ce830d3c60
`delete_all` doesn't support limit, so you'd need to subquery that. And instead of subquerying with `where(id: query)`, it's better to use an `INNER JOIN`. This method also works with MySQL, while subquerying doesn't (without another layer of subquerying) Reference: https://stackoverflow.com/questions/17892762/mysql-this-version-of-mysql-doesnt-yet-support-limit-in-all-any-some-subqu/17892886#17892886
1.4 KiB
Database helpers
There are a number of useful helper modules defined in /lib/gitlab/database/.
Subquery
In some cases it is not possible to perform an operation on a query. For example:
Geo::EventLog.where('id < 100').limit(10).delete_all
Will give this error:
ActiveRecord::ActiveRecordError: delete_all doesn't support limit
One solution would be to wrap it in another where:
Geo::EventLog.where(id: Geo::EventLog.where('id < 100').limit(10)).delete_all
This works with PostgreSQL, but with MySQL it gives this error:
ActiveRecord::StatementInvalid: Mysql2::Error: This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'
Also, that query doesn't have very good performance. Using a
INNER JOIN with itself is better.
So instead of this query:
SELECT geo_event_log.*
FROM geo_event_log
WHERE geo_event_log.id IN
(SELECT geo_event_log.id
FROM geo_event_log
WHERE (id < 100)
LIMIT 10)
It's better to write:
SELECT geo_event_log.*
FROM geo_event_log
INNER JOIN
(SELECT geo_event_log.*
FROM geo_event_log
WHERE (id < 100)
LIMIT 10) t2 ON geo_event_log.id = t2.id
And this is where Gitlab::Database::Subquery.self_join can help
you. So you can rewrite the above statement as:
Gitlab::Database::Subquery.self_join(Geo::EventLog.where('id < 100').limit(10)).delete_all
And this also works with MySQL, so you don't need to worry about that.