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Re: Inlining comparators as a performance optimisation

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(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: 2011-12-02 20:42:21
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Lists: pgsql-hackers
Robert Haas wrote:
> On Fri, Dec 2, 2011 at 2:35 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > Agreed. ?Doing something once and doing something in the sort loop are
> > two different overheads.
> OK, so I tried to code this up.  Adding the new amproc wasn't too
> difficult (see attached).  It wasn't obvious to me how to tie it into
> the tuplesort infrastructure, though, so instead of wasting time
> guessing what a sensible approach might be I'm going to use one of my
> lifelines and poll the audience (or is that ask an expert?).
> Currently the Tuplesortstate[1] has a pointer to an array of
> ScanKeyData objects, one per column being sorted.  But now instead of
> "FmgrInfo sk_func", the tuplesort code is going to want each scankey
> to contain "SortSupportInfo(Data?) sk_sortsupport"[2], because that's
> where we get the comparison function from.   Should I just go ahead
> and add one more member to that struct, or is there some more
> appropriate way to handle this?

Is this code immediately usable anywhere else in our codebasde, and if
so, is it generic enough?

  Bruce Momjian  <bruce(at)momjian(dot)us>

  + It's impossible for everything to be true. +

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