38 lines
1.4 KiB
Markdown
38 lines
1.4 KiB
Markdown
---
|
|
stage: none
|
|
group: unassigned
|
|
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
|
|
---
|
|
|
|
# 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 behavior.
|
|
|
|
To facilitate this we have the following methods that you can use:
|
|
|
|
- `Gitlab::Database.version`: returns the PostgreSQL version number as a string
|
|
in the format `X.Y.Z`.
|
|
|
|
This allows you to write code such as:
|
|
|
|
```ruby
|
|
if Gitlab::Database.version.to_f >= 11.7
|
|
run_really_fast_query
|
|
else
|
|
run_fast_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`).
|