Re: pgbench throttling latency limit

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Rukh Meski <rukh(dot)meski(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>, gregsmithpgsql(at)gmail(dot)com, jan(at)wi3ck(dot)info
Subject: Re: pgbench throttling latency limit
Date: 2014-10-09 19:39:59
Message-ID: alpine.DEB.2.10.1410092128190.27407@sto
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> One thing bothers me with the log format. Here's an example:
>
>> 0 81 4621 0 1412881037 912698 3005
>> 0 82 6173 0 1412881037 914578 4304
>> 0 83 skipped 0 1412881037 914578 5217
>> 0 83 skipped 0 1412881037 914578 5099
>> 0 83 4722 0 1412881037 916203 3108
>> 0 84 4142 0 1412881037 918023 2333
>> 0 85 2465 0 1412881037 919759 740
>
> Note how the transaction counter is not incremented for skipped transactions.
> That's understandable, since we're not including skipped transactions in the
> number of transactions executed, but it means that the skipped transactions
> don't have a unique ID. That's annoying.

Indeed. As transactions were not done, it does not make much sense to
identify them. Otherwise it should report "intended" transactions and
"performed" transactions, which would not help clarify the matter much.

My idea of "skipped" transactions, which are not transactions as such, is
just a health quality measurement for both the throttling process and the
database latency, so I would really let it as it is.

> Here's a new version of the patch. I'll sleep over it before committing, but
> I think it's fine now, except maybe for the unique ID thing.

I saw a typo in a comment: "lateny" -> "latency". Otherwise it looks ok,
and the documentation seems indeed clearer than before.

--
Fabien.

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