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  * Validator for "check_option" reloption on views. The allowed values
  43  * are "local" and "cascaded".
  44  */
  45 void
  46 validateWithCheckOption(const char *value)
  47 {
  48         if (value == NULL ||
  49                 (strcmp(value, "local") != 0 &&
  50                  strcmp(value, "cascaded") != 0))
  51         {
  52                 ereport(ERROR,
  53                                 (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  54                                  errmsg("invalid value for \"check_option\" option"),
  55                                  errdetail("Valid values are \"local\" and \"cascaded\".")));
  56         }
  57 }
  58
  59 /*---------------------------------------------------------------------
  60  * DefineVirtualRelation
  61  *
  62  * Create a view relation and use the rules system to store the query
  63  * for the view.
  64  *
  65  * EventTriggerAlterTableStart must have been called already.
  66  *---------------------------------------------------------------------
  67  */
  68 static ObjectAddress
  69 DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
  70                                           List *options, Query *viewParse)
  71 {
  72         Oid                     viewOid;
  73         LOCKMODE        lockmode;
  74         CreateStmt *createStmt = makeNode(CreateStmt);
  75         List       *attrList;
  76         ListCell   *t;
  77
  78         /*
  79          * create a list of ColumnDef nodes based on the names and types of the
  80          * (non-junk) targetlist items from the view's SELECT list.
  81          */
  82         attrList = NIL;
  83         foreach(t, tlist)
  84         {
  85                 TargetEntry *tle = (TargetEntry *) lfirst(t);
  86
  87                 if (!tle->resjunk)
  88                 {
  89                         ColumnDef  *def = makeColumnDef(tle->resname,
  90                                                                                         exprType((Node *) tle->expr),
  91                                                                                         exprTypmod((Node *) tle->expr),
  92                                                                                         exprCollation((Node *) tle->expr));
  93
  94                         /*
  95                          * It's possible that the column is of a collatable type but the
  96                          * collation could not be resolved, so double-check.
  97                          */
  98                         if (type_is_collatable(exprType((Node *) tle->expr)))
  99                         {
 100                                 if (!OidIsValid(def->collOid))
 101                                         ereport(ERROR,
 102                                                         (errcode(ERRCODE_INDETERMINATE_COLLATION),
 103                                                          errmsg("could not determine which collation to use for view column \"%s\"",
 104                                                                         def->colname),
 105                                                          errhint("Use the COLLATE clause to set the collation explicitly.")));
 106                         }
 107                         else
 108                                 Assert(!OidIsValid(def->collOid));
 109
 110                         attrList = lappend(attrList, def);
 111                 }
 112         }
 113
 114         /*
 115          * Look up, check permissions on, and lock the creation namespace; also
 116          * check for a preexisting view with the same name.  This will also set
 117          * relation->relpersistence to RELPERSISTENCE_TEMP if the selected
 118          * namespace is temporary.
 119          */
 120         lockmode = replace ? AccessExclusiveLock : NoLock;
 121         (void) RangeVarGetAndCheckCreationNamespace(relation, lockmode, &viewOid);
 122
 123         if (OidIsValid(viewOid) && replace)
 124         {
 125                 Relation        rel;
 126                 TupleDesc       descriptor;
 127                 List       *atcmds = NIL;
 128                 AlterTableCmd *atcmd;
 129                 ObjectAddress address;
 130
 131                 /* Relation is already locked, but we must build a relcache entry. */
 132                 rel = relation_open(viewOid, NoLock);
 133
 134                 /* Make sure it *is* a view. */
 135                 if (rel->rd_rel->relkind != RELKIND_VIEW)
 136                         ereport(ERROR,
 137                                         (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 138                                          errmsg("\"%s\" is not a view",
 139                                                         RelationGetRelationName(rel))));
 140
 141                 /* Also check it's not in use already */
 142                 CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW");
 143
 144                 /*
 145                  * Due to the namespace visibility rules for temporary objects, we
 146                  * should only end up replacing a temporary view with another
 147                  * temporary view, and similarly for permanent views.
 148                  */
 149                 Assert(relation->relpersistence == rel->rd_rel->relpersistence);
 150
 151                 /*
 152                  * Create a tuple descriptor to compare against the existing view, and
 153                  * verify that the old column list is an initial prefix of the new
 154                  * column list.
 155                  */
 156                 descriptor = BuildDescForRelation(attrList);
 157                 checkViewTupleDesc(descriptor, rel->rd_att);
 158
 159                 /*
 160                  * If new attributes have been added, we must add pg_attribute entries
 161                  * for them.  It is convenient (although overkill) to use the ALTER
 162                  * TABLE ADD COLUMN infrastructure for this.
 163                  *
 164                  * Note that we must do this before updating the query for the view,
 165                  * since the rules system requires that the correct view columns be in
 166                  * place when defining the new rules.
 167                  */
 168                 if (list_length(attrList) > rel->rd_att->natts)
 169                 {
 170                         ListCell   *c;
 171                         int                     skip = rel->rd_att->natts;
 172
 173                         foreach(c, attrList)
 174                         {
 175                                 if (skip > 0)
 176                                 {
 177                                         skip--;
 178                                         continue;
 179                                 }
 180                                 atcmd = makeNode(AlterTableCmd);
 181                                 atcmd->subtype = AT_AddColumnToView;
 182                                 atcmd->def = (Node *) lfirst(c);
 183                                 atcmds = lappend(atcmds, atcmd);
 184                         }
 185
 186                         /* EventTriggerAlterTableStart called by ProcessUtilitySlow */
 187                         AlterTableInternal(viewOid, atcmds, true);
 188
 189                         /* Make the new view columns visible */
 190                         CommandCounterIncrement();
 191                 }
 192
 193                 /*
 194                  * Update the query for the view.
 195                  *
 196                  * Note that we must do this before updating the view options, because
 197                  * the new options may not be compatible with the old view query (for
 198                  * example if we attempt to add the WITH CHECK OPTION, we require that
 199                  * the new view be automatically updatable, but the old view may not
 200                  * have been).
 201                  */
 202                 StoreViewQuery(viewOid, viewParse, replace);
 203
 204                 /* Make the new view query visible */
 205                 CommandCounterIncrement();
 206
 207                 /*
 208                  * Update the view's options.
 209                  *
 210                  * The new options list replaces the existing options list, even if
 211                  * it's empty.
 212                  */
 213                 atcmd = makeNode(AlterTableCmd);
 214                 atcmd->subtype = AT_ReplaceRelOptions;
 215                 atcmd->def = (Node *) options;
 216                 atcmds = list_make1(atcmd);
 217
 218                 /* EventTriggerAlterTableStart called by ProcessUtilitySlow */
 219                 AlterTableInternal(viewOid, atcmds, true);
 220
 221                 /*
 222                  * There is very little to do here to update the view's dependencies.
 223                  * Most view-level dependency relationships, such as those on the
 224                  * owner, schema, and associated composite type, aren't changing.
 225                  * Because we don't allow changing type or collation of an existing
 226                  * view column, those dependencies of the existing columns don't
 227                  * change either, while the AT_AddColumnToView machinery took care of
 228                  * adding such dependencies for new view columns.  The dependencies of
 229                  * the view's query could have changed arbitrarily, but that was dealt
 230                  * with inside StoreViewQuery.  What remains is only to check that
 231                  * view replacement is allowed when we're creating an extension.
 232                  */
 233                 ObjectAddressSet(address, RelationRelationId, viewOid);
 234
 235                 recordDependencyOnCurrentExtension(&address, true);
 236
 237                 /*
 238                  * Seems okay, so return the OID of the pre-existing view.
 239                  */
 240                 relation_close(rel, NoLock);    /* keep the lock! */
 241
 242                 return address;
 243         }
 244         else
 245         {
 246                 ObjectAddress address;
 247
 248                 /*
 249                  * Set the parameters for keys/inheritance etc. All of these are
 250                  * uninteresting for views...
 251                  */
 252                 createStmt->relation = relation;
 253                 createStmt->tableElts = attrList;
 254                 createStmt->inhRelations = NIL;
 255                 createStmt->constraints = NIL;
 256                 createStmt->options = options;
 257                 createStmt->oncommit = ONCOMMIT_NOOP;
 258                 createStmt->tablespacename = NULL;
 259                 createStmt->if_not_exists = false;
 260
 261                 /*
 262                  * Create the relation (this will error out if there's an existing
 263                  * view, so we don't need more code to complain if "replace" is
 264                  * false).
 265                  */
 266                 address = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid, NULL,
 267                                                                  NULL);
 268                 Assert(address.objectId != InvalidOid);
 269
 270                 /* Make the new view relation visible */
 271                 CommandCounterIncrement();
 272
 273                 /* Store the query for the view */
 274                 StoreViewQuery(address.objectId, viewParse, replace);
 275
 276                 return address;
 277         }
 278 }
 279
 280 /*
 281  * Verify that tupledesc associated with proposed new view definition
 282  * matches tupledesc of old view.  This is basically a cut-down version
 283  * of equalTupleDescs(), with code added to generate specific complaints.
 284  * Also, we allow the new tupledesc to have more columns than the old.
 285  */
 286 static void
 287 checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc)
 288 {
 289         int                     i;
 290
 291         if (newdesc->natts < olddesc->natts)
 292                 ereport(ERROR,
 293                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 294                                  errmsg("cannot drop columns from view")));
 295
 296         for (i = 0; i < olddesc->natts; i++)
 297         {
 298                 Form_pg_attribute newattr = TupleDescAttr(newdesc, i);
 299                 Form_pg_attribute oldattr = TupleDescAttr(olddesc, i);
 300
 301                 /* XXX msg not right, but we don't support DROP COL on view anyway */
 302                 if (newattr->attisdropped != oldattr->attisdropped)
 303                         ereport(ERROR,
 304                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 305                                          errmsg("cannot drop columns from view")));
 306
 307                 if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0)
 308                         ereport(ERROR,
 309                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 310                                          errmsg("cannot change name of view column \"%s\" to \"%s\"",
 311                                                         NameStr(oldattr->attname),
 312                                                         NameStr(newattr->attname))));
 313                 /* XXX would it be safe to allow atttypmod to change?  Not sure */
 314                 if (newattr->atttypid != oldattr->atttypid ||
 315                         newattr->atttypmod != oldattr->atttypmod)
 316                         ereport(ERROR,
 317                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 318                                          errmsg("cannot change data type of view column \"%s\" from %s to %s",
 319                                                         NameStr(oldattr->attname),
 320                                                         format_type_with_typemod(oldattr->atttypid,
 321                                                                                                          oldattr->atttypmod),
 322                                                         format_type_with_typemod(newattr->atttypid,
 323                                                                                                          newattr->atttypmod))));
 324                 /* We can ignore the remaining attributes of an attribute... */
 325         }
 326
 327         /*
 328          * We ignore the constraint fields.  The new view desc can't have any
 329          * constraints, and the only ones that could be on the old view are
 330          * defaults, which we are happy to leave in place.
 331          */
 332 }
 333
 334 static void
 335 DefineViewRules(Oid viewOid, Query *viewParse, bool replace)
 336 {
 337         /*
 338          * Set up the ON SELECT rule.  Since the query has already been through
 339          * parse analysis, we use DefineQueryRewrite() directly.
 340          */
 341         DefineQueryRewrite(pstrdup(ViewSelectRuleName),
 342                                            viewOid,
 343                                            NULL,
 344                                            CMD_SELECT,
 345                                            true,
 346                                            replace,
 347                                            list_make1(viewParse));
 348
 349         /*
 350          * Someday: automatic ON INSERT, etc
 351          */
 352 }
 353
 354 /*---------------------------------------------------------------
 355  * UpdateRangeTableOfViewParse
 356  *
 357  * Update the range table of the given parsetree.
 358  * This update consists of adding two new entries IN THE BEGINNING
 359  * of the range table (otherwise the rule system will die a slow,
 360  * horrible and painful death, and we do not want that now, do we?)
 361  * one for the OLD relation and one for the NEW one (both of
 362  * them refer in fact to the "view" relation).
 363  *
 364  * Of course we must also increase the 'varnos' of all the Var nodes
 365  * by 2...
 366  *
 367  * These extra RT entries are not actually used in the query,
 368  * except for run-time locking and permission checking.
 369  *---------------------------------------------------------------
 370  */
 371 static Query *
 372 UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse)
 373 {
 374         Relation        viewRel;
 375         List       *new_rt;
 376         RangeTblEntry *rt_entry1,
 377                            *rt_entry2;
 378         ParseState *pstate;
 379
 380         /*
 381          * Make a copy of the given parsetree.  It's not so much that we don't
 382          * want to scribble on our input, it's that the parser has a bad habit of
 383          * outputting multiple links to the same subtree for constructs like
 384          * BETWEEN, and we mustn't have OffsetVarNodes increment the varno of a
 385          * Var node twice.  copyObject will expand any multiply-referenced subtree
 386          * into multiple copies.
 387          */
 388         viewParse = copyObject(viewParse);
 389
 390         /* Create a dummy ParseState for addRangeTableEntryForRelation */
 391         pstate = make_parsestate(NULL);
 392
 393         /* need to open the rel for addRangeTableEntryForRelation */
 394         viewRel = relation_open(viewOid, AccessShareLock);
 395
 396         /*
 397          * Create the 2 new range table entries and form the new range table...
 398          * OLD first, then NEW....
 399          */
 400         rt_entry1 = addRangeTableEntryForRelation(pstate, viewRel,
 401                                                                                           AccessShareLock,
 402                                                                                           makeAlias("old", NIL),
 403                                                                                           false, false);
 404         rt_entry2 = addRangeTableEntryForRelation(pstate, viewRel,
 405                                                                                           AccessShareLock,
 406                                                                                           makeAlias("new", NIL),
 407                                                                                           false, false);
 408         /* Must override addRangeTableEntry's default access-check flags */
 409         rt_entry1->requiredPerms = 0;
 410         rt_entry2->requiredPerms = 0;
 411
 412         new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable));
 413
 414         viewParse->rtable = new_rt;
 415
 416         /*
 417          * Now offset all var nodes by 2, and jointree RT indexes too.
 418          */
 419         OffsetVarNodes((Node *) viewParse, 2, 0);
 420
 421         relation_close(viewRel, AccessShareLock);
 422
 423         return viewParse;
 424 }
 425
 426 /*
 427  * DefineView
 428  *              Execute a CREATE VIEW command.
 429  */
 430 ObjectAddress
 431 DefineView(ViewStmt *stmt, const char *queryString,
 432                    int stmt_location, int stmt_len)
 433 {
 434         RawStmt    *rawstmt;
 435         Query      *viewParse;
 436         RangeVar   *view;
 437         ListCell   *cell;
 438         bool            check_option;
 439         ObjectAddress address;
 440
 441         /*
 442          * Run parse analysis to convert the raw parse tree to a Query.  Note this
 443          * also acquires sufficient locks on the source table(s).
 444          *
 445          * Since parse analysis scribbles on its input, copy the raw parse tree;
 446          * this ensures we don't corrupt a prepared statement, for example.
 447          */
 448         rawstmt = makeNode(RawStmt);
 449         rawstmt->stmt = (Node *) copyObject(stmt->query);
 450         rawstmt->stmt_location = stmt_location;
 451         rawstmt->stmt_len = stmt_len;
 452
 453         viewParse = parse_analyze(rawstmt, queryString, NULL, 0, NULL);
 454
 455         /*
 456          * The grammar should ensure that the result is a single SELECT Query.
 457          * However, it doesn't forbid SELECT INTO, so we have to check for that.
 458          */
 459         if (!IsA(viewParse, Query))
 460                 elog(ERROR, "unexpected parse analysis result");
 461         if (viewParse->utilityStmt != NULL &&
 462                 IsA(viewParse->utilityStmt, CreateTableAsStmt))
 463                 ereport(ERROR,
 464                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 465                                  errmsg("views must not contain SELECT INTO")));
 466         if (viewParse->commandType != CMD_SELECT)
 467                 elog(ERROR, "unexpected parse analysis result");
 468
 469         /*
 470          * Check for unsupported cases.  These tests are redundant with ones in
 471          * DefineQueryRewrite(), but that function will complain about a bogus ON
 472          * SELECT rule, and we'd rather the message complain about a view.
 473          */
 474         if (viewParse->hasModifyingCTE)
 475                 ereport(ERROR,
 476                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 477                                  errmsg("views must not contain data-modifying statements in WITH")));
 478
 479         /*
 480          * If the user specified the WITH CHECK OPTION, add it to the list of
 481          * reloptions.
 482          */
 483         if (stmt->withCheckOption == LOCAL_CHECK_OPTION)
 484                 stmt->options = lappend(stmt->options,
 485                                                                 makeDefElem("check_option",
 486                                                                                         (Node *) makeString("local"), -1));
 487         else if (stmt->withCheckOption == CASCADED_CHECK_OPTION)
 488                 stmt->options = lappend(stmt->options,
 489                                                                 makeDefElem("check_option",
 490                                                                                         (Node *) makeString("cascaded"), -1));
 491
 492         /*
 493          * Check that the view is auto-updatable if WITH CHECK OPTION was
 494          * specified.
 495          */
 496         check_option = false;
 497
 498         foreach(cell, stmt->options)
 499         {
 500                 DefElem    *defel = (DefElem *) lfirst(cell);
 501
 502                 if (strcmp(defel->defname, "check_option") == 0)
 503                         check_option = true;
 504         }
 505
 506         /*
 507          * If the check option is specified, look to see if the view is actually
 508          * auto-updatable or not.
 509          */
 510         if (check_option)
 511         {
 512                 const char *view_updatable_error =
 513                 view_query_is_auto_updatable(viewParse, true);
 514
 515                 if (view_updatable_error)
 516                         ereport(ERROR,
 517                                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 518                                          errmsg("WITH CHECK OPTION is supported only on automatically updatable views"),
 519                                          errhint("%s", _(view_updatable_error))));
 520         }
 521
 522         /*
 523          * If a list of column names was given, run through and insert these into
 524          * the actual query tree. - thomas 2000-03-08
 525          */
 526         if (stmt->aliases != NIL)
 527         {
 528                 ListCell   *alist_item = list_head(stmt->aliases);
 529                 ListCell   *targetList;
 530
 531                 foreach(targetList, viewParse->targetList)
 532                 {
 533                         TargetEntry *te = lfirst_node(TargetEntry, targetList);
 534
 535                         /* junk columns don't get aliases */
 536                         if (te->resjunk)
 537                                 continue;
 538                         te->resname = pstrdup(strVal(lfirst(alist_item)));
 539                         alist_item = lnext(alist_item);
 540                         if (alist_item == NULL)
 541                                 break;                  /* done assigning aliases */
 542                 }
 543
 544                 if (alist_item != NULL)
 545                         ereport(ERROR,
 546                                         (errcode(ERRCODE_SYNTAX_ERROR),
 547                                          errmsg("CREATE VIEW specifies more column "
 548                                                         "names than columns")));
 549         }
 550
 551         /* Unlogged views are not sensible. */
 552         if (stmt->view->relpersistence == RELPERSISTENCE_UNLOGGED)
 553                 ereport(ERROR,
 554                                 (errcode(ERRCODE_SYNTAX_ERROR),
 555                                  errmsg("views cannot be unlogged because they do not have storage")));
 556
 557         /*
 558          * If the user didn't explicitly ask for a temporary view, check whether
 559          * we need one implicitly.  We allow TEMP to be inserted automatically as
 560          * long as the CREATE command is consistent with that --- no explicit
 561          * schema name.
 562          */
 563         view = copyObject(stmt->view);  /* don't corrupt original command */
 564         if (view->relpersistence == RELPERSISTENCE_PERMANENT
 565                 && isQueryUsingTempRelation(viewParse))
 566         {
 567                 view->relpersistence = RELPERSISTENCE_TEMP;
 568                 ereport(NOTICE,
 569                                 (errmsg("view \"%s\" will be a temporary view",
 570                                                 view->relname)));
 571         }
 572
 573         /*
 574          * Create the view relation
 575          *
 576          * NOTE: if it already exists and replace is false, the xact will be
 577          * aborted.
 578          */
 579         address = DefineVirtualRelation(view, viewParse->targetList,
 580                                                                         stmt->replace, stmt->options, viewParse);
 581
 582         return address;
 583 }
 584
 585 /*
 586  * Use the rules system to store the query for the view.
 587  */
 588 void
 589 StoreViewQuery(Oid viewOid, Query *viewParse, bool replace)
 590 {
 591         /*
 592          * The range table of 'viewParse' does not contain entries for the "OLD"
 593          * and "NEW" relations. So... add them!
 594          */
 595         viewParse = UpdateRangeTableOfViewParse(viewOid, viewParse);
 596
 597         /*
 598          * Now create the rules associated with the view.
 599          */
 600         DefineViewRules(viewOid, viewParse, replace);
 601 }