Re: Super PathKeys (Allowing sort order through precision loss functions) - Mailing list pgsql-hackers

From David Rowley
Subject Re: Super PathKeys (Allowing sort order through precision loss functions)
Date
Msg-id CAKJS1f-=HEnwZU0s11xqD9ae0Zho=k=dP2367+yJUrXochhumg@mail.gmail.com
Whole thread Raw
In response to Re: Super PathKeys (Allowing sort order through precision loss functions)  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: Super PathKeys (Allowing sort order through precision lossfunctions)  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
List pgsql-hackers
On 1 November 2018 at 05:40, Robert Haas <robertmhaas@gmail.com> wrote:
> This kinda reminds me of commit
> 8f9fe6edce358f7904e0db119416b4d1080a83aa.  We needed a way to provide
> the planner with knowledge about the behavior of specific functions.
> In that case, the specific need was to be able to tell the planner
> that a certain function call could be omitted or strength-reduced, and
> we did that by having the planner call a function that encoded the
> necessary knowledge.  Here, we want to evaluate a function call and
> see whether it is order preserving, which could depend on a whole
> bunch of stuff that isn't easily parameterized by catalog entries, but
> could be figured out by a C function written for that purpose.  I'm
> not really sure how that would work in this case, or whether it's a
> good idea, but I thought I'd mention it just in case it's helpful.

Agreed. That's a good idea. Thanks.


-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


pgsql-hackers by date:

Previous
From: Darafei "Komяpa" Praliaskouski
Date:
Subject: Parallel threads in query
Next
From: Tom Lane
Date:
Subject: Re: Parallel threads in query