From: Marina Polyakova <m.polyakova@postgrespro.ru>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org, Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Kevin Grittner <kgrittn@gmail.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>
Subject: Re: WIP Patch: Pgbench Serialization and deadlock errors
Date: Fri, 16 Jun 2017 13:26:28 +0300
Message-ID: <d979e8d9a3bb31fff69c31745b95ae78@postgrespro.ru> (raw)
In-Reply-To: <20170615191636.mqzk7ongddmhoqzm@alap3.anarazel.de>
References: <72a0d590d6ba06f242d75c2e641820ec@postgrespro.ru>
<20170615191636.mqzk7ongddmhoqzm@alap3.anarazel.de>
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> Hi,
Hello!
> I think that's a good idea and sorely needed.
Thanks, I'm very glad to hear it!
>> - if there were these failures during script execution this
>> "transaction" is
>> marked
>> appropriately in logs;
>> - numbers of "transactions" with these failures are printed in
>> progress, in
>> aggregation logs and in the end with other results (all and for each
>> script);
>
> I guess that'll include a "rolled-back %' or 'retried %' somewhere?
Not exactly, see documentation:
+ If transaction has serialization / deadlock failure or them both
(last thing
+ is possible if used script contains several transactions; see
+ <xref linkend="transactions-and-scripts"
+ endterm="transactions-and-scripts-title"> for more information), its
+ <replaceable>time</> will be reported as <literal>serialization
failure</> /
+ <literal>deadlock failure</> /
+ <literal>serialization and deadlock failures</> appropriately.
+ Example with serialization, deadlock and both these failures:
+<screen>
+1 128 24968 0 1496759158 426984
+0 129 serialization failure 0 1496759158 427023
+3 129 serialization failure 0 1496759158 432662
+2 128 serialization failure 0 1496759158 432765
+0 130 deadlock failure 0 1496759159 460070
+1 129 serialization failure 0 1496759160 485188
+2 129 serialization and deadlock failures 0 1496759160 485339
+4 130 serialization failure 0 1496759160 485465
+</screen>
I have understood proposals in next messages of this thread that the
most interesting case is to retry failed transaction. Do you think it's
better to write for example "rolled-back after % retries (serialization
failure)' or "time (retried % times, serialization and deadlock
failures)'?
>> Advanced options:
>> - mostly for testing built-in scripts: you can set the default
>> transaction
>> isolation level by the appropriate benchmarking option (-I);
>
> I'm less convinced of the need of htat, you can already set arbitrary
> connection options with
> PGOPTIONS='-c default_transaction_isolation=serializable' pgbench
Oh, thanks, I forgot about it =[
>> P.S. Does this use case (do not retry transaction with serialization
>> or
>> deadlock failure) is most interesting or failed transactions should be
>> retried (and how much times if there seems to be no hope of
>> success...)?
> I can't quite parse that sentence, could you restate?
Álvaro Herrera later in this thread has understood my text right:
> As far as I understand her proposal, it is exactly the opposite -- if a
> transaction fails, it is discarded. And this P.S. note is asking
> whether this is a good idea, or would we prefer that failing
> transactions are retried.
With his explanation has my text become clearer?
--
Marina Polyakova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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To: pgsql-hackers@postgresql.org
Cc: m.polyakova@postgrespro.ru, andres@anarazel.de, alvherre@2ndquadrant.com, kgrittn@gmail.com, thomas.munro@enterprisedb.com
Subject: Re: WIP Patch: Pgbench Serialization and deadlock errors
In-Reply-To: <d979e8d9a3bb31fff69c31745b95ae78@postgrespro.ru>
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