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Re: Inlining comparators as a performance optimisation

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, Peter Geoghegan <peter(at)2ndquadrant(dot)com>, PG Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Inlining comparators as a performance optimisation
Date: 2011-09-21 16:27:49
Message-ID: 24658.1316622469@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> On 21.09.2011 18:46, Tom Lane wrote:
>> Well, we'd have to negotiate what the API ought to be.  What I'm
>> envisioning is that datatypes could provide alternate comparison
>> functions that are designed to be qsort-callable rather than
>> SQL-callable.  As such, they could not have entries in pg_proc, so
>> it seems like there's no ready way to represent them in the catalogs.

> Quite aside from this qsort-thing, it would be nice to have versions of 
> all simple functions that could be called without the FunctionCall 
> overhead.

Hmm, that's an interesting idea.  I think probably the important aspects
are (1) known number of arguments and (2) no null argument or result
values are allowed.  Not sure what we'd do with collations though.

> We could have an extended version of the PG_FUNCTION_INFO_V1 macro that 
> would let you register the fastpath function:
> PG_FUNCTION_INFO_V1(int4pl, int4pl_fastpath);

We don't use PG_FUNCTION_INFO_V1 for built-in functions ...

			regards, tom lane

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