state clean up behavior with flink interval join

0
votes

I am reading at

https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/dev/table/sql/queries/joins/#interval-joins,

It has following example:

SELECT *
FROM Orders o, Shipments s
WHERE o.id = s.order_id
AND o.order_time BETWEEN s.ship_time - INTERVAL '4' HOUR AND s.ship_time

I got following two questions:

  1. If o.order_time and s.ship_time are normal time column, not event time attribute, then all the states will be saved in Flink, like normal regular inner join does? So that, maybe big size states will be kept in Flink

  2. If o.order_time and s.ship_time are event time attributes, then flink will rely on watermark to do state clean up? so that small size states will be kept in Flink

1
apache-flink

1 Answers

1
votes

Yes, that's correct. The reason Flink SQL has the notion of time attributes is so that suitable streaming queries can have their state automatically cleaned up, and an interval join is an example of such a query. Time windows and temporal joins on versioned tables also work in a similar way.