Bug #15977 mysqldump DISABLE KEYS/LOCK TABLES in wrong order

Submitted:	25 Dec 2005 4:59	Modified:	13 Jul 2006 19:54
Reporter:	Kolbe Kegel	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: mysqldump Command-line Client	Severity:	S3 (Non-critical)
Version:	4.1,5.0	OS:	Linux (Linux)
Assigned to:	Ian Greenhoe	CPU Architecture:	Any

Description:
When mysqldump is executed against a MyISAM table, DISABLE KEYS is written before LOCK TABLES.

It would be possible for a query executed after keys were disabled and before tables were locked to take a very long time, as it would be executing without the benefit of indexes.

How to repeat:
Create a MyISAM table
Run mysqldump against the table

/*!40000 ALTER TABLE `t1` DISABLE KEYS */;
LOCK TABLES `t1` WRITE;
UNLOCK TABLES;
/*!40000 ALTER TABLE `t1` ENABLE KEYS */;

Suggested fix:
LOCK TABLES should be written before DISABLE KEYS in mysqldump output.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/7985

In 4.1.21

Noted in 4.1.21 changelog.

When mysqldump disabled keys and locked a MyISAM table, the lock operation happened second. If another client performed a query on the table in the interim, it could take a long time due to indexes not
being used. Now the lock operation happens first.

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