Re: Bug in PostgreSQL

From: Andres Freund
Subject: Re: Bug in PostgreSQL
Date: ,
Msg-id: 20180628161316.jbzzo76kzcmczh2r@alap3.anarazel.de
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In response to: Re: Bug in PostgreSQL  (Laurenz Albe)
List: pgsql-performance

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Bug in PostgreSQL  (Rambabu V, )
 Re: Bug in PostgreSQL  (Steve Crawford, )
  Re: Bug in PostgreSQL  (Joseph Curtin, )
 Re: Bug in PostgreSQL  (Laurenz Albe, )
  Re: Bug in PostgreSQL  (Andres Freund, )

Hi,

On 2018-06-28 08:55:21 +0200, Laurenz Albe wrote:
> Rambabu V wrote:
> > While taking pgdump we are getting error message cache lookup failed for function 7418447.
> > While trying select * from pg_proc where oid=7418447 returns zero rows. Please help us on this. 
> 
> That means that some catalog data are corrupted.

It does *NOT* have mean that. You can get such reports e.g. because
there was concurrent DDL. Most things are protected against via locks,
but there's enough of a window between getting the list of objects and
locking to cause issues for tables. And for functions it's fairly easy
to get into trouble because there's a mismatch between the snapshot
pg_dump uses (a normal transactional snapshot) and the snapshot used to
deparse expressions etc (a fresh catalog snapshot that takes into
account concurrent commits).

Greetings,

Andres Freund



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