https://bugzilla.wikimedia.org/show_bug.cgi?id=53577
Web browser: ---
Bug ID: 53577
Summary: IndexPager::buildQueryInfo (LogPager) query needs
tuning
Product: MediaWiki
Version: 1.21.1
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: Unprioritized
Component: Database
Assignee: [email protected]
Reporter: [email protected]
Classification: Unclassified
Mobile Platform: ---
Have seen multiple instances of this one backing up on commonswiki slaves
recently:
SELECT /* IndexPager::buildQueryInfo (LogPager) 148.160.132.46 */
log_id,log_type,log_action,log_timestamp,log_user,log_user_text,log_namespace,log_title,log_comment,log_params,log_deleted,user_id,user_name,user_editcount,ts_tags
FROM `logging` FORCE INDEX (times) LEFT JOIN `user` ON ((log_user=user_id))
LEFT JOIN `tag_summary` ON ((ts_log_id=log_id)) WHERE (log_action !=
'revision') AND (log_type != 'suppress') AND log_type IN ('delete','move') AND
log_namespace = '0' AND log_title = '0' AND ((log_deleted & 1) = 0) ORDER BY
log_timestamp DESC LIMIT 11
It runs in excess of 10 minutes.
EXPLAIN says the FORCE INDEX sends MySQL onto a very slow index scan over
`times` (log_timestamp) which is hardly better than a table scan in this case.
Removing the FORCE allows `page_time` index be used which reduces execution
time to a few seconds.
Suggest either filtering by a range on log_timestamp or removing the FORCE.
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