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->storage = 0;
 128                         def->raw_default = NULL;
 129                         def->cooked_default = NULL;
 130                         def->constraints = NIL;
 131
 132                         attrList = lappend(attrList, def);
 133                 }
 134         }
 135
 136         if (attrList == NIL)
 137                 ereport(ERROR,
 138                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 139                                  errmsg("view must have at least one column")));
 140
 141         /*
 142          * Check to see if we want to replace an existing view.
 143          */
 144         namespaceId = RangeVarGetCreationNamespace(relation);
 145         viewOid = get_relname_relid(relation->relname, namespaceId);
 146
 147         if (OidIsValid(viewOid) && replace)
 148         {
 149                 Relation        rel;
 150                 TupleDesc       descriptor;
 151
 152                 /*
 153                  * Yes.  Get exclusive lock on the existing view ...
 154                  */
 155                 rel = relation_open(viewOid, AccessExclusiveLock);
 156
 157                 /*
 158                  * Make sure it *is* a view, and do permissions checks.
 159                  */
 160                 if (rel->rd_rel->relkind != RELKIND_VIEW)
 161                         ereport(ERROR,
 162                                         (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 163                                          errmsg("\"%s\" is not a view",
 164                                                         RelationGetRelationName(rel))));
 165
 166                 if (!pg_class_ownercheck(viewOid, GetUserId()))
 167                         aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
 168                                                    RelationGetRelationName(rel));
 169
 170                 /* Also check it's not in use already */
 171                 CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW");
 172
 173                 /*
 174                  * Due to the namespace visibility rules for temporary objects, we
 175                  * should only end up replacing a temporary view with another
 176                  * temporary view, and similarly for permanent views.
 177                  */
 178                 Assert(relation->relpersistence == rel->rd_rel->relpersistence);
 179
 180                 /*
 181                  * Create a tuple descriptor to compare against the existing view, and
 182                  * verify that the old column list is an initial prefix of the new
 183                  * column list.
 184                  */
 185                 descriptor = BuildDescForRelation(attrList);
 186                 checkViewTupleDesc(descriptor, rel->rd_att);
 187
 188                 /*
 189                  * If new attributes have been added, we must add pg_attribute entries
 190                  * for them.  It is convenient (although overkill) to use the ALTER
 191                  * TABLE ADD COLUMN infrastructure for this.
 192                  */
 193                 if (list_length(attrList) > rel->rd_att->natts)
 194                 {
 195                         List       *atcmds = NIL;
 196                         ListCell   *c;
 197                         int                     skip = rel->rd_att->natts;
 198
 199                         foreach(c, attrList)
 200                         {
 201                                 AlterTableCmd *atcmd;
 202
 203                                 if (skip > 0)
 204                                 {
 205                                         skip--;
 206                                         continue;
 207                                 }
 208                                 atcmd = makeNode(AlterTableCmd);
 209                                 atcmd->subtype = AT_AddColumnToView;
 210                                 atcmd->def = (Node *) lfirst(c);
 211                                 atcmds = lappend(atcmds, atcmd);
 212                         }
 213                         AlterTableInternal(viewOid, atcmds, true);
 214                 }
 215
 216                 /*
 217                  * Seems okay, so return the OID of the pre-existing view.
 218                  */
 219                 relation_close(rel, NoLock);    /* keep the lock! */
 220
 221                 return viewOid;
 222         }
 223         else
 224         {
 225                 Oid             relid;
 226
 227                 /*
 228                  * now set the parameters for keys/inheritance etc. All of these are
 229                  * uninteresting for views...
 230                  */
 231                 createStmt->relation = (RangeVar *) relation;
 232                 createStmt->tableElts = attrList;
 233                 createStmt->inhRelations = NIL;
 234                 createStmt->constraints = NIL;
 235                 createStmt->options = list_make1(defWithOids(false));
 236                 createStmt->oncommit = ONCOMMIT_NOOP;
 237                 createStmt->tablespacename = NULL;
 238                 createStmt->if_not_exists = false;
 239
 240                 /*
 241                  * finally create the relation (this will error out if there's an
 242                  * existing view, so we don't need more code to complain if "replace"
 243                  * is false).
 244                  */
 245                 relid = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid);
 246                 Assert(relid != InvalidOid);
 247                 return relid;
 248         }
 249 }
 250
 251 /*
 252  * Verify that tupledesc associated with proposed new view definition
 253  * matches tupledesc of old view.  This is basically a cut-down version
 254  * of equalTupleDescs(), with code added to generate specific complaints.
 255  * Also, we allow the new tupledesc to have more columns than the old.
 256  */
 257 static void
 258 checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc)
 259 {
 260         int                     i;
 261
 262         if (newdesc->natts < olddesc->natts)
 263                 ereport(ERROR,
 264                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 265                                  errmsg("cannot drop columns from view")));
 266         /* we can ignore tdhasoid */
 267
 268         for (i = 0; i < olddesc->natts; i++)
 269         {
 270                 Form_pg_attribute newattr = newdesc->attrs[i];
 271                 Form_pg_attribute oldattr = olddesc->attrs[i];
 272
 273                 /* XXX msg not right, but we don't support DROP COL on view anyway */
 274                 if (newattr->attisdropped != oldattr->attisdropped)
 275                         ereport(ERROR,
 276                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 277                                          errmsg("cannot drop columns from view")));
 278
 279                 if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0)
 280                         ereport(ERROR,
 281                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 282                                  errmsg("cannot change name of view column \"%s\" to \"%s\"",
 283                                                 NameStr(oldattr->attname),
 284                                                 NameStr(newattr->attname))));
 285                 /* XXX would it be safe to allow atttypmod to change?  Not sure */
 286                 if (newattr->atttypid != oldattr->atttypid ||
 287                         newattr->atttypmod != oldattr->atttypmod)
 288                         ereport(ERROR,
 289                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 290                                          errmsg("cannot change data type of view column \"%s\" from %s to %s",
 291                                                         NameStr(oldattr->attname),
 292                                                         format_type_with_typemod(oldattr->atttypid,
 293                                                                                                          oldattr->atttypmod),
 294                                                         format_type_with_typemod(newattr->atttypid,
 295                                                                                                          newattr->atttypmod))));
 296                 /* We can ignore the remaining attributes of an attribute... */
 297         }
 298
 299         /*
 300          * We ignore the constraint fields.  The new view desc can't have any
 301          * constraints, and the only ones that could be on the old view are
 302          * defaults, which we are happy to leave in place.
 303          */
 304 }
 305
 306 static void
 307 DefineViewRules(Oid viewOid, Query *viewParse, bool replace)
 308 {
 309         /*
 310          * Set up the ON SELECT rule.  Since the query has already been through
 311          * parse analysis, we use DefineQueryRewrite() directly.
 312          */
 313         DefineQueryRewrite(pstrdup(ViewSelectRuleName),
 314                                            viewOid,
 315                                            NULL,
 316                                            CMD_SELECT,
 317                                            true,
 318                                            replace,
 319                                            list_make1(viewParse));
 320
 321         /*
 322          * Someday: automatic ON INSERT, etc
 323          */
 324 }
 325
 326 /*---------------------------------------------------------------
 327  * UpdateRangeTableOfViewParse
 328  *
 329  * Update the range table of the given parsetree.
 330  * This update consists of adding two new entries IN THE BEGINNING
 331  * of the range table (otherwise the rule system will die a slow,
 332  * horrible and painful death, and we do not want that now, do we?)
 333  * one for the OLD relation and one for the NEW one (both of
 334  * them refer in fact to the "view" relation).
 335  *
 336  * Of course we must also increase the 'varnos' of all the Var nodes
 337  * by 2...
 338  *
 339  * These extra RT entries are not actually used in the query,
 340  * except for run-time permission checking.
 341  *---------------------------------------------------------------
 342  */
 343 static Query *
 344 UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse)
 345 {
 346         Relation        viewRel;
 347         List       *new_rt;
 348         RangeTblEntry *rt_entry1,
 349                            *rt_entry2;
 350
 351         /*
 352          * Make a copy of the given parsetree.  It's not so much that we don't
 353          * want to scribble on our input, it's that the parser has a bad habit of
 354          * outputting multiple links to the same subtree for constructs like
 355          * BETWEEN, and we mustn't have OffsetVarNodes increment the varno of a
 356          * Var node twice.      copyObject will expand any multiply-referenced subtree
 357          * into multiple copies.
 358          */
 359         viewParse = (Query *) copyObject(viewParse);
 360
 361         /* need to open the rel for addRangeTableEntryForRelation */
 362         viewRel = relation_open(viewOid, AccessShareLock);
 363
 364         /*
 365          * Create the 2 new range table entries and form the new range table...
 366          * OLD first, then NEW....
 367          */
 368         rt_entry1 = addRangeTableEntryForRelation(NULL, viewRel,
 369                                                                                           makeAlias("old", NIL),
 370                                                                                           false, false);
 371         rt_entry2 = addRangeTableEntryForRelation(NULL, viewRel,
 372                                                                                           makeAlias("new", NIL),
 373                                                                                           false, false);
 374         /* Must override addRangeTableEntry's default access-check flags */
 375         rt_entry1->requiredPerms = 0;
 376         rt_entry2->requiredPerms = 0;
 377
 378         new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable));
 379
 380         viewParse->rtable = new_rt;
 381
 382         /*
 383          * Now offset all var nodes by 2, and jointree RT indexes too.
 384          */
 385         OffsetVarNodes((Node *) viewParse, 2, 0);
 386
 387         relation_close(viewRel, AccessShareLock);
 388
 389         return viewParse;
 390 }
 391
 392 /*
 393  * DefineView
 394  *              Execute a CREATE VIEW command.
 395  */
 396 void
 397 DefineView(ViewStmt *stmt, const char *queryString)
 398 {
 399         Query      *viewParse;
 400         Oid                     viewOid;
 401         RangeVar   *view;
 402
 403         /*
 404          * Run parse analysis to convert the raw parse tree to a Query.  Note this
 405          * also acquires sufficient locks on the source table(s).
 406          *
 407          * Since parse analysis scribbles on its input, copy the raw parse tree;
 408          * this ensures we don't corrupt a prepared statement, for example.
 409          */
 410         viewParse = parse_analyze((Node *) copyObject(stmt->query),
 411                                                           queryString, NULL, 0);
 412
 413         /*
 414          * The grammar should ensure that the result is a single SELECT Query.
 415          */
 416         if (!IsA(viewParse, Query) ||
 417                 viewParse->commandType != CMD_SELECT)
 418                 elog(ERROR, "unexpected parse analysis result");
 419
 420         /*
 421          * If a list of column names was given, run through and insert these into
 422          * the actual query tree. - thomas 2000-03-08
 423          */
 424         if (stmt->aliases != NIL)
 425         {
 426                 ListCell   *alist_item = list_head(stmt->aliases);
 427                 ListCell   *targetList;
 428
 429                 foreach(targetList, viewParse->targetList)
 430                 {
 431                         TargetEntry *te = (TargetEntry *) lfirst(targetList);
 432
 433                         Assert(IsA(te, TargetEntry));
 434                         /* junk columns don't get aliases */
 435                         if (te->resjunk)
 436                                 continue;
 437                         te->resname = pstrdup(strVal(lfirst(alist_item)));
 438                         alist_item = lnext(alist_item);
 439                         if (alist_item == NULL)
 440                                 break;                  /* done assigning aliases */
 441                 }
 442
 443                 if (alist_item != NULL)
 444                         ereport(ERROR,
 445                                         (errcode(ERRCODE_SYNTAX_ERROR),
 446                                          errmsg("CREATE VIEW specifies more column "
 447                                                         "names than columns")));
 448         }
 449
 450         /*
 451          * If the user didn't explicitly ask for a temporary view, check whether
 452          * we need one implicitly.      We allow TEMP to be inserted automatically as
 453          * long as the CREATE command is consistent with that --- no explicit
 454          * schema name.
 455          */
 456         view = stmt->view;
 457         if (view->relpersistence == RELPERSISTENCE_PERMANENT
 458                 && isViewOnTempTable(viewParse))
 459         {
 460                 view = copyObject(view);        /* don't corrupt original command */
 461                 view->relpersistence = RELPERSISTENCE_TEMP;
 462                 ereport(NOTICE,
 463                                 (errmsg("view \"%s\" will be a temporary view",
 464                                                 view->relname)));
 465         }
 466
 467         /*
 468          * Create the view relation
 469          *
 470          * NOTE: if it already exists and replace is false, the xact will be
 471          * aborted.
 472          */
 473         viewOid = DefineVirtualRelation(view, viewParse->targetList,
 474                                                                         stmt->replace);
 475
 476         /*
 477          * The relation we have just created is not visible to any other commands
 478          * running with the same transaction & command id. So, increment the
 479          * command id counter (but do NOT pfree any memory!!!!)
 480          */
 481         CommandCounterIncrement();
 482
 483         /*
 484          * The range table of 'viewParse' does not contain entries for the "OLD"
 485          * and "NEW" relations. So... add them!
 486          */
 487         viewParse = UpdateRangeTableOfViewParse(viewOid, viewParse);
 488
 489         /*
 490          * Now create the rules associated with the view.
 491          */
 492         DefineViewRules(viewOid, viewParse, stmt->replace);
 493 }