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                         /*
 135                          * It's possible that the column is of a collatable type but the
 136                          * collation could not be resolved, so double-check.
 137                          */
 138                         if (type_is_collatable(exprType((Node *) tle->expr)))
 139                         {
 140                                 if (!OidIsValid(def->collOid))
 141                                         ereport(ERROR,
 142                                                         (errcode(ERRCODE_INDETERMINATE_COLLATION),
 143                                                          errmsg("could not determine which collation to use for view column \"%s\"",
 144                                                                         def->colname),
 145                                                          errhint("Use the COLLATE clause to set the collation explicitly.")));
 146                         }
 147                         else
 148                                 Assert(!OidIsValid(def->collOid));
 149                         def->constraints = NIL;
 150
 151                         attrList = lappend(attrList, def);
 152                 }
 153         }
 154
 155         if (attrList == NIL)
 156                 ereport(ERROR,
 157                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 158                                  errmsg("view must have at least one column")));
 159
 160         /*
 161          * Check to see if we want to replace an existing view.
 162          */
 163         namespaceId = RangeVarGetCreationNamespace(relation);
 164         viewOid = get_relname_relid(relation->relname, namespaceId);
 165
 166         if (OidIsValid(viewOid) && replace)
 167         {
 168                 Relation        rel;
 169                 TupleDesc       descriptor;
 170
 171                 /*
 172                  * Yes.  Get exclusive lock on the existing view ...
 173                  */
 174                 rel = relation_open(viewOid, AccessExclusiveLock);
 175
 176                 /*
 177                  * Make sure it *is* a view, and do permissions checks.
 178                  */
 179                 if (rel->rd_rel->relkind != RELKIND_VIEW)
 180                         ereport(ERROR,
 181                                         (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 182                                          errmsg("\"%s\" is not a view",
 183                                                         RelationGetRelationName(rel))));
 184
 185                 if (!pg_class_ownercheck(viewOid, GetUserId()))
 186                         aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
 187                                                    RelationGetRelationName(rel));
 188
 189                 /* Also check it's not in use already */
 190                 CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW");
 191
 192                 /*
 193                  * Due to the namespace visibility rules for temporary objects, we
 194                  * should only end up replacing a temporary view with another
 195                  * temporary view, and similarly for permanent views.
 196                  */
 197                 Assert(relation->relpersistence == rel->rd_rel->relpersistence);
 198
 199                 /*
 200                  * Create a tuple descriptor to compare against the existing view, and
 201                  * verify that the old column list is an initial prefix of the new
 202                  * column list.
 203                  */
 204                 descriptor = BuildDescForRelation(attrList);
 205                 checkViewTupleDesc(descriptor, rel->rd_att);
 206
 207                 /*
 208                  * If new attributes have been added, we must add pg_attribute entries
 209                  * for them.  It is convenient (although overkill) to use the ALTER
 210                  * TABLE ADD COLUMN infrastructure for this.
 211                  */
 212                 if (list_length(attrList) > rel->rd_att->natts)
 213                 {
 214                         List       *atcmds = NIL;
 215                         ListCell   *c;
 216                         int                     skip = rel->rd_att->natts;
 217
 218                         foreach(c, attrList)
 219                         {
 220                                 AlterTableCmd *atcmd;
 221
 222                                 if (skip > 0)
 223                                 {
 224                                         skip--;
 225                                         continue;
 226                                 }
 227                                 atcmd = makeNode(AlterTableCmd);
 228                                 atcmd->subtype = AT_AddColumnToView;
 229                                 atcmd->def = (Node *) lfirst(c);
 230                                 atcmds = lappend(atcmds, atcmd);
 231                         }
 232                         AlterTableInternal(viewOid, atcmds, true);
 233                 }
 234
 235                 /*
 236                  * Seems okay, so return the OID of the pre-existing view.
 237                  */
 238                 relation_close(rel, NoLock);    /* keep the lock! */
 239
 240                 return viewOid;
 241         }
 242         else
 243         {
 244                 Oid                     relid;
 245
 246                 /*
 247                  * now set the parameters for keys/inheritance etc. All of these are
 248                  * uninteresting for views...
 249                  */
 250                 createStmt->relation = (RangeVar *) relation;
 251                 createStmt->tableElts = attrList;
 252                 createStmt->inhRelations = NIL;
 253                 createStmt->constraints = NIL;
 254                 createStmt->options = list_make1(defWithOids(false));
 255                 createStmt->oncommit = ONCOMMIT_NOOP;
 256                 createStmt->tablespacename = NULL;
 257                 createStmt->if_not_exists = false;
 258
 259                 /*
 260                  * finally create the relation (this will error out if there's an
 261                  * existing view, so we don't need more code to complain if "replace"
 262                  * is false).
 263                  */
 264                 relid = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid);
 265                 Assert(relid != InvalidOid);
 266                 return relid;
 267         }
 268 }
 269
 270 /*
 271  * Verify that tupledesc associated with proposed new view definition
 272  * matches tupledesc of old view.  This is basically a cut-down version
 273  * of equalTupleDescs(), with code added to generate specific complaints.
 274  * Also, we allow the new tupledesc to have more columns than the old.
 275  */
 276 static void
 277 checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc)
 278 {
 279         int                     i;
 280
 281         if (newdesc->natts < olddesc->natts)
 282                 ereport(ERROR,
 283                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 284                                  errmsg("cannot drop columns from view")));
 285         /* we can ignore tdhasoid */
 286
 287         for (i = 0; i < olddesc->natts; i++)
 288         {
 289                 Form_pg_attribute newattr = newdesc->attrs[i];
 290                 Form_pg_attribute oldattr = olddesc->attrs[i];
 291
 292                 /* XXX msg not right, but we don't support DROP COL on view anyway */
 293                 if (newattr->attisdropped != oldattr->attisdropped)
 294                         ereport(ERROR,
 295                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 296                                          errmsg("cannot drop columns from view")));
 297
 298                 if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0)
 299                         ereport(ERROR,
 300                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 301                                  errmsg("cannot change name of view column \"%s\" to \"%s\"",
 302                                                 NameStr(oldattr->attname),
 303                                                 NameStr(newattr->attname))));
 304                 /* XXX would it be safe to allow atttypmod to change?  Not sure */
 305                 if (newattr->atttypid != oldattr->atttypid ||
 306                         newattr->atttypmod != oldattr->atttypmod)
 307                         ereport(ERROR,
 308                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 309                                          errmsg("cannot change data type of view column \"%s\" from %s to %s",
 310                                                         NameStr(oldattr->attname),
 311                                                         format_type_with_typemod(oldattr->atttypid,
 312                                                                                                          oldattr->atttypmod),
 313                                                         format_type_with_typemod(newattr->atttypid,
 314                                                                                                          newattr->atttypmod))));
 315                 /* We can ignore the remaining attributes of an attribute... */
 316         }
 317
 318         /*
 319          * We ignore the constraint fields.  The new view desc can't have any
 320          * constraints, and the only ones that could be on the old view are
 321          * defaults, which we are happy to leave in place.
 322          */
 323 }
 324
 325 static void
 326 DefineViewRules(Oid viewOid, Query *viewParse, bool replace)
 327 {
 328         /*
 329          * Set up the ON SELECT rule.  Since the query has already been through
 330          * parse analysis, we use DefineQueryRewrite() directly.
 331          */
 332         DefineQueryRewrite(pstrdup(ViewSelectRuleName),
 333                                            viewOid,
 334                                            NULL,
 335                                            CMD_SELECT,
 336                                            true,
 337                                            replace,
 338                                            list_make1(viewParse));
 339
 340         /*
 341          * Someday: automatic ON INSERT, etc
 342          */
 343 }
 344
 345 /*---------------------------------------------------------------
 346  * UpdateRangeTableOfViewParse
 347  *
 348  * Update the range table of the given parsetree.
 349  * This update consists of adding two new entries IN THE BEGINNING
 350  * of the range table (otherwise the rule system will die a slow,
 351  * horrible and painful death, and we do not want that now, do we?)
 352  * one for the OLD relation and one for the NEW one (both of
 353  * them refer in fact to the "view" relation).
 354  *
 355  * Of course we must also increase the 'varnos' of all the Var nodes
 356  * by 2...
 357  *
 358  * These extra RT entries are not actually used in the query,
 359  * except for run-time permission checking.
 360  *---------------------------------------------------------------
 361  */
 362 static Query *
 363 UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse)
 364 {
 365         Relation        viewRel;
 366         List       *new_rt;
 367         RangeTblEntry *rt_entry1,
 368                            *rt_entry2;
 369
 370         /*
 371          * Make a copy of the given parsetree.  It's not so much that we don't
 372          * want to scribble on our input, it's that the parser has a bad habit of
 373          * outputting multiple links to the same subtree for constructs like
 374          * BETWEEN, and we mustn't have OffsetVarNodes increment the varno of a
 375          * Var node twice.      copyObject will expand any multiply-referenced subtree
 376          * into multiple copies.
 377          */
 378         viewParse = (Query *) copyObject(viewParse);
 379
 380         /* need to open the rel for addRangeTableEntryForRelation */
 381         viewRel = relation_open(viewOid, AccessShareLock);
 382
 383         /*
 384          * Create the 2 new range table entries and form the new range table...
 385          * OLD first, then NEW....
 386          */
 387         rt_entry1 = addRangeTableEntryForRelation(NULL, viewRel,
 388                                                                                           makeAlias("old", NIL),
 389                                                                                           false, false);
 390         rt_entry2 = addRangeTableEntryForRelation(NULL, viewRel,
 391                                                                                           makeAlias("new", NIL),
 392                                                                                           false, false);
 393         /* Must override addRangeTableEntry's default access-check flags */
 394         rt_entry1->requiredPerms = 0;
 395         rt_entry2->requiredPerms = 0;
 396
 397         new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable));
 398
 399         viewParse->rtable = new_rt;
 400
 401         /*
 402          * Now offset all var nodes by 2, and jointree RT indexes too.
 403          */
 404         OffsetVarNodes((Node *) viewParse, 2, 0);
 405
 406         relation_close(viewRel, AccessShareLock);
 407
 408         return viewParse;
 409 }
 410
 411 /*
 412  * DefineView
 413  *              Execute a CREATE VIEW command.
 414  */
 415 void
 416 DefineView(ViewStmt *stmt, const char *queryString)
 417 {
 418         Query      *viewParse;
 419         Oid                     viewOid;
 420         RangeVar   *view;
 421
 422         /*
 423          * Run parse analysis to convert the raw parse tree to a Query.  Note this
 424          * also acquires sufficient locks on the source table(s).
 425          *
 426          * Since parse analysis scribbles on its input, copy the raw parse tree;
 427          * this ensures we don't corrupt a prepared statement, for example.
 428          */
 429         viewParse = parse_analyze((Node *) copyObject(stmt->query),
 430                                                           queryString, NULL, 0);
 431
 432         /*
 433          * The grammar should ensure that the result is a single SELECT Query.
 434          */
 435         if (!IsA(viewParse, Query) ||
 436                 viewParse->commandType != CMD_SELECT)
 437                 elog(ERROR, "unexpected parse analysis result");
 438
 439         /*
 440          * Check for unsupported cases.  These tests are redundant with ones in
 441          * DefineQueryRewrite(), but that function will complain about a bogus ON
 442          * SELECT rule, and we'd rather the message complain about a view.
 443          */
 444         if (viewParse->intoClause != NULL)
 445                 ereport(ERROR,
 446                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 447                                  errmsg("views must not contain SELECT INTO")));
 448         if (viewParse->hasModifyingCTE)
 449                 ereport(ERROR,
 450                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 451                 errmsg("views must not contain data-modifying statements in WITH")));
 452
 453         /*
 454          * If a list of column names was given, run through and insert these into
 455          * the actual query tree. - thomas 2000-03-08
 456          */
 457         if (stmt->aliases != NIL)
 458         {
 459                 ListCell   *alist_item = list_head(stmt->aliases);
 460                 ListCell   *targetList;
 461
 462                 foreach(targetList, viewParse->targetList)
 463                 {
 464                         TargetEntry *te = (TargetEntry *) lfirst(targetList);
 465
 466                         Assert(IsA(te, TargetEntry));
 467                         /* junk columns don't get aliases */
 468                         if (te->resjunk)
 469                                 continue;
 470                         te->resname = pstrdup(strVal(lfirst(alist_item)));
 471                         alist_item = lnext(alist_item);
 472                         if (alist_item == NULL)
 473                                 break;                  /* done assigning aliases */
 474                 }
 475
 476                 if (alist_item != NULL)
 477                         ereport(ERROR,
 478                                         (errcode(ERRCODE_SYNTAX_ERROR),
 479                                          errmsg("CREATE VIEW specifies more column "
 480                                                         "names than columns")));
 481         }
 482
 483         /*
 484          * If the user didn't explicitly ask for a temporary view, check whether
 485          * we need one implicitly.      We allow TEMP to be inserted automatically as
 486          * long as the CREATE command is consistent with that --- no explicit
 487          * schema name.
 488          */
 489         view = stmt->view;
 490         if (view->relpersistence == RELPERSISTENCE_PERMANENT
 491                 && isViewOnTempTable(viewParse))
 492         {
 493                 view = copyObject(view);        /* don't corrupt original command */
 494                 view->relpersistence = RELPERSISTENCE_TEMP;
 495                 ereport(NOTICE,
 496                                 (errmsg("view \"%s\" will be a temporary view",
 497                                                 view->relname)));
 498         }
 499
 500         /* Unlogged views are not sensible. */
 501         if (view->relpersistence == RELPERSISTENCE_UNLOGGED)
 502                 ereport(ERROR,
 503                                 (errcode(ERRCODE_SYNTAX_ERROR),
 504                 errmsg("views cannot be unlogged because they do not have storage")));
 505
 506         /*
 507          * Create the view relation
 508          *
 509          * NOTE: if it already exists and replace is false, the xact will be
 510          * aborted.
 511          */
 512         viewOid = DefineVirtualRelation(view, viewParse->targetList,
 513                                                                         stmt->replace);
 514
 515         /*
 516          * The relation we have just created is not visible to any other commands
 517          * running with the same transaction & command id. So, increment the
 518          * command id counter (but do NOT pfree any memory!!!!)
 519          */
 520         CommandCounterIncrement();
 521
 522         /*
 523          * The range table of 'viewParse' does not contain entries for the "OLD"
 524          * and "NEW" relations. So... add them!
 525          */
 526         viewParse = UpdateRangeTableOfViewParse(viewOid, viewParse);
 527
 528         /*
 529          * Now create the rules associated with the view.
 530          */
 531         DefineViewRules(viewOid, viewParse, stmt->replace);
 532 }