Re: pgbench MAX_ARGS - Mailing list pgsql-hackers

From Simon Riggs
Subject Re: pgbench MAX_ARGS
Date
Msg-id CANP8+jJkquQHR+DJ6=s_UHqFxmjV+2FwTZH-Uk3zz_NRZp5Rsw@mail.gmail.com
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In response to Re: pgbench MAX_ARGS  (Fabien COELHO <coelho@cri.ensmp.fr>)
Responses Re: pgbench MAX_ARGS  (ilmari@ilmari.org (Dagfinn Ilmari Mannsåker))
Re: pgbench MAX_ARGS  (Andres Freund <andres@anarazel.de>)
Re: pgbench MAX_ARGS  (David Rowley <david.rowley@2ndquadrant.com>)
List pgsql-hackers
On Tue, 26 Feb 2019 at 12:19, Fabien COELHO <coelho@cri.ensmp.fr> wrote:

Hello Simon,

Thanks for reviewing Fabien,
 
> pgbench has a strange restriction to only allow 10 arguments, which is too
> low for some real world uses.
>
> Since MAX_ARGS is only used for an array of pointers and an array of
> integers increasing this should not be a problem, so increase value to 255.
 
Probably I would have chosen a smaller value, eg 32 or 64, but I have not
seen your use case.

I've put it as 256 args now.

The overhead of that is about 2kB, so not really an issue.

People are using pgbench for real testing, so no need for setting it too low.

I notice that there is no documentation update, which just shows that
indeed there are no documentation about the number of arguments, maybe the
patch could add a sentence somewhere? There is no limit discussed in the
PREPARE documentation, I tested up to 20. I'd sugggest to add something at
the end of the paragraph about variable substitution in the "Custom
Script" section, eg "A maximum of XX variable references can appear within
an SQL command.".

Added as you suggest. 

--
Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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