Re: pgbench stats per script & other stuff

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pgbench stats per script & other stuff
Date: 2016-03-04 18:41:57
Message-ID: 20160304184157.GA726930@alvherre.pgsql
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Fabien COELHO wrote:

> >However, this is still a bit broken -- you cannot return a stack
> >variable from process_file, because the stack goes away once the
> >function returns. You need to malloc it.
> That is why the "fs" variable in process_file is declared "static", and why
> I wrote "some hidden awkwarness".
> I did want to avoid a malloc because then who would free the struct?
> addScript cannot to it systematically because builtins are static. Or it
> would have to create an on purpose struct, but I then that would be more
> awkwarness, and malloc/free to pass arguments between functions is not
> efficient nor very elegant.
> So the "static" option looked like the simplest & most elegant version.

Surely that trick breaks if you have more than one -f switch, no? Oh, I
see what you're doing: you only use the command list, which is
allocated, so it doesn't matter that the rest of the struct changes
later. That seems rather nasty to me -- I'd avoid that.

I'm not concerned about freeing the struct; what's the problem with it
surviving until the program terminates? If somebody specifies thousands
of -f switches, they will waste a few bytes with each, but I'm hardly
concerned about a few dozen kilobytes there ...

Álvaro Herrera
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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