MySQL Bugs: #39372: "Smart" ALTER TABLE not so smart after all.

Bug #39372	"Smart" ALTER TABLE not so smart after all.
Submitted:	10 Sep 2008 14:25	Modified:	13 Nov 2008 3:39
Reporter:	Tobias Asplund	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: DDL	Severity:	S3 (Non-critical)
Version:	5.1.26	OS:	Any
Assigned to:	Sergei Glukhov	CPU Architecture:	Any

Description:
ALTER TABLE in 5.1 has a regression compared to 5.0 in the cases when you try to use the flags MAX_ROWS or PACK_KEYS together with MyISAM tables.

Example below only shows PACK_KEYS, but similar error occurs with MAX_ROWS and MAX_DATA_LENGTH.

How to repeat:
# Clean Copy of the world database from the docs pages

5.0> ALTER TABLE Country ADD INDEX (Name), ADD INDEX (Population), ADD INDEX (IndepYear), ADD INDEX (GNP);

5.0> pager grep Index_le
PAGER set to 'grep Index_le'

5.0> SHOW TABLE STATUS LIKE 'Country'\G
   Index_length: 22528

5.0> ALTER TABLE Country PACK_KEYS=1;

5.0> SHOW TABLE STATUS LIKE 'Country'\G
   Index_length: 19456

But, look now at 5.1, it seems to not rebuild the table...

5.1> ALTER TABLE Country ADD INDEX (Name), ADD INDEX (Population), ADD INDEX (IndepYear), ADD INDEX (GNP);

5.1> pager grep Index_le
PAGER set to 'grep Index_le'

5.1> SHOW TABLE STATUS LIKE 'Country'\G
   Index_length: 22528

5.1> ALTER TABLE Country PACK_KEYS=1;

5.1> SHOW TABLE STATUS LIKE 'Country'\G
   Index_length: 22528

Suggested fix:
Have MAX_ROWS and PACK_KEYS rebuild the table once changed.

There is a workaround by adding/dropping a new column, but that's very inefficient since it rebuilds the table twice (Could possibly be a more efficient workaround by doing something else in ALTER TABLE, but......)

Thank you for the bug report. 6.0 bzr not affected.

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/55000

2754 Sergey Glukhov	2008-10-02
      Bug#39372 "Smart" ALTER TABLE not so smart after all.
      The problem was that PACK_KEYS clause in ALTER TABLE did not trigger
      table reconstruction.
      The fix is to rebuild a table if PACK_KEYS is specified.

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/55017

2754 Sergey Glukhov	2008-10-02
      Bug#39372 "Smart" ALTER TABLE not so smart after all.
      The problem was that PACK_KEYS and MAX_ROWS clause in ALTER TABLE did not trigger
      table reconstruction.
      The fix is to rebuild a table if PACK_KEYS or MAX_ROWS are specified.

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/55906

2772 Sergey Glukhov	2008-10-09
      Bug#39372 "Smart" ALTER TABLE not so smart after all.
      The problem was that PACK_KEYS and MAX_ROWS clause in ALTER TABLE did not trigger
      table reconstruction.
      The fix is to rebuild a table if PACK_KEYS or MAX_ROWS are specified.

Pushed into 6.0.8-alpha  (revid:sergey.glukhov@sun.com-20081009104913-91h0wlocv02g1p88) (version source revid:sergey.glukhov@sun.com-20081009105309-cs05hufzyohagnuh) (pib:5)

Pushed into 5.1.30  (revid:sergey.glukhov@sun.com-20081009104913-91h0wlocv02g1p88) (version source revid:kgeorge@mysql.com-20081010130753-obt82wv52av801ed) (pib:5)

The versions are actually 5.1.31, 6.0.9.

Noted in 5.1.31, 6.0.9 changelogs.

Use of the PACK_KEYS or MAX_ROWS table option in ALTER TABLE should
have triggered table reconstruction but did not.

Pushed into 5.1.31-ndb-6.2.17 (revid:tomas.ulin@sun.com-20090119095303-uwwvxiibtr38djii) (version source revid:tomas.ulin@sun.com-20090108105244-8opp3i85jw0uj5ib) (merge vers: 5.1.31-ndb-6.2.17) (pib:6)

Pushed into 5.1.31-ndb-6.3.21 (revid:tomas.ulin@sun.com-20090119104956-guxz190n2kh31fxl) (version source revid:tomas.ulin@sun.com-20090119104956-guxz190n2kh31fxl) (merge vers: 5.1.31-ndb-6.3.21) (pib:6)

Pushed into 5.1.31-ndb-6.4.1 (revid:tomas.ulin@sun.com-20090119144033-4aylstx5czzz88i5) (version source revid:tomas.ulin@sun.com-20090119144033-4aylstx5czzz88i5) (merge vers: 5.1.31-ndb-6.4.1) (pib:6)