflush(stdout);
4268 }
4269 
4270 #endif /* OPTIMIZER_DEBUG */
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Definition: pathnodes.h:733
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struct TableSampleClause * tablesample
Definition: parsenodes.h:1006
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Definition: attnum.h:21
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static void set_rel_size(PlannerInfo *root, RelOptInfo *rel, Index rti, RangeTblEntry *rte)
Definition: allpaths.c:361
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List * subplan_params
Definition: pathnodes.h:710
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Definition: planner.c:597
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Path * create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer, int parallel_workers)
Definition: pathnode.c:929
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Definition: costsize.c:5731
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Definition: ltree_op.c:241
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#define lfirst_oid(lc)
Definition: pg_list.h:192
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bool bms_equal(const Bitmapset *a, const Bitmapset *b)
Definition: bitmapset.c:94
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static struct subre * parse(struct vars *, int, int, struct state *, struct state *)
Definition: regcomp.c:648
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Definition: appendinfo.c:194
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Definition: c.h:324
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Definition: pathnode.c:1046
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Definition: pathnode.c:2047
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static void set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
Definition: allpaths.c:2626
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Definition: pathnode.c:2022
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Definition: pathnodes.h:696