Revert "Accept relations of any kind in LOCK TABLE".

Revert 59ab4ac32, as well as the followup fix 33862cb9c, in all
branches.  We need to think a bit harder about what the behavior
of LOCK TABLE on views should be, and there's no time for that
before next week's releases.  We'll take another crack at this
later.

Discussion: https://postgr.es/m/16703-e348f58aab3cf6cc@postgresql.org

doc/src/sgml/ref/lock.sgml

@@ -16,7 +16,7 @@ PostgreSQL documentation
 
  <refnamediv>
   <refname>LOCK</refname>
-  <refpurpose>lock a named relation (table, etc)</refpurpose>
+  <refpurpose>lock a table</refpurpose>
  </refnamediv>
 
  <refsynopsisdiv>
@@ -34,9 +34,7 @@ LOCK [ TABLE ] [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
   <title>Description</title>
 
   <para>
-   <command>LOCK TABLE</command> obtains a table-level lock on a
+   <command>LOCK TABLE</command> obtains a table-level lock, waiting
-   relation (table, partitioned table, foreign table, view,
-   materialized view, index, composite type, sequence), waiting
    if necessary for any conflicting locks to be released.  If
    <literal>NOWAIT</literal> is specified, <command>LOCK
    TABLE</command> does not wait to acquire the desired lock: if it
@@ -112,23 +110,17 @@ LOCK [ TABLE ] [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
-      The name (optionally schema-qualified) of an existing relation to
+      The name (optionally schema-qualified) of an existing table to
-      lock. If <literal>ONLY</literal> is specified before a table name, only that
+      lock. If <literal>ONLY</> is specified before the table name, only that
-      table is locked. If <literal>ONLY</literal> is not specified, the table and all
+      table is locked. If <literal>ONLY</> is not specified, the table and all
-      its descendant tables (if any) are locked.  Optionally, <literal>*</literal>
+      its descendant tables (if any) are locked.  Optionally, <literal>*</>
       can be specified after the table name to explicitly indicate that
       descendant tables are included.
      </para>
 
      <para>
-      Locking a view locks only the view object itself, not any referenced
+      The command <literal>LOCK TABLE a, b;</> is equivalent to
-      relations.  (Note that this behavior is different
+      <literal>LOCK TABLE a; LOCK TABLE b;</>. The tables are locked
-      in <productname>PostgreSQL</productname> v11 and later.)
-     </para>
-
-     <para>
-      The command <literal>LOCK TABLE a, b;</literal> is equivalent to
-      <literal>LOCK TABLE a; LOCK TABLE b;</literal>. The relations are locked
       one-by-one in the order specified in the <command>LOCK
       TABLE</command> command.
      </para>

src/backend/commands/lockcmds.c

@@ -87,6 +87,13 @@ RangeVarCallbackForLockTable(const RangeVar *rv, Oid relid, Oid oldrelid,
 		return;					/* woops, concurrently dropped; no permissions
 								 * check */
 
+	/* Currently, we only allow plain tables to be locked */
+	if (relkind != RELKIND_RELATION)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not a table",
+						rv->relname)));
+
 	/* Check permissions. */
 	aclresult = LockTableAclCheck(relid, lockmode);
 	if (aclresult != ACLCHECK_OK)

src/test/regress/expected/lock.out

@@ -5,10 +5,7 @@
 CREATE SCHEMA lock_schema1;
 SET search_path = lock_schema1;
 CREATE TABLE lock_tbl1 (a BIGINT);
-CREATE VIEW lock_view1 AS SELECT 1 AS a;
+CREATE VIEW lock_view1 AS SELECT 1;
-CREATE MATERIALIZED VIEW lock_mv1 AS SELECT * FROM lock_view1;
-CREATE INDEX lock_mvi1 ON lock_mv1 (a);
-CREATE SEQUENCE lock_seq;
 CREATE ROLE regress_rol_lock1;
 ALTER ROLE regress_rol_lock1 SET search_path = lock_schema1;
 GRANT USAGE ON SCHEMA lock_schema1 TO regress_rol_lock1;
@@ -33,7 +30,8 @@ LOCK TABLE lock_tbl1 IN SHARE MODE NOWAIT;
 LOCK TABLE lock_tbl1 IN SHARE ROW EXCLUSIVE MODE NOWAIT;
 LOCK TABLE lock_tbl1 IN EXCLUSIVE MODE NOWAIT;
 LOCK TABLE lock_tbl1 IN ACCESS EXCLUSIVE MODE NOWAIT;
-LOCK TABLE lock_view1 IN EXCLUSIVE MODE;
+LOCK TABLE lock_view1 IN EXCLUSIVE MODE;   -- Will fail; can't lock a non-table
+ERROR:  "lock_view1" is not a table
 ROLLBACK;
 -- Verify that we can lock a table with inheritance children.
 CREATE TABLE lock_tbl2 (b BIGINT) INHERITS (lock_tbl1);
@@ -53,21 +51,13 @@ BEGIN;
 LOCK TABLE ONLY lock_tbl1;
 ROLLBACK;
 RESET ROLE;
--- Lock other relations
-BEGIN TRANSACTION;
-LOCK TABLE lock_mv1;
-LOCK TABLE lock_mvi1;
-LOCK TABLE lock_seq;
-ROLLBACK;
 --
 -- Clean up
 --
-DROP MATERIALIZED VIEW lock_mv1;
 DROP VIEW lock_view1;
 DROP TABLE lock_tbl3;
 DROP TABLE lock_tbl2;
 DROP TABLE lock_tbl1;
-DROP SEQUENCE lock_seq;
 DROP SCHEMA lock_schema1 CASCADE;
 DROP ROLE regress_rol_lock1;
 -- atomic ops tests

src/test/regress/sql/lock.sql

@@ -6,10 +6,7 @@
 CREATE SCHEMA lock_schema1;
 SET search_path = lock_schema1;
 CREATE TABLE lock_tbl1 (a BIGINT);
-CREATE VIEW lock_view1 AS SELECT 1 AS a;
+CREATE VIEW lock_view1 AS SELECT 1;
-CREATE MATERIALIZED VIEW lock_mv1 AS SELECT * FROM lock_view1;
-CREATE INDEX lock_mvi1 ON lock_mv1 (a);
-CREATE SEQUENCE lock_seq;
 CREATE ROLE regress_rol_lock1;
 ALTER ROLE regress_rol_lock1 SET search_path = lock_schema1;
 GRANT USAGE ON SCHEMA lock_schema1 TO regress_rol_lock1;
@@ -36,7 +33,7 @@ LOCK TABLE lock_tbl1 IN SHARE MODE NOWAIT;
 LOCK TABLE lock_tbl1 IN SHARE ROW EXCLUSIVE MODE NOWAIT;
 LOCK TABLE lock_tbl1 IN EXCLUSIVE MODE NOWAIT;
 LOCK TABLE lock_tbl1 IN ACCESS EXCLUSIVE MODE NOWAIT;
-LOCK TABLE lock_view1 IN EXCLUSIVE MODE;
+LOCK TABLE lock_view1 IN EXCLUSIVE MODE;   -- Will fail; can't lock a non-table
 ROLLBACK;
 
 -- Verify that we can lock a table with inheritance children.
@@ -58,23 +55,13 @@ LOCK TABLE ONLY lock_tbl1;
 ROLLBACK;
 RESET ROLE;
 
--- Lock other relations
-BEGIN TRANSACTION;
-LOCK TABLE lock_mv1;
-LOCK TABLE lock_mvi1;
-LOCK TABLE lock_seq;
-ROLLBACK;
-
-
 --
 -- Clean up
 --
-DROP MATERIALIZED VIEW lock_mv1;
 DROP VIEW lock_view1;
 DROP TABLE lock_tbl3;
 DROP TABLE lock_tbl2;
 DROP TABLE lock_tbl1;
-DROP SEQUENCE lock_seq;
 DROP SCHEMA lock_schema1 CASCADE;
 DROP ROLE regress_rol_lock1;