Re: Current int & float overflow checking is slow.

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2017-10-25T05:33:46Z
Lists: pgsql-hackers
On Tue, Oct 24, 2017 at 9:28 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I don't like changing well-defined, user-visible query behavior for
> no other reason than a performance gain (of a size that hasn't even
> been shown to be interesting, btw).  Will we change it back in another
> ten years if the performance tradeoff changes?
>
> Also, if I recall the old discussion properly, one concern was getting
> uniform behavior across different platforms.  I'm worried that if we do
> what Andres suggests, we'll get behavior that is not only different but
> platform-specific.  Now, to the extent that you believe that every modern
> platform implements edge-case IEEE float behavior the same way, that worry
> may be obsolete.  But I don't think I believe that.

Yeah, those are reasonable concerns.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


Commits

  1. Provide overflow safe integer math inline functions.

  2. Use new overflow aware integer operations.