|From:||Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com>|
|To:||Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>|
|Cc:||Petr Jelinek <petr(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>|
|Subject:||Re: Freeze avoidance of very large table.|
|Views:||Raw Message | Whole Thread | Download mbox|
On Thu, Apr 30, 2015 at 8:07 PM, Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com> wrote:
> On Fri, Apr 24, 2015 at 11:21 AM, Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com> wrote:
>> On Fri, Apr 24, 2015 at 1:31 AM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
>>> On 4/23/15 11:06 AM, Petr Jelinek wrote:
>>>> On 23/04/15 17:45, Bruce Momjian wrote:
>>>>> On Thu, Apr 23, 2015 at 09:45:38AM -0400, Robert Haas wrote:
>>>>> Agreed, no extra file, and the same write volume as currently. It would
>>>>> also match pg_clog, which uses two bits per transaction --- maybe we can
>>>>> reuse some of that code.
>>>> Yeah, this approach seems promising. We probably can't reuse code from
>>>> clog because the usage pattern is different (key for clog is xid, while
>>>> for visibility/freeze map ctid is used). But visibility map storage
>>>> layer is pretty simple so it should be easy to extend it for this use.
>>> Actually, there may be some bit manipulation functions we could reuse;
>>> things like efficiently counting how many things in a byte are set. Probably
>>> doesn't make sense to fully refactor it, but at least CLOG is a good source
>>> for cut/paste/whack.
>> I agree with adding a bit that indicates corresponding page is
>> all-frozen into VM, just like CLOG.
>> I'll change the patch as second version patch.
> The second patch is attached.
> In second patch, I added a bit that indicates all tuples in page are
> completely frozen into visibility map.
> The visibility map became a bitmap with two bit per heap page:
> all-visible and all-frozen.
> The logics around vacuum, insert/update/delete heap are almost same as
> previous version.
> This patch lack some point: documentation, comment in source code,
> etc, so it's WIP patch yet,
> but I think that it's enough to discuss about this.
The previous patch is no longer applied cleanly to HEAD.
The attached v2 patch is latest version.
Please review it.
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