[Bug] first_value semantic conflict about paimon

[Aitozi]

Thanks @luowanghaoyun for report this. IMO, the aggregate function for first, first_non_null_value, last_non_null_value whose value are not align with the latest sequence may encounter this problem, because the actual "version number " of the value is not kept.

I try to introduce an exclusive sequence for these three kind aggregation field, it should solve this problem, as posted in #3101 But I think it's a bit burden for end user, especially for the aggregation table, the default aggregation function is last_non_null_value. And the exclusive sequence enforce user to config an individual sequence field for these three kind aggregation field.

[liyubin117]

@Aitozi Why not keep the earliest sequence under the mentioned scenarios? I think sequence.field should also be constrainted with the aggregation function.

[Aitozi]

@liyubin117 If we have serval aggregation function fields, a single sequence.field is not enough. The first_value need earliest sequence, but last_value need the latest sequence

[liyubin117]

@Aitozi Thanks for claring that! it is actually more complex than I thought.

[luowanghaoyun]

@Aitozi hi, when is this issue expected to be fixed?