Greg Stark <gsstark@mit.edu> writes:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
>> There is some stuff in the literature about how to make transformations
>> of the last kind, but it requires additional executor smarts to do strange
>> sorts of "generalized outer join" operations.

> Would these "generalized outer join" operations be general enough to handle IN
> semantics? Or other subqueries?

No, AFAICT it's just a weird way of defining a join operation.

I did find some papers that talked about ways to push joins up and down
past aggregations and GROUP BY, but that's a problem for another day.

regards, tom lane

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