5a574883f9
I noticed the doc/development/testing_guide/best_practices.md still referenced the `[run mysql]` tags, etc. They no longer work, so I removed them, then realised I had better clean up the rest of doc/development !
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Verifying Database Capabilities
Sometimes certain bits of code may only work on a certain database version. While we try to avoid such code as much as possible sometimes it is necessary to add database (version) specific behaviour.
To facilitate this we have the following methods that you can use:
Gitlab::Database.postgresql?: returnstrueif PostgreSQL is being used. You can normally just assume this is the case.Gitlab::Database.version: returns the PostgreSQL version number as a string in the formatX.Y.Z.
This allows you to write code such as:
if Gitlab::Database.postgresql?
if Gitlab::Database.version.to_f >= 9.6
run_really_fast_query
else
run_fast_query
end
else
run_query
end
Read-only database
The database can be used in read-only mode. In this case we have to
make sure all GET requests don't attempt any write operations to the
database. If one of those requests wants to write to the database, it needs
to be wrapped in a Gitlab::Database.read_only? or Gitlab::Database.read_write?
guard, to make sure it doesn't for read-only databases.
We have a Rails Middleware that filters any potentially writing
operations (the CUD operations of CRUD) and prevent the user from trying
to update the database and getting a 500 error (see Gitlab::Middleware::ReadOnly).