Re: Very strange postgresql behaviour

Arnau <arnaulist@andromeiberica.com> writes:
>    I have postgresql 7.4.2 running on debian and I have the oddest
> postgresql behaviour I've ever seen.

Is this specific to these two rows?  If so it might be a case of this
bug, which was repaired in 7.4.13:

http://archives.postgresql.org/pgsql-general/2006-05/msg00756.php
http://archives.postgresql.org/pgsql-committers/2006-05/msg00174.php

2006-05-19 12:31  tgl

    * src/backend/executor/nodeIndexscan.c (REL7_4_STABLE): Fix nasty
    bug in nodeIndexscan.c's detection of duplicate tuples during a
    multiple (OR'ed) indexscan.  It was checking for duplicate
    tuple->t_data->t_ctid, when what it should be checking is
    tuple->t_self.    The trouble situation occurs when a live tuple has
    t_ctid not pointing to itself, which can happen if an attempted
    UPDATE was rolled back.  After a VACUUM, an unrelated tuple could
    be installed where the failed update tuple was, leading to one live
    tuple's t_ctid pointing to an unrelated tuple.    If one of these
    tuples is fetched by an earlier OR'ed indexscan and the other by a
    later indexscan, nodeIndexscan.c would incorrectly ignore the
    second tuple.  The bug exists in all 7.4.* and 8.0.* versions, but
    not in earlier or later branches because this code was only used in
    those releases.  Per trouble report from Rafael Martinez Guerrero.

REINDEX wouldn't fix this, although a table dump and reload would.

            regards, tom lane

PS: please don't spam multiple lists with the same question.