RailsHelpers.stub_rails_env takes care of
stubbing Rails.env

- Also add helper to undo rename_column_concurrently.

- When renaming a column concurrently, drop any existing trigger before
attempting to create a new one.

When running migration specs multiple times (as it happens during
local development), the down method of previous migrations are called.
If any of the called methods contains a call to
rename_column_concurrently, a trigger will be created and not removed.
So, the next time a migration spec is run, if the same down method is
executed again, it will cause an error when attempting to create the
trigger (since it already exists). Dropping the trigger if it already
exists will prevent this problem.

Using the sed script from
https://gitlab.com/gitlab-org/gitlab-ce/issues/59758

None of this code can be reached any more, so it can all be removed

Alexis Kalderimis authored 5 years ago and Mayra Cabrera committed 5 years ago

This improves the `add_timestamps_with_timezone` helper by allowing the
column names to be configured. This has the advantage that unnecessary
columns can be avoided, saving space.

A helper for removing the columns is also provided, to be used in the
`down` method of migrations.

In https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21497, we
migrated all project import data into a separate table,
`project_import_data`.  In addition, we also added:

```
ignore_column :import_status, :import_jid, :import_error
```

In https://gitlab.com/gitlab-com/gl-infra/production/issues/908, we
observed some of these `import_error` columns consumed megabytes of
error backtraces and caused slow loading of projects whenever a `SELECT
* from projects` query loaded the row into memory.

Since we have long migrated away from these columns, we can now drop
these columns entirely.

This is necessary for backporting the EE schema to ensure backported
foreign keys use the same key names.

We want to run CI with rails 4 for a short-term (until we are sure that
we will ship with rails 5). The problem is that rails 4 can not handle
rails 5 schema.rb properly - specifically `t.index` directive can not
handle multiple indexes on the same column.

Because combination of rails 4 + rails 5 schema will be used
only in CI for a short-term, we can just ignore these incompatibility
failures. This patch adds `rails5` helper for specs.

it will decide the method for disable statement_timeout upon
per transaction or per session, based on how it's called.

When calling with a block, block will be executed and it will use
session based statement_timeout, otherwise will default to existing
behavior.

By default statement_timeout will only be enabled during transaction
lifetime, therefore not leaking outside of it.

With `transaction: false` it will set for entire session, but requires
a block to passed. It yields control and cleans up session after block
finishes, also preventing leaking outside of it.

This works the same way as change_column_type_using_background_migration, but
for renaming a column. It takes a table, not a relation, to match its concurrent
counterpart.

Also, generalise the cleanup migrations to reduce code duplication.

This will use the same query as `\di` to find an index on postgresql.

Closes #43887.

Index creation does not have an effect if the index is present already.
Index removal does not have an affect if the index is not present.

This helps to avoid patterns like this in migrations:
```
if index_exists?(...)
  remove_concurrent_index(...)
end
```

Prior to this commit we would essentially update all rows in a table,
even those where the source column (e.g. `issues.closed_at`) was NULL.
This in turn could lead to statement timeouts when using the default
batch size of 10 000 rows per job.

To work around this we don't schedule jobs for rows where the source
value is NULL. We also don't update rows where the source column is NULL
(as an extra precaution) or the target column already has a non-NULL
value. Using this approach it should be possible to update 10 000 rows
in the "issues" table in about 7.5 - 8 seconds.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/42158

This adds a minimum interval to BackgroundMigrationWorker, ensuring
background migrations of the same class only run once every 5 minutes.
This prevents a thundering herd problem where scheduled migrations all
run at once due to their delays having been expired (e.g. as the result
of a queue being paused for a long time).

If a job was recently executed it's rescheduled with a delay that equals
the remaining time of the job's lease. This means that if the lease
expires in two minutes we only need to wait two minutes, instead of
five.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/41624

In a previous attempt (rolled back in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16021) we tried
to migrate `issues.closed_at` from timestamp to timestamptz using a
regular migration. This has a bad impact on GitLab.com and as such was
rolled back.

This commit re-implements the original migrations using generic
background migrations, allowing us to still migrate the data in a single
release but without a negative impact on availability.

To ensure the database schema is up to date the background migrations
are performed inline in development and test environments. We also make
sure to not migrate that that doesn't need migrating in the first place
or has already been migrated.

This adds a bunch of checks to migrations that may create or drop
triggers. Dropping triggers/functions is done using "IF EXISTS" so we
don't throw an error if the object in question has already been dropped.
We now also raise a custom error (message) when the user does not have
TRIGGER privileges. This should prevent the schema from entering an
inconsistent state while also providing the user with enough information
on how to solve the problem.

The recommendation of using SUPERUSER permissions is a bit extreme but
we require this anyway (Omnibus also configures users with this
permission).

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36633