granicus.if.org Git - postgresql/blob - src/backend/rewrite/rewriteHandler.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * rewriteHandler.c
   4  *              Primary module of query rewriter.
   5  *
   6  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  * IDENTIFICATION
  10  *        $PostgreSQL: pgsql/src/backend/rewrite/rewriteHandler.c,v 1.158 2005/10/15 02:49:24 momjian Exp $
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #include "postgres.h"
  15
  16 #include "access/heapam.h"
  17 #include "catalog/pg_operator.h"
  18 #include "catalog/pg_type.h"
  19 #include "miscadmin.h"
  20 #include "nodes/makefuncs.h"
  21 #include "optimizer/clauses.h"
  22 #include "optimizer/prep.h"
  23 #include "optimizer/var.h"
  24 #include "parser/analyze.h"
  25 #include "parser/parse_coerce.h"
  26 #include "parser/parse_expr.h"
  27 #include "parser/parse_oper.h"
  28 #include "parser/parse_type.h"
  29 #include "parser/parsetree.h"
  30 #include "rewrite/rewriteHandler.h"
  31 #include "rewrite/rewriteManip.h"
  32 #include "utils/builtins.h"
  33 #include "utils/lsyscache.h"
  34
  35
  36 /* We use a list of these to detect recursion in RewriteQuery */
  37 typedef struct rewrite_event
  38 {
  39         Oid                     relation;               /* OID of relation having rules */
  40         CmdType         event;                  /* type of rule being fired */
  41 } rewrite_event;
  42
  43 static bool acquireLocksOnSubLinks(Node *node, void *context);
  44 static Query *rewriteRuleAction(Query *parsetree,
  45                                   Query *rule_action,
  46                                   Node *rule_qual,
  47                                   int rt_index,
  48                                   CmdType event);
  49 static List *adjustJoinTreeList(Query *parsetree, bool removert, int rt_index);
  50 static void rewriteTargetList(Query *parsetree, Relation target_relation);
  51 static TargetEntry *process_matched_tle(TargetEntry *src_tle,
  52                                         TargetEntry *prior_tle,
  53                                         const char *attrName);
  54 static Node *get_assignment_input(Node *node);
  55 static void markQueryForLocking(Query *qry, bool forUpdate, bool noWait,
  56                                         bool skipOldNew);
  57 static List *matchLocks(CmdType event, RuleLock *rulelocks,
  58                    int varno, Query *parsetree);
  59 static Query *fireRIRrules(Query *parsetree, List *activeRIRs);
  60
  61
  62 /*
  63  * AcquireRewriteLocks -
  64  *        Acquire suitable locks on all the relations mentioned in the Query.
  65  *        These locks will ensure that the relation schemas don't change under us
  66  *        while we are rewriting and planning the query.
  67  *
  68  * A secondary purpose of this routine is to fix up JOIN RTE references to
  69  * dropped columns (see details below).  Because the RTEs are modified in
  70  * place, it is generally appropriate for the caller of this routine to have
  71  * first done a copyObject() to make a writable copy of the querytree in the
  72  * current memory context.
  73  *
  74  * This processing can, and for efficiency's sake should, be skipped when the
  75  * querytree has just been built by the parser: parse analysis already got
  76  * all the same locks we'd get here, and the parser will have omitted dropped
  77  * columns from JOINs to begin with.  But we must do this whenever we are
  78  * dealing with a querytree produced earlier than the current command.
  79  *
  80  * About JOINs and dropped columns: although the parser never includes an
  81  * already-dropped column in a JOIN RTE's alias var list, it is possible for
  82  * such a list in a stored rule to include references to dropped columns.
  83  * (If the column is not explicitly referenced anywhere else in the query,
  84  * the dependency mechanism won't consider it used by the rule and so won't
  85  * prevent the column drop.)  To support get_rte_attribute_is_dropped(),
  86  * we replace join alias vars that reference dropped columns with NULL Const
  87  * nodes.
  88  *
  89  * (In PostgreSQL 8.0, we did not do this processing but instead had
  90  * get_rte_attribute_is_dropped() recurse to detect dropped columns in joins.
  91  * That approach had horrible performance unfortunately; in particular
  92  * construction of a nested join was O(N^2) in the nesting depth.)
  93  */
  94 void
  95 AcquireRewriteLocks(Query *parsetree)
  96 {
  97         ListCell   *l;
  98         int                     rt_index;
  99
 100         /*
 101          * First, process RTEs of the current query level.
 102          */
 103         rt_index = 0;
 104         foreach(l, parsetree->rtable)
 105         {
 106                 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 107                 Relation        rel;
 108                 LOCKMODE        lockmode;
 109                 List       *newaliasvars;
 110                 Index           curinputvarno;
 111                 RangeTblEntry *curinputrte;
 112                 ListCell   *ll;
 113
 114                 ++rt_index;
 115                 switch (rte->rtekind)
 116                 {
 117                         case RTE_RELATION:
 118
 119                                 /*
 120                                  * Grab the appropriate lock type for the relation, and do not
 121                                  * release it until end of transaction. This protects the
 122                                  * rewriter and planner against schema changes mid-query.
 123                                  *
 124                                  * If the relation is the query's result relation, then we need
 125                                  * RowExclusiveLock.  Otherwise, check to see if the relation
 126                                  * is accessed FOR UPDATE/SHARE or not.  We can't just grab
 127                                  * AccessShareLock because then the executor would be trying
 128                                  * to upgrade the lock, leading to possible deadlocks.
 129                                  */
 130                                 if (rt_index == parsetree->resultRelation)
 131                                         lockmode = RowExclusiveLock;
 132                                 else if (list_member_int(parsetree->rowMarks, rt_index))
 133                                         lockmode = RowShareLock;
 134                                 else
 135                                         lockmode = AccessShareLock;
 136
 137                                 rel = heap_open(rte->relid, lockmode);
 138                                 heap_close(rel, NoLock);
 139                                 break;
 140
 141                         case RTE_JOIN:
 142
 143                                 /*
 144                                  * Scan the join's alias var list to see if any columns have
 145                                  * been dropped, and if so replace those Vars with NULL
 146                                  * Consts.
 147                                  *
 148                                  * Since a join has only two inputs, we can expect to see
 149                                  * multiple references to the same input RTE; optimize away
 150                                  * multiple fetches.
 151                                  */
 152                                 newaliasvars = NIL;
 153                                 curinputvarno = 0;
 154                                 curinputrte = NULL;
 155                                 foreach(ll, rte->joinaliasvars)
 156                                 {
 157                                         Var                *aliasvar = (Var *) lfirst(ll);
 158
 159                                         /*
 160                                          * If the list item isn't a simple Var, then it must
 161                                          * represent a merged column, ie a USING column, and so it
 162                                          * couldn't possibly be dropped, since it's referenced in
 163                                          * the join clause.  (Conceivably it could also be a NULL
 164                                          * constant already?  But that's OK too.)
 165                                          */
 166                                         if (IsA(aliasvar, Var))
 167                                         {
 168                                                 /*
 169                                                  * The elements of an alias list have to refer to
 170                                                  * earlier RTEs of the same rtable, because that's the
 171                                                  * order the planner builds things in.  So we already
 172                                                  * processed the referenced RTE, and so it's safe to
 173                                                  * use get_rte_attribute_is_dropped on it. (This might
 174                                                  * not hold after rewriting or planning, but it's OK
 175                                                  * to assume here.)
 176                                                  */
 177                                                 Assert(aliasvar->varlevelsup == 0);
 178                                                 if (aliasvar->varno != curinputvarno)
 179                                                 {
 180                                                         curinputvarno = aliasvar->varno;
 181                                                         if (curinputvarno >= rt_index)
 182                                                                 elog(ERROR, "unexpected varno %d in JOIN RTE %d",
 183                                                                          curinputvarno, rt_index);
 184                                                         curinputrte = rt_fetch(curinputvarno,
 185                                                                                                    parsetree->rtable);
 186                                                 }
 187                                                 if (get_rte_attribute_is_dropped(curinputrte,
 188                                                                                                                  aliasvar->varattno))
 189                                                 {
 190                                                         /*
 191                                                          * can't use vartype here, since that might be a
 192                                                          * now-dropped type OID, but it doesn't really
 193                                                          * matter what type the Const claims to be.
 194                                                          */
 195                                                         aliasvar = (Var *) makeNullConst(INT4OID);
 196                                                 }
 197                                         }
 198                                         newaliasvars = lappend(newaliasvars, aliasvar);
 199                                 }
 200                                 rte->joinaliasvars = newaliasvars;
 201                                 break;
 202
 203                         case RTE_SUBQUERY:
 204
 205                                 /*
 206                                  * The subquery RTE itself is all right, but we have to
 207                                  * recurse to process the represented subquery.
 208                                  */
 209                                 AcquireRewriteLocks(rte->subquery);
 210                                 break;
 211
 212                         default:
 213                                 /* ignore other types of RTEs */
 214                                 break;
 215                 }
 216         }
 217
 218         /*
 219          * Recurse into sublink subqueries, too.  But we already did the ones in
 220          * the rtable.
 221          */
 222         if (parsetree->hasSubLinks)
 223                 query_tree_walker(parsetree, acquireLocksOnSubLinks, NULL,
 224                                                   QTW_IGNORE_RT_SUBQUERIES);
 225 }
 226
 227 /*
 228  * Walker to find sublink subqueries for AcquireRewriteLocks
 229  */
 230 static bool
 231 acquireLocksOnSubLinks(Node *node, void *context)
 232 {
 233         if (node == NULL)
 234                 return false;
 235         if (IsA(node, SubLink))
 236         {
 237                 SubLink    *sub = (SubLink *) node;
 238
 239                 /* Do what we came for */
 240                 AcquireRewriteLocks((Query *) sub->subselect);
 241                 /* Fall through to process lefthand args of SubLink */
 242         }
 243
 244         /*
 245          * Do NOT recurse into Query nodes, because AcquireRewriteLocks already
 246          * processed subselects of subselects for us.
 247          */
 248         return expression_tree_walker(node, acquireLocksOnSubLinks, context);
 249 }
 250
 251
 252 /*
 253  * rewriteRuleAction -
 254  *        Rewrite the rule action with appropriate qualifiers (taken from
 255  *        the triggering query).
 256  */
 257 static Query *
 258 rewriteRuleAction(Query *parsetree,
 259                                   Query *rule_action,
 260                                   Node *rule_qual,
 261                                   int rt_index,
 262                                   CmdType event)
 263 {
 264         int                     current_varno,
 265                                 new_varno;
 266         int                     rt_length;
 267         Query      *sub_action;
 268         Query     **sub_action_ptr;
 269
 270         /*
 271          * Make modifiable copies of rule action and qual (what we're passed are
 272          * the stored versions in the relcache; don't touch 'em!).
 273          */
 274         rule_action = (Query *) copyObject(rule_action);
 275         rule_qual = (Node *) copyObject(rule_qual);
 276
 277         /*
 278          * Acquire necessary locks and fix any deleted JOIN RTE entries.
 279          */
 280         AcquireRewriteLocks(rule_action);
 281         (void) acquireLocksOnSubLinks(rule_qual, NULL);
 282
 283         current_varno = rt_index;
 284         rt_length = list_length(parsetree->rtable);
 285         new_varno = PRS2_NEW_VARNO + rt_length;
 286
 287         /*
 288          * Adjust rule action and qual to offset its varnos, so that we can merge
 289          * its rtable with the main parsetree's rtable.
 290          *
 291          * If the rule action is an INSERT...SELECT, the OLD/NEW rtable entries will
 292          * be in the SELECT part, and we have to modify that rather than the
 293          * top-level INSERT (kluge!).
 294          */
 295         sub_action = getInsertSelectQuery(rule_action, &sub_action_ptr);
 296
 297         OffsetVarNodes((Node *) sub_action, rt_length, 0);
 298         OffsetVarNodes(rule_qual, rt_length, 0);
 299         /* but references to *OLD* should point at original rt_index */
 300         ChangeVarNodes((Node *) sub_action,
 301                                    PRS2_OLD_VARNO + rt_length, rt_index, 0);
 302         ChangeVarNodes(rule_qual,
 303                                    PRS2_OLD_VARNO + rt_length, rt_index, 0);
 304
 305         /*
 306          * Generate expanded rtable consisting of main parsetree's rtable plus
 307          * rule action's rtable; this becomes the complete rtable for the rule
 308          * action.      Some of the entries may be unused after we finish rewriting,
 309          * but we leave them all in place for two reasons:
 310          *
 311          * We'd have a much harder job to adjust the query's varnos if we selectively
 312          * removed RT entries.
 313          *
 314          * If the rule is INSTEAD, then the original query won't be executed at all,
 315          * and so its rtable must be preserved so that the executor will do the
 316          * correct permissions checks on it.
 317          *
 318          * RT entries that are not referenced in the completed jointree will be
 319          * ignored by the planner, so they do not affect query semantics.  But any
 320          * permissions checks specified in them will be applied during executor
 321          * startup (see ExecCheckRTEPerms()).  This allows us to check that the
 322          * caller has, say, insert-permission on a view, when the view is not
 323          * semantically referenced at all in the resulting query.
 324          *
 325          * When a rule is not INSTEAD, the permissions checks done on its copied RT
 326          * entries will be redundant with those done during execution of the
 327          * original query, but we don't bother to treat that case differently.
 328          *
 329          * NOTE: because planner will destructively alter rtable, we must ensure that
 330          * rule action's rtable is separate and shares no substructure with the
 331          * main rtable.  Hence do a deep copy here.
 332          */
 333         sub_action->rtable = list_concat((List *) copyObject(parsetree->rtable),
 334                                                                          sub_action->rtable);
 335
 336         /*
 337          * Each rule action's jointree should be the main parsetree's jointree
 338          * plus that rule's jointree, but usually *without* the original rtindex
 339          * that we're replacing (if present, which it won't be for INSERT). Note
 340          * that if the rule action refers to OLD, its jointree will add a
 341          * reference to rt_index.  If the rule action doesn't refer to OLD, but
 342          * either the rule_qual or the user query quals do, then we need to keep
 343          * the original rtindex in the jointree to provide data for the quals.  We
 344          * don't want the original rtindex to be joined twice, however, so avoid
 345          * keeping it if the rule action mentions it.
 346          *
 347          * As above, the action's jointree must not share substructure with the main
 348          * parsetree's.
 349          */
 350         if (sub_action->commandType != CMD_UTILITY)
 351         {
 352                 bool            keeporig;
 353                 List       *newjointree;
 354
 355                 Assert(sub_action->jointree != NULL);
 356                 keeporig = (!rangeTableEntry_used((Node *) sub_action->jointree,
 357                                                                                   rt_index, 0)) &&
 358                         (rangeTableEntry_used(rule_qual, rt_index, 0) ||
 359                          rangeTableEntry_used(parsetree->jointree->quals, rt_index, 0));
 360                 newjointree = adjustJoinTreeList(parsetree, !keeporig, rt_index);
 361                 if (newjointree != NIL)
 362                 {
 363                         /*
 364                          * If sub_action is a setop, manipulating its jointree will do no
 365                          * good at all, because the jointree is dummy.  (Perhaps someday
 366                          * we could push the joining and quals down to the member
 367                          * statements of the setop?)
 368                          */
 369                         if (sub_action->setOperations != NULL)
 370                                 ereport(ERROR,
 371                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 372                                                  errmsg("conditional UNION/INTERSECT/EXCEPT statements are not implemented")));
 373
 374                         sub_action->jointree->fromlist =
 375                                 list_concat(newjointree, sub_action->jointree->fromlist);
 376                 }
 377         }
 378
 379         /*
 380          * Event Qualification forces copying of parsetree and splitting into two
 381          * queries one w/rule_qual, one w/NOT rule_qual. Also add user query qual
 382          * onto rule action
 383          */
 384         AddQual(sub_action, rule_qual);
 385
 386         AddQual(sub_action, parsetree->jointree->quals);
 387
 388         /*
 389          * Rewrite new.attribute w/ right hand side of target-list entry for
 390          * appropriate field name in insert/update.
 391          *
 392          * KLUGE ALERT: since ResolveNew returns a mutated copy, we can't just apply
 393          * it to sub_action; we have to remember to update the sublink inside
 394          * rule_action, too.
 395          */
 396         if ((event == CMD_INSERT || event == CMD_UPDATE) &&
 397                 sub_action->commandType != CMD_UTILITY)
 398         {
 399                 sub_action = (Query *) ResolveNew((Node *) sub_action,
 400                                                                                   new_varno,
 401                                                                                   0,
 402                                                                                   rt_fetch(new_varno,
 403                                                                                                    sub_action->rtable),
 404                                                                                   parsetree->targetList,
 405                                                                                   event,
 406                                                                                   current_varno);
 407                 if (sub_action_ptr)
 408                         *sub_action_ptr = sub_action;
 409                 else
 410                         rule_action = sub_action;
 411         }
 412
 413         return rule_action;
 414 }
 415
 416 /*
 417  * Copy the query's jointree list, and optionally attempt to remove any
 418  * occurrence of the given rt_index as a top-level join item (we do not look
 419  * for it within join items; this is OK because we are only expecting to find
 420  * it as an UPDATE or DELETE target relation, which will be at the top level
 421  * of the join).  Returns modified jointree list --- this is a separate copy
 422  * sharing no nodes with the original.
 423  */
 424 static List *
 425 adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
 426 {
 427         List       *newjointree = copyObject(parsetree->jointree->fromlist);
 428         ListCell   *l;
 429
 430         if (removert)
 431         {
 432                 foreach(l, newjointree)
 433                 {
 434                         RangeTblRef *rtr = lfirst(l);
 435
 436                         if (IsA(rtr, RangeTblRef) &&
 437                                 rtr->rtindex == rt_index)
 438                         {
 439                                 newjointree = list_delete_ptr(newjointree, rtr);
 440
 441                                 /*
 442                                  * foreach is safe because we exit loop after list_delete...
 443                                  */
 444                                 break;
 445                         }
 446                 }
 447         }
 448         return newjointree;
 449 }
 450
 451
 452 /*
 453  * rewriteTargetList - rewrite INSERT/UPDATE targetlist into standard form
 454  *
 455  * This has the following responsibilities:
 456  *
 457  * 1. For an INSERT, add tlist entries to compute default values for any
 458  * attributes that have defaults and are not assigned to in the given tlist.
 459  * (We do not insert anything for default-less attributes, however.  The
 460  * planner will later insert NULLs for them, but there's no reason to slow
 461  * down rewriter processing with extra tlist nodes.)  Also, for both INSERT
 462  * and UPDATE, replace explicit DEFAULT specifications with column default
 463  * expressions.
 464  *
 465  * 2. Merge multiple entries for the same target attribute, or declare error
 466  * if we can't.  Multiple entries are only allowed for INSERT/UPDATE of
 467  * portions of an array or record field, for example
 468  *                      UPDATE table SET foo[2] = 42, foo[4] = 43;
 469  * We can merge such operations into a single assignment op.  Essentially,
 470  * the expression we want to produce in this case is like
 471  *              foo = array_set(array_set(foo, 2, 42), 4, 43)
 472  *
 473  * 3. Sort the tlist into standard order: non-junk fields in order by resno,
 474  * then junk fields (these in no particular order).
 475  *
 476  * We must do items 1 and 2 before firing rewrite rules, else rewritten
 477  * references to NEW.foo will produce wrong or incomplete results.      Item 3
 478  * is not needed for rewriting, but will be needed by the planner, and we
 479  * can do it essentially for free while handling items 1 and 2.
 480  */
 481 static void
 482 rewriteTargetList(Query *parsetree, Relation target_relation)
 483 {
 484         CmdType         commandType = parsetree->commandType;
 485         TargetEntry **new_tles;
 486         List       *new_tlist = NIL;
 487         List       *junk_tlist = NIL;
 488         Form_pg_attribute att_tup;
 489         int                     attrno,
 490                                 next_junk_attrno,
 491                                 numattrs;
 492         ListCell   *temp;
 493
 494         /*
 495          * We process the normal (non-junk) attributes by scanning the input tlist
 496          * once and transferring TLEs into an array, then scanning the array to
 497          * build an output tlist.  This avoids O(N^2) behavior for large numbers
 498          * of attributes.
 499          *
 500          * Junk attributes are tossed into a separate list during the same tlist
 501          * scan, then appended to the reconstructed tlist.
 502          */
 503         numattrs = RelationGetNumberOfAttributes(target_relation);
 504         new_tles = (TargetEntry **) palloc0(numattrs * sizeof(TargetEntry *));
 505         next_junk_attrno = numattrs + 1;
 506
 507         foreach(temp, parsetree->targetList)
 508         {
 509                 TargetEntry *old_tle = (TargetEntry *) lfirst(temp);
 510
 511                 if (!old_tle->resjunk)
 512                 {
 513                         /* Normal attr: stash it into new_tles[] */
 514                         attrno = old_tle->resno;
 515                         if (attrno < 1 || attrno > numattrs)
 516                                 elog(ERROR, "bogus resno %d in targetlist", attrno);
 517                         att_tup = target_relation->rd_att->attrs[attrno - 1];
 518
 519                         /* We can (and must) ignore deleted attributes */
 520                         if (att_tup->attisdropped)
 521                                 continue;
 522
 523                         /* Merge with any prior assignment to same attribute */
 524                         new_tles[attrno - 1] =
 525                                 process_matched_tle(old_tle,
 526                                                                         new_tles[attrno - 1],
 527                                                                         NameStr(att_tup->attname));
 528                 }
 529                 else
 530                 {
 531                         /*
 532                          * Copy all resjunk tlist entries to junk_tlist, and assign them
 533                          * resnos above the last real resno.
 534                          *
 535                          * Typical junk entries include ORDER BY or GROUP BY expressions (are
 536                          * these actually possible in an INSERT or UPDATE?), system
 537                          * attribute references, etc.
 538                          */
 539
 540                         /* Get the resno right, but don't copy unnecessarily */
 541                         if (old_tle->resno != next_junk_attrno)
 542                         {
 543                                 old_tle = flatCopyTargetEntry(old_tle);
 544                                 old_tle->resno = next_junk_attrno;
 545                         }
 546                         junk_tlist = lappend(junk_tlist, old_tle);
 547                         next_junk_attrno++;
 548                 }
 549         }
 550
 551         for (attrno = 1; attrno <= numattrs; attrno++)
 552         {
 553                 TargetEntry *new_tle = new_tles[attrno - 1];
 554
 555                 att_tup = target_relation->rd_att->attrs[attrno - 1];
 556
 557                 /* We can (and must) ignore deleted attributes */
 558                 if (att_tup->attisdropped)
 559                         continue;
 560
 561                 /*
 562                  * Handle the two cases where we need to insert a default expression:
 563                  * it's an INSERT and there's no tlist entry for the column, or the
 564                  * tlist entry is a DEFAULT placeholder node.
 565                  */
 566                 if ((new_tle == NULL && commandType == CMD_INSERT) ||
 567                         (new_tle && new_tle->expr && IsA(new_tle->expr, SetToDefault)))
 568                 {
 569                         Node       *new_expr;
 570
 571                         new_expr = build_column_default(target_relation, attrno);
 572
 573                         /*
 574                          * If there is no default (ie, default is effectively NULL), we
 575                          * can omit the tlist entry in the INSERT case, since the planner
 576                          * can insert a NULL for itself, and there's no point in spending
 577                          * any more rewriter cycles on the entry.  But in the UPDATE case
 578                          * we've got to explicitly set the column to NULL.
 579                          */
 580                         if (!new_expr)
 581                         {
 582                                 if (commandType == CMD_INSERT)
 583                                         new_tle = NULL;
 584                                 else
 585                                 {
 586                                         new_expr = (Node *) makeConst(att_tup->atttypid,
 587                                                                                                   att_tup->attlen,
 588                                                                                                   (Datum) 0,
 589                                                                                                   true, /* isnull */
 590                                                                                                   att_tup->attbyval);
 591                                         /* this is to catch a NOT NULL domain constraint */
 592                                         new_expr = coerce_to_domain(new_expr,
 593                                                                                                 InvalidOid,
 594                                                                                                 att_tup->atttypid,
 595                                                                                                 COERCE_IMPLICIT_CAST,
 596                                                                                                 false,
 597                                                                                                 false);
 598                                 }
 599                         }
 600
 601                         if (new_expr)
 602                                 new_tle = makeTargetEntry((Expr *) new_expr,
 603                                                                                   attrno,
 604                                                                                   pstrdup(NameStr(att_tup->attname)),
 605                                                                                   false);
 606                 }
 607
 608                 if (new_tle)
 609                         new_tlist = lappend(new_tlist, new_tle);
 610         }
 611
 612         pfree(new_tles);
 613
 614         parsetree->targetList = list_concat(new_tlist, junk_tlist);
 615 }
 616
 617
 618 /*
 619  * Convert a matched TLE from the original tlist into a correct new TLE.
 620  *
 621  * This routine detects and handles multiple assignments to the same target
 622  * attribute.  (The attribute name is needed only for error messages.)
 623  */
 624 static TargetEntry *
 625 process_matched_tle(TargetEntry *src_tle,
 626                                         TargetEntry *prior_tle,
 627                                         const char *attrName)
 628 {
 629         TargetEntry *result;
 630         Node       *src_expr;
 631         Node       *prior_expr;
 632         Node       *src_input;
 633         Node       *prior_input;
 634         Node       *priorbottom;
 635         Node       *newexpr;
 636
 637         if (prior_tle == NULL)
 638         {
 639                 /*
 640                  * Normal case where this is the first assignment to the attribute.
 641                  */
 642                 return src_tle;
 643         }
 644
 645         /*----------
 646          * Multiple assignments to same attribute.      Allow only if all are
 647          * FieldStore or ArrayRef assignment operations.  This is a bit
 648          * tricky because what we may actually be looking at is a nest of
 649          * such nodes; consider
 650          *              UPDATE tab SET col.fld1.subfld1 = x, col.fld2.subfld2 = y
 651          * The two expressions produced by the parser will look like
 652          *              FieldStore(col, fld1, FieldStore(placeholder, subfld1, x))
 653          *              FieldStore(col, fld2, FieldStore(placeholder, subfld2, x))
 654          * However, we can ignore the substructure and just consider the top
 655          * FieldStore or ArrayRef from each assignment, because it works to
 656          * combine these as
 657          *              FieldStore(FieldStore(col, fld1,
 658          *                                                        FieldStore(placeholder, subfld1, x)),
 659          *                                 fld2, FieldStore(placeholder, subfld2, x))
 660          * Note the leftmost expression goes on the inside so that the
 661          * assignments appear to occur left-to-right.
 662          *
 663          * For FieldStore, instead of nesting we can generate a single
 664          * FieldStore with multiple target fields.      We must nest when
 665          * ArrayRefs are involved though.
 666          *----------
 667          */
 668         src_expr = (Node *) src_tle->expr;
 669         prior_expr = (Node *) prior_tle->expr;
 670         src_input = get_assignment_input(src_expr);
 671         prior_input = get_assignment_input(prior_expr);
 672         if (src_input == NULL ||
 673                 prior_input == NULL ||
 674                 exprType(src_expr) != exprType(prior_expr))
 675                 ereport(ERROR,
 676                                 (errcode(ERRCODE_SYNTAX_ERROR),
 677                                  errmsg("multiple assignments to same column \"%s\"",
 678                                                 attrName)));
 679
 680         /*
 681          * Prior TLE could be a nest of assignments if we do this more than once.
 682          */
 683         priorbottom = prior_input;
 684         for (;;)
 685         {
 686                 Node       *newbottom = get_assignment_input(priorbottom);
 687
 688                 if (newbottom == NULL)
 689                         break;                          /* found the original Var reference */
 690                 priorbottom = newbottom;
 691         }
 692         if (!equal(priorbottom, src_input))
 693                 ereport(ERROR,
 694                                 (errcode(ERRCODE_SYNTAX_ERROR),
 695                                  errmsg("multiple assignments to same column \"%s\"",
 696                                                 attrName)));
 697
 698         /*
 699          * Looks OK to nest 'em.
 700          */
 701         if (IsA(src_expr, FieldStore))
 702         {
 703                 FieldStore *fstore = makeNode(FieldStore);
 704
 705                 if (IsA(prior_expr, FieldStore))
 706                 {
 707                         /* combine the two */
 708                         memcpy(fstore, prior_expr, sizeof(FieldStore));
 709                         fstore->newvals =
 710                                 list_concat(list_copy(((FieldStore *) prior_expr)->newvals),
 711                                                         list_copy(((FieldStore *) src_expr)->newvals));
 712                         fstore->fieldnums =
 713                                 list_concat(list_copy(((FieldStore *) prior_expr)->fieldnums),
 714                                                         list_copy(((FieldStore *) src_expr)->fieldnums));
 715                 }
 716                 else
 717                 {
 718                         /* general case, just nest 'em */
 719                         memcpy(fstore, src_expr, sizeof(FieldStore));
 720                         fstore->arg = (Expr *) prior_expr;
 721                 }
 722                 newexpr = (Node *) fstore;
 723         }
 724         else if (IsA(src_expr, ArrayRef))
 725         {
 726                 ArrayRef   *aref = makeNode(ArrayRef);
 727
 728                 memcpy(aref, src_expr, sizeof(ArrayRef));
 729                 aref->refexpr = (Expr *) prior_expr;
 730                 newexpr = (Node *) aref;
 731         }
 732         else
 733         {
 734                 elog(ERROR, "can't happen");
 735                 newexpr = NULL;
 736         }
 737
 738         result = flatCopyTargetEntry(src_tle);
 739         result->expr = (Expr *) newexpr;
 740         return result;
 741 }
 742
 743 /*
 744  * If node is an assignment node, return its input; else return NULL
 745  */
 746 static Node *
 747 get_assignment_input(Node *node)
 748 {
 749         if (node == NULL)
 750                 return NULL;
 751         if (IsA(node, FieldStore))
 752         {
 753                 FieldStore *fstore = (FieldStore *) node;
 754
 755                 return (Node *) fstore->arg;
 756         }
 757         else if (IsA(node, ArrayRef))
 758         {
 759                 ArrayRef   *aref = (ArrayRef *) node;
 760
 761                 if (aref->refassgnexpr == NULL)
 762                         return NULL;
 763                 return (Node *) aref->refexpr;
 764         }
 765         return NULL;
 766 }
 767
 768 /*
 769  * Make an expression tree for the default value for a column.
 770  *
 771  * If there is no default, return a NULL instead.
 772  */
 773 Node *
 774 build_column_default(Relation rel, int attrno)
 775 {
 776         TupleDesc       rd_att = rel->rd_att;
 777         Form_pg_attribute att_tup = rd_att->attrs[attrno - 1];
 778         Oid                     atttype = att_tup->atttypid;
 779         int32           atttypmod = att_tup->atttypmod;
 780         Node       *expr = NULL;
 781         Oid                     exprtype;
 782
 783         /*
 784          * Scan to see if relation has a default for this column.
 785          */
 786         if (rd_att->constr && rd_att->constr->num_defval > 0)
 787         {
 788                 AttrDefault *defval = rd_att->constr->defval;
 789                 int                     ndef = rd_att->constr->num_defval;
 790
 791                 while (--ndef >= 0)
 792                 {
 793                         if (attrno == defval[ndef].adnum)
 794                         {
 795                                 /*
 796                                  * Found it, convert string representation to node tree.
 797                                  */
 798                                 expr = stringToNode(defval[ndef].adbin);
 799                                 break;
 800                         }
 801                 }
 802         }
 803
 804         if (expr == NULL)
 805         {
 806                 /*
 807                  * No per-column default, so look for a default for the type itself.
 808                  */
 809                 expr = get_typdefault(atttype);
 810         }
 811
 812         if (expr == NULL)
 813                 return NULL;                    /* No default anywhere */
 814
 815         /*
 816          * Make sure the value is coerced to the target column type; this will
 817          * generally be true already, but there seem to be some corner cases
 818          * involving domain defaults where it might not be true. This should match
 819          * the parser's processing of non-defaulted expressions --- see
 820          * updateTargetListEntry().
 821          */
 822         exprtype = exprType(expr);
 823
 824         expr = coerce_to_target_type(NULL,      /* no UNKNOWN params here */
 825                                                                  expr, exprtype,
 826                                                                  atttype, atttypmod,
 827                                                                  COERCION_ASSIGNMENT,
 828                                                                  COERCE_IMPLICIT_CAST);
 829         if (expr == NULL)
 830                 ereport(ERROR,
 831                                 (errcode(ERRCODE_DATATYPE_MISMATCH),
 832                                  errmsg("column \"%s\" is of type %s"
 833                                                 " but default expression is of type %s",
 834                                                 NameStr(att_tup->attname),
 835                                                 format_type_be(atttype),
 836                                                 format_type_be(exprtype)),
 837                            errhint("You will need to rewrite or cast the expression.")));
 838
 839         return expr;
 840 }
 841
 842
 843 /*
 844  * matchLocks -
 845  *        match the list of locks and returns the matching rules
 846  */
 847 static List *
 848 matchLocks(CmdType event,
 849                    RuleLock *rulelocks,
 850                    int varno,
 851                    Query *parsetree)
 852 {
 853         List       *matching_locks = NIL;
 854         int                     nlocks;
 855         int                     i;
 856
 857         if (rulelocks == NULL)
 858                 return NIL;
 859
 860         if (parsetree->commandType != CMD_SELECT)
 861         {
 862                 if (parsetree->resultRelation != varno)
 863                         return NIL;
 864         }
 865
 866         nlocks = rulelocks->numLocks;
 867
 868         for (i = 0; i < nlocks; i++)
 869         {
 870                 RewriteRule *oneLock = rulelocks->rules[i];
 871
 872                 if (oneLock->event == event)
 873                 {
 874                         if (parsetree->commandType != CMD_SELECT ||
 875                                 (oneLock->attrno == -1 ?
 876                                  rangeTableEntry_used((Node *) parsetree, varno, 0) :
 877                                  attribute_used((Node *) parsetree,
 878                                                                 varno, oneLock->attrno, 0)))
 879                                 matching_locks = lappend(matching_locks, oneLock);
 880                 }
 881         }
 882
 883         return matching_locks;
 884 }
 885
 886
 887 /*
 888  * ApplyRetrieveRule - expand an ON SELECT rule
 889  */
 890 static Query *
 891 ApplyRetrieveRule(Query *parsetree,
 892                                   RewriteRule *rule,
 893                                   int rt_index,
 894                                   bool relation_level,
 895                                   Relation relation,
 896                                   List *activeRIRs)
 897 {
 898         Query      *rule_action;
 899         RangeTblEntry *rte,
 900                            *subrte;
 901
 902         if (list_length(rule->actions) != 1)
 903                 elog(ERROR, "expected just one rule action");
 904         if (rule->qual != NULL)
 905                 elog(ERROR, "cannot handle qualified ON SELECT rule");
 906         if (!relation_level)
 907                 elog(ERROR, "cannot handle per-attribute ON SELECT rule");
 908
 909         /*
 910          * Make a modifiable copy of the view query, and acquire needed locks on
 911          * the relations it mentions.
 912          */
 913         rule_action = copyObject(linitial(rule->actions));
 914
 915         AcquireRewriteLocks(rule_action);
 916
 917         /*
 918          * Recursively expand any view references inside the view.
 919          */
 920         rule_action = fireRIRrules(rule_action, activeRIRs);
 921
 922         /*
 923          * VIEWs are really easy --- just plug the view query in as a subselect,
 924          * replacing the relation's original RTE.
 925          */
 926         rte = rt_fetch(rt_index, parsetree->rtable);
 927
 928         rte->rtekind = RTE_SUBQUERY;
 929         rte->relid = InvalidOid;
 930         rte->subquery = rule_action;
 931         rte->inh = false;                       /* must not be set for a subquery */
 932
 933         /*
 934          * We move the view's permission check data down to its rangetable. The
 935          * checks will actually be done against the *OLD* entry therein.
 936          */
 937         subrte = rt_fetch(PRS2_OLD_VARNO, rule_action->rtable);
 938         Assert(subrte->relid == relation->rd_id);
 939         subrte->requiredPerms = rte->requiredPerms;
 940         subrte->checkAsUser = rte->checkAsUser;
 941
 942         rte->requiredPerms = 0;         /* no permission check on subquery itself */
 943         rte->checkAsUser = InvalidOid;
 944
 945         /*
 946          * FOR UPDATE/SHARE of view?
 947          */
 948         if (list_member_int(parsetree->rowMarks, rt_index))
 949         {
 950                 /*
 951                  * Remove the view from the list of rels that will actually be marked
 952                  * FOR UPDATE/SHARE by the executor.  It will still be access- checked
 953                  * for write access, though.
 954                  */
 955                 parsetree->rowMarks = list_delete_int(parsetree->rowMarks, rt_index);
 956
 957                 /*
 958                  * Set up the view's referenced tables as if FOR UPDATE/SHARE.
 959                  */
 960                 markQueryForLocking(rule_action, parsetree->forUpdate,
 961                                                         parsetree->rowNoWait, true);
 962         }
 963
 964         return parsetree;
 965 }
 966
 967 /*
 968  * Recursively mark all relations used by a view as FOR UPDATE/SHARE.
 969  *
 970  * This may generate an invalid query, eg if some sub-query uses an
 971  * aggregate.  We leave it to the planner to detect that.
 972  *
 973  * NB: this must agree with the parser's transformLocking() routine.
 974  */
 975 static void
 976 markQueryForLocking(Query *qry, bool forUpdate, bool noWait, bool skipOldNew)
 977 {
 978         Index           rti = 0;
 979         ListCell   *l;
 980
 981         if (qry->rowMarks)
 982         {
 983                 if (forUpdate != qry->forUpdate)
 984                         ereport(ERROR,
 985                                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 986                         errmsg("cannot use both FOR UPDATE and FOR SHARE in one query")));
 987                 if (noWait != qry->rowNoWait)
 988                         ereport(ERROR,
 989                                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 990                                          errmsg("cannot use both wait and NOWAIT in one query")));
 991         }
 992         qry->forUpdate = forUpdate;
 993         qry->rowNoWait = noWait;
 994
 995         foreach(l, qry->rtable)
 996         {
 997                 RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
 998
 999                 rti++;
1000
1001                 /* Ignore OLD and NEW entries if we are at top level of view */
1002                 if (skipOldNew &&
1003                         (rti == PRS2_OLD_VARNO || rti == PRS2_NEW_VARNO))
1004                         continue;
1005
1006                 if (rte->rtekind == RTE_RELATION)
1007                 {
1008                         qry->rowMarks = list_append_unique_int(qry->rowMarks, rti);
1009                         rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
1010                 }
1011                 else if (rte->rtekind == RTE_SUBQUERY)
1012                 {
1013                         /* FOR UPDATE/SHARE of subquery is propagated to subquery's rels */
1014                         markQueryForLocking(rte->subquery, forUpdate, noWait, false);
1015                 }
1016         }
1017 }
1018
1019
1020 /*
1021  * fireRIRonSubLink -
1022  *      Apply fireRIRrules() to each SubLink (subselect in expression) found
1023  *      in the given tree.
1024  *
1025  * NOTE: although this has the form of a walker, we cheat and modify the
1026  * SubLink nodes in-place.      It is caller's responsibility to ensure that
1027  * no unwanted side-effects occur!
1028  *
1029  * This is unlike most of the other routines that recurse into subselects,
1030  * because we must take control at the SubLink node in order to replace
1031  * the SubLink's subselect link with the possibly-rewritten subquery.
1032  */
1033 static bool
1034 fireRIRonSubLink(Node *node, List *activeRIRs)
1035 {
1036         if (node == NULL)
1037                 return false;
1038         if (IsA(node, SubLink))
1039         {
1040                 SubLink    *sub = (SubLink *) node;
1041
1042                 /* Do what we came for */
1043                 sub->subselect = (Node *) fireRIRrules((Query *) sub->subselect,
1044                                                                                            activeRIRs);
1045                 /* Fall through to process lefthand args of SubLink */
1046         }
1047
1048         /*
1049          * Do NOT recurse into Query nodes, because fireRIRrules already processed
1050          * subselects of subselects for us.
1051          */
1052         return expression_tree_walker(node, fireRIRonSubLink,
1053                                                                   (void *) activeRIRs);
1054 }
1055
1056
1057 /*
1058  * fireRIRrules -
1059  *      Apply all RIR rules on each rangetable entry in a query
1060  */
1061 static Query *
1062 fireRIRrules(Query *parsetree, List *activeRIRs)
1063 {
1064         int                     rt_index;
1065
1066         /*
1067          * don't try to convert this into a foreach loop, because rtable list can
1068          * get changed each time through...
1069          */
1070         rt_index = 0;
1071         while (rt_index < list_length(parsetree->rtable))
1072         {
1073                 RangeTblEntry *rte;
1074                 Relation        rel;
1075                 List       *locks;
1076                 RuleLock   *rules;
1077                 RewriteRule *rule;
1078                 int                     i;
1079
1080                 ++rt_index;
1081
1082                 rte = rt_fetch(rt_index, parsetree->rtable);
1083
1084                 /*
1085                  * A subquery RTE can't have associated rules, so there's nothing to
1086                  * do to this level of the query, but we must recurse into the
1087                  * subquery to expand any rule references in it.
1088                  */
1089                 if (rte->rtekind == RTE_SUBQUERY)
1090                 {
1091                         rte->subquery = fireRIRrules(rte->subquery, activeRIRs);
1092                         continue;
1093                 }
1094
1095                 /*
1096                  * Joins and other non-relation RTEs can be ignored completely.
1097                  */
1098                 if (rte->rtekind != RTE_RELATION)
1099                         continue;
1100
1101                 /*
1102                  * If the table is not referenced in the query, then we ignore it.
1103                  * This prevents infinite expansion loop due to new rtable entries
1104                  * inserted by expansion of a rule. A table is referenced if it is
1105                  * part of the join set (a source table), or is referenced by any Var
1106                  * nodes, or is the result table.
1107                  */
1108                 if (rt_index != parsetree->resultRelation &&
1109                         !rangeTableEntry_used((Node *) parsetree, rt_index, 0))
1110                         continue;
1111
1112                 /*
1113                  * We can use NoLock here since either the parser or
1114                  * AcquireRewriteLocks should have locked the rel already.
1115                  */
1116                 rel = heap_open(rte->relid, NoLock);
1117
1118                 /*
1119                  * Collect the RIR rules that we must apply
1120                  */
1121                 rules = rel->rd_rules;
1122                 if (rules == NULL)
1123                 {
1124                         heap_close(rel, NoLock);
1125                         continue;
1126                 }
1127                 locks = NIL;
1128                 for (i = 0; i < rules->numLocks; i++)
1129                 {
1130                         rule = rules->rules[i];
1131                         if (rule->event != CMD_SELECT)
1132                                 continue;
1133
1134                         if (rule->attrno > 0)
1135                         {
1136                                 /* per-attr rule; do we need it? */
1137                                 if (!attribute_used((Node *) parsetree, rt_index,
1138                                                                         rule->attrno, 0))
1139                                         continue;
1140                         }
1141
1142                         locks = lappend(locks, rule);
1143                 }
1144
1145                 /*
1146                  * If we found any, apply them --- but first check for recursion!
1147                  */
1148                 if (locks != NIL)
1149                 {
1150                         ListCell   *l;
1151
1152                         if (list_member_oid(activeRIRs, RelationGetRelid(rel)))
1153                                 ereport(ERROR,
1154                                                 (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
1155                                                  errmsg("infinite recursion detected in rules for relation \"%s\"",
1156                                                                 RelationGetRelationName(rel))));
1157                         activeRIRs = lcons_oid(RelationGetRelid(rel), activeRIRs);
1158
1159                         foreach(l, locks)
1160                         {
1161                                 rule = lfirst(l);
1162
1163                                 parsetree = ApplyRetrieveRule(parsetree,
1164                                                                                           rule,
1165                                                                                           rt_index,
1166                                                                                           rule->attrno == -1,
1167                                                                                           rel,
1168                                                                                           activeRIRs);
1169                         }
1170
1171                         activeRIRs = list_delete_first(activeRIRs);
1172                 }
1173
1174                 heap_close(rel, NoLock);
1175         }
1176
1177         /*
1178          * Recurse into sublink subqueries, too.  But we already did the ones in
1179          * the rtable.
1180          */
1181         if (parsetree->hasSubLinks)
1182                 query_tree_walker(parsetree, fireRIRonSubLink, (void *) activeRIRs,
1183                                                   QTW_IGNORE_RT_SUBQUERIES);
1184
1185         return parsetree;
1186 }
1187
1188
1189 /*
1190  * Modify the given query by adding 'AND rule_qual IS NOT TRUE' to its
1191  * qualification.  This is used to generate suitable "else clauses" for
1192  * conditional INSTEAD rules.  (Unfortunately we must use "x IS NOT TRUE",
1193  * not just "NOT x" which the planner is much smarter about, else we will
1194  * do the wrong thing when the qual evaluates to NULL.)
1195  *
1196  * The rule_qual may contain references to OLD or NEW.  OLD references are
1197  * replaced by references to the specified rt_index (the relation that the
1198  * rule applies to).  NEW references are only possible for INSERT and UPDATE
1199  * queries on the relation itself, and so they should be replaced by copies
1200  * of the related entries in the query's own targetlist.
1201  */
1202 static Query *
1203 CopyAndAddInvertedQual(Query *parsetree,
1204                                            Node *rule_qual,
1205                                            int rt_index,
1206                                            CmdType event)
1207 {
1208         /* Don't scribble on the passed qual (it's in the relcache!) */
1209         Node       *new_qual = (Node *) copyObject(rule_qual);
1210
1211         /*
1212          * In case there are subqueries in the qual, acquire necessary locks and
1213          * fix any deleted JOIN RTE entries.  (This is somewhat redundant with
1214          * rewriteRuleAction, but not entirely ... consider restructuring so that
1215          * we only need to process the qual this way once.)
1216          */
1217         (void) acquireLocksOnSubLinks(new_qual, NULL);
1218
1219         /* Fix references to OLD */
1220         ChangeVarNodes(new_qual, PRS2_OLD_VARNO, rt_index, 0);
1221         /* Fix references to NEW */
1222         if (event == CMD_INSERT || event == CMD_UPDATE)
1223                 new_qual = ResolveNew(new_qual,
1224                                                           PRS2_NEW_VARNO,
1225                                                           0,
1226                                                           rt_fetch(rt_index, parsetree->rtable),
1227                                                           parsetree->targetList,
1228                                                           event,
1229                                                           rt_index);
1230         /* And attach the fixed qual */
1231         AddInvertedQual(parsetree, new_qual);
1232
1233         return parsetree;
1234 }
1235
1236
1237 /*
1238  *      fireRules -
1239  *         Iterate through rule locks applying rules.
1240  *
1241  * Input arguments:
1242  *      parsetree - original query
1243  *      rt_index - RT index of result relation in original query
1244  *      event - type of rule event
1245  *      locks - list of rules to fire
1246  * Output arguments:
1247  *      *instead_flag - set TRUE if any unqualified INSTEAD rule is found
1248  *                                      (must be initialized to FALSE)
1249  *      *qual_product - filled with modified original query if any qualified
1250  *                                      INSTEAD rule is found (must be initialized to NULL)
1251  * Return value:
1252  *      list of rule actions adjusted for use with this query
1253  *
1254  * Qualified INSTEAD rules generate their action with the qualification
1255  * condition added.  They also generate a modified version of the original
1256  * query with the negated qualification added, so that it will run only for
1257  * rows that the qualified action doesn't act on.  (If there are multiple
1258  * qualified INSTEAD rules, we AND all the negated quals onto a single
1259  * modified original query.)  We won't execute the original, unmodified
1260  * query if we find either qualified or unqualified INSTEAD rules.      If
1261  * we find both, the modified original query is discarded too.
1262  */
1263 static List *
1264 fireRules(Query *parsetree,
1265                   int rt_index,
1266                   CmdType event,
1267                   List *locks,
1268                   bool *instead_flag,
1269                   Query **qual_product)
1270 {
1271         List       *results = NIL;
1272         ListCell   *l;
1273
1274         foreach(l, locks)
1275         {
1276                 RewriteRule *rule_lock = (RewriteRule *) lfirst(l);
1277                 Node       *event_qual = rule_lock->qual;
1278                 List       *actions = rule_lock->actions;
1279                 QuerySource qsrc;
1280                 ListCell   *r;
1281
1282                 /* Determine correct QuerySource value for actions */
1283                 if (rule_lock->isInstead)
1284                 {
1285                         if (event_qual != NULL)
1286                                 qsrc = QSRC_QUAL_INSTEAD_RULE;
1287                         else
1288                         {
1289                                 qsrc = QSRC_INSTEAD_RULE;
1290                                 *instead_flag = true;   /* report unqualified INSTEAD */
1291                         }
1292                 }
1293                 else
1294                         qsrc = QSRC_NON_INSTEAD_RULE;
1295
1296                 if (qsrc == QSRC_QUAL_INSTEAD_RULE)
1297                 {
1298                         /*
1299                          * If there are INSTEAD rules with qualifications, the original
1300                          * query is still performed. But all the negated rule
1301                          * qualifications of the INSTEAD rules are added so it does its
1302                          * actions only in cases where the rule quals of all INSTEAD rules
1303                          * are false. Think of it as the default action in a case. We save
1304                          * this in *qual_product so RewriteQuery() can add it to the query
1305                          * list after we mangled it up enough.
1306                          *
1307                          * If we have already found an unqualified INSTEAD rule, then
1308                          * *qual_product won't be used, so don't bother building it.
1309                          */
1310                         if (!*instead_flag)
1311                         {
1312                                 if (*qual_product == NULL)
1313                                         *qual_product = copyObject(parsetree);
1314                                 *qual_product = CopyAndAddInvertedQual(*qual_product,
1315                                                                                                            event_qual,
1316                                                                                                            rt_index,
1317                                                                                                            event);
1318                         }
1319                 }
1320
1321                 /* Now process the rule's actions and add them to the result list */
1322                 foreach(r, actions)
1323                 {
1324                         Query      *rule_action = lfirst(r);
1325
1326                         if (rule_action->commandType == CMD_NOTHING)
1327                                 continue;
1328
1329                         rule_action = rewriteRuleAction(parsetree, rule_action,
1330                                                                                         event_qual, rt_index, event);
1331
1332                         rule_action->querySource = qsrc;
1333                         rule_action->canSetTag = false;         /* might change later */
1334
1335                         results = lappend(results, rule_action);
1336                 }
1337         }
1338
1339         return results;
1340 }
1341
1342
1343 /*
1344  * RewriteQuery -
1345  *        rewrites the query and apply the rules again on the queries rewritten
1346  *
1347  * rewrite_events is a list of open query-rewrite actions, so we can detect
1348  * infinite recursion.
1349  */
1350 static List *
1351 RewriteQuery(Query *parsetree, List *rewrite_events)
1352 {
1353         CmdType         event = parsetree->commandType;
1354         bool            instead = false;
1355         Query      *qual_product = NULL;
1356         List       *rewritten = NIL;
1357
1358         /*
1359          * If the statement is an update, insert or delete - fire rules on it.
1360          *
1361          * SELECT rules are handled later when we have all the queries that should
1362          * get executed.  Also, utilities aren't rewritten at all (do we still
1363          * need that check?)
1364          */
1365         if (event != CMD_SELECT && event != CMD_UTILITY)
1366         {
1367                 int                     result_relation;
1368                 RangeTblEntry *rt_entry;
1369                 Relation        rt_entry_relation;
1370                 List       *locks;
1371
1372                 result_relation = parsetree->resultRelation;
1373                 Assert(result_relation != 0);
1374                 rt_entry = rt_fetch(result_relation, parsetree->rtable);
1375                 Assert(rt_entry->rtekind == RTE_RELATION);
1376
1377                 /*
1378                  * We can use NoLock here since either the parser or
1379                  * AcquireRewriteLocks should have locked the rel already.
1380                  */
1381                 rt_entry_relation = heap_open(rt_entry->relid, NoLock);
1382
1383                 /*
1384                  * If it's an INSERT or UPDATE, rewrite the targetlist into standard
1385                  * form.  This will be needed by the planner anyway, and doing it now
1386                  * ensures that any references to NEW.field will behave sanely.
1387                  */
1388                 if (event == CMD_INSERT || event == CMD_UPDATE)
1389                         rewriteTargetList(parsetree, rt_entry_relation);
1390
1391                 /*
1392                  * Collect and apply the appropriate rules.
1393                  */
1394                 locks = matchLocks(event, rt_entry_relation->rd_rules,
1395                                                    result_relation, parsetree);
1396
1397                 if (locks != NIL)
1398                 {
1399                         List       *product_queries;
1400
1401                         product_queries = fireRules(parsetree,
1402                                                                                 result_relation,
1403                                                                                 event,
1404                                                                                 locks,
1405                                                                                 &instead,
1406                                                                                 &qual_product);
1407
1408                         /*
1409                          * If we got any product queries, recursively rewrite them --- but
1410                          * first check for recursion!
1411                          */
1412                         if (product_queries != NIL)
1413                         {
1414                                 ListCell   *n;
1415                                 rewrite_event *rev;
1416
1417                                 foreach(n, rewrite_events)
1418                                 {
1419                                         rev = (rewrite_event *) lfirst(n);
1420                                         if (rev->relation == RelationGetRelid(rt_entry_relation) &&
1421                                                 rev->event == event)
1422                                                 ereport(ERROR,
1423                                                                 (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
1424                                                                  errmsg("infinite recursion detected in rules for relation \"%s\"",
1425                                                            RelationGetRelationName(rt_entry_relation))));
1426                                 }
1427
1428                                 rev = (rewrite_event *) palloc(sizeof(rewrite_event));
1429                                 rev->relation = RelationGetRelid(rt_entry_relation);
1430                                 rev->event = event;
1431                                 rewrite_events = lcons(rev, rewrite_events);
1432
1433                                 foreach(n, product_queries)
1434                                 {
1435                                         Query      *pt = (Query *) lfirst(n);
1436                                         List       *newstuff;
1437
1438                                         newstuff = RewriteQuery(pt, rewrite_events);
1439                                         rewritten = list_concat(rewritten, newstuff);
1440                                 }
1441
1442                                 rewrite_events = list_delete_first(rewrite_events);
1443                         }
1444                 }
1445
1446                 heap_close(rt_entry_relation, NoLock);
1447         }
1448
1449         /*
1450          * For INSERTs, the original query is done first; for UPDATE/DELETE, it is
1451          * done last.  This is needed because update and delete rule actions might
1452          * not do anything if they are invoked after the update or delete is
1453          * performed. The command counter increment between the query executions
1454          * makes the deleted (and maybe the updated) tuples disappear so the scans
1455          * for them in the rule actions cannot find them.
1456          *
1457          * If we found any unqualified INSTEAD, the original query is not done at
1458          * all, in any form.  Otherwise, we add the modified form if qualified
1459          * INSTEADs were found, else the unmodified form.
1460          */
1461         if (!instead)
1462         {
1463                 if (parsetree->commandType == CMD_INSERT)
1464                 {
1465                         if (qual_product != NULL)
1466                                 rewritten = lcons(qual_product, rewritten);
1467                         else
1468                                 rewritten = lcons(parsetree, rewritten);
1469                 }
1470                 else
1471                 {
1472                         if (qual_product != NULL)
1473                                 rewritten = lappend(rewritten, qual_product);
1474                         else
1475                                 rewritten = lappend(rewritten, parsetree);
1476                 }
1477         }
1478
1479         return rewritten;
1480 }
1481
1482
1483 /*
1484  * QueryRewrite -
1485  *        Primary entry point to the query rewriter.
1486  *        Rewrite one query via query rewrite system, possibly returning 0
1487  *        or many queries.
1488  *
1489  * NOTE: the parsetree must either have come straight from the parser,
1490  * or have been scanned by AcquireRewriteLocks to acquire suitable locks.
1491  */
1492 List *
1493 QueryRewrite(Query *parsetree)
1494 {
1495         List       *querylist;
1496         List       *results = NIL;
1497         ListCell   *l;
1498         CmdType         origCmdType;
1499         bool            foundOriginalQuery;
1500         Query      *lastInstead;
1501
1502         /*
1503          * Step 1
1504          *
1505          * Apply all non-SELECT rules possibly getting 0 or many queries
1506          */
1507         querylist = RewriteQuery(parsetree, NIL);
1508
1509         /*
1510          * Step 2
1511          *
1512          * Apply all the RIR rules on each query
1513          */
1514         foreach(l, querylist)
1515         {
1516                 Query      *query = (Query *) lfirst(l);
1517
1518                 query = fireRIRrules(query, NIL);
1519
1520                 /*
1521                  * If the query target was rewritten as a view, complain.
1522                  */
1523                 if (query->resultRelation)
1524                 {
1525                         RangeTblEntry *rte = rt_fetch(query->resultRelation,
1526                                                                                   query->rtable);
1527
1528                         if (rte->rtekind == RTE_SUBQUERY)
1529                         {
1530                                 switch (query->commandType)
1531                                 {
1532                                         case CMD_INSERT:
1533                                                 ereport(ERROR,
1534                                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1535                                                                  errmsg("cannot insert into a view"),
1536                                                                  errhint("You need an unconditional ON INSERT DO INSTEAD rule.")));
1537                                                 break;
1538                                         case CMD_UPDATE:
1539                                                 ereport(ERROR,
1540                                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1541                                                                  errmsg("cannot update a view"),
1542                                                                  errhint("You need an unconditional ON UPDATE DO INSTEAD rule.")));
1543                                                 break;
1544                                         case CMD_DELETE:
1545                                                 ereport(ERROR,
1546                                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1547                                                                  errmsg("cannot delete from a view"),
1548                                                                  errhint("You need an unconditional ON DELETE DO INSTEAD rule.")));
1549                                                 break;
1550                                         default:
1551                                                 elog(ERROR, "unrecognized commandType: %d",
1552                                                          (int) query->commandType);
1553                                                 break;
1554                                 }
1555                         }
1556                 }
1557
1558                 results = lappend(results, query);
1559         }
1560
1561         /*
1562          * Step 3
1563          *
1564          * Determine which, if any, of the resulting queries is supposed to set the
1565          * command-result tag; and update the canSetTag fields accordingly.
1566          *
1567          * If the original query is still in the list, it sets the command tag.
1568          * Otherwise, the last INSTEAD query of the same kind as the original is
1569          * allowed to set the tag.      (Note these rules can leave us with no query
1570          * setting the tag.  The tcop code has to cope with this by setting up a
1571          * default tag based on the original un-rewritten query.)
1572          *
1573          * The Asserts verify that at most one query in the result list is marked
1574          * canSetTag.  If we aren't checking asserts, we can fall out of the loop
1575          * as soon as we find the original query.
1576          */
1577         origCmdType = parsetree->commandType;
1578         foundOriginalQuery = false;
1579         lastInstead = NULL;
1580
1581         foreach(l, results)
1582         {
1583                 Query      *query = (Query *) lfirst(l);
1584
1585                 if (query->querySource == QSRC_ORIGINAL)
1586                 {
1587                         Assert(query->canSetTag);
1588                         Assert(!foundOriginalQuery);
1589                         foundOriginalQuery = true;
1590 #ifndef USE_ASSERT_CHECKING
1591                         break;
1592 #endif
1593                 }
1594                 else
1595                 {
1596                         Assert(!query->canSetTag);
1597                         if (query->commandType == origCmdType &&
1598                                 (query->querySource == QSRC_INSTEAD_RULE ||
1599                                  query->querySource == QSRC_QUAL_INSTEAD_RULE))
1600                                 lastInstead = query;
1601                 }
1602         }
1603
1604         if (!foundOriginalQuery && lastInstead != NULL)
1605                 lastInstead->canSetTag = true;
1606
1607         return results;
1608 }