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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Georgios Kokolatos <gkokolatos@pm.me>
Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Subject: Re: CPU costs of random_zipfian in pgbench
Date: Mon, 01 Apr 2019 17:39:05 -0400
Message-ID: <19055.1554154745@sss.pgh.pa.us> (raw)
In-Reply-To: <alpine.DEB.2.21.1903242006310.9939@lancre>
References: <b5e172e9-ad22-48a3-86a3-589afa20e8f7@2ndquadrant.com>
	<alpine.DEB.2.21.1902221716430.4182@lancre>
	<155246731010.16480.15850913449923768119.pgcf@coridan.postgresql.org>
	<alpine.DEB.2.21.1903131048290.4059@lancre>
	<3703.1553360483@sss.pgh.pa.us>
	<alpine.DEB.2.21.1903231802440.18811@lancre>
	<010a884f-8ffc-4cb7-9773-fd05f32ef4cc@2ndquadrant.com>
	<alpine.DEB.2.21.1903241513570.9939@lancre>
	<alpine.DEB.2.21.1903241823070.9939@lancre>
	<29040.1553452066@sss.pgh.pa.us>
	<alpine.DEB.2.21.1903242006310.9939@lancre>

Fabien COELHO <coelho@cri.ensmp.fr> writes:
>> I was wondering about that too.  It seems like it'd be a wise idea to
>> further constrain s and/or n to ensure that the s > 1 code path doesn't do
>> anything too awful ...

> Yep. The attached version enforces s >= 1.001, which avoids the worse cost
> of iterating, according to my small tests.

Seems reasonable.  Pushed with minor documentation editing.

			regards, tom lane





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