/*------------------------------------------------------------------------- * * view.c * use rewrite rules to construct views * * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/commands/view.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/heapam.h" #include "access/xact.h" #include "catalog/namespace.h" #include "commands/defrem.h" #include "commands/tablecmds.h" #include "commands/view.h" #include "miscadmin.h" #include "nodes/makefuncs.h" #include "nodes/nodeFuncs.h" #include "parser/analyze.h" #include "parser/parse_relation.h" #include "rewrite/rewriteDefine.h" #include "rewrite/rewriteManip.h" #include "rewrite/rewriteSupport.h" #include "utils/acl.h" #include "utils/builtins.h" #include "utils/lsyscache.h" #include "utils/rel.h" static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc); static bool isViewOnTempTable_walker(Node *node, void *context); /*--------------------------------------------------------------------- * isViewOnTempTable * * Returns true iff any of the relations underlying this view are * temporary tables. *--------------------------------------------------------------------- */ static bool isViewOnTempTable(Query *viewParse) { return isViewOnTempTable_walker((Node *) viewParse, NULL); } static bool isViewOnTempTable_walker(Node *node, void *context) { if (node == NULL) return false; if (IsA(node, Query)) { Query *query = (Query *) node; ListCell *rtable; foreach(rtable, query->rtable) { RangeTblEntry *rte = lfirst(rtable); if (rte->rtekind == RTE_RELATION) { Relation rel = heap_open(rte->relid, AccessShareLock); char relpersistence = rel->rd_rel->relpersistence; heap_close(rel, AccessShareLock); if (relpersistence == RELPERSISTENCE_TEMP) return true; } } return query_tree_walker(query, isViewOnTempTable_walker, context, QTW_IGNORE_JOINALIASES); } return expression_tree_walker(node, isViewOnTempTable_walker, context); } /*--------------------------------------------------------------------- * DefineVirtualRelation * * Create the "view" relation. `DefineRelation' does all the work, * we just provide the correct arguments ... at least when we're * creating a view. If we're updating an existing view, we have to * work harder. *--------------------------------------------------------------------- */ static Oid DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace) { Oid viewOid, namespaceId; CreateStmt *createStmt = makeNode(CreateStmt); List *attrList; ListCell *t; /* * create a list of ColumnDef nodes based on the names and types of the * (non-junk) targetlist items from the view's SELECT list. */ attrList = NIL; foreach(t, tlist) { TargetEntry *tle = lfirst(t); if (!tle->resjunk) { ColumnDef *def = makeNode(ColumnDef); def->colname = pstrdup(tle->resname); def->typeName = makeTypeNameFromOid(exprType((Node *) tle->expr), exprTypmod((Node *) tle->expr)); def->inhcount = 0; def->is_local = true; def->is_not_null = false; def->is_from_type = false; def->storage = 0; def->raw_default = NULL; def->cooked_default = NULL; def->collClause = NULL; def->collOid = exprCollation((Node *) tle->expr); /* * It's possible that the column is of a collatable type but the * collation could not be resolved, so double-check. */ if (type_is_collatable(exprType((Node *) tle->expr))) { if (!OidIsValid(def->collOid)) ereport(ERROR, (errcode(ERRCODE_INDETERMINATE_COLLATION), errmsg("no collation was derived for view column \"%s\"", def->colname), errhint("Use the COLLATE clause to set the collation explicitly."))); } else Assert(!OidIsValid(def->collOid)); def->constraints = NIL; attrList = lappend(attrList, def); } } if (attrList == NIL) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("view must have at least one column"))); /* * Check to see if we want to replace an existing view. */ namespaceId = RangeVarGetCreationNamespace(relation); viewOid = get_relname_relid(relation->relname, namespaceId); if (OidIsValid(viewOid) && replace) { Relation rel; TupleDesc descriptor; /* * Yes. Get exclusive lock on the existing view ... */ rel = relation_open(viewOid, AccessExclusiveLock); /* * Make sure it *is* a view, and do permissions checks. */ if (rel->rd_rel->relkind != RELKIND_VIEW) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is not a view", RelationGetRelationName(rel)))); if (!pg_class_ownercheck(viewOid, GetUserId())) aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS, RelationGetRelationName(rel)); /* Also check it's not in use already */ CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW"); /* * Due to the namespace visibility rules for temporary objects, we * should only end up replacing a temporary view with another * temporary view, and similarly for permanent views. */ Assert(relation->relpersistence == rel->rd_rel->relpersistence); /* * Create a tuple descriptor to compare against the existing view, and * verify that the old column list is an initial prefix of the new * column list. */ descriptor = BuildDescForRelation(attrList); checkViewTupleDesc(descriptor, rel->rd_att); /* * If new attributes have been added, we must add pg_attribute entries * for them. It is convenient (although overkill) to use the ALTER * TABLE ADD COLUMN infrastructure for this. */ if (list_length(attrList) > rel->rd_att->natts) { List *atcmds = NIL; ListCell *c; int skip = rel->rd_att->natts; foreach(c, attrList) { AlterTableCmd *atcmd; if (skip > 0) { skip--; continue; } atcmd = makeNode(AlterTableCmd); atcmd->subtype = AT_AddColumnToView; atcmd->def = (Node *) lfirst(c); atcmds = lappend(atcmds, atcmd); } AlterTableInternal(viewOid, atcmds, true); } /* * Seems okay, so return the OID of the pre-existing view. */ relation_close(rel, NoLock); /* keep the lock! */ return viewOid; } else { Oid relid; /* * now set the parameters for keys/inheritance etc. All of these are * uninteresting for views... */ createStmt->relation = (RangeVar *) relation; createStmt->tableElts = attrList; createStmt->inhRelations = NIL; createStmt->constraints = NIL; createStmt->options = list_make1(defWithOids(false)); createStmt->oncommit = ONCOMMIT_NOOP; createStmt->tablespacename = NULL; createStmt->if_not_exists = false; /* * finally create the relation (this will error out if there's an * existing view, so we don't need more code to complain if "replace" * is false). */ relid = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid); Assert(relid != InvalidOid); return relid; } } /* * Verify that tupledesc associated with proposed new view definition * matches tupledesc of old view. This is basically a cut-down version * of equalTupleDescs(), with code added to generate specific complaints. * Also, we allow the new tupledesc to have more columns than the old. */ static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc) { int i; if (newdesc->natts < olddesc->natts) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot drop columns from view"))); /* we can ignore tdhasoid */ for (i = 0; i < olddesc->natts; i++) { Form_pg_attribute newattr = newdesc->attrs[i]; Form_pg_attribute oldattr = olddesc->attrs[i]; /* XXX msg not right, but we don't support DROP COL on view anyway */ if (newattr->attisdropped != oldattr->attisdropped) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot drop columns from view"))); if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot change name of view column \"%s\" to \"%s\"", NameStr(oldattr->attname), NameStr(newattr->attname)))); /* XXX would it be safe to allow atttypmod to change? Not sure */ if (newattr->atttypid != oldattr->atttypid || newattr->atttypmod != oldattr->atttypmod) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot change data type of view column \"%s\" from %s to %s", NameStr(oldattr->attname), format_type_with_typemod(oldattr->atttypid, oldattr->atttypmod), format_type_with_typemod(newattr->atttypid, newattr->atttypmod)))); /* We can ignore the remaining attributes of an attribute... */ } /* * We ignore the constraint fields. The new view desc can't have any * constraints, and the only ones that could be on the old view are * defaults, which we are happy to leave in place. */ } static void DefineViewRules(Oid viewOid, Query *viewParse, bool replace) { /* * Set up the ON SELECT rule. Since the query has already been through * parse analysis, we use DefineQueryRewrite() directly. */ DefineQueryRewrite(pstrdup(ViewSelectRuleName), viewOid, NULL, CMD_SELECT, true, replace, list_make1(viewParse)); /* * Someday: automatic ON INSERT, etc */ } /*--------------------------------------------------------------- * UpdateRangeTableOfViewParse * * Update the range table of the given parsetree. * This update consists of adding two new entries IN THE BEGINNING * of the range table (otherwise the rule system will die a slow, * horrible and painful death, and we do not want that now, do we?) * one for the OLD relation and one for the NEW one (both of * them refer in fact to the "view" relation). * * Of course we must also increase the 'varnos' of all the Var nodes * by 2... * * These extra RT entries are not actually used in the query, * except for run-time permission checking. *--------------------------------------------------------------- */ static Query * UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse) { Relation viewRel; List *new_rt; RangeTblEntry *rt_entry1, *rt_entry2; /* * Make a copy of the given parsetree. It's not so much that we don't * want to scribble on our input, it's that the parser has a bad habit of * outputting multiple links to the same subtree for constructs like * BETWEEN, and we mustn't have OffsetVarNodes increment the varno of a * Var node twice. copyObject will expand any multiply-referenced subtree * into multiple copies. */ viewParse = (Query *) copyObject(viewParse); /* need to open the rel for addRangeTableEntryForRelation */ viewRel = relation_open(viewOid, AccessShareLock); /* * Create the 2 new range table entries and form the new range table... * OLD first, then NEW.... */ rt_entry1 = addRangeTableEntryForRelation(NULL, viewRel, makeAlias("old", NIL), false, false); rt_entry2 = addRangeTableEntryForRelation(NULL, viewRel, makeAlias("new", NIL), false, false); /* Must override addRangeTableEntry's default access-check flags */ rt_entry1->requiredPerms = 0; rt_entry2->requiredPerms = 0; new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable)); viewParse->rtable = new_rt; /* * Now offset all var nodes by 2, and jointree RT indexes too. */ OffsetVarNodes((Node *) viewParse, 2, 0); relation_close(viewRel, AccessShareLock); return viewParse; } /* * DefineView * Execute a CREATE VIEW command. */ void DefineView(ViewStmt *stmt, const char *queryString) { Query *viewParse; Oid viewOid; RangeVar *view; /* * Run parse analysis to convert the raw parse tree to a Query. Note this * also acquires sufficient locks on the source table(s). * * Since parse analysis scribbles on its input, copy the raw parse tree; * this ensures we don't corrupt a prepared statement, for example. */ viewParse = parse_analyze((Node *) copyObject(stmt->query), queryString, NULL, 0); /* * The grammar should ensure that the result is a single SELECT Query. */ if (!IsA(viewParse, Query) || viewParse->commandType != CMD_SELECT) elog(ERROR, "unexpected parse analysis result"); /* * Check for unsupported cases. These tests are redundant with ones in * DefineQueryRewrite(), but that function will complain about a bogus * ON SELECT rule, and we'd rather the message complain about a view. */ if (viewParse->intoClause != NULL) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("views must not contain SELECT INTO"))); if (viewParse->hasModifyingCTE) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("views must not contain data-modifying statements in WITH"))); /* * If a list of column names was given, run through and insert these into * the actual query tree. - thomas 2000-03-08 */ if (stmt->aliases != NIL) { ListCell *alist_item = list_head(stmt->aliases); ListCell *targetList; foreach(targetList, viewParse->targetList) { TargetEntry *te = (TargetEntry *) lfirst(targetList); Assert(IsA(te, TargetEntry)); /* junk columns don't get aliases */ if (te->resjunk) continue; te->resname = pstrdup(strVal(lfirst(alist_item))); alist_item = lnext(alist_item); if (alist_item == NULL) break; /* done assigning aliases */ } if (alist_item != NULL) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("CREATE VIEW specifies more column " "names than columns"))); } /* * If the user didn't explicitly ask for a temporary view, check whether * we need one implicitly. We allow TEMP to be inserted automatically as * long as the CREATE command is consistent with that --- no explicit * schema name. */ view = stmt->view; if (view->relpersistence == RELPERSISTENCE_PERMANENT && isViewOnTempTable(viewParse)) { view = copyObject(view); /* don't corrupt original command */ view->relpersistence = RELPERSISTENCE_TEMP; ereport(NOTICE, (errmsg("view \"%s\" will be a temporary view", view->relname))); } /* Unlogged views are not sensible. */ if (view->relpersistence == RELPERSISTENCE_UNLOGGED) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("views cannot be unlogged because they do not have storage"))); /* * Create the view relation * * NOTE: if it already exists and replace is false, the xact will be * aborted. */ viewOid = DefineVirtualRelation(view, viewParse->targetList, stmt->replace); /* * The relation we have just created is not visible to any other commands * running with the same transaction & command id. So, increment the * command id counter (but do NOT pfree any memory!!!!) */ CommandCounterIncrement(); /* * The range table of 'viewParse' does not contain entries for the "OLD" * and "NEW" relations. So... add them! */ viewParse = UpdateRangeTableOfViewParse(viewOid, viewParse); /* * Now create the rules associated with the view. */ DefineViewRules(viewOid, viewParse, stmt->replace); }