exclude 'closed' versions or releases from droppables

[fuminori-ido-m]

Issue

In lib/backlogs_project_patch.rb, ProjectPatch::InstanceMethods#_sql_for_droppables gather infos of [projects.id, versions/releases ids under the projects], which will be used to check a story can be dragged&dropped on the page.

When the number of versions and/or releases become large, two problems arise:

• A) the SQL takes long time (e.g. 26 seconds under Versions.count ~= 900 and projects.count ~= 240 our case).
• B) In MySQL, GROUP_CONCAT default max length is 1024 chars so that the _sql_for_droppables method easily exeeds at our case; the result is chopped so that incorrect value is returned.

Solution for A

I think the closed versions and releases should be excluded from droppables because they are not used at backlog page, am I right?

This PR is for A.

(Solution for B would tune MySQL server parameter or session(SET SESSION group_concat_max_len = ...))

[fuminori-ido-m]

I wrote:

I think the closed versions and releases should be excluded from droppables because they are not used at backlog page, am I right?

but I am not sure so that I'm asking the same question at the origin. Even though my understanding is right or not, taking long time at this droppable SQL has no meaning because drag&drop doesn't work at project-tree as I am asking.

[ghost]

just wondering.

as time passes by, the number of closed tickets will increase but the number of open tickets expects to be pretty much the same if usage stays in the same way.

does this use an appropriate index available?
are there any more suitable indexes if we change the order of where condition?

drp.status <> 'closed'

[fuminori-ido-m]

Thank you for your pointing out about indexing! I didn't think about that.

...However, I have no idea how to tune around the index of this SQL even though I tried to explain it. That should be a task to resolve.