From:
Robert Haas <robertmhaas(at)gmail(dot)com>
To:
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc:
Bruce Momjian <bruce(at)momjian(dot)us>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject:
Re: crash-safe visibility map, take three
Date:
2010-12-01 17:23:50
Message-ID:
AANLkTi=d=8oJzvLbUmuoDdViSG9O+1uamC3Gj3OUs+r6@mail.gmail.com (view raw or flat )
Thread:
2010-11-30 04:57:25 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 07:34:04 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 15:32:15 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 15:43:47 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 15:54:50 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 16:40:10 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 16:48:08 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 16:54:43 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 16:59:20 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 17:01:56 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 15:38:02 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 15:46:44 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 15:53:25 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 16:02:05 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 16:16:33 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 16:22:03 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 16:27:04 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 16:33:18 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 16:47:40 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 16:49:34 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 16:55:44 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 17:00:29 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 17:10:49 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 17:12:35 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 17:22:02 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 17:25:18 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 17:36:07 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 17:25:41 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 17:26:08 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-11-30 16:59:47 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-01 01:35:56 from Bruce Momjian <bruce(at)momjian(dot)us>
2010-12-01 07:35:40 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-12-01 13:39:07 from Bruce Momjian <bruce(at)momjian(dot)us>
2010-12-01 13:53:12 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-12-01 14:57:51 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2010-12-01 15:46:21 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-01 15:36:51 from Bruce Momjian <bruce(at)momjian(dot)us>
2010-12-01 16:25:36 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-01 16:40:39 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-12-01 16:43:39 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-12-01 17:23:50 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-01 16:40:46 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-12-01 16:44:12 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-12-01 16:48:03 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-12-01 17:22:41 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-12-01 17:31:36 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-01 20:31:27 from Jeff Davis <pgsql(at)j-davis(dot)com>
2010-12-01 20:59:49 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-01 21:27:28 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-12-01 22:24:22 from Jeff Davis <pgsql(at)j-davis(dot)com>
2010-12-02 04:22:12 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-02 11:37:57 from Dimitri Fontaine <dimitri(at)2ndQuadrant(dot)fr>
2010-12-02 14:37:37 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-02 19:01:43 from Jeff Davis <pgsql(at)j-davis(dot)com>
2010-12-02 19:16:09 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2010-12-02 22:00:18 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-02 23:37:05 from Jeff Davis <pgsql(at)j-davis(dot)com>
2010-12-03 00:06:29 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-03 00:40:44 from Jeff Davis <pgsql(at)j-davis(dot)com>
2010-12-01 23:41:33 from Jim Nasby <jim(at)nasby(dot)net>
2010-12-02 04:36:42 from Robert Haas <robertmhaas(at)gmail(dot)com>
2010-12-03 14:25:20 from Florian Weimer <fweimer(at)bfk(dot)de>
2010-11-30 16:27:30 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 16:10:13 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 16:30:53 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2010-11-30 16:37:13 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2010-11-30 13:18:12 from Rob Wultsch <wultsch(at)gmail(dot)com>
2011-01-05 20:22:54 from Jesper Krogh <jesper(at)krogh(dot)cc>
2011-01-06 02:10:15 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-01-06 07:00:29 from Jesper Krogh <jesper(at)krogh(dot)cc>
2011-01-07 18:28:54 from Jim Nasby <jim(at)nasby(dot)net>
2011-01-08 02:59:36 from Robert Haas <robertmhaas(at)gmail(dot)com>
Lists:
pgsql-hackers
On Wed, Dec 1, 2010 at 11:40 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> On 01.12.2010 18:25, Robert Haas wrote:
>>
>> I think we can improve this a bit further by also introducing a
>> HEAP_XMIN_FROZEN bit that we set in lieu of overwriting XMIN with
>> FrozenXID. This allows us to freeze tuples aggressively - if we want
>> - without losing any forensic information. We can then modify the
>> above algorithm slightly, so that when we observe that a page is all
>> visible, we not only set PD_ALL_VISIBLE on the page but also
>> HEAP_XMIN_FROZEN on each tuple.
>
> Hmm, actually, if we're willing to believe PD_ALL_VISIBLE in the page header
> over the xmin/xmax on the tuples, we could simply not bother doing
> anti-wraparound vacuums for pages that have the flag set. I'm not sure what
> changes that would require outside heapam.c, as we'd have to be careful to
> not trust the xmin/xmax if the flag was set.
>
> The first update on the page that clears the flag would need to freeze all
> the tuples in that scheme.
That seems more complex for no particular gain. I guess it saves an
infomask bit, but I'm willing to burn one to reduce code complexity.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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