diff --git a/doc/src/sgml/rules.sgml b/doc/src/sgml/rules.sgml index be3d17c8525..3c9459b6482 100644 --- a/doc/src/sgml/rules.sgml +++ b/doc/src/sgml/rules.sgml @@ -280,14 +280,16 @@ Views in PostgreSQL are implemented - using the rule system. In fact, there is essentially no difference - between: + using the rule system. A view is basically an empty table (having no + actual storage) with an ON SELECT DO INSTEAD rule. + Conventionally, that rule is named _RETURN. + So a view like CREATE VIEW myview AS SELECT * FROM mytab; - compared against the two commands: + is very nearly the same thing as CREATE TABLE myview (same column list as mytab); @@ -295,13 +297,17 @@ CREATE RULE "_RETURN" AS ON SELECT TO myview DO INSTEAD SELECT * FROM mytab; - because this is exactly what the CREATE VIEW - command does internally. This has some side effects. One of them - is that the information about a view in the - PostgreSQL system catalogs is exactly - the same as it is for a table. So for the parser, there is - absolutely no difference between a table and a view. They are the - same thing: relations. + although you can't actually write that, because tables are not + allowed to have ON SELECT rules. + + + + A view can also have other kinds of DO INSTEAD + rules, allowing INSERT, UPDATE, + or DELETE commands to be performed on the view + despite its lack of underlying storage. + This is discussed further below, in + . @@ -1111,7 +1117,7 @@ SELECT word FROM words ORDER BY word <-> 'caterpiler' LIMIT 10; Rules that are defined on INSERT, UPDATE, and DELETE are significantly different from the view rules - described in the previous section. First, their CREATE + described in the previous sections. First, their CREATE RULE command allows more: diff --git a/src/backend/rewrite/rewriteDefine.c b/src/backend/rewrite/rewriteDefine.c index db45d8a08b2..8ac2c81b06b 100644 --- a/src/backend/rewrite/rewriteDefine.c +++ b/src/backend/rewrite/rewriteDefine.c @@ -239,7 +239,6 @@ DefineQueryRewrite(const char *rulename, Relation event_relation; ListCell *l; Query *query; - bool RelisBecomingView = false; Oid ruleId = InvalidOid; ObjectAddress address; @@ -311,7 +310,18 @@ DefineQueryRewrite(const char *rulename, /* * Rules ON SELECT are restricted to view definitions * - * So there cannot be INSTEAD NOTHING, ... + * So this had better be a view, ... + */ + if (event_relation->rd_rel->relkind != RELKIND_VIEW && + event_relation->rd_rel->relkind != RELKIND_MATVIEW) + ereport(ERROR, + (errcode(ERRCODE_WRONG_OBJECT_TYPE), + errmsg("relation \"%s\" cannot have ON SELECT rules", + RelationGetRelationName(event_relation)), + errdetail_relkind_not_supported(event_relation->rd_rel->relkind))); + + /* + * ... there cannot be INSTEAD NOTHING, ... */ if (action == NIL) ereport(ERROR, @@ -407,93 +417,6 @@ DefineQueryRewrite(const char *rulename, ViewSelectRuleName))); rulename = pstrdup(ViewSelectRuleName); } - - /* - * Are we converting a relation to a view? - * - * If so, check that the relation is empty because the storage for the - * relation is going to be deleted. Also insist that the rel not be - * involved in partitioning, nor have any triggers, indexes, child or - * parent tables, RLS policies, or RLS enabled. (Note: some of these - * tests are too strict, because they will reject relations that once - * had such but don't anymore. But we don't really care, because this - * whole business of converting relations to views is just an obsolete - * kluge to allow dump/reload of views that participate in circular - * dependencies.) - */ - if (event_relation->rd_rel->relkind != RELKIND_VIEW && - event_relation->rd_rel->relkind != RELKIND_MATVIEW) - { - TableScanDesc scanDesc; - Snapshot snapshot; - TupleTableSlot *slot; - - if (event_relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE) - ereport(ERROR, - (errcode(ERRCODE_WRONG_OBJECT_TYPE), - errmsg("cannot convert partitioned table \"%s\" to a view", - RelationGetRelationName(event_relation)))); - - /* only case left: */ - Assert(event_relation->rd_rel->relkind == RELKIND_RELATION); - - if (event_relation->rd_rel->relispartition) - ereport(ERROR, - (errcode(ERRCODE_WRONG_OBJECT_TYPE), - errmsg("cannot convert partition \"%s\" to a view", - RelationGetRelationName(event_relation)))); - - snapshot = RegisterSnapshot(GetLatestSnapshot()); - scanDesc = table_beginscan(event_relation, snapshot, 0, NULL); - slot = table_slot_create(event_relation, NULL); - if (table_scan_getnextslot(scanDesc, ForwardScanDirection, slot)) - ereport(ERROR, - (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), - errmsg("could not convert table \"%s\" to a view because it is not empty", - RelationGetRelationName(event_relation)))); - ExecDropSingleTupleTableSlot(slot); - table_endscan(scanDesc); - UnregisterSnapshot(snapshot); - - if (event_relation->rd_rel->relhastriggers) - ereport(ERROR, - (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), - errmsg("could not convert table \"%s\" to a view because it has triggers", - RelationGetRelationName(event_relation)), - errhint("In particular, the table cannot be involved in any foreign key relationships."))); - - if (event_relation->rd_rel->relhasindex) - ereport(ERROR, - (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), - errmsg("could not convert table \"%s\" to a view because it has indexes", - RelationGetRelationName(event_relation)))); - - if (event_relation->rd_rel->relhassubclass) - ereport(ERROR, - (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), - errmsg("could not convert table \"%s\" to a view because it has child tables", - RelationGetRelationName(event_relation)))); - - if (has_superclass(RelationGetRelid(event_relation))) - ereport(ERROR, - (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), - errmsg("could not convert table \"%s\" to a view because it has parent tables", - RelationGetRelationName(event_relation)))); - - if (event_relation->rd_rel->relrowsecurity) - ereport(ERROR, - (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), - errmsg("could not convert table \"%s\" to a view because it has row security enabled", - RelationGetRelationName(event_relation)))); - - if (relation_has_policies(event_relation)) - ereport(ERROR, - (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), - errmsg("could not convert table \"%s\" to a view because it has row security policies", - RelationGetRelationName(event_relation)))); - - RelisBecomingView = true; - } } else { @@ -569,94 +492,6 @@ DefineQueryRewrite(const char *rulename, SetRelationRuleStatus(event_relid, true); } - /* --------------------------------------------------------------------- - * If the relation is becoming a view: - * - delete the associated storage files - * - get rid of any system attributes in pg_attribute; a view shouldn't - * have any of those - * - remove the toast table; there is no need for it anymore, and its - * presence would make vacuum slightly more complicated - * - set relkind to RELKIND_VIEW, and adjust other pg_class fields - * to be appropriate for a view - * - * NB: we had better have AccessExclusiveLock to do this ... - * --------------------------------------------------------------------- - */ - if (RelisBecomingView) - { - Relation relationRelation; - Oid toastrelid; - HeapTuple classTup; - Form_pg_class classForm; - - relationRelation = table_open(RelationRelationId, RowExclusiveLock); - toastrelid = event_relation->rd_rel->reltoastrelid; - - /* drop storage while table still looks like a table */ - RelationDropStorage(event_relation); - DeleteSystemAttributeTuples(event_relid); - - /* - * Drop the toast table if any. (This won't take care of updating the - * toast fields in the relation's own pg_class entry; we handle that - * below.) - */ - if (OidIsValid(toastrelid)) - { - ObjectAddress toastobject; - - /* - * Delete the dependency of the toast relation on the main - * relation so we can drop the former without dropping the latter. - */ - deleteDependencyRecordsFor(RelationRelationId, toastrelid, - false); - - /* Make deletion of dependency record visible */ - CommandCounterIncrement(); - - /* Now drop toast table, including its index */ - toastobject.classId = RelationRelationId; - toastobject.objectId = toastrelid; - toastobject.objectSubId = 0; - performDeletion(&toastobject, DROP_RESTRICT, - PERFORM_DELETION_INTERNAL); - } - - /* - * SetRelationRuleStatus may have updated the pg_class row, so we must - * advance the command counter before trying to update it again. - */ - CommandCounterIncrement(); - - /* - * Fix pg_class entry to look like a normal view's, including setting - * the correct relkind and removal of reltoastrelid of the toast table - * we potentially removed above. - */ - classTup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(event_relid)); - if (!HeapTupleIsValid(classTup)) - elog(ERROR, "cache lookup failed for relation %u", event_relid); - classForm = (Form_pg_class) GETSTRUCT(classTup); - - classForm->relam = InvalidOid; - classForm->reltablespace = InvalidOid; - classForm->relpages = 0; - classForm->reltuples = -1; - classForm->relallvisible = 0; - classForm->reltoastrelid = InvalidOid; - classForm->relhasindex = false; - classForm->relkind = RELKIND_VIEW; - classForm->relfrozenxid = InvalidTransactionId; - classForm->relminmxid = InvalidMultiXactId; - classForm->relreplident = REPLICA_IDENTITY_NOTHING; - - CatalogTupleUpdate(relationRelation, &classTup->t_self, classTup); - - heap_freetuple(classTup); - table_close(relationRelation, RowExclusiveLock); - } - ObjectAddressSet(address, RewriteRelationId, ruleId); /* Close rel, but keep lock till commit... */ diff --git a/src/test/modules/test_ddl_deparse/expected/create_rule.out b/src/test/modules/test_ddl_deparse/expected/create_rule.out index fe3d047a411..78724df818b 100644 --- a/src/test/modules/test_ddl_deparse/expected/create_rule.out +++ b/src/test/modules/test_ddl_deparse/expected/create_rule.out @@ -1,6 +1,8 @@ --- --- CREATE_RULE --- +--- Note: views' ON SELECT rules are tested elsewhere. +--- CREATE RULE rule_1 AS ON INSERT TO datatype_table @@ -16,12 +18,6 @@ CREATE RULE rule_3 AS TO datatype_table DO ALSO NOTHING; NOTICE: DDL test: type simple, tag CREATE RULE -CREATE RULE "_RETURN" AS - ON SELECT - TO like_datatype_table - DO INSTEAD - SELECT * FROM datatype_view; -NOTICE: DDL test: type simple, tag CREATE RULE CREATE RULE rule_3 AS ON DELETE TO like_datatype_table diff --git a/src/test/modules/test_ddl_deparse/sql/create_rule.sql b/src/test/modules/test_ddl_deparse/sql/create_rule.sql index 60ac151a264..7d03859a172 100644 --- a/src/test/modules/test_ddl_deparse/sql/create_rule.sql +++ b/src/test/modules/test_ddl_deparse/sql/create_rule.sql @@ -1,6 +1,8 @@ --- --- CREATE_RULE --- +--- Note: views' ON SELECT rules are tested elsewhere. +--- CREATE RULE rule_1 AS @@ -18,12 +20,6 @@ CREATE RULE rule_3 AS TO datatype_table DO ALSO NOTHING; -CREATE RULE "_RETURN" AS - ON SELECT - TO like_datatype_table - DO INSTEAD - SELECT * FROM datatype_view; - CREATE RULE rule_3 AS ON DELETE TO like_datatype_table diff --git a/src/test/regress/expected/rowsecurity.out b/src/test/regress/expected/rowsecurity.out index ac21a11330a..31509a0a6f8 100644 --- a/src/test/regress/expected/rowsecurity.out +++ b/src/test/regress/expected/rowsecurity.out @@ -3942,28 +3942,6 @@ DROP ROLE regress_rls_frank; -- succeeds ROLLBACK TO q; ROLLBACK; -- cleanup -- --- Converting table to view --- -BEGIN; -CREATE TABLE t (c int); -CREATE POLICY p ON t USING (c % 2 = 1); -ALTER TABLE t ENABLE ROW LEVEL SECURITY; -SAVEPOINT q; -CREATE RULE "_RETURN" AS ON SELECT TO t DO INSTEAD - SELECT * FROM generate_series(1,5) t0(c); -- fails due to row-level security enabled -ERROR: could not convert table "t" to a view because it has row security enabled -ROLLBACK TO q; -ALTER TABLE t DISABLE ROW LEVEL SECURITY; -SAVEPOINT q; -CREATE RULE "_RETURN" AS ON SELECT TO t DO INSTEAD - SELECT * FROM generate_series(1,5) t0(c); -- fails due to policy p on t -ERROR: could not convert table "t" to a view because it has row security policies -ROLLBACK TO q; -DROP POLICY p ON t; -CREATE RULE "_RETURN" AS ON SELECT TO t DO INSTEAD - SELECT * FROM generate_series(1,5) t0(c); -- succeeds -ROLLBACK; --- -- Policy expression handling -- BEGIN; diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out index 37c1c864739..8d85ffc7608 100644 --- a/src/test/regress/expected/rules.out +++ b/src/test/regress/expected/rules.out @@ -2707,54 +2707,26 @@ ERROR: cannot drop rule _RETURN on view rules_fooview because view rules_foovie HINT: You can drop view rules_fooview instead. drop view rules_fooview; -- --- test conversion of table to view (needed to load some pg_dump files) +-- We used to allow converting a table to a view by creating a "_RETURN" +-- rule for it, but no more. -- create table rules_fooview (x int, y text); -select xmin, * from rules_fooview; - xmin | x | y -------+---+--- -(0 rows) - create rule "_RETURN" as on select to rules_fooview do instead select 1 as x, 'aaa'::text as y; -select * from rules_fooview; - x | y ----+----- - 1 | aaa -(1 row) - -select xmin, * from rules_fooview; -- fail, views don't have such a column -ERROR: column "xmin" does not exist -LINE 1: select xmin, * from rules_fooview; - ^ -select reltoastrelid, relkind, relfrozenxid - from pg_class where oid = 'rules_fooview'::regclass; - reltoastrelid | relkind | relfrozenxid ----------------+---------+-------------- - 0 | v | 0 -(1 row) - -drop view rules_fooview; --- cannot convert an inheritance parent or child to a view, though -create table rules_fooview (x int, y text); -create table rules_fooview_child () inherits (rules_fooview); -create rule "_RETURN" as on select to rules_fooview do instead - select 1 as x, 'aaa'::text as y; -ERROR: could not convert table "rules_fooview" to a view because it has child tables -create rule "_RETURN" as on select to rules_fooview_child do instead - select 1 as x, 'aaa'::text as y; -ERROR: could not convert table "rules_fooview_child" to a view because it has parent tables -drop table rules_fooview cascade; -NOTICE: drop cascades to table rules_fooview_child +ERROR: relation "rules_fooview" cannot have ON SELECT rules +DETAIL: This operation is not supported for tables. +drop table rules_fooview; -- likewise, converting a partitioned table or partition to view is not allowed create table rules_fooview (x int, y text) partition by list (x); create rule "_RETURN" as on select to rules_fooview do instead select 1 as x, 'aaa'::text as y; -ERROR: cannot convert partitioned table "rules_fooview" to a view +ERROR: relation "rules_fooview" cannot have ON SELECT rules +DETAIL: This operation is not supported for partitioned tables. create table rules_fooview_part partition of rules_fooview for values in (1); create rule "_RETURN" as on select to rules_fooview_part do instead select 1 as x, 'aaa'::text as y; -ERROR: cannot convert partition "rules_fooview_part" to a view +ERROR: relation "rules_fooview_part" cannot have ON SELECT rules +DETAIL: This operation is not supported for tables. drop table rules_fooview; -- -- check for planner problems with complex inherited UPDATES diff --git a/src/test/regress/sql/rowsecurity.sql b/src/test/regress/sql/rowsecurity.sql index febf3cc4cf1..b38fa8ed8f0 100644 --- a/src/test/regress/sql/rowsecurity.sql +++ b/src/test/regress/sql/rowsecurity.sql @@ -1713,30 +1713,6 @@ ROLLBACK TO q; ROLLBACK; -- cleanup --- --- Converting table to view --- -BEGIN; -CREATE TABLE t (c int); -CREATE POLICY p ON t USING (c % 2 = 1); -ALTER TABLE t ENABLE ROW LEVEL SECURITY; - -SAVEPOINT q; -CREATE RULE "_RETURN" AS ON SELECT TO t DO INSTEAD - SELECT * FROM generate_series(1,5) t0(c); -- fails due to row-level security enabled -ROLLBACK TO q; - -ALTER TABLE t DISABLE ROW LEVEL SECURITY; -SAVEPOINT q; -CREATE RULE "_RETURN" AS ON SELECT TO t DO INSTEAD - SELECT * FROM generate_series(1,5) t0(c); -- fails due to policy p on t -ROLLBACK TO q; - -DROP POLICY p ON t; -CREATE RULE "_RETURN" AS ON SELECT TO t DO INSTEAD - SELECT * FROM generate_series(1,5) t0(c); -- succeeds -ROLLBACK; - -- -- Policy expression handling -- diff --git a/src/test/regress/sql/rules.sql b/src/test/regress/sql/rules.sql index bfb5f3b0bb0..aee53816654 100644 --- a/src/test/regress/sql/rules.sql +++ b/src/test/regress/sql/rules.sql @@ -884,33 +884,14 @@ drop rule "_RETURN" on rules_fooview; drop view rules_fooview; -- --- test conversion of table to view (needed to load some pg_dump files) +-- We used to allow converting a table to a view by creating a "_RETURN" +-- rule for it, but no more. -- create table rules_fooview (x int, y text); -select xmin, * from rules_fooview; - create rule "_RETURN" as on select to rules_fooview do instead select 1 as x, 'aaa'::text as y; - -select * from rules_fooview; -select xmin, * from rules_fooview; -- fail, views don't have such a column - -select reltoastrelid, relkind, relfrozenxid - from pg_class where oid = 'rules_fooview'::regclass; - -drop view rules_fooview; - --- cannot convert an inheritance parent or child to a view, though -create table rules_fooview (x int, y text); -create table rules_fooview_child () inherits (rules_fooview); - -create rule "_RETURN" as on select to rules_fooview do instead - select 1 as x, 'aaa'::text as y; -create rule "_RETURN" as on select to rules_fooview_child do instead - select 1 as x, 'aaa'::text as y; - -drop table rules_fooview cascade; +drop table rules_fooview; -- likewise, converting a partitioned table or partition to view is not allowed create table rules_fooview (x int, y text) partition by list (x);