Re: BRIN range operator class

> Judging from a quick look, I think patches 1 and 5 can be committed
> quickly; they imply no changes to other parts of BRIN.  (Not sure why 1
> and 5 are separate.  Any reason for this?)  Also patch 2.

Not much reason except that 1 includes only functions, but 5 includes operators.

> Patch 4 looks like a simple bugfix (or maybe a generalization) of BRIN
> framework code; should also be committable right away.  Needs a closer
> look of course.
>
> Patch 3 is a problem.  That code is there because the union proc is only
> used in a corner case in Minmax, so if we remove it, user-written Union
> procs are very likely to remain buggy for long.  If you have a better
> idea to test Union in Minmax, or some other way to turn that stuff off
> for the range stuff, I'm all ears.  Just lets make sure the support
> procs are tested to avoid stupid bugs.  Before I introduced that, my
> Minmax Union proc was all wrong.

I removed this test because I don't see a way to support it.  I
believe any other implementation that is more complicated than minmax
will fail in there.  It is better to cache them with the regression
tests, so I tried to improve them.  GiST, SP-GiST and GIN don't have
similar checks, but they have more complicated user defined functions.

> Patch 7 I don't understand.  Will have to look closer.  Are you saying
> Minmax will depend on Btree opclasses?  I remember thinking in doing it
> that way at some point, but wasn't convinced for some reason.

No, there isn't any additional dependency.  It makes minmax operator
classes use the procedures from the pg_amop instead of adding them to
pg_amproc.

It also makes the operator class safer for cross data type usage.
Actually, I just checked and find out that we got wrong answers from
index on the current master without this patch.  You can reproduce it
with this query on the regression database:

select * from brintest where timestampcol = '1979-01-29 11:05:09'::timestamptz;

inclusion-opclasses patch make it possible to add cross type brin
regression tests.  I will add more of them on the next version.

> Patch 6 seems the real meat of your own stuff.  I think there should be
> a patch 8 also but it's not attached ... ??

I had another commit not to intended to be sent.  Sorry about that.