https://bugzilla.wikimedia.org/show_bug.cgi?id=57175
Web browser: ---
Bug ID: 57175
Summary: SpecialRecentChanges::doMainQuery query needs tuning
Product: MediaWiki
Version: 1.21.3
Hardware: All
OS: All
Status: NEW
Severity: major
Priority: Unprioritized
Component: Database
Assignee: [email protected]
Reporter: [email protected]
Classification: Unclassified
Mobile Platform: ---
The following query is much slower on MariaDB enwiki with the FORCE INDEX than
without it:
SELECT /* SpecialRecentChanges::doMainQuery */
rc_id,rc_timestamp,rc_cur_time,rc_user,rc_user_text,rc_namespace,rc_title,rc_comment,rc_minor,rc_bot,rc_new,rc_cur_id,rc_this_oldid,rc_last_oldid,rc_type,rc_source,rc_patrolled,rc_ip,rc_old_len,rc_new_len,rc_deleted,rc_logid,rc_log_type,rc_log_action,rc_params,wl_user,wl_notificationtimestamp,ts_tags,fp_stable,fp_pending_since
FROM `recentchanges` FORCE INDEX (rc_timestamp) LEFT JOIN `watchlist` ON
(wl_user = '12744321' AND (wl_title=rc_title) AND (wl_namespace=rc_namespace))
LEFT JOIN `tag_summary` ON ((ts_rc_id=rc_id)) LEFT JOIN `flaggedpages` ON
((fp_page_id = rc_cur_id)) WHERE (rc_timestamp >= '20131018000000') AND rc_bot
= '0' AND (rc_namespace = '828') AND (rc_type != 5) AND rc_new IN ('0','1')
ORDER BY rc_timestamp DESC LIMIT 500
With force: > 1 minute, a slow range scan on rc_timestamp, ~2 million rows.
Without force: < 3 seconds, a fast ref lookup on rc_namespace_title with cheap
filesort, ~1000 rows.
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