From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: Bruce Momjian <bruce@momjian.us>, Tatsuo Ishii <ishii@postgresql.org>,
	pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] pg_dump and thousands of schemas
In-reply-to: 
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References: <20120529.185149.1127748531209576379.t-ishii@sraoss.co.jp>
	<12147.1338306742@sss.pgh.pa.us>
	<20120530.180620.600165924826262795.t-ishii@sraoss.co.jp>
	<20120531.092043.1953698679173443322.t-ishii@sraoss.co.jp>
	<20120830204433.GW8753@momjian.us> <1086.1346359916@sss.pgh.pa.us>
	<CA+TgmobHksoQmbLyAMB7D5FwqDGA8+u5rooviEuP8rg_zcMzGg@mail.gmail.com>
Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Thu, 30 Aug 2012 17:45:24 -0400"
Date: Thu, 30 Aug 2012 23:17:55 -0400
Message-ID: <27683.1346383075@sss.pgh.pa.us>

Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, Aug 30, 2012 at 4:51 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Bruce Momjian <bruce@momjian.us> writes:
>>> On Thu, May 31, 2012 at 09:20:43AM +0900, Tatsuo Ishii wrote:
>>>> Ok, I modified the part of pg_dump where tremendous number of LOCK
>>>> TABLE are issued. I replace them with single LOCK TABLE with multiple
>>>> tables. With 100k tables LOCK statements took 13 minutes in total, now
>>>> it only takes 3 seconds. Comments?

>>> Was this applied?

>> No, we fixed the server side instead.

> But only for 9.2, right?  So people running back branches are still screwed.

Yeah, but they're screwed anyway, because there are a bunch of O(N^2)
behaviors involved here, not all of which are masked by what Tatsuo-san
suggested.

Six months or a year from now, we might have enough confidence in that
batch of 9.2 fixes to back-port them en masse.  Don't want to do it
today though.

			regards, tom lane