| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
| Cc: | pgsql-hackers(at)postgreSQL(dot)org |
| Subject: | Re: Interesting glitch in autovacuum |
| Date: | 2008-09-10 17:34:11 |
| Message-ID: | 2052.1221068051@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Tom Lane wrote:
>> I observed a curious bug in autovac just now. ...
> Maybe we should boot RecentGlobalXmin with InvalidOid, and ensure where
> it's going to be used that it's not that.
Good idea --- an Assert at the use sites should be sufficient.
>> Lastly, now that we have the PROC_IN_VACUUM test in GetSnapshotData,
>> is it actually necessary for lazy vacuum to avoid setting a snapshot?
>> It seems like it might be a good idea for it to do so in order to
>> keep its RecentGlobalXmin reasonably current.
> Hmm, I think I'd rather be inclined to get a snapshot just when it's
> going to finish.
I'm worried about keeping RecentGlobalXmin up to date during the
vacuums, not only at the end, because it will be used for HOT page
pruning during the vacuums.
regards, tom lane
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