Re: How much do the hint bits help?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Merlin Moncure <mmoncure(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: How much do the hint bits help?
Date: 2010-12-22 00:45:17
Message-ID: 9107.1292978717@sss.pgh.pa.us
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Merlin Moncure <mmoncure(at)gmail(dot)com> writes:
> Attached is an incomplete patch disabling hint bits based on compile
> switch. ...
> So far, at least doing pgbench runs and another test designed to
> exercise clog lookups, the performance loss of always doing full
> lookup hasn't materialized.

The standard pgbench test would be just about 100% useless for stressing
this, because its net database activity is only about one row
touched/updated per query. You need a test case that hits lots of rows
per query, else you're just measuring parse+plan+network overhead.

regards, tom lane

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