Backport of revno: 2617.71.1

Bug#42546 Backup: RESTORE fails, thinking it finds an existing table

The problem occured when a MDL locking conflict happened for a non-existent 
table between a CREATE and a INSERT statement. The code for CREATE 
interpreted this lock conflict to mean that the table existed, 
which meant that the statement failed when it should not have.
The problem could occur for CREATE TABLE, CREATE TABLE LIKE and
ALTER TABLE RENAME.

This patch fixes the problem for CREATE TABLE and CREATE TABLE LIKE.
It is based on code backported from the mysql-6.1-fk tree written
by Dmitry Lenev. CREATE now uses normal open_and_lock_tables() code 
to acquire exclusive locks. This means that for the test case in the bug 
description, CREATE will wait until INSERT completes so that it can 
get the exclusive lock. This resolves the reported bug.

The patch also prohibits CREATE TABLE and CREATE TABLE LIKE under 
LOCK TABLES. Note that this is an incompatible change and must 
be reflected in the documentation. Affected test cases have been
updated.

mdl_sync.test contains tests for CREATE TABLE and CREATE TABLE LIKE.

Fixing the issue for ALTER TABLE RENAME is beyond the scope of this
patch. ALTER TABLE cannot be prohibited from working under LOCK TABLES
as this could seriously impact customers and a proper fix would require
a significant rewrite.

1 files changed, 10 insertions, 7 deletions

diff --git a/mysql-test/r/ps_ddl.result b/mysql-test/r/ps_ddl.result
index f411328ed7c..3d57c8f7332 100644
--- a/mysql-test/r/ps_ddl.result
+++ b/mysql-test/r/ps_ddl.result
@@ -1755,21 +1755,21 @@ SUCCESS
 
 drop table t1;
 deallocate prepare stmt;
-# XXX: no validation of the first table in case of
-# CREATE TEMPORARY TABLE. This is a shortcoming of the current code,
-# but since validation is not strictly necessary, nothing is done
-# about it.
-# Will be fixed as part of work on Bug#21431 "Incomplete support of
-# temporary tables"
 create table t1 (a int);
 insert into t1 (a) values (1);
 prepare stmt from "create temporary table if not exists t2 as select * from t1";
 execute stmt;
 drop table t2;
 execute stmt;
+call p_verify_reprepare_count(0);
+SUCCESS
+
 execute stmt;
 Warnings:
 Note	1050	Table 't2' already exists
+call p_verify_reprepare_count(1);
+SUCCESS
+
 select * from t2;
 a
 1
@@ -1777,6 +1777,9 @@ a
 execute stmt;
 Warnings:
 Note	1050	Table 't2' already exists
+call p_verify_reprepare_count(0);
+SUCCESS
+
 select * from t2;
 a
 1
@@ -1790,7 +1793,7 @@ Note	1050	Table 't2' already exists
 select * from t2;
 a
 1
-call p_verify_reprepare_count(0);
+call p_verify_reprepare_count(1);
 SUCCESS
 
 drop table t1;