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Re: [pgsql-cluster-hackers] Question: Can i cut NON-HOT chain Pointers if there are no concurrent updates?

From: Markus Wanner <markus(at)bluegap(dot)ch>
To: "" <HMaelzer(at)buerotiger(dot)de>
Cc: PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [pgsql-cluster-hackers] Question: Can i cut NON-HOT chain Pointers if there are no concurrent updates?
Date: 2012-11-23 15:08:51
Message-ID: 50AF9183.3010308@bluegap.ch (view raw or flat)
Thread:
Lists: pgsql-cluster-hackerspgsql-hackers
Henning,

On 11/23/2012 03:17 PM, "Henning Mälzer" wrote:
> Can somebody help me?

Sure, but you might get better answers on the -hackers mailing list. I'm
redirecting there. The cluster-hackers one is pretty low volume and low
subscribers, I think.

> Question:
> What would be the loss if i cut NON-HOT chain Pointers, meaning i set t_ctid=t_self in the case where it points to a tuple on another page?

READ COMMITTED would stop to work correctly in the face of concurrent
transactions, I guess. See the fine manual:

http://www.postgresql.org/docs/devel/static/transaction-iso.html#XACT-READ-COMMITTED

The problem essentially boils down to: READ COMMITTED transactions need
to learn about tuples *newer* than what their snapshot would see.

> I am working on a project based on "postgres (PostgreSQL) 8.5devel" with the code from several master thesises befor me.

Care to elaborate a bit? Can (part of) that code be released under an
open license?

Regards

Markus Wanner


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