src/backend/commands/view.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * view.c
   4  *        use rewrite rules to construct views
   5  *
   6  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL: pgsql/src/backend/commands/view.c,v 1.114 2009/02/02 19:31:39 alvherre Exp $
  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                                 bool            istemp = rel->rd_istemp;
  72
  73                                 heap_close(rel, AccessShareLock);
  74                                 if (istemp)
  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->raw_default = NULL;
 128                         def->cooked_default = NULL;
 129                         def->constraints = NIL;
 130
 131                         attrList = lappend(attrList, def);
 132                 }
 133         }
 134
 135         if (attrList == NIL)
 136                 ereport(ERROR,
 137                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 138                                  errmsg("view must have at least one column")));
 139
 140         /*
 141          * Check to see if we want to replace an existing view.
 142          */
 143         namespaceId = RangeVarGetCreationNamespace(relation);
 144         viewOid = get_relname_relid(relation->relname, namespaceId);
 145
 146         if (OidIsValid(viewOid) && replace)
 147         {
 148                 Relation        rel;
 149                 TupleDesc       descriptor;
 150
 151                 /*
 152                  * Yes.  Get exclusive lock on the existing view ...
 153                  */
 154                 rel = relation_open(viewOid, AccessExclusiveLock);
 155
 156                 /*
 157                  * Make sure it *is* a view, and do permissions checks.
 158                  */
 159                 if (rel->rd_rel->relkind != RELKIND_VIEW)
 160                         ereport(ERROR,
 161                                         (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 162                                          errmsg("\"%s\" is not a view",
 163                                                         RelationGetRelationName(rel))));
 164
 165                 if (!pg_class_ownercheck(viewOid, GetUserId()))
 166                         aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
 167                                                    RelationGetRelationName(rel));
 168
 169                 /* Also check it's not in use already */
 170                 CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW");
 171
 172                 /*
 173                  * Due to the namespace visibility rules for temporary objects, we
 174                  * should only end up replacing a temporary view with another
 175                  * temporary view, and vice versa.
 176                  */
 177                 Assert(relation->istemp == rel->rd_istemp);
 178
 179                 /*
 180                  * Create a tuple descriptor to compare against the existing view, and
 181                  * verify that the old column list is an initial prefix of the new
 182                  * column list.
 183                  */
 184                 descriptor = BuildDescForRelation(attrList);
 185                 checkViewTupleDesc(descriptor, rel->rd_att);
 186
 187                 /*
 188                  * If new attributes have been added, we must add pg_attribute entries
 189                  * for them.  It is convenient (although overkill) to use the ALTER
 190                  * TABLE ADD COLUMN infrastructure for this.
 191                  */
 192                 if (list_length(attrList) > rel->rd_att->natts)
 193                 {
 194                         List            *atcmds = NIL;
 195                         ListCell        *c;
 196                         int                     skip = rel->rd_att->natts;
 197
 198                         foreach(c, attrList)
 199                         {
 200                                 AlterTableCmd *atcmd;
 201
 202                                 if (skip > 0)
 203                                 {
 204                                         skip--;
 205                                         continue;
 206                                 }
 207                                 atcmd = makeNode(AlterTableCmd);
 208                                 atcmd->subtype = AT_AddColumnToView;
 209                                 atcmd->def = (Node *) lfirst(c);
 210                                 atcmds = lappend(atcmds, atcmd);
 211                         }
 212                         AlterTableInternal(viewOid, atcmds, true);
 213                 }
 214
 215                 /*
 216                  * Seems okay, so return the OID of the pre-existing view.
 217                  */
 218                 relation_close(rel, NoLock);    /* keep the lock! */
 219
 220                 return viewOid;
 221         }
 222         else
 223         {
 224                 /*
 225                  * now set the parameters for keys/inheritance etc. All of these are
 226                  * uninteresting for views...
 227                  */
 228                 createStmt->relation = (RangeVar *) relation;
 229                 createStmt->tableElts = attrList;
 230                 createStmt->inhRelations = NIL;
 231                 createStmt->constraints = NIL;
 232                 createStmt->options = list_make1(reloptWithOids(false));
 233                 createStmt->oncommit = ONCOMMIT_NOOP;
 234                 createStmt->tablespacename = NULL;
 235
 236                 /*
 237                  * finally create the relation (this will error out if there's an
 238                  * existing view, so we don't need more code to complain if "replace"
 239                  * is false).
 240                  */
 241                 return DefineRelation(createStmt, RELKIND_VIEW);
 242         }
 243 }
 244
 245 /*
 246  * Verify that tupledesc associated with proposed new view definition
 247  * matches tupledesc of old view.  This is basically a cut-down version
 248  * of equalTupleDescs(), with code added to generate specific complaints.
 249  * Also, we allow the new tupledesc to have more columns than the old.
 250  */
 251 static void
 252 checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc)
 253 {
 254         int                     i;
 255
 256         if (newdesc->natts < olddesc->natts)
 257                 ereport(ERROR,
 258                                 (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 259                                  errmsg("cannot drop columns from view")));
 260         /* we can ignore tdhasoid */
 261
 262         for (i = 0; i < olddesc->natts; i++)
 263         {
 264                 Form_pg_attribute newattr = newdesc->attrs[i];
 265                 Form_pg_attribute oldattr = olddesc->attrs[i];
 266
 267                 /* XXX msg not right, but we don't support DROP COL on view anyway */
 268                 if (newattr->attisdropped != oldattr->attisdropped)
 269                         ereport(ERROR,
 270                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 271                                          errmsg("cannot drop columns from view")));
 272
 273                 if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0)
 274                         ereport(ERROR,
 275                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 276                                          errmsg("cannot change name of view column \"%s\" to \"%s\"",
 277                                                         NameStr(oldattr->attname),
 278                                                         NameStr(newattr->attname))));
 279                 /* XXX would it be safe to allow atttypmod to change?  Not sure */
 280                 if (newattr->atttypid != oldattr->atttypid ||
 281                         newattr->atttypmod != oldattr->atttypmod)
 282                         ereport(ERROR,
 283                                         (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 284                                          errmsg("cannot change data type of view column \"%s\" from %s to %s",
 285                                                         NameStr(oldattr->attname),
 286                                                         format_type_with_typemod(oldattr->atttypid,
 287                                                                                                          oldattr->atttypmod),
 288                                                         format_type_with_typemod(newattr->atttypid,
 289                                                                                                          newattr->atttypmod))));
 290                 /* We can ignore the remaining attributes of an attribute... */
 291         }
 292
 293         /*
 294          * We ignore the constraint fields.  The new view desc can't have any
 295          * constraints, and the only ones that could be on the old view are
 296          * defaults, which we are happy to leave in place.
 297          */
 298 }
 299
 300 static void
 301 DefineViewRules(Oid viewOid, Query *viewParse, bool replace)
 302 {
 303         /*
 304          * Set up the ON SELECT rule.  Since the query has already been through
 305          * parse analysis, we use DefineQueryRewrite() directly.
 306          */
 307         DefineQueryRewrite(pstrdup(ViewSelectRuleName),
 308                                            viewOid,
 309                                            NULL,
 310                                            CMD_SELECT,
 311                                            true,
 312                                            replace,
 313                                            list_make1(viewParse));
 314
 315         /*
 316          * Someday: automatic ON INSERT, etc
 317          */
 318 }
 319
 320 /*---------------------------------------------------------------
 321  * UpdateRangeTableOfViewParse
 322  *
 323  * Update the range table of the given parsetree.
 324  * This update consists of adding two new entries IN THE BEGINNING
 325  * of the range table (otherwise the rule system will die a slow,
 326  * horrible and painful death, and we do not want that now, do we?)
 327  * one for the OLD relation and one for the NEW one (both of
 328  * them refer in fact to the "view" relation).
 329  *
 330  * Of course we must also increase the 'varnos' of all the Var nodes
 331  * by 2...
 332  *
 333  * These extra RT entries are not actually used in the query,
 334  * except for run-time permission checking.
 335  *---------------------------------------------------------------
 336  */
 337 static Query *
 338 UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse)
 339 {
 340         Relation        viewRel;
 341         List       *new_rt;
 342         RangeTblEntry *rt_entry1,
 343                            *rt_entry2;
 344
 345         /*
 346          * Make a copy of the given parsetree.  It's not so much that we don't
 347          * want to scribble on our input, it's that the parser has a bad habit of
 348          * outputting multiple links to the same subtree for constructs like
 349          * BETWEEN, and we mustn't have OffsetVarNodes increment the varno of a
 350          * Var node twice.      copyObject will expand any multiply-referenced subtree
 351          * into multiple copies.
 352          */
 353         viewParse = (Query *) copyObject(viewParse);
 354
 355         /* need to open the rel for addRangeTableEntryForRelation */
 356         viewRel = relation_open(viewOid, AccessShareLock);
 357
 358         /*
 359          * Create the 2 new range table entries and form the new range table...
 360          * OLD first, then NEW....
 361          */
 362         rt_entry1 = addRangeTableEntryForRelation(NULL, viewRel,
 363                                                                                           makeAlias("*OLD*", NIL),
 364                                                                                           false, false);
 365         rt_entry2 = addRangeTableEntryForRelation(NULL, viewRel,
 366                                                                                           makeAlias("*NEW*", NIL),
 367                                                                                           false, false);
 368         /* Must override addRangeTableEntry's default access-check flags */
 369         rt_entry1->requiredPerms = 0;
 370         rt_entry2->requiredPerms = 0;
 371
 372         new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable));
 373
 374         viewParse->rtable = new_rt;
 375
 376         /*
 377          * Now offset all var nodes by 2, and jointree RT indexes too.
 378          */
 379         OffsetVarNodes((Node *) viewParse, 2, 0);
 380
 381         relation_close(viewRel, AccessShareLock);
 382
 383         return viewParse;
 384 }
 385
 386 /*
 387  * DefineView
 388  *              Execute a CREATE VIEW command.
 389  */
 390 void
 391 DefineView(ViewStmt *stmt, const char *queryString)
 392 {
 393         Query      *viewParse;
 394         Oid                     viewOid;
 395         RangeVar   *view;
 396
 397         /*
 398          * Run parse analysis to convert the raw parse tree to a Query.  Note this
 399          * also acquires sufficient locks on the source table(s).
 400          *
 401          * Since parse analysis scribbles on its input, copy the raw parse tree;
 402          * this ensures we don't corrupt a prepared statement, for example.
 403          */
 404         viewParse = parse_analyze((Node *) copyObject(stmt->query),
 405                                                           queryString, NULL, 0);
 406
 407         /*
 408          * The grammar should ensure that the result is a single SELECT Query.
 409          */
 410         if (!IsA(viewParse, Query) ||
 411                 viewParse->commandType != CMD_SELECT)
 412                 elog(ERROR, "unexpected parse analysis result");
 413
 414         /*
 415          * If a list of column names was given, run through and insert these into
 416          * the actual query tree. - thomas 2000-03-08
 417          */
 418         if (stmt->aliases != NIL)
 419         {
 420                 ListCell   *alist_item = list_head(stmt->aliases);
 421                 ListCell   *targetList;
 422
 423                 foreach(targetList, viewParse->targetList)
 424                 {
 425                         TargetEntry *te = (TargetEntry *) lfirst(targetList);
 426
 427                         Assert(IsA(te, TargetEntry));
 428                         /* junk columns don't get aliases */
 429                         if (te->resjunk)
 430                                 continue;
 431                         te->resname = pstrdup(strVal(lfirst(alist_item)));
 432                         alist_item = lnext(alist_item);
 433                         if (alist_item == NULL)
 434                                 break;                  /* done assigning aliases */
 435                 }
 436
 437                 if (alist_item != NULL)
 438                         ereport(ERROR,
 439                                         (errcode(ERRCODE_SYNTAX_ERROR),
 440                                          errmsg("CREATE VIEW specifies more column "
 441                                                         "names than columns")));
 442         }
 443
 444         /*
 445          * If the user didn't explicitly ask for a temporary view, check whether
 446          * we need one implicitly.      We allow TEMP to be inserted automatically as
 447          * long as the CREATE command is consistent with that --- no explicit
 448          * schema name.
 449          */
 450         view = stmt->view;
 451         if (!view->istemp && isViewOnTempTable(viewParse))
 452         {
 453                 view = copyObject(view);        /* don't corrupt original command */
 454                 view->istemp = true;
 455                 ereport(NOTICE,
 456                                 (errmsg("view \"%s\" will be a temporary view",
 457                                                 view->relname)));
 458         }
 459
 460         /*
 461          * Create the view relation
 462          *
 463          * NOTE: if it already exists and replace is false, the xact will be
 464          * aborted.
 465          */
 466         viewOid = DefineVirtualRelation(view, viewParse->targetList,
 467                                                                         stmt->replace);
 468
 469         /*
 470          * The relation we have just created is not visible to any other commands
 471          * running with the same transaction & command id. So, increment the
 472          * command id counter (but do NOT pfree any memory!!!!)
 473          */
 474         CommandCounterIncrement();
 475
 476         /*
 477          * The range table of 'viewParse' does not contain entries for the "OLD"
 478          * and "NEW" relations. So... add them!
 479          */
 480         viewParse = UpdateRangeTableOfViewParse(viewOid, viewParse);
 481
 482         /*
 483          * Now create the rules associated with the view.
 484          */
 485         DefineViewRules(viewOid, viewParse, stmt->replace);
 486 }