Re: [HACKERS] pgbench randomness initialization

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Chapman Flack <chap(at)anastigmatix(dot)net>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] pgbench randomness initialization
Date: 2018-03-01 06:56:57
Message-ID: alpine.DEB.2.20.1803010750440.7903@lancre
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Hello Tom,

> Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> writes:
>>> This is a simple patch that does what it says on the tin. I ran into
>>> trouble with the pgbench TAP test *even before applying the patch*, but
>>> only because I was doing a VPATH build as a user without 'write'
>>> on the source tree (001_pgbench_with_server.pl tried to make pgbench
>>> create log files there). Bad me. Oddly, that was the only test in the
>>> whole tree to have such an issue, so here I add a pre-patch to fix that.
>>> Now my review needs a review. :)
>
>> Yep. I find the multiple chdir solution a little bit too extreme.
>
>> ISTM that it should rather add the correct path to --log-prefix by
>> prepending $node->basedir, like the pgbench function does for -f scripts.
>> See attached.
>
> Hm ... so I tried to replicate this problem, and failed to: the log files
> get made under the VPATH build directory, as desired, even without this
> patch. Am I doing something wrong, or is this platform-dependent somehow?

As I recall, it indeed works if the source directories are rw, but fails
if they are ro because then the local mkdir fails. So you would have to do
a vpath build with sources that are ro to get the issue the patch is
fixing. Otherwise, the issue would have been cought earlier by the
buildfarm, which I guess is doing vpath compilation and full validation.

--
Fabien.

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