Re: Using 128-bit integers for sum, avg and statistics aggregates

From: Andreas Karlsson <andreas(at)proxel(dot)se>
To: Petr Jelinek <petr(at)2ndquadrant(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Peter Geoghegan <pg(at)heroku(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Using 128-bit integers for sum, avg and statistics aggregates
Date: 2015-03-22 12:59:22
Message-ID: 550EBCAA.6030004@proxel.se
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On 03/22/2015 11:47 AM, Petr Jelinek wrote:
> On 22/03/15 10:35, Andres Freund wrote:
>>> http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=jacana&dt=2015-03-21%2003%3A01%3A21
>>>
>>
>> That's the stuff looking like random memory that I talk about above...
>>
>
> If you look at it closely, it's actually not random memory. At least in
> the first 2 failing tests which are not obfuscated by aggregates on top
> of aggregates. It looks like first NumericDigit is ok and the second one
> is corrupted (there are only 2 NumericDigits in those numbers). Of
> course the conversion to Numeric is done from the end so it looks like
> only the last computation/pointer change/something stays ok while the
> rest got corrupted.

Would this mean the bug is most likely somewhere in
int128_to_numericvar()? Maybe that version of gcc has a bug in some
__int128 operator or I messed up the code there somehow.

Andreas

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