The number of forks of a project doesn't change very frequently and
running a COUNT(*) every time this information is requested can be quite
expensive. We also end up running such a COUNT(*) query at least twice
on the homepage of a project.
By caching this data and refreshing it when necessary we can reduce
project homepage loading times by around 60 milliseconds (based on the
timings of https://gitlab.com/gitlab-org/gitlab-ce).
This commit migrates events data in such a way that push events are
stored much more efficiently. This is done by creating a shadow table
called "events_for_migration", and a table called "push_event_payloads"
which is used for storing push data of push events. The background
migration in this commit will copy events from the "events" table into
the "events_for_migration" table, push events in will also have a row
created in "push_event_payloads".
This approach allows us to reclaim space in the next release by simply
swapping the "events" and "events_for_migration" tables, then dropping
the old events (now "events_for_migration") table.
The new table structure is also optimised for storage space, and does
not include the unused "title" column nor the "data" column (since this
data is moved to "push_event_payloads").
== Newly Created Events
Newly created events are inserted into both "events" and
"events_for_migration", both using the exact same primary key value. The
table "push_event_payloads" in turn has a foreign key to the _shadow_
table. This removes the need for recreating and validating the foreign
key after swapping the tables. Since the shadow table also has a foreign
key to "projects.id" we also don't have to worry about orphaned rows.
This approach however does require some additional storage as we're
duplicating a portion of the events data for at least 1 release. The
exact amount is hard to estimate, but for GitLab.com this is expected to
be between 10 and 20 GB at most. The background migration in this commit
deliberately does _not_ update the "events" table as doing so would put
a lot of pressure on PostgreSQL's auto vacuuming system.
== Supporting Both Old And New Events
Application code has also been adjusted to support push events using
both the old and new data formats. This is done by creating a PushEvent
class which extends the regular Event class. Using Rails' Single Table
Inheritance system we can ensure the right class is used for the right
data, which in this case is based on the value of `events.action`. To
support displaying old and new data at the same time the PushEvent class
re-defines a few methods of the Event class, falling back to their
original implementations for push events in the old format.
Once all existing events have been migrated the various push event
related methods can be removed from the Event model, and the calls to
`super` can be removed from the methods in the PushEvent model.
The UI and event atom feed have also been slightly changed to better
handle this new setup, fortunately only a few changes were necessary to
make this work.
== API Changes
The API only displays push data of events in the new format. Supporting
both formats in the API is a bit more difficult compared to the UI.
Since the old push data was not really well documented (apart from one
example that used an incorrect "action" nmae) I decided that supporting
both was not worth the effort, especially since events will be migrated
in a few days _and_ new events are created in the correct format.
This removes the need for relying on Rails' "dependent" option for data
removal, which is _incredibly_ slow (even when using :delete_all) when
deleting large amounts of data. This also ensures data consistency is
enforced on DB level and not on application level (something Rails is
really bad at).
This commit also includes various migrations to add foreign keys to
tables that eventually point to "projects" to ensure no rows get
orphaned upon removing a project.
* upstream/master: (149 commits)
Revert change to design. Go back to scrollable page
Fixes the column widths for the new navigation options in settings
Migrate #submodule_url_for to Gitaly
Add test example for external commit status retries
Fix invalid Rails.logger call in lib/gitlab/health_checks/fs_shards_check.rb
Fix build for !12300.
Log rescued exceptions to Sentry
Fix issues with non-UTF8 filenames by always fixing the encoding of tree and blob paths
Revert "Merge branch 'revert-12499' into 'master'"
Prevent accidental deletion of protected MR source branch by repeating checks before actual deletion
Improve the overall UX for the new monitoring dashboard
Document that GitLab 9.3 requires the TRIGGER permission on MySQL
Instrument Unicorn with Ruby exporter
Remove group modal like remove project modal. Closes#33130
Update prometheus client gem
Enables the option in user preferences to turn on the new navigation
Add Jasmine tests for `OAuthRememberMe`
Simplify authentication logic in the v4 users API for !12445.
Use stub_application_setting when testing ApplicationHelper#support_url
wait_for_requests is not needed when AJAX is not in play
...
In Geo, Project#ensure_repository is used to make sure that a Git repo
is available to be fetched on a secondary. If a project were a fork,
this directory would never be created.
Closesgitlab-org/gitlab-ee#2800
* upstream/master: (123 commits)
Backport changes to Projects::IssuesController and the search bar
bugfix: use `require_dependency` to bring in DeclarativePolicy
Resolve "Select branch dropdown is too close to branch name"
Clean up issuable lists
Defer project destroys within a namespace in Groups::DestroyService#async_execute
Fixed new navgiation bar logo height in Safari
Resolve "Issue dropdown persists when adding issue number to issue description"
Move verification to block level instead of paragraph
Revert "Merge branch 'dm-drop-default-scope-on-sortable-finders' into 'master'"
Added code for defining SHA attributes
Minor edits
Job details won't scroll horizontally to show long lines
Run mysql tests on stable preperation branches like 9-3-stable-patch-2
Bring back branches badge to main project page
optimize translation content based on comments
supplement traditional chinese in taiwan translation
Inserts exact matches of username, email and name to the top of the user search list
Remove Namespace model default scope override and write additional test to Project search
optimize translation content based on comments
Limit OpenGraph image size to 64x64
...
Gabriel Mazetto
Douwe Maan
Tiago Botelho
Nick Thomas
Yorick Peterse
Sean McGivern
Robert Speicher
Rémy Coutable
blackst0ne
Michael Kozono
Jarka Kadlecova
Alexander Randa
Bob Van Landuyt
Grzegorz Bizon
Paul Charlton
Lin Jen-Shin
Grzegorz Bizon
Robert Speicher
Douglas Barbosa Alexandre
Stan Hu