Backport of revno: 3702

Bug #48248 assert in MDL_ticket::upgrade_shared_lock_to_exclusive

The assert would happen if REPAIR TABLE was used on a table already
locked by LOCK TABLES READ. REPAIR mistakenly tried to upgrade the
read-lock to exclusive, thereby triggering the assert.

The cause of the problem was that REPAIR TABLE ignored errors 
from opening and locking tables. This is by design, as REPAIR
can be used to broken tables that cannot be opened. However,
repair also ignored logical errors such as the inability to
exclusivly lock a table due to conflicting LOCK TABLES.

This patch fixes the problem by not ignoring errors from
opening and locking tables if inside LOCK TABLES mode.
In LOCK TABLES we already know that the table can be opened,
so that the failure to open must be a logical error.

Test added to repair.test.

1 files changed, 12 insertions, 0 deletions

diff --git a/mysql-test/r/repair.result b/mysql-test/r/repair.result
index 5bb3dd76fed..77eb927a21f 100644
--- a/mysql-test/r/repair.result
+++ b/mysql-test/r/repair.result
@@ -157,3 +157,15 @@ REPAIR TABLE tt1 USE_FRM;
 Table	Op	Msg_type	Msg_text
 tt1	repair	error	Cannot repair temporary table from .frm file
 DROP TABLE tt1;
+#
+# Bug #48248 assert in MDL_ticket::upgrade_shared_lock_to_exclusive
+#
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1(a INT);
+LOCK TABLES t1 READ;
+REPAIR TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	Error	Table 't1' was locked with a READ lock and can't be updated
+test.t1	repair	status	Operation failed
+UNLOCK TABLES;
+DROP TABLE t1;