Martin Devera <devik@cdi.cz> writes:
> Inner semijoin scans its left input outputting all rows which
> has its pair in right input but doesn't duplicate result when
> there are duplicates at right.
> The WHERE IN(select...), corelated EXISTS and ANY are
> converted to it. This semijoin is simple to efectively implement
> for all physical join types.
> NOT IN, NOT EXISTS and ALL uses anti-semi-inner-join. The
> join outputs lefts which can't be paired and don't duplicate
> others. Again, simple implementation.
> Have anyone thought about it ?
Yes, this is exactly what I was thinking of doing in 7.2 or so ...
regards, tom lane
