Re: PG_DUMP error : unexpected chunk number

On 10/28/2011 06:24 PM, mailtolouis2020-postgres(at)yahoo(dot)com wrote:
> Hello,
>
> I think I got a big problem now, I'm not able to do pg_dump on one of my
> production database. When I do pg_dump it give me this error:
> pg_dump: Error message from server: ERROR: unexpected chunk number
> 18390760 (expected 4) for toast value 92784 in pg_toast_88487
>
> I believe this message mean that my database is corrupted.

Yup, pretty much. Check your hard drives. It's not impossible that
there's a PostgreSQL bug that's caused the issue, but it's more likely
going to be a hard drive, RAID array, or system memory/cpu/heat issue.

For recovery: First, stop postgresql and take a file-level copy of your
whole database. Keep that copy somewhere safe, in case your repair
efforts make the issue worse.

In this case, I'd probably try zeroing damaged pages as my first
recovery effort. That's a bit of a big hammer, but might let you get a
dump out. It WILL DESTROY DATA, so I'd recommend doing it by copying
your backup to another directory and running a temporary postgresql
instance with zero_damaged_pages enabled on it, then trying to dump from
the temporary postmaster you've started. That way you don't have to mess
with your original running database.

See:
http://www.postgresql.org/docs/current/static/runtime-config-developer.html

It might help to look up which "real" table the pg_toast_88487 TOAST
table is associated with, and see how important it is. Use pg_catalog
for that; see the documentation.

--
Craig Ringer