/*------------------------------------------------------------------------- * * view.c * use rewrite rules to construct views * * Portions Copyright (c) 1996-2023, 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/relation.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/rewriteHandler.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" #include "utils/syscache.h" static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc); /*--------------------------------------------------------------------- * DefineVirtualRelation * * Create a view relation and use the rules system to store the query * for the view. * * EventTriggerAlterTableStart must have been called already. *--------------------------------------------------------------------- */ static ObjectAddress DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace, List *options, Query *viewParse) { Oid viewOid; LOCKMODE lockmode; 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 = (TargetEntry *) lfirst(t); if (!tle->resjunk) { ColumnDef *def = makeColumnDef(tle->resname, exprType((Node *) tle->expr), exprTypmod((Node *) tle->expr), 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("could not determine which collation to use for view column \"%s\"", def->colname), errhint("Use the COLLATE clause to set the collation explicitly."))); } else Assert(!OidIsValid(def->collOid)); attrList = lappend(attrList, def); } } /* * Look up, check permissions on, and lock the creation namespace; also * check for a preexisting view with the same name. This will also set * relation->relpersistence to RELPERSISTENCE_TEMP if the selected * namespace is temporary. */ lockmode = replace ? AccessExclusiveLock : NoLock; (void) RangeVarGetAndCheckCreationNamespace(relation, lockmode, &viewOid); if (OidIsValid(viewOid) && replace) { Relation rel; TupleDesc descriptor; List *atcmds = NIL; AlterTableCmd *atcmd; ObjectAddress address; /* Relation is already locked, but we must build a relcache entry. */ rel = relation_open(viewOid, NoLock); /* Make sure it *is* a view. */ if (rel->rd_rel->relkind != RELKIND_VIEW) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is not a view", 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. * * Note that we must do this before updating the query for the view, * since the rules system requires that the correct view columns be in * place when defining the new rules. * * Also note that ALTER TABLE doesn't run parse transformation on * AT_AddColumnToView commands. The ColumnDef we supply must be ready * to execute as-is. */ if (list_length(attrList) > rel->rd_att->natts) { ListCell *c; int skip = rel->rd_att->natts; foreach(c, attrList) { if (skip > 0) { skip--; continue; } atcmd = makeNode(AlterTableCmd); atcmd->subtype = AT_AddColumnToView; atcmd->def = (Node *) lfirst(c); atcmds = lappend(atcmds, atcmd); } /* EventTriggerAlterTableStart called by ProcessUtilitySlow */ AlterTableInternal(viewOid, atcmds, true); /* Make the new view columns visible */ CommandCounterIncrement(); } /* * Update the query for the view. * * Note that we must do this before updating the view options, because * the new options may not be compatible with the old view query (for * example if we attempt to add the WITH CHECK OPTION, we require that * the new view be automatically updatable, but the old view may not * have been). */ StoreViewQuery(viewOid, viewParse, replace); /* Make the new view query visible */ CommandCounterIncrement(); /* * Update the view's options. * * The new options list replaces the existing options list, even if * it's empty. */ atcmd = makeNode(AlterTableCmd); atcmd->subtype = AT_ReplaceRelOptions; atcmd->def = (Node *) options; atcmds = list_make1(atcmd); /* EventTriggerAlterTableStart called by ProcessUtilitySlow */ AlterTableInternal(viewOid, atcmds, true); /* * There is very little to do here to update the view's dependencies. * Most view-level dependency relationships, such as those on the * owner, schema, and associated composite type, aren't changing. * Because we don't allow changing type or collation of an existing * view column, those dependencies of the existing columns don't * change either, while the AT_AddColumnToView machinery took care of * adding such dependencies for new view columns. The dependencies of * the view's query could have changed arbitrarily, but that was dealt * with inside StoreViewQuery. What remains is only to check that * view replacement is allowed when we're creating an extension. */ ObjectAddressSet(address, RelationRelationId, viewOid); recordDependencyOnCurrentExtension(&address, true); /* * Seems okay, so return the OID of the pre-existing view. */ relation_close(rel, NoLock); /* keep the lock! */ return address; } else { ObjectAddress address; /* * Set the parameters for keys/inheritance etc. All of these are * uninteresting for views... */ createStmt->relation = relation; createStmt->tableElts = attrList; createStmt->inhRelations = NIL; createStmt->constraints = NIL; createStmt->options = options; createStmt->oncommit = ONCOMMIT_NOOP; createStmt->tablespacename = NULL; createStmt->if_not_exists = false; /* * 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). */ address = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid, NULL, NULL); Assert(address.objectId != InvalidOid); /* Make the new view relation visible */ CommandCounterIncrement(); /* Store the query for the view */ StoreViewQuery(address.objectId, viewParse, replace); return address; } } /* * 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"))); for (i = 0; i < olddesc->natts; i++) { Form_pg_attribute newattr = TupleDescAttr(newdesc, i); Form_pg_attribute oldattr = TupleDescAttr(olddesc, 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)), errhint("Use ALTER VIEW ... RENAME COLUMN ... to change name of view column instead."))); /* * We cannot allow type, typmod, or collation to change, since these * properties may be embedded in Vars of other views/rules referencing * this one. Other column attributes can be ignored. */ 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)))); /* * At this point, attcollations should be both valid or both invalid, * so applying get_collation_name unconditionally should be fine. */ if (newattr->attcollation != oldattr->attcollation) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot change collation of view column \"%s\" from \"%s\" to \"%s\"", NameStr(oldattr->attname), get_collation_name(oldattr->attcollation), get_collation_name(newattr->attcollation)))); } /* * 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 */ } /* * DefineView * Execute a CREATE VIEW command. */ ObjectAddress DefineView(ViewStmt *stmt, const char *queryString, int stmt_location, int stmt_len) { RawStmt *rawstmt; Query *viewParse; RangeVar *view; ListCell *cell; bool check_option; ObjectAddress address; /* * Run parse analysis to convert the raw parse tree to a Query. Note this * also acquires sufficient locks on the source table(s). */ rawstmt = makeNode(RawStmt); rawstmt->stmt = stmt->query; rawstmt->stmt_location = stmt_location; rawstmt->stmt_len = stmt_len; viewParse = parse_analyze_fixedparams(rawstmt, queryString, NULL, 0, NULL); /* * The grammar should ensure that the result is a single SELECT Query. * However, it doesn't forbid SELECT INTO, so we have to check for that. */ if (!IsA(viewParse, Query)) elog(ERROR, "unexpected parse analysis result"); if (viewParse->utilityStmt != NULL && IsA(viewParse->utilityStmt, CreateTableAsStmt)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("views must not contain SELECT INTO"))); if (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->hasModifyingCTE) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("views must not contain data-modifying statements in WITH"))); /* * If the user specified the WITH CHECK OPTION, add it to the list of * reloptions. */ if (stmt->withCheckOption == LOCAL_CHECK_OPTION) stmt->options = lappend(stmt->options, makeDefElem("check_option", (Node *) makeString("local"), -1)); else if (stmt->withCheckOption == CASCADED_CHECK_OPTION) stmt->options = lappend(stmt->options, makeDefElem("check_option", (Node *) makeString("cascaded"), -1)); /* * Check that the view is auto-updatable if WITH CHECK OPTION was * specified. */ check_option = false; foreach(cell, stmt->options) { DefElem *defel = (DefElem *) lfirst(cell); if (strcmp(defel->defname, "check_option") == 0) check_option = true; } /* * If the check option is specified, look to see if the view is actually * auto-updatable or not. */ if (check_option) { const char *view_updatable_error = view_query_is_auto_updatable(viewParse, true); if (view_updatable_error) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("WITH CHECK OPTION is supported only on automatically updatable views"), errhint("%s", _(view_updatable_error)))); } /* * 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 = lfirst_node(TargetEntry, targetList); /* junk columns don't get aliases */ if (te->resjunk) continue; te->resname = pstrdup(strVal(lfirst(alist_item))); alist_item = lnext(stmt->aliases, 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"))); } /* Unlogged views are not sensible. */ if (stmt->view->relpersistence == RELPERSISTENCE_UNLOGGED) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("views cannot be unlogged because they do not have storage"))); /* * 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 = copyObject(stmt->view); /* don't corrupt original command */ if (view->relpersistence == RELPERSISTENCE_PERMANENT && isQueryUsingTempRelation(viewParse)) { view->relpersistence = RELPERSISTENCE_TEMP; 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. */ address = DefineVirtualRelation(view, viewParse->targetList, stmt->replace, stmt->options, viewParse); return address; } /* * Use the rules system to store the query for the view. */ void StoreViewQuery(Oid viewOid, Query *viewParse, bool replace) { /* * Now create the rules associated with the view. */ DefineViewRules(viewOid, viewParse, replace); }