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Re: [HACKERS] pg_dump and thousands of schemas

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>,Claudio Freire <klaussfreire(at)gmail(dot)com>,Robert Klemme <shortcutter(at)googlemail(dot)com>,Tatsuo Ishii <ishii(at)postgresql(dot)org>,pgsql-performance(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] pg_dump and thousands of schemas
Date: 2012-05-31 15:00:54
Message-ID: 20120531150054.GF26894@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
On Thu, May 31, 2012 at 10:50:51AM -0400, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > On Thu, May 31, 2012 at 10:31 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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).

FYI, that is the pg_upgrade use-case, and pg_dump/restore time is
reportedly taking the majority of time in many cases.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +

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