From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | sailesh(at)cs(dot)berkeley(dot)edu, Jenny - <nat_lazy(at)hotmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: this is in plain text (row level locks) |
Date: | 2003-07-24 02:03:51 |
Message-ID: | 14295.1059012231@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> Sailesh Krishnamurthy wrote:
>> Does pgsql only record X locks on the individual tuples on-disk or
>> does it do so for S locks as well ?
> We don't need to shared lock individual rows because of MVCC --- well,
> we sort of do by recording our xid in our proc structure, so folks don't
> change things underneath us. We prevent expired rows from disappearing
> from the disk by others looking at our proc start xid.
This is actually an issue though. Row-level shared locks would be
really nice to have for foreign-key handling. Right now we have to
use X locks for those, and that leads to deadlocking problems for
applications.
regards, tom lane
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