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Re: Debugging deadlocks

From: Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl>
To: Guy Rouillier <guyr(at)masergy(dot)com>
Cc: PostgreSQL General <pgsql-general(at)postgresql(dot)org>,Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Debugging deadlocks
Date: 2005-04-01 01:31:14
Message-ID: 20050401013113.GA27341@dcc.uchile.cl (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
On Thu, Mar 31, 2005 at 06:54:31PM -0600, Guy Rouillier wrote:
> Alvaro Herrera wrote:
> > 
> > Now this can't be applied right away because it's easy to run "out of
> > memory" (shared memory for the lock table).  Say, a delete or update
> > that touches 10000 tuples does not work.  I'm currently working on a
> > proposal to allow the lock table to spill to disk ...   
> 
> While not always true, in many cases the cardinality of the referenced
> (parent) table is small compared to that of the referencing (child)
> table.  Does locking require a separate lock record for each tuple in
> the child table, or just one for each tuple in the parent table with a
> reference count?

Just one.  (LOCALLOCK, which is private to each backend, stores how many
times we hold a lock.)

I just realized we not only need to be able to spill LOCK struct to
disk, but also PROCLOCK ... am I right?

-- 
Alvaro Herrera (<alvherre[(at)]dcc(dot)uchile(dot)cl>)
La web junta la gente porque no importa que clase de mutante sexual seas,
tienes millones de posibles parejas. Pon "buscar gente que tengan sexo con
ciervos incendiándose", y el computador dirá "especifique el tipo de ciervo"
(Jason Alexander)

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