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Re: visibility maps and heap_prune

From: "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>
To: "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: visibility maps and heap_prune
Date: 2008-12-08 12:56:49
Message-ID: 2e78013d0812080456s2158fc9ex30f90250a3eadd5c@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Mon, Dec 8, 2008 at 11:33 AM, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>wrote:

>
>
> On Sat, Dec 6, 2008 at 8:08 PM, Heikki Linnakangas <
> heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>
>>
>> If you see a straightforward way, please submit a patch!
>>
>>
> Will do that.
>
>

Here is a patch which implements this. The PD_ALL_VISIBLE flag is set if all
tuples in the page are visible to all transactions and there are no DEAD
line pointers in the page. The second check is required so that VACUUM takes
up the page. We could slightly distinguish the two cases (one where the page
requires vacuuming only because of DEAD line pointers and the other where
the page-tuples do not require any visibility checks), but I thought its not
worth the complexity.

Thanks,
Pavan

-- 
Pavan Deolasee
EnterpriseDB     http://www.enterprisedb.com

Attachment: visibility_maps_prune.patch
Description: text/x-patch (7.2 KB)

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