From: | Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Mark Wong <mark(at)2ndQuadrant(dot)com> |
Cc: | Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Odd 9.4, 9.3 buildfarm failure on s390x |
Date: | 2018-10-01 20:58:21 |
Message-ID: | c953db2d-2702-dbf9-8c61-e78e9c68bcdc@2ndQuadrant.com |
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Lists: | pgsql-hackers |
On 10/01/2018 11:58 AM, Tom Lane wrote:
> Mark Wong <mark(at)2ndQuadrant(dot)com> writes:
>> a | a | uuid_cmp
>> --------------------------------------+--------------------------------------+-------------
>> 11111111-1111-1111-1111-111111111111 | 11111111-1111-1111-1111-111111111111 | 0
>> 11111111-1111-1111-1111-111111111111 | 22222222-2222-2222-2222-222222222222 | -2147483648
>> 11111111-1111-1111-1111-111111111111 | 3f3e3c3b-3a30-3938-3736-353433a2313e | -2147483648
>> 22222222-2222-2222-2222-222222222222 | 11111111-1111-1111-1111-111111111111 | 1
>> 22222222-2222-2222-2222-222222222222 | 22222222-2222-2222-2222-222222222222 | 0
>> 22222222-2222-2222-2222-222222222222 | 3f3e3c3b-3a30-3938-3736-353433a2313e | -2147483648
>> 3f3e3c3b-3a30-3938-3736-353433a2313e | 11111111-1111-1111-1111-111111111111 | 1
>> 3f3e3c3b-3a30-3938-3736-353433a2313e | 22222222-2222-2222-2222-222222222222 | 1
>> 3f3e3c3b-3a30-3938-3736-353433a2313e | 3f3e3c3b-3a30-3938-3736-353433a2313e | 0
>> (9 rows)
>
> Oooh ... apparently, on that platform, memcmp() is willing to produce
> INT_MIN in some cases. That's not a safe value for a sort comparator
> to produce --- we explicitly say that somewhere, IIRC. I think we
> implement DESC by negating the comparator's result, which explains
> why only the DESC case fails.
>
>
Is there a standard that forbids this, or have we just been lucky up to now?
cheers
andrew
--
Andrew Dunstan https://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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