pg_clog and pg_xlog empty, postgresql refuses to start

[Glen Parker]

First things first: Postgresql 8.4.2 on Fedora Core 2 X86.

Something seems to have happened to my pg_xlog and pg_clog directories after
(I believe) a power outage. In the course of trying to figure out why the
server wouldn't start, I cleaned out pg_clog and pg_xlog, in an obviously
vain attempt to reset things. I was under the impression that the server
could start without those files. Now I seem to be stuck.

So now what?

Here is what postmaster has to say on the subject:

LOG: database system was shut down at 2004-08-16 15:52:01 PDT
LOG: could not open file
"/usr/local/var/lib/pgsql32-broken/pg_xlog/0000000F000000F3" (log file 15,
segment 243): No such file or directory
LOG: invalid primary checkpoint record
LOG: could not open file
"/usr/local/var/lib/pgsql32-broken/pg_xlog/0000000F000000F3" (log file 15,
segment 243): No such file or directory
LOG: invalid secondary checkpoint record
PANIC: could not locate a valid checkpoint record
LOG: startup process (PID 9920) was terminated by signal 6
LOG: aborting startup due to startup process failure

Thx
Glen Parker
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[Tom Lane]

"Glen Parker" <gl******@nwlink.com> writes:

First things first: Postgresql 8.4.2 on Fedora Core 2 X86.
I take it this message fell through a time warp ;-)
Something seems to have happened to my pg_xlog and pg_clog directories after
(I believe) a power outage. In the course of trying to figure out why the
server wouldn't start, I cleaned out pg_clog and pg_xlog, in an obviously
vain attempt to reset things. I was under the impression that the server
could start without those files. Now I seem to be stuck.

That was probably not your best first move...

I'd put back the clog files if at all possible. If not you can
substitute zero-filled 256K files for each clog file the server
complains about not finding, but realize that you *will* be losing
transactions in whole or in part.

As for pg_xlog, you can cons up dummy xlog contents with pg_resetxlog,
but again you'd be better off with the real thing. The dummy files will
not be capable of replaying whatever happened since your last checkpoint.

What failures were you getting *before* you decided to try this?

regards, tom lane

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[Glen Parker]

> > First things first: Postgresql 8.4.2 on Fedora Core 2 X86.

I take it this message fell through a time warp ;-)
Yep :-)
7.4.2.

...I cleaned out pg_clog and pg_xlog...

That was probably not your best first move...

This is actually a development copy of our real database, so worst-case
scenario is a dump/restore. No big deal.
I'd put back the clog files if at all possible. If not you can
substitute zero-filled 256K files for each clog file the server
complains about not finding, but realize that you *will* be losing
transactions in whole or in part.

As for pg_xlog, you can cons up dummy xlog contents with pg_resetxlog,
but again you'd be better off with the real thing. The dummy files will
not be capable of replaying whatever happened since your last checkpoint.
OK, all the files I deleted, I really deleted... See? I'm on a roll today.

pg_resetxlog did the trick, mostly; the server starts again and I seem to be
back to where I started...
What failures were you getting *before* you decided to try this?

I started out, and am now once again, getting this error when issuing a
delete query in psql:

ERROR: could not access status of transaction 655360
DETAIL: could not read from file "/usr/local/var/lib/pgsql32/pg_clog/0000"
at offset 163840: Success

I am now also getting this error when vacuuming a different table:
ERROR: catalog is missing 2 attribute(s) for relid 25297932
Hmm, whatever happened over the weekend that caused this machine to be *off*
this morning must have been a bit nasty... Dump/restore may be my only
option.

Thx again,
Glen Parker
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[Tom Lane]

"Glen Parker" <gl******@nwlink.com> writes:

I am now also getting this error when vacuuming a different table:
ERROR: catalog is missing 2 attribute(s) for relid 25297932

Yeah, this is what I warned you about: partial committal of transactions.
Given that it's only a devel server, it's probably best to initdb ...

regards, tom lane

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