| From: | Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Philip Molter <philip(at)datafoundry(dot)net>, Alex Pilosov <alex(at)pilosoft(dot)com>, Alex Knight <knight(at)phunc(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Weird error |
| Date: | 2001-06-28 10:08:59 |
| Message-ID: | 3B3B023B.22B349C0@tpf.co.jp |
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| Thread: | |
| Lists: | pgsql-general |
Tom Lane wrote:
>
> Philip Molter <philip(at)datafoundry(dot)net> writes:
> > I am using 7.1.2.
>
> Drat.
>
> Don't suppose you want to dig in there with a debugger when it happens?
> You must be seeing some hard-to-replicate problem in VACUUM's
> tuple-chain-moving logic.
I had a pretty reproducible example 2 years ago.
IIRC the situation was like
When vacuum starts xid=10001 and 10004 are alive.
If vacuum finds an update chain (10002 -> 10000 -> 10003),
it removes the tuple (10000) because no xids <= 10000 is
alive. Then the chain is broken.
The problem seems to lie in scan_heap.
How could vacuum know that the tuple (10000) must be alive
after vacuum ?
regards,
Hiroshi Inoue
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