QueryCache not working in Capybara transactional tests

[engwan]

Steps to reproduce

When transactional_tests are enabled, requests to the Capybara web server don't have query cache enabled.

In the controller, ActiveRecord::Base.connection.query_cache_enabled is false

Expected behavior

The connection has query cache enabled

Actual behavior

The query cache middleware enables query caching on the pool. But since we have transactional_tests, when we get a connection, we return the shared connection (based on @lock_thread) instead of checking out a connection from the pool.

I think this means https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb#L13 would not be triggered, causing query cache to not be enabled for the request

Additional information

We want query cache enabled in test so that it is closer to what happens in development / production. We have tests that check for the number of uncached queries that are now failing after enabling transactional_tests.

System configuration

Rails version: 5.1.7

Ruby version: 2.6.3

[engwan]

cc @eileencodes I'm not sure if this is intended behavior?

[engwan]

Having this patch fixes the issue:

module ActiveRecord
  module ConnectionAdapters
    module QueryCache
      module ConnectionPoolConfiguration
        def enable_query_cache!
          @query_cache_enabled[connection_cache_key(@lock_thread || Thread.current)] = true
          connection.enable_query_cache! if active_connection?
        end

        def disable_query_cache!
          @query_cache_enabled.delete connection_cache_key(@lock_thread || Thread.current)
          connection.disable_query_cache! if active_connection?
        end

        def query_cache_enabled
          @query_cache_enabled[connection_cache_key(@lock_thread || Thread.current)]
        end
      end
    end

    class ConnectionPool
      def active_connection?
        @thread_cached_conns[connection_cache_key(@lock_thread || Thread.current)]
      end
    end
  end
end

[eileencodes]

Do you want to send a PR @engwan?

[engwan]

Sure. I'll look at adding tests for this and send a PR