src/backend/commands/view.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * view.c
   4  *        use rewrite rules to construct views
   5  *
   6  * Portions Copyright (c) 1996-2011, 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/heapam.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/rewriteSupport.h"
  31 #include "utils/acl.h"
  32 #include "utils/builtins.h"
  33 #include "utils/lsyscache.h"
  34 #include "utils/rel.h"
  35
  36
  37 static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc);
  38 static bool isViewOnTempTable_walker(Node *node, void *context);
  39
  40 /*---------------------------------------------------------------------
  41  * isViewOnTempTable
  42  *
  43  * Returns true iff any of the relations underlying this view are
  44  * temporary tables.
  45  *---------------------------------------------------------------------
  46  */
  47 static bool
  48 isViewOnTempTable(Query *viewParse)
  49 {
  50         return isViewOnTempTable_walker((Node *) viewParse, NULL);
  51 }
  52
  53 static bool
  54 isViewOnTempTable_walker(Node *node, void *context)
  55 {
  56         if (node == NULL)
  57                 return false;
  58
  59         if (IsA(node, Query))
  60         {
  61                 Query      *query = (Query *) node;
  62                 ListCell   *rtable;
  63
  64                 foreach(rtable, query->rtable)
  65                 {
  66                         RangeTblEntry *rte = lfirst(rtable);
  67
  68                         if (rte->rtekind == RTE_RELATION)
  69                         {
  70                                 Relation        rel = heap_open(rte->relid, AccessShareLock);
  71                                 char            relpersistence = rel->rd_rel->relpersistence;
  72
  73                                 heap_close(rel, AccessShareLock);
  74                                 if (relpersistence == RELPERSISTENCE_TEMP)
  75                                         return true;
  76                         }
  77                 }
  78
  79                 return query_tree_walker(query,
  80                                                                  isViewOnTempTable_walker,
  81                                                                  context,
  82                                                                  QTW_IGNORE_JOINALIASES);
  83         }
  84
  85         return expression_tree_walker(node,
  86                                                                   isViewOnTempTable_walker,
  87                                                                   context);
  88 }
  89
  90 /*---------------------------------------------------------------------
  91  * DefineVirtualRelation
  92  *
  93  * Create the "view" relation. `DefineRelation' does all the work,
  94  * we just provide the correct arguments ... at least when we're
  95  * creating a view.  If we're updating an existing view, we have to
  96  * work harder.
  97  *---------------------------------------------------------------------
  98  */
  99 static Oid
 100 DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace)
 101 {
 102         Oid                     viewOid,
 103                                 namespaceId;
 104         CreateStmt *createStmt = makeNode(CreateStmt);
 105         List       *attrList;
 106         ListCell   *t;
 107
 108         /*
 109          * create a list of ColumnDef nodes based on the names and types of the
 110          * (non-junk) targetlist items from the view's SELECT list.
 111          */
 112         attrList = NIL;
 113         foreach(t, tlist)
 114         {
 115                 TargetEntry *tle = lfirst(t);
 116
 117                 if (!tle->resjunk)
 118                 {
 119                         ColumnDef  *def = makeNode(ColumnDef);
 120
 121                         def->colname = pstrdup(tle->resname);
 122                         def->typeName = makeTypeNameFromOid(exprType((Node *) tle->expr),
 123                                                                                                 exprTypmod((Node *) tle->expr));
 124                         def->inhcount = 0;
 125                         def->is_local = true;
 126                         def->is_not_null = false;
 127                         def->is_from_type = false;
 128                         def->storage = 0;
 129                         def->raw_default = NULL;
 130                         def->cooked_default = NULL;
 131                         def->collClause = NULL;
 132                         def->collOid = exprCollation((Node *) tle->expr);
 133                         /*
 134                          * It's possible that the column is of a collatable type but the
 135                          * collation could not be resolved, so double-check.
 136                          */
 137                         if (type_is_collatable(exprType((Node *) tle->expr)))
 138                         {
 139                                 if (!OidIsValid(def->collOid))
 140                                         ereport(ERROR,
 141                                                         (errcode(ERRCODE_INDETERMINATE_COLLATION),
 142                                                          errmsg("could not determine which collation to use for view column \"%s\"",
 143                                                                         def->colname),
 144                                                          errhint("Use the COLLATE clause to set the collation explicitly.")));
 145                         }
 146                         else
 147                                 Assert(!OidIsValid(def->collOid));
 148                         def->constraints = NIL;
 149
 150                         attrList = lappend(attrList, def);
 151                 }
 152         }
 153
 154         if (attrList == NIL)
 155                 ereport(ERROR,
 156                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 157                                  errmsg("view must have at least one column")));
 158
 159         /*
 160          * Check to see if we want to replace an existing view.
 161          */
 162         namespaceId = RangeVarGetCreationNamespace(relation);
 163         viewOid = get_relname_relid(relation->relname, namespaceId);
 164
 165         if (OidIsValid(viewOid) && replace)
 166         {
 167                 Relation        rel;
 168                 TupleDesc       descriptor;
 169
 170                 /*
 171                  * Yes.  Get exclusive lock on the existing view ...
 172                  */
 173                 rel = relation_open(viewOid, AccessExclusiveLock);
 174
 175                 /*
 176                  * Make sure it *is* a view, and do permissions checks.
 177                  */
 178                 if (rel->rd_rel->relkind != RELKIND_VIEW)
 179                         ereport(ERROR,
 180                                         (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 181                                          errmsg("\"%s\" is not a view",
 182                                                         RelationGetRelationName(rel))));
 183
 184                 if (!pg_class_ownercheck(viewOid, GetUserId()))
 185                         aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
 186                                                    RelationGetRelationName(rel));
 187
 188                 /* Also check it's not in use already */
 189                 CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW");
 190
 191                 /*
 192                  * Due to the namespace visibility rules for temporary objects, we
 193                  * should only end up replacing a temporary view with another
 194                  * temporary view, and similarly for permanent views.
 195                  */
 196                 Assert(relation->relpersistence == rel->rd_rel->relpersistence);
 197
 198                 /*
 199                  * Create a tuple descriptor to compare against the existing view, and
 200                  * verify that the old column list is an initial prefix of the new
 201                  * column list.
 202                  */
 203                 descriptor = BuildDescForRelation(attrList);
 204                 checkViewTupleDesc(descriptor, rel->rd_att);
 205
 206                 /*
 207                  * If new attributes have been added, we must add pg_attribute entries
 208                  * for them.  It is convenient (although overkill) to use the ALTER
 209                  * TABLE ADD COLUMN infrastructure for this.
 210                  */
 211                 if (list_length(attrList) > rel->rd_att->natts)
 212                 {
 213                         List       *atcmds = NIL;
 214                         ListCell   *c;
 215                         int                     skip = rel->rd_att->natts;
 216
 217                         foreach(c, attrList)
 218                         {
 219                                 AlterTableCmd *atcmd;
 220
 221                                 if (skip > 0)
 222                                 {
 223                                         skip--;
 224                                         continue;
 225                                 }
 226                                 atcmd = makeNode(AlterTableCmd);
 227                                 atcmd->subtype = AT_AddColumnToView;
 228                                 atcmd->def = (Node *) lfirst(c);
 229                                 atcmds = lappend(atcmds, atcmd);
 230                         }
 231                         AlterTableInternal(viewOid, atcmds, true);
 232                 }
 233
 234                 /*
 235                  * Seems okay, so return the OID of the pre-existing view.
 236                  */
 237                 relation_close(rel, NoLock);    /* keep the lock! */
 238
 239                 return viewOid;
 240         }
 241         else
 242         {
 243                 Oid             relid;
 244
 245                 /*
 246                  * now set the parameters for keys/inheritance etc. All of these are
 247                  * uninteresting for views...
 248                  */
 249                 createStmt->relation = (RangeVar *) relation;
 250                 createStmt->tableElts = attrList;
 251                 createStmt->inhRelations = NIL;
 252                 createStmt->constraints = NIL;
 253                 createStmt->options = list_make1(defWithOids(false));
 254                 createStmt->oncommit = ONCOMMIT_NOOP;
 255                 createStmt->tablespacename = NULL;
 256                 createStmt->if_not_exists = false;
 257
 258                 /*
 259                  * finally create the relation (this will error out if there's an
 260                  * existing view, so we don't need more code to complain if "replace"
 261                  * is false).
 262                  */
 263                 relid = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid);
 264                 Assert(relid != InvalidOid);
 265                 return relid;
 266         }
 267 }
 268
 269 /*
 270  * Verify that tupledesc associated with proposed new view definition
 271  * matches tupledesc of old view.  This is basically a cut-down version
 272  * of equalTupleDescs(), with code added to generate specific complaints.
 273  * Also, we allow the new tupledesc to have more columns than the old.
 274  */
 275 static void
 276 checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc)
 277 {
 278         int                     i;
 279
 280         if (newdesc->natts < olddesc->natts)
 281                 ereport(ERROR,
 282                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 283                                  errmsg("cannot drop columns from view")));
 284         /* we can ignore tdhasoid */
 285
 286         for (i = 0; i < olddesc->natts; i++)
 287         {
 288                 Form_pg_attribute newattr = newdesc->attrs[i];
 289                 Form_pg_attribute oldattr = olddesc->attrs[i];
 290
 291                 /* XXX msg not right, but we don't support DROP COL on view anyway */
 292                 if (newattr->attisdropped != oldattr->attisdropped)
 293                         ereport(ERROR,
 294                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 295                                          errmsg("cannot drop columns from view")));
 296
 297                 if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0)
 298                         ereport(ERROR,
 299                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 300                                  errmsg("cannot change name of view column \"%s\" to \"%s\"",
 301                                                 NameStr(oldattr->attname),
 302                                                 NameStr(newattr->attname))));
 303                 /* XXX would it be safe to allow atttypmod to change?  Not sure */
 304                 if (newattr->atttypid != oldattr->atttypid ||
 305                         newattr->atttypmod != oldattr->atttypmod)
 306                         ereport(ERROR,
 307                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 308                                          errmsg("cannot change data type of view column \"%s\" from %s to %s",
 309                                                         NameStr(oldattr->attname),
 310                                                         format_type_with_typemod(oldattr->atttypid,
 311                                                                                                          oldattr->atttypmod),
 312                                                         format_type_with_typemod(newattr->atttypid,
 313                                                                                                          newattr->atttypmod))));
 314                 /* We can ignore the remaining attributes of an attribute... */
 315         }
 316
 317         /*
 318          * We ignore the constraint fields.  The new view desc can't have any
 319          * constraints, and the only ones that could be on the old view are
 320          * defaults, which we are happy to leave in place.
 321          */
 322 }
 323
 324 static void
 325 DefineViewRules(Oid viewOid, Query *viewParse, bool replace)
 326 {
 327         /*
 328          * Set up the ON SELECT rule.  Since the query has already been through
 329          * parse analysis, we use DefineQueryRewrite() directly.
 330          */
 331         DefineQueryRewrite(pstrdup(ViewSelectRuleName),
 332                                            viewOid,
 333                                            NULL,
 334                                            CMD_SELECT,
 335                                            true,
 336                                            replace,
 337                                            list_make1(viewParse));
 338
 339         /*
 340          * Someday: automatic ON INSERT, etc
 341          */
 342 }
 343
 344 /*---------------------------------------------------------------
 345  * UpdateRangeTableOfViewParse
 346  *
 347  * Update the range table of the given parsetree.
 348  * This update consists of adding two new entries IN THE BEGINNING
 349  * of the range table (otherwise the rule system will die a slow,
 350  * horrible and painful death, and we do not want that now, do we?)
 351  * one for the OLD relation and one for the NEW one (both of
 352  * them refer in fact to the "view" relation).
 353  *
 354  * Of course we must also increase the 'varnos' of all the Var nodes
 355  * by 2...
 356  *
 357  * These extra RT entries are not actually used in the query,
 358  * except for run-time permission checking.
 359  *---------------------------------------------------------------
 360  */
 361 static Query *
 362 UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse)
 363 {
 364         Relation        viewRel;
 365         List       *new_rt;
 366         RangeTblEntry *rt_entry1,
 367                            *rt_entry2;
 368
 369         /*
 370          * Make a copy of the given parsetree.  It's not so much that we don't
 371          * want to scribble on our input, it's that the parser has a bad habit of
 372          * outputting multiple links to the same subtree for constructs like
 373          * BETWEEN, and we mustn't have OffsetVarNodes increment the varno of a
 374          * Var node twice.      copyObject will expand any multiply-referenced subtree
 375          * into multiple copies.
 376          */
 377         viewParse = (Query *) copyObject(viewParse);
 378
 379         /* need to open the rel for addRangeTableEntryForRelation */
 380         viewRel = relation_open(viewOid, AccessShareLock);
 381
 382         /*
 383          * Create the 2 new range table entries and form the new range table...
 384          * OLD first, then NEW....
 385          */
 386         rt_entry1 = addRangeTableEntryForRelation(NULL, viewRel,
 387                                                                                           makeAlias("old", NIL),
 388                                                                                           false, false);
 389         rt_entry2 = addRangeTableEntryForRelation(NULL, viewRel,
 390                                                                                           makeAlias("new", NIL),
 391                                                                                           false, false);
 392         /* Must override addRangeTableEntry's default access-check flags */
 393         rt_entry1->requiredPerms = 0;
 394         rt_entry2->requiredPerms = 0;
 395
 396         new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable));
 397
 398         viewParse->rtable = new_rt;
 399
 400         /*
 401          * Now offset all var nodes by 2, and jointree RT indexes too.
 402          */
 403         OffsetVarNodes((Node *) viewParse, 2, 0);
 404
 405         relation_close(viewRel, AccessShareLock);
 406
 407         return viewParse;
 408 }
 409
 410 /*
 411  * DefineView
 412  *              Execute a CREATE VIEW command.
 413  */
 414 void
 415 DefineView(ViewStmt *stmt, const char *queryString)
 416 {
 417         Query      *viewParse;
 418         Oid                     viewOid;
 419         RangeVar   *view;
 420
 421         /*
 422          * Run parse analysis to convert the raw parse tree to a Query.  Note this
 423          * also acquires sufficient locks on the source table(s).
 424          *
 425          * Since parse analysis scribbles on its input, copy the raw parse tree;
 426          * this ensures we don't corrupt a prepared statement, for example.
 427          */
 428         viewParse = parse_analyze((Node *) copyObject(stmt->query),
 429                                                           queryString, NULL, 0);
 430
 431         /*
 432          * The grammar should ensure that the result is a single SELECT Query.
 433          */
 434         if (!IsA(viewParse, Query) ||
 435                 viewParse->commandType != CMD_SELECT)
 436                 elog(ERROR, "unexpected parse analysis result");
 437
 438         /*
 439          * Check for unsupported cases.  These tests are redundant with ones in
 440          * DefineQueryRewrite(), but that function will complain about a bogus
 441          * ON SELECT rule, and we'd rather the message complain about a view.
 442          */
 443         if (viewParse->intoClause != NULL)
 444                 ereport(ERROR,
 445                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 446                                  errmsg("views must not contain SELECT INTO")));
 447         if (viewParse->hasModifyingCTE)
 448                 ereport(ERROR,
 449                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 450                                  errmsg("views must not contain data-modifying statements in WITH")));
 451
 452         /*
 453          * If a list of column names was given, run through and insert these into
 454          * the actual query tree. - thomas 2000-03-08
 455          */
 456         if (stmt->aliases != NIL)
 457         {
 458                 ListCell   *alist_item = list_head(stmt->aliases);
 459                 ListCell   *targetList;
 460
 461                 foreach(targetList, viewParse->targetList)
 462                 {
 463                         TargetEntry *te = (TargetEntry *) lfirst(targetList);
 464
 465                         Assert(IsA(te, TargetEntry));
 466                         /* junk columns don't get aliases */
 467                         if (te->resjunk)
 468                                 continue;
 469                         te->resname = pstrdup(strVal(lfirst(alist_item)));
 470                         alist_item = lnext(alist_item);
 471                         if (alist_item == NULL)
 472                                 break;                  /* done assigning aliases */
 473                 }
 474
 475                 if (alist_item != NULL)
 476                         ereport(ERROR,
 477                                         (errcode(ERRCODE_SYNTAX_ERROR),
 478                                          errmsg("CREATE VIEW specifies more column "
 479                                                         "names than columns")));
 480         }
 481
 482         /*
 483          * If the user didn't explicitly ask for a temporary view, check whether
 484          * we need one implicitly.      We allow TEMP to be inserted automatically as
 485          * long as the CREATE command is consistent with that --- no explicit
 486          * schema name.
 487          */
 488         view = stmt->view;
 489         if (view->relpersistence == RELPERSISTENCE_PERMANENT
 490                 && isViewOnTempTable(viewParse))
 491         {
 492                 view = copyObject(view);        /* don't corrupt original command */
 493                 view->relpersistence = RELPERSISTENCE_TEMP;
 494                 ereport(NOTICE,
 495                                 (errmsg("view \"%s\" will be a temporary view",
 496                                                 view->relname)));
 497         }
 498
 499         /* Unlogged views are not sensible. */
 500         if (view->relpersistence == RELPERSISTENCE_UNLOGGED)
 501                 ereport(ERROR,
 502                                 (errcode(ERRCODE_SYNTAX_ERROR),
 503                                  errmsg("views cannot be unlogged because they do not have storage")));
 504
 505         /*
 506          * Create the view relation
 507          *
 508          * NOTE: if it already exists and replace is false, the xact will be
 509          * aborted.
 510          */
 511         viewOid = DefineVirtualRelation(view, viewParse->targetList,
 512                                                                         stmt->replace);
 513
 514         /*
 515          * The relation we have just created is not visible to any other commands
 516          * running with the same transaction & command id. So, increment the
 517          * command id counter (but do NOT pfree any memory!!!!)
 518          */
 519         CommandCounterIncrement();
 520
 521         /*
 522          * The range table of 'viewParse' does not contain entries for the "OLD"
 523          * and "NEW" relations. So... add them!
 524          */
 525         viewParse = UpdateRangeTableOfViewParse(viewOid, viewParse);
 526
 527         /*
 528          * Now create the rules associated with the view.
 529          */
 530         DefineViewRules(viewOid, viewParse, stmt->replace);
 531 }