Hi all. I'd like to start a discussion of FLIP-392: Deprecate the Legacy Group Window Aggregation.
Although the current Flink SQL Window Aggregation documentation[1] indicates that the legacy Group Window Aggregation syntax has been deprecated, the new Window TVF Aggregation syntax has not fully covered all of the features of the legacy one. Compared to Group Window Aggergation, Window TVF Aggergation has several advantages, such as two-stage optimization, support for standard GROUPING SET syntax, and so on. However, it needs to supplement and enrich the following features. 1. Support for SESSION Window TVF Aggregation 2. Support for consuming CDC stream 3. Support for HOP window size with non-integer step length 4. Support for configurations such as early fire, late fire and allow lateness (which are internal experimental configurations in Group Window Aggregation and not public to users yet.) 5. Unification of the Window TVF Aggregation operator in runtime at the implementation layer (In the long term, the cost to maintain the operators about Window TVF Aggregation and Group Window Aggregation is too expensive.) This flip aims to continue the unfinished work in FLIP-145[2], which is to fully enable the capabilities of Window TVF Aggregation and officially deprecate the legacy syntax Group Window Aggregation, to prepare for the removal of the legacy one in Flink 2.0. I have already done some preliminary POC to validate the feasibility of the related work in this flip as follows. 1. POC for SESSION Window TVF Aggregation [3] 2. POC for CUMULATE in Group Window Aggregation operator [4] 3. POC for consuming CDC stream in Window Aggregation operator [5] Looking forward to your feedback and thoughts! [1] https://nightlies.apache.org/flink/flink-docs-master/docs/dev/table/sql/queries/window-agg/ [2] https://cwiki.apache.org/confluence/display/FLINK/FLIP-145%3A+Support+SQL+windowing+table-valued+function#FLIP145:SupportSQLwindowingtablevaluedfunction-SessionWindows [3] https://github.com/xuyangzhong/flink/tree/FLINK-24024 [4] https://github.com/xuyangzhong/flink/tree/poc_legacy_group_window_agg_cumulate [5] https://github.com/xuyangzhong/flink/tree/poc_window_agg_consumes_cdc_stream -- Best！ Xuyang
