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prepjointree.c
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1 /*-------------------------------------------------------------------------
2  *
3  * prepjointree.c
4  * Planner preprocessing for subqueries and join tree manipulation.
5  *
6  * NOTE: the intended sequence for invoking these operations is
7  * replace_empty_jointree
8  * pull_up_sublinks
9  * preprocess_function_rtes
10  * pull_up_subqueries
11  * flatten_simple_union_all
12  * do expression preprocessing (including flattening JOIN alias vars)
13  * reduce_outer_joins
14  * remove_useless_result_rtes
15  *
16  *
17  * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
18  * Portions Copyright (c) 1994, Regents of the University of California
19  *
20  *
21  * IDENTIFICATION
22  * src/backend/optimizer/prep/prepjointree.c
23  *
24  *-------------------------------------------------------------------------
25  */
26 #include "postgres.h"
27 
28 #include "catalog/pg_type.h"
29 #include "funcapi.h"
30 #include "nodes/makefuncs.h"
31 #include "nodes/nodeFuncs.h"
32 #include "optimizer/clauses.h"
33 #include "optimizer/optimizer.h"
34 #include "optimizer/placeholder.h"
35 #include "optimizer/prep.h"
36 #include "optimizer/subselect.h"
37 #include "optimizer/tlist.h"
38 #include "parser/parse_relation.h"
39 #include "parser/parsetree.h"
40 #include "rewrite/rewriteManip.h"
41 
42 
43 typedef struct pullup_replace_vars_context
44 {
45  PlannerInfo *root;
46  List *targetlist; /* tlist of subquery being pulled up */
47  RangeTblEntry *target_rte; /* RTE of subquery */
48  Relids relids; /* relids within subquery, as numbered after
49  * pullup (set only if target_rte->lateral) */
50  bool *outer_hasSubLinks; /* -> outer query's hasSubLinks */
51  int varno; /* varno of subquery */
52  bool need_phvs; /* do we need PlaceHolderVars? */
53  bool wrap_non_vars; /* do we need 'em on *all* non-Vars? */
54  Node **rv_cache; /* cache for results with PHVs */
55 } pullup_replace_vars_context;
56 
57 typedef struct reduce_outer_joins_state
58 {
59  Relids relids; /* base relids within this subtree */
60  bool contains_outer; /* does subtree contain outer join(s)? */
61  List *sub_states; /* List of states for subtree components */
62 } reduce_outer_joins_state;
63 
64 static Node *pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
65  Relids *relids);
66 static Node *pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
67  Node **jtlink1, Relids available_rels1,
68  Node **jtlink2, Relids available_rels2);
69 static Node *pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
70  JoinExpr *lowest_outer_join,
71  JoinExpr *lowest_nulling_outer_join,
72  AppendRelInfo *containing_appendrel);
73 static Node *pull_up_simple_subquery(PlannerInfo *root, Node *jtnode,
74  RangeTblEntry *rte,
75  JoinExpr *lowest_outer_join,
76  JoinExpr *lowest_nulling_outer_join,
77  AppendRelInfo *containing_appendrel);
78 static Node *pull_up_simple_union_all(PlannerInfo *root, Node *jtnode,
79  RangeTblEntry *rte);
80 static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root,
81  int parentRTindex, Query *setOpQuery,
82  int childRToffset);
83 static void make_setop_translation_list(Query *query, Index newvarno,
84  AppendRelInfo *appinfo);
85 static bool is_simple_subquery(Query *subquery, RangeTblEntry *rte,
86  JoinExpr *lowest_outer_join);
87 static Node *pull_up_simple_values(PlannerInfo *root, Node *jtnode,
88  RangeTblEntry *rte);
89 static bool is_simple_values(PlannerInfo *root, RangeTblEntry *rte);
90 static Node *pull_up_constant_function(PlannerInfo *root, Node *jtnode,
91  RangeTblEntry *rte,
92  JoinExpr *lowest_nulling_outer_join,
93  AppendRelInfo *containing_appendrel);
94 static bool is_simple_union_all(Query *subquery);
95 static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery,
96  List *colTypes);
97 static bool is_safe_append_member(Query *subquery);
98 static bool jointree_contains_lateral_outer_refs(Node *jtnode, bool restricted,
99  Relids safe_upper_varnos);
100 static void perform_pullup_replace_vars(PlannerInfo *root,
101  pullup_replace_vars_context *rvcontext,
102  JoinExpr *lowest_nulling_outer_join,
103  AppendRelInfo *containing_appendrel);
104 static void replace_vars_in_jointree(Node *jtnode,
105  pullup_replace_vars_context *context,
106  JoinExpr *lowest_nulling_outer_join);
107 static Node *pullup_replace_vars(Node *expr,
108  pullup_replace_vars_context *context);
109 static Node *pullup_replace_vars_callback(Var *var,
110  replace_rte_variables_context *context);
111 static Query *pullup_replace_vars_subquery(Query *query,
112  pullup_replace_vars_context *context);
113 static reduce_outer_joins_state *reduce_outer_joins_pass1(Node *jtnode);
114 static void reduce_outer_joins_pass2(Node *jtnode,
115  reduce_outer_joins_state *state,
116  PlannerInfo *root,
117  Relids nonnullable_rels,
118  List *nonnullable_vars,
119  List *forced_null_vars);
120 static Node *remove_useless_results_recurse(PlannerInfo *root, Node *jtnode);
121 static int get_result_relid(PlannerInfo *root, Node *jtnode);
122 static void remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc);
123 static bool find_dependent_phvs(PlannerInfo *root, int varno);
124 static bool find_dependent_phvs_in_jointree(PlannerInfo *root,
125  Node *node, int varno);
126 static void substitute_phv_relids(Node *node,
127  int varno, Relids subrelids);
128 static void fix_append_rel_relids(List *append_rel_list, int varno,
129  Relids subrelids);
130 static Node *find_jointree_node_for_rel(Node *jtnode, int relid);
131 
132 
133 /*
134  * replace_empty_jointree
135  * If the Query's jointree is empty, replace it with a dummy RTE_RESULT
136  * relation.
137  *
138  * By doing this, we can avoid a bunch of corner cases that formerly existed
139  * for SELECTs with omitted FROM clauses. An example is that a subquery
140  * with empty jointree previously could not be pulled up, because that would
141  * have resulted in an empty relid set, making the subquery not uniquely
142  * identifiable for join or PlaceHolderVar processing.
143  *
144  * Unlike most other functions in this file, this function doesn't recurse;
145  * we rely on other processing to invoke it on sub-queries at suitable times.
146  */
147 void
148 replace_empty_jointree(Query *parse)
149 {
150  RangeTblEntry *rte;
151  Index rti;
152  RangeTblRef *rtr;
153 
154  /* Nothing to do if jointree is already nonempty */
155  if (parse->jointree->fromlist != NIL)
156  return;
157 
158  /* We mustn't change it in the top level of a setop tree, either */
159  if (parse->setOperations)
160  return;
161 
162  /* Create suitable RTE */
163  rte = makeNode(RangeTblEntry);
164  rte->rtekind = RTE_RESULT;
165  rte->eref = makeAlias("*RESULT*", NIL);
166 
167  /* Add it to rangetable */
168  parse->rtable = lappend(parse->rtable, rte);
169  rti = list_length(parse->rtable);
170 
171  /* And jam a reference into the jointree */
172  rtr = makeNode(RangeTblRef);
173  rtr->rtindex = rti;
174  parse->jointree->fromlist = list_make1(rtr);
175 }
176 
177 /*
178  * pull_up_sublinks
179  * Attempt to pull up ANY and EXISTS SubLinks to be treated as
180  * semijoins or anti-semijoins.
181  *
182  * A clause "foo op ANY (sub-SELECT)" can be processed by pulling the
183  * sub-SELECT up to become a rangetable entry and treating the implied
184  * comparisons as quals of a semijoin. However, this optimization *only*
185  * works at the top level of WHERE or a JOIN/ON clause, because we cannot
186  * distinguish whether the ANY ought to return FALSE or NULL in cases
187  * involving NULL inputs. Also, in an outer join's ON clause we can only
188  * do this if the sublink is degenerate (ie, references only the nullable
189  * side of the join). In that case it is legal to push the semijoin
190  * down into the nullable side of the join. If the sublink references any
191  * nonnullable-side variables then it would have to be evaluated as part
192  * of the outer join, which makes things way too complicated.
193  *
194  * Under similar conditions, EXISTS and NOT EXISTS clauses can be handled
195  * by pulling up the sub-SELECT and creating a semijoin or anti-semijoin.
196  *
197  * This routine searches for such clauses and does the necessary parsetree
198  * transformations if any are found.
199  *
200  * This routine has to run before preprocess_expression(), so the quals
201  * clauses are not yet reduced to implicit-AND format, and are not guaranteed
202  * to be AND/OR-flat either. That means we need to recursively search through
203  * explicit AND clauses. We stop as soon as we hit a non-AND item.
204  */
205 void
206 pull_up_sublinks(PlannerInfo *root)
207 {
208  Node *jtnode;
209  Relids relids;
210 
211  /* Begin recursion through the jointree */
212  jtnode = pull_up_sublinks_jointree_recurse(root,
213  (Node *) root->parse->jointree,
214  &relids);
215 
216  /*
217  * root->parse->jointree must always be a FromExpr, so insert a dummy one
218  * if we got a bare RangeTblRef or JoinExpr out of the recursion.
219  */
220  if (IsA(jtnode, FromExpr))
221  root->parse->jointree = (FromExpr *) jtnode;
222  else
223  root->parse->jointree = makeFromExpr(list_make1(jtnode), NULL);
224 }
225 
226 /*
227  * Recurse through jointree nodes for pull_up_sublinks()
228  *
229  * In addition to returning the possibly-modified jointree node, we return
230  * a relids set of the contained rels into *relids.
231  */
232 static Node *
233 pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
234  Relids *relids)
235 {
236  if (jtnode == NULL)
237  {
238  *relids = NULL;
239  }
240  else if (IsA(jtnode, RangeTblRef))
241  {
242  int varno = ((RangeTblRef *) jtnode)->rtindex;
243 
244  *relids = bms_make_singleton(varno);
245  /* jtnode is returned unmodified */
246  }
247  else if (IsA(jtnode, FromExpr))
248  {
249  FromExpr *f = (FromExpr *) jtnode;
250  List *newfromlist = NIL;
251  Relids frelids = NULL;
252  FromExpr *newf;
253  Node *jtlink;
254  ListCell *l;
255 
256  /* First, recurse to process children and collect their relids */
257  foreach(l, f->fromlist)
258  {
259  Node *newchild;
260  Relids childrelids;
261 
262  newchild = pull_up_sublinks_jointree_recurse(root,
263  lfirst(l),
264  &childrelids);
265  newfromlist = lappend(newfromlist, newchild);
266  frelids = bms_join(frelids, childrelids);
267  }
268  /* Build the replacement FromExpr; no quals yet */
269  newf = makeFromExpr(newfromlist, NULL);
270  /* Set up a link representing the rebuilt jointree */
271  jtlink = (Node *) newf;
272  /* Now process qual --- all children are available for use */
273  newf->quals = pull_up_sublinks_qual_recurse(root, f->quals,
274  &jtlink, frelids,
275  NULL, NULL);
276 
277  /*
278  * Note that the result will be either newf, or a stack of JoinExprs
279  * with newf at the base. We rely on subsequent optimization steps to
280  * flatten this and rearrange the joins as needed.
281  *
282  * Although we could include the pulled-up subqueries in the returned
283  * relids, there's no need since upper quals couldn't refer to their
284  * outputs anyway.
285  */
286  *relids = frelids;
287  jtnode = jtlink;
288  }
289  else if (IsA(jtnode, JoinExpr))
290  {
291  JoinExpr *j;
292  Relids leftrelids;
293  Relids rightrelids;
294  Node *jtlink;
295 
296  /*
297  * Make a modifiable copy of join node, but don't bother copying its
298  * subnodes (yet).
299  */
300  j = (JoinExpr *) palloc(sizeof(JoinExpr));
301  memcpy(j, jtnode, sizeof(JoinExpr));
302  jtlink = (Node *) j;
303 
304  /* Recurse to process children and collect their relids */
305  j->larg = pull_up_sublinks_jointree_recurse(root, j->larg,
306  &leftrelids);
307  j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg,
308  &rightrelids);
309 
310  /*
311  * Now process qual, showing appropriate child relids as available,
312  * and attach any pulled-up jointree items at the right place. In the
313  * inner-join case we put new JoinExprs above the existing one (much
314  * as for a FromExpr-style join). In outer-join cases the new
315  * JoinExprs must go into the nullable side of the outer join. The
316  * point of the available_rels machinations is to ensure that we only
317  * pull up quals for which that's okay.
318  *
319  * We don't expect to see any pre-existing JOIN_SEMI or JOIN_ANTI
320  * nodes here.
321  */
322  switch (j->jointype)
323  {
324  case JOIN_INNER:
325  j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
326  &jtlink,
327  bms_union(leftrelids,
328  rightrelids),
329  NULL, NULL);
330  break;
331  case JOIN_LEFT:
332  j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
333  &j->rarg,
334  rightrelids,
335  NULL, NULL);
336  break;
337  case JOIN_FULL:
338  /* can't do anything with full-join quals */
339  break;
340  case JOIN_RIGHT:
341  j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
342  &j->larg,
343  leftrelids,
344  NULL, NULL);
345  break;
346  default:
347  elog(ERROR, "unrecognized join type: %d",
348  (int) j->jointype);
349  break;
350  }
351 
352  /*
353  * Although we could include the pulled-up subqueries in the returned
354  * relids, there's no need since upper quals couldn't refer to their
355  * outputs anyway. But we *do* need to include the join's own rtindex
356  * because we haven't yet collapsed join alias variables, so upper
357  * levels would mistakenly think they couldn't use references to this
358  * join.
359  */
360  *relids = bms_join(leftrelids, rightrelids);
361  if (j->rtindex)
362  *relids = bms_add_member(*relids, j->rtindex);
363  jtnode = jtlink;
364  }
365  else
366  elog(ERROR, "unrecognized node type: %d",
367  (int) nodeTag(jtnode));
368  return jtnode;
369 }
370 
371 /*
372  * Recurse through top-level qual nodes for pull_up_sublinks()
373  *
374  * jtlink1 points to the link in the jointree where any new JoinExprs should
375  * be inserted if they reference available_rels1 (i.e., available_rels1
376  * denotes the relations present underneath jtlink1). Optionally, jtlink2 can
377  * point to a second link where new JoinExprs should be inserted if they
378  * reference available_rels2 (pass NULL for both those arguments if not used).
379  * Note that SubLinks referencing both sets of variables cannot be optimized.
380  * If we find multiple pull-up-able SubLinks, they'll get stacked onto jtlink1
381  * and/or jtlink2 in the order we encounter them. We rely on subsequent
382  * optimization to rearrange the stack if appropriate.
383  *
384  * Returns the replacement qual node, or NULL if the qual should be removed.
385  */
386 static Node *
387 pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
388  Node **jtlink1, Relids available_rels1,
389  Node **jtlink2, Relids available_rels2)
390 {
391  if (node == NULL)
392  return NULL;
393  if (IsA(node, SubLink))
394  {
395  SubLink *sublink = (SubLink *) node;
396  JoinExpr *j;
397  Relids child_rels;
398 
399  /* Is it a convertible ANY or EXISTS clause? */
400  if (sublink->subLinkType == ANY_SUBLINK)
401  {
402  if ((j = convert_ANY_sublink_to_join(root, sublink,
403  available_rels1)) != NULL)
404  {
405  /* Yes; insert the new join node into the join tree */
406  j->larg = *jtlink1;
407  *jtlink1 = (Node *) j;
408  /* Recursively process pulled-up jointree nodes */
409  j->rarg = pull_up_sublinks_jointree_recurse(root,
410  j->rarg,
411  &child_rels);
412 
413  /*
414  * Now recursively process the pulled-up quals. Any inserted
415  * joins can get stacked onto either j->larg or j->rarg,
416  * depending on which rels they reference.
417  */
418  j->quals = pull_up_sublinks_qual_recurse(root,
419  j->quals,
420  &j->larg,
421  available_rels1,
422  &j->rarg,
423  child_rels);
424  /* Return NULL representing constant TRUE */
425  return NULL;
426  }
427  if (available_rels2 != NULL &&
428  (j = convert_ANY_sublink_to_join(root, sublink,
429  available_rels2)) != NULL)
430  {
431  /* Yes; insert the new join node into the join tree */
432  j->larg = *jtlink2;
433  *jtlink2 = (Node *) j;
434  /* Recursively process pulled-up jointree nodes */
435  j->rarg = pull_up_sublinks_jointree_recurse(root,
436  j->rarg,
437  &child_rels);
438 
439  /*
440  * Now recursively process the pulled-up quals. Any inserted
441  * joins can get stacked onto either j->larg or j->rarg,
442  * depending on which rels they reference.
443  */
444  j->quals = pull_up_sublinks_qual_recurse(root,
445  j->quals,
446  &j->larg,
447  available_rels2,
448  &j->rarg,
449  child_rels);
450  /* Return NULL representing constant TRUE */
451  return NULL;
452  }
453  }
454  else if (sublink->subLinkType == EXISTS_SUBLINK)
455  {
456  if ((j = convert_EXISTS_sublink_to_join(root, sublink, false,
457  available_rels1)) != NULL)
458  {
459  /* Yes; insert the new join node into the join tree */
460  j->larg = *jtlink1;
461  *jtlink1 = (Node *) j;
462  /* Recursively process pulled-up jointree nodes */
463  j->rarg = pull_up_sublinks_jointree_recurse(root,
464  j->rarg,
465  &child_rels);
466 
467  /*
468  * Now recursively process the pulled-up quals. Any inserted
469  * joins can get stacked onto either j->larg or j->rarg,
470  * depending on which rels they reference.
471  */
472  j->quals = pull_up_sublinks_qual_recurse(root,
473  j->quals,
474  &j->larg,
475  available_rels1,
476  &j->rarg,
477  child_rels);
478  /* Return NULL representing constant TRUE */
479  return NULL;
480  }
481  if (available_rels2 != NULL &&
482  (j = convert_EXISTS_sublink_to_join(root, sublink, false,
483  available_rels2)) != NULL)
484  {
485  /* Yes; insert the new join node into the join tree */
486  j->larg = *jtlink2;
487  *jtlink2 = (Node *) j;
488  /* Recursively process pulled-up jointree nodes */
489  j->rarg = pull_up_sublinks_jointree_recurse(root,
490  j->rarg,
491  &child_rels);
492 
493  /*
494  * Now recursively process the pulled-up quals. Any inserted
495  * joins can get stacked onto either j->larg or j->rarg,
496  * depending on which rels they reference.
497  */
498  j->quals = pull_up_sublinks_qual_recurse(root,
499  j->quals,
500  &j->larg,
501  available_rels2,
502  &j->rarg,
503  child_rels);
504  /* Return NULL representing constant TRUE */
505  return NULL;
506  }
507  }
508  /* Else return it unmodified */
509  return node;
510  }
511  if (is_notclause(node))
512  {
513  /* If the immediate argument of NOT is EXISTS, try to convert */
514  SubLink *sublink = (SubLink *) get_notclausearg((Expr *) node);
515  JoinExpr *j;
516  Relids child_rels;
517 
518  if (sublink && IsA(sublink, SubLink))
519  {
520  if (sublink->subLinkType == EXISTS_SUBLINK)
521  {
522  if ((j = convert_EXISTS_sublink_to_join(root, sublink, true,
523  available_rels1)) != NULL)
524  {
525  /* Yes; insert the new join node into the join tree */
526  j->larg = *jtlink1;
527  *jtlink1 = (Node *) j;
528  /* Recursively process pulled-up jointree nodes */
529  j->rarg = pull_up_sublinks_jointree_recurse(root,
530  j->rarg,
531  &child_rels);
532 
533  /*
534  * Now recursively process the pulled-up quals. Because
535  * we are underneath a NOT, we can't pull up sublinks that
536  * reference the left-hand stuff, but it's still okay to
537  * pull up sublinks referencing j->rarg.
538  */
539  j->quals = pull_up_sublinks_qual_recurse(root,
540  j->quals,
541  &j->rarg,
542  child_rels,
543  NULL, NULL);
544  /* Return NULL representing constant TRUE */
545  return NULL;
546  }
547  if (available_rels2 != NULL &&
548  (j = convert_EXISTS_sublink_to_join(root, sublink, true,
549  available_rels2)) != NULL)
550  {
551  /* Yes; insert the new join node into the join tree */
552  j->larg = *jtlink2;
553  *jtlink2 = (Node *) j;
554  /* Recursively process pulled-up jointree nodes */
555  j->rarg = pull_up_sublinks_jointree_recurse(root,
556  j->rarg,
557  &child_rels);
558 
559  /*
560  * Now recursively process the pulled-up quals. Because
561  * we are underneath a NOT, we can't pull up sublinks that
562  * reference the left-hand stuff, but it's still okay to
563  * pull up sublinks referencing j->rarg.
564  */
565  j->quals = pull_up_sublinks_qual_recurse(root,
566  j->quals,
567  &j->rarg,
568  child_rels,
569  NULL, NULL);
570  /* Return NULL representing constant TRUE */
571  return NULL;
572  }
573  }
574  }
575  /* Else return it unmodified */
576  return node;
577  }
578  if (is_andclause(node))
579  {
580  /* Recurse into AND clause */
581  List *newclauses = NIL;
582  ListCell *l;
583 
584  foreach(l, ((BoolExpr *) node)->args)
585  {
586  Node *oldclause = (Node *) lfirst(l);
587  Node *newclause;
588 
589  newclause = pull_up_sublinks_qual_recurse(root,
590  oldclause,
591  jtlink1,
592  available_rels1,
593  jtlink2,
594  available_rels2);
595  if (newclause)
596  newclauses = lappend(newclauses, newclause);
597  }
598  /* We might have got back fewer clauses than we started with */
599  if (newclauses == NIL)
600  return NULL;
601  else if (list_length(newclauses) == 1)
602  return (Node *) linitial(newclauses);
603  else
604  return (Node *) make_andclause(newclauses);
605  }
606  /* Stop if not an AND */
607  return node;
608 }
609 
610 /*
611  * preprocess_function_rtes
612  * Constant-simplify any FUNCTION RTEs in the FROM clause, and then
613  * attempt to "inline" any that are set-returning functions.
614  *
615  * If an RTE_FUNCTION rtable entry invokes a set-returning function that
616  * contains just a simple SELECT, we can convert the rtable entry to an
617  * RTE_SUBQUERY entry exposing the SELECT directly. This is especially
618  * useful if the subquery can then be "pulled up" for further optimization,
619  * but we do it even if not, to reduce executor overhead.
620  *
621  * This has to be done before we have started to do any optimization of
622  * subqueries, else any such steps wouldn't get applied to subqueries
623  * obtained via inlining. However, we do it after pull_up_sublinks
624  * so that we can inline any functions used in SubLink subselects.
625  *
626  * The reason for applying const-simplification at this stage is that
627  * (a) we'd need to do it anyway to inline a SRF, and (b) by doing it now,
628  * we can be sure that pull_up_constant_function() will see constants
629  * if there are constants to be seen. This approach also guarantees
630  * that every FUNCTION RTE has been const-simplified, allowing planner.c's
631  * preprocess_expression() to skip doing it again.
632  *
633  * Like most of the planner, this feels free to scribble on its input data
634  * structure.
635  */
636 void
637 preprocess_function_rtes(PlannerInfo *root)
638 {
639  ListCell *rt;
640 
641  foreach(rt, root->parse->rtable)
642  {
643  RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt);
644 
645  if (rte->rtekind == RTE_FUNCTION)
646  {
647  Query *funcquery;
648 
649  /* Apply const-simplification */
650  rte->functions = (List *)
651  eval_const_expressions(root, (Node *) rte->functions);
652 
653  /* Check safety of expansion, and expand if possible */
654  funcquery = inline_set_returning_function(root, rte);
655  if (funcquery)
656  {
657  /* Successful expansion, convert the RTE to a subquery */
658  rte->rtekind = RTE_SUBQUERY;
659  rte->subquery = funcquery;
660  rte->security_barrier = false;
661  /* Clear fields that should not be set in a subquery RTE */
662  rte->functions = NIL;
663  rte->funcordinality = false;
664  }
665  }
666  }
667 }
668 
669 /*
670  * pull_up_subqueries
671  * Look for subqueries in the rangetable that can be pulled up into
672  * the parent query. If the subquery has no special features like
673  * grouping/aggregation then we can merge it into the parent's jointree.
674  * Also, subqueries that are simple UNION ALL structures can be
675  * converted into "append relations".
676  */
677 void
678 pull_up_subqueries(PlannerInfo *root)
679 {
680  /* Top level of jointree must always be a FromExpr */
681  Assert(IsA(root->parse->jointree, FromExpr));
682  /* Recursion starts with no containing join nor appendrel */
683  root->parse->jointree = (FromExpr *)
684  pull_up_subqueries_recurse(root, (Node *) root->parse->jointree,
685  NULL, NULL, NULL);
686  /* We should still have a FromExpr */
687  Assert(IsA(root->parse->jointree, FromExpr));
688 }
689 
690 /*
691  * pull_up_subqueries_recurse
692  * Recursive guts of pull_up_subqueries.
693  *
694  * This recursively processes the jointree and returns a modified jointree.
695  *
696  * If this jointree node is within either side of an outer join, then
697  * lowest_outer_join references the lowest such JoinExpr node; otherwise
698  * it is NULL. We use this to constrain the effects of LATERAL subqueries.
699  *
700  * If this jointree node is within the nullable side of an outer join, then
701  * lowest_nulling_outer_join references the lowest such JoinExpr node;
702  * otherwise it is NULL. This forces use of the PlaceHolderVar mechanism for
703  * references to non-nullable targetlist items, but only for references above
704  * that join.
705  *
706  * If we are looking at a member subquery of an append relation,
707  * containing_appendrel describes that relation; else it is NULL.
708  * This forces use of the PlaceHolderVar mechanism for all non-Var targetlist
709  * items, and puts some additional restrictions on what can be pulled up.
710  *
711  * A tricky aspect of this code is that if we pull up a subquery we have
712  * to replace Vars that reference the subquery's outputs throughout the
713  * parent query, including quals attached to jointree nodes above the one
714  * we are currently processing! We handle this by being careful to maintain
715  * validity of the jointree structure while recursing, in the following sense:
716  * whenever we recurse, all qual expressions in the tree must be reachable
717  * from the top level, in case the recursive call needs to modify them.
718  *
719  * Notice also that we can't turn pullup_replace_vars loose on the whole
720  * jointree, because it'd return a mutated copy of the tree; we have to
721  * invoke it just on the quals, instead. This behavior is what makes it
722  * reasonable to pass lowest_outer_join and lowest_nulling_outer_join as
723  * pointers rather than some more-indirect way of identifying the lowest
724  * OJs. Likewise, we don't replace append_rel_list members but only their
725  * substructure, so the containing_appendrel reference is safe to use.
726  */
727 static Node *
728 pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
729  JoinExpr *lowest_outer_join,
730  JoinExpr *lowest_nulling_outer_join,
731  AppendRelInfo *containing_appendrel)
732 {
733  Assert(jtnode != NULL);
734  if (IsA(jtnode, RangeTblRef))
735  {
736  int varno = ((RangeTblRef *) jtnode)->rtindex;
737  RangeTblEntry *rte = rt_fetch(varno, root->parse->rtable);
738 
739  /*
740  * Is this a subquery RTE, and if so, is the subquery simple enough to
741  * pull up?
742  *
743  * If we are looking at an append-relation member, we can't pull it up
744  * unless is_safe_append_member says so.
745  */
746  if (rte->rtekind == RTE_SUBQUERY &&
747  is_simple_subquery(rte->subquery, rte, lowest_outer_join) &&
748  (containing_appendrel == NULL ||
749  is_safe_append_member(rte->subquery)))
750  return pull_up_simple_subquery(root, jtnode, rte,
751  lowest_outer_join,
752  lowest_nulling_outer_join,
753  containing_appendrel);
754 
755  /*
756  * Alternatively, is it a simple UNION ALL subquery? If so, flatten
757  * into an "append relation".
758  *
759  * It's safe to do this regardless of whether this query is itself an
760  * appendrel member. (If you're thinking we should try to flatten the
761  * two levels of appendrel together, you're right; but we handle that
762  * in set_append_rel_pathlist, not here.)
763  */
764  if (rte->rtekind == RTE_SUBQUERY &&
765  is_simple_union_all(rte->subquery))
766  return pull_up_simple_union_all(root, jtnode, rte);
767 
768  /*
769  * Or perhaps it's a simple VALUES RTE?
770  *
771  * We don't allow VALUES pullup below an outer join nor into an
772  * appendrel (such cases are impossible anyway at the moment).
773  */
774  if (rte->rtekind == RTE_VALUES &&
775  lowest_outer_join == NULL &&
776  containing_appendrel == NULL &&
777  is_simple_values(root, rte))
778  return pull_up_simple_values(root, jtnode, rte);
779 
780  /*
781  * Or perhaps it's a FUNCTION RTE that we could inline?
782  */
783  if (rte->rtekind == RTE_FUNCTION)
784  return pull_up_constant_function(root, jtnode, rte,
785  lowest_nulling_outer_join,
786  containing_appendrel);
787 
788  /* Otherwise, do nothing at this node. */
789  }
790  else if (IsA(jtnode, FromExpr))
791  {
792  FromExpr *f = (FromExpr *) jtnode;
793  ListCell *l;
794 
795  Assert(containing_appendrel == NULL);
796  /* Recursively transform all the child nodes */
797  foreach(l, f->fromlist)
798  {
799  lfirst(l) = pull_up_subqueries_recurse(root, lfirst(l),
800  lowest_outer_join,
801  lowest_nulling_outer_join,
802  NULL);
803  }
804  }
805  else if (IsA(jtnode, JoinExpr))
806  {
807  JoinExpr *j = (JoinExpr *) jtnode;
808 
809  Assert(containing_appendrel == NULL);
810  /* Recurse, being careful to tell myself when inside outer join */
811  switch (j->jointype)
812  {
813  case JOIN_INNER:
814  j->larg = pull_up_subqueries_recurse(root, j->larg,
815  lowest_outer_join,
816  lowest_nulling_outer_join,
817  NULL);
818  j->rarg = pull_up_subqueries_recurse(root, j->rarg,
819  lowest_outer_join,
820  lowest_nulling_outer_join,
821  NULL);
822  break;
823  case JOIN_LEFT:
824  case JOIN_SEMI:
825  case JOIN_ANTI:
826  j->larg = pull_up_subqueries_recurse(root, j->larg,
827  j,
828  lowest_nulling_outer_join,
829  NULL);
830  j->rarg = pull_up_subqueries_recurse(root, j->rarg,
831  j,
832  j,
833  NULL);
834  break;
835  case JOIN_FULL:
836  j->larg = pull_up_subqueries_recurse(root, j->larg,
837  j,
838  j,
839  NULL);
840  j->rarg = pull_up_subqueries_recurse(root, j->rarg,
841  j,
842  j,
843  NULL);
844  break;
845  case JOIN_RIGHT:
846  j->larg = pull_up_subqueries_recurse(root, j->larg,
847  j,
848  j,
849  NULL);
850  j->rarg = pull_up_subqueries_recurse(root, j->rarg,
851  j,
852  lowest_nulling_outer_join,
853  NULL);
854  break;
855  default:
856  elog(ERROR, "unrecognized join type: %d",
857  (int) j->jointype);
858  break;
859  }
860  }
861  else
862  elog(ERROR, "unrecognized node type: %d",
863  (int) nodeTag(jtnode));
864  return jtnode;
865 }
866 
867 /*
868  * pull_up_simple_subquery
869  * Attempt to pull up a single simple subquery.
870  *
871  * jtnode is a RangeTblRef that has been tentatively identified as a simple
872  * subquery by pull_up_subqueries. We return the replacement jointree node,
873  * or jtnode itself if we determine that the subquery can't be pulled up
874  * after all.
875  *
876  * rte is the RangeTblEntry referenced by jtnode. Remaining parameters are
877  * as for pull_up_subqueries_recurse.
878  */
879 static Node *
880 pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
881  JoinExpr *lowest_outer_join,
882  JoinExpr *lowest_nulling_outer_join,
883  AppendRelInfo *containing_appendrel)
884 {
885  Query *parse = root->parse;
886  int varno = ((RangeTblRef *) jtnode)->rtindex;
887  Query *subquery;
888  PlannerInfo *subroot;
889  int rtoffset;
890  pullup_replace_vars_context rvcontext;
891  ListCell *lc;
892 
893  /*
894  * Need a modifiable copy of the subquery to hack on. Even if we didn't
895  * sometimes choose not to pull up below, we must do this to avoid
896  * problems if the same subquery is referenced from multiple jointree
897  * items (which can't happen normally, but might after rule rewriting).
898  */
899  subquery = copyObject(rte->subquery);
900 
901  /*
902  * Create a PlannerInfo data structure for this subquery.
903  *
904  * NOTE: the next few steps should match the first processing in
905  * subquery_planner(). Can we refactor to avoid code duplication, or
906  * would that just make things uglier?
907  */
908  subroot = makeNode(PlannerInfo);
909  subroot->parse = subquery;
910  subroot->glob = root->glob;
911  subroot->query_level = root->query_level;
912  subroot->parent_root = root->parent_root;
913  subroot->plan_params = NIL;
914  subroot->outer_params = NULL;
915  subroot->planner_cxt = CurrentMemoryContext;
916  subroot->init_plans = NIL;
917  subroot->cte_plan_ids = NIL;
918  subroot->multiexpr_params = NIL;
919  subroot->eq_classes = NIL;
920  subroot->ec_merging_done = false;
921  subroot->append_rel_list = NIL;
922  subroot->rowMarks = NIL;
923  memset(subroot->upper_rels, 0, sizeof(subroot->upper_rels));
924  memset(subroot->upper_targets, 0, sizeof(subroot->upper_targets));
925  subroot->processed_tlist = NIL;
926  subroot->grouping_map = NULL;
927  subroot->minmax_aggs = NIL;
928  subroot->qual_security_level = 0;
929  subroot->inhTargetKind = INHKIND_NONE;
930  subroot->hasRecursion = false;
931  subroot->wt_param_id = -1;
932  subroot->non_recursive_path = NULL;
933 
934  /* No CTEs to worry about */
935  Assert(subquery->cteList == NIL);
936 
937  /*
938  * If the FROM clause is empty, replace it with a dummy RTE_RESULT RTE, so
939  * that we don't need so many special cases to deal with that situation.
940  */
941  replace_empty_jointree(subquery);
942 
943  /*
944  * Pull up any SubLinks within the subquery's quals, so that we don't
945  * leave unoptimized SubLinks behind.
946  */
947  if (subquery->hasSubLinks)
948  pull_up_sublinks(subroot);
949 
950  /*
951  * Similarly, preprocess its function RTEs to inline any set-returning
952  * functions in its rangetable.
953  */
954  preprocess_function_rtes(subroot);
955 
956  /*
957  * Recursively pull up the subquery's subqueries, so that
958  * pull_up_subqueries' processing is complete for its jointree and
959  * rangetable.
960  *
961  * Note: it's okay that the subquery's recursion starts with NULL for
962  * containing-join info, even if we are within an outer join in the upper
963  * query; the lower query starts with a clean slate for outer-join
964  * semantics. Likewise, we needn't pass down appendrel state.
965  */
966  pull_up_subqueries(subroot);
967 
968  /*
969  * Now we must recheck whether the subquery is still simple enough to pull
970  * up. If not, abandon processing it.
971  *
972  * We don't really need to recheck all the conditions involved, but it's
973  * easier just to keep this "if" looking the same as the one in
974  * pull_up_subqueries_recurse.
975  */
976  if (is_simple_subquery(subquery, rte, lowest_outer_join) &&
977  (containing_appendrel == NULL || is_safe_append_member(subquery)))
978  {
979  /* good to go */
980  }
981  else
982  {
983  /*
984  * Give up, return unmodified RangeTblRef.
985  *
986  * Note: The work we just did will be redone when the subquery gets
987  * planned on its own. Perhaps we could avoid that by storing the
988  * modified subquery back into the rangetable, but I'm not gonna risk
989  * it now.
990  */
991  return jtnode;
992  }
993 
994  /*
995  * We must flatten any join alias Vars in the subquery's targetlist,
996  * because pulling up the subquery's subqueries might have changed their
997  * expansions into arbitrary expressions, which could affect
998  * pullup_replace_vars' decisions about whether PlaceHolderVar wrappers
999  * are needed for tlist entries. (Likely it'd be better to do
1000  * flatten_join_alias_vars on the whole query tree at some earlier stage,
1001  * maybe even in the rewriter; but for now let's just fix this case here.)
1002  */
1003  subquery->targetList = (List *)
1004  flatten_join_alias_vars(subroot->parse, (Node *) subquery->targetList);
1005 
1006  /*
1007  * Adjust level-0 varnos in subquery so that we can append its rangetable
1008  * to upper query's. We have to fix the subquery's append_rel_list as
1009  * well.
1010  */
1011  rtoffset = list_length(parse->rtable);
1012  OffsetVarNodes((Node *) subquery, rtoffset, 0);
1013  OffsetVarNodes((Node *) subroot->append_rel_list, rtoffset, 0);
1014 
1015  /*
1016  * Upper-level vars in subquery are now one level closer to their parent
1017  * than before.
1018  */
1019  IncrementVarSublevelsUp((Node *) subquery, -1, 1);
1020  IncrementVarSublevelsUp((Node *) subroot->append_rel_list, -1, 1);
1021 
1022  /*
1023  * The subquery's targetlist items are now in the appropriate form to
1024  * insert into the top query, except that we may need to wrap them in
1025  * PlaceHolderVars. Set up required context data for pullup_replace_vars.
1026  */
1027  rvcontext.root = root;
1028  rvcontext.targetlist = subquery->targetList;
1029  rvcontext.target_rte = rte;
1030  if (rte->lateral)
1031  rvcontext.relids = get_relids_in_jointree((Node *) subquery->jointree,
1032  true);
1033  else /* won't need relids */
1034  rvcontext.relids = NULL;
1035  rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
1036  rvcontext.varno = varno;
1037  /* these flags will be set below, if needed */
1038  rvcontext.need_phvs = false;
1039  rvcontext.wrap_non_vars = false;
1040  /* initialize cache array with indexes 0 .. length(tlist) */
1041  rvcontext.rv_cache = palloc0((list_length(subquery->targetList) + 1) *
1042  sizeof(Node *));
1043 
1044  /*
1045  * If we are under an outer join then non-nullable items and lateral
1046  * references may have to be turned into PlaceHolderVars.
1047  */
1048  if (lowest_nulling_outer_join != NULL)
1049  rvcontext.need_phvs = true;
1050 
1051  /*
1052  * If we are dealing with an appendrel member then anything that's not a
1053  * simple Var has to be turned into a PlaceHolderVar. We force this to
1054  * ensure that what we pull up doesn't get merged into a surrounding
1055  * expression during later processing and then fail to match the
1056  * expression actually available from the appendrel.
1057  */
1058  if (containing_appendrel != NULL)
1059  {
1060  rvcontext.need_phvs = true;
1061  rvcontext.wrap_non_vars = true;
1062  }
1063 
1064  /*
1065  * If the parent query uses grouping sets, we need a PlaceHolderVar for
1066  * anything that's not a simple Var. Again, this ensures that expressions
1067  * retain their separate identity so that they will match grouping set
1068  * columns when appropriate. (It'd be sufficient to wrap values used in
1069  * grouping set columns, and do so only in non-aggregated portions of the
1070  * tlist and havingQual, but that would require a lot of infrastructure
1071  * that pullup_replace_vars hasn't currently got.)
1072  */
1073  if (parse->groupingSets)
1074  {
1075  rvcontext.need_phvs = true;
1076  rvcontext.wrap_non_vars = true;
1077  }
1078 
1079  /*
1080  * Replace all of the top query's references to the subquery's outputs
1081  * with copies of the adjusted subtlist items, being careful not to
1082  * replace any of the jointree structure.
1083  */
1084  perform_pullup_replace_vars(root, &rvcontext,
1085  lowest_nulling_outer_join,
1086  containing_appendrel);
1087 
1088  /*
1089  * If the subquery had a LATERAL marker, propagate that to any of its
1090  * child RTEs that could possibly now contain lateral cross-references.
1091  * The children might or might not contain any actual lateral
1092  * cross-references, but we have to mark the pulled-up child RTEs so that
1093  * later planner stages will check for such.
1094  */
1095  if (rte->lateral)
1096  {
1097  foreach(lc, subquery->rtable)
1098  {
1099  RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(lc);
1100 
1101  switch (child_rte->rtekind)
1102  {
1103  case RTE_RELATION:
1104  if (child_rte->tablesample)
1105  child_rte->lateral = true;
1106  break;
1107  case RTE_SUBQUERY:
1108  case RTE_FUNCTION:
1109  case RTE_VALUES:
1110  case RTE_TABLEFUNC:
1111  child_rte->lateral = true;
1112  break;
1113  case RTE_JOIN:
1114  case RTE_CTE:
1115  case RTE_NAMEDTUPLESTORE:
1116  case RTE_RESULT:
1117  /* these can't contain any lateral references */
1118  break;
1119  }
1120  }
1121  }
1122 
1123  /*
1124  * Now append the adjusted rtable entries to upper query. (We hold off
1125  * until after fixing the upper rtable entries; no point in running that
1126  * code on the subquery ones too.)
1127  */
1128  parse->rtable = list_concat(parse->rtable, subquery->rtable);
1129 
1130  /*
1131  * Pull up any FOR UPDATE/SHARE markers, too. (OffsetVarNodes already
1132  * adjusted the marker rtindexes, so just concat the lists.)
1133  */
1134  parse->rowMarks = list_concat(parse->rowMarks, subquery->rowMarks);
1135 
1136  /*
1137  * We also have to fix the relid sets of any PlaceHolderVar nodes in the
1138  * parent query. (This could perhaps be done by pullup_replace_vars(),
1139  * but it seems cleaner to use two passes.) Note in particular that any
1140  * PlaceHolderVar nodes just created by pullup_replace_vars() will be
1141  * adjusted, so having created them with the subquery's varno is correct.
1142  *
1143  * Likewise, relids appearing in AppendRelInfo nodes have to be fixed. We
1144  * already checked that this won't require introducing multiple subrelids
1145  * into the single-slot AppendRelInfo structs.
1146  */
1147  if (parse->hasSubLinks || root->glob->lastPHId != 0 ||
1148  root->append_rel_list)
1149  {
1150  Relids subrelids;
1151 
1152  subrelids = get_relids_in_jointree((Node *) subquery->jointree, false);
1153  substitute_phv_relids((Node *) parse, varno, subrelids);
1154  fix_append_rel_relids(root->append_rel_list, varno, subrelids);
1155  }
1156 
1157  /*
1158  * And now add subquery's AppendRelInfos to our list.
1159  */
1160  root->append_rel_list = list_concat(root->append_rel_list,
1161  subroot->append_rel_list);
1162 
1163  /*
1164  * We don't have to do the equivalent bookkeeping for outer-join info,
1165  * because that hasn't been set up yet. placeholder_list likewise.
1166  */
1167  Assert(root->join_info_list == NIL);
1168  Assert(subroot->join_info_list == NIL);
1169  Assert(root->placeholder_list == NIL);
1170  Assert(subroot->placeholder_list == NIL);
1171 
1172  /*
1173  * Miscellaneous housekeeping.
1174  *
1175  * Although replace_rte_variables() faithfully updated parse->hasSubLinks
1176  * if it copied any SubLinks out of the subquery's targetlist, we still
1177  * could have SubLinks added to the query in the expressions of FUNCTION
1178  * and VALUES RTEs copied up from the subquery. So it's necessary to copy
1179  * subquery->hasSubLinks anyway. Perhaps this can be improved someday.
1180  */
1181  parse->hasSubLinks |= subquery->hasSubLinks;
1182 
1183  /* If subquery had any RLS conditions, now main query does too */
1184  parse->hasRowSecurity |= subquery->hasRowSecurity;
1185 
1186  /*
1187  * subquery won't be pulled up if it hasAggs, hasWindowFuncs, or
1188  * hasTargetSRFs, so no work needed on those flags
1189  */
1190 
1191  /*
1192  * Return the adjusted subquery jointree to replace the RangeTblRef entry
1193  * in parent's jointree; or, if the FromExpr is degenerate, just return
1194  * its single member.
1195  */
1196  Assert(IsA(subquery->jointree, FromExpr));
1197  Assert(subquery->jointree->fromlist != NIL);
1198  if (subquery->jointree->quals == NULL &&
1199  list_length(subquery->jointree->fromlist) == 1)
1200  return (Node *) linitial(subquery->jointree->fromlist);
1201 
1202  return (Node *) subquery->jointree;
1203 }
1204 
1205 /*
1206  * pull_up_simple_union_all
1207  * Pull up a single simple UNION ALL subquery.
1208  *
1209  * jtnode is a RangeTblRef that has been identified as a simple UNION ALL
1210  * subquery by pull_up_subqueries. We pull up the leaf subqueries and
1211  * build an "append relation" for the union set. The result value is just
1212  * jtnode, since we don't actually need to change the query jointree.
1213  */
1214 static Node *
1215 pull_up_simple_union_all(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
1216 {
1217  int varno = ((RangeTblRef *) jtnode)->rtindex;
1218  Query *subquery = rte->subquery;
1219  int rtoffset = list_length(root->parse->rtable);
1220  List *rtable;
1221 
1222  /*
1223  * Make a modifiable copy of the subquery's rtable, so we can adjust
1224  * upper-level Vars in it. There are no such Vars in the setOperations
1225  * tree proper, so fixing the rtable should be sufficient.
1226  */
1227  rtable = copyObject(subquery->rtable);
1228 
1229  /*
1230  * Upper-level vars in subquery are now one level closer to their parent
1231  * than before. We don't have to worry about offsetting varnos, though,
1232  * because the UNION leaf queries can't cross-reference each other.
1233  */
1234  IncrementVarSublevelsUp_rtable(rtable, -1, 1);
1235 
1236  /*
1237  * If the UNION ALL subquery had a LATERAL marker, propagate that to all
1238  * its children. The individual children might or might not contain any
1239  * actual lateral cross-references, but we have to mark the pulled-up
1240  * child RTEs so that later planner stages will check for such.
1241  */
1242  if (rte->lateral)
1243  {
1244  ListCell *rt;
1245 
1246  foreach(rt, rtable)
1247  {
1248  RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(rt);
1249 
1250  Assert(child_rte->rtekind == RTE_SUBQUERY);
1251  child_rte->lateral = true;
1252  }
1253  }
1254 
1255  /*
1256  * Append child RTEs to parent rtable.
1257  */
1258  root->parse->rtable = list_concat(root->parse->rtable, rtable);
1259 
1260  /*
1261  * Recursively scan the subquery's setOperations tree and add
1262  * AppendRelInfo nodes for leaf subqueries to the parent's
1263  * append_rel_list. Also apply pull_up_subqueries to the leaf subqueries.
1264  */
1265  Assert(subquery->setOperations);
1266  pull_up_union_leaf_queries(subquery->setOperations, root, varno, subquery,
1267  rtoffset);
1268 
1269  /*
1270  * Mark the parent as an append relation.
1271  */
1272  rte->inh = true;
1273 
1274  return jtnode;
1275 }
1276 
1277 /*
1278  * pull_up_union_leaf_queries -- recursive guts of pull_up_simple_union_all
1279  *
1280  * Build an AppendRelInfo for each leaf query in the setop tree, and then
1281  * apply pull_up_subqueries to the leaf query.
1282  *
1283  * Note that setOpQuery is the Query containing the setOp node, whose tlist
1284  * contains references to all the setop output columns. When called from
1285  * pull_up_simple_union_all, this is *not* the same as root->parse, which is
1286  * the parent Query we are pulling up into.
1287  *
1288  * parentRTindex is the appendrel parent's index in root->parse->rtable.
1289  *
1290  * The child RTEs have already been copied to the parent. childRToffset
1291  * tells us where in the parent's range table they were copied. When called
1292  * from flatten_simple_union_all, childRToffset is 0 since the child RTEs
1293  * were already in root->parse->rtable and no RT index adjustment is needed.
1294  */
1295 static void
1296 pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
1297  Query *setOpQuery, int childRToffset)
1298 {
1299  if (IsA(setOp, RangeTblRef))
1300  {
1301  RangeTblRef *rtr = (RangeTblRef *) setOp;
1302  int childRTindex;
1303  AppendRelInfo *appinfo;
1304 
1305  /*
1306  * Calculate the index in the parent's range table
1307  */
1308  childRTindex = childRToffset + rtr->rtindex;
1309 
1310  /*
1311  * Build a suitable AppendRelInfo, and attach to parent's list.
1312  */
1313  appinfo = makeNode(AppendRelInfo);
1314  appinfo->parent_relid = parentRTindex;
1315  appinfo->child_relid = childRTindex;
1316  appinfo->parent_reltype = InvalidOid;
1317  appinfo->child_reltype = InvalidOid;
1318  make_setop_translation_list(setOpQuery, childRTindex, appinfo);
1319  appinfo->parent_reloid = InvalidOid;
1320  root->append_rel_list = lappend(root->append_rel_list, appinfo);
1321 
1322  /*
1323  * Recursively apply pull_up_subqueries to the new child RTE. (We
1324  * must build the AppendRelInfo first, because this will modify it.)
1325  * Note that we can pass NULL for containing-join info even if we're
1326  * actually under an outer join, because the child's expressions
1327  * aren't going to propagate up to the join. Also, we ignore the
1328  * possibility that pull_up_subqueries_recurse() returns a different
1329  * jointree node than what we pass it; if it does, the important thing
1330  * is that it replaced the child relid in the AppendRelInfo node.
1331  */
1332  rtr = makeNode(RangeTblRef);
1333  rtr->rtindex = childRTindex;
1334  (void) pull_up_subqueries_recurse(root, (Node *) rtr,
1335  NULL, NULL, appinfo);
1336  }
1337  else if (IsA(setOp, SetOperationStmt))
1338  {
1339  SetOperationStmt *op = (SetOperationStmt *) setOp;
1340 
1341  /* Recurse to reach leaf queries */
1342  pull_up_union_leaf_queries(op->larg, root, parentRTindex, setOpQuery,
1343  childRToffset);
1344  pull_up_union_leaf_queries(op->rarg, root, parentRTindex, setOpQuery,
1345  childRToffset);
1346  }
1347  else
1348  {
1349  elog(ERROR, "unrecognized node type: %d",
1350  (int) nodeTag(setOp));
1351  }
1352 }
1353 
1354 /*
1355  * make_setop_translation_list
1356  * Build the list of translations from parent Vars to child Vars for
1357  * a UNION ALL member. (At this point it's just a simple list of
1358  * referencing Vars, but if we succeed in pulling up the member
1359  * subquery, the Vars will get replaced by pulled-up expressions.)
1360  * Also create the rather trivial reverse-translation array.
1361  */
1362 static void
1363 make_setop_translation_list(Query *query, Index newvarno,
1364  AppendRelInfo *appinfo)
1365 {
1366  List *vars = NIL;
1367  AttrNumber *pcolnos;
1368  ListCell *l;
1369 
1370  /* Initialize reverse-translation array with all entries zero */
1371  /* (entries for resjunk columns will stay that way) */
1372  appinfo->num_child_cols = list_length(query->targetList);
1373  appinfo->parent_colnos = pcolnos =
1374  (AttrNumber *) palloc0(appinfo->num_child_cols * sizeof(AttrNumber));
1375 
1376  foreach(l, query->targetList)
1377  {
1378  TargetEntry *tle = (TargetEntry *) lfirst(l);
1379 
1380  if (tle->resjunk)
1381  continue;
1382 
1383  vars = lappend(vars, makeVarFromTargetEntry(newvarno, tle));
1384  pcolnos[tle->resno - 1] = tle->resno;
1385  }
1386 
1387  appinfo->translated_vars = vars;
1388 }
1389 
1390 /*
1391  * is_simple_subquery
1392  * Check a subquery in the range table to see if it's simple enough
1393  * to pull up into the parent query.
1394  *
1395  * rte is the RTE_SUBQUERY RangeTblEntry that contained the subquery.
1396  * (Note subquery is not necessarily equal to rte->subquery; it could be a
1397  * processed copy of that.)
1398  * lowest_outer_join is the lowest outer join above the subquery, or NULL.
1399  */
1400 static bool
1401 is_simple_subquery(Query *subquery, RangeTblEntry *rte,
1402  JoinExpr *lowest_outer_join)
1403 {
1404  /*
1405  * Let's just make sure it's a valid subselect ...
1406  */
1407  if (!IsA(subquery, Query) ||
1408  subquery->commandType != CMD_SELECT)
1409  elog(ERROR, "subquery is bogus");
1410 
1411  /*
1412  * Can't currently pull up a query with setops (unless it's simple UNION
1413  * ALL, which is handled by a different code path). Maybe after querytree
1414  * redesign...
1415  */
1416  if (subquery->setOperations)
1417  return false;
1418 
1419  /*
1420  * Can't pull up a subquery involving grouping, aggregation, SRFs,
1421  * sorting, limiting, or WITH. (XXX WITH could possibly be allowed later)
1422  *
1423  * We also don't pull up a subquery that has explicit FOR UPDATE/SHARE
1424  * clauses, because pullup would cause the locking to occur semantically
1425  * higher than it should. Implicit FOR UPDATE/SHARE is okay because in
1426  * that case the locking was originally declared in the upper query
1427  * anyway.
1428  */
1429  if (subquery->hasAggs ||
1430  subquery->hasWindowFuncs ||
1431  subquery->hasTargetSRFs ||
1432  subquery->groupClause ||
1433  subquery->groupingSets ||
1434  subquery->havingQual ||
1435  subquery->sortClause ||
1436  subquery->distinctClause ||
1437  subquery->limitOffset ||
1438  subquery->limitCount ||
1439  subquery->hasForUpdate ||
1440  subquery->cteList)
1441  return false;
1442 
1443  /*
1444  * Don't pull up if the RTE represents a security-barrier view; we
1445  * couldn't prevent information leakage once the RTE's Vars are scattered
1446  * about in the upper query.
1447  */
1448  if (rte->security_barrier)
1449  return false;
1450 
1451  /*
1452  * If the subquery is LATERAL, check for pullup restrictions from that.
1453  */
1454  if (rte->lateral)
1455  {
1456  bool restricted;
1457  Relids safe_upper_varnos;
1458 
1459  /*
1460  * The subquery's WHERE and JOIN/ON quals mustn't contain any lateral
1461  * references to rels outside a higher outer join (including the case
1462  * where the outer join is within the subquery itself). In such a
1463  * case, pulling up would result in a situation where we need to
1464  * postpone quals from below an outer join to above it, which is
1465  * probably completely wrong and in any case is a complication that
1466  * doesn't seem worth addressing at the moment.
1467  */
1468  if (lowest_outer_join != NULL)
1469  {
1470  restricted = true;
1471  safe_upper_varnos = get_relids_in_jointree((Node *) lowest_outer_join,
1472  true);
1473  }
1474  else
1475  {
1476  restricted = false;
1477  safe_upper_varnos = NULL; /* doesn't matter */
1478  }
1479 
1480  if (jointree_contains_lateral_outer_refs((Node *) subquery->jointree,
1481  restricted, safe_upper_varnos))
1482  return false;
1483 
1484  /*
1485  * If there's an outer join above the LATERAL subquery, also disallow
1486  * pullup if the subquery's targetlist has any references to rels
1487  * outside the outer join, since these might get pulled into quals
1488  * above the subquery (but in or below the outer join) and then lead
1489  * to qual-postponement issues similar to the case checked for above.
1490  * (We wouldn't need to prevent pullup if no such references appear in
1491  * outer-query quals, but we don't have enough info here to check
1492  * that. Also, maybe this restriction could be removed if we forced
1493  * such refs to be wrapped in PlaceHolderVars, even when they're below
1494  * the nearest outer join? But it's a pretty hokey usage, so not
1495  * clear this is worth sweating over.)
1496  */
1497  if (lowest_outer_join != NULL)
1498  {
1499  Relids lvarnos = pull_varnos_of_level((Node *) subquery->targetList, 1);
1500 
1501  if (!bms_is_subset(lvarnos, safe_upper_varnos))
1502  return false;
1503  }
1504  }
1505 
1506  /*
1507  * Don't pull up a subquery that has any volatile functions in its
1508  * targetlist. Otherwise we might introduce multiple evaluations of these
1509  * functions, if they get copied to multiple places in the upper query,
1510  * leading to surprising results. (Note: the PlaceHolderVar mechanism
1511  * doesn't quite guarantee single evaluation; else we could pull up anyway
1512  * and just wrap such items in PlaceHolderVars ...)
1513  */
1514  if (contain_volatile_functions((Node *) subquery->targetList))
1515  return false;
1516 
1517  return true;
1518 }
1519 
1520 /*
1521  * pull_up_simple_values
1522  * Pull up a single simple VALUES RTE.
1523  *
1524  * jtnode is a RangeTblRef that has been identified as a simple VALUES RTE
1525  * by pull_up_subqueries. We always return a RangeTblRef representing a
1526  * RESULT RTE to replace it (all failure cases should have been detected by
1527  * is_simple_values()). Actually, what we return is just jtnode, because
1528  * we replace the VALUES RTE in the rangetable with the RESULT RTE.
1529  *
1530  * rte is the RangeTblEntry referenced by jtnode. Because of the limited
1531  * possible usage of VALUES RTEs, we do not need the remaining parameters
1532  * of pull_up_subqueries_recurse.
1533  */
1534 static Node *
1535 pull_up_simple_values(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
1536 {
1537  Query *parse = root->parse;
1538  int varno = ((RangeTblRef *) jtnode)->rtindex;
1539  List *values_list;
1540  List *tlist;
1541  AttrNumber attrno;
1542  pullup_replace_vars_context rvcontext;
1543  ListCell *lc;
1544 
1545  Assert(rte->rtekind == RTE_VALUES);
1546  Assert(list_length(rte->values_lists) == 1);
1547 
1548  /*
1549  * Need a modifiable copy of the VALUES list to hack on, just in case it's
1550  * multiply referenced.
1551  */
1552  values_list = copyObject(linitial(rte->values_lists));
1553 
1554  /*
1555  * The VALUES RTE can't contain any Vars of level zero, let alone any that
1556  * are join aliases, so no need to flatten join alias Vars.
1557  */
1558  Assert(!contain_vars_of_level((Node *) values_list, 0));
1559 
1560  /*
1561  * Set up required context data for pullup_replace_vars. In particular,
1562  * we have to make the VALUES list look like a subquery targetlist.
1563  */
1564  tlist = NIL;
1565  attrno = 1;
1566  foreach(lc, values_list)
1567  {
1568  tlist = lappend(tlist,
1569  makeTargetEntry((Expr *) lfirst(lc),
1570  attrno,
1571  NULL,
1572  false));
1573  attrno++;
1574  }
1575  rvcontext.root = root;
1576  rvcontext.targetlist = tlist;
1577  rvcontext.target_rte = rte;
1578  rvcontext.relids = NULL;
1579  rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
1580  rvcontext.varno = varno;
1581  rvcontext.need_phvs = false;
1582  rvcontext.wrap_non_vars = false;
1583  /* initialize cache array with indexes 0 .. length(tlist) */
1584  rvcontext.rv_cache = palloc0((list_length(tlist) + 1) *
1585  sizeof(Node *));
1586 
1587  /*
1588  * Replace all of the top query's references to the RTE's outputs with
1589  * copies of the adjusted VALUES expressions, being careful not to replace
1590  * any of the jointree structure. We can assume there's no outer joins or
1591  * appendrels in the dummy Query that surrounds a VALUES RTE.
1592  */
1593  perform_pullup_replace_vars(root, &rvcontext, NULL, NULL);
1594 
1595  /*
1596  * There should be no appendrels to fix, nor any outer joins and hence no
1597  * PlaceHolderVars.
1598  */
1599  Assert(root->append_rel_list == NIL);
1600  Assert(root->join_info_list == NIL);
1601  Assert(root->placeholder_list == NIL);
1602 
1603  /*
1604  * Replace the VALUES RTE with a RESULT RTE. The VALUES RTE is the only
1605  * rtable entry in the current query level, so this is easy.
1606  */
1607  Assert(list_length(parse->rtable) == 1);
1608 
1609  /* Create suitable RTE */
1610  rte = makeNode(RangeTblEntry);
1611  rte->rtekind = RTE_RESULT;
1612  rte->eref = makeAlias("*RESULT*", NIL);
1613 
1614  /* Replace rangetable */
1615  parse->rtable = list_make1(rte);
1616 
1617  /* We could manufacture a new RangeTblRef, but the one we have is fine */
1618  Assert(varno == 1);
1619 
1620  return jtnode;
1621 }
1622 
1623 /*
1624  * is_simple_values
1625  * Check a VALUES RTE in the range table to see if it's simple enough
1626  * to pull up into the parent query.
1627  *
1628  * rte is the RTE_VALUES RangeTblEntry to check.
1629  */
1630 static bool
1631 is_simple_values(PlannerInfo *root, RangeTblEntry *rte)
1632 {
1633  Assert(rte->rtekind == RTE_VALUES);
1634 
1635  /*
1636  * There must be exactly one VALUES list, else it's not semantically
1637  * correct to replace the VALUES RTE with a RESULT RTE, nor would we have
1638  * a unique set of expressions to substitute into the parent query.
1639  */
1640  if (list_length(rte->values_lists) != 1)
1641  return false;
1642 
1643  /*
1644  * Because VALUES can't appear under an outer join (or at least, we won't
1645  * try to pull it up if it does), we need not worry about LATERAL, nor
1646  * about validity of PHVs for the VALUES' outputs.
1647  */
1648 
1649  /*
1650  * Don't pull up a VALUES that contains any set-returning or volatile
1651  * functions. The considerations here are basically identical to the
1652  * restrictions on a pull-able subquery's targetlist.
1653  */
1654  if (expression_returns_set((Node *) rte->values_lists) ||
1655  contain_volatile_functions((Node *) rte->values_lists))
1656  return false;
1657 
1658  /*
1659  * Do not pull up a VALUES that's not the only RTE in its parent query.
1660  * This is actually the only case that the parser will generate at the
1661  * moment, and assuming this is true greatly simplifies
1662  * pull_up_simple_values().
1663  */
1664  if (list_length(root->parse->rtable) != 1 ||
1665  rte != (RangeTblEntry *) linitial(root->parse->rtable))
1666  return false;
1667 
1668  return true;
1669 }
1670 
1671 /*
1672  * pull_up_constant_function
1673  * Pull up an RTE_FUNCTION expression that was simplified to a constant.
1674  *
1675  * jtnode is a RangeTblRef that has been identified as a FUNCTION RTE by
1676  * pull_up_subqueries. If its expression is just a Const, hoist that value
1677  * up into the parent query, and replace the RTE_FUNCTION with RTE_RESULT.
1678  *
1679  * In principle we could pull up any immutable expression, but we don't.
1680  * That might result in multiple evaluations of the expression, which could
1681  * be costly if it's not just a Const. Also, the main value of this is
1682  * to let the constant participate in further const-folding, and of course
1683  * that won't happen for a non-Const.
1684  *
1685  * The pulled-up value might need to be wrapped in a PlaceHolderVar if the
1686  * RTE is below an outer join or is part of an appendrel; the extra
1687  * parameters show whether that's needed.
1688  */
1689 static Node *
1690 pull_up_constant_function(PlannerInfo *root, Node *jtnode,
1691  RangeTblEntry *rte,
1692  JoinExpr *lowest_nulling_outer_join,
1693  AppendRelInfo *containing_appendrel)
1694 {
1695  Query *parse = root->parse;
1696  RangeTblFunction *rtf;
1697  TypeFuncClass functypclass;
1698  Oid funcrettype;
1699  TupleDesc tupdesc;
1700  pullup_replace_vars_context rvcontext;
1701 
1702  /* Fail if the RTE has ORDINALITY - we don't implement that here. */
1703  if (rte->funcordinality)
1704  return jtnode;
1705 
1706  /* Fail if RTE isn't a single, simple Const expr */
1707  if (list_length(rte->functions) != 1)
1708  return jtnode;
1709  rtf = linitial_node(RangeTblFunction, rte->functions);
1710  if (!IsA(rtf->funcexpr, Const))
1711  return jtnode;
1712 
1713  /*
1714  * If the function's result is not a scalar, we punt. In principle we
1715  * could break the composite constant value apart into per-column
1716  * constants, but for now it seems not worth the work.
1717  */
1718  if (rtf->funccolcount != 1)
1719  return jtnode; /* definitely composite */
1720 
1721  functypclass = get_expr_result_type(rtf->funcexpr,
1722  &funcrettype,
1723  &tupdesc);
1724  if (functypclass != TYPEFUNC_SCALAR)
1725  return jtnode; /* must be a one-column composite type */
1726 
1727  /* Create context for applying pullup_replace_vars */
1728  rvcontext.root = root;
1729  rvcontext.targetlist = list_make1(makeTargetEntry((Expr *) rtf->funcexpr,
1730  1, /* resno */
1731  NULL, /* resname */
1732  false)); /* resjunk */
1733  rvcontext.target_rte = rte;
1734 
1735  /*
1736  * Since this function was reduced to a Const, it doesn't contain any
1737  * lateral references, even if it's marked as LATERAL. This means we
1738  * don't need to fill relids.
1739  */
1740  rvcontext.relids = NULL;
1741 
1742  rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
1743  rvcontext.varno = ((RangeTblRef *) jtnode)->rtindex;
1744  /* these flags will be set below, if needed */
1745  rvcontext.need_phvs = false;
1746  rvcontext.wrap_non_vars = false;
1747  /* initialize cache array with indexes 0 .. length(tlist) */
1748  rvcontext.rv_cache = palloc0((list_length(rvcontext.targetlist) + 1) *
1749  sizeof(Node *));
1750 
1751  /*
1752  * If we are under an outer join then non-nullable items and lateral
1753  * references may have to be turned into PlaceHolderVars.
1754  */
1755  if (lowest_nulling_outer_join != NULL)
1756  rvcontext.need_phvs = true;
1757 
1758  /*
1759  * If we are dealing with an appendrel member then anything that's not a
1760  * simple Var has to be turned into a PlaceHolderVar. (See comments in
1761  * pull_up_simple_subquery().)
1762  */
1763  if (containing_appendrel != NULL)
1764  {
1765  rvcontext.need_phvs = true;
1766  rvcontext.wrap_non_vars = true;
1767  }
1768 
1769  /*
1770  * If the parent query uses grouping sets, we need a PlaceHolderVar for
1771  * anything that's not a simple Var.
1772  */
1773  if (parse->groupingSets)
1774  {
1775  rvcontext.need_phvs = true;
1776  rvcontext.wrap_non_vars = true;
1777  }
1778 
1779  /*
1780  * Replace all of the top query's references to the RTE's output with
1781  * copies of the funcexpr, being careful not to replace any of the
1782  * jointree structure.
1783  */
1784  perform_pullup_replace_vars(root, &rvcontext,
1785  lowest_nulling_outer_join,
1786  containing_appendrel);
1787 
1788  /*
1789  * We don't need to bother with changing PlaceHolderVars in the parent
1790  * query. Their references to the RT index are still good for now, and
1791  * will get removed later if we're able to drop the RTE_RESULT.
1792  */
1793 
1794  /*
1795  * Convert the RTE to be RTE_RESULT type, signifying that we don't need to
1796  * scan it anymore, and zero out RTE_FUNCTION-specific fields.
1797  */
1798  rte->rtekind = RTE_RESULT;
1799  rte->functions = NIL;
1800 
1801  /*
1802  * We can reuse the RangeTblRef node.
1803  */
1804  return jtnode;
1805 }
1806 
1807 /*
1808  * is_simple_union_all
1809  * Check a subquery to see if it's a simple UNION ALL.
1810  *
1811  * We require all the setops to be UNION ALL (no mixing) and there can't be
1812  * any datatype coercions involved, ie, all the leaf queries must emit the
1813  * same datatypes.
1814  */
1815 static bool
1816 is_simple_union_all(Query *subquery)
1817 {
1818  SetOperationStmt *topop;
1819 
1820  /* Let's just make sure it's a valid subselect ... */
1821  if (!IsA(subquery, Query) ||
1822  subquery->commandType != CMD_SELECT)
1823  elog(ERROR, "subquery is bogus");
1824 
1825  /* Is it a set-operation query at all? */
1826  topop = castNode(SetOperationStmt, subquery->setOperations);
1827  if (!topop)
1828  return false;
1829 
1830  /* Can't handle ORDER BY, LIMIT/OFFSET, locking, or WITH */
1831  if (subquery->sortClause ||
1832  subquery->limitOffset ||
1833  subquery->limitCount ||
1834  subquery->rowMarks ||
1835  subquery->cteList)
1836  return false;
1837 
1838  /* Recursively check the tree of set operations */
1839  return is_simple_union_all_recurse((Node *) topop, subquery,
1840  topop->colTypes);
1841 }
1842 
1843 static bool
1844 is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes)
1845 {
1846  if (IsA(setOp, RangeTblRef))
1847  {
1848  RangeTblRef *rtr = (RangeTblRef *) setOp;
1849  RangeTblEntry *rte = rt_fetch(rtr->rtindex, setOpQuery->rtable);
1850  Query *subquery = rte->subquery;
1851 
1852  Assert(subquery != NULL);
1853 
1854  /* Leaf nodes are OK if they match the toplevel column types */
1855  /* We don't have to compare typmods or collations here */
1856  return tlist_same_datatypes(subquery->targetList, colTypes, true);
1857  }
1858  else if (IsA(setOp, SetOperationStmt))
1859  {
1860  SetOperationStmt *op = (SetOperationStmt *) setOp;
1861 
1862  /* Must be UNION ALL */
1863  if (op->op != SETOP_UNION || !op->all)
1864  return false;
1865 
1866  /* Recurse to check inputs */
1867  return is_simple_union_all_recurse(op->larg, setOpQuery, colTypes) &&
1868  is_simple_union_all_recurse(op->rarg, setOpQuery, colTypes);
1869  }
1870  else
1871  {
1872  elog(ERROR, "unrecognized node type: %d",
1873  (int) nodeTag(setOp));
1874  return false; /* keep compiler quiet */
1875  }
1876 }
1877 
1878 /*
1879  * is_safe_append_member
1880  * Check a subquery that is a leaf of a UNION ALL appendrel to see if it's
1881  * safe to pull up.
1882  */
1883 static bool
1884 is_safe_append_member(Query *subquery)
1885 {
1886  FromExpr *jtnode;
1887 
1888  /*
1889  * It's only safe to pull up the child if its jointree contains exactly
1890  * one RTE, else the AppendRelInfo data structure breaks. The one base RTE
1891  * could be buried in several levels of FromExpr, however. Also, if the
1892  * child's jointree is completely empty, we can pull up because
1893  * pull_up_simple_subquery will insert a single RTE_RESULT RTE instead.
1894  *
1895  * Also, the child can't have any WHERE quals because there's no place to
1896  * put them in an appendrel. (This is a bit annoying...) If we didn't
1897  * need to check this, we'd just test whether get_relids_in_jointree()
1898  * yields a singleton set, to be more consistent with the coding of
1899  * fix_append_rel_relids().
1900  */
1901  jtnode = subquery->jointree;
1902  Assert(IsA(jtnode, FromExpr));
1903  /* Check the completely-empty case */
1904  if (jtnode->fromlist == NIL && jtnode->quals == NULL)
1905  return true;
1906  /* Check the more general case */
1907  while (IsA(jtnode, FromExpr))
1908  {
1909  if (jtnode->quals != NULL)
1910  return false;
1911  if (list_length(jtnode->fromlist) != 1)
1912  return false;
1913  jtnode = linitial(jtnode->fromlist);
1914  }
1915  if (!IsA(jtnode, RangeTblRef))
1916  return false;
1917 
1918  return true;
1919 }
1920 
1921 /*
1922  * jointree_contains_lateral_outer_refs
1923  * Check for disallowed lateral references in a jointree's quals
1924  *
1925  * If restricted is false, all level-1 Vars are allowed (but we still must
1926  * search the jointree, since it might contain outer joins below which there
1927  * will be restrictions). If restricted is true, return true when any qual
1928  * in the jointree contains level-1 Vars coming from outside the rels listed
1929  * in safe_upper_varnos.
1930  */
1931 static bool
1932 jointree_contains_lateral_outer_refs(Node *jtnode, bool restricted,
1933  Relids safe_upper_varnos)
1934 {
1935  if (jtnode == NULL)
1936  return false;
1937  if (IsA(jtnode, RangeTblRef))
1938  return false;
1939  else if (IsA(jtnode, FromExpr))
1940  {
1941  FromExpr *f = (FromExpr *) jtnode;
1942  ListCell *l;
1943 
1944  /* First, recurse to check child joins */
1945  foreach(l, f->fromlist)
1946  {
1947  if (jointree_contains_lateral_outer_refs(lfirst(l),
1948  restricted,
1949  safe_upper_varnos))
1950  return true;
1951  }
1952 
1953  /* Then check the top-level quals */
1954  if (restricted &&
1955  !bms_is_subset(pull_varnos_of_level(f->quals, 1),
1956  safe_upper_varnos))
1957  return true;
1958  }
1959  else if (IsA(jtnode, JoinExpr))
1960  {
1961  JoinExpr *j = (JoinExpr *) jtnode;
1962 
1963  /*
1964  * If this is an outer join, we mustn't allow any upper lateral
1965  * references in or below it.
1966  */
1967  if (j->jointype != JOIN_INNER)
1968  {
1969  restricted = true;
1970  safe_upper_varnos = NULL;
1971  }
1972 
1973  /* Check the child joins */
1974  if (jointree_contains_lateral_outer_refs(j->larg,
1975  restricted,
1976  safe_upper_varnos))
1977  return true;
1978  if (jointree_contains_lateral_outer_refs(j->rarg,
1979  restricted,
1980  safe_upper_varnos))
1981  return true;
1982 
1983  /* Check the JOIN's qual clauses */
1984  if (restricted &&
1985  !bms_is_subset(pull_varnos_of_level(j->quals, 1),
1986  safe_upper_varnos))
1987  return true;
1988  }
1989  else
1990  elog(ERROR, "unrecognized node type: %d",
1991  (int) nodeTag(jtnode));
1992  return false;
1993 }
1994 
1995 /*
1996  * Perform pullup_replace_vars everyplace it's needed in the query tree.
1997  *
1998  * Caller has already filled *rvcontext with data describing what to
1999  * substitute for Vars referencing the target subquery. In addition
2000  * we need the identity of the lowest outer join that can null the
2001  * target subquery, and its containing appendrel if any.
2002  */
2003 static void
2004 perform_pullup_replace_vars(PlannerInfo *root,
2005  pullup_replace_vars_context *rvcontext,
2006  JoinExpr *lowest_nulling_outer_join,
2007  AppendRelInfo *containing_appendrel)
2008 {
2009  Query *parse = root->parse;
2010  ListCell *lc;
2011 
2012  /*
2013  * Replace all of the top query's references to the subquery's outputs
2014  * with copies of the adjusted subtlist items, being careful not to
2015  * replace any of the jointree structure. (This'd be a lot cleaner if we
2016  * could use query_tree_mutator.) We have to use PHVs in the targetList,
2017  * returningList, and havingQual, since those are certainly above any
2018  * outer join. replace_vars_in_jointree tracks its location in the
2019  * jointree and uses PHVs or not appropriately.
2020  */
2021  parse->targetList = (List *)
2022  pullup_replace_vars((Node *) parse->targetList, rvcontext);
2023  parse->returningList = (List *)
2024  pullup_replace_vars((Node *) parse->returningList, rvcontext);
2025  if (parse->onConflict)
2026  {
2027  parse->onConflict->onConflictSet = (List *)
2028  pullup_replace_vars((Node *) parse->onConflict->onConflictSet,
2029  rvcontext);
2030  parse->onConflict->onConflictWhere =
2031  pullup_replace_vars(parse->onConflict->onConflictWhere,
2032  rvcontext);
2033 
2034  /*
2035  * We assume ON CONFLICT's arbiterElems, arbiterWhere, exclRelTlist
2036  * can't contain any references to a subquery.
2037  */
2038  }
2039  replace_vars_in_jointree((Node *) parse->jointree, rvcontext,
2040  lowest_nulling_outer_join);
2041  Assert(parse->setOperations == NULL);
2042  parse->havingQual = pullup_replace_vars(parse->havingQual, rvcontext);
2043 
2044  /*
2045  * Replace references in the translated_vars lists of appendrels. When
2046  * pulling up an appendrel member, we do not need PHVs in the list of the
2047  * parent appendrel --- there isn't any outer join between. Elsewhere,
2048  * use PHVs for safety. (This analysis could be made tighter but it seems
2049  * unlikely to be worth much trouble.)
2050  */
2051  foreach(lc, root->append_rel_list)
2052  {
2053  AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
2054  bool save_need_phvs = rvcontext->need_phvs;
2055 
2056  if (appinfo == containing_appendrel)
2057  rvcontext->need_phvs = false;
2058  appinfo->translated_vars = (List *)
2059  pullup_replace_vars((Node *) appinfo->translated_vars, rvcontext);
2060  rvcontext->need_phvs = save_need_phvs;
2061  }
2062 
2063  /*
2064  * Replace references in the joinaliasvars lists of join RTEs.
2065  *
2066  * You might think that we could avoid using PHVs for alias vars of joins
2067  * below lowest_nulling_outer_join, but that doesn't work because the
2068  * alias vars could be referenced above that join; we need the PHVs to be
2069  * present in such references after the alias vars get flattened. (It
2070  * might be worth trying to be smarter here, someday.)
2071  */
2072  foreach(lc, parse->rtable)
2073  {
2074  RangeTblEntry *otherrte = (RangeTblEntry *) lfirst(lc);
2075 
2076  if (otherrte->rtekind == RTE_JOIN)
2077  otherrte->joinaliasvars = (List *)
2078  pullup_replace_vars((Node *) otherrte->joinaliasvars,
2079  rvcontext);
2080  }
2081 }
2082 
2083 /*
2084  * Helper routine for perform_pullup_replace_vars: do pullup_replace_vars on
2085  * every expression in the jointree, without changing the jointree structure
2086  * itself. Ugly, but there's no other way...
2087  *
2088  * If we are at or below lowest_nulling_outer_join, we can suppress use of
2089  * PlaceHolderVars wrapped around the replacement expressions.
2090  */
2091 static void
2092 replace_vars_in_jointree(Node *jtnode,
2093  pullup_replace_vars_context *context,
2094  JoinExpr *lowest_nulling_outer_join)
2095 {
2096  if (jtnode == NULL)
2097  return;
2098  if (IsA(jtnode, RangeTblRef))
2099  {
2100  /*
2101  * If the RangeTblRef refers to a LATERAL subquery (that isn't the
2102  * same subquery we're pulling up), it might contain references to the
2103  * target subquery, which we must replace. We drive this from the
2104  * jointree scan, rather than a scan of the rtable, for a couple of
2105  * reasons: we can avoid processing no-longer-referenced RTEs, and we
2106  * can use the appropriate setting of need_phvs depending on whether
2107  * the RTE is above possibly-nulling outer joins or not.
2108  */
2109  int varno = ((RangeTblRef *) jtnode)->rtindex;
2110 
2111  if (varno != context->varno) /* ignore target subquery itself */
2112  {
2113  RangeTblEntry *rte = rt_fetch(varno, context->root->parse->rtable);
2114 
2115  Assert(rte != context->target_rte);
2116  if (rte->lateral)
2117  {
2118  switch (rte->rtekind)
2119  {
2120  case RTE_RELATION:
2121  /* shouldn't be marked LATERAL unless tablesample */
2122  Assert(rte->tablesample);
2123  rte->tablesample = (TableSampleClause *)
2124  pullup_replace_vars((Node *) rte->tablesample,
2125  context);
2126  break;
2127  case RTE_SUBQUERY:
2128  rte->subquery =
2129  pullup_replace_vars_subquery(rte->subquery,
2130  context);
2131  break;
2132  case RTE_FUNCTION:
2133  rte->functions = (List *)
2134  pullup_replace_vars((Node *) rte->functions,
2135  context);
2136  break;
2137  case RTE_TABLEFUNC:
2138  rte->tablefunc = (TableFunc *)
2139  pullup_replace_vars((Node *) rte->tablefunc,
2140  context);
2141  break;
2142  case RTE_VALUES:
2143  rte->values_lists = (List *)
2144  pullup_replace_vars((Node *) rte->values_lists,
2145  context);
2146  break;
2147  case RTE_JOIN:
2148  case RTE_CTE:
2149  case RTE_NAMEDTUPLESTORE:
2150  case RTE_RESULT:
2151  /* these shouldn't be marked LATERAL */
2152  Assert(false);
2153  break;
2154  }
2155  }
2156  }
2157  }
2158  else if (IsA(jtnode, FromExpr))
2159  {
2160  FromExpr *f = (FromExpr *) jtnode;
2161  ListCell *l;
2162 
2163  foreach(l, f->fromlist)
2164  replace_vars_in_jointree(lfirst(l), context,
2165  lowest_nulling_outer_join);
2166  f->quals = pullup_replace_vars(f->quals, context);
2167  }
2168  else if (IsA(jtnode, JoinExpr))
2169  {
2170  JoinExpr *j = (JoinExpr *) jtnode;
2171  bool save_need_phvs = context->need_phvs;
2172 
2173  if (j == lowest_nulling_outer_join)
2174  {
2175  /* no more PHVs in or below this join */
2176  context->need_phvs = false;
2177  lowest_nulling_outer_join = NULL;
2178  }
2179  replace_vars_in_jointree(j->larg, context, lowest_nulling_outer_join);
2180  replace_vars_in_jointree(j->rarg, context, lowest_nulling_outer_join);
2181 
2182  /*
2183  * Use PHVs within the join quals of a full join, even when it's the
2184  * lowest nulling outer join. Otherwise, we cannot identify which
2185  * side of the join a pulled-up var-free expression came from, which
2186  * can lead to failure to make a plan at all because none of the quals
2187  * appear to be mergeable or hashable conditions. For this purpose we
2188  * don't care about the state of wrap_non_vars, so leave it alone.
2189  */
2190  if (j->jointype == JOIN_FULL)
2191  context->need_phvs = true;
2192 
2193  j->quals = pullup_replace_vars(j->quals, context);
2194 
2195  /*
2196  * We don't bother to update the colvars list, since it won't be used
2197  * again ...
2198  */
2199  context->need_phvs = save_need_phvs;
2200  }
2201  else
2202  elog(ERROR, "unrecognized node type: %d",
2203  (int) nodeTag(jtnode));
2204 }
2205 
2206 /*
2207  * Apply pullup variable replacement throughout an expression tree
2208  *
2209  * Returns a modified copy of the tree, so this can't be used where we
2210  * need to do in-place replacement.
2211  */
2212 static Node *
2213 pullup_replace_vars(Node *expr, pullup_replace_vars_context *context)
2214 {
2215  return replace_rte_variables(expr,
2216  context->varno, 0,
2217  pullup_replace_vars_callback,
2218  (void *) context,
2219  context->outer_hasSubLinks);
2220 }
2221 
2222 static Node *
2223 pullup_replace_vars_callback(Var *var,
2224  replace_rte_variables_context *context)
2225 {
2226  pullup_replace_vars_context *rcon = (pullup_replace_vars_context *) context->callback_arg;
2227  int varattno = var->varattno;
2228  Node *newnode;
2229 
2230  /*
2231  * If PlaceHolderVars are needed, we cache the modified expressions in
2232  * rcon->rv_cache[]. This is not in hopes of any material speed gain
2233  * within this function, but to avoid generating identical PHVs with
2234  * different IDs. That would result in duplicate evaluations at runtime,
2235  * and possibly prevent optimizations that rely on recognizing different
2236  * references to the same subquery output as being equal(). So it's worth
2237  * a bit of extra effort to avoid it.
2238  */
2239  if (rcon->need_phvs &&
2240  varattno >= InvalidAttrNumber &&
2241  varattno <= list_length(rcon->targetlist) &&
2242  rcon->rv_cache[varattno] != NULL)
2243  {
2244  /* Just copy the entry and fall through to adjust its varlevelsup */
2245  newnode = copyObject(rcon->rv_cache[varattno]);
2246  }
2247  else if (varattno == InvalidAttrNumber)
2248  {
2249  /* Must expand whole-tuple reference into RowExpr */
2250  RowExpr *rowexpr;
2251  List *colnames;
2252  List *fields;
2253  bool save_need_phvs = rcon->need_phvs;
2254  int save_sublevelsup = context->sublevels_up;
2255 
2256  /*
2257  * If generating an expansion for a var of a named rowtype (ie, this
2258  * is a plain relation RTE), then we must include dummy items for
2259  * dropped columns. If the var is RECORD (ie, this is a JOIN), then
2260  * omit dropped columns. Either way, attach column names to the
2261  * RowExpr for use of ruleutils.c.
2262  *
2263  * In order to be able to cache the results, we always generate the
2264  * expansion with varlevelsup = 0, and then adjust if needed.
2265  */
2266  expandRTE(rcon->target_rte,
2267  var->varno, 0 /* not varlevelsup */ , var->location,
2268  (var->vartype != RECORDOID),
2269  &colnames, &fields);
2270  /* Adjust the generated per-field Vars, but don't insert PHVs */
2271  rcon->need_phvs = false;
2272  context->sublevels_up = 0; /* to match the expandRTE output */
2273  fields = (List *) replace_rte_variables_mutator((Node *) fields,
2274  context);
2275  rcon->need_phvs = save_need_phvs;
2276  context->sublevels_up = save_sublevelsup;
2277 
2278  rowexpr = makeNode(RowExpr);
2279  rowexpr->args = fields;
2280  rowexpr->row_typeid = var->vartype;
2281  rowexpr->row_format = COERCE_IMPLICIT_CAST;
2282  rowexpr->colnames = colnames;
2283  rowexpr->location = var->location;
2284  newnode = (Node *) rowexpr;
2285 
2286  /*
2287  * Insert PlaceHolderVar if needed. Notice that we are wrapping one
2288  * PlaceHolderVar around the whole RowExpr, rather than putting one
2289  * around each element of the row. This is because we need the
2290  * expression to yield NULL, not ROW(NULL,NULL,...) when it is forced
2291  * to null by an outer join.
2292  */
2293  if (rcon->need_phvs)
2294  {
2295  /* RowExpr is certainly not strict, so always need PHV */
2296  newnode = (Node *)
2297  make_placeholder_expr(rcon->root,
2298  (Expr *) newnode,
2299  bms_make_singleton(rcon->varno));
2300  /* cache it with the PHV, and with varlevelsup still zero */
2301  rcon->rv_cache[InvalidAttrNumber] = copyObject(newnode);
2302  }
2303  }
2304  else
2305  {
2306  /* Normal case referencing one targetlist element */
2307  TargetEntry *tle = get_tle_by_resno(rcon->targetlist, varattno);
2308 
2309  if (tle == NULL) /* shouldn't happen */
2310  elog(ERROR, "could not find attribute %d in subquery targetlist",
2311  varattno);
2312 
2313  /* Make a copy of the tlist item to return */
2314  newnode = (Node *) copyObject(tle->expr);
2315 
2316  /* Insert PlaceHolderVar if needed */
2317  if (rcon->need_phvs)
2318  {
2319  bool wrap;
2320 
2321  if (newnode && IsA(newnode, Var) &&
2322  ((Var *) newnode)->varlevelsup == 0)
2323  {
2324  /*
2325  * Simple Vars always escape being wrapped, unless they are
2326  * lateral references to something outside the subquery being
2327  * pulled up. (Even then, we could omit the PlaceHolderVar if
2328  * the referenced rel is under the same lowest outer join, but
2329  * it doesn't seem worth the trouble to check that.)
2330  */
2331  if (rcon->target_rte->lateral &&
2332  !bms_is_member(((Var *) newnode)->varno, rcon->relids))
2333  wrap = true;
2334  else
2335  wrap = false;
2336  }
2337  else if (newnode && IsA(newnode, PlaceHolderVar) &&
2338  ((PlaceHolderVar *) newnode)->phlevelsup == 0)
2339  {
2340  /* No need to wrap a PlaceHolderVar with another one, either */
2341  wrap = false;
2342  }
2343  else if (rcon->wrap_non_vars)
2344  {
2345  /* Wrap all non-Vars in a PlaceHolderVar */
2346  wrap = true;
2347  }
2348  else
2349  {
2350  /*
2351  * If it contains a Var of the subquery being pulled up, and
2352  * does not contain any non-strict constructs, then it's
2353  * certainly nullable so we don't need to insert a
2354  * PlaceHolderVar.
2355  *
2356  * This analysis could be tighter: in particular, a non-strict
2357  * construct hidden within a lower-level PlaceHolderVar is not
2358  * reason to add another PHV. But for now it doesn't seem
2359  * worth the code to be more exact.
2360  *
2361  * Note: in future maybe we should insert a PlaceHolderVar
2362  * anyway, if the tlist item is expensive to evaluate?
2363  *
2364  * For a LATERAL subquery, we have to check the actual var
2365  * membership of the node, but if it's non-lateral then any
2366  * level-zero var must belong to the subquery.
2367  */
2368  if ((rcon->target_rte->lateral ?
2369  bms_overlap(pull_varnos((Node *) newnode), rcon->relids) :
2370  contain_vars_of_level((Node *) newnode, 0)) &&
2371  !contain_nonstrict_functions((Node *) newnode))
2372  {
2373  /* No wrap needed */
2374  wrap = false;
2375  }
2376  else
2377  {
2378  /* Else wrap it in a PlaceHolderVar */
2379  wrap = true;
2380  }
2381  }
2382 
2383  if (wrap)
2384  newnode = (Node *)
2385  make_placeholder_expr(rcon->root,
2386  (Expr *) newnode,
2387  bms_make_singleton(rcon->varno));
2388 
2389  /*
2390  * Cache it if possible (ie, if the attno is in range, which it
2391  * probably always should be). We can cache the value even if we
2392  * decided we didn't need a PHV, since this result will be
2393  * suitable for any request that has need_phvs.
2394  */
2395  if (varattno > InvalidAttrNumber &&
2396  varattno <= list_length(rcon->targetlist))
2397  rcon->rv_cache[varattno] = copyObject(newnode);
2398  }
2399  }
2400 
2401  /* Must adjust varlevelsup if tlist item is from higher query */
2402  if (var->varlevelsup > 0)
2403  IncrementVarSublevelsUp(newnode, var->varlevelsup, 0);
2404 
2405  return newnode;
2406 }
2407 
2408 /*
2409  * Apply pullup variable replacement to a subquery
2410  *
2411  * This needs to be different from pullup_replace_vars() because
2412  * replace_rte_variables will think that it shouldn't increment sublevels_up
2413  * before entering the Query; so we need to call it with sublevels_up == 1.
2414  */
2415 static Query *
2416 pullup_replace_vars_subquery(Query *query,
2417  pullup_replace_vars_context *context)
2418 {
2419  Assert(IsA(query, Query));
2420  return (Query *) replace_rte_variables((Node *) query,
2421  context->varno, 1,
2422  pullup_replace_vars_callback,
2423  (void *) context,
2424  NULL);
2425 }
2426 
2427 
2428 /*
2429  * flatten_simple_union_all
2430  * Try to optimize top-level UNION ALL structure into an appendrel
2431  *
2432  * If a query's setOperations tree consists entirely of simple UNION ALL
2433  * operations, flatten it into an append relation, which we can process more
2434  * intelligently than the general setops case. Otherwise, do nothing.
2435  *
2436  * In most cases, this can succeed only for a top-level query, because for a
2437  * subquery in FROM, the parent query's invocation of pull_up_subqueries would
2438  * already have flattened the UNION via pull_up_simple_union_all. But there
2439  * are a few cases we can support here but not in that code path, for example
2440  * when the subquery also contains ORDER BY.
2441  */
2442 void
2443 flatten_simple_union_all(PlannerInfo *root)
2444 {
2445  Query *parse = root->parse;
2446  SetOperationStmt *topop;
2447  Node *leftmostjtnode;
2448  int leftmostRTI;
2449  RangeTblEntry *leftmostRTE;
2450  int childRTI;
2451  RangeTblEntry *childRTE;
2452  RangeTblRef *rtr;
2453 
2454  /* Shouldn't be called unless query has setops */
2455  topop = castNode(SetOperationStmt, parse->setOperations);
2456  Assert(topop);
2457 
2458  /* Can't optimize away a recursive UNION */
2459  if (root->hasRecursion)
2460  return;
2461 
2462  /*
2463  * Recursively check the tree of set operations. If not all UNION ALL
2464  * with identical column types, punt.
2465  */
2466  if (!is_simple_union_all_recurse((Node *) topop, parse, topop->colTypes))
2467  return;
2468 
2469  /*
2470  * Locate the leftmost leaf query in the setops tree. The upper query's
2471  * Vars all refer to this RTE (see transformSetOperationStmt).
2472  */
2473  leftmostjtnode = topop->larg;
2474  while (leftmostjtnode && IsA(leftmostjtnode, SetOperationStmt))
2475  leftmostjtnode = ((SetOperationStmt *) leftmostjtnode)->larg;
2476  Assert(leftmostjtnode && IsA(leftmostjtnode, RangeTblRef));
2477  leftmostRTI = ((RangeTblRef *) leftmostjtnode)->rtindex;
2478  leftmostRTE = rt_fetch(leftmostRTI, parse->rtable);
2479  Assert(leftmostRTE->rtekind == RTE_SUBQUERY);
2480 
2481  /*
2482  * Make a copy of the leftmost RTE and add it to the rtable. This copy
2483  * will represent the leftmost leaf query in its capacity as a member of
2484  * the appendrel. The original will represent the appendrel as a whole.
2485  * (We must do things this way because the upper query's Vars have to be
2486  * seen as referring to the whole appendrel.)
2487  */
2488  childRTE = copyObject(leftmostRTE);
2489  parse->rtable = lappend(parse->rtable, childRTE);
2490  childRTI = list_length(parse->rtable);
2491 
2492  /* Modify the setops tree to reference the child copy */
2493  ((RangeTblRef *) leftmostjtnode)->rtindex = childRTI;
2494 
2495  /* Modify the formerly-leftmost RTE to mark it as an appendrel parent */
2496  leftmostRTE->inh = true;
2497 
2498  /*
2499  * Form a RangeTblRef for the appendrel, and insert it into FROM. The top
2500  * Query of a setops tree should have had an empty FromClause initially.
2501  */
2502  rtr = makeNode(RangeTblRef);
2503  rtr->rtindex = leftmostRTI;
2504  Assert(parse->jointree->fromlist == NIL);
2505  parse->jointree->fromlist = list_make1(rtr);
2506 
2507  /*
2508  * Now pretend the query has no setops. We must do this before trying to
2509  * do subquery pullup, because of Assert in pull_up_simple_subquery.
2510  */
2511  parse->setOperations = NULL;
2512 
2513  /*
2514  * Build AppendRelInfo information, and apply pull_up_subqueries to the
2515  * leaf queries of the UNION ALL. (We must do that now because they
2516  * weren't previously referenced by the jointree, and so were missed by
2517  * the main invocation of pull_up_subqueries.)
2518  */
2519  pull_up_union_leaf_queries((Node *) topop, root, leftmostRTI, parse, 0);
2520 }
2521 
2522 
2523 /*
2524  * reduce_outer_joins
2525  * Attempt to reduce outer joins to plain inner joins.
2526  *
2527  * The idea here is that given a query like
2528  * SELECT ... FROM a LEFT JOIN b ON (...) WHERE b.y = 42;
2529  * we can reduce the LEFT JOIN to a plain JOIN if the "=" operator in WHERE
2530  * is strict. The strict operator will always return NULL, causing the outer
2531  * WHERE to fail, on any row where the LEFT JOIN filled in NULLs for b's
2532  * columns. Therefore, there's no need for the join to produce null-extended
2533  * rows in the first place --- which makes it a plain join not an outer join.
2534  * (This scenario may not be very likely in a query written out by hand, but
2535  * it's reasonably likely when pushing quals down into complex views.)
2536  *
2537  * More generally, an outer join can be reduced in strength if there is a
2538  * strict qual above it in the qual tree that constrains a Var from the
2539  * nullable side of the join to be non-null. (For FULL joins this applies
2540  * to each side separately.)
2541  *
2542  * Another transformation we apply here is to recognize cases like
2543  * SELECT ... FROM a LEFT JOIN b ON (a.x = b.y) WHERE b.y IS NULL;
2544  * If the join clause is strict for b.y, then only null-extended rows could
2545  * pass the upper WHERE, and we can conclude that what the query is really
2546  * specifying is an anti-semijoin. We change the join type from JOIN_LEFT
2547  * to JOIN_ANTI. The IS NULL clause then becomes redundant, and must be
2548  * removed to prevent bogus selectivity calculations, but we leave it to
2549  * distribute_qual_to_rels to get rid of such clauses.
2550  *
2551  * Also, we get rid of JOIN_RIGHT cases by flipping them around to become
2552  * JOIN_LEFT. This saves some code here and in some later planner routines,
2553  * but the main reason to do it is to not need to invent a JOIN_REVERSE_ANTI
2554  * join type.
2555  *
2556  * To ease recognition of strict qual clauses, we require this routine to be
2557  * run after expression preprocessing (i.e., qual canonicalization and JOIN
2558  * alias-var expansion).
2559  */
2560 void
2561 reduce_outer_joins(PlannerInfo *root)
2562 {
2563  reduce_outer_joins_state *state;
2564 
2565  /*
2566  * To avoid doing strictness checks on more quals than necessary, we want
2567  * to stop descending the jointree as soon as there are no outer joins
2568  * below our current point. This consideration forces a two-pass process.
2569  * The first pass gathers information about which base rels appear below
2570  * each side of each join clause, and about whether there are outer
2571  * join(s) below each side of each join clause. The second pass examines
2572  * qual clauses and changes join types as it descends the tree.
2573  */
2574  state = reduce_outer_joins_pass1((Node *) root->parse->jointree);
2575 
2576  /* planner.c shouldn't have called me if no outer joins */
2577  if (state == NULL || !state->contains_outer)
2578  elog(ERROR, "so where are the outer joins?");
2579 
2580  reduce_outer_joins_pass2((Node *) root->parse->jointree,
2581  state, root, NULL, NIL, NIL);
2582 }
2583 
2584 /*
2585  * reduce_outer_joins_pass1 - phase 1 data collection
2586  *
2587  * Returns a state node describing the given jointree node.
2588  */
2589 static reduce_outer_joins_state *
2590 reduce_outer_joins_pass1(Node *jtnode)
2591 {
2592  reduce_outer_joins_state *result;
2593 
2594  result = (reduce_outer_joins_state *)
2595  palloc(sizeof(reduce_outer_joins_state));
2596  result->relids = NULL;
2597  result->contains_outer = false;
2598  result->sub_states = NIL;
2599 
2600  if (jtnode == NULL)
2601  return result;
2602  if (IsA(jtnode, RangeTblRef))
2603  {
2604  int varno = ((RangeTblRef *) jtnode)->rtindex;
2605 
2606  result->relids = bms_make_singleton(varno);
2607  }
2608  else if (IsA(jtnode, FromExpr))
2609  {
2610  FromExpr *f = (FromExpr *) jtnode;
2611  ListCell *l;
2612 
2613  foreach(l, f->fromlist)
2614  {
2615  reduce_outer_joins_state *sub_state;
2616 
2617  sub_state = reduce_outer_joins_pass1(lfirst(l));
2618  result->relids = bms_add_members(result->relids,
2619  sub_state->relids);
2620  result->contains_outer |= sub_state->contains_outer;
2621  result->sub_states = lappend(result->sub_states, sub_state);
2622  }
2623  }
2624  else if (IsA(jtnode, JoinExpr))
2625  {
2626  JoinExpr *j = (JoinExpr *) jtnode;
2627  reduce_outer_joins_state *sub_state;
2628 
2629  /* join's own RT index is not wanted in result->relids */
2630  if (IS_OUTER_JOIN(j->jointype))
2631  result->contains_outer = true;
2632 
2633  sub_state = reduce_outer_joins_pass1(j->larg);
2634  result->relids = bms_add_members(result->relids,
2635  sub_state->relids);
2636  result->contains_outer |= sub_state->contains_outer;
2637  result->sub_states = lappend(result->sub_states, sub_state);
2638 
2639  sub_state = reduce_outer_joins_pass1(j->rarg);
2640  result->relids = bms_add_members(result->relids,
2641  sub_state->relids);
2642  result->contains_outer |= sub_state->contains_outer;
2643  result->sub_states = lappend(result->sub_states, sub_state);
2644  }
2645  else
2646  elog(ERROR, "unrecognized node type: %d",
2647  (int) nodeTag(jtnode));
2648  return result;
2649 }
2650 
2651 /*
2652  * reduce_outer_joins_pass2 - phase 2 processing
2653  *
2654  * jtnode: current jointree node
2655  * state: state data collected by phase 1 for this node
2656  * root: toplevel planner state
2657  * nonnullable_rels: set of base relids forced non-null by upper quals
2658  * nonnullable_vars: list of Vars forced non-null by upper quals
2659  * forced_null_vars: list of Vars forced null by upper quals
2660  */
2661 static void
2662 reduce_outer_joins_pass2(Node *jtnode,
2663  reduce_outer_joins_state *state,
2664  PlannerInfo *root,
2665  Relids nonnullable_rels,
2666  List *nonnullable_vars,
2667  List *forced_null_vars)
2668 {
2669  /*
2670  * pass 2 should never descend as far as an empty subnode or base rel,
2671  * because it's only called on subtrees marked as contains_outer.
2672  */
2673  if (jtnode == NULL)
2674  elog(ERROR, "reached empty jointree");
2675  if (IsA(jtnode, RangeTblRef))
2676  elog(ERROR, "reached base rel");
2677  else if (IsA(jtnode, FromExpr))
2678  {
2679  FromExpr *f = (FromExpr *) jtnode;
2680  ListCell *l;
2681  ListCell *s;
2682  Relids pass_nonnullable_rels;
2683  List *pass_nonnullable_vars;
2684  List *pass_forced_null_vars;
2685 
2686  /* Scan quals to see if we can add any constraints */
2687  pass_nonnullable_rels = find_nonnullable_rels(f->quals);
2688  pass_nonnullable_rels = bms_add_members(pass_nonnullable_rels,
2689  nonnullable_rels);
2690  pass_nonnullable_vars = find_nonnullable_vars(f->quals);
2691  pass_nonnullable_vars = list_concat(pass_nonnullable_vars,
2692  nonnullable_vars);
2693  pass_forced_null_vars = find_forced_null_vars(f->quals);
2694  pass_forced_null_vars = list_concat(pass_forced_null_vars,
2695  forced_null_vars);
2696  /* And recurse --- but only into interesting subtrees */
2697  Assert(list_length(f->fromlist) == list_length(state->sub_states));
2698  forboth(l, f->fromlist, s, state->sub_states)
2699  {
2700  reduce_outer_joins_state *sub_state = lfirst(s);
2701 
2702  if (sub_state->contains_outer)
2703  reduce_outer_joins_pass2(lfirst(l), sub_state, root,
2704  pass_nonnullable_rels,
2705  pass_nonnullable_vars,
2706  pass_forced_null_vars);
2707  }
2708  bms_free(pass_nonnullable_rels);
2709  /* can't so easily clean up var lists, unfortunately */
2710  }
2711  else if (IsA(jtnode, JoinExpr))
2712  {
2713  JoinExpr *j = (JoinExpr *) jtnode;
2714  int rtindex = j->rtindex;
2715  JoinType jointype = j->jointype;
2716  reduce_outer_joins_state *left_state = linitial(state->sub_states);
2717  reduce_outer_joins_state *right_state = lsecond(state->sub_states);
2718  List *local_nonnullable_vars = NIL;
2719  bool computed_local_nonnullable_vars = false;
2720 
2721  /* Can we simplify this join? */
2722  switch (jointype)
2723  {
2724  case JOIN_INNER:
2725  break;
2726  case JOIN_LEFT:
2727  if (bms_overlap(nonnullable_rels, right_state->relids))
2728  jointype = JOIN_INNER;
2729  break;
2730  case JOIN_RIGHT:
2731  if (bms_overlap(nonnullable_rels, left_state->relids))
2732  jointype = JOIN_INNER;
2733  break;
2734  case JOIN_FULL:
2735  if (bms_overlap(nonnullable_rels, left_state->relids))
2736  {
2737  if (bms_overlap(nonnullable_rels, right_state->relids))
2738  jointype = JOIN_INNER;
2739  else
2740  jointype = JOIN_LEFT;
2741  }
2742  else
2743  {
2744  if (bms_overlap(nonnullable_rels, right_state->relids))
2745  jointype = JOIN_RIGHT;
2746  }
2747  break;
2748  case JOIN_SEMI:
2749  case JOIN_ANTI:
2750 
2751  /*
2752  * These could only have been introduced by pull_up_sublinks,
2753  * so there's no way that upper quals could refer to their
2754  * righthand sides, and no point in checking.
2755  */
2756  break;
2757  default:
2758  elog(ERROR, "unrecognized join type: %d",
2759  (int) jointype);
2760  break;
2761  }
2762 
2763  /*
2764  * Convert JOIN_RIGHT to JOIN_LEFT. Note that in the case where we
2765  * reduced JOIN_FULL to JOIN_RIGHT, this will mean the JoinExpr no
2766  * longer matches the internal ordering of any CoalesceExpr's built to
2767  * represent merged join variables. We don't care about that at
2768  * present, but be wary of it ...
2769  */
2770  if (jointype == JOIN_RIGHT)
2771  {
2772  Node *tmparg;
2773 
2774  tmparg = j->larg;
2775  j->larg = j->rarg;
2776  j->rarg = tmparg;
2777  jointype = JOIN_LEFT;
2778  right_state = linitial(state->sub_states);
2779  left_state = lsecond(state->sub_states);
2780  }
2781 
2782  /*
2783  * See if we can reduce JOIN_LEFT to JOIN_ANTI. This is the case if
2784  * the join's own quals are strict for any var that was forced null by
2785  * higher qual levels. NOTE: there are other ways that we could
2786  * detect an anti-join, in particular if we were to check whether Vars
2787  * coming from the RHS must be non-null because of table constraints.
2788  * That seems complicated and expensive though (in particular, one
2789  * would have to be wary of lower outer joins). For the moment this
2790  * seems sufficient.
2791  */
2792  if (jointype == JOIN_LEFT)
2793  {
2794  List *overlap;
2795 
2796  local_nonnullable_vars = find_nonnullable_vars(j->quals);
2797  computed_local_nonnullable_vars = true;
2798 
2799  /*
2800  * It's not sufficient to check whether local_nonnullable_vars and
2801  * forced_null_vars overlap: we need to know if the overlap
2802  * includes any RHS variables.
2803  */
2804  overlap = list_intersection(local_nonnullable_vars,
2805  forced_null_vars);
2806  if (overlap != NIL &&
2807  bms_overlap(pull_varnos((Node *) overlap),
2808  right_state->relids))
2809  jointype = JOIN_ANTI;
2810  }
2811 
2812  /* Apply the jointype change, if any, to both jointree node and RTE */
2813  if (rtindex && jointype != j->jointype)
2814  {
2815  RangeTblEntry *rte = rt_fetch(rtindex, root->parse->rtable);
2816 
2817  Assert(rte->rtekind == RTE_JOIN);
2818  Assert(rte->jointype == j->jointype);
2819  rte->jointype = jointype;
2820  }
2821  j->jointype = jointype;
2822 
2823  /* Only recurse if there's more to do below here */
2824  if (left_state->contains_outer || right_state->contains_outer)
2825  {
2826  Relids local_nonnullable_rels;
2827  List *local_forced_null_vars;
2828  Relids pass_nonnullable_rels;
2829  List *pass_nonnullable_vars;
2830  List *pass_forced_null_vars;
2831 
2832  /*
2833  * If this join is (now) inner, we can add any constraints its
2834  * quals provide to those we got from above. But if it is outer,
2835  * we can pass down the local constraints only into the nullable
2836  * side, because an outer join never eliminates any rows from its
2837  * non-nullable side. Also, there is no point in passing upper
2838  * constraints into the nullable side, since if there were any
2839  * we'd have been able to reduce the join. (In the case of upper
2840  * forced-null constraints, we *must not* pass them into the
2841  * nullable side --- they either applied here, or not.) The upshot
2842  * is that we pass either the local or the upper constraints,
2843  * never both, to the children of an outer join.
2844  *
2845  * Note that a SEMI join works like an inner join here: it's okay
2846  * to pass down both local and upper constraints. (There can't be
2847  * any upper constraints affecting its inner side, but it's not
2848  * worth having a separate code path to avoid passing them.)
2849  *
2850  * At a FULL join we just punt and pass nothing down --- is it
2851  * possible to be smarter?
2852  */
2853  if (jointype != JOIN_FULL)
2854  {
2855  local_nonnullable_rels = find_nonnullable_rels(j->quals);
2856  if (!computed_local_nonnullable_vars)
2857  local_nonnullable_vars = find_nonnullable_vars(j->quals);
2858  local_forced_null_vars = find_forced_null_vars(j->quals);
2859  if (jointype == JOIN_INNER || jointype == JOIN_SEMI)
2860  {
2861  /* OK to merge upper and local constraints */
2862  local_nonnullable_rels = bms_add_members(local_nonnullable_rels,
2863  nonnullable_rels);
2864  local_nonnullable_vars = list_concat(local_nonnullable_vars,
2865  nonnullable_vars);
2866  local_forced_null_vars = list_concat(local_forced_null_vars,
2867  forced_null_vars);
2868  }
2869  }
2870  else
2871  {
2872  /* no use in calculating these */
2873  local_nonnullable_rels = NULL;
2874  local_forced_null_vars = NIL;
2875  }
2876 
2877  if (left_state->contains_outer)
2878  {
2879  if (jointype == JOIN_INNER || jointype == JOIN_SEMI)
2880  {
2881  /* pass union of local and upper constraints */
2882  pass_nonnullable_rels = local_nonnullable_rels;
2883  pass_nonnullable_vars = local_nonnullable_vars;
2884  pass_forced_null_vars = local_forced_null_vars;
2885  }
2886  else if (jointype != JOIN_FULL) /* ie, LEFT or ANTI */
2887  {
2888  /* can't pass local constraints to non-nullable side */
2889  pass_nonnullable_rels = nonnullable_rels;
2890  pass_nonnullable_vars = nonnullable_vars;
2891  pass_forced_null_vars = forced_null_vars;
2892  }
2893  else
2894  {
2895  /* no constraints pass through JOIN_FULL */
2896  pass_nonnullable_rels = NULL;
2897  pass_nonnullable_vars = NIL;
2898  pass_forced_null_vars = NIL;
2899  }
2900  reduce_outer_joins_pass2(j->larg, left_state, root,
2901  pass_nonnullable_rels,
2902  pass_nonnullable_vars,
2903  pass_forced_null_vars);
2904  }
2905 
2906  if (right_state->contains_outer)
2907  {
2908  if (jointype != JOIN_FULL) /* ie, INNER/LEFT/SEMI/ANTI */
2909  {
2910  /* pass appropriate constraints, per comment above */
2911  pass_nonnullable_rels = local_nonnullable_rels;
2912  pass_nonnullable_vars = local_nonnullable_vars;
2913  pass_forced_null_vars = local_forced_null_vars;
2914  }
2915  else
2916  {
2917  /* no constraints pass through JOIN_FULL */
2918  pass_nonnullable_rels = NULL;
2919  pass_nonnullable_vars = NIL;
2920  pass_forced_null_vars = NIL;
2921  }
2922  reduce_outer_joins_pass2(j->rarg, right_state, root,
2923  pass_nonnullable_rels,
2924  pass_nonnullable_vars,
2925  pass_forced_null_vars);
2926  }
2927  bms_free(local_nonnullable_rels);
2928  }
2929  }
2930  else
2931  elog(ERROR, "unrecognized node type: %d",
2932  (int) nodeTag(jtnode));
2933 }
2934 
2935 
2936 /*
2937  * remove_useless_result_rtes
2938  * Attempt to remove RTE_RESULT RTEs from the join tree.
2939  *
2940  * We can remove RTE_RESULT entries from the join tree using the knowledge
2941  * that RTE_RESULT returns exactly one row and has no output columns. Hence,
2942  * if one is inner-joined to anything else, we can delete it. Optimizations
2943  * are also possible for some outer-join cases, as detailed below.
2944  *
2945  * Some of these optimizations depend on recognizing empty (constant-true)
2946  * quals for FromExprs and JoinExprs. That makes it useful to apply this
2947  * optimization pass after expression preprocessing, since that will have
2948  * eliminated constant-true quals, allowing more cases to be recognized as
2949  * optimizable. What's more, the usual reason for an RTE_RESULT to be present
2950  * is that we pulled up a subquery or VALUES clause, thus very possibly
2951  * replacing Vars with constants, making it more likely that a qual can be
2952  * reduced to constant true. Also, because some optimizations depend on
2953  * the outer-join type, it's best to have done reduce_outer_joins() first.
2954  *
2955  * A PlaceHolderVar referencing an RTE_RESULT RTE poses an obstacle to this
2956  * process: we must remove the RTE_RESULT's relid from the PHV's phrels, but
2957  * we must not reduce the phrels set to empty. If that would happen, and
2958  * the RTE_RESULT is an immediate child of an outer join, we have to give up
2959  * and not remove the RTE_RESULT: there is noplace else to evaluate the
2960  * PlaceHolderVar. (That is, in such cases the RTE_RESULT *does* have output
2961  * columns.) But if the RTE_RESULT is an immediate child of an inner join,
2962  * we can usually change the PlaceHolderVar's phrels so as to evaluate it at
2963  * the inner join instead. This is OK because we really only care that PHVs
2964  * are evaluated above or below the correct outer joins. We can't, however,
2965  * postpone the evaluation of a PHV to above where it is used; so there are
2966  * some checks below on whether output PHVs are laterally referenced in the
2967  * other join input rel(s).
2968  *
2969  * We used to try to do this work as part of pull_up_subqueries() where the
2970  * potentially-optimizable cases get introduced; but it's way simpler, and
2971  * more effective, to do it separately.
2972  */
2973 void
2974 remove_useless_result_rtes(PlannerInfo *root)
2975 {
2976  ListCell *cell;
2977 
2978  /* Top level of jointree must always be a FromExpr */
2979  Assert(IsA(root->parse->jointree, FromExpr));
2980  /* Recurse ... */
2981  root->parse->jointree = (FromExpr *)
2982  remove_useless_results_recurse(root, (Node *) root->parse->jointree);
2983  /* We should still have a FromExpr */
2984  Assert(IsA(root->parse->jointree, FromExpr));
2985 
2986  /*
2987  * Remove any PlanRowMark referencing an RTE_RESULT RTE. We obviously
2988  * must do that for any RTE_RESULT that we just removed. But one for a
2989  * RTE that we did not remove can be dropped anyway: since the RTE has
2990  * only one possible output row, there is no need for EPQ to mark and
2991  * restore that row.
2992  *
2993  * It's necessary, not optional, to remove the PlanRowMark for a surviving
2994  * RTE_RESULT RTE; otherwise we'll generate a whole-row Var for the
2995  * RTE_RESULT, which the executor has no support for.
2996  */
2997  foreach(cell, root->rowMarks)
2998  {
2999  PlanRowMark *rc = (PlanRowMark *) lfirst(cell);
3000 
3001  if (rt_fetch(rc->rti, root->parse->rtable)->rtekind == RTE_RESULT)
3002  root->rowMarks = foreach_delete_current(root->rowMarks, cell);
3003  }
3004 }
3005 
3006 /*
3007  * remove_useless_results_recurse
3008  * Recursive guts of remove_useless_result_rtes.
3009  *
3010  * This recursively processes the jointree and returns a modified jointree.
3011  */
3012 static Node *
3013 remove_useless_results_recurse(PlannerInfo *root, Node *jtnode)
3014 {
3015  Assert(jtnode != NULL);
3016  if (IsA(jtnode, RangeTblRef))
3017  {
3018  /* Can't immediately do anything with a RangeTblRef */
3019  }
3020  else if (IsA(jtnode, FromExpr))
3021  {
3022  FromExpr *f = (FromExpr *) jtnode;
3023  Relids result_relids = NULL;
3024  ListCell *cell;
3025 
3026  /*
3027  * We can drop RTE_RESULT rels from the fromlist so long as at least
3028  * one child remains, since joining to a one-row table changes
3029  * nothing. (But we can't drop a RTE_RESULT that computes PHV(s) that
3030  * are needed by some sibling. The cleanup transformation below would
3031  * reassign the PHVs to be computed at the join, which is too late for
3032  * the sibling's use.) The easiest way to mechanize this rule is to
3033  * modify the list in-place.
3034  */
3035  foreach(cell, f->fromlist)
3036  {
3037  Node *child = (Node *) lfirst(cell);
3038  int varno;
3039 
3040  /* Recursively transform child ... */
3041  child = remove_useless_results_recurse(root, child);
3042  /* ... and stick it back into the tree */
3043  lfirst(cell) = child;
3044 
3045  /*
3046  * If it's an RTE_RESULT with at least one sibling, and no sibling
3047  * references dependent PHVs, we can drop it. We don't yet know
3048  * what the inner join's final relid set will be, so postpone
3049  * cleanup of PHVs etc till after this loop.
3050  */
3051  if (list_length(f->fromlist) > 1 &&
3052  (varno = get_result_relid(root, child)) != 0 &&
3053  !find_dependent_phvs_in_jointree(root, (Node *) f, varno))
3054  {
3055  f->fromlist = foreach_delete_current(f->fromlist, cell);
3056  result_relids = bms_add_member(result_relids, varno);
3057  }
3058  }
3059 
3060  /*
3061  * Clean up if we dropped any RTE_RESULT RTEs. This is a bit
3062  * inefficient if there's more than one, but it seems better to
3063  * optimize the support code for the single-relid case.
3064  */
3065  if (result_relids)
3066  {
3067  int varno = -1;
3068 
3069  while ((varno = bms_next_member(result_relids, varno)) >= 0)
3070  remove_result_refs(root, varno, (Node *) f);
3071  }
3072 
3073  /*
3074  * If we're not at the top of the jointree, it's valid to simplify a
3075  * degenerate FromExpr into its single child. (At the top, we must
3076  * keep the FromExpr since Query.jointree is required to point to a
3077  * FromExpr.)
3078  */
3079  if (f != root->parse->jointree &&
3080  f->quals == NULL &&
3081  list_length(f->fromlist) == 1)
3082  return (Node *) linitial(f->fromlist);
3083  }
3084  else if (IsA(jtnode, JoinExpr))
3085  {
3086  JoinExpr *j = (JoinExpr *) jtnode;
3087  int varno;
3088 
3089  /* First, recurse */
3090  j->larg = remove_useless_results_recurse(root, j->larg);
3091  j->rarg = remove_useless_results_recurse(root, j->rarg);
3092 
3093  /* Apply join-type-specific optimization rules */
3094  switch (j->jointype)
3095  {
3096  case JOIN_INNER:
3097 
3098  /*
3099  * An inner join is equivalent to a FromExpr, so if either
3100  * side was simplified to an RTE_RESULT rel, we can replace
3101  * the join with a FromExpr with just the other side; and if
3102  * the qual is empty (JOIN ON TRUE) then we can omit the
3103  * FromExpr as well.
3104  *
3105  * Just as in the FromExpr case, we can't simplify if the
3106  * other input rel references any PHVs that are marked as to
3107  * be evaluated at the RTE_RESULT rel, because we can't
3108  * postpone their evaluation in that case. But we only have
3109  * to check this in cases where it's syntactically legal for
3110  * the other input to have a LATERAL reference to the
3111  * RTE_RESULT rel. Only RHSes of inner and left joins are
3112  * allowed to have such refs.
3113  */
3114  if ((varno = get_result_relid(root, j->larg)) != 0 &&
3115  !find_dependent_phvs_in_jointree(root, j->rarg, varno))
3116  {
3117  remove_result_refs(root, varno, j->rarg);
3118  if (j->quals)
3119  jtnode = (Node *)
3120  makeFromExpr(list_make1(j->rarg), j->quals);
3121  else
3122  jtnode = j->rarg;
3123  }
3124  else if ((varno = get_result_relid(root, j->rarg)) != 0)
3125  {
3126  remove_result_refs(root, varno, j->larg);
3127  if (j->quals)
3128  jtnode = (Node *)
3129  makeFromExpr(list_make1(j->larg), j->quals);
3130  else
3131  jtnode = j->larg;
3132  }
3133  break;
3134  case JOIN_LEFT:
3135 
3136  /*
3137  * We can simplify this case if the RHS is an RTE_RESULT, with
3138  * two different possibilities:
3139  *
3140  * If the qual is empty (JOIN ON TRUE), then the join can be
3141  * strength-reduced to a plain inner join, since each LHS row
3142  * necessarily has exactly one join partner. So we can always
3143  * discard the RHS, much as in the JOIN_INNER case above.
3144  * (Again, the LHS could not contain a lateral reference to
3145  * the RHS.)
3146  *
3147  * Otherwise, it's still true that each LHS row should be
3148  * returned exactly once, and since the RHS returns no columns
3149  * (unless there are PHVs that have to be evaluated there), we
3150  * don't much care if it's null-extended or not. So in this
3151  * case also, we can just ignore the qual and discard the left
3152  * join.
3153  */
3154  if ((varno = get_result_relid(root, j->rarg)) != 0 &&
3155  (j->quals == NULL ||
3156  !find_dependent_phvs(root, varno)))
3157  {
3158  remove_result_refs(root, varno, j->larg);
3159  jtnode = j->larg;
3160  }
3161  break;
3162  case JOIN_RIGHT:
3163  /* Mirror-image of the JOIN_LEFT case */
3164  if ((varno = get_result_relid(root, j->larg)) != 0 &&
3165  (j->quals == NULL ||
3166  !find_dependent_phvs(root, varno)))
3167  {
3168  remove_result_refs(root, varno, j->rarg);
3169  jtnode = j->rarg;
3170  }
3171  break;
3172  case JOIN_SEMI:
3173 
3174  /*
3175  * We may simplify this case if the RHS is an RTE_RESULT; the
3176  * join qual becomes effectively just a filter qual for the
3177  * LHS, since we should either return the LHS row or not. For
3178  * simplicity we inject the filter qual into a new FromExpr.
3179  *
3180  * Unlike the LEFT/RIGHT cases, we just Assert that there are
3181  * no PHVs that need to be evaluated at the semijoin's RHS,
3182  * since the rest of the query couldn't reference any outputs
3183  * of the semijoin's RHS.
3184  */
3185  if ((varno = get_result_relid(root, j->rarg)) != 0)
3186  {
3187  Assert(!find_dependent_phvs(root, varno));
3188  remove_result_refs(root, varno, j->larg);
3189  if (j->quals)
3190  jtnode = (Node *)
3191  makeFromExpr(list_make1(j->larg), j->quals);
3192  else
3193  jtnode = j->larg;
3194  }
3195  break;
3196  case JOIN_FULL:
3197  case JOIN_ANTI:
3198  /* We have no special smarts for these cases */
3199  break;
3200  default:
3201  elog(ERROR, "unrecognized join type: %d",
3202  (int) j->jointype);
3203  break;
3204  }
3205  }
3206  else
3207  elog(ERROR, "unrecognized node type: %d",
3208  (int) nodeTag(jtnode));
3209  return jtnode;
3210 }
3211 
3212 /*
3213  * get_result_relid
3214  * If jtnode is a RangeTblRef for an RTE_RESULT RTE, return its relid;
3215  * otherwise return 0.
3216  */
3217 static int
3218 get_result_relid(PlannerInfo *root, Node *jtnode)
3219 {
3220  int varno;
3221 
3222  if (!IsA(jtnode, RangeTblRef))
3223  return 0;
3224  varno = ((RangeTblRef *) jtnode)->rtindex;
3225  if (rt_fetch(varno, root->parse->rtable)->rtekind != RTE_RESULT)
3226  return 0;
3227  return varno;
3228 }
3229 
3230 /*
3231  * remove_result_refs
3232  * Helper routine for dropping an unneeded RTE_RESULT RTE.
3233  *
3234  * This doesn't physically remove the RTE from the jointree, because that's
3235  * more easily handled in remove_useless_results_recurse. What it does do
3236  * is the necessary cleanup in the rest of the tree: we must adjust any PHVs
3237  * that may reference the RTE. Be sure to call this at a point where the
3238  * jointree is valid (no disconnected nodes).
3239  *
3240  * Note that we don't need to process the append_rel_list, since RTEs
3241  * referenced directly in the jointree won't be appendrel members.
3242  *
3243  * varno is the RTE_RESULT's relid.
3244  * newjtloc is the jointree location at which any PHVs referencing the
3245  * RTE_RESULT should be evaluated instead.
3246  */
3247 static void
3248 remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc)
3249 {
3250  /* Fix up PlaceHolderVars as needed */
3251  /* If there are no PHVs anywhere, we can skip this bit */
3252  if (root->glob->lastPHId != 0)
3253  {
3254  Relids subrelids;
3255 
3256  subrelids = get_relids_in_jointree(newjtloc, false);
3257  Assert(!bms_is_empty(subrelids));
3258  substitute_phv_relids((Node *) root->parse, varno, subrelids);
3259  }
3260 
3261  /*
3262  * We also need to remove any PlanRowMark referencing the RTE, but we
3263  * postpone that work until we return to remove_useless_result_rtes.
3264  */
3265 }
3266 
3267 
3268 /*
3269  * find_dependent_phvs - are there any PlaceHolderVars whose relids are
3270  * exactly the given varno?
3271  *
3272  * find_dependent_phvs should be used when we want to see if there are
3273  * any such PHVs anywhere in the Query. Another use-case is to see if
3274  * a subtree of the join tree contains such PHVs; but for that, we have
3275  * to look not only at the join tree nodes themselves but at the
3276  * referenced RTEs. For that, use find_dependent_phvs_in_jointree.
3277  */
3278 
3279 typedef struct
3280 {
3281  Relids relids;
3282  int sublevels_up;
3283 } find_dependent_phvs_context;
3284 
3285 static bool
3286 find_dependent_phvs_walker(Node *node,
3287  find_dependent_phvs_context *context)
3288 {
3289  if (node == NULL)
3290  return false;
3291  if (IsA(node, PlaceHolderVar))
3292  {
3293  PlaceHolderVar *phv = (PlaceHolderVar *) node;
3294 
3295  if (phv->phlevelsup == context->sublevels_up &&
3296  bms_equal(context->relids, phv->phrels))
3297  return true;
3298  /* fall through to examine children */
3299  }
3300  if (IsA(node, Query))
3301  {
3302  /* Recurse into subselects */
3303  bool result;
3304 
3305  context->sublevels_up++;
3306  result = query_tree_walker((Query *) node,
3307  find_dependent_phvs_walker,
3308  (void *) context, 0);
3309  context->sublevels_up--;
3310  return result;
3311  }
3312  /* Shouldn't need to handle planner auxiliary nodes here */
3313  Assert(!IsA(node, SpecialJoinInfo));
3314  Assert(!IsA(node, AppendRelInfo));
3315  Assert(!IsA(node, PlaceHolderInfo));
3316  Assert(!IsA(node, MinMaxAggInfo));
3317 
3318  return expression_tree_walker(node, find_dependent_phvs_walker,
3319  (void *) context);
3320 }
3321 
3322 static bool
3323 find_dependent_phvs(PlannerInfo *root, int varno)
3324 {
3325  find_dependent_phvs_context context;
3326 
3327  /* If there are no PHVs anywhere, we needn't work hard */
3328  if (root->glob->lastPHId == 0)
3329  return false;
3330 
3331  context.relids = bms_make_singleton(varno);
3332  context.sublevels_up = 0;
3333 
3334  return query_tree_walker(root->parse,
3335  find_dependent_phvs_walker,
3336  (void *) &context,
3337  0);
3338 }
3339 
3340 static bool
3341 find_dependent_phvs_in_jointree(PlannerInfo *root, Node *node, int varno)
3342 {
3343  find_dependent_phvs_context context;
3344  Relids subrelids;
3345  int relid;
3346 
3347  /* If there are no PHVs anywhere, we needn't work hard */
3348  if (root->glob->lastPHId == 0)
3349  return false;
3350 
3351  context.relids = bms_make_singleton(varno);
3352  context.sublevels_up = 0;
3353 
3354  /*
3355  * See if the jointree fragment itself contains references (in join quals)
3356  */
3357  if (find_dependent_phvs_walker(node, &context))
3358  return true;
3359 
3360  /*
3361  * Otherwise, identify the set of referenced RTEs (we can ignore joins,
3362  * since they should be flattened already, so their join alias lists no
3363  * longer matter), and tediously check each RTE. We can ignore RTEs that
3364  * are not marked LATERAL, though, since they couldn't possibly contain
3365  * any cross-references to other RTEs.
3366  */
3367  subrelids = get_relids_in_jointree(node, false);
3368  relid = -1;
3369  while ((relid = bms_next_member(subrelids, relid)) >= 0)
3370  {
3371  RangeTblEntry *rte = rt_fetch(relid, root->parse->rtable);
3372 
3373  if (rte->lateral &&
3374  range_table_entry_walker(rte,
3375  find_dependent_phvs_walker,
3376  (void *) &context,
3377  0))
3378  return true;
3379  }
3380 
3381  return false;
3382 }
3383 
3384 /*
3385  * substitute_phv_relids - adjust PlaceHolderVar relid sets after pulling up
3386  * a subquery or removing an RTE_RESULT jointree item
3387  *
3388  * Find any PlaceHolderVar nodes in the given tree that reference the
3389  * pulled-up relid, and change them to reference the replacement relid(s).
3390  *
3391  * NOTE: although this has the form of a walker, we cheat and modify the
3392  * nodes in-place. This should be OK since the tree was copied by
3393  * pullup_replace_vars earlier. Avoid scribbling on the original values of
3394  * the bitmapsets, though, because expression_tree_mutator doesn't copy those.
3395  */
3396 
3397 typedef struct
3398 {
3399  int varno;
3400  int sublevels_up;
3401  Relids subrelids;
3402 } substitute_phv_relids_context;
3403 
3404 static bool
3405 substitute_phv_relids_walker(Node *node,
3406  substitute_phv_relids_context *context)
3407 {
3408  if (node == NULL)
3409  return false;
3410  if (IsA(node, PlaceHolderVar))
3411  {
3412  PlaceHolderVar *phv = (PlaceHolderVar *) node;
3413 
3414  if (phv->phlevelsup == context->sublevels_up &&
3415  bms_is_member(context->varno, phv->phrels))
3416  {
3417  phv->phrels = bms_union(phv->phrels,
3418  context->subrelids);
3419  phv->phrels = bms_del_member(phv->phrels,
3420  context->varno);
3421  /* Assert we haven't broken the PHV */
3422  Assert(!bms_is_empty(phv->phrels));
3423  }
3424  /* fall through to examine children */
3425  }
3426  if (IsA(node, Query))
3427  {
3428  /* Recurse into subselects */
3429  bool result;
3430 
3431  context->sublevels_up++;
3432  result = query_tree_walker((Query *) node,
3433  substitute_phv_relids_walker,
3434  (void *) context, 0);
3435  context->sublevels_up--;
3436  return result;
3437  }
3438  /* Shouldn't need to handle planner auxiliary nodes here */
3439  Assert(!IsA(node, SpecialJoinInfo));
3440  Assert(!IsA(node, AppendRelInfo));
3441  Assert(!IsA(node, PlaceHolderInfo));
3442  Assert(!IsA(node, MinMaxAggInfo));
3443 
3444  return expression_tree_walker(node, substitute_phv_relids_walker,
3445  (void *) context);
3446 }
3447 
3448 static void
3449 substitute_phv_relids(Node *node, int varno, Relids subrelids)
3450 {
3451  substitute_phv_relids_context context;
3452 
3453  context.varno = varno;
3454  context.sublevels_up = 0;
3455  context.subrelids = subrelids;
3456 
3457  /*
3458  * Must be prepared to start with a Query or a bare expression tree.
3459  */
3460  query_or_expression_tree_walker(node,
3461  substitute_phv_relids_walker,
3462  (void *) &context,
3463  0);
3464 }
3465 
3466 /*
3467  * fix_append_rel_relids: update RT-index fields of AppendRelInfo nodes
3468  *
3469  * When we pull up a subquery, any AppendRelInfo references to the subquery's
3470  * RT index have to be replaced by the substituted relid (and there had better
3471  * be only one). We also need to apply substitute_phv_relids to their
3472  * translated_vars lists, since those might contain PlaceHolderVars.
3473  *
3474  * We assume we may modify the AppendRelInfo nodes in-place.
3475  */
3476 static void
3477 fix_append_rel_relids(List *append_rel_list, int varno, Relids subrelids)
3478 {
3479  ListCell *l;
3480  int subvarno = -1;
3481 
3482  /*
3483  * We only want to extract the member relid once, but we mustn't fail
3484  * immediately if there are multiple members; it could be that none of the
3485  * AppendRelInfo nodes refer to it. So compute it on first use. Note that
3486  * bms_singleton_member will complain if set is not singleton.
3487  */
3488  foreach(l, append_rel_list)
3489  {
3490  AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
3491 
3492  /* The parent_relid shouldn't ever be a pullup target */
3493  Assert(appinfo->parent_relid != varno);
3494 
3495  if (appinfo->child_relid == varno)
3496  {
3497  if (subvarno < 0)
3498  subvarno = bms_singleton_member(subrelids);
3499  appinfo->child_relid = subvarno;
3500  }
3501 
3502  /* Also fix up any PHVs in its translated vars */
3503  substitute_phv_relids((Node *) appinfo->translated_vars,
3504  varno, subrelids);
3505  }
3506 }
3507 
3508 /*
3509  * get_relids_in_jointree: get set of RT indexes present in a jointree
3510  *
3511  * If include_joins is true, join RT indexes are included; if false,
3512  * only base rels are included.
3513  */
3514 Relids
3515 get_relids_in_jointree(Node *jtnode, bool include_joins)
3516 {
3517  Relids result = NULL;
3518 
3519  if (jtnode == NULL)
3520  return result;
3521  if (IsA(jtnode, RangeTblRef))
3522  {
3523  int varno = ((RangeTblRef *) jtnode)->rtindex;
3524 
3525  result = bms_make_singleton(varno);
3526  }
3527  else if (IsA(jtnode, FromExpr))
3528  {
3529  FromExpr *f = (FromExpr *) jtnode;
3530  ListCell *l;
3531 
3532  foreach(l, f->fromlist)
3533  {
3534  result = bms_join(result,
3535  get_relids_in_jointree(lfirst(l),
3536  include_joins));
3537  }
3538  }
3539  else if (IsA(jtnode, JoinExpr))
3540  {
3541  JoinExpr *j = (JoinExpr *) jtnode;
3542 
3543  result = get_relids_in_jointree(j->larg, include_joins);
3544  result = bms_join(result,
3545  get_relids_in_jointree(j->rarg, include_joins));
3546  if (include_joins && j->rtindex)
3547  result = bms_add_member(result, j->rtindex);
3548  }
3549  else
3550  elog(ERROR, "unrecognized node type: %d",
3551  (int) nodeTag(jtnode));
3552  return result;
3553 }
3554 
3555 /*
3556  * get_relids_for_join: get set of base RT indexes making up a join
3557  */
3558 Relids
3559 get_relids_for_join(Query *query, int joinrelid)
3560 {
3561  Node *jtnode;
3562 
3563  jtnode = find_jointree_node_for_rel((Node *) query->jointree,
3564  joinrelid);
3565  if (!jtnode)
3566  elog(ERROR, "could not find join node %d", joinrelid);
3567  return get_relids_in_jointree(jtnode, false);
3568 }
3569 
3570 /*
3571  * find_jointree_node_for_rel: locate jointree node for a base or join RT index
3572  *
3573  * Returns NULL if not found
3574  */
3575 static Node *
3576 find_jointree_node_for_rel(Node *jtnode, int relid)
3577 {
3578  if (jtnode == NULL)
3579  return NULL;
3580  if (IsA(jtnode, RangeTblRef))
3581  {
3582  int varno = ((RangeTblRef *) jtnode)->rtindex;
3583 
3584  if (relid == varno)
3585  return jtnode;
3586  }
3587  else if (IsA(jtnode, FromExpr))
3588  {
3589  FromExpr *f = (FromExpr *) jtnode;
3590  ListCell *l;
3591 
3592  foreach(l, f->fromlist)
3593  {
3594  jtnode = find_jointree_node_for_rel(lfirst(l), relid);
3595  if (jtnode)
3596  return jtnode;
3597  }
3598  }
3599  else if (IsA(jtnode, JoinExpr))
3600  {
3601  JoinExpr *j = (JoinExpr *) jtnode;
3602 
3603  if (relid == j->rtindex)
3604  return jtnode;
3605  jtnode = find_jointree_node_for_rel(j->larg, relid);
3606  if (jtnode)
3607  return jtnode;
3608  jtnode = find_jointree_node_for_rel(j->rarg, relid);
3609  if (jtnode)
3610  return jtnode;
3611  }
3612  else
3613  elog(ERROR, "unrecognized node type: %d",
3614  (int) nodeTag(jtnode));
3615  return NULL;
3616 }
Query::limitOffset
Node * limitOffset
Definition: parsenodes.h:160
NIL
#define NIL
Definition: pg_list.h:65
substitute_phv_relids
static void substitute_phv_relids(Node *node, int varno, Relids subrelids)
Definition: prepjointree.c:3449
PlannerInfo::rowMarks
List * rowMarks
Definition: pathnodes.h:292
pull_up_sublinks_qual_recurse
static Node * pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node, Node **jtlink1, Relids available_rels1, Node **jtlink2, Relids available_rels2)
Definition: prepjointree.c:387
remove_useless_result_rtes
void remove_useless_result_rtes(PlannerInfo *root)
Definition: prepjointree.c:2974
pull_up_union_leaf_queries
static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex, Query *setOpQuery, int childRToffset)
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