Every project page displays a navigation menu that in turn displays the
number of open issues and merge requests. This means that for every
project page we run two COUNT(*) queries, each taking up roughly 30
milliseconds on GitLab.com. By caching these numbers and refreshing them
whenever necessary we can reduce loading times of all these pages by up
to roughly 60 milliseconds.
The number of open issues does not include confidential issues. This is
a trade-off to keep the code simple and to ensure refreshing the data
only needs 2 COUNT(*) queries instead of 3. A downside is that if a
project only has 5 confidential issues the counter will be set to 0.
Because we now have 3 similar counting service classes the code
previously used in Projects::ForksCountService has mostly been moved to
Projects::CountService, which in turn is reused by the various service
classes.
Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36622
Having two states that essentially mean the same thing is very much like
having a boolean "true" and boolean "mostly-true": it's rather silly.
This commit merges the "reopened" state into the "opened" state while
taking care of system notes still showing messages along the lines of
"Alice reopened this issue".
A big benefit from having only two states (opened and closed) is that
indexing and querying becomes simpler and more performant. For example,
to get all the opened queries we no longer have to query both states:
SELECT *
FROM issues
WHERE project_id = 2
AND state IN ('opened', 'reopened');
Instead we can query a single state directly, which can be much faster:
SELECT *
FROM issues
WHERE project_id = 2
AND state = 'opened';
Further, only having two states makes indexing easier as we will only
ever filter (and thus scan an index) using a single value. Partial
indexes could help but aren't supported on MySQL, complicating the
development process and not being helpful for MySQL.
Mark Chao