Re: How much do the hint bits help?

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Merlin Moncure" <mmoncure(at)gmail(dot)com>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: How much do the hint bits help?
Date: 2010-12-21 23:41:48
Message-ID: 4D10E6DC02000025000388FB@gw.wicourts.gov
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Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:

> *) what's a good way to stress the clog severely? I'd like to pick
> a degenerate case to get a better idea of the way things stand
> without them.

The worst I can think of is a large database with a 90/10 mix of
reads to writes -- all short transactions. Maybe someone else can
do better. In particular, I'm not sure how savepoints might play
into a degenerate case.

Since we're always talking about how to do better with hint bits
during an unlogged bulk load, it would be interesting to benchmark
one of those followed by a `select count(*) from newtable;` with and
without the patch, on a data set too big to fit in RAM.

> *) is there community interest in a full patch that fills in the
> missing details not implemented here?

I'm certainly curious to see real numbers.

-Kevin

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