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.
The syntax CREATE OR REPLACE FUNCTION xxx $$ ... $$ SET GUC=, ... is always related only to GUC. So there should not be any security risk.
It is another reason why GUC and variables should be separated.
I know so there is risk of possibility of collision. There are two possibilities
a) use different keyword - but it is out of SQL/PSM and out of another databases.
b) detect possible collision and raise error when assignment is ambiguous. I am thinking about similar solution used in plpgsql, where is a possibility of collision between SQL identifier and plpgsql variable.