Re: pgsql 8.3.3 "Invalid page header" leads to "FATAL: segment too big"

Στις Thursday 22 April 2010 16:53:05 ο/η Cédric Villemain έγραψε:
> 2010/4/22 Achilleas Mantzios <achill(at)matrix(dot)gatewaynet(dot)com>:
> > Hello,
> > i have this serious problem in one of our remote vessels. (comm is done by minicom to the remote satelite modem)
> > I think that this server was under some sort of constant resets or hardware failures.
> > Initially,i had this problem:
> > ERROR:  invalid page header in block 672720 of relation "pg_toast_125716009"
> >
> > This toast table corresponds to a table named "mail_message",
> >                                Table "public.mail_message"
> >  Column   |       Type        |                         Modifiers
> > -----------+-------------------+-----------------------------------------------------------
> >  msgno     | mail_msgno_domain | not null default nextval('mail_msgno_sequence'::regclass)
> >  msgsource | bytea             |
> > Indexes:
> >    "mail_message_key" PRIMARY KEY, btree (msgno)
> >
> > (obviously the TOAST table serves the msgsource varlena) the contents of which is not of vital importance.
> > I tried, REINDEXING, with no success, and after that, i tried resetting the said block on disk as per this
> > suggestion by Tom here: http://old.nabble.com/invalid-page-header-td11981154.html
> >
> > i found the oid of the table:
> > SELECT tableoid,1 from pg_toast.pg_toast_125716009 order by chunk_id LIMIT 1
> >  tableoid  | ?column?
> > -----------+----------
> >  125716013 |        1
> >
> > (and just to verify)
> > SELECT relname from pg_class where oid=125716013;
> >      relname
> > --------------------
> >  pg_toast_125716009
> >
> > Then i did: (as i said i do not need the contents of msgsource - yet the contents of msgno are vital)
> > dd if=/dev/zero of=/usr/local/var/lib/pgsql/data/base/125714957/125716013 seek=672720 bs=8192 count=1
>
> segment have 1.1GB size maximum. You have to catch in what segment the
> faulty block is, and reajust the block value from the error report to
> the real one in the good segment.
>

Thanx,
Taking a look at /usr/local/src/postgresql-8.3.3/src/backend/storage/smgr/md.c
i see the the error comes from function mdnblocks

if (nblocks > ((BlockNumber) RELSEG_SIZE))
elog(FATAL, "segment too big");

That means, that some segment file is bigger than RELSEG_SIZE
At least in my system:
#define BLCKSZ 8192
#define RELSEG_SIZE (0x40000000 / BLCKSZ)
So, any segment file cannot be bigger than RELSEG_SIZE blocks (or 2^30 bytes = 1GB)

Currently i dont have any access to the machine but tomorrow i will check the file sizes.

Can anyone shed some light as to some method of identifying all the segment files of a table?
The first one has the same name as the tableoid.
How about the subsequent segments?

> >
> > However, after that, unfortunately i get constant postgresql server restarts with:
> > FATAL:  segment too big
> > server closed the connection unexpectedly
> >        This probably means the server terminated abnormally
> >        before or while processing the request.
> > The connection to the server was lost. Attempting reset: Succeeded.
> >
> > Is there anything i can do to savage the situation?
> >
> > (one of) the hard part here is that i dont have neither physical nor network access to the server
> > (only ultra expensive unreliable satellite comms)
> >
> > Thanks for any hints...
> >
> > --
> > Achilleas Mantzios
> >
> > --
> > Sent via pgsql-admin mailing list (pgsql-admin(at)postgresql(dot)org)
> > To make changes to your subscription:
> > http://www.postgresql.org/mailpref/pgsql-admin
> >
>
>
>

--
Achilleas Mantzios