Re: pgbench regression test failure

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: PostgreSQL Developers <pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: pgbench regression test failure
Date: 2017-09-12 17:13:22
Message-ID: 4233.1505236402@sss.pgh.pa.us
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Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> writes:
>> Apparently, one of the threads ran 3 transactions where the test script
>> expects it to run at most 2. Is this a pgbench bug, or is the test
>> being overoptimistic about how exact the "-T 2" cutoff is?

> Probably both? It seems that cutting off on time is not a precise science,
> so I suggest to accept 1, 2 and 3 lines, see attached.

Before I'd deciphered the test output fully, I was actually guessing that
the problem was the opposite, namely too few lines. Isn't it possible
that some thread is slow enough to start up that it doesn't get to run
any transactions? IOW, do we need to allow 0 to 3 lines?

regards, tom lane

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