Re: Summary and Plan for Hot Standby

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Summary and Plan for Hot Standby
Date: 2009-11-15 17:36:52
Message-ID: 4B003C34.4080604@enterprisedb.com
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Simon Riggs wrote:
> On Sun, 2009-11-15 at 16:07 +0200, Heikki Linnakangas wrote:
>
>> The assumption that b-tree vacuum records don't need conflict
>> resolution because we did that with the additional cleanup-info record
>> works ATM, but it hinges on the fact that we don't delete any tuples
>> marked as killed while we do the vacuum.
>
>> That seems like a low-hanging
>> fruit that I'd actually like to do now that I spotted it, but will
>> then need to fix b-tree vacuum records accordingly. We'd probably need
>> to do something about the previous item first to keep performance
>> acceptable.
>
> We can optimise that by using the xlog pointer of the HeapInfo record.
> Any blocks cleaned that haven't been further updated can avoid
> generating further btree deletion records.

Sorry, I don't understand that. (Remember that marking index tuples as
killed is not WAL-logged.)

> You spotted this issue only this morning??

Yesterday evening.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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