From: Alessandro Baretta <a.baretta@barettadeit.com>
To: Craig A. James <cjames@modgraph-usa.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Suspending SELECTs
Date: Tue, 17 Jan 2006 21:06:53 +0100
Message-ID: <43CD4E5D.7060406@barettadeit.com> (raw)
In-Reply-To: <43CC0DDF.9080904@modgraph-usa.com>
References: <43CB71AC.20203@barettadeit.com>
<9766.1137433907@sss.pgh.pa.us>
<43CC0DDF.9080904@modgraph-usa.com>
Craig A. James wrote:
>
> Alessandro Baretta <a.baretta@barettadeit.com> writes:
>
> I think you're trying to do something at the wrong layer of your
> architecture. This task normally goes in your middleware layer, not
> your database layer.
I am developing my applications in Objective Caml, and I have written the
middleware layer myself. I could easily implement a cursor-pooling strategy, but
there is no perfect solution to the problem of guaranteeing that cursors be
closed. Remember that web applications require the user to "open a session" by
connecting the appropriate HTTP resource, but users as never required to log
out. Hence, in order to eventually reclaim all cursors, I must use magical
"log-out detection" algorithm, which is usually implemented with a simple
timeout. This guarantees the required property of safety (the population of
cursors does not diverge) but does not guarantee the required property of
liveness (a user connecting to the application, who has opened a session but has
not logged out, and thus possesses a session token, should have access the
execution context identified by his token).
Alex
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To: pgsql-performance@postgresql.org
Cc: a.baretta@barettadeit.com, cjames@modgraph-usa.com
Subject: Re: Suspending SELECTs
In-Reply-To: <43CD4E5D.7060406@barettadeit.com>
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