Joins Usage Clarification

[Nishant Gupta]

Hi Team,

There are 3 types of window join (Tumbling, Session, and Sliding) and 1 interval Join as mentioned in (For Table API)
[1] https://ci.apache.org/projects/flink/flink-docs-release-1.9/dev/stream/operators/joining.html

Plus, there is 1 Time window Join as mentioned in (For SQL)

[2] https://ci.apache.org/projects/flink/flink-docs-release-1.9/dev/table/sql.html#joins 

Need some clarifications/answers to below doubts
1. Can some one help me understand how Time window join is different from Interval Join. Looks like same to me

2. How do I implement session window join in Flink SQL? With an example would be appreciated.

Thanks

Nishant 

 

[Fabian Hueske-2]

Hi Nishant,

To answer your questions:

1) yes, the SQL time-windowed join and the DataStream API Interval Join are the same (with different implementations though)

2) DataStream Session-window joins are not directly supported in SQL. You can play some tricks to make it work, but it wouldn't be elegant and to be honest, the semantics of the session-window join are not really meaningful, IMO.

Fabian

Am Mi., 25. Sept. 2019 um 11:26 Uhr schrieb Nishant Gupta <[hidden email]>:

Hi Team,

There are 3 types of window join (Tumbling, Session, and Sliding) and 1 interval Join as mentioned in (For Table API)
[1] https://ci.apache.org/projects/flink/flink-docs-release-1.9/dev/stream/operators/joining.html

Plus, there is 1 Time window Join as mentioned in (For SQL)

[2] https://ci.apache.org/projects/flink/flink-docs-release-1.9/dev/table/sql.html#joins 

Need some clarifications/answers to below doubts
1. Can some one help me understand how Time window join is different from Interval Join. Looks like same to me

2. How do I implement session window join in Flink SQL? With an example would be appreciated.

Thanks

Nishant