kafka-connect: correct partition transform support

[ajantha-bhat]

plurals are not standard syntax as per spec.
https://iceberg.apache.org/spec/#partition-transforms

Hence, we should not support it.

[Fokko]

What's the harm of supporting plurals? For example, Spark is plural as well. This might also break backward compatibility since this already went out with 1.5.0.

[ajantha-bhat]

What's the harm of supporting plurals? For example, Spark is plural as well. This might also break backward compatibility since this already went out with 1.5.0.

• Connector is not usable from 1.5.0. So, I don't think we have to worry about compatibility.
• Spark it was a UDF and Spark plural was confusing (plus not as per spec) and we corrected it in 1.3.0 and kept older format for compatibility. But when we are adding freshly we can adhere to spec.

[bryanck]

I'd rather keep the plurals to avoid the trial-and-error approach of figuring out which works. As Fokko pointed out, Spark uses plurals for the transforms.

[ajantha-bhat]

I'd rather keep the plurals to avoid the trial-and-error approach of figuring out which works. As Fokko pointed out, Spark uses plurals for the transforms.

I still think it is good to have spec aligned configs as we are introducing it newly. Just because we made a mistake at Spark, we don't have to follow it. We can have docs and examples for users to make things easier (instead of figuring out). Lets see what others think.

[amogh-jahagirdar]

I don't really consider it a mistake to have the plural form. The exposed syntax and the actual metadata which is spec compliant are independent concerns. For the metadata we already know we're writing the spec compliant representation of the transform. For the syntax I believe we should optimize for user experience, and I think having both options available just makes it easier since it's easy for someone to punch in the plural form (with minimal code maintenance concerns).

Put another way, I don't think the common user is trying to correlate the syntax and expect the exact same representation in the metadata; they mostly would care that it's a good experience and that what is written to metadata is spec compliant IMO.

[ajantha-bhat]

closing this as many people don't see it as a problem.