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Re: Suggestion to add --continue-client-on-abort option to pgbench

Yugo Nagata <nagata@sraoss.co.jp>

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From: Yugo Nagata <nagata@sraoss.co.jp>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: 'Rintaro Ikeda' <ikedarintarof@oss.nttdata.com>, "slpmcf@gmail.com" <slpmcf@gmail.com>, "boekewurm+postgres@gmail.com" <boekewurm+postgres@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>
Date: 2025-06-26T09:47:33Z
Lists: pgsql-hackers 
On Thu, 26 Jun 2025 05:45:12 +0000
"Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com> wrote:

> Dear Nagata-san,
> 
> > As I understand it, the current patch aims to allow continuation only after
> > SQL-level
> > errors, such as constraint violations. That seems reasonable, as it can simulate
> > the
> > behavior of applications that ignore or retry such errors (even though retries are
> > not
> > implemented in the current patch).
> 
> Yes, no one has objections to retry in this case. This is a main part of the proposal., 

As I understand it, the proposed --continue-on-error option does not retry the transaction
in any case; it simply gives up on the transaction. That is, when an SQL-level error occurs,
the transaction is reported as "failed" rather than "retried", and the random state is discarded.

> 
> > However, I'm not sure it's reasonable to allow continuation after other types of
> > errors,
> > such as misuse of meta-commands or unexpected errors during their execution,
> > since these
> > wouldn't simulate any real application behavior and would more likely indicate a
> > failure
> > in the benchmarking process itself.
> 
> I have a concern for \gset metacommand.
> According to the doc and source code, \gset assumed that executed command surely
> returns a tuple:
> 
> ```
> 					if (meta == META_GSET && ntuples != 1)
> 					{
> 						/* under \gset, report the error */
> 						pg_log_error("client %d script %d command %d query %d: expected one row, got %d",
> 									 st->id, st->use_file, st->command, qrynum, PQntuples(res));
> 						st->estatus = ESTATUS_META_COMMAND_ERROR;
> 						goto error;
> 					}
> ```
> 
> But sometimes the SQL may not be able to return tuples or return multiple ones due
> to the concurrent transactions. I feel retrying the transaction is very useful
> in this case.

You can use \aset command instead to avoid the error of pgbench. If the query doesn't
return any row, a subsecuent SQL command trying to use the varialbe will fail, but this
would be ignored without terminating the benchmark when the --coneinue-on-error option
enabled.

> Anyway, we must confirm the opinion from the proposer.

+1

Best regards,
Yugo Nagata

-- 
Yugo Nagata <nagata@sraoss.co.jp>

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. pgbench: Fix assertion failure with multiple \syncpipeline in pipeline mode.

  2. pgbench: Add --continue-on-error option.

  3. Fix "inconsistent DLL linkage" warning on Windows MSVC

  4. pgbench: Fix error reporting in readCommandResponse().

  5. pgbench: Fix assertion failure with retriable errors in pipeline mode.

  6. Allow pgbench to retry in some cases.