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: | 2011-12-06 17:48:35 |
Message-ID: | CA+TgmoYw_iOWmU36J1Y=X29vyjNEHO3rniO6L4sRwRXYV7X84g@mail.gmail.com |
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Lists: | pgsql-hackers |
On Tue, Dec 6, 2011 at 12:06 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Sun, Dec 4, 2011 at 2:17 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> * We're going to want to expose PrepareSortSupportComparisonShim
>>> for use outside tuplesort.c too, and possibly refactor
>>> tuplesort_begin_heap so that the SortKey setup logic inside it
>>> can be extracted for use elsewhere. Shall we just add those to
>>> tuplesort's API, or would it be better to create a sortsupport.c
>>> with these sorts of functions?
>
>> Why are we going to want to do that? If it's because there are other
>> places in the code that can make use of a fast comparator that don't
>> go through tuplesort.c, then we should probably break it off into a
>> separate file (sortkey.c?). But if it's because we think that clients
>> of the tuplesort code are going to need it for some reason, then we
>> may as well keep it in tuplesort.c.
>
> My expectation is that nbtree, as well as mergejoin and mergeappend,
> would get converted over to use the fast comparator API. I looked at
> that a little bit but didn't push it far enough to be very sure about
> whether they'd be able to share the initialization code from
> tuplesort_begin_heap. But they're definitely going to need the shim
> function for backwards compatibility, and
> PrepareSortSupportComparisonShim was my first cut at a wrapper that
> would be generally useful.
OK. Well, then pushing it out to a separate file probably makes
sense. Do you want to do that or shall I have a crack at it? If the
latter, what do you think about using the name SortKey for everything
rather than SortSupport?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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