Re: CUBE seems a bit confused about ORDER BY

On Tue, Dec 12, 2017 at 3:49 PM, Teodor Sigaev <teodor(at)sigaev(dot)ru> wrote:

> Yes, the thing is that we change behavior of existing ~> operator. In
>> general, this is not good idea because it could affect existing users whose
>> already use this operator. Typically in such situation, we could leave
>> existing operator as is, and invent new operator with new behavior.
>> However, in this particular case, I think there are reasons to make an
>> exception to the rules. The reasons are following:
>> 1) The ~> operator was designed especially for knn gist.
>> 2) Knn gist support for current behavior is broken by design and can't be
>> fixed. Most we can do to fix existing ~> operator behavior as is to drop
>> knn gist support. But then ~> operator would be left useless.
>> 3) It doesn't seems that ~> operator have many users yet, because an
>> error wasn't reported during whole release cycle.
>>
>> I hope these reasons justify altering behavior of existing operator as an
>> exception to the rules. Another question is whether we should backpatch
>> it. But I think we could leave this decision to committer.
>>
>> I think that this patch is ready for committer.
>>
> I'm agree with changing behavior of existing ~> operator, but is any
> objection here? Current implementation is not fixable and I hope that users
> which use this operator will understand why we change it. Fortunately, the
> fix doesn't require changes in system catalog.
>
> The single question here is about index over expression with this
> operator, they will need to reindex, which should be noted in release notes.

Yes. I bet only few users have built indexes over ~> operator if any. Ask
them to reindex in the release notes seems OK for me.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company