Re: "could not read block 0... " error followed by "database does not exist"

Hi. What I see when I do ls on the current (corrupt)
$PGDATA/global is

...
- rw------- 1 jsjacobs deepsky 0 Feb 8 18:51 1262
...
-rw------- 1 jsjacobs deepsky 602 Feb 12 17:42 pg_auth
-rw------- 1 jsjacobs deepsky 8192 Feb 12 17:42 pg_control
-rw------- 1 jsjacobs deepsky 0 Feb 12 17:42 pg_database
-rw------- 1 jsjacobs deepsky 10927 Feb 12 21:57 pgstat.stat

I have a pgdump from a month ago. Are you saying to restore
that to a different location and then copy over
$PGDATA/global/1262? Do I also need to copy over
$PGDATA/global/pg_database?

Thanks,
Janet

Tom Lane wrote:
> Janet S Jacobsen <JSJacobsen(at)lbl(dot)gov> writes:
>> Hi. I am running Postgres 8.2.7 on a Linux system for over
>> a year now with no problems.
>
>> Today one of the database users reported the following error:
>
>> psql: FATAL: could not read block 0 of relation 1664/0/1262: read
>> only 0 of 8192 bytes
>
> Ugh. 1262 is pg_database --- apparently something has truncated your
> pg_database table to zero bytes :-(. Which certainly explains the
> "no such database" errors.
>
> Have you got any chance of pulling that physical file from a backup?
> The one bright spot here is that pg_database is pretty static in most
> installations, so you could probably use even a not-very-current copy.
> The file you want is $PGDATA/global/1262.
>
> I don't offhand know of any bugs in 8.2.7 that could cause this,
> though that is rather an old version ... you might want to think
> about an update to 8.2.something-recent.
>
> regards, tom lane