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