Bug #56494 Segfault in upgrade_shared_lock_to_exclusive() for

           REPAIR of merge table
Bug #56422 CHECK TABLE run when the table is locked reports
           corruption along with timeout

The crash happened if a table maintenance statement (ANALYZE TABLE,
REPAIR TABLE, etc.) was executed on a MERGE table and opening and 
locking a child table failed. This could for example happen if a child
table did not exist or if a lock timeout happened while waiting for
a conflicting metadata lock to disappear.

Since opening and locking the MERGE table and its children failed,
the tables would be closed and the metadata locks released.
However, TABLE_LIST::table for the MERGE table would still be set,
with its value invalid since the tables had been closed.
This caused the table maintenance statement to try to continue
and upgrade the metadata lock on the MERGE table. But since the lock
already had been released, this caused a segfault.

This patch fixes the problem by setting TABLE_LIST::table to NULL 
if open_and_lock_tables() fails. This prevents maintenance
statements from continuing and trying to upgrade the metadata lock.

The patch includes a 5.5 version of the fix for
Bug #46339 crash on REPAIR TABLE merge table USE_FRM.
This bug caused REPAIR TABLE ... USE_FRM to give an assert 
when used on merge tables.

The patch also enables the CHECK TABLE statement for log tables.
Before, CHECK TABLE for log tables gave ER_CANT_LOCK_LOG_TABLE,
yet still counted the statement as successfully executed.
With the changes to table maintenance statement error handling
in this patch, CHECK TABLE would no longer be considered as
successful in this case. This would have caused upgrade scripts
to mistakenly think that the general and slow logs are corrupted
and have to be repaired. Enabling CHECK TABLES for log tables
prevents this from happening.

Finally, the patch changes the error message from "Corrupt" to
"Operation failed" for a number of issues not related to table
corruption. For example "Lock wait timeout exceeded" and 
"Deadlock found trying to get lock".

Test cases added to merge.test and check.test.

1 files changed, 108 insertions, 0 deletions

diff --git a/mysql-test/t/merge.test b/mysql-test/t/merge.test
index 51c4ca51a29..34d0b5bf237 100644
--- a/mysql-test/t/merge.test
+++ b/mysql-test/t/merge.test
@@ -1734,6 +1734,84 @@ t2 WHERE b SOUNDS LIKE e AND d = 1;
 
 DROP TABLE t2, t1;
 
+--echo #
+--echo # Bug#46339 - crash on REPAIR TABLE merge table USE_FRM
+--echo #
+--disable_warnings
+DROP TABLE IF EXISTS m1, t1;
+--enable_warnings
+#
+# Test derived from a proposal of Shane Bester.
+#
+CREATE TABLE t1 (c1 INT) ENGINE=MYISAM;
+CREATE TABLE m1 (c1 INT) ENGINE=MRG_MyISAM UNION=(t1) INSERT_METHOD=LAST;
+#
+# REPAIR ... USE_FRM with LOCK TABLES.
+#
+LOCK TABLE m1 READ;
+REPAIR TABLE m1 USE_FRM;
+UNLOCK TABLES;
+#
+# REPAIR ... USE_FRM without LOCK TABLES.
+#
+# This statement crashed the server (Bug#46339).
+#
+REPAIR TABLE m1 USE_FRM;
+#
+DROP TABLE m1,t1;
+#
+# Test derived from a proposal of Matthias Leich.
+#
+# Base table is missing.
+#
+CREATE TABLE m1 (f1 BIGINT) ENGINE=MRG_MyISAM UNION(t1);
+#
+# This statement crashed the server (Bug#46339).
+#
+REPAIR TABLE m1 USE_FRM;
+#
+# Create base table.
+#
+CREATE TABLE t1 (f1 BIGINT) ENGINE = MyISAM;
+#
+# This statement crashed the server (Bug#46339).
+#
+REPAIR TABLE m1 USE_FRM;
+#
+# Normal repair as reference.
+#
+REPAIR TABLE m1;
+#
+# Cleanup.
+#
+DROP TABLE m1, t1;
+#
+# Same with temporary tables.
+#
+# Base table is missing.
+#
+CREATE TEMPORARY TABLE m1 (f1 BIGINT) ENGINE=MRG_MyISAM UNION(t1);
+#
+# This statement crashed the server (Bug#46339).
+#
+REPAIR TABLE m1 USE_FRM;
+#
+# Create base table.
+#
+CREATE TEMPORARY TABLE t1 (f1 BIGINT) ENGINE=MyISAM;
+#
+# This statement crashed the server (Bug#46339).
+#
+REPAIR TABLE m1 USE_FRM;
+#
+# Normal repair as reference.
+#
+REPAIR TABLE m1;
+#
+# Cleanup.
+#
+DROP TABLE m1, t1;
+
 --echo End of 5.1 tests
 
 --echo #
@@ -2668,6 +2746,36 @@ drop temporary table tmp;
 drop table t1, t2, t3, m1, m2;
 
 
+--echo #
+--echo # Bug#56494 Segfault in upgrade_shared_lock_to_exclusive() for
+--echo #           REPAIR of merge table
+--echo #
+
+--disable_warnings
+DROP TABLE IF EXISTS t1, t2, t_not_exists;
+--enable_warnings
+
+CREATE TABLE t1(a INT);
+ALTER TABLE t1 engine= MERGE UNION (t_not_exists);
+# This caused the segfault
+ANALYZE TABLE t1;
+CHECK TABLE t1;
+CHECKSUM TABLE t1;
+OPTIMIZE TABLE t1;
+REPAIR TABLE t1;
+
+# This caused an assert
+REPAIR TABLE t1 USE_FRM;
+
+DROP TABLE t1;
+CREATE TABLE t1(a INT);
+CREATE TABLE t2(a INT) engine= MERGE UNION (t1);
+# This caused an assert
+REPAIR TABLE t2 USE_FRM;
+
+DROP TABLE t1, t2;
+
+
 --echo End of 6.0 tests
 
 --disable_result_log