Re: Why is lock not released?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Why is lock not released?
Date: 2005-08-20 04:23:38
Message-ID: 10661.1124511818@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
>> The "drop" way probably allows slightly more concurrency, but given that
>> people should seldom be taking exclusionary locks on system catalogs,
>> I'm not sure this is really an issue.

> Hmm. The problem at hand (REASSIGN OWNED BY) may involve changing
> ownership of several objects in a single transaction. The order is
> unspecified, because it's following a scan of the pg_shdepend entries --
> so it'd be easy for one REASSIGN OWNED BY transaction to deadlock with
> another one, if they happen to follow different orderings.

Uh, how is it going to deadlock on a lock that is not exclusive?

regards, tom lane

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