Database configurations can now be flagged as "replicas", indicating that the database they connect to is read-only.
For now this just means they're ignored by database tasks like db:create, but the comments on the pull request mention some other features that could be built on top of this change.
Initially this patch looked like a micro-optimisation, but the author produced a benchmark which demonstrated saving 1% of both memory and time on a real world Rails app.
Previously, inverse associations would only be detected when they matched the model name exactly. Now, the case where they use the plural form of the model name will work too.
This change ensures that a record's view of the database is up to date immediately after an around callback yields, just as it would be in an after callback.
