This ensures that the "author" association of an event's "target"
association is eager loaded whenever the "target" association defines an
"author" association. This in turn solves the N+1 query problem we first
tried to solve in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15788 but caused
problems when displaying milestones as those don't define an "author"
association.

The approach in this commit does mean that the authors are _always_
eager loaded since this takes place in the "belongs_to" block. This
however shouldn't pose too much of a problem, and as far as I can tell
there's no real way around this unfortunately.

This finishes the procedure for migrating events from the old format
into the new format. Code no longer uses the old setup and the database
tables used during the migration process are swapped, with the old table
being dropped.

While the database migration can be reversed this will 1) take a lot of
time as data has to be coped around 2) won't restore data in the
"events.data" column as we have no way of restoring this.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/37241

This changes the style of push events that remove tags or branches so
they don't display the commit details. This prevents displaying commit
details such as:

    000000 . --broken encoding

Instead we now simply display the header such as:

    Administrator deleted branch example-branch

This is displayed in the same style as events for newly created
branches/tags.

This commit also ensures that if no commit message is present we simply
don't display anything, instead of "--broken encoding".

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36685
Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36722

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.

Remove superfluous lib: true, type: redis, service: true, models: true, services: true, no_db: true, api: true
Signed-off-by: NRémy Coutable <remy@rymai.me>

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

With events no longer being cached this is no longer needed.

Signed-off-by: NRémy Coutable <remy@rymai.me>

Respect project visibility settings in the contributions calendar

This MR fixes a number of bugs relating to access controls and date selection of events for the contributions calendar

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23403

See merge request !2019
Signed-off-by: NRémy Coutable <remy@rymai.me>

At the moment we cannot see weather a user left a project due to their
membership expiring of if they themselves opted to leave the project.
This adds a new event type that allows us to make this differentiation.
Note that is not really feasable to go back and reliably fix up the
previous events. As a result the events for previous expire removals
will remain the same however events of this nature going forward will be
correctly represented.

At the moment we cannot see weather a user left a project due to their
membership expiring of if they themselves opted to leave the project.
This adds a new event type that allows us to make this differentiation.
Note that is not really feasable to go back and reliably fix up the
previous events. As a result the events for previous expire removals
will remain the same however events of this nature going forward will be
correctly represented.

Per GitLab.com's performance metrics this method could take up to 5
seconds of wall time to complete, while only taking 1-2 milliseconds of
CPU time. Removing the Redis lease in favour of conditional updates
allows us to work around this.

A slight drawback is that this allows for multiple threads/processes to
try and update the same row. However, only a single thread/process will
ever win since the UPDATE query uses a WHERE condition to only update
rows that were not updated in the last hour.

Fixes gitlab-org/gitlab-ce#22473

The lock in turn is only obtained when actually needed, reducing some
load on Redis.

Fixes gitlab-org/gitlab-ce#22213

Signed-off-by: NRémy Coutable <remy@rymai.me>

Signed-off-by: NRémy Coutable <remy@rymai.me>

This reverts commit 13e37a3e.

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

In 8278b763 the default behaviour of annotation
has changes, which was causing a lot of noise in diffs. We decided in #17382
that it is better to get rid of the whole annotate gem, and instead let people
look at schema.rb for the columns in a table.

Fixes: #17382

Signed-off-by: NRémy Coutable <remy@rymai.me>

By simply loading the first event from the already sorted set we save
ourselves extra (slow) queries just to get the latest update timestamp.
This removes the need for Event.latest_update_time and significantly
reduces the time needed to build an Atom feed.

Fixes gitlab-org/gitlab-ce#12415

This will be used to move some querying logic from the users controller
to the Event model (where it belongs).

Instead of using MAX(events.updated_at) we can simply sort the events in
descending order by the "id" column and grab the first row. In other
words, instead of this:

    SELECT max(events.updated_at) AS max_id
    FROM events
    LEFT OUTER JOIN projects   ON projects.id   = events.project_id
    LEFT OUTER JOIN namespaces ON namespaces.id = projects.namespace_id
    WHERE events.author_id IS NOT NULL
    AND events.project_id IN (13083);

we can use this:

    SELECT events.updated_at AS max_id
    FROM events
    LEFT OUTER JOIN projects   ON projects.id   = events.project_id
    LEFT OUTER JOIN namespaces ON namespaces.id = projects.namespace_id
    WHERE events.author_id IS NOT NULL
    AND events.project_id IN (13083)
    ORDER BY events.id DESC
    LIMIT 1;

This has the benefit that on PostgreSQL a backwards index scan can be
used, which due to the "LIMIT 1" will at most process only a single row.
This in turn greatly speeds up the process of grabbing the latest update
time. This can be confirmed by looking at the query plans. The first
query produces the following plan:

    Aggregate  (cost=43779.84..43779.85 rows=1 width=12) (actual time=2142.462..2142.462 rows=1 loops=1)
      ->  Index Scan using index_events_on_project_id on events  (cost=0.43..43704.69 rows=30060 width=12) (actual time=0.033..2138.086 rows=32769 loops=1)
            Index Cond: (project_id = 13083)
            Filter: (author_id IS NOT NULL)
    Planning time: 1.248 ms
    Execution time: 2142.548 ms

The second query in turn produces the following plan:

    Limit  (cost=0.43..41.65 rows=1 width=16) (actual time=1.394..1.394 rows=1 loops=1)
      ->  Index Scan Backward using events_pkey on events  (cost=0.43..1238907.96 rows=30060 width=16) (actual time=1.394..1.394 rows=1 loops=1)
            Filter: ((author_id IS NOT NULL) AND (project_id = 13083))
            Rows Removed by Filter: 2104
    Planning time: 0.166 ms
    Execution time: 1.408 ms

According to the above plans the 2nd query is around 1500 times faster.
However, re-running the first query produces timings of around 80 ms,
making the 2nd query "only" around 55 times faster.