New Features In MySQL 6.x

You’ve probably seen the MySQL Reference Manual page “What’s New in MySQL 6.0″ and so you’ve seen this description of a new feature: “Support for extended comments for tables, columns, and indexes.” Here’s what “extended” means.

You can do a little more with COMMENTs in ALTER or CREATE statements. The easy way to see the difference is by running this statement in both MySQL 5.1 and MySQL 6.0:

SELECT table_schema, table_name, column_name, character_maximum_length

FROM information_schema.columns

WHERE column_name LIKE '%comment';

From that, you’ll see that the differences are:

TABLE_NAME     COLUMN_NAME      CHARACTER_MAXIMUM_LENGTH CHARACTER_MAXIMUM_LENGTH

                                in MySQL 5.1             in MySQL 6.0

COLUMNS        COLUMN_COMMENT   255                      1024

PARTITIONS     PARTITION_COMMENT 80                        80

TABLES         TABLE_COMMENT     80                      2048

STATISTICS     INDEX_COMMENT    n/a                      1024

In other words, the maximum length of a column or table comment is muchly increased, and it’s now possible to have index comments too. Partition comment length is changed too, but you can’t see it yet (Bug#37728). This change was for a special request from one of MySQL’s partners.

This entry was posted on Sunday, June 29th, 2008 at 6:45 pm and is filed under Tiny Tweaks. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.