From: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, Greg S <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Freeze avoidance of very large table. |
Date: | 2016-03-10 18:41:55 |
Message-ID: | CAD21AoAykDHd_95p6J8UXSaxW_qdkBxba2k7grTCJ4K1ZmRkJg@mail.gmail.com |
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Lists: | pgsql-hackers |
On Fri, Mar 11, 2016 at 1:03 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> This 001 patch looks so little like what I was expecting that I
> decided to start over from scratch. The new version I wrote is
> attached here. I don't understand why your version tinkers with the
> logic for setting the all-frozen bit; I thought that what I already
> committed dealt with that already, and in any case, your version
> doesn't even compile against latest sources. Your version also leaves
> the scan_all terminology intact even though it's not accurate any
> more, and I am not very convinced that the updates to the
> page-skipping logic are actually correct. Please have a look over
> this version and see what you think.
Thank you for your advise.
Sorry, optimising logic of previous patch was old by mistake.
Attached latest patch incorporated your suggestions with a little revising.
>
> I think that's kind of pointless. We need to test that this
> conversion code works, but once it does, I don't think we should make
> everybody pay the overhead of retesting that. Anyway, the test code
> could have bugs, too.
>
> Here's an updated version of your patch with that code removed and
> some cosmetic cleanups like fixing typos and stuff like that. I think
> this is mostly ready to commit, but I noticed one problem: your
> conversion code always produces two output pages for each input page
> even if one of them would be empty. In particular, if you have a
> large number of small relations and run pg_upgrade, all of their
> visibility maps will go from 8kB to 16kB. That isn't the end of the
> world, maybe, but I think you should see if you can't fix it
> somehow....
Thank you for updating patch.
To deal with this problem, I've changed it so that pg_upgrade checks
file size before conversion.
And if fork file does not exist or size is 0 (empty), ignore.
Attached latest patch.
Regards,
--
Masahiko Sawada
Attachment | Content-Type | Size |
---|---|---|
001_optimize_vacuum_by_frozen_bit_v40.patch | application/octet-stream | 31.6 KB |
000_pgupgrade_rewrite_vm_v42.patch | application/octet-stream | 9.8 KB |
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