Manual:revision_comment_temp table

The revision_comment_temp table was a temporary table creating a relation between each row of the revision table and a row of the comment table. It was created (along with the similar revision_actor_temp table) to avoid blocking on an alter of the revision table, which took. On large wikis like the English Wikipedia, altering the revision table is a months-long process. This table was created so that other data migrations could be done while the alter was running. Once adding the rev_comment_id field to the revision table was done, the data from revision_comment_temp was merged back into the revision table and the table was deleted.

This table was introduced in Gerrit change 357892. See also the image_comment_temp table.

Key to revision.rev_id

Key to comment.comment_id

DESCRIBErevision_comment_temp;

+-----------------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------------+---------------------+------+-----+---------+-------+
| revcomment_rev | int(10) unsigned | NO | PRI | NULL | |
| revcomment_comment_id | bigint(20) unsigned | NO | PRI | NULL | |
+-----------------------+---------------------+------+-----+---------+-------+

SHOWINDEXINrevision_comment_temp;

+-----------------------+------------+----------------+--------------+-----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-----------------------+------------+----------------+--------------+-----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| revision_comment_temp | 0 | PRIMARY | 1 | revcomment_rev | A | 0 | NULL | NULL | | BTREE | | |
| revision_comment_temp | 0 | PRIMARY | 2 | revcomment_comment_id | A | 0 | NULL | NULL | | BTREE | | |
| revision_comment_temp | 0 | revcomment_rev | 1 | revcomment_rev | A | 0 | NULL | NULL | | BTREE | | |
+-----------------------+------------+----------------+--------------+-----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

• MediaWiki database tables