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Re: Inlining comparators as a performance optimisation

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Peter Geoghegan <peter(at)2ndquadrant(dot)com>, PG Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Inlining comparators as a performance optimisation
Date: 2011-12-07 15:15:35
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Lists: pgsql-hackers
On Wed, Dec 7, 2011 at 10:09 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> There's some stuff that's debatable according to this criterion --- in
> particular, I wondered whether it'd be worth having a fast path for
> bttextcmp, especially if we pre-tested the collate_is_c condition and
> had a separate version that just hardwired the memcmp code path.  (The
> idea of doing that was one reason I insisted on collation being known at
> the setup step.)  But it would still have to be prepared for detoasting,
> so in the end I was unenthused.  Anyone who feels like testing could try
> to prove me wrong about it though.

I think that'd definitely be worth investigating (although I'm not
sure I have the time to do it myself any time real soon).

>> Are you planning to do anything about #2 or #3?
> I am willing to do #2, but not right now; I feel what I need to do next
> is go review SPGist.

Yeah, makes sense.  That one seems likely to be a challenge to absorb.

> I don't believe that #2 blocks progress on #3
> anyway.  I think #3 is in Peter's court, or yours if you want to do it.
> (BTW, I agree with your comments yesterday about trying to break down
> the different aspects of what Peter did, and put as many of them as we
> can into the non-inlined code paths.)

Cool.  Peter, can you rebase your patch and integrate it into the
sortsupport framework that's now committed?

Robert Haas
The Enterprise PostgreSQL Company

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