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parse_collate.c
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1 /*-------------------------------------------------------------------------
2  *
3  * parse_collate.c
4  * Routines for assigning collation information.
5  *
6  * We choose to handle collation analysis in a post-pass over the output
7  * of expression parse analysis. This is because we need more state to
8  * perform this processing than is needed in the finished tree. If we
9  * did it on-the-fly while building the tree, all that state would have
10  * to be kept in expression node trees permanently. This way, the extra
11  * storage is just local variables in this recursive routine.
12  *
13  * The info that is actually saved in the finished tree is:
14  * 1. The output collation of each expression node, or InvalidOid if it
15  * returns a noncollatable data type. This can also be InvalidOid if the
16  * result type is collatable but the collation is indeterminate.
17  * 2. The collation to be used in executing each function. InvalidOid means
18  * that there are no collatable inputs or their collation is indeterminate.
19  * This value is only stored in node types that might call collation-using
20  * functions.
21  *
22  * You might think we could get away with storing only one collation per
23  * node, but the two concepts really need to be kept distinct. Otherwise
24  * it's too confusing when a function produces a collatable output type but
25  * has no collatable inputs or produces noncollatable output from collatable
26  * inputs.
27  *
28  * Cases with indeterminate collation might result in an error being thrown
29  * at runtime. If we knew exactly which functions require collation
30  * information, we could throw those errors at parse time instead.
31  *
32  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
33  * Portions Copyright (c) 1994, Regents of the University of California
34  *
35  *
36  * IDENTIFICATION
37  * src/backend/parser/parse_collate.c
38  *
39  *-------------------------------------------------------------------------
40  */
41 #include "postgres.h"
42 
43 #include "catalog/pg_aggregate.h"
44 #include "catalog/pg_collation.h"
45 #include "nodes/makefuncs.h"
46 #include "nodes/nodeFuncs.h"
47 #include "parser/parse_collate.h"
48 #include "utils/lsyscache.h"
49 
50 
51 /*
52  * Collation strength (the SQL standard calls this "derivation"). Order is
53  * chosen to allow comparisons to work usefully. Note: the standard doesn't
54  * seem to distinguish between NONE and CONFLICT.
55  */
56 typedef enum
57 {
58  COLLATE_NONE, /* expression is of a noncollatable datatype */
59  COLLATE_IMPLICIT, /* collation was derived implicitly */
60  COLLATE_CONFLICT, /* we had a conflict of implicit collations */
61  COLLATE_EXPLICIT /* collation was derived explicitly */
63 
64 typedef struct
65 {
66  ParseState *pstate; /* parse state (for error reporting) */
67  Oid collation; /* OID of current collation, if any */
68  CollateStrength strength; /* strength of current collation choice */
69  int location; /* location of expr that set collation */
70  /* Remaining fields are only valid when strength == COLLATE_CONFLICT */
71  Oid collation2; /* OID of conflicting collation */
72  int location2; /* location of expr that set collation2 */
74 
75 static bool assign_query_collations_walker(Node *node, ParseState *pstate);
76 static bool assign_collations_walker(Node *node,
77  assign_collations_context *context);
78 static void merge_collation_state(Oid collation,
79  CollateStrength strength,
80  int location,
81  Oid collation2,
82  int location2,
83  assign_collations_context *context);
84 static void assign_aggregate_collations(Aggref *aggref,
85  assign_collations_context *loccontext);
86 static void assign_ordered_set_collations(Aggref *aggref,
87  assign_collations_context *loccontext);
88 static void assign_hypothetical_collations(Aggref *aggref,
89  assign_collations_context *loccontext);
90 
91 
92 /*
93  * assign_query_collations()
94  * Mark all expressions in the given Query with collation information.
95  *
96  * This should be applied to each Query after completion of parse analysis
97  * for expressions. Note that we do not recurse into sub-Queries, since
98  * those should have been processed when built.
99  */
100 void
102 {
103  /*
104  * We just use query_tree_walker() to visit all the contained expressions.
105  * We can skip the rangetable and CTE subqueries, though, since RTEs and
106  * subqueries had better have been processed already (else Vars referring
107  * to them would not get created with the right collation).
108  */
109  (void) query_tree_walker(query,
111  (void *) pstate,
114 }
115 
116 /*
117  * Walker for assign_query_collations
118  *
119  * Each expression found by query_tree_walker is processed independently.
120  * Note that query_tree_walker may pass us a whole List, such as the
121  * targetlist, in which case each subexpression must be processed
122  * independently --- we don't want to bleat if two different targetentries
123  * have different collations.
124  */
125 static bool
127 {
128  /* Need do nothing for empty subexpressions */
129  if (node == NULL)
130  return false;
131 
132  /*
133  * We don't want to recurse into a set-operations tree; it's already been
134  * fully processed in transformSetOperationStmt.
135  */
136  if (IsA(node, SetOperationStmt))
137  return false;
138 
139  if (IsA(node, List))
140  assign_list_collations(pstate, (List *) node);
141  else
142  assign_expr_collations(pstate, node);
143 
144  return false;
145 }
146 
147 /*
148  * assign_list_collations()
149  * Mark all nodes in the list of expressions with collation information.
150  *
151  * The list member expressions are processed independently; they do not have
152  * to share a common collation.
153  */
154 void
156 {
157  ListCell *lc;
158 
159  foreach(lc, exprs)
160  {
161  Node *node = (Node *) lfirst(lc);
162 
163  assign_expr_collations(pstate, node);
164  }
165 }
166 
167 /*
168  * assign_expr_collations()
169  * Mark all nodes in the given expression tree with collation information.
170  *
171  * This is exported for the benefit of various utility commands that process
172  * expressions without building a complete Query. It should be applied after
173  * calling transformExpr() plus any expression-modifying operations such as
174  * coerce_to_boolean().
175  */
176 void
178 {
180 
181  /* initialize context for tree walk */
182  context.pstate = pstate;
183  context.collation = InvalidOid;
184  context.strength = COLLATE_NONE;
185  context.location = -1;
186 
187  /* and away we go */
188  (void) assign_collations_walker(expr, &context);
189 }
190 
191 /*
192  * select_common_collation()
193  * Identify a common collation for a list of expressions.
194  *
195  * The expressions should all return the same datatype, else this is not
196  * terribly meaningful.
197  *
198  * none_ok means that it is permitted to return InvalidOid, indicating that
199  * no common collation could be identified, even for collatable datatypes.
200  * Otherwise, an error is thrown for conflict of implicit collations.
201  *
202  * In theory, none_ok = true reflects the rules of SQL standard clause "Result
203  * of data type combinations", none_ok = false reflects the rules of clause
204  * "Collation determination" (in some cases invoked via "Grouping
205  * operations").
206  */
207 Oid
208 select_common_collation(ParseState *pstate, List *exprs, bool none_ok)
209 {
211 
212  /* initialize context for tree walk */
213  context.pstate = pstate;
214  context.collation = InvalidOid;
215  context.strength = COLLATE_NONE;
216  context.location = -1;
217 
218  /* and away we go */
219  (void) assign_collations_walker((Node *) exprs, &context);
220 
221  /* deal with collation conflict */
222  if (context.strength == COLLATE_CONFLICT)
223  {
224  if (none_ok)
225  return InvalidOid;
226  ereport(ERROR,
227  (errcode(ERRCODE_COLLATION_MISMATCH),
228  errmsg("collation mismatch between implicit collations \"%s\" and \"%s\"",
229  get_collation_name(context.collation),
230  get_collation_name(context.collation2)),
231  errhint("You can choose the collation by applying the COLLATE clause to one or both expressions."),
232  parser_errposition(context.pstate, context.location2)));
233  }
234 
235  /*
236  * Note: if strength is still COLLATE_NONE, we'll return InvalidOid, but
237  * that's okay because it must mean none of the expressions returned
238  * collatable datatypes.
239  */
240  return context.collation;
241 }
242 
243 /*
244  * assign_collations_walker()
245  * Recursive guts of collation processing.
246  *
247  * Nodes with no children (eg, Vars, Consts, Params) must have been marked
248  * when built. All upper-level nodes are marked here.
249  *
250  * Note: if this is invoked directly on a List, it will attempt to infer a
251  * common collation for all the list members. In particular, it will throw
252  * error if there are conflicting explicit collations for different members.
253  */
254 static bool
256 {
257  assign_collations_context loccontext;
258  Oid collation;
259  CollateStrength strength;
260  int location;
261 
262  /* Need do nothing for empty subexpressions */
263  if (node == NULL)
264  return false;
265 
266  /*
267  * Prepare for recursion. For most node types, though not all, the first
268  * thing we do is recurse to process all nodes below this one. Each level
269  * of the tree has its own local context.
270  */
271  loccontext.pstate = context->pstate;
272  loccontext.collation = InvalidOid;
273  loccontext.strength = COLLATE_NONE;
274  loccontext.location = -1;
275  /* Set these fields just to suppress uninitialized-value warnings: */
276  loccontext.collation2 = InvalidOid;
277  loccontext.location2 = -1;
278 
279  /*
280  * Recurse if appropriate, then determine the collation for this node.
281  *
282  * Note: the general cases are at the bottom of the switch, after various
283  * special cases.
284  */
285  switch (nodeTag(node))
286  {
287  case T_CollateExpr:
288  {
289  /*
290  * COLLATE sets an explicitly derived collation, regardless of
291  * what the child state is. But we must recurse to set up
292  * collation info below here.
293  */
294  CollateExpr *expr = (CollateExpr *) node;
295 
296  (void) expression_tree_walker(node,
298  (void *) &loccontext);
299 
300  collation = expr->collOid;
301  Assert(OidIsValid(collation));
302  strength = COLLATE_EXPLICIT;
303  location = expr->location;
304  }
305  break;
306  case T_FieldSelect:
307  {
308  /*
309  * For FieldSelect, the result has the field's declared
310  * collation, independently of what happened in the arguments.
311  * (The immediate argument must be composite and thus not
312  * collatable, anyhow.) The field's collation was already
313  * looked up and saved in the node.
314  */
315  FieldSelect *expr = (FieldSelect *) node;
316 
317  /* ... but first, recurse */
318  (void) expression_tree_walker(node,
320  (void *) &loccontext);
321 
322  if (OidIsValid(expr->resultcollid))
323  {
324  /* Node's result type is collatable. */
325  /* Pass up field's collation as an implicit choice. */
326  collation = expr->resultcollid;
327  strength = COLLATE_IMPLICIT;
328  location = exprLocation(node);
329  }
330  else
331  {
332  /* Node's result type isn't collatable. */
333  collation = InvalidOid;
334  strength = COLLATE_NONE;
335  location = -1; /* won't be used */
336  }
337  }
338  break;
339  case T_RowExpr:
340  {
341  /*
342  * RowExpr is a special case because the subexpressions are
343  * independent: we don't want to complain if some of them have
344  * incompatible explicit collations.
345  */
346  RowExpr *expr = (RowExpr *) node;
347 
348  assign_list_collations(context->pstate, expr->args);
349 
350  /*
351  * Since the result is always composite and therefore never
352  * has a collation, we can just stop here: this node has no
353  * impact on the collation of its parent.
354  */
355  return false; /* done */
356  }
357  case T_RowCompareExpr:
358  {
359  /*
360  * For RowCompare, we have to find the common collation of
361  * each pair of input columns and build a list. If we can't
362  * find a common collation, we just put InvalidOid into the
363  * list, which may or may not cause an error at runtime.
364  */
365  RowCompareExpr *expr = (RowCompareExpr *) node;
366  List *colls = NIL;
367  ListCell *l;
368  ListCell *r;
369 
370  forboth(l, expr->largs, r, expr->rargs)
371  {
372  Node *le = (Node *) lfirst(l);
373  Node *re = (Node *) lfirst(r);
374  Oid coll;
375 
376  coll = select_common_collation(context->pstate,
377  list_make2(le, re),
378  true);
379  colls = lappend_oid(colls, coll);
380  }
381  expr->inputcollids = colls;
382 
383  /*
384  * Since the result is always boolean and therefore never has
385  * a collation, we can just stop here: this node has no impact
386  * on the collation of its parent.
387  */
388  return false; /* done */
389  }
390  case T_CoerceToDomain:
391  {
392  /*
393  * If the domain declaration included a non-default COLLATE
394  * spec, then use that collation as the output collation of
395  * the coercion. Otherwise allow the input collation to
396  * bubble up. (The input should be of the domain's base type,
397  * therefore we don't need to worry about it not being
398  * collatable when the domain is.)
399  */
400  CoerceToDomain *expr = (CoerceToDomain *) node;
401  Oid typcollation = get_typcollation(expr->resulttype);
402 
403  /* ... but first, recurse */
404  (void) expression_tree_walker(node,
406  (void *) &loccontext);
407 
408  if (OidIsValid(typcollation))
409  {
410  /* Node's result type is collatable. */
411  if (typcollation == DEFAULT_COLLATION_OID)
412  {
413  /* Collation state bubbles up from child. */
414  collation = loccontext.collation;
415  strength = loccontext.strength;
416  location = loccontext.location;
417  }
418  else
419  {
420  /* Use domain's collation as an implicit choice. */
421  collation = typcollation;
422  strength = COLLATE_IMPLICIT;
423  location = exprLocation(node);
424  }
425  }
426  else
427  {
428  /* Node's result type isn't collatable. */
429  collation = InvalidOid;
430  strength = COLLATE_NONE;
431  location = -1; /* won't be used */
432  }
433 
434  /*
435  * Save the state into the expression node. We know it
436  * doesn't care about input collation.
437  */
438  if (strength == COLLATE_CONFLICT)
440  else
441  exprSetCollation(node, collation);
442  }
443  break;
444  case T_TargetEntry:
445  (void) expression_tree_walker(node,
447  (void *) &loccontext);
448 
449  /*
450  * TargetEntry can have only one child, and should bubble that
451  * state up to its parent. We can't use the general-case code
452  * below because exprType and friends don't work on TargetEntry.
453  */
454  collation = loccontext.collation;
455  strength = loccontext.strength;
456  location = loccontext.location;
457 
458  /*
459  * Throw error if the collation is indeterminate for a TargetEntry
460  * that is a sort/group target. We prefer to do this now, instead
461  * of leaving the comparison functions to fail at runtime, because
462  * we can give a syntax error pointer to help locate the problem.
463  * There are some cases where there might not be a failure, for
464  * example if the planner chooses to use hash aggregation instead
465  * of sorting for grouping; but it seems better to predictably
466  * throw an error. (Compare transformSetOperationTree, which will
467  * throw error for indeterminate collation of set-op columns, even
468  * though the planner might be able to implement the set-op
469  * without sorting.)
470  */
471  if (strength == COLLATE_CONFLICT &&
472  ((TargetEntry *) node)->ressortgroupref != 0)
473  ereport(ERROR,
474  (errcode(ERRCODE_COLLATION_MISMATCH),
475  errmsg("collation mismatch between implicit collations \"%s\" and \"%s\"",
476  get_collation_name(loccontext.collation),
477  get_collation_name(loccontext.collation2)),
478  errhint("You can choose the collation by applying the COLLATE clause to one or both expressions."),
479  parser_errposition(context->pstate,
480  loccontext.location2)));
481  break;
482  case T_InferenceElem:
483  case T_RangeTblRef:
484  case T_JoinExpr:
485  case T_FromExpr:
486  case T_OnConflictExpr:
487  case T_SortGroupClause:
488  (void) expression_tree_walker(node,
490  (void *) &loccontext);
491 
492  /*
493  * When we're invoked on a query's jointree, we don't need to do
494  * anything with join nodes except recurse through them to process
495  * WHERE/ON expressions. So just stop here. Likewise, we don't
496  * need to do anything when invoked on sort/group lists.
497  */
498  return false;
499  case T_Query:
500  {
501  /*
502  * We get here when we're invoked on the Query belonging to a
503  * SubLink. Act as though the Query returns its first output
504  * column, which indeed is what it does for EXPR_SUBLINK and
505  * ARRAY_SUBLINK cases. In the cases where the SubLink
506  * returns boolean, this info will be ignored. Special case:
507  * in EXISTS, the Query might return no columns, in which case
508  * we need do nothing.
509  *
510  * We needn't recurse, since the Query is already processed.
511  */
512  Query *qtree = (Query *) node;
513  TargetEntry *tent;
514 
515  if (qtree->targetList == NIL)
516  return false;
517  tent = linitial_node(TargetEntry, qtree->targetList);
518  if (tent->resjunk)
519  return false;
520 
521  collation = exprCollation((Node *) tent->expr);
522  /* collation doesn't change if it's converted to array */
523  strength = COLLATE_IMPLICIT;
524  location = exprLocation((Node *) tent->expr);
525  }
526  break;
527  case T_List:
528  (void) expression_tree_walker(node,
530  (void *) &loccontext);
531 
532  /*
533  * When processing a list, collation state just bubbles up from
534  * the list elements.
535  */
536  collation = loccontext.collation;
537  strength = loccontext.strength;
538  location = loccontext.location;
539  break;
540 
541  case T_Var:
542  case T_Const:
543  case T_Param:
545  case T_CaseTestExpr:
546  case T_SetToDefault:
547  case T_CurrentOfExpr:
548 
549  /*
550  * General case for childless expression nodes. These should
551  * already have a collation assigned; it is not this function's
552  * responsibility to look into the catalogs for base-case
553  * information.
554  */
555  collation = exprCollation(node);
556 
557  /*
558  * Note: in most cases, there will be an assigned collation
559  * whenever type_is_collatable(exprType(node)); but an exception
560  * occurs for a Var referencing a subquery output column for which
561  * a unique collation was not determinable. That may lead to a
562  * runtime failure if a collation-sensitive function is applied to
563  * the Var.
564  */
565 
566  if (OidIsValid(collation))
567  strength = COLLATE_IMPLICIT;
568  else
569  strength = COLLATE_NONE;
570  location = exprLocation(node);
571  break;
572 
573  default:
574  {
575  /*
576  * General case for most expression nodes with children. First
577  * recurse, then figure out what to assign to this node.
578  */
579  Oid typcollation;
580 
581  /*
582  * For most node types, we want to treat all the child
583  * expressions alike; but there are a few exceptions, hence
584  * this inner switch.
585  */
586  switch (nodeTag(node))
587  {
588  case T_Aggref:
589  {
590  /*
591  * Aggref is messy enough that we give it its own
592  * function, in fact three of them. The FILTER
593  * clause is independent of the rest of the
594  * aggregate, however, so it can be processed
595  * separately.
596  */
597  Aggref *aggref = (Aggref *) node;
598 
599  switch (aggref->aggkind)
600  {
601  case AGGKIND_NORMAL:
603  &loccontext);
604  break;
605  case AGGKIND_ORDERED_SET:
607  &loccontext);
608  break;
611  &loccontext);
612  break;
613  default:
614  elog(ERROR, "unrecognized aggkind: %d",
615  (int) aggref->aggkind);
616  }
617 
619  (Node *) aggref->aggfilter);
620  }
621  break;
622  case T_WindowFunc:
623  {
624  /*
625  * WindowFunc requires special processing only for
626  * its aggfilter clause, as for aggregates.
627  */
628  WindowFunc *wfunc = (WindowFunc *) node;
629 
630  (void) assign_collations_walker((Node *) wfunc->args,
631  &loccontext);
632 
634  (Node *) wfunc->aggfilter);
635  }
636  break;
637  case T_CaseExpr:
638  {
639  /*
640  * CaseExpr is a special case because we do not
641  * want to recurse into the test expression (if
642  * any). It was already marked with collations
643  * during transformCaseExpr, and furthermore its
644  * collation is not relevant to the result of the
645  * CASE --- only the output expressions are.
646  */
647  CaseExpr *expr = (CaseExpr *) node;
648  ListCell *lc;
649 
650  foreach(lc, expr->args)
651  {
653 
654  /*
655  * The condition expressions mustn't affect
656  * the CASE's result collation either; but
657  * since they are known to yield boolean, it's
658  * safe to recurse directly on them --- they
659  * won't change loccontext.
660  */
661  (void) assign_collations_walker((Node *) when->expr,
662  &loccontext);
663  (void) assign_collations_walker((Node *) when->result,
664  &loccontext);
665  }
666  (void) assign_collations_walker((Node *) expr->defresult,
667  &loccontext);
668  }
669  break;
670  default:
671 
672  /*
673  * Normal case: all child expressions contribute
674  * equally to loccontext.
675  */
676  (void) expression_tree_walker(node,
678  (void *) &loccontext);
679  break;
680  }
681 
682  /*
683  * Now figure out what collation to assign to this node.
684  */
685  typcollation = get_typcollation(exprType(node));
686  if (OidIsValid(typcollation))
687  {
688  /* Node's result is collatable; what about its input? */
689  if (loccontext.strength > COLLATE_NONE)
690  {
691  /* Collation state bubbles up from children. */
692  collation = loccontext.collation;
693  strength = loccontext.strength;
694  location = loccontext.location;
695  }
696  else
697  {
698  /*
699  * Collatable output produced without any collatable
700  * input. Use the type's collation (which is usually
701  * DEFAULT_COLLATION_OID, but might be different for a
702  * domain).
703  */
704  collation = typcollation;
705  strength = COLLATE_IMPLICIT;
706  location = exprLocation(node);
707  }
708  }
709  else
710  {
711  /* Node's result type isn't collatable. */
712  collation = InvalidOid;
713  strength = COLLATE_NONE;
714  location = -1; /* won't be used */
715  }
716 
717  /*
718  * Save the result collation into the expression node. If the
719  * state is COLLATE_CONFLICT, we'll set the collation to
720  * InvalidOid, which might result in an error at runtime.
721  */
722  if (strength == COLLATE_CONFLICT)
724  else
725  exprSetCollation(node, collation);
726 
727  /*
728  * Likewise save the input collation, which is the one that
729  * any function called by this node should use.
730  */
731  if (loccontext.strength == COLLATE_CONFLICT)
733  else
734  exprSetInputCollation(node, loccontext.collation);
735  }
736  break;
737  }
738 
739  /*
740  * Now, merge my information into my parent's state.
741  */
742  merge_collation_state(collation,
743  strength,
744  location,
745  loccontext.collation2,
746  loccontext.location2,
747  context);
748 
749  return false;
750 }
751 
752 /*
753  * Merge collation state of a subexpression into the context for its parent.
754  */
755 static void
757  CollateStrength strength,
758  int location,
759  Oid collation2,
760  int location2,
761  assign_collations_context *context)
762 {
763  /*
764  * If the collation strength for this node is different from what's
765  * already in *context, then this node either dominates or is dominated by
766  * earlier siblings.
767  */
768  if (strength > context->strength)
769  {
770  /* Override previous parent state */
771  context->collation = collation;
772  context->strength = strength;
773  context->location = location;
774  /* Bubble up error info if applicable */
775  if (strength == COLLATE_CONFLICT)
776  {
777  context->collation2 = collation2;
778  context->location2 = location2;
779  }
780  }
781  else if (strength == context->strength)
782  {
783  /* Merge, or detect error if there's a collation conflict */
784  switch (strength)
785  {
786  case COLLATE_NONE:
787  /* Nothing + nothing is still nothing */
788  break;
789  case COLLATE_IMPLICIT:
790  if (collation != context->collation)
791  {
792  /*
793  * Non-default implicit collation always beats default.
794  */
795  if (context->collation == DEFAULT_COLLATION_OID)
796  {
797  /* Override previous parent state */
798  context->collation = collation;
799  context->strength = strength;
800  context->location = location;
801  }
802  else if (collation != DEFAULT_COLLATION_OID)
803  {
804  /*
805  * Oops, we have a conflict. We cannot throw error
806  * here, since the conflict could be resolved by a
807  * later sibling CollateExpr, or the parent might not
808  * care about collation anyway. Return enough info to
809  * throw the error later, if needed.
810  */
811  context->strength = COLLATE_CONFLICT;
812  context->collation2 = collation;
813  context->location2 = location;
814  }
815  }
816  break;
817  case COLLATE_CONFLICT:
818  /* We're still conflicted ... */
819  break;
820  case COLLATE_EXPLICIT:
821  if (collation != context->collation)
822  {
823  /*
824  * Oops, we have a conflict of explicit COLLATE clauses.
825  * Here we choose to throw error immediately; that is what
826  * the SQL standard says to do, and there's no good reason
827  * to be less strict.
828  */
829  ereport(ERROR,
830  (errcode(ERRCODE_COLLATION_MISMATCH),
831  errmsg("collation mismatch between explicit collations \"%s\" and \"%s\"",
832  get_collation_name(context->collation),
833  get_collation_name(collation)),
834  parser_errposition(context->pstate, location)));
835  }
836  break;
837  }
838  }
839 }
840 
841 /*
842  * Aggref is a special case because expressions used only for ordering
843  * shouldn't be taken to conflict with each other or with regular args,
844  * indeed shouldn't affect the aggregate's result collation at all.
845  * We handle this by applying assign_expr_collations() to them rather than
846  * passing down our loccontext.
847  *
848  * Note that we recurse to each TargetEntry, not directly to its contained
849  * expression, so that the case above for T_TargetEntry will complain if we
850  * can't resolve a collation for an ORDER BY item (whether or not it is also
851  * a normal aggregate arg).
852  *
853  * We need not recurse into the aggorder or aggdistinct lists, because those
854  * contain only SortGroupClause nodes which we need not process.
855  */
856 static void
858  assign_collations_context *loccontext)
859 {
860  ListCell *lc;
861 
862  /* Plain aggregates have no direct args */
863  Assert(aggref->aggdirectargs == NIL);
864 
865  /* Process aggregated args, holding resjunk ones at arm's length */
866  foreach(lc, aggref->args)
867  {
868  TargetEntry *tle = lfirst_node(TargetEntry, lc);
869 
870  if (tle->resjunk)
871  assign_expr_collations(loccontext->pstate, (Node *) tle);
872  else
873  (void) assign_collations_walker((Node *) tle, loccontext);
874  }
875 }
876 
877 /*
878  * For ordered-set aggregates, it's somewhat unclear how best to proceed.
879  * The spec-defined inverse distribution functions have only one sort column
880  * and don't return collatable types, but this is clearly too restrictive in
881  * the general case. Our solution is to consider that the aggregate's direct
882  * arguments contribute normally to determination of the aggregate's own
883  * collation, while aggregated arguments contribute only when the aggregate
884  * is designed to have exactly one aggregated argument (i.e., it has a single
885  * aggregated argument and is non-variadic). If it can have more than one
886  * aggregated argument, we process the aggregated arguments as independent
887  * sort columns. This avoids throwing error for something like
888  * agg(...) within group (order by x collate "foo", y collate "bar")
889  * while also guaranteeing that variadic aggregates don't change in behavior
890  * depending on how many sort columns a particular call happens to have.
891  *
892  * Otherwise this is much like the plain-aggregate case.
893  */
894 static void
896  assign_collations_context *loccontext)
897 {
898  bool merge_sort_collations;
899  ListCell *lc;
900 
901  /* Merge sort collations to parent only if there can be only one */
902  merge_sort_collations = (list_length(aggref->args) == 1 &&
904 
905  /* Direct args, if any, are normal children of the Aggref node */
906  (void) assign_collations_walker((Node *) aggref->aggdirectargs,
907  loccontext);
908 
909  /* Process aggregated args appropriately */
910  foreach(lc, aggref->args)
911  {
912  TargetEntry *tle = lfirst_node(TargetEntry, lc);
913 
914  if (merge_sort_collations)
915  (void) assign_collations_walker((Node *) tle, loccontext);
916  else
917  assign_expr_collations(loccontext->pstate, (Node *) tle);
918  }
919 }
920 
921 /*
922  * Hypothetical-set aggregates are even more special: per spec, we need to
923  * unify the collations of each pair of hypothetical and aggregated args.
924  * And we need to force the choice of collation down into the sort column
925  * to ensure that the sort happens with the chosen collation. Other than
926  * that, the behavior is like regular ordered-set aggregates. Note that
927  * hypothetical direct arguments contribute to the aggregate collation
928  * only when their partner aggregated arguments do.
929  */
930 static void
932  assign_collations_context *loccontext)
933 {
934  ListCell *h_cell = list_head(aggref->aggdirectargs);
935  ListCell *s_cell = list_head(aggref->args);
936  bool merge_sort_collations;
937  int extra_args;
938 
939  /* Merge sort collations to parent only if there can be only one */
940  merge_sort_collations = (list_length(aggref->args) == 1 &&
942 
943  /* Process any non-hypothetical direct args */
944  extra_args = list_length(aggref->aggdirectargs) - list_length(aggref->args);
945  Assert(extra_args >= 0);
946  while (extra_args-- > 0)
947  {
948  (void) assign_collations_walker((Node *) lfirst(h_cell), loccontext);
949  h_cell = lnext(h_cell);
950  }
951 
952  /* Scan hypothetical args and aggregated args in parallel */
953  while (h_cell && s_cell)
954  {
955  Node *h_arg = (Node *) lfirst(h_cell);
956  TargetEntry *s_tle = (TargetEntry *) lfirst(s_cell);
957  assign_collations_context paircontext;
958 
959  /*
960  * Assign collations internally in this pair of expressions, then
961  * choose a common collation for them. This should match
962  * select_common_collation(), but we can't use that function as-is
963  * because we need access to the whole collation state so we can
964  * bubble it up to the aggregate function's level.
965  */
966  paircontext.pstate = loccontext->pstate;
967  paircontext.collation = InvalidOid;
968  paircontext.strength = COLLATE_NONE;
969  paircontext.location = -1;
970  /* Set these fields just to suppress uninitialized-value warnings: */
971  paircontext.collation2 = InvalidOid;
972  paircontext.location2 = -1;
973 
974  (void) assign_collations_walker(h_arg, &paircontext);
975  (void) assign_collations_walker((Node *) s_tle->expr, &paircontext);
976 
977  /* deal with collation conflict */
978  if (paircontext.strength == COLLATE_CONFLICT)
979  ereport(ERROR,
980  (errcode(ERRCODE_COLLATION_MISMATCH),
981  errmsg("collation mismatch between implicit collations \"%s\" and \"%s\"",
982  get_collation_name(paircontext.collation),
983  get_collation_name(paircontext.collation2)),
984  errhint("You can choose the collation by applying the COLLATE clause to one or both expressions."),
985  parser_errposition(paircontext.pstate,
986  paircontext.location2)));
987 
988  /*
989  * At this point paircontext.collation can be InvalidOid only if the
990  * type is not collatable; no need to do anything in that case. If we
991  * do have to change the sort column's collation, do it by inserting a
992  * RelabelType node into the sort column TLE.
993  *
994  * XXX This is pretty grotty for a couple of reasons:
995  * assign_collations_walker isn't supposed to be changing the
996  * expression structure like this, and a parse-time change of
997  * collation ought to be signaled by a CollateExpr not a RelabelType
998  * (the use of RelabelType for collation marking is supposed to be a
999  * planner/executor thing only). But we have no better alternative.
1000  * In particular, injecting a CollateExpr could result in the
1001  * expression being interpreted differently after dump/reload, since
1002  * we might be effectively promoting an implicit collation to
1003  * explicit. This kluge is relying on ruleutils.c not printing a
1004  * COLLATE clause for a RelabelType, and probably on some other
1005  * fragile behaviors.
1006  */
1007  if (OidIsValid(paircontext.collation) &&
1008  paircontext.collation != exprCollation((Node *) s_tle->expr))
1009  {
1010  s_tle->expr = (Expr *)
1011  makeRelabelType(s_tle->expr,
1012  exprType((Node *) s_tle->expr),
1013  exprTypmod((Node *) s_tle->expr),
1014  paircontext.collation,
1016  }
1017 
1018  /*
1019  * If appropriate, merge this column's collation state up to the
1020  * aggregate function.
1021  */
1022  if (merge_sort_collations)
1023  merge_collation_state(paircontext.collation,
1024  paircontext.strength,
1025  paircontext.location,
1026  paircontext.collation2,
1027  paircontext.location2,
1028  loccontext);
1029 
1030  h_cell = lnext(h_cell);
1031  s_cell = lnext(s_cell);
1032  }
1033  Assert(h_cell == NULL && s_cell == NULL);
1034 }
#define list_make2(x1, x2)
Definition: pg_list.h:140
#define NIL
Definition: pg_list.h:69
bool query_tree_walker(Query *query, bool(*walker)(), void *context, int flags)
Definition: nodeFuncs.c:2245
List * args
Definition: primnodes.h:990
#define IsA(nodeptr, _type_)
Definition: nodes.h:562
int errhint(const char *fmt,...)
Definition: elog.c:987
#define forboth(cell1, list1, cell2, list2)
Definition: pg_list.h:180
int exprLocation(const Node *expr)
Definition: nodeFuncs.c:1186
List * args
Definition: primnodes.h:359
int32 exprTypmod(const Node *expr)
Definition: nodeFuncs.c:276
char * get_collation_name(Oid colloid)
Definition: lsyscache.c:967
Definition: nodes.h:511
int errcode(int sqlerrcode)
Definition: elog.c:575
List * args
Definition: primnodes.h:301
unsigned int Oid
Definition: postgres_ext.h:31
#define linitial_node(type, l)
Definition: pg_list.h:114
List * lappend_oid(List *list, Oid datum)
Definition: list.c:164
#define OidIsValid(objectId)
Definition: c.h:576
List * targetList
Definition: parsenodes.h:138
#define QTW_IGNORE_CTE_SUBQUERIES
Definition: nodeFuncs.h:21
void assign_expr_collations(ParseState *pstate, Node *expr)
bool resjunk
Definition: primnodes.h:1382
#define ERROR
Definition: elog.h:43
static bool assign_query_collations_walker(Node *node, ParseState *pstate)
Oid resultcollid
Definition: primnodes.h:747
#define lfirst_node(type, lc)
Definition: pg_list.h:109
void assign_list_collations(ParseState *pstate, List *exprs)
Oid get_func_variadictype(Oid funcid)
Definition: lsyscache.c:1527
RelabelType * makeRelabelType(Expr *arg, Oid rtype, int32 rtypmod, Oid rcollid, CoercionForm rformat)
Definition: makefuncs.c:401
#define DEFAULT_COLLATION_OID
Definition: pg_collation.h:75
Oid select_common_collation(ParseState *pstate, List *exprs, bool none_ok)
#define AGGKIND_NORMAL
Definition: pg_aggregate.h:128
static ListCell * list_head(const List *l)
Definition: pg_list.h:77
List * aggdirectargs
Definition: primnodes.h:300
Definition: type.h:82
#define lnext(lc)
Definition: pg_list.h:105
#define ereport(elevel, rest)
Definition: elog.h:122
Definition: nodes.h:292
Definition: nodes.h:147
Definition: nodes.h:146
List * args
Definition: primnodes.h:913
Definition: nodes.h:305
void exprSetInputCollation(Node *expr, Oid inputcollation)
Definition: nodeFuncs.c:1122
#define InvalidOid
Definition: postgres_ext.h:36
CollateStrength strength
Definition: parse_collate.c:68
Oid aggfnoid
Definition: primnodes.h:294
static void assign_aggregate_collations(Aggref *aggref, assign_collations_context *loccontext)
Oid get_typcollation(Oid typid)
Definition: lsyscache.c:2795
#define Assert(condition)
Definition: c.h:670
#define lfirst(lc)
Definition: pg_list.h:106
static void assign_ordered_set_collations(Aggref *aggref, assign_collations_context *loccontext)
Expr * aggfilter
Definition: primnodes.h:360
Expr * expr
Definition: primnodes.h:1375
static void assign_hypothetical_collations(Aggref *aggref, assign_collations_context *loccontext)
Oid exprType(const Node *expr)
Definition: nodeFuncs.c:42
bool expression_tree_walker(Node *node, bool(*walker)(), void *context)
Definition: nodeFuncs.c:1834
static int list_length(const List *l)
Definition: pg_list.h:89
int parser_errposition(ParseState *pstate, int location)
Definition: parse_node.c:111
Oid exprCollation(const Node *expr)
Definition: nodeFuncs.c:720
Expr * aggfilter
Definition: primnodes.h:304
#define nodeTag(nodeptr)
Definition: nodes.h:516
void exprSetCollation(Node *expr, Oid collation)
Definition: nodeFuncs.c:969
int errmsg(const char *fmt,...)
Definition: elog.c:797
void assign_query_collations(ParseState *pstate, Query *query)
#define QTW_IGNORE_RANGE_TABLE
Definition: nodeFuncs.h:24
char aggkind
Definition: primnodes.h:308
#define elog
Definition: elog.h:219
Expr * result
Definition: primnodes.h:925
static bool assign_collations_walker(Node *node, assign_collations_context *context)
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Definition: primnodes.h:1041
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Definition: primnodes.h:914
Expr * expr
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Definition: primnodes.h:882
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Definition: parse_collate.c:56
#define AGGKIND_HYPOTHETICAL
Definition: pg_aggregate.h:130
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static void merge_collation_state(Oid collation, CollateStrength strength, int location, Oid collation2, int location2, assign_collations_context *context)
#define AGGKIND_ORDERED_SET
Definition: pg_aggregate.h:129
Definition: nodes.h:148