Bug #7531
closed
Duplicate users in userlist
Description
If a user has more than 1 usergroup they will display more than once in a userlist. This is due to the inner join of the usergroup mapping table. Adding DISTINCT back causes a performance decrease at the magnitude of 600x. Causing significant performance loss. Example as follows.
Current: 0.0311 seconds
GROUP BY: 20.4404 seconds
DISTINCT: 154.7703 seconds
Updated by krileon over 5 years ago
SUBQUERY: 0.0311 seconds
Subquery optimizes away the same as current. This maybe the best, if not only, solution for optimal performance. It results in full indexing, including of the subquery, preventing full scans. If subquery can't be used (e.g. if the usergroup table is accessed by its join alias elsewhere) then GROUP BY is best.
Updated by krileon over 5 years ago
- Status changed from Assigned to Resolved
- % Done changed from 0 to 100
Fixed in MR !1469 by changing the usergroups join to a subquery