Arrangement ​

Arrangement stores the state in the dataflow's process. It stores the streams of update flows for further querying and updating.

The arrangement essentially stores key-value pairs with timestamps to mark their change time.

Internally, the arrangement receives tuples like ((Key Row, Value Row), timestamp, diff) and stores them in memory. One can query key-value pairs at a certain time using the get(now: Timestamp, key: Row) method. The arrangement also assumes that everything older than a certain time (also known as the low watermark) has already been ingested to the sink tables and does not keep a history for them.