1 /*-------------------------------------------------------------------------
4 * Primary module of query rewriter.
6 * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
10 * $PostgreSQL: pgsql/src/backend/rewrite/rewriteHandler.c,v 1.167 2006/10/04 00:29:56 momjian Exp $
12 *-------------------------------------------------------------------------
16 #include "access/heapam.h"
17 #include "catalog/pg_type.h"
18 #include "nodes/makefuncs.h"
19 #include "optimizer/clauses.h"
20 #include "parser/analyze.h"
21 #include "parser/parse_coerce.h"
22 #include "parser/parse_expr.h"
23 #include "parser/parsetree.h"
24 #include "rewrite/rewriteHandler.h"
25 #include "rewrite/rewriteManip.h"
26 #include "utils/builtins.h"
27 #include "utils/lsyscache.h"
30 /* We use a list of these to detect recursion in RewriteQuery */
31 typedef struct rewrite_event
33 Oid relation; /* OID of relation having rules */
34 CmdType event; /* type of rule being fired */
37 static bool acquireLocksOnSubLinks(Node *node, void *context);
38 static Query *rewriteRuleAction(Query *parsetree,
43 bool *returning_flag);
44 static List *adjustJoinTreeList(Query *parsetree, bool removert, int rt_index);
45 static void rewriteTargetList(Query *parsetree, Relation target_relation,
47 static TargetEntry *process_matched_tle(TargetEntry *src_tle,
48 TargetEntry *prior_tle,
49 const char *attrName);
50 static Node *get_assignment_input(Node *node);
51 static void rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation,
53 static void markQueryForLocking(Query *qry, bool forUpdate, bool noWait,
55 static List *matchLocks(CmdType event, RuleLock *rulelocks,
56 int varno, Query *parsetree);
57 static Query *fireRIRrules(Query *parsetree, List *activeRIRs);
61 * AcquireRewriteLocks -
62 * Acquire suitable locks on all the relations mentioned in the Query.
63 * These locks will ensure that the relation schemas don't change under us
64 * while we are rewriting and planning the query.
66 * A secondary purpose of this routine is to fix up JOIN RTE references to
67 * dropped columns (see details below). Because the RTEs are modified in
68 * place, it is generally appropriate for the caller of this routine to have
69 * first done a copyObject() to make a writable copy of the querytree in the
70 * current memory context.
72 * This processing can, and for efficiency's sake should, be skipped when the
73 * querytree has just been built by the parser: parse analysis already got
74 * all the same locks we'd get here, and the parser will have omitted dropped
75 * columns from JOINs to begin with. But we must do this whenever we are
76 * dealing with a querytree produced earlier than the current command.
78 * About JOINs and dropped columns: although the parser never includes an
79 * already-dropped column in a JOIN RTE's alias var list, it is possible for
80 * such a list in a stored rule to include references to dropped columns.
81 * (If the column is not explicitly referenced anywhere else in the query,
82 * the dependency mechanism won't consider it used by the rule and so won't
83 * prevent the column drop.) To support get_rte_attribute_is_dropped(),
84 * we replace join alias vars that reference dropped columns with NULL Const
87 * (In PostgreSQL 8.0, we did not do this processing but instead had
88 * get_rte_attribute_is_dropped() recurse to detect dropped columns in joins.
89 * That approach had horrible performance unfortunately; in particular
90 * construction of a nested join was O(N^2) in the nesting depth.)
93 AcquireRewriteLocks(Query *parsetree)
99 * First, process RTEs of the current query level.
102 foreach(l, parsetree->rtable)
104 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
109 RangeTblEntry *curinputrte;
113 switch (rte->rtekind)
118 * Grab the appropriate lock type for the relation, and do not
119 * release it until end of transaction. This protects the
120 * rewriter and planner against schema changes mid-query.
122 * If the relation is the query's result relation, then we
123 * need RowExclusiveLock. Otherwise, check to see if the
124 * relation is accessed FOR UPDATE/SHARE or not. We can't
125 * just grab AccessShareLock because then the executor would
126 * be trying to upgrade the lock, leading to possible
129 if (rt_index == parsetree->resultRelation)
130 lockmode = RowExclusiveLock;
131 else if (get_rowmark(parsetree, rt_index))
132 lockmode = RowShareLock;
134 lockmode = AccessShareLock;
136 rel = heap_open(rte->relid, lockmode);
137 heap_close(rel, NoLock);
143 * Scan the join's alias var list to see if any columns have
144 * been dropped, and if so replace those Vars with NULL
147 * Since a join has only two inputs, we can expect to see
148 * multiple references to the same input RTE; optimize away
154 foreach(ll, rte->joinaliasvars)
156 Var *aliasvar = (Var *) lfirst(ll);
159 * If the list item isn't a simple Var, then it must
160 * represent a merged column, ie a USING column, and so it
161 * couldn't possibly be dropped, since it's referenced in
162 * the join clause. (Conceivably it could also be a NULL
163 * constant already? But that's OK too.)
165 if (IsA(aliasvar, Var))
168 * The elements of an alias list have to refer to
169 * earlier RTEs of the same rtable, because that's the
170 * order the planner builds things in. So we already
171 * processed the referenced RTE, and so it's safe to
172 * use get_rte_attribute_is_dropped on it. (This might
173 * not hold after rewriting or planning, but it's OK
176 Assert(aliasvar->varlevelsup == 0);
177 if (aliasvar->varno != curinputvarno)
179 curinputvarno = aliasvar->varno;
180 if (curinputvarno >= rt_index)
181 elog(ERROR, "unexpected varno %d in JOIN RTE %d",
182 curinputvarno, rt_index);
183 curinputrte = rt_fetch(curinputvarno,
186 if (get_rte_attribute_is_dropped(curinputrte,
190 * can't use vartype here, since that might be a
191 * now-dropped type OID, but it doesn't really
192 * matter what type the Const claims to be.
194 aliasvar = (Var *) makeNullConst(INT4OID);
197 newaliasvars = lappend(newaliasvars, aliasvar);
199 rte->joinaliasvars = newaliasvars;
205 * The subquery RTE itself is all right, but we have to
206 * recurse to process the represented subquery.
208 AcquireRewriteLocks(rte->subquery);
212 /* ignore other types of RTEs */
218 * Recurse into sublink subqueries, too. But we already did the ones in
221 if (parsetree->hasSubLinks)
222 query_tree_walker(parsetree, acquireLocksOnSubLinks, NULL,
223 QTW_IGNORE_RT_SUBQUERIES);
227 * Walker to find sublink subqueries for AcquireRewriteLocks
230 acquireLocksOnSubLinks(Node *node, void *context)
234 if (IsA(node, SubLink))
236 SubLink *sub = (SubLink *) node;
238 /* Do what we came for */
239 AcquireRewriteLocks((Query *) sub->subselect);
240 /* Fall through to process lefthand args of SubLink */
244 * Do NOT recurse into Query nodes, because AcquireRewriteLocks already
245 * processed subselects of subselects for us.
247 return expression_tree_walker(node, acquireLocksOnSubLinks, context);
252 * rewriteRuleAction -
253 * Rewrite the rule action with appropriate qualifiers (taken from
254 * the triggering query).
257 * parsetree - original query
258 * rule_action - one action (query) of a rule
259 * rule_qual - WHERE condition of rule, or NULL if unconditional
260 * rt_index - RT index of result relation in original query
261 * event - type of rule event
263 * *returning_flag - set TRUE if we rewrite RETURNING clause in rule_action
264 * (must be initialized to FALSE)
266 * rewritten form of rule_action
269 rewriteRuleAction(Query *parsetree,
274 bool *returning_flag)
280 Query **sub_action_ptr;
283 * Make modifiable copies of rule action and qual (what we're passed are
284 * the stored versions in the relcache; don't touch 'em!).
286 rule_action = (Query *) copyObject(rule_action);
287 rule_qual = (Node *) copyObject(rule_qual);
290 * Acquire necessary locks and fix any deleted JOIN RTE entries.
292 AcquireRewriteLocks(rule_action);
293 (void) acquireLocksOnSubLinks(rule_qual, NULL);
295 current_varno = rt_index;
296 rt_length = list_length(parsetree->rtable);
297 new_varno = PRS2_NEW_VARNO + rt_length;
300 * Adjust rule action and qual to offset its varnos, so that we can merge
301 * its rtable with the main parsetree's rtable.
303 * If the rule action is an INSERT...SELECT, the OLD/NEW rtable entries
304 * will be in the SELECT part, and we have to modify that rather than the
305 * top-level INSERT (kluge!).
307 sub_action = getInsertSelectQuery(rule_action, &sub_action_ptr);
309 OffsetVarNodes((Node *) sub_action, rt_length, 0);
310 OffsetVarNodes(rule_qual, rt_length, 0);
311 /* but references to *OLD* should point at original rt_index */
312 ChangeVarNodes((Node *) sub_action,
313 PRS2_OLD_VARNO + rt_length, rt_index, 0);
314 ChangeVarNodes(rule_qual,
315 PRS2_OLD_VARNO + rt_length, rt_index, 0);
318 * Generate expanded rtable consisting of main parsetree's rtable plus
319 * rule action's rtable; this becomes the complete rtable for the rule
320 * action. Some of the entries may be unused after we finish rewriting,
321 * but we leave them all in place for two reasons:
323 * We'd have a much harder job to adjust the query's varnos if we
324 * selectively removed RT entries.
326 * If the rule is INSTEAD, then the original query won't be executed at
327 * all, and so its rtable must be preserved so that the executor will do
328 * the correct permissions checks on it.
330 * RT entries that are not referenced in the completed jointree will be
331 * ignored by the planner, so they do not affect query semantics. But any
332 * permissions checks specified in them will be applied during executor
333 * startup (see ExecCheckRTEPerms()). This allows us to check that the
334 * caller has, say, insert-permission on a view, when the view is not
335 * semantically referenced at all in the resulting query.
337 * When a rule is not INSTEAD, the permissions checks done on its copied
338 * RT entries will be redundant with those done during execution of the
339 * original query, but we don't bother to treat that case differently.
341 * NOTE: because planner will destructively alter rtable, we must ensure
342 * that rule action's rtable is separate and shares no substructure with
343 * the main rtable. Hence do a deep copy here.
345 sub_action->rtable = list_concat((List *) copyObject(parsetree->rtable),
349 * Each rule action's jointree should be the main parsetree's jointree
350 * plus that rule's jointree, but usually *without* the original rtindex
351 * that we're replacing (if present, which it won't be for INSERT). Note
352 * that if the rule action refers to OLD, its jointree will add a
353 * reference to rt_index. If the rule action doesn't refer to OLD, but
354 * either the rule_qual or the user query quals do, then we need to keep
355 * the original rtindex in the jointree to provide data for the quals. We
356 * don't want the original rtindex to be joined twice, however, so avoid
357 * keeping it if the rule action mentions it.
359 * As above, the action's jointree must not share substructure with the
362 if (sub_action->commandType != CMD_UTILITY)
367 Assert(sub_action->jointree != NULL);
368 keeporig = (!rangeTableEntry_used((Node *) sub_action->jointree,
370 (rangeTableEntry_used(rule_qual, rt_index, 0) ||
371 rangeTableEntry_used(parsetree->jointree->quals, rt_index, 0));
372 newjointree = adjustJoinTreeList(parsetree, !keeporig, rt_index);
373 if (newjointree != NIL)
376 * If sub_action is a setop, manipulating its jointree will do no
377 * good at all, because the jointree is dummy. (Perhaps someday
378 * we could push the joining and quals down to the member
379 * statements of the setop?)
381 if (sub_action->setOperations != NULL)
383 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
384 errmsg("conditional UNION/INTERSECT/EXCEPT statements are not implemented")));
386 sub_action->jointree->fromlist =
387 list_concat(newjointree, sub_action->jointree->fromlist);
390 * There could have been some SubLinks in newjointree, in which
391 * case we'd better mark the sub_action correctly.
393 if (parsetree->hasSubLinks && !sub_action->hasSubLinks)
394 sub_action->hasSubLinks =
395 checkExprHasSubLink((Node *) newjointree);
400 * Event Qualification forces copying of parsetree and splitting into two
401 * queries one w/rule_qual, one w/NOT rule_qual. Also add user query qual
404 AddQual(sub_action, rule_qual);
406 AddQual(sub_action, parsetree->jointree->quals);
409 * Rewrite new.attribute w/ right hand side of target-list entry for
410 * appropriate field name in insert/update.
412 * KLUGE ALERT: since ResolveNew returns a mutated copy, we can't just
413 * apply it to sub_action; we have to remember to update the sublink
414 * inside rule_action, too.
416 if ((event == CMD_INSERT || event == CMD_UPDATE) &&
417 sub_action->commandType != CMD_UTILITY)
419 sub_action = (Query *) ResolveNew((Node *) sub_action,
424 parsetree->targetList,
428 *sub_action_ptr = sub_action;
430 rule_action = sub_action;
434 * If rule_action has a RETURNING clause, then either throw it away if the
435 * triggering query has no RETURNING clause, or rewrite it to emit what
436 * the triggering query's RETURNING clause asks for. Throw an error if
437 * more than one rule has a RETURNING clause.
439 if (!parsetree->returningList)
440 rule_action->returningList = NIL;
441 else if (rule_action->returningList)
445 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
446 errmsg("cannot have RETURNING lists in multiple rules")));
447 *returning_flag = true;
448 rule_action->returningList = (List *)
449 ResolveNew((Node *) parsetree->returningList,
450 parsetree->resultRelation,
452 rt_fetch(parsetree->resultRelation,
454 rule_action->returningList,
463 * Copy the query's jointree list, and optionally attempt to remove any
464 * occurrence of the given rt_index as a top-level join item (we do not look
465 * for it within join items; this is OK because we are only expecting to find
466 * it as an UPDATE or DELETE target relation, which will be at the top level
467 * of the join). Returns modified jointree list --- this is a separate copy
468 * sharing no nodes with the original.
471 adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
473 List *newjointree = copyObject(parsetree->jointree->fromlist);
478 foreach(l, newjointree)
480 RangeTblRef *rtr = lfirst(l);
482 if (IsA(rtr, RangeTblRef) &&
483 rtr->rtindex == rt_index)
485 newjointree = list_delete_ptr(newjointree, rtr);
488 * foreach is safe because we exit loop after list_delete...
499 * rewriteTargetList - rewrite INSERT/UPDATE targetlist into standard form
501 * This has the following responsibilities:
503 * 1. For an INSERT, add tlist entries to compute default values for any
504 * attributes that have defaults and are not assigned to in the given tlist.
505 * (We do not insert anything for default-less attributes, however. The
506 * planner will later insert NULLs for them, but there's no reason to slow
507 * down rewriter processing with extra tlist nodes.) Also, for both INSERT
508 * and UPDATE, replace explicit DEFAULT specifications with column default
511 * 2. Merge multiple entries for the same target attribute, or declare error
512 * if we can't. Multiple entries are only allowed for INSERT/UPDATE of
513 * portions of an array or record field, for example
514 * UPDATE table SET foo[2] = 42, foo[4] = 43;
515 * We can merge such operations into a single assignment op. Essentially,
516 * the expression we want to produce in this case is like
517 * foo = array_set(array_set(foo, 2, 42), 4, 43)
519 * 3. Sort the tlist into standard order: non-junk fields in order by resno,
520 * then junk fields (these in no particular order).
522 * We must do items 1 and 2 before firing rewrite rules, else rewritten
523 * references to NEW.foo will produce wrong or incomplete results. Item 3
524 * is not needed for rewriting, but will be needed by the planner, and we
525 * can do it essentially for free while handling items 1 and 2.
527 * If attrno_list isn't NULL, we return an additional output besides the
528 * rewritten targetlist: an integer list of the assigned-to attnums, in
529 * order of the original tlist's non-junk entries. This is needed for
530 * processing VALUES RTEs.
533 rewriteTargetList(Query *parsetree, Relation target_relation,
536 CmdType commandType = parsetree->commandType;
537 TargetEntry **new_tles;
538 List *new_tlist = NIL;
539 List *junk_tlist = NIL;
540 Form_pg_attribute att_tup;
546 if (attrno_list) /* initialize optional result list */
550 * We process the normal (non-junk) attributes by scanning the input tlist
551 * once and transferring TLEs into an array, then scanning the array to
552 * build an output tlist. This avoids O(N^2) behavior for large numbers
555 * Junk attributes are tossed into a separate list during the same tlist
556 * scan, then appended to the reconstructed tlist.
558 numattrs = RelationGetNumberOfAttributes(target_relation);
559 new_tles = (TargetEntry **) palloc0(numattrs * sizeof(TargetEntry *));
560 next_junk_attrno = numattrs + 1;
562 foreach(temp, parsetree->targetList)
564 TargetEntry *old_tle = (TargetEntry *) lfirst(temp);
566 if (!old_tle->resjunk)
568 /* Normal attr: stash it into new_tles[] */
569 attrno = old_tle->resno;
570 if (attrno < 1 || attrno > numattrs)
571 elog(ERROR, "bogus resno %d in targetlist", attrno);
572 att_tup = target_relation->rd_att->attrs[attrno - 1];
574 /* put attrno into attrno_list even if it's dropped */
576 *attrno_list = lappend_int(*attrno_list, attrno);
578 /* We can (and must) ignore deleted attributes */
579 if (att_tup->attisdropped)
582 /* Merge with any prior assignment to same attribute */
583 new_tles[attrno - 1] =
584 process_matched_tle(old_tle,
585 new_tles[attrno - 1],
586 NameStr(att_tup->attname));
591 * Copy all resjunk tlist entries to junk_tlist, and assign them
592 * resnos above the last real resno.
594 * Typical junk entries include ORDER BY or GROUP BY expressions
595 * (are these actually possible in an INSERT or UPDATE?), system
596 * attribute references, etc.
599 /* Get the resno right, but don't copy unnecessarily */
600 if (old_tle->resno != next_junk_attrno)
602 old_tle = flatCopyTargetEntry(old_tle);
603 old_tle->resno = next_junk_attrno;
605 junk_tlist = lappend(junk_tlist, old_tle);
610 for (attrno = 1; attrno <= numattrs; attrno++)
612 TargetEntry *new_tle = new_tles[attrno - 1];
614 att_tup = target_relation->rd_att->attrs[attrno - 1];
616 /* We can (and must) ignore deleted attributes */
617 if (att_tup->attisdropped)
621 * Handle the two cases where we need to insert a default expression:
622 * it's an INSERT and there's no tlist entry for the column, or the
623 * tlist entry is a DEFAULT placeholder node.
625 if ((new_tle == NULL && commandType == CMD_INSERT) ||
626 (new_tle && new_tle->expr && IsA(new_tle->expr, SetToDefault)))
630 new_expr = build_column_default(target_relation, attrno);
633 * If there is no default (ie, default is effectively NULL), we
634 * can omit the tlist entry in the INSERT case, since the planner
635 * can insert a NULL for itself, and there's no point in spending
636 * any more rewriter cycles on the entry. But in the UPDATE case
637 * we've got to explicitly set the column to NULL.
641 if (commandType == CMD_INSERT)
645 new_expr = (Node *) makeConst(att_tup->atttypid,
650 /* this is to catch a NOT NULL domain constraint */
651 new_expr = coerce_to_domain(new_expr,
654 COERCE_IMPLICIT_CAST,
661 new_tle = makeTargetEntry((Expr *) new_expr,
663 pstrdup(NameStr(att_tup->attname)),
668 new_tlist = lappend(new_tlist, new_tle);
673 parsetree->targetList = list_concat(new_tlist, junk_tlist);
678 * Convert a matched TLE from the original tlist into a correct new TLE.
680 * This routine detects and handles multiple assignments to the same target
681 * attribute. (The attribute name is needed only for error messages.)
684 process_matched_tle(TargetEntry *src_tle,
685 TargetEntry *prior_tle,
686 const char *attrName)
696 if (prior_tle == NULL)
699 * Normal case where this is the first assignment to the attribute.
705 * Multiple assignments to same attribute. Allow only if all are
706 * FieldStore or ArrayRef assignment operations. This is a bit
707 * tricky because what we may actually be looking at is a nest of
708 * such nodes; consider
709 * UPDATE tab SET col.fld1.subfld1 = x, col.fld2.subfld2 = y
710 * The two expressions produced by the parser will look like
711 * FieldStore(col, fld1, FieldStore(placeholder, subfld1, x))
712 * FieldStore(col, fld2, FieldStore(placeholder, subfld2, x))
713 * However, we can ignore the substructure and just consider the top
714 * FieldStore or ArrayRef from each assignment, because it works to
716 * FieldStore(FieldStore(col, fld1,
717 * FieldStore(placeholder, subfld1, x)),
718 * fld2, FieldStore(placeholder, subfld2, x))
719 * Note the leftmost expression goes on the inside so that the
720 * assignments appear to occur left-to-right.
722 * For FieldStore, instead of nesting we can generate a single
723 * FieldStore with multiple target fields. We must nest when
724 * ArrayRefs are involved though.
727 src_expr = (Node *) src_tle->expr;
728 prior_expr = (Node *) prior_tle->expr;
729 src_input = get_assignment_input(src_expr);
730 prior_input = get_assignment_input(prior_expr);
731 if (src_input == NULL ||
732 prior_input == NULL ||
733 exprType(src_expr) != exprType(prior_expr))
735 (errcode(ERRCODE_SYNTAX_ERROR),
736 errmsg("multiple assignments to same column \"%s\"",
740 * Prior TLE could be a nest of assignments if we do this more than once.
742 priorbottom = prior_input;
745 Node *newbottom = get_assignment_input(priorbottom);
747 if (newbottom == NULL)
748 break; /* found the original Var reference */
749 priorbottom = newbottom;
751 if (!equal(priorbottom, src_input))
753 (errcode(ERRCODE_SYNTAX_ERROR),
754 errmsg("multiple assignments to same column \"%s\"",
758 * Looks OK to nest 'em.
760 if (IsA(src_expr, FieldStore))
762 FieldStore *fstore = makeNode(FieldStore);
764 if (IsA(prior_expr, FieldStore))
766 /* combine the two */
767 memcpy(fstore, prior_expr, sizeof(FieldStore));
769 list_concat(list_copy(((FieldStore *) prior_expr)->newvals),
770 list_copy(((FieldStore *) src_expr)->newvals));
772 list_concat(list_copy(((FieldStore *) prior_expr)->fieldnums),
773 list_copy(((FieldStore *) src_expr)->fieldnums));
777 /* general case, just nest 'em */
778 memcpy(fstore, src_expr, sizeof(FieldStore));
779 fstore->arg = (Expr *) prior_expr;
781 newexpr = (Node *) fstore;
783 else if (IsA(src_expr, ArrayRef))
785 ArrayRef *aref = makeNode(ArrayRef);
787 memcpy(aref, src_expr, sizeof(ArrayRef));
788 aref->refexpr = (Expr *) prior_expr;
789 newexpr = (Node *) aref;
793 elog(ERROR, "can't happen");
797 result = flatCopyTargetEntry(src_tle);
798 result->expr = (Expr *) newexpr;
803 * If node is an assignment node, return its input; else return NULL
806 get_assignment_input(Node *node)
810 if (IsA(node, FieldStore))
812 FieldStore *fstore = (FieldStore *) node;
814 return (Node *) fstore->arg;
816 else if (IsA(node, ArrayRef))
818 ArrayRef *aref = (ArrayRef *) node;
820 if (aref->refassgnexpr == NULL)
822 return (Node *) aref->refexpr;
828 * Make an expression tree for the default value for a column.
830 * If there is no default, return a NULL instead.
833 build_column_default(Relation rel, int attrno)
835 TupleDesc rd_att = rel->rd_att;
836 Form_pg_attribute att_tup = rd_att->attrs[attrno - 1];
837 Oid atttype = att_tup->atttypid;
838 int32 atttypmod = att_tup->atttypmod;
843 * Scan to see if relation has a default for this column.
845 if (rd_att->constr && rd_att->constr->num_defval > 0)
847 AttrDefault *defval = rd_att->constr->defval;
848 int ndef = rd_att->constr->num_defval;
852 if (attrno == defval[ndef].adnum)
855 * Found it, convert string representation to node tree.
857 expr = stringToNode(defval[ndef].adbin);
866 * No per-column default, so look for a default for the type itself.
868 expr = get_typdefault(atttype);
872 return NULL; /* No default anywhere */
875 * Make sure the value is coerced to the target column type; this will
876 * generally be true already, but there seem to be some corner cases
877 * involving domain defaults where it might not be true. This should match
878 * the parser's processing of non-defaulted expressions --- see
879 * transformAssignedExpr().
881 exprtype = exprType(expr);
883 expr = coerce_to_target_type(NULL, /* no UNKNOWN params here */
887 COERCE_IMPLICIT_CAST);
890 (errcode(ERRCODE_DATATYPE_MISMATCH),
891 errmsg("column \"%s\" is of type %s"
892 " but default expression is of type %s",
893 NameStr(att_tup->attname),
894 format_type_be(atttype),
895 format_type_be(exprtype)),
896 errhint("You will need to rewrite or cast the expression.")));
902 /* Does VALUES RTE contain any SetToDefault items? */
904 searchForDefault(RangeTblEntry *rte)
908 foreach(lc, rte->values_lists)
910 List *sublist = (List *) lfirst(lc);
913 foreach(lc2, sublist)
915 Node *col = (Node *) lfirst(lc2);
917 if (IsA(col, SetToDefault))
925 * When processing INSERT ... VALUES with a VALUES RTE (ie, multiple VALUES
926 * lists), we have to replace any DEFAULT items in the VALUES lists with
927 * the appropriate default expressions. The other aspects of rewriteTargetList
928 * need be applied only to the query's targetlist proper.
930 * Note that we currently can't support subscripted or field assignment
931 * in the multi-VALUES case. The targetlist will contain simple Vars
932 * referencing the VALUES RTE, and therefore process_matched_tle() will
933 * reject any such attempt with "multiple assignments to same column".
936 rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation, List *attrnos)
942 * Rebuilding all the lists is a pretty expensive proposition in a big
943 * VALUES list, and it's a waste of time if there aren't any DEFAULT
944 * placeholders. So first scan to see if there are any.
946 if (!searchForDefault(rte))
947 return; /* nothing to do */
949 /* Check list lengths (we can assume all the VALUES sublists are alike) */
950 Assert(list_length(attrnos) == list_length(linitial(rte->values_lists)));
953 foreach(lc, rte->values_lists)
955 List *sublist = (List *) lfirst(lc);
960 forboth(lc2, sublist, lc3, attrnos)
962 Node *col = (Node *) lfirst(lc2);
963 int attrno = lfirst_int(lc3);
965 if (IsA(col, SetToDefault))
967 Form_pg_attribute att_tup;
970 att_tup = target_relation->rd_att->attrs[attrno - 1];
972 if (!att_tup->attisdropped)
973 new_expr = build_column_default(target_relation, attrno);
975 new_expr = NULL; /* force a NULL if dropped */
978 * If there is no default (ie, default is effectively NULL),
979 * we've got to explicitly set the column to NULL.
983 new_expr = (Node *) makeConst(att_tup->atttypid,
988 /* this is to catch a NOT NULL domain constraint */
989 new_expr = coerce_to_domain(new_expr,
992 COERCE_IMPLICIT_CAST,
996 newList = lappend(newList, new_expr);
999 newList = lappend(newList, col);
1001 newValues = lappend(newValues, newList);
1003 rte->values_lists = newValues;
1009 * match the list of locks and returns the matching rules
1012 matchLocks(CmdType event,
1013 RuleLock *rulelocks,
1017 List *matching_locks = NIL;
1021 if (rulelocks == NULL)
1024 if (parsetree->commandType != CMD_SELECT)
1026 if (parsetree->resultRelation != varno)
1030 nlocks = rulelocks->numLocks;
1032 for (i = 0; i < nlocks; i++)
1034 RewriteRule *oneLock = rulelocks->rules[i];
1036 if (oneLock->event == event)
1038 if (parsetree->commandType != CMD_SELECT ||
1039 (oneLock->attrno == -1 ?
1040 rangeTableEntry_used((Node *) parsetree, varno, 0) :
1041 attribute_used((Node *) parsetree,
1042 varno, oneLock->attrno, 0)))
1043 matching_locks = lappend(matching_locks, oneLock);
1047 return matching_locks;
1052 * ApplyRetrieveRule - expand an ON SELECT rule
1055 ApplyRetrieveRule(Query *parsetree,
1058 bool relation_level,
1067 if (list_length(rule->actions) != 1)
1068 elog(ERROR, "expected just one rule action");
1069 if (rule->qual != NULL)
1070 elog(ERROR, "cannot handle qualified ON SELECT rule");
1071 if (!relation_level)
1072 elog(ERROR, "cannot handle per-attribute ON SELECT rule");
1075 * Make a modifiable copy of the view query, and acquire needed locks on
1076 * the relations it mentions.
1078 rule_action = copyObject(linitial(rule->actions));
1080 AcquireRewriteLocks(rule_action);
1083 * Recursively expand any view references inside the view.
1085 rule_action = fireRIRrules(rule_action, activeRIRs);
1088 * VIEWs are really easy --- just plug the view query in as a subselect,
1089 * replacing the relation's original RTE.
1091 rte = rt_fetch(rt_index, parsetree->rtable);
1093 rte->rtekind = RTE_SUBQUERY;
1094 rte->relid = InvalidOid;
1095 rte->subquery = rule_action;
1096 rte->inh = false; /* must not be set for a subquery */
1099 * We move the view's permission check data down to its rangetable. The
1100 * checks will actually be done against the *OLD* entry therein.
1102 subrte = rt_fetch(PRS2_OLD_VARNO, rule_action->rtable);
1103 Assert(subrte->relid == relation->rd_id);
1104 subrte->requiredPerms = rte->requiredPerms;
1105 subrte->checkAsUser = rte->checkAsUser;
1107 rte->requiredPerms = 0; /* no permission check on subquery itself */
1108 rte->checkAsUser = InvalidOid;
1111 * FOR UPDATE/SHARE of view?
1113 if ((rc = get_rowmark(parsetree, rt_index)) != NULL)
1116 * Remove the view from the list of rels that will actually be marked
1117 * FOR UPDATE/SHARE by the executor. It will still be access-checked
1118 * for write access, though.
1120 parsetree->rowMarks = list_delete_ptr(parsetree->rowMarks, rc);
1123 * Set up the view's referenced tables as if FOR UPDATE/SHARE.
1125 markQueryForLocking(rule_action, rc->forUpdate,
1133 * Recursively mark all relations used by a view as FOR UPDATE/SHARE.
1135 * This may generate an invalid query, eg if some sub-query uses an
1136 * aggregate. We leave it to the planner to detect that.
1138 * NB: this must agree with the parser's transformLocking() routine.
1141 markQueryForLocking(Query *qry, bool forUpdate, bool noWait, bool skipOldNew)
1146 foreach(l, qry->rtable)
1148 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
1152 /* Ignore OLD and NEW entries if we are at top level of view */
1154 (rti == PRS2_OLD_VARNO || rti == PRS2_NEW_VARNO))
1157 if (rte->rtekind == RTE_RELATION)
1159 applyLockingClause(qry, rti, forUpdate, noWait);
1160 rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
1162 else if (rte->rtekind == RTE_SUBQUERY)
1164 /* FOR UPDATE/SHARE of subquery is propagated to subquery's rels */
1165 markQueryForLocking(rte->subquery, forUpdate, noWait, false);
1172 * fireRIRonSubLink -
1173 * Apply fireRIRrules() to each SubLink (subselect in expression) found
1174 * in the given tree.
1176 * NOTE: although this has the form of a walker, we cheat and modify the
1177 * SubLink nodes in-place. It is caller's responsibility to ensure that
1178 * no unwanted side-effects occur!
1180 * This is unlike most of the other routines that recurse into subselects,
1181 * because we must take control at the SubLink node in order to replace
1182 * the SubLink's subselect link with the possibly-rewritten subquery.
1185 fireRIRonSubLink(Node *node, List *activeRIRs)
1189 if (IsA(node, SubLink))
1191 SubLink *sub = (SubLink *) node;
1193 /* Do what we came for */
1194 sub->subselect = (Node *) fireRIRrules((Query *) sub->subselect,
1196 /* Fall through to process lefthand args of SubLink */
1200 * Do NOT recurse into Query nodes, because fireRIRrules already processed
1201 * subselects of subselects for us.
1203 return expression_tree_walker(node, fireRIRonSubLink,
1204 (void *) activeRIRs);
1210 * Apply all RIR rules on each rangetable entry in a query
1213 fireRIRrules(Query *parsetree, List *activeRIRs)
1218 * don't try to convert this into a foreach loop, because rtable list can
1219 * get changed each time through...
1222 while (rt_index < list_length(parsetree->rtable))
1233 rte = rt_fetch(rt_index, parsetree->rtable);
1236 * A subquery RTE can't have associated rules, so there's nothing to
1237 * do to this level of the query, but we must recurse into the
1238 * subquery to expand any rule references in it.
1240 if (rte->rtekind == RTE_SUBQUERY)
1242 rte->subquery = fireRIRrules(rte->subquery, activeRIRs);
1247 * Joins and other non-relation RTEs can be ignored completely.
1249 if (rte->rtekind != RTE_RELATION)
1253 * If the table is not referenced in the query, then we ignore it.
1254 * This prevents infinite expansion loop due to new rtable entries
1255 * inserted by expansion of a rule. A table is referenced if it is
1256 * part of the join set (a source table), or is referenced by any Var
1257 * nodes, or is the result table.
1259 if (rt_index != parsetree->resultRelation &&
1260 !rangeTableEntry_used((Node *) parsetree, rt_index, 0))
1264 * We can use NoLock here since either the parser or
1265 * AcquireRewriteLocks should have locked the rel already.
1267 rel = heap_open(rte->relid, NoLock);
1270 * Collect the RIR rules that we must apply
1272 rules = rel->rd_rules;
1275 heap_close(rel, NoLock);
1279 for (i = 0; i < rules->numLocks; i++)
1281 rule = rules->rules[i];
1282 if (rule->event != CMD_SELECT)
1285 if (rule->attrno > 0)
1287 /* per-attr rule; do we need it? */
1288 if (!attribute_used((Node *) parsetree, rt_index,
1293 locks = lappend(locks, rule);
1297 * If we found any, apply them --- but first check for recursion!
1303 if (list_member_oid(activeRIRs, RelationGetRelid(rel)))
1305 (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
1306 errmsg("infinite recursion detected in rules for relation \"%s\"",
1307 RelationGetRelationName(rel))));
1308 activeRIRs = lcons_oid(RelationGetRelid(rel), activeRIRs);
1314 parsetree = ApplyRetrieveRule(parsetree,
1322 activeRIRs = list_delete_first(activeRIRs);
1325 heap_close(rel, NoLock);
1329 * Recurse into sublink subqueries, too. But we already did the ones in
1332 if (parsetree->hasSubLinks)
1333 query_tree_walker(parsetree, fireRIRonSubLink, (void *) activeRIRs,
1334 QTW_IGNORE_RT_SUBQUERIES);
1341 * Modify the given query by adding 'AND rule_qual IS NOT TRUE' to its
1342 * qualification. This is used to generate suitable "else clauses" for
1343 * conditional INSTEAD rules. (Unfortunately we must use "x IS NOT TRUE",
1344 * not just "NOT x" which the planner is much smarter about, else we will
1345 * do the wrong thing when the qual evaluates to NULL.)
1347 * The rule_qual may contain references to OLD or NEW. OLD references are
1348 * replaced by references to the specified rt_index (the relation that the
1349 * rule applies to). NEW references are only possible for INSERT and UPDATE
1350 * queries on the relation itself, and so they should be replaced by copies
1351 * of the related entries in the query's own targetlist.
1354 CopyAndAddInvertedQual(Query *parsetree,
1359 /* Don't scribble on the passed qual (it's in the relcache!) */
1360 Node *new_qual = (Node *) copyObject(rule_qual);
1363 * In case there are subqueries in the qual, acquire necessary locks and
1364 * fix any deleted JOIN RTE entries. (This is somewhat redundant with
1365 * rewriteRuleAction, but not entirely ... consider restructuring so that
1366 * we only need to process the qual this way once.)
1368 (void) acquireLocksOnSubLinks(new_qual, NULL);
1370 /* Fix references to OLD */
1371 ChangeVarNodes(new_qual, PRS2_OLD_VARNO, rt_index, 0);
1372 /* Fix references to NEW */
1373 if (event == CMD_INSERT || event == CMD_UPDATE)
1374 new_qual = ResolveNew(new_qual,
1377 rt_fetch(rt_index, parsetree->rtable),
1378 parsetree->targetList,
1381 /* And attach the fixed qual */
1382 AddInvertedQual(parsetree, new_qual);
1390 * Iterate through rule locks applying rules.
1393 * parsetree - original query
1394 * rt_index - RT index of result relation in original query
1395 * event - type of rule event
1396 * locks - list of rules to fire
1398 * *instead_flag - set TRUE if any unqualified INSTEAD rule is found
1399 * (must be initialized to FALSE)
1400 * *returning_flag - set TRUE if we rewrite RETURNING clause in any rule
1401 * (must be initialized to FALSE)
1402 * *qual_product - filled with modified original query if any qualified
1403 * INSTEAD rule is found (must be initialized to NULL)
1405 * list of rule actions adjusted for use with this query
1407 * Qualified INSTEAD rules generate their action with the qualification
1408 * condition added. They also generate a modified version of the original
1409 * query with the negated qualification added, so that it will run only for
1410 * rows that the qualified action doesn't act on. (If there are multiple
1411 * qualified INSTEAD rules, we AND all the negated quals onto a single
1412 * modified original query.) We won't execute the original, unmodified
1413 * query if we find either qualified or unqualified INSTEAD rules. If
1414 * we find both, the modified original query is discarded too.
1417 fireRules(Query *parsetree,
1422 bool *returning_flag,
1423 Query **qual_product)
1425 List *results = NIL;
1430 RewriteRule *rule_lock = (RewriteRule *) lfirst(l);
1431 Node *event_qual = rule_lock->qual;
1432 List *actions = rule_lock->actions;
1436 /* Determine correct QuerySource value for actions */
1437 if (rule_lock->isInstead)
1439 if (event_qual != NULL)
1440 qsrc = QSRC_QUAL_INSTEAD_RULE;
1443 qsrc = QSRC_INSTEAD_RULE;
1444 *instead_flag = true; /* report unqualified INSTEAD */
1448 qsrc = QSRC_NON_INSTEAD_RULE;
1450 if (qsrc == QSRC_QUAL_INSTEAD_RULE)
1453 * If there are INSTEAD rules with qualifications, the original
1454 * query is still performed. But all the negated rule
1455 * qualifications of the INSTEAD rules are added so it does its
1456 * actions only in cases where the rule quals of all INSTEAD rules
1457 * are false. Think of it as the default action in a case. We save
1458 * this in *qual_product so RewriteQuery() can add it to the query
1459 * list after we mangled it up enough.
1461 * If we have already found an unqualified INSTEAD rule, then
1462 * *qual_product won't be used, so don't bother building it.
1466 if (*qual_product == NULL)
1467 *qual_product = copyObject(parsetree);
1468 *qual_product = CopyAndAddInvertedQual(*qual_product,
1475 /* Now process the rule's actions and add them to the result list */
1478 Query *rule_action = lfirst(r);
1480 if (rule_action->commandType == CMD_NOTHING)
1483 rule_action = rewriteRuleAction(parsetree, rule_action,
1484 event_qual, rt_index, event,
1487 rule_action->querySource = qsrc;
1488 rule_action->canSetTag = false; /* might change later */
1490 results = lappend(results, rule_action);
1500 * rewrites the query and apply the rules again on the queries rewritten
1502 * rewrite_events is a list of open query-rewrite actions, so we can detect
1503 * infinite recursion.
1506 RewriteQuery(Query *parsetree, List *rewrite_events)
1508 CmdType event = parsetree->commandType;
1509 bool instead = false;
1510 bool returning = false;
1511 Query *qual_product = NULL;
1512 List *rewritten = NIL;
1515 * If the statement is an update, insert or delete - fire rules on it.
1517 * SELECT rules are handled later when we have all the queries that should
1518 * get executed. Also, utilities aren't rewritten at all (do we still
1521 if (event != CMD_SELECT && event != CMD_UTILITY)
1523 int result_relation;
1524 RangeTblEntry *rt_entry;
1525 Relation rt_entry_relation;
1528 result_relation = parsetree->resultRelation;
1529 Assert(result_relation != 0);
1530 rt_entry = rt_fetch(result_relation, parsetree->rtable);
1531 Assert(rt_entry->rtekind == RTE_RELATION);
1534 * We can use NoLock here since either the parser or
1535 * AcquireRewriteLocks should have locked the rel already.
1537 rt_entry_relation = heap_open(rt_entry->relid, NoLock);
1540 * If it's an INSERT or UPDATE, rewrite the targetlist into standard
1541 * form. This will be needed by the planner anyway, and doing it now
1542 * ensures that any references to NEW.field will behave sanely.
1544 if (event == CMD_UPDATE)
1545 rewriteTargetList(parsetree, rt_entry_relation, NULL);
1546 else if (event == CMD_INSERT)
1548 RangeTblEntry *values_rte = NULL;
1551 * If it's an INSERT ... VALUES (...), (...), ... there will be a
1552 * single RTE for the VALUES targetlists.
1554 if (list_length(parsetree->jointree->fromlist) == 1)
1556 RangeTblRef *rtr = (RangeTblRef *) linitial(parsetree->jointree->fromlist);
1558 if (IsA(rtr, RangeTblRef))
1560 RangeTblEntry *rte = rt_fetch(rtr->rtindex,
1563 if (rte->rtekind == RTE_VALUES)
1572 /* Process the main targetlist ... */
1573 rewriteTargetList(parsetree, rt_entry_relation, &attrnos);
1574 /* ... and the VALUES expression lists */
1575 rewriteValuesRTE(values_rte, rt_entry_relation, attrnos);
1579 /* Process just the main targetlist */
1580 rewriteTargetList(parsetree, rt_entry_relation, NULL);
1585 * Collect and apply the appropriate rules.
1587 locks = matchLocks(event, rt_entry_relation->rd_rules,
1588 result_relation, parsetree);
1592 List *product_queries;
1594 product_queries = fireRules(parsetree,
1603 * If we got any product queries, recursively rewrite them --- but
1604 * first check for recursion!
1606 if (product_queries != NIL)
1611 foreach(n, rewrite_events)
1613 rev = (rewrite_event *) lfirst(n);
1614 if (rev->relation == RelationGetRelid(rt_entry_relation) &&
1615 rev->event == event)
1617 (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
1618 errmsg("infinite recursion detected in rules for relation \"%s\"",
1619 RelationGetRelationName(rt_entry_relation))));
1622 rev = (rewrite_event *) palloc(sizeof(rewrite_event));
1623 rev->relation = RelationGetRelid(rt_entry_relation);
1625 rewrite_events = lcons(rev, rewrite_events);
1627 foreach(n, product_queries)
1629 Query *pt = (Query *) lfirst(n);
1632 newstuff = RewriteQuery(pt, rewrite_events);
1633 rewritten = list_concat(rewritten, newstuff);
1636 rewrite_events = list_delete_first(rewrite_events);
1641 * If there is an INSTEAD, and the original query has a RETURNING, we
1642 * have to have found a RETURNING in the rule(s), else fail. (Because
1643 * DefineQueryRewrite only allows RETURNING in unconditional INSTEAD
1644 * rules, there's no need to worry whether the substituted RETURNING
1645 * will actually be executed --- it must be.)
1647 if ((instead || qual_product != NULL) &&
1648 parsetree->returningList &&
1655 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1656 errmsg("cannot INSERT RETURNING on relation \"%s\"",
1657 RelationGetRelationName(rt_entry_relation)),
1658 errhint("You need an unconditional ON INSERT DO INSTEAD rule with a RETURNING clause.")));
1662 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1663 errmsg("cannot UPDATE RETURNING on relation \"%s\"",
1664 RelationGetRelationName(rt_entry_relation)),
1665 errhint("You need an unconditional ON UPDATE DO INSTEAD rule with a RETURNING clause.")));
1669 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1670 errmsg("cannot DELETE RETURNING on relation \"%s\"",
1671 RelationGetRelationName(rt_entry_relation)),
1672 errhint("You need an unconditional ON DELETE DO INSTEAD rule with a RETURNING clause.")));
1675 elog(ERROR, "unrecognized commandType: %d",
1681 heap_close(rt_entry_relation, NoLock);
1685 * For INSERTs, the original query is done first; for UPDATE/DELETE, it is
1686 * done last. This is needed because update and delete rule actions might
1687 * not do anything if they are invoked after the update or delete is
1688 * performed. The command counter increment between the query executions
1689 * makes the deleted (and maybe the updated) tuples disappear so the scans
1690 * for them in the rule actions cannot find them.
1692 * If we found any unqualified INSTEAD, the original query is not done at
1693 * all, in any form. Otherwise, we add the modified form if qualified
1694 * INSTEADs were found, else the unmodified form.
1698 if (parsetree->commandType == CMD_INSERT)
1700 if (qual_product != NULL)
1701 rewritten = lcons(qual_product, rewritten);
1703 rewritten = lcons(parsetree, rewritten);
1707 if (qual_product != NULL)
1708 rewritten = lappend(rewritten, qual_product);
1710 rewritten = lappend(rewritten, parsetree);
1720 * Primary entry point to the query rewriter.
1721 * Rewrite one query via query rewrite system, possibly returning 0
1724 * NOTE: the parsetree must either have come straight from the parser,
1725 * or have been scanned by AcquireRewriteLocks to acquire suitable locks.
1728 QueryRewrite(Query *parsetree)
1731 List *results = NIL;
1733 CmdType origCmdType;
1734 bool foundOriginalQuery;
1740 * Apply all non-SELECT rules possibly getting 0 or many queries
1742 querylist = RewriteQuery(parsetree, NIL);
1747 * Apply all the RIR rules on each query
1749 foreach(l, querylist)
1751 Query *query = (Query *) lfirst(l);
1753 query = fireRIRrules(query, NIL);
1756 * If the query target was rewritten as a view, complain.
1758 if (query->resultRelation)
1760 RangeTblEntry *rte = rt_fetch(query->resultRelation,
1763 if (rte->rtekind == RTE_SUBQUERY)
1765 switch (query->commandType)
1769 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1770 errmsg("cannot insert into a view"),
1771 errhint("You need an unconditional ON INSERT DO INSTEAD rule.")));
1775 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1776 errmsg("cannot update a view"),
1777 errhint("You need an unconditional ON UPDATE DO INSTEAD rule.")));
1781 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1782 errmsg("cannot delete from a view"),
1783 errhint("You need an unconditional ON DELETE DO INSTEAD rule.")));
1786 elog(ERROR, "unrecognized commandType: %d",
1787 (int) query->commandType);
1793 results = lappend(results, query);
1799 * Determine which, if any, of the resulting queries is supposed to set
1800 * the command-result tag; and update the canSetTag fields accordingly.
1802 * If the original query is still in the list, it sets the command tag.
1803 * Otherwise, the last INSTEAD query of the same kind as the original is
1804 * allowed to set the tag. (Note these rules can leave us with no query
1805 * setting the tag. The tcop code has to cope with this by setting up a
1806 * default tag based on the original un-rewritten query.)
1808 * The Asserts verify that at most one query in the result list is marked
1809 * canSetTag. If we aren't checking asserts, we can fall out of the loop
1810 * as soon as we find the original query.
1812 origCmdType = parsetree->commandType;
1813 foundOriginalQuery = false;
1818 Query *query = (Query *) lfirst(l);
1820 if (query->querySource == QSRC_ORIGINAL)
1822 Assert(query->canSetTag);
1823 Assert(!foundOriginalQuery);
1824 foundOriginalQuery = true;
1825 #ifndef USE_ASSERT_CHECKING
1831 Assert(!query->canSetTag);
1832 if (query->commandType == origCmdType &&
1833 (query->querySource == QSRC_INSTEAD_RULE ||
1834 query->querySource == QSRC_QUAL_INSTEAD_RULE))
1835 lastInstead = query;
1839 if (!foundOriginalQuery && lastInstead != NULL)
1840 lastInstead->canSetTag = true;