/*------------------------------------------------------------------------- * * view.c * use rewrite rules to construct views * * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/commands/view.c,v 1.95 2006/07/02 02:23:20 momjian Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/heapam.h" #include "catalog/dependency.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 "optimizer/clauses.h" #include "parser/parse_expr.h" #include "parser/parse_relation.h" #include "rewrite/rewriteDefine.h" #include "rewrite/rewriteManip.h" #include "rewrite/rewriteSupport.h" #include "utils/acl.h" #include "utils/lsyscache.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); bool istemp = rel->rd_istemp; heap_close(rel, AccessShareLock); if (istemp) 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->raw_default = NULL; def->cooked_default = NULL; def->constraints = NIL; def->support = NULL; 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)); /* * Due to the namespace visibility rules for temporary objects, we * should only end up replacing a temporary view with another * temporary view, and vice versa. */ Assert(relation->istemp == rel->rd_istemp); /* * Create a tuple descriptor to compare against the existing view, and * verify it matches. */ descriptor = BuildDescForRelation(attrList); checkViewTupleDesc(descriptor, rel->rd_att); /* * Seems okay, so return the OID of the pre-existing view. */ relation_close(rel, NoLock); /* keep the lock! */ return viewOid; } else { /* * 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; /* * 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). */ return DefineRelation(createStmt, RELKIND_VIEW); } } /* * 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. */ static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc) { int i; if (newdesc->natts != olddesc->natts) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot change number of columns in view"))); /* we can ignore tdhasoid */ for (i = 0; i < newdesc->natts; i++) { Form_pg_attribute newattr = newdesc->attrs[i]; Form_pg_attribute oldattr = olddesc->attrs[i]; /* XXX 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 change number of columns in 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\"", NameStr(oldattr->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\"", NameStr(oldattr->attname)))); /* 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 RuleStmt * FormViewRetrieveRule(const RangeVar *view, Query *viewParse, bool replace) { RuleStmt *rule; /* * Create a RuleStmt that corresponds to the suitable rewrite rule args * for DefineQueryRewrite(); */ rule = makeNode(RuleStmt); rule->relation = copyObject((RangeVar *) view); rule->rulename = pstrdup(ViewSelectRuleName); rule->whereClause = NULL; rule->event = CMD_SELECT; rule->instead = true; rule->actions = list_make1(viewParse); rule->replace = replace; return rule; } static void DefineViewRules(const RangeVar *view, Query *viewParse, bool replace) { RuleStmt *retrieve_rule; #ifdef NOTYET RuleStmt *replace_rule; RuleStmt *append_rule; RuleStmt *delete_rule; #endif retrieve_rule = FormViewRetrieveRule(view, viewParse, replace); #ifdef NOTYET replace_rule = FormViewReplaceRule(view, viewParse); append_rule = FormViewAppendRule(view, viewParse); delete_rule = FormViewDeleteRule(view, viewParse); #endif DefineQueryRewrite(retrieve_rule); #ifdef NOTYET DefineQueryRewrite(replace_rule); DefineQueryRewrite(append_rule); DefineQueryRewrite(delete_rule); #endif } /*--------------------------------------------------------------- * 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 * * - takes a "viewname", "parsetree" pair and then * 1) construct the "virtual" relation * 2) commit the command but NOT the transaction, * so that the relation exists * before the rules are defined. * 2) define the "n" rules specified in the PRS2 paper * over the "virtual" relation *------------------------------------------------------------------- */ void DefineView(RangeVar *view, Query *viewParse, bool replace) { Oid viewOid; /* * If the user didn't explicitly ask for a temporary view, check whether * we need one implicitly. */ if (!view->istemp) { view->istemp = isViewOnTempTable(viewParse); if (view->istemp) ereport(NOTICE, (errmsg("view \"%s\" will be a temporary view", view->relname))); } /* * Create the view relation * * NOTE: if it already exists and replace is false, the xact will be * aborted. */ viewOid = DefineVirtualRelation(view, viewParse->targetList, 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(view, viewParse, replace); } /* * RemoveView * * Remove a view given its name * * We just have to drop the relation; the associated rules will be * cleaned up automatically. */ void RemoveView(const RangeVar *view, DropBehavior behavior) { Oid viewOid; ObjectAddress object; viewOid = RangeVarGetRelid(view, false); object.classId = RelationRelationId; object.objectId = viewOid; object.objectSubId = 0; performDeletion(&object, behavior); }