Offer advice when ` Window function with empty PARTITION BY is not supported yet` about risingwave

[fuyufjh]

Feature is not yet implemented: Window function with empty PARTITION BY is not supported yet

@stdrc Do you think it's "not yet implemented"? I think we intended to forbid such thing to avoid bad query, just like the case of nested-loop join.

[lmatz]

BTW, if the workaround works for most cases, shouldn't we just rewrite the query automatically?

[fuyufjh]

BTW, if the workaround works for most cases, shouldn't we just rewrite the query automatically?

Had better not to do so. partition by 1, similarly to the nested-loop join trick, will make it impossible to process parallelly and thus easily become a performance bottleneck. Writing partition by 1 also let users know what he is doing.

[stdrc]

Feature is not yet implemented: Window function with empty PARTITION BY is not supported yet

@stdrc Do you think it's "not yet implemented"? I think we intended to forbid such thing to avoid bad query, just like the case of nested-loop join.

Yes we didn't support this because we don't want user to write such bad query very easily.

Although I think give a better error message to advise the user be careful and use "partition by 1" if it's really needed.