| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Hannu Krosing <hannu(at)skype(dot)net> |
| Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Missing CONCURRENT VACUUM (Was: Release notes for |
| Date: | 2005-08-17 20:45:36 |
| Message-ID: | 7825.1124311536@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Hannu Krosing <hannu(at)skype(dot)net> writes:
> On K, 2005-08-17 at 14:48 -0400, Tom Lane wrote:
>> While testing this I realized that it does not in fact work as
>> advertised. It will only exclude long-running VACUUMs from other
>> VACUUMs' OldestXmin if *all* the transactions in the system are lazy
>> VACUUMs. If there is even one regular transaction in the system,
>> that transaction will include the VACUUMs in its MyProc->xmin, and
>> thence GetOldestXmin will have to include them in its result.
> Only if these regular transactions are running in SERIALIZABLE isolation
> level, else MyProc->xmin is not set inside GetSnapshotData.
Better read the code again. The first snap in *any* transaction sets
MyProc->xmin.
regards, tom lane
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