| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Shared row locking |
| Date: | 2004-12-19 20:54:54 |
| Message-ID: | 16460.1103489694@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> writes:
> On Sun, Dec 19, 2004 at 09:52:01AM +0000, Simon Riggs wrote:
>> - use a lock mode called Cursor Stability that locks only those rows
>> currently being examined by a cursor, those maintaining the lock usage
>> of a cursor at a constant level as the cursor moves. The lock mode of
>> Repeatable Read *does* lock all rows read
> We can't release the locks until the end of the transaction.
Well, what Simon is essentially proposing is that we work around a
potential performance issue by exposing a less-clean semantic model
to users. I'd prefer to adopt such a thing as a last resort, not a
first one.
regards, tom lane
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