Re: Freeze avoidance of very large table.

From: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
To: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(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>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Freeze avoidance of very large table.
Date: 2015-11-19 14:44:05
Message-ID: CAD21AoANrFoioh3zFZFFx7sns8BKJV1pzX4zDDw6H-thp=MvsA@mail.gmail.com
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On Thu, Nov 19, 2015 at 5:54 AM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> On Wed, Nov 18, 2015 at 11:18 AM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
>>
>> I get an error when running pg_upgrade from 9.4 to 9.6-this
>>
>> error while copying relation "mediawiki.archive"
>> ("/tmp/data/base/16414/21043_vm" to
>> "/tmp/data_fm/base/16400/21043_vm"): No such file or directory
>
> OK, so the problem seems to be that rewriteVisibilitymap can get
> called with errno already set to a nonzero value.
>
> It never clears it, and then fails at the end despite that no error
> has actually occurred.
>
> Just setting it to 0 at the top of the function seems to be correct
> thing to do. Or does it need to save the old value and restore it?

Thank you for testing!
I think that the former is better, so attached latest patch.

> But now when I want to do the upgrade faster, I run into this:
>
> "This utility cannot upgrade from PostgreSQL version from 9.5 or
> before to 9.6 or later with link mode."
>
> Is this really an acceptable a tradeoff? Surely we can arrange to
> link everything else and rewrite just the _vm, which is a tiny portion
> of the data directory. I don't think that -k promises to link
> everything it possibly can.

I agree.
I've changed the patch so that.
pg_upgarde creates new _vm file and rewrites it even if upgrading to
9.6 with link mode.

Regards,

--
Masahiko Sawada

Attachment Content-Type Size
000_add_frozen_bit_into_visibilitymap_v25.patch application/octet-stream 91.0 KB

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