Re: Cause of missing pg_clog files

Tom Lane wrote:
> Yesterday I reported a WAL problem that could lead to tuples not being
> marked as committed-good or committed-dead after we'd already removed
> the pg_clog segment that had their transaction's commit status.
> I wasn't completely satisfied with that, though, because on further
> reflection it seemed a very low-probability mechanism. I kept digging,
> and finally came to the kind of bug that qualifies as a big DOH :-(
>
> If you run a database-wide VACUUM (one with no specific target table
> mentioned) as a non-superuser, then the VACUUM doesn't process tables
> that don't belong to you. But it will advance pg_database.datvacuumxid
> anyway, which means that pg_clog could be truncated while old transaction
> references still remain unmarked in those other tables.
>
> In words of one syllable: running VACUUM as a non-superuser can cause
> irrecoverable data loss in any 7.2.* release.
>
> I think this qualifies as a "must fix" bug. I recommend we back-patch
> a fix for this into the REL7_2 branch and put out a 7.2.3 release.
> We should also fix the "can't wait without a PROC" bug that was solved
> a few days ago.

Wow, you sure have found some good bugs in the past few days. Nice job.

Yes, I agree we should push out a 7.2.3, and I think we are now ready
for beta3. I will work on docs and packaging now.

--
Bruce Momjian | http://candle.pha.pa.us
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