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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Claudio Freire <klaussfreire@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Robert Klemme <shortcutter@googlemail.com>
Cc: Tatsuo Ishii <ishii@postgresql.org>
Cc: pgsql-performance@postgresql.org
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] pg_dump and thousands of schemas
Date: Thu, 31 May 2012 11:25:37 -0400
Message-ID: <13349.1338477937@sss.pgh.pa.us> (raw)
In-Reply-To: <CAGTBQpYdNN_Q3Ksvr7tN_6aXqp_gc0KOsbrWLW_QZE=c22QjUg@mail.gmail.com>
References: <20120529.185149.1127748531209576379.t-ishii@sraoss.co.jp>
	<20120531.174526.2183902405630094684.t-ishii@sraoss.co.jp>
	<CAM9pMnM9vLd8HiNCqeskMwij4MAEjSb76pKDRnnh=uRpL4U17A@mail.gmail.com>
	<20120531.230757.2014494683420217075.t-ishii@sraoss.co.jp>
	<CAM9pMnPQb9PUxWAx_VGVCb41ta08rW2AA_G6XXnp+2FcuB1BXQ@mail.gmail.com>
	<CAGTBQpaW5O7vUKMrWGn+xUJR-Ni-FEQB_DUZMB_Gt_a-uMp8WA@mail.gmail.com>
	<9787.1338474676@sss.pgh.pa.us>
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	<10443.1338475851@sss.pgh.pa.us>
	<CAGTBQpYdNN_Q3Ksvr7tN_6aXqp_gc0KOsbrWLW_QZE=c22QjUg@mail.gmail.com>

Claudio Freire <klaussfreire@gmail.com> writes:
> On Thu, May 31, 2012 at 11:50 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> The performance patches we applied to pg_dump over the past couple weeks
>> were meant to relieve pain in situations where the big server-side
>> lossage wasn't the dominant factor in runtime (ie, partial dumps).
>> But this one is targeting exactly that area, which is why it looks like
>> a band-aid and not a fix to me.

> No, Tatsuo's patch attacks a phase dominated by latency in some
> setups.

No, it does not.  The reason it's a win is that it avoids the O(N^2)
behavior in the server.  Whether the bandwidth savings is worth worrying
about cannot be proven one way or the other as long as that elephant
is in the room.

			regards, tom lane



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