Date: Thu, 2 Nov 2017 10:35:07 -0500
From: Nico Williams <nico@cryptonector.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: proposal: schema variables
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On Thu, Nov 02, 2017 at 06:05:54PM +0530, Robert Haas wrote:
> On Thu, Oct 26, 2017 at 12:51 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote:
> > The variables can be modified by SQL command SET (this is taken from
> > standard, and it natural)
> >
> > SET varname = expression;
> 
> Overloading SET to handle both variables and GUCs seems likely to
> create problems, possibly including security problems.  For example,
> maybe a security-definer function could leave behind variables to
> trick the calling code into failing to set GUCs that it intended to
> set.  Or maybe creating a variable at the wrong time will just break
> things randomly.

That's already true of GUCs, since there are no access controls on
set_config()/current_setting().

Presumably "schema variables" would really just be GUC-like and not at
all like lexically scoped variables.  And also subject to access
controls, thus an overall improvement on set_config()/current_setting().

With access controls, GUCs could become schema variables, and settings
from postgresql.conf could move into the database itself (which I think
would be nice).

Nico
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