adopt_connection

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 1258
        def adopt_connection(conn)
          conn.pool = self
          @connections << conn

          # We just created the first connection, it's time to load the schema
          # cache if that wasn't eagerly done before
          if @schema_cache.nil? && ActiveRecord.lazily_load_schema_cache
            schema_cache.load!
          end
        end