1 /*-------------------------------------------------------------------------
2 *
3 * var.c
4 * Var node manipulation routines
5 *
6 * Note: for most purposes, PlaceHolderVar is considered a Var too,
7 * even if its contained expression is variable-free. Also, CurrentOfExpr
8 * is treated as a Var for purposes of determining whether an expression
9 * contains variables.
10 *
11 *
12 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
13 * Portions Copyright (c) 1994, Regents of the University of California
14 *
15 *
16 * IDENTIFICATION
17 * src/backend/optimizer/util/var.c
18 *
19 *-------------------------------------------------------------------------
20 */
21 #include "postgres.h"
22
23 #include "access/sysattr.h"
24 #include "nodes/nodeFuncs.h"
25 #include "optimizer/optimizer.h"
26 #include "optimizer/placeholder.h"
27 #include "optimizer/prep.h"
28 #include "parser/parsetree.h"
29 #include "rewrite/rewriteManip.h"
30
31
32 typedef struct
33 {
34 Relids varnos;
35 PlannerInfo *root;
36 int sublevels_up;
37 } pull_varnos_context;
38
39 typedef struct
40 {
41 Bitmapset *varattnos;
42 Index varno;
43 } pull_varattnos_context;
44
45 typedef struct
46 {
47 List *vars;
48 int sublevels_up;
49 } pull_vars_context;
50
51 typedef struct
52 {
53 int var_location;
54 int sublevels_up;
55 } locate_var_of_level_context;
56
57 typedef struct
58 {
59 List *varlist;
60 int flags;
61 } pull_var_clause_context;
62
63 typedef struct
64 {
65 Query *query; /* outer Query */
66 int sublevels_up;
67 bool possible_sublink; /* could aliases include a SubLink? */
68 bool inserted_sublink; /* have we inserted a SubLink? */
69 } flatten_join_alias_vars_context;
70
71 static bool pull_varnos_walker(Node *node,
72 pull_varnos_context *context);
73 static bool pull_varattnos_walker(Node *node, pull_varattnos_context *context);
74 static bool pull_vars_walker(Node *node, pull_vars_context *context);
75 static bool contain_var_clause_walker(Node *node, void *context);
76 static bool contain_vars_of_level_walker(Node *node, int *sublevels_up);
77 static bool locate_var_of_level_walker(Node *node,
78 locate_var_of_level_context *context);
79 static bool pull_var_clause_walker(Node *node,
80 pull_var_clause_context *context);
81 static Node *flatten_join_alias_vars_mutator(Node *node,
82 flatten_join_alias_vars_context *context);
83 static Relids alias_relid_set(Query *query, Relids relids);
84
85
86 /*
87 * pull_varnos
88 * Create a set of all the distinct varnos present in a parsetree.
89 * Only varnos that reference level-zero rtable entries are considered.
90 *
91 * NOTE: this is used on not-yet-planned expressions. It may therefore find
92 * bare SubLinks, and if so it needs to recurse into them to look for uplevel
93 * references to the desired rtable level! But when we find a completed
94 * SubPlan, we only need to look at the parameters passed to the subplan.
95 */
96 Relids
pull_varnos(PlannerInfo * root,Node * node)97 pull_varnos(PlannerInfo *root, Node *node)
98 {
99 pull_varnos_context context;
100
101 context.varnos = NULL;
102 context.root = root;
103 context.sublevels_up = 0;
104
105 /*
106 * Must be prepared to start with a Query or a bare expression tree; if
107 * it's a Query, we don't want to increment sublevels_up.
108 */
109 query_or_expression_tree_walker(node,
110 pull_varnos_walker,
111 (void *) &context,
112 0);
113
114 return context.varnos;
115 }
116
117 /*
118 * pull_varnos_of_level
119 * Create a set of all the distinct varnos present in a parsetree.
120 * Only Vars of the specified level are considered.
121 */
122 Relids
pull_varnos_of_level(PlannerInfo * root,Node * node,int levelsup)123 pull_varnos_of_level(PlannerInfo *root, Node *node, int levelsup)
124 {
125 pull_varnos_context context;
126
127 context.varnos = NULL;
128 context.root = root;
129 context.sublevels_up = levelsup;
130
131 /*
132 * Must be prepared to start with a Query or a bare expression tree; if
133 * it's a Query, we don't want to increment sublevels_up.
134 */
135 query_or_expression_tree_walker(node,
136 pull_varnos_walker,
137 (void *) &context,
138 0);
139
140 return context.varnos;
141 }
142
143 static bool
pull_varnos_walker(Node * node,pull_varnos_context * context)144 pull_varnos_walker(Node *node, pull_varnos_context *context)
145 {
146 if (node == NULL)
147 return false;
148 if (IsA(node, Var))
149 {
150 Var *var = (Var *) node;
151
152 if (var->varlevelsup == context->sublevels_up)
153 context->varnos = bms_add_member(context->varnos, var->varno);
154 return false;
155 }
156 if (IsA(node, CurrentOfExpr))
157 {
158 CurrentOfExpr *cexpr = (CurrentOfExpr *) node;
159
160 if (context->sublevels_up == 0)
161 context->varnos = bms_add_member(context->varnos, cexpr->cvarno);
162 return false;
163 }
164 if (IsA(node, PlaceHolderVar))
165 {
166 PlaceHolderVar *phv = (PlaceHolderVar *) node;
167
168 /*
169 * If a PlaceHolderVar is not of the target query level, ignore it,
170 * instead recursing into its expression to see if it contains any
171 * vars that are of the target level.
172 */
173 if (phv->phlevelsup == context->sublevels_up)
174 {
175 /*
176 * Ideally, the PHV's contribution to context->varnos is its
177 * ph_eval_at set. However, this code can be invoked before
178 * that's been computed. If we cannot find a PlaceHolderInfo,
179 * fall back to the conservative assumption that the PHV will be
180 * evaluated at its syntactic level (phv->phrels).
181 *
182 * There is a second hazard: this code is also used to examine
183 * qual clauses during deconstruct_jointree, when we may have a
184 * PlaceHolderInfo but its ph_eval_at value is not yet final, so
185 * that theoretically we could obtain a relid set that's smaller
186 * than we'd see later on. That should never happen though,
187 * because we deconstruct the jointree working upwards. Any outer
188 * join that forces delay of evaluation of a given qual clause
189 * will be processed before we examine that clause here, so the
190 * ph_eval_at value should have been updated to include it.
191 *
192 * Another problem is that a PlaceHolderVar can appear in quals or
193 * tlists that have been translated for use in a child appendrel.
194 * Typically such a PHV is a parameter expression sourced by some
195 * other relation, so that the translation from parent appendrel
196 * to child doesn't change its phrels, and we should still take
197 * ph_eval_at at face value. But in corner cases, the PHV's
198 * original phrels can include the parent appendrel itself, in
199 * which case the translated PHV will have the child appendrel in
200 * phrels, and we must translate ph_eval_at to match.
201 */
202 PlaceHolderInfo *phinfo = NULL;
203
204 if (phv->phlevelsup == 0)
205 {
206 ListCell *lc;
207
208 foreach(lc, context->root->placeholder_list)
209 {
210 phinfo = (PlaceHolderInfo *) lfirst(lc);
211 if (phinfo->phid == phv->phid)
212 break;
213 phinfo = NULL;
214 }
215 }
216 if (phinfo == NULL)
217 {
218 /* No PlaceHolderInfo yet, use phrels */
219 context->varnos = bms_add_members(context->varnos,
220 phv->phrels);
221 }
222 else if (bms_equal(phv->phrels, phinfo->ph_var->phrels))
223 {
224 /* Normal case: use ph_eval_at */
225 context->varnos = bms_add_members(context->varnos,
226 phinfo->ph_eval_at);
227 }
228 else
229 {
230 /* Translated PlaceHolderVar: translate ph_eval_at to match */
231 Relids newevalat,
232 delta;
233
234 /* remove what was removed from phv->phrels ... */
235 delta = bms_difference(phinfo->ph_var->phrels, phv->phrels);
236 newevalat = bms_difference(phinfo->ph_eval_at, delta);
237 /* ... then if that was in fact part of ph_eval_at ... */
238 if (!bms_equal(newevalat, phinfo->ph_eval_at))
239 {
240 /* ... add what was added */
241 delta = bms_difference(phv->phrels, phinfo->ph_var->phrels);
242 newevalat = bms_join(newevalat, delta);
243 }
244 context->varnos = bms_join(context->varnos,
245 newevalat);
246 }
247 return false; /* don't recurse into expression */
248 }
249 }
250 else if (IsA(node, Query))
251 {
252 /* Recurse into RTE subquery or not-yet-planned sublink subquery */
253 bool result;
254
255 context->sublevels_up++;
256 result = query_tree_walker((Query *) node, pull_varnos_walker,
257 (void *) context, 0);
258 context->sublevels_up--;
259 return result;
260 }
261 return expression_tree_walker(node, pull_varnos_walker,
262 (void *) context);
263 }
264
265
266 /*
267 * pull_varattnos
268 * Find all the distinct attribute numbers present in an expression tree,
269 * and add them to the initial contents of *varattnos.
270 * Only Vars of the given varno and rtable level zero are considered.
271 *
272 * Attribute numbers are offset by FirstLowInvalidHeapAttributeNumber so that
273 * we can include system attributes (e.g., OID) in the bitmap representation.
274 *
275 * Currently, this does not support unplanned subqueries; that is not needed
276 * for current uses. It will handle already-planned SubPlan nodes, though,
277 * looking into only the "testexpr" and the "args" list. (The subplan cannot
278 * contain any other references to Vars of the current level.)
279 */
280 void
pull_varattnos(Node * node,Index varno,Bitmapset ** varattnos)281 pull_varattnos(Node *node, Index varno, Bitmapset **varattnos)
282 {
283 pull_varattnos_context context;
284
285 context.varattnos = *varattnos;
286 context.varno = varno;
287
288 (void) pull_varattnos_walker(node, &context);
289
290 *varattnos = context.varattnos;
291 }
292
293 static bool
pull_varattnos_walker(Node * node,pull_varattnos_context * context)294 pull_varattnos_walker(Node *node, pull_varattnos_context *context)
295 {
296 if (node == NULL)
297 return false;
298 if (IsA(node, Var))
299 {
300 Var *var = (Var *) node;
301
302 if (var->varno == context->varno && var->varlevelsup == 0)
303 context->varattnos =
304 bms_add_member(context->varattnos,
305 var->varattno - FirstLowInvalidHeapAttributeNumber);
306 return false;
307 }
308
309 /* Should not find an unplanned subquery */
310 Assert(!IsA(node, Query));
311
312 return expression_tree_walker(node, pull_varattnos_walker,
313 (void *) context);
314 }
315
316
317 /*
318 * pull_vars_of_level
319 * Create a list of all Vars (and PlaceHolderVars) referencing the
320 * specified query level in the given parsetree.
321 *
322 * Caution: the Vars are not copied, only linked into the list.
323 */
324 List *
pull_vars_of_level(Node * node,int levelsup)325 pull_vars_of_level(Node *node, int levelsup)
326 {
327 pull_vars_context context;
328
329 context.vars = NIL;
330 context.sublevels_up = levelsup;
331
332 /*
333 * Must be prepared to start with a Query or a bare expression tree; if
334 * it's a Query, we don't want to increment sublevels_up.
335 */
336 query_or_expression_tree_walker(node,
337 pull_vars_walker,
338 (void *) &context,
339 0);
340
341 return context.vars;
342 }
343
344 static bool
pull_vars_walker(Node * node,pull_vars_context * context)345 pull_vars_walker(Node *node, pull_vars_context *context)
346 {
347 if (node == NULL)
348 return false;
349 if (IsA(node, Var))
350 {
351 Var *var = (Var *) node;
352
353 if (var->varlevelsup == context->sublevels_up)
354 context->vars = lappend(context->vars, var);
355 return false;
356 }
357 if (IsA(node, PlaceHolderVar))
358 {
359 PlaceHolderVar *phv = (PlaceHolderVar *) node;
360
361 if (phv->phlevelsup == context->sublevels_up)
362 context->vars = lappend(context->vars, phv);
363 /* we don't want to look into the contained expression */
364 return false;
365 }
366 if (IsA(node, Query))
367 {
368 /* Recurse into RTE subquery or not-yet-planned sublink subquery */
369 bool result;
370
371 context->sublevels_up++;
372 result = query_tree_walker((Query *) node, pull_vars_walker,
373 (void *) context, 0);
374 context->sublevels_up--;
375 return result;
376 }
377 return expression_tree_walker(node, pull_vars_walker,
378 (void *) context);
379 }
380
381
382 /*
383 * contain_var_clause
384 * Recursively scan a clause to discover whether it contains any Var nodes
385 * (of the current query level).
386 *
387 * Returns true if any varnode found.
388 *
389 * Does not examine subqueries, therefore must only be used after reduction
390 * of sublinks to subplans!
391 */
392 bool
contain_var_clause(Node * node)393 contain_var_clause(Node *node)
394 {
395 return contain_var_clause_walker(node, NULL);
396 }
397
398 static bool
contain_var_clause_walker(Node * node,void * context)399 contain_var_clause_walker(Node *node, void *context)
400 {
401 if (node == NULL)
402 return false;
403 if (IsA(node, Var))
404 {
405 if (((Var *) node)->varlevelsup == 0)
406 return true; /* abort the tree traversal and return true */
407 return false;
408 }
409 if (IsA(node, CurrentOfExpr))
410 return true;
411 if (IsA(node, PlaceHolderVar))
412 {
413 if (((PlaceHolderVar *) node)->phlevelsup == 0)
414 return true; /* abort the tree traversal and return true */
415 /* else fall through to check the contained expr */
416 }
417 return expression_tree_walker(node, contain_var_clause_walker, context);
418 }
419
420
421 /*
422 * contain_vars_of_level
423 * Recursively scan a clause to discover whether it contains any Var nodes
424 * of the specified query level.
425 *
426 * Returns true if any such Var found.
427 *
428 * Will recurse into sublinks. Also, may be invoked directly on a Query.
429 */
430 bool
contain_vars_of_level(Node * node,int levelsup)431 contain_vars_of_level(Node *node, int levelsup)
432 {
433 int sublevels_up = levelsup;
434
435 return query_or_expression_tree_walker(node,
436 contain_vars_of_level_walker,
437 (void *) &sublevels_up,
438 0);
439 }
440
441 static bool
contain_vars_of_level_walker(Node * node,int * sublevels_up)442 contain_vars_of_level_walker(Node *node, int *sublevels_up)
443 {
444 if (node == NULL)
445 return false;
446 if (IsA(node, Var))
447 {
448 if (((Var *) node)->varlevelsup == *sublevels_up)
449 return true; /* abort tree traversal and return true */
450 return false;
451 }
452 if (IsA(node, CurrentOfExpr))
453 {
454 if (*sublevels_up == 0)
455 return true;
456 return false;
457 }
458 if (IsA(node, PlaceHolderVar))
459 {
460 if (((PlaceHolderVar *) node)->phlevelsup == *sublevels_up)
461 return true; /* abort the tree traversal and return true */
462 /* else fall through to check the contained expr */
463 }
464 if (IsA(node, Query))
465 {
466 /* Recurse into subselects */
467 bool result;
468
469 (*sublevels_up)++;
470 result = query_tree_walker((Query *) node,
471 contain_vars_of_level_walker,
472 (void *) sublevels_up,
473 0);
474 (*sublevels_up)--;
475 return result;
476 }
477 return expression_tree_walker(node,
478 contain_vars_of_level_walker,
479 (void *) sublevels_up);
480 }
481
482
483 /*
484 * locate_var_of_level
485 * Find the parse location of any Var of the specified query level.
486 *
487 * Returns -1 if no such Var is in the querytree, or if they all have
488 * unknown parse location. (The former case is probably caller error,
489 * but we don't bother to distinguish it from the latter case.)
490 *
491 * Will recurse into sublinks. Also, may be invoked directly on a Query.
492 *
493 * Note: it might seem appropriate to merge this functionality into
494 * contain_vars_of_level, but that would complicate that function's API.
495 * Currently, the only uses of this function are for error reporting,
496 * and so shaving cycles probably isn't very important.
497 */
498 int
locate_var_of_level(Node * node,int levelsup)499 locate_var_of_level(Node *node, int levelsup)
500 {
501 locate_var_of_level_context context;
502
503 context.var_location = -1; /* in case we find nothing */
504 context.sublevels_up = levelsup;
505
506 (void) query_or_expression_tree_walker(node,
507 locate_var_of_level_walker,
508 (void *) &context,
509 0);
510
511 return context.var_location;
512 }
513
514 static bool
locate_var_of_level_walker(Node * node,locate_var_of_level_context * context)515 locate_var_of_level_walker(Node *node,
516 locate_var_of_level_context *context)
517 {
518 if (node == NULL)
519 return false;
520 if (IsA(node, Var))
521 {
522 Var *var = (Var *) node;
523
524 if (var->varlevelsup == context->sublevels_up &&
525 var->location >= 0)
526 {
527 context->var_location = var->location;
528 return true; /* abort tree traversal and return true */
529 }
530 return false;
531 }
532 if (IsA(node, CurrentOfExpr))
533 {
534 /* since CurrentOfExpr doesn't carry location, nothing we can do */
535 return false;
536 }
537 /* No extra code needed for PlaceHolderVar; just look in contained expr */
538 if (IsA(node, Query))
539 {
540 /* Recurse into subselects */
541 bool result;
542
543 context->sublevels_up++;
544 result = query_tree_walker((Query *) node,
545 locate_var_of_level_walker,
546 (void *) context,
547 0);
548 context->sublevels_up--;
549 return result;
550 }
551 return expression_tree_walker(node,
552 locate_var_of_level_walker,
553 (void *) context);
554 }
555
556
557 /*
558 * pull_var_clause
559 * Recursively pulls all Var nodes from an expression clause.
560 *
561 * Aggrefs are handled according to these bits in 'flags':
562 * PVC_INCLUDE_AGGREGATES include Aggrefs in output list
563 * PVC_RECURSE_AGGREGATES recurse into Aggref arguments
564 * neither flag throw error if Aggref found
565 * Vars within an Aggref's expression are included in the result only
566 * when PVC_RECURSE_AGGREGATES is specified.
567 *
568 * WindowFuncs are handled according to these bits in 'flags':
569 * PVC_INCLUDE_WINDOWFUNCS include WindowFuncs in output list
570 * PVC_RECURSE_WINDOWFUNCS recurse into WindowFunc arguments
571 * neither flag throw error if WindowFunc found
572 * Vars within a WindowFunc's expression are included in the result only
573 * when PVC_RECURSE_WINDOWFUNCS is specified.
574 *
575 * PlaceHolderVars are handled according to these bits in 'flags':
576 * PVC_INCLUDE_PLACEHOLDERS include PlaceHolderVars in output list
577 * PVC_RECURSE_PLACEHOLDERS recurse into PlaceHolderVar arguments
578 * neither flag throw error if PlaceHolderVar found
579 * Vars within a PHV's expression are included in the result only
580 * when PVC_RECURSE_PLACEHOLDERS is specified.
581 *
582 * GroupingFuncs are treated mostly like Aggrefs, and so do not need
583 * their own flag bits.
584 *
585 * CurrentOfExpr nodes are ignored in all cases.
586 *
587 * Upper-level vars (with varlevelsup > 0) should not be seen here,
588 * likewise for upper-level Aggrefs and PlaceHolderVars.
589 *
590 * Returns list of nodes found. Note the nodes themselves are not
591 * copied, only referenced.
592 *
593 * Does not examine subqueries, therefore must only be used after reduction
594 * of sublinks to subplans!
595 */
596 List *
pull_var_clause(Node * node,int flags)597 pull_var_clause(Node *node, int flags)
598 {
599 pull_var_clause_context context;
600
601 /* Assert that caller has not specified inconsistent flags */
602 Assert((flags & (PVC_INCLUDE_AGGREGATES | PVC_RECURSE_AGGREGATES))
603 != (PVC_INCLUDE_AGGREGATES | PVC_RECURSE_AGGREGATES));
604 Assert((flags & (PVC_INCLUDE_WINDOWFUNCS | PVC_RECURSE_WINDOWFUNCS))
605 != (PVC_INCLUDE_WINDOWFUNCS | PVC_RECURSE_WINDOWFUNCS));
606 Assert((flags & (PVC_INCLUDE_PLACEHOLDERS | PVC_RECURSE_PLACEHOLDERS))
607 != (PVC_INCLUDE_PLACEHOLDERS | PVC_RECURSE_PLACEHOLDERS));
608
609 context.varlist = NIL;
610 context.flags = flags;
611
612 pull_var_clause_walker(node, &context);
613 return context.varlist;
614 }
615
616 static bool
pull_var_clause_walker(Node * node,pull_var_clause_context * context)617 pull_var_clause_walker(Node *node, pull_var_clause_context *context)
618 {
619 if (node == NULL)
620 return false;
621 if (IsA(node, Var))
622 {
623 if (((Var *) node)->varlevelsup != 0)
624 elog(ERROR, "Upper-level Var found where not expected");
625 context->varlist = lappend(context->varlist, node);
626 return false;
627 }
628 else if (IsA(node, Aggref))
629 {
630 if (((Aggref *) node)->agglevelsup != 0)
631 elog(ERROR, "Upper-level Aggref found where not expected");
632 if (context->flags & PVC_INCLUDE_AGGREGATES)
633 {
634 context->varlist = lappend(context->varlist, node);
635 /* we do NOT descend into the contained expression */
636 return false;
637 }
638 else if (context->flags & PVC_RECURSE_AGGREGATES)
639 {
640 /* fall through to recurse into the aggregate's arguments */
641 }
642 else
643 elog(ERROR, "Aggref found where not expected");
644 }
645 else if (IsA(node, GroupingFunc))
646 {
647 if (((GroupingFunc *) node)->agglevelsup != 0)
648 elog(ERROR, "Upper-level GROUPING found where not expected");
649 if (context->flags & PVC_INCLUDE_AGGREGATES)
650 {
651 context->varlist = lappend(context->varlist, node);
652 /* we do NOT descend into the contained expression */
653 return false;
654 }
655 else if (context->flags & PVC_RECURSE_AGGREGATES)
656 {
657 /*
658 * We do NOT descend into the contained expression, even if the
659 * caller asked for it, because we never actually evaluate it -
660 * the result is driven entirely off the associated GROUP BY
661 * clause, so we never need to extract the actual Vars here.
662 */
663 return false;
664 }
665 else
666 elog(ERROR, "GROUPING found where not expected");
667 }
668 else if (IsA(node, WindowFunc))
669 {
670 /* WindowFuncs have no levelsup field to check ... */
671 if (context->flags & PVC_INCLUDE_WINDOWFUNCS)
672 {
673 context->varlist = lappend(context->varlist, node);
674 /* we do NOT descend into the contained expressions */
675 return false;
676 }
677 else if (context->flags & PVC_RECURSE_WINDOWFUNCS)
678 {
679 /* fall through to recurse into the windowfunc's arguments */
680 }
681 else
682 elog(ERROR, "WindowFunc found where not expected");
683 }
684 else if (IsA(node, PlaceHolderVar))
685 {
686 if (((PlaceHolderVar *) node)->phlevelsup != 0)
687 elog(ERROR, "Upper-level PlaceHolderVar found where not expected");
688 if (context->flags & PVC_INCLUDE_PLACEHOLDERS)
689 {
690 context->varlist = lappend(context->varlist, node);
691 /* we do NOT descend into the contained expression */
692 return false;
693 }
694 else if (context->flags & PVC_RECURSE_PLACEHOLDERS)
695 {
696 /* fall through to recurse into the placeholder's expression */
697 }
698 else
699 elog(ERROR, "PlaceHolderVar found where not expected");
700 }
701 return expression_tree_walker(node, pull_var_clause_walker,
702 (void *) context);
703 }
704
705
706 /*
707 * flatten_join_alias_vars
708 * Replace Vars that reference JOIN outputs with references to the original
709 * relation variables instead. This allows quals involving such vars to be
710 * pushed down. Whole-row Vars that reference JOIN relations are expanded
711 * into RowExpr constructs that name the individual output Vars. This
712 * is necessary since we will not scan the JOIN as a base relation, which
713 * is the only way that the executor can directly handle whole-row Vars.
714 *
715 * This also adjusts relid sets found in some expression node types to
716 * substitute the contained base rels for any join relid.
717 *
718 * If a JOIN contains sub-selects that have been flattened, its join alias
719 * entries might now be arbitrary expressions, not just Vars. This affects
720 * this function in one important way: we might find ourselves inserting
721 * SubLink expressions into subqueries, and we must make sure that their
722 * Query.hasSubLinks fields get set to true if so. If there are any
723 * SubLinks in the join alias lists, the outer Query should already have
724 * hasSubLinks = true, so this is only relevant to un-flattened subqueries.
725 *
726 * NOTE: this is used on not-yet-planned expressions. We do not expect it
727 * to be applied directly to the whole Query, so if we see a Query to start
728 * with, we do want to increment sublevels_up (this occurs for LATERAL
729 * subqueries).
730 */
731 Node *
flatten_join_alias_vars(Query * query,Node * node)732 flatten_join_alias_vars(Query *query, Node *node)
733 {
734 flatten_join_alias_vars_context context;
735
736 context.query = query;
737 context.sublevels_up = 0;
738 /* flag whether join aliases could possibly contain SubLinks */
739 context.possible_sublink = query->hasSubLinks;
740 /* if hasSubLinks is already true, no need to work hard */
741 context.inserted_sublink = query->hasSubLinks;
742
743 return flatten_join_alias_vars_mutator(node, &context);
744 }
745
746 static Node *
flatten_join_alias_vars_mutator(Node * node,flatten_join_alias_vars_context * context)747 flatten_join_alias_vars_mutator(Node *node,
748 flatten_join_alias_vars_context *context)
749 {
750 if (node == NULL)
751 return NULL;
752 if (IsA(node, Var))
753 {
754 Var *var = (Var *) node;
755 RangeTblEntry *rte;
756 Node *newvar;
757
758 /* No change unless Var belongs to a JOIN of the target level */
759 if (var->varlevelsup != context->sublevels_up)
760 return node; /* no need to copy, really */
761 rte = rt_fetch(var->varno, context->query->rtable);
762 if (rte->rtekind != RTE_JOIN)
763 return node;
764 if (var->varattno == InvalidAttrNumber)
765 {
766 /* Must expand whole-row reference */
767 RowExpr *rowexpr;
768 List *fields = NIL;
769 List *colnames = NIL;
770 AttrNumber attnum;
771 ListCell *lv;
772 ListCell *ln;
773
774 attnum = 0;
775 Assert(list_length(rte->joinaliasvars) == list_length(rte->eref->colnames));
776 forboth(lv, rte->joinaliasvars, ln, rte->eref->colnames)
777 {
778 newvar = (Node *) lfirst(lv);
779 attnum++;
780 /* Ignore dropped columns */
781 if (newvar == NULL)
782 continue;
783 newvar = copyObject(newvar);
784
785 /*
786 * If we are expanding an alias carried down from an upper
787 * query, must adjust its varlevelsup fields.
788 */
789 if (context->sublevels_up != 0)
790 IncrementVarSublevelsUp(newvar, context->sublevels_up, 0);
791 /* Preserve original Var's location, if possible */
792 if (IsA(newvar, Var))
793 ((Var *) newvar)->location = var->location;
794 /* Recurse in case join input is itself a join */
795 /* (also takes care of setting inserted_sublink if needed) */
796 newvar = flatten_join_alias_vars_mutator(newvar, context);
797 fields = lappend(fields, newvar);
798 /* We need the names of non-dropped columns, too */
799 colnames = lappend(colnames, copyObject((Node *) lfirst(ln)));
800 }
801 rowexpr = makeNode(RowExpr);
802 rowexpr->args = fields;
803 rowexpr->row_typeid = var->vartype;
804 rowexpr->row_format = COERCE_IMPLICIT_CAST;
805 rowexpr->colnames = colnames;
806 rowexpr->location = var->location;
807
808 return (Node *) rowexpr;
809 }
810
811 /* Expand join alias reference */
812 Assert(var->varattno > 0);
813 newvar = (Node *) list_nth(rte->joinaliasvars, var->varattno - 1);
814 Assert(newvar != NULL);
815 newvar = copyObject(newvar);
816
817 /*
818 * If we are expanding an alias carried down from an upper query, must
819 * adjust its varlevelsup fields.
820 */
821 if (context->sublevels_up != 0)
822 IncrementVarSublevelsUp(newvar, context->sublevels_up, 0);
823
824 /* Preserve original Var's location, if possible */
825 if (IsA(newvar, Var))
826 ((Var *) newvar)->location = var->location;
827
828 /* Recurse in case join input is itself a join */
829 newvar = flatten_join_alias_vars_mutator(newvar, context);
830
831 /* Detect if we are adding a sublink to query */
832 if (context->possible_sublink && !context->inserted_sublink)
833 context->inserted_sublink = checkExprHasSubLink(newvar);
834
835 return newvar;
836 }
837 if (IsA(node, PlaceHolderVar))
838 {
839 /* Copy the PlaceHolderVar node with correct mutation of subnodes */
840 PlaceHolderVar *phv;
841
842 phv = (PlaceHolderVar *) expression_tree_mutator(node,
843 flatten_join_alias_vars_mutator,
844 (void *) context);
845 /* now fix PlaceHolderVar's relid sets */
846 if (phv->phlevelsup == context->sublevels_up)
847 {
848 phv->phrels = alias_relid_set(context->query,
849 phv->phrels);
850 }
851 return (Node *) phv;
852 }
853
854 if (IsA(node, Query))
855 {
856 /* Recurse into RTE subquery or not-yet-planned sublink subquery */
857 Query *newnode;
858 bool save_inserted_sublink;
859
860 context->sublevels_up++;
861 save_inserted_sublink = context->inserted_sublink;
862 context->inserted_sublink = ((Query *) node)->hasSubLinks;
863 newnode = query_tree_mutator((Query *) node,
864 flatten_join_alias_vars_mutator,
865 (void *) context,
866 QTW_IGNORE_JOINALIASES);
867 newnode->hasSubLinks |= context->inserted_sublink;
868 context->inserted_sublink = save_inserted_sublink;
869 context->sublevels_up--;
870 return (Node *) newnode;
871 }
872 /* Already-planned tree not supported */
873 Assert(!IsA(node, SubPlan));
874 /* Shouldn't need to handle these planner auxiliary nodes here */
875 Assert(!IsA(node, SpecialJoinInfo));
876 Assert(!IsA(node, PlaceHolderInfo));
877 Assert(!IsA(node, MinMaxAggInfo));
878
879 return expression_tree_mutator(node, flatten_join_alias_vars_mutator,
880 (void *) context);
881 }
882
883 /*
884 * alias_relid_set: in a set of RT indexes, replace joins by their
885 * underlying base relids
886 */
887 static Relids
alias_relid_set(Query * query,Relids relids)888 alias_relid_set(Query *query, Relids relids)
889 {
890 Relids result = NULL;
891 int rtindex;
892
893 rtindex = -1;
894 while ((rtindex = bms_next_member(relids, rtindex)) >= 0)
895 {
896 RangeTblEntry *rte = rt_fetch(rtindex, query->rtable);
897
898 if (rte->rtekind == RTE_JOIN)
899 result = bms_join(result, get_relids_for_join(query, rtindex));
900 else
901 result = bms_add_member(result, rtindex);
902 }
903 return result;
904 }
905