From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
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To: | Gokulakannan Somasundaram <gokul007(at)gmail(dot)com> |
Cc: | pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Deadlock possibility in _bt_check_unique? |
Date: | 2010-03-23 10:19:49 |
Message-ID: | 4BA895C5.2080000@enterprisedb.com |
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Lists: | pgsql-hackers |
Gokulakannan Somasundaram wrote:
> Hi,
> With the implementation of deferred unique constraints, we need to go
> back to the index second time to check whether the unique check is valid.
> Say a situation occurs like this
> a) the first session doing the unique check finds out that there is a unique
> check required second time and just makes its entry and comes back
> b) the second session doing the unique check finds out that there is a
> unique check required second time and just makes its entry and comes back
>
> While they do the second check, first session will wait for the session to
> complete and vice versa. Won't this result in a deadlock? Isn't this a
> realistic scenario?
Yes, that can happen. The deadlock detector will kick in and abort one
of the sessions.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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