kennknowles commented on pull request #13306: URL: https://github.com/apache/beam/pull/13306#issuecomment-728330950
CombineFn is stable, but UDAF is not. One example is that a UDAF has to have a SQL type. Right now this is not represented on the UDAF object but is implied. That might change. Personally, I would make the type part of the UDAF object. If you look at any other SQL product's definition of UDAFs you will see lots of extra metadata ([postgresql](https://www.postgresql.org/docs/9.5/sql-createaggregate.html), [mssql](https://docs.microsoft.com/en-us/sql/t-sql/statements/create-aggregate-transact-sql?view=sql-server-ver15)). A decoupled interface and trivial wrapper have obvious benefits and no real downside. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
