Re: Physical append-only tables

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Magnus Hagander <magnus(at)hagander(dot)net>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Physical append-only tables
Date: 2016-11-14 01:35:51
Message-ID: 20161114013551.tjj5yz5okggsm4p2@alvherre.pgsql
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Magnus Hagander wrote:

> But then consider the same table. Except rows are typically updated once or
> twice when they are new, and *then* go read only. And we also have a
> process that at some point deletes *some* old rows (but not all - in fact,
> only a small portion).
> In this case, the next INSERT once VACUUM has run is likely to stick a
> "new" row somewhere very "far back" in the table, since there is now free
> space there. This more or less completely ruins the BRIN index usability,
> as the "old" blocks will now contain a single row from a "new" series.

Yeah. When we initially discussed BRIN, there was a mention of allowing
a BRIN index to guide new tuple location -- something like
auto-clustering, if you will. We haven't discussed the exact details
but I think something along those lines is worth considering.

Álvaro Herrera
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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