Add an index on issues.parent_id
|Assignee:||Jean-Philippe Lang||% Done:|
We encounter slowness with using the scrum plugin (https://redmine.ociotec.com/projects/redmine-plugin-scrum).
It happens when dragging issue in the backlog.
It seems that the slowness comes from the fact that there is no index on the parent_id field of the issues table :
Here we have more than 500.000 issues
and for example a simple
SELECT COUNT(*) FROM `issues` WHERE `issues`.`parent_id` = 520784 takes 0.28 seconds
The slow method is all_dependent_issues.
Aside from the use of this plugin, on issues with children, a request is made on the parent_id field, that takes a few hundreds of milli-seconds.
We have added an index on that field, that fixes the issue.
Can this index be added by default in the Redmine migrations ?
Thanks a lot