AR 3.2 pool patch for less contention on release_connection

pool.rb

  ::ActiveRecord::ConnectionAdapters::ConnectionPool.class_eval do

    def release_connection(with_id = current_connection_id)
      #synchronize do
        conn = @reserved_connections.delete(with_id)
        checkin conn, true if conn
      #end
    end

    def checkin(conn, on_release = nil)
      synchronize do
        conn.run_callbacks :checkin do
          conn.expire
          @queue.signal
        end

        release conn unless on_release
      end
    end

    def release(conn)
      #synchronize do
        thread_id = nil

        if @reserved_connections[current_connection_id] == conn
          thread_id = current_connection_id
        else
          thread_id = @reserved_connections.keys.find { |k|
            @reserved_connections[k] == conn
          }
        end

        @reserved_connections.delete thread_id if thread_id
      #end
    end
    
  end