| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Kris Kiger <kris(at)musicrebellion(dot)com>, pgsql-admin(at)postgresql(dot)org |
| Subject: | Re: Concurrency |
| Date: | 2005-05-09 19:18:40 |
| Message-ID: | 515.1115666320@sss.pgh.pa.us |
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| Lists: | pgsql-admin |
Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> On Mon, 2005-05-09 at 12:21 -0500, Kris Kiger wrote:
>> Quick question. I lock a table, call it table X, and then issue two
>> updates on that table. The two updates are left waiting. I then unlock
>> the table. The two updates go through. My question is, is there a
>> predictable way to determine which query will be executed first?
> The lock queue is served in FIFO sequence.
... usually. We will promote later arrivals in front of older ones if
the alternative would be a deadlock (eg, the later one already holds
some lock that would block the earlier one).
regards, tom lane
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