From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Claudio Freire <klaussfreire@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 10:50:51 -0400
Message-ID: <10443.1338475851@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+Tgmoa3OjFGfkru-XkbxKyysCWLHX-s4y1yVZYwYSdGp0Pc3A@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>
<CA+Tgmoa3OjFGfkru-XkbxKyysCWLHX-s4y1yVZYwYSdGp0Pc3A@mail.gmail.com>
Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, May 31, 2012 at 10:31 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I'm not; Jeff Janes is. But you shouldn't be holding your breath
>> anyway, since it's 9.3 material at this point.
> I agree we can't back-patch that change, but then I think we ought to
> consider back-patching some variant of Tatsuo's patch. Maybe it's not
> reasonable to thunk an arbitrary number of relation names in there on
> one line, but how about 1000 relations per LOCK statement or so? I
> guess we'd need to see how much that erodes the benefit, but we've
> certainly done back-branch rearrangements in pg_dump in the past to
> fix various kinds of issues, and this is pretty non-invasive.
I am not convinced either that this patch will still be useful after
Jeff's fix goes in, or that it provides any meaningful savings when
you consider a complete pg_dump run. Yeah, it will make the lock
acquisition phase faster, but that's not a big part of the runtime
except in very limited scenarios (--schema-only, perhaps).
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.
regards, tom lane
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Cc: tgl@sss.pgh.pa.us, robertmhaas@gmail.com, klaussfreire@gmail.com, shortcutter@googlemail.com, ishii@postgresql.org, pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] pg_dump and thousands of schemas
In-Reply-To: <10443.1338475851@sss.pgh.pa.us>
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