Re: BRIN cost estimate

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Emre Hasegeli <emre(at)hasegeli(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: BRIN cost estimate
Date: 2017-04-06 21:47:48
Message-ID: 20170406214748.3jhqwipgkbmj5pl4@alvherre.pgsql
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Tom Lane wrote:

> TBH, I think that code is in the noise. It doesn't involve any disk
> access, or catalog access, or user-defined function calls. I wouldn't
> bother trying to account for it.

I removed it in the pushed version.

> What you should be accounting for is the ensuing heap page accesses,
> but I assume that's done somewhere else.

It's supposed to be accounted for, yeah.

One thing we do not account for is the number of extra heap accesses we
do for unsummarized ranges (mostly, heap has grown but the index doesn't
cover the new pages yet).

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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