Re: WIP: Faster Expression Processing v4

Andres Freund <andres(at)anarazel(dot)de> writes:
> [ latest patches ]

I looked through 0002-Make-get_last_attnums-more-generic.patch.
Although it seems relatively unobjectionable on its own, I'm not
convinced that it's really useful to try to split it out like this.
I see that 0004 removes the only call of ExecGetLastAttnums (the
one in ExecBuildProjectionInfo) and then adds a single call in
ExecInitExprSlots which is in execExpr.c. To me, the only reason
ExecGetLastAttnums nee get_last_attnums is in execUtils.c in the first
place is that it is a private subroutine of ExecBuildProjectionInfo.
After these changes, it might as well be a private subroutine of
ExecInitExprSlots. I'm suspicious of turning it into a globally
accessible function as you've done here, because I doubt that it is of
global use --- in particular, the fact that it doesn't deal specially
with INDEX_VAR Vars seems rather specific to this one use-case.

So for my money, you should drop 0002 altogether and just have 0004
remove get_last_attnums() from execUtils.c and stick it into
execExpr.c. I suppose you still need the LastAttnumInfo API change
so as to decouple it from ProjectionInfo, but that's minor.

regards, tom lane