38 lines
1.4 KiB
Markdown
38 lines
1.4 KiB
Markdown
# Verifying Database Capabilities
|
|
|
|
Sometimes certain bits of code may only work on a certain database and/or
|
|
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?`: returns `true` if PostgreSQL is being used
|
|
* `Gitlab::Database.mysql?`: returns `true` if MySQL is being used
|
|
* `Gitlab::Database.version`: returns the PostgreSQL version number as a string
|
|
in the format `X.Y.Z`. This method does not work for MySQL
|
|
|
|
This allows you to write code such as:
|
|
|
|
```ruby
|
|
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`).
|