Re: Deleting older versions in unique indexes to avoid page splits

From: Andres Freund <andres(at)anarazel(dot)de>
To: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: Peter Geoghegan <pg(at)bowt(dot)ie>, Victor Yegorov <vyegorov(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Deleting older versions in unique indexes to avoid page splits
Date: 2021-01-20 05:20:21
Message-ID: 20210120052021.l5ygiuw66nk2htet@alap3.anarazel.de
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Hi,

On 2021-01-20 09:24:35 +0530, Amit Kapila wrote:
> I feel extending the deletion mechanism based on the number of LP_DEAD
> items sounds more favorable than giving preference to duplicate
> items. Sure, it will give equally good or better results if there are
> no long-standing open transactions.

There's a lot of workloads that never set LP_DEAD because all scans are
bitmap index scans. And there's no obvious way to address that. So I
don't think it's wise to purely rely on LP_DEAD.

Greetings,

Andres Freund

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