Re: Page at a time index scan

From: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-patches(at)postgresql(dot)org
Subject: Re: Page at a time index scan
Date: 2006-05-03 07:28:24
Message-ID: Pine.OSF.4.61.0605031026060.244444@kosh.hut.fi
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On Tue, 2 May 2006, Tom Lane wrote:

> Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
>> On Tue, 2 May 2006, Tom Lane wrote:
>>> Backwards scan may break this whole concept; are you sure you've thought
>>> it through?
>
>> I think so. The patch doesn't change the walk-left code. Do you have
>> something specific in mind?
>
> I'm worried about synchronization, particularly what happens if the page
> gets deleted from under you while you don't have it pinned.

AFAICS, shouldn't happen. The half-dead system makes sure that a page
won't get deleted while a scan might still be interested in it. It
doesn't depend on pins.

- Heikki

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