instance method query_cache

# File activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb, line 201
      def query_cache
        if @pinned && @owner != ActiveSupport::IsolatedExecutionState.context
          # With transactional tests, if the connection is pinned, any thread
          # other than the one that pinned the connection need to go through the
          # query cache pool, so each thread get a different cache.
          pool.query_cache
        else
          @query_cache
        end
      end