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Re: memory leaks? using savepoint

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Tatsuhito Kasahara <kasahara(dot)tatsuhito(at)oss(dot)ntt(dot)co(dot)jp>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: memory leaks? using savepoint
Date: 2010-12-22 03:58:30
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Lists: pgsql-bugs
On Tue, Dec 21, 2010 at 9:26 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> On Fri, Dec 17, 2010 at 7:27 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Tatsuhito Kasahara <kasahara(dot)tatsuhito(at)oss(dot)ntt(dot)co(dot)jp> writes:
>>> When I tested simple query as following, backend process used much memory
>>> and not freed until the backend was finished.
>>> # This is reproduced on PostgreSQL8.3 (PostgreSQL8.3.6 - PostgreSQL8.3.12)
>> Hmm ... this test case doesn't appear to produce any significant memory
>> leakage in 8.4 and up.  What is happening in 8.3 is that the
>> CurTransactionContext of each subtransaction becomes nonempty, so it
>> eats 8K or so even though the snapshot gets released shortly later.
>> There are plenty of other ways to cause that to happen, though, so I'm
>> not particularly excited about fixing this one ... especially not in a
>> stable branch that's not getting a lot of developer testing anymore.
>> I'm inclined to leave this alone --- I think the risks of patching only
>> an old branch will outweigh the benefits.
> The proposed patch looks very simple. I don't think that applying that
> patch will cause serious risk.
> Unless the bug is fixed, the users who encountered the memory-leak
> cannot update their postgres to the latest version of 8.3. This would
> cause more serious situation. And, since psqlODBC frequently issues
> SAVEPONT and RELEASE SAVEPOINT, this memory-leak is not rare case,
> I think.

Are you saying that this problem does not exist in 8.3.0 but does
exist in later 8.3.x revs?

Robert Haas
The Enterprise PostgreSQL Company

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