granicus.if.org Git - postgresql/blob - src/backend/commands/view.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * view.c
   4  *        use rewrite rules to construct views
   5  *
   6  * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/backend/commands/view.c
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #include "postgres.h"
  16
  17 #include "access/relation.h"
  18 #include "access/xact.h"
  19 #include "catalog/namespace.h"
  20 #include "commands/defrem.h"
  21 #include "commands/tablecmds.h"
  22 #include "commands/view.h"
  23 #include "miscadmin.h"
  24 #include "nodes/makefuncs.h"
  25 #include "nodes/nodeFuncs.h"
  26 #include "parser/analyze.h"
  27 #include "parser/parse_relation.h"
  28 #include "rewrite/rewriteDefine.h"
  29 #include "rewrite/rewriteManip.h"
  30 #include "rewrite/rewriteHandler.h"
  31 #include "rewrite/rewriteSupport.h"
  32 #include "utils/acl.h"
  33 #include "utils/builtins.h"
  34 #include "utils/lsyscache.h"
  35 #include "utils/rel.h"
  36 #include "utils/syscache.h"
  37
  38
  39 static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc);
  40
  41 /*---------------------------------------------------------------------
  42  * DefineVirtualRelation
  43  *
  44  * Create a view relation and use the rules system to store the query
  45  * for the view.
  46  *
  47  * EventTriggerAlterTableStart must have been called already.
  48  *---------------------------------------------------------------------
  49  */
  50 static ObjectAddress
  51 DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
  52                                           List *options, Query *viewParse)
  53 {
  54         Oid                     viewOid;
  55         LOCKMODE        lockmode;
  56         CreateStmt *createStmt = makeNode(CreateStmt);
  57         List       *attrList;
  58         ListCell   *t;
  59
  60         /*
  61          * create a list of ColumnDef nodes based on the names and types of the
  62          * (non-junk) targetlist items from the view's SELECT list.
  63          */
  64         attrList = NIL;
  65         foreach(t, tlist)
  66         {
  67                 TargetEntry *tle = (TargetEntry *) lfirst(t);
  68
  69                 if (!tle->resjunk)
  70                 {
  71                         ColumnDef  *def = makeColumnDef(tle->resname,
  72                                                                                         exprType((Node *) tle->expr),
  73                                                                                         exprTypmod((Node *) tle->expr),
  74                                                                                         exprCollation((Node *) tle->expr));
  75
  76                         /*
  77                          * It's possible that the column is of a collatable type but the
  78                          * collation could not be resolved, so double-check.
  79                          */
  80                         if (type_is_collatable(exprType((Node *) tle->expr)))
  81                         {
  82                                 if (!OidIsValid(def->collOid))
  83                                         ereport(ERROR,
  84                                                         (errcode(ERRCODE_INDETERMINATE_COLLATION),
  85                                                          errmsg("could not determine which collation to use for view column \"%s\"",
  86                                                                         def->colname),
  87                                                          errhint("Use the COLLATE clause to set the collation explicitly.")));
  88                         }
  89                         else
  90                                 Assert(!OidIsValid(def->collOid));
  91
  92                         attrList = lappend(attrList, def);
  93                 }
  94         }
  95
  96         /*
  97          * Look up, check permissions on, and lock the creation namespace; also
  98          * check for a preexisting view with the same name.  This will also set
  99          * relation->relpersistence to RELPERSISTENCE_TEMP if the selected
 100          * namespace is temporary.
 101          */
 102         lockmode = replace ? AccessExclusiveLock : NoLock;
 103         (void) RangeVarGetAndCheckCreationNamespace(relation, lockmode, &viewOid);
 104
 105         if (OidIsValid(viewOid) && replace)
 106         {
 107                 Relation        rel;
 108                 TupleDesc       descriptor;
 109                 List       *atcmds = NIL;
 110                 AlterTableCmd *atcmd;
 111                 ObjectAddress address;
 112
 113                 /* Relation is already locked, but we must build a relcache entry. */
 114                 rel = relation_open(viewOid, NoLock);
 115
 116                 /* Make sure it *is* a view. */
 117                 if (rel->rd_rel->relkind != RELKIND_VIEW)
 118                         ereport(ERROR,
 119                                         (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 120                                          errmsg("\"%s\" is not a view",
 121                                                         RelationGetRelationName(rel))));
 122
 123                 /* Also check it's not in use already */
 124                 CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW");
 125
 126                 /*
 127                  * Due to the namespace visibility rules for temporary objects, we
 128                  * should only end up replacing a temporary view with another
 129                  * temporary view, and similarly for permanent views.
 130                  */
 131                 Assert(relation->relpersistence == rel->rd_rel->relpersistence);
 132
 133                 /*
 134                  * Create a tuple descriptor to compare against the existing view, and
 135                  * verify that the old column list is an initial prefix of the new
 136                  * column list.
 137                  */
 138                 descriptor = BuildDescForRelation(attrList);
 139                 checkViewTupleDesc(descriptor, rel->rd_att);
 140
 141                 /*
 142                  * If new attributes have been added, we must add pg_attribute entries
 143                  * for them.  It is convenient (although overkill) to use the ALTER
 144                  * TABLE ADD COLUMN infrastructure for this.
 145                  *
 146                  * Note that we must do this before updating the query for the view,
 147                  * since the rules system requires that the correct view columns be in
 148                  * place when defining the new rules.
 149                  */
 150                 if (list_length(attrList) > rel->rd_att->natts)
 151                 {
 152                         ListCell   *c;
 153                         int                     skip = rel->rd_att->natts;
 154
 155                         foreach(c, attrList)
 156                         {
 157                                 if (skip > 0)
 158                                 {
 159                                         skip--;
 160                                         continue;
 161                                 }
 162                                 atcmd = makeNode(AlterTableCmd);
 163                                 atcmd->subtype = AT_AddColumnToView;
 164                                 atcmd->def = (Node *) lfirst(c);
 165                                 atcmds = lappend(atcmds, atcmd);
 166                         }
 167
 168                         /* EventTriggerAlterTableStart called by ProcessUtilitySlow */
 169                         AlterTableInternal(viewOid, atcmds, true);
 170
 171                         /* Make the new view columns visible */
 172                         CommandCounterIncrement();
 173                 }
 174
 175                 /*
 176                  * Update the query for the view.
 177                  *
 178                  * Note that we must do this before updating the view options, because
 179                  * the new options may not be compatible with the old view query (for
 180                  * example if we attempt to add the WITH CHECK OPTION, we require that
 181                  * the new view be automatically updatable, but the old view may not
 182                  * have been).
 183                  */
 184                 StoreViewQuery(viewOid, viewParse, replace);
 185
 186                 /* Make the new view query visible */
 187                 CommandCounterIncrement();
 188
 189                 /*
 190                  * Finally update the view options.
 191                  *
 192                  * The new options list replaces the existing options list, even if
 193                  * it's empty.
 194                  */
 195                 atcmd = makeNode(AlterTableCmd);
 196                 atcmd->subtype = AT_ReplaceRelOptions;
 197                 atcmd->def = (Node *) options;
 198                 atcmds = list_make1(atcmd);
 199
 200                 /* EventTriggerAlterTableStart called by ProcessUtilitySlow */
 201                 AlterTableInternal(viewOid, atcmds, true);
 202
 203                 ObjectAddressSet(address, RelationRelationId, viewOid);
 204
 205                 /*
 206                  * Seems okay, so return the OID of the pre-existing view.
 207                  */
 208                 relation_close(rel, NoLock);    /* keep the lock! */
 209
 210                 return address;
 211         }
 212         else
 213         {
 214                 ObjectAddress address;
 215
 216                 /*
 217                  * Set the parameters for keys/inheritance etc. All of these are
 218                  * uninteresting for views...
 219                  */
 220                 createStmt->relation = relation;
 221                 createStmt->tableElts = attrList;
 222                 createStmt->inhRelations = NIL;
 223                 createStmt->constraints = NIL;
 224                 createStmt->options = options;
 225                 createStmt->oncommit = ONCOMMIT_NOOP;
 226                 createStmt->tablespacename = NULL;
 227                 createStmt->if_not_exists = false;
 228
 229                 /*
 230                  * Create the relation (this will error out if there's an existing
 231                  * view, so we don't need more code to complain if "replace" is
 232                  * false).
 233                  */
 234                 address = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid, NULL,
 235                                                                  NULL);
 236                 Assert(address.objectId != InvalidOid);
 237
 238                 /* Make the new view relation visible */
 239                 CommandCounterIncrement();
 240
 241                 /* Store the query for the view */
 242                 StoreViewQuery(address.objectId, viewParse, replace);
 243
 244                 return address;
 245         }
 246 }
 247
 248 /*
 249  * Verify that tupledesc associated with proposed new view definition
 250  * matches tupledesc of old view.  This is basically a cut-down version
 251  * of equalTupleDescs(), with code added to generate specific complaints.
 252  * Also, we allow the new tupledesc to have more columns than the old.
 253  */
 254 static void
 255 checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc)
 256 {
 257         int                     i;
 258
 259         if (newdesc->natts < olddesc->natts)
 260                 ereport(ERROR,
 261                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 262                                  errmsg("cannot drop columns from view")));
 263
 264         for (i = 0; i < olddesc->natts; i++)
 265         {
 266                 Form_pg_attribute newattr = TupleDescAttr(newdesc, i);
 267                 Form_pg_attribute oldattr = TupleDescAttr(olddesc, i);
 268
 269                 /* XXX msg not right, but we don't support DROP COL on view anyway */
 270                 if (newattr->attisdropped != oldattr->attisdropped)
 271                         ereport(ERROR,
 272                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 273                                          errmsg("cannot drop columns from view")));
 274
 275                 if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0)
 276                         ereport(ERROR,
 277                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 278                                          errmsg("cannot change name of view column \"%s\" to \"%s\"",
 279                                                         NameStr(oldattr->attname),
 280                                                         NameStr(newattr->attname))));
 281                 /* XXX would it be safe to allow atttypmod to change?  Not sure */
 282                 if (newattr->atttypid != oldattr->atttypid ||
 283                         newattr->atttypmod != oldattr->atttypmod)
 284                         ereport(ERROR,
 285                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 286                                          errmsg("cannot change data type of view column \"%s\" from %s to %s",
 287                                                         NameStr(oldattr->attname),
 288                                                         format_type_with_typemod(oldattr->atttypid,
 289                                                                                                          oldattr->atttypmod),
 290                                                         format_type_with_typemod(newattr->atttypid,
 291                                                                                                          newattr->atttypmod))));
 292                 /* We can ignore the remaining attributes of an attribute... */
 293         }
 294
 295         /*
 296          * We ignore the constraint fields.  The new view desc can't have any
 297          * constraints, and the only ones that could be on the old view are
 298          * defaults, which we are happy to leave in place.
 299          */
 300 }
 301
 302 static void
 303 DefineViewRules(Oid viewOid, Query *viewParse, bool replace)
 304 {
 305         /*
 306          * Set up the ON SELECT rule.  Since the query has already been through
 307          * parse analysis, we use DefineQueryRewrite() directly.
 308          */
 309         DefineQueryRewrite(pstrdup(ViewSelectRuleName),
 310                                            viewOid,
 311                                            NULL,
 312                                            CMD_SELECT,
 313                                            true,
 314                                            replace,
 315                                            list_make1(viewParse));
 316
 317         /*
 318          * Someday: automatic ON INSERT, etc
 319          */
 320 }
 321
 322 /*---------------------------------------------------------------
 323  * UpdateRangeTableOfViewParse
 324  *
 325  * Update the range table of the given parsetree.
 326  * This update consists of adding two new entries IN THE BEGINNING
 327  * of the range table (otherwise the rule system will die a slow,
 328  * horrible and painful death, and we do not want that now, do we?)
 329  * one for the OLD relation and one for the NEW one (both of
 330  * them refer in fact to the "view" relation).
 331  *
 332  * Of course we must also increase the 'varnos' of all the Var nodes
 333  * by 2...
 334  *
 335  * These extra RT entries are not actually used in the query,
 336  * except for run-time locking and permission checking.
 337  *---------------------------------------------------------------
 338  */
 339 static Query *
 340 UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse)
 341 {
 342         Relation        viewRel;
 343         List       *new_rt;
 344         RangeTblEntry *rt_entry1,
 345                            *rt_entry2;
 346         ParseState *pstate;
 347
 348         /*
 349          * Make a copy of the given parsetree.  It's not so much that we don't
 350          * want to scribble on our input, it's that the parser has a bad habit of
 351          * outputting multiple links to the same subtree for constructs like
 352          * BETWEEN, and we mustn't have OffsetVarNodes increment the varno of a
 353          * Var node twice.  copyObject will expand any multiply-referenced subtree
 354          * into multiple copies.
 355          */
 356         viewParse = copyObject(viewParse);
 357
 358         /* Create a dummy ParseState for addRangeTableEntryForRelation */
 359         pstate = make_parsestate(NULL);
 360
 361         /* need to open the rel for addRangeTableEntryForRelation */
 362         viewRel = relation_open(viewOid, AccessShareLock);
 363
 364         /*
 365          * Create the 2 new range table entries and form the new range table...
 366          * OLD first, then NEW....
 367          */
 368         rt_entry1 = addRangeTableEntryForRelation(pstate, viewRel,
 369                                                                                           AccessShareLock,
 370                                                                                           makeAlias("old", NIL),
 371                                                                                           false, false);
 372         rt_entry2 = addRangeTableEntryForRelation(pstate, viewRel,
 373                                                                                           AccessShareLock,
 374                                                                                           makeAlias("new", NIL),
 375                                                                                           false, false);
 376         /* Must override addRangeTableEntry's default access-check flags */
 377         rt_entry1->requiredPerms = 0;
 378         rt_entry2->requiredPerms = 0;
 379
 380         new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable));
 381
 382         viewParse->rtable = new_rt;
 383
 384         /*
 385          * Now offset all var nodes by 2, and jointree RT indexes too.
 386          */
 387         OffsetVarNodes((Node *) viewParse, 2, 0);
 388
 389         relation_close(viewRel, AccessShareLock);
 390
 391         return viewParse;
 392 }
 393
 394 /*
 395  * DefineView
 396  *              Execute a CREATE VIEW command.
 397  */
 398 ObjectAddress
 399 DefineView(ViewStmt *stmt, const char *queryString,
 400                    int stmt_location, int stmt_len)
 401 {
 402         RawStmt    *rawstmt;
 403         Query      *viewParse;
 404         RangeVar   *view;
 405         ListCell   *cell;
 406         bool            check_option;
 407         ObjectAddress address;
 408
 409         /*
 410          * Run parse analysis to convert the raw parse tree to a Query.  Note this
 411          * also acquires sufficient locks on the source table(s).
 412          *
 413          * Since parse analysis scribbles on its input, copy the raw parse tree;
 414          * this ensures we don't corrupt a prepared statement, for example.
 415          */
 416         rawstmt = makeNode(RawStmt);
 417         rawstmt->stmt = (Node *) copyObject(stmt->query);
 418         rawstmt->stmt_location = stmt_location;
 419         rawstmt->stmt_len = stmt_len;
 420
 421         viewParse = parse_analyze(rawstmt, queryString, NULL, 0, NULL);
 422
 423         /*
 424          * The grammar should ensure that the result is a single SELECT Query.
 425          * However, it doesn't forbid SELECT INTO, so we have to check for that.
 426          */
 427         if (!IsA(viewParse, Query))
 428                 elog(ERROR, "unexpected parse analysis result");
 429         if (viewParse->utilityStmt != NULL &&
 430                 IsA(viewParse->utilityStmt, CreateTableAsStmt))
 431                 ereport(ERROR,
 432                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 433                                  errmsg("views must not contain SELECT INTO")));
 434         if (viewParse->commandType != CMD_SELECT)
 435                 elog(ERROR, "unexpected parse analysis result");
 436
 437         /*
 438          * Check for unsupported cases.  These tests are redundant with ones in
 439          * DefineQueryRewrite(), but that function will complain about a bogus ON
 440          * SELECT rule, and we'd rather the message complain about a view.
 441          */
 442         if (viewParse->hasModifyingCTE)
 443                 ereport(ERROR,
 444                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 445                                  errmsg("views must not contain data-modifying statements in WITH")));
 446
 447         /*
 448          * If the user specified the WITH CHECK OPTION, add it to the list of
 449          * reloptions.
 450          */
 451         if (stmt->withCheckOption == LOCAL_CHECK_OPTION)
 452                 stmt->options = lappend(stmt->options,
 453                                                                 makeDefElem("check_option",
 454                                                                                         (Node *) makeString("local"), -1));
 455         else if (stmt->withCheckOption == CASCADED_CHECK_OPTION)
 456                 stmt->options = lappend(stmt->options,
 457                                                                 makeDefElem("check_option",
 458                                                                                         (Node *) makeString("cascaded"), -1));
 459
 460         /*
 461          * Check that the view is auto-updatable if WITH CHECK OPTION was
 462          * specified.
 463          */
 464         check_option = false;
 465
 466         foreach(cell, stmt->options)
 467         {
 468                 DefElem    *defel = (DefElem *) lfirst(cell);
 469
 470                 if (strcmp(defel->defname, "check_option") == 0)
 471                         check_option = true;
 472         }
 473
 474         /*
 475          * If the check option is specified, look to see if the view is actually
 476          * auto-updatable or not.
 477          */
 478         if (check_option)
 479         {
 480                 const char *view_updatable_error =
 481                 view_query_is_auto_updatable(viewParse, true);
 482
 483                 if (view_updatable_error)
 484                         ereport(ERROR,
 485                                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 486                                          errmsg("WITH CHECK OPTION is supported only on automatically updatable views"),
 487                                          errhint("%s", _(view_updatable_error))));
 488         }
 489
 490         /*
 491          * If a list of column names was given, run through and insert these into
 492          * the actual query tree. - thomas 2000-03-08
 493          */
 494         if (stmt->aliases != NIL)
 495         {
 496                 ListCell   *alist_item = list_head(stmt->aliases);
 497                 ListCell   *targetList;
 498
 499                 foreach(targetList, viewParse->targetList)
 500                 {
 501                         TargetEntry *te = lfirst_node(TargetEntry, targetList);
 502
 503                         /* junk columns don't get aliases */
 504                         if (te->resjunk)
 505                                 continue;
 506                         te->resname = pstrdup(strVal(lfirst(alist_item)));
 507                         alist_item = lnext(stmt->aliases, alist_item);
 508                         if (alist_item == NULL)
 509                                 break;                  /* done assigning aliases */
 510                 }
 511
 512                 if (alist_item != NULL)
 513                         ereport(ERROR,
 514                                         (errcode(ERRCODE_SYNTAX_ERROR),
 515                                          errmsg("CREATE VIEW specifies more column "
 516                                                         "names than columns")));
 517         }
 518
 519         /* Unlogged views are not sensible. */
 520         if (stmt->view->relpersistence == RELPERSISTENCE_UNLOGGED)
 521                 ereport(ERROR,
 522                                 (errcode(ERRCODE_SYNTAX_ERROR),
 523                                  errmsg("views cannot be unlogged because they do not have storage")));
 524
 525         /*
 526          * If the user didn't explicitly ask for a temporary view, check whether
 527          * we need one implicitly.  We allow TEMP to be inserted automatically as
 528          * long as the CREATE command is consistent with that --- no explicit
 529          * schema name.
 530          */
 531         view = copyObject(stmt->view);  /* don't corrupt original command */
 532         if (view->relpersistence == RELPERSISTENCE_PERMANENT
 533                 && isQueryUsingTempRelation(viewParse))
 534         {
 535                 view->relpersistence = RELPERSISTENCE_TEMP;
 536                 ereport(NOTICE,
 537                                 (errmsg("view \"%s\" will be a temporary view",
 538                                                 view->relname)));
 539         }
 540
 541         /*
 542          * Create the view relation
 543          *
 544          * NOTE: if it already exists and replace is false, the xact will be
 545          * aborted.
 546          */
 547         address = DefineVirtualRelation(view, viewParse->targetList,
 548                                                                         stmt->replace, stmt->options, viewParse);
 549
 550         return address;
 551 }
 552
 553 /*
 554  * Use the rules system to store the query for the view.
 555  */
 556 void
 557 StoreViewQuery(Oid viewOid, Query *viewParse, bool replace)
 558 {
 559         /*
 560          * The range table of 'viewParse' does not contain entries for the "OLD"
 561          * and "NEW" relations. So... add them!
 562          */
 563         viewParse = UpdateRangeTableOfViewParse(viewOid, viewParse);
 564
 565         /*
 566          * Now create the rules associated with the view.
 567          */
 568         DefineViewRules(viewOid, viewParse, replace);
 569 }