1. Change multiple updates to a single `update_all`
2. Use cascading deletes
3. Extract an average function for the database median.
4. Move database median to `lib/gitlab/database`
5. Use `delete_all` instead of `destroy_all`
6. Minor refactoring
1. Add indexes to `CreateMergeRequestsClosingIssues` columns.
2. Remove an extraneous `check_if_open` check that is redundant now.
It would've been better to rebase this in, but that's not possible
because more people are working on this branch.
1. These changes bring down page load time for 100 issues from more than
a minute to about 1.5 seconds.
2. This entire commit is composed of these types of performance
enhancements:
- Cache relevant data in `IssueMetrics` wherever possible.
- Cache relevant data in `MergeRequestMetrics` wherever possible.
- Preload metrics
3. Given these improvements, we now only need to make 4 SQL calls:
- Load all issues
- Load all merge requests
- Load all metrics for the issues
- Load all metrics for the merge requests
4. A list of all the data points that are now being pre-calculated:
a. The first time an issue is mentioned in a commit
- In `GitPushService`, find all issues mentioned by the given commit
using `ReferenceExtractor`. Set the `first_mentioned_in_commit_at`
flag for each of them.
- There seems to be a (pre-existing) bug here - files (and
therefore commits) created using the Web CI don't have
cross-references created, and issues are not closed even when
the commit title is "Fixes #xx".
b. The first time a merge request is deployed to production
When a `Deployment` is created, find all merge requests that
were merged in before the deployment, and set the
`first_deployed_to_production_at` flag for each of them.
c. The start / end time for a merge request pipeline
Hook into the `Pipeline` state machine. When the `status` moves to
`running`, find the merge requests whose tip commit matches the
pipeline, and record the `latest_build_started_at` time for each
of them. When the `status` moves to `success`, record the
`latest_build_finished_at` time.
d. The merge requests that close an issue
- This was a big cause of the performance problems we were having
with Cycle Analytics. We need to use `ReferenceExtractor` to make
this calculation, which is slow when we have to run it on a large
number of merge requests.
- When a merge request is created, updated, or refreshed, find the
issues it closes, and create an instance of
`MergeRequestsClosingIssues`, which acts as a join model between
merge requests and issues.
- If a `MergeRequestsClosingIssues` instance links a merge request
and an issue, that issue closes that merge request.
5. The `Queries` module was changed into a class, so we can cache the
results of `issues` and `merge_requests_closing_issues` across
various cycle analytics stages.
6. The code added in this commit is untested. Tests will be added in the
next commit.
