Re: question about wal and point in time recovery

Tom,

Is your (?) tool publically available?

<awkward pause>

Maybe I could have phrased that better....<sigh>

In any case, do you have a pointer to this R&R WAL tool?

Thanks,

Ross

-----Original Message-----
From: pgsql-admin-owner(at)postgresql(dot)org [mailto:pgsql-admin-owner(at)postgresql(dot)org] On Behalf Of Tom Lane
Sent: Wednesday, April 13, 2005 12:29 AM
To: Alex Zendel
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: [ADMIN] question about wal and point in time recovery

"Alex Zendel" <alexzendel(at)hotmail(dot)com> writes:
> ... i've been reading up on the wal and point in time recovery in
> the online postgre manual. but i have a question about using it:

[ obligatory gripe: it's postgres or postgresql, not postgre ]

> is it possible to visually read the entries in the log?

Not readily. If you find yourself backed into a corner, I have a rough-and-ready debug tool for printing out the contents of a WAL log, but I'd surely not want to call it "supported" in its current form...

> can the log be modified before recovery occurs.

Not easily. If you were to hack any one log entry, you'd have to recompute the CRC checksum for it, and there's no way at all to make a change that would involve changing the size of a log entry. So really the only useful option you have here is to stop recovery short of a particular log entry you don't like.

> my biggest concern is that somebody in my org, for example, deletes a
> field or fudges an update query that changes a foreign key to a single
> value - and therefore destroys table links. so what if this happens
> and nobody notices it for several weeks?

There is no automatic recovery mechanism that is going to help you in such a scenario. You can't expect to undo a long-ago change and not have that break some unknown number of consequent decisions.

regards, tom lane

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