Date: Sat, 17 Nov 2018 08:06:54 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: Michael Paquier <michael@paquier.xyz>,
	Stephen Frost <sfrost@snowman.net>,
	Andrew Dunstan <andrew.dunstan@2ndquadrant.com>,
	PostgreSQL Developers <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] pgbench - allow to store select results into variables
Message-ID: <20181117110654.ekd2duiss4lwph6y@alvherre.pgsql>
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On 2018-Nov-17, Fabien COELHO wrote:

> 
> > I think this patch's Command->lines would benefit from using PQExpBuffer
> > (or maybe StringInfo?) for the command string instead of open-coding
> > string manipulation and allocation.
> 
> Indeed it could be used, but it is not used anywhere in "pgbench": not for
> lines, not for variable subtitutions, not for the PREPARE stuff... So I did
> not think that it was time to start, I just kept the current style.
> 
> Probably it could be a refactoring patch to replace all basic string stuff
> with PQExpBuffer infrastructure within pgbench.

Well, I think command handling was mostly straightforward before, but
it's not as straightforward after your patch.  Also, PQExpBuffer is
already in use in pgbench when interacting with the lexer, so yeah I
think we should fix that.  I don't think we should replace *ALL* string
handling in pgbench with PQExpBuffer, just the command stuff.


> > I'm not sure that Command->first_line is really all that useful.  It
> > seems we go to a lot of trouble to keep it up to date.  Isn't it easier
> > to chop Command->lines at the first newline when it is needed?
> 
> Hmmm, it is needed quite often (about 12 times) to report errors, that would
> mean having to handle the truncation in many places, so I felt it was worth
> the trouble.

Ok, as long as we don't repeat the work during script execution.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services