Re: WIP Patch: Pgbench Serialization and deadlock errors

From: Andres Freund <andres(at)anarazel(dot)de>
To: Marina Polyakova <m(dot)polyakova(at)postgrespro(dot)ru>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: WIP Patch: Pgbench Serialization and deadlock errors
Date: 2017-06-15 19:16:36
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On 2017-06-14 11:48:25 +0300, Marina Polyakova wrote:
> Now in pgbench we can test only transactions with Read Committed isolation
> level because client sessions are disconnected forever on serialization
> failures. There were some proposals and discussions about it (see message
> here [1] and thread here [2]).

> I suggest a patch where pgbench client sessions are not disconnected because
> of serialization or deadlock failures and these failures are mentioned in
> reports.

I think that's a good idea and sorely needed.

In details:

> - 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?

> 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

> 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?

- Andres

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