From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@commandprompt.com>
Cc: ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp>
Cc: pgsql-hackers@postgresql.org, Katsuhiko Okano <okano.katsuhiko@oss.ntt.co.jp>
Subject: Re: CSStorm occurred again by postgreSQL8.2
Date: Mon, 07 Aug 2006 15:42:31 -0400
Message-ID: <13175.1154979751@sss.pgh.pa.us> (raw)
In-Reply-To: <20060807185243.GB26021@alvh.no-ip.org>
References: <200607181650.EDC81237.LOBJUTPuIPPBLLV@oss.ntt.co.jp>
<5126.1153241513@sss.pgh.pa.us>
<20060807114525.5266.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
<19738.1154956177@sss.pgh.pa.us>
<20060807185243.GB26021@alvh.no-ip.org>
Alvaro Herrera <alvherre@commandprompt.com> writes:
> Tom Lane wrote:
>> I'm wondering about doing something similar to what
>> TransactionIdIsInProgress does, ie, make use of the PGPROC lists
>> of live subtransactions.
> Well, that sounds awfully more expensive than setting
> local-to-my-database Xmins as well as global (all databases) Xmins :-)
Only when you've got a lot of subtransactions. The point of this
discussion is to optimize for the few-or-none case. In any case,
the problem with the local/global bit was that you'd be expending
foreground-process cycles without any foreground-process return.
Being able to use a snapshot without consulting pg_subtrans will
certainly buy back some cycles...
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, alvherre@commandprompt.com, itagaki.takahiro@oss.ntt.co.jp, okano.katsuhiko@oss.ntt.co.jp
Subject: Re: CSStorm occurred again by postgreSQL8.2
In-Reply-To: <13175.1154979751@sss.pgh.pa.us>
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