Re: Is my database now too big?

Darren Reed wrote:
> Scott Marlowe wrote:
>> On 10/7/07, Darren Reed <darrenr+postgres(at)fastmail(dot)net> wrote:
>> > Scott Marlowe wrote:
>> > > On 10/7/07, Darren Reed <darrenr(at)fastmail(dot)net> wrote:
>> > > > Scott Marlowe wrote:
>>
>> > A few days ago I did:
>> > pg_dumpall > foo
>> > What I was doing yesterday was:
>> > rm -rf /data/db/*
>> > initdb -D /data/db
>> > start
>> > psql < foo
>> > run for some period
>> > stop
>> > reboot
>> > start
>> > ...tables have gone but disk space is still in use.
>> > I dont know if it was during the period of running that the
>> > database got corrupted (interrupted insert/update/query?)
>> > or what happened.
>>
>> Are you sure postgresql was starting up in the /data/db directory
>> after reboot and not somewhere else like /var/lib/pgsql/data???
>>
>> IF you're definitely hitting the right directory, then Is the database
>> shutting down cleanly on reboot? It might be that it's getting killed
>> during a write and you've got some kind of problem with fsync on your
>> machine so the db is getting corrupted
>>
>> > > Can you be more specific on what exact query causes the problem
>> to show up?
>> > >
>> >
>> > It turned out that _any_ query on that table caused the problem to
>> show up.
>> >
>> > I couldn't even do "DROP TABLE ifl;" without postgres growing until it
>> > ran out of memory.
>>
>> definitely sounds like some kind of issue other just the size of the
>> table, like some kind of corruption.
>>
>> ...
>> And I don't see anything else in your postgresql.conf that looks
>> suspicious. I'm leaning towards possible pilot error in shutting down
>> or starting up the db.
>>
>
> Ok, I've had another reoccurance of this problem.
>
> The sequence of events was something like this:
> CREATE TABLESPACE foo LOCATION "/data/index/ext";
> <wait>
> <machine hangs>
> <reboot>
> Of course postgresql didn't shut down cleanly because it was
> naughtly earlier and ate all my RAM, causing the box to hang.
> Now I'm back to the prior problem: entire tables are missing
> when postgresql starts back up again. Obviously there is some
> sort of corruption (caused by postgresql) and it isn't able to
> recover properly.

I suppose the obvious question here is how do I restore the
missing tables? The data is all there, is there some sort of
transaction log that can be unwound to restore visibility of
the missing tables? Where do I start for trying to do some
forensics? Or am I SOL?

Later on...

So having upgraded to 8.1.10, I thought I'd try out a few things...

# /usr/pkg/bin/pg_dumpall
--
-- PostgreSQL database cluster dump
--

\connect postgres

--
-- Roles
--

CREATE ROLE postgres;
ALTER ROLE postgres WITH SUPERUSER INHERIT CREATEROLE CREATEDB LOGIN;
CREATE ROLE root;
ALTER ROLE root WITH SUPERUSER INHERIT CREATEROLE CREATEDB LOGIN;

--
-- Database creation
--

REVOKE ALL ON DATABASE template1 FROM PUBLIC;
REVOKE ALL ON DATABASE template1 FROM postgres;
GRANT ALL ON DATABASE template1 TO postgres;

\connect postgres

pg_dump: SQL command failed
pg_dump: Error message from server: ERROR: out of memory
DETAIL: Failed on request of size 20.
pg_dump: The command was: LOCK TABLE public.foo IN ACCESS SHARE MODE
pg_dumpall: pg_dump failed on database "postgres", exiting
# SELECT * FROM foo LIMIT 1;
ERROR: out of memory
DETAIL: Failed on request of size 20.

I don't know if this is of any significance:
# \l
List of databases
Name | Owner | Encoding
-----------+----------+-----------
postgres | postgres | SQL_ASCII
template0 | postgres | SQL_ASCII
template1 | postgres | SQL_ASCII
(3 rows)

# /usr/pkg/bin/psql -U postgres template1
psql: FATAL: out of memory
DETAIL: Failed on request of size 20.

What puzzles me is why the transaction log hasn't
resulted in postgresql being able to restore itself
to a known clean state.

Darren