I had a customer recently who needed to reduce their database size on disk quickly without a lot of messy schema redesign and application recoding. They didn’t want to drop any actual data, and their index usage was fairly high, so we decided to look for unused indexes that could be removed. Collecting data It’s [...]
Dropping unused indexes
January 15, 2009 By 6 Comments
Vadim wrote some time ago about how to find unused indexes with single query. I was working on the system today and found hundreds of unused indexes on dozens of tables so just dropping indexes manually did not look fun. So I extended Vadim’s query to generate ALTER TABLE statements automatically. I also made it [...]
Unused indexes by single query
September 12, 2008 By 14 Comments
Usually unused indexes are devil, they waste diskspace, cache, they make INSERT / DELETE / UPDATE operations slower and what makes them worse – it is hard to find them. But now ( with userstatsV2.patch) you can find all unused indexes (since last restart of mysqld) by single query
1 2 3 4 5 6 | SELECT DISTINCT s.TABLE_SCHEMA, s.TABLE_NAME, s.INDEX_NAME FROM information_schema.statistics `s` LEFT JOIN information_schema.index_statistics INDXS ON (s.TABLE_SCHEMA = INDXS.TABLE_SCHEMA AND s.TABLE_NAME=INDXS.TABLE_NAME AND s.INDEX_NAME=INDXS.INDEX_NAME) WHERE INDXS.TABLE_SCHEMA IS NULL; |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | +--------------+---------------------------+-----------------+ | TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | +--------------+---------------------------+-----------------+ | art100 | article100 | ext_key | | art100 | article100 | site_id | | art100 | article100 | hash | | art100 | article100 | forum_id_2 | | art100 | article100 | published | | art100 | article100 | inserted | | art100 | article100 | site_id_2 | | art100 | author100 | PRIMARY | | art100 | author100 | site_id | ... +--------------+---------------------------+-----------------+ 1150 rows in set (1 min 44.23 sec) |
As you see query [...]
