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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Steve <cheetah@tanabi.org>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Strangely Variable Query Performance
Date: Thu, 12 Apr 2007 18:22:49 -0400
Message-ID: <9457.1176416569@sss.pgh.pa.us> (raw)
In-Reply-To: <Pine.GSO.4.64.0704121757060.17955@kittyhawk.tanabi.org>
References: <57271CC2-BCB1-4ACA-A177-4FF64F1BC33F@brandeis.edu>
	<E1HbzJr-0005VG-GC@elasmtp-curtail.atl.sa.earthlink.net>
	<16E9A17C-ADFA-43B2-B7EA-5C7A4D7E96D1@event-s.net>
	<E1Hc0lc-0001iE-La@elasmtp-banded.atl.sa.earthlink.net>
	<0914C05F-BA1B-4A6C-A1B1-52256BC851A4@event-s.net>
	<1176396964.13754.16.camel@state.g2switchworks.com>
	<Pine.LNX.4.64.0704121000570.32187@glacier.frostconsultingllc.com>
	<Pine.GSO.4.64.0704121653030.17955@kittyhawk.tanabi.org>
	<5772.1176413092@sss.pgh.pa.us>
	<Pine.GSO.4.64.0704121735000.17955@kittyhawk.tanabi.org>
	<9213.1176415301@sss.pgh.pa.us>
	<Pine.GSO.4.64.0704121757060.17955@kittyhawk.tanabi.org>

Steve <cheetah@tanabi.org> writes:
> Datum   ddd_text_revcmp(PG_FUNCTION_ARGS){
>          char*           arg1=(char*)VARDATA(PG_GETARG_TEXT_P(0));
>          char*           arg2=(char*)VARDATA(PG_GETARG_TEXT_P(1));

>          if((*arg1) != (*arg2)){
>                  PG_RETURN_INT32(*arg2 - *arg1);
>          }else{
>                  PG_RETURN_INT32(strcmp(arg2,arg1));
>          }
> }

[ itch... ]  That code is just completely wrong, because the contents
of a TEXT datum aren't guaranteed null-terminated.  It'd be better to
invoke bttextcmp and negate its result.

That's not relevant to your immediate problem, but if you've noticed
any strange behavior with your text_revop indexes, that's the reason...

			regards, tom lane



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