Re: crash / data recovery issues - Mailing list pgsql-hackers

From Alvaro Herrera
Subject Re: crash / data recovery issues
Date
Msg-id 20080206185641.GB19269@alvh.no-ip.org
Whole thread Raw
In response to crash / data recovery issues  (Robert Treat <xzilla@users.sourceforge.net>)
Responses Re: crash / data recovery issues  (Robert Treat <xzilla@users.sourceforge.net>)
List pgsql-hackers
Robert Treat wrote:
> I'm trying to do some data recovery on an 8.1.9 system.  The brief history is 
> the system crashed, attempted to do xlog replay but that failed.   I did a 
> pg_resetxlog to get something that would startup, and it looks as if the 
> indexes on pg_class have become corrupt. (ie. reindex claimes duplicate rows, 
> which do not show up when doing count() manipulations on the data).  As it 
> turns out, I can't drop these indexes either (system refuses with message 
> indexes are needed by the system).  This has kind of let the system in an 
> unworkable state.  

You can work out of it by starting a standalone server with system
indexes disabled (postgres -O -P, I think) and do a REINDEX on it (the
form of it that reindexes all system indexes -- I think it's REINDEX
DATABASE).

> I also did some digging to find the original error on xlog replay and it 
> was  "failed to re-find parent key in "763769" for split pages 21032/21033". 
> I'm wondering if this is actually something you can push past with 
> pg_resetxlog, or if I need to do a pg_resetxlog and pass in values prior to 
> that error point (i guess essentially letting pg_resetxlog do a lookup)... 
> thoughts? 

You should be able to get out of that by reindexing that index.
(Actually, after you do a pg_resetxlog I think the best is to pg_dump
the whole thing and reload it.  That gives you at least the assurance
that your FKs are not b0rked)

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support


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