Thank to everybody, I recompiled Postgres and tested it on the same DB : the offending SELECT worked, without any index
regeneration.Maybe the order in which the items where inserted in the table (using COPY, before creating the index)
madeit working.
I only had problems with the source RPMs : I installed it (6.5.2), added a patch file for this, recompiled, but wasn't
ableto get brand new RPM package for installing on my other machines...
What I did for testing my compilation with the fresh "postgres" binary, is installing it in /usr/bin, in place of the
otherone. Is it the only think to do, or will there be side effects if I don't install more binaries ?
Maybe Lamar Owen could help me getting a fresh patched RPM ?
Nicolas Huillard
-----Message d'origine-----
De: Tom Lane [SMTP:tgl@sss.pgh.pa.us]
Date: vendredi 28 janvier 2000 05:49
À: John Brothers
Cc: pgsql-general@hub.org; pgsql-sql@hub.org
Objet: Re: [SQL] RE: [GENERAL] Problem with SELECT on large negative INT4
John Brothers <johnbr@mindspring.com> writes:
> I don't think that patch will work - Hiroshi whipped up that patch for
> me a week ago for a different problem - we have a table with duplicate
> primary keys, which seems to be an arithmetic overflow problem because
> the index key values can be both very large positive and very large
> negative numbers.
Actually, if Nicolas' table contains both very large positive and very
large negative integers, then his index could be messed up pretty badly.
What Hiroshi saw (and I missed :-() was that btint4cmp can fail and
return a result of the wrong sign if the difference between two integers
overflows. Since index sorting depends critically on the assumption
that the comparator always returns consistent results (a < b and b < c
must imply a < c, but this can fail if a - c overflows), you could have
an out-of-order index. And then probes into the index could fail to
find items they should find ... which is exactly the complained-of
symptom.
Hiroshi neglected to mention that you'd probably need to drop and
recreate the index after applying the patch; if it's indeed out of
order, just patching the comparator bug isn't enough to fix it.
regards, tom lane
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