Thread: 'Session local' variables

I want to write a contrib module that exports a couple of functions
that PLs (that don't natively support this) can use to set/get
session-local variables. I have a couple of questions:

- Can I simply use a global variable for my hash? Am I correct in
thinking that stored procedures and functions will be executed in the
postgres process assigned to the connection that invokes them, and
therefore each will have its own copy of the global variable?

- How can I get a session-scoped MemoryContext to allocate nodes out of?

Thanks,

Nick Johnson

"Nick Johnson" <arachnid@notdot.net> writes:
> I want to write a contrib module that exports a couple of functions
> that PLs (that don't natively support this) can use to set/get
> session-local variables.

Um, why do you need to do anything?  Don't current_setting() and
set_config() cover this?

            regards, tom lane

On 7/2/07, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> "Nick Johnson" <arachnid@notdot.net> writes:
> > I want to write a contrib module that exports a couple of functions
> > that PLs (that don't natively support this) can use to set/get
> > session-local variables.
>
> Um, why do you need to do anything?  Don't current_setting() and
> set_config() cover this?

I thought those were supposed to be reserved for postgres's
configuration options?

-Nick Johnson

"Nick Johnson" <arachnid@notdot.net> writes:
> On 7/2/07, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> "Nick Johnson" <arachnid@notdot.net> writes:
>>> I want to write a contrib module that exports a couple of functions
>>> that PLs (that don't natively support this) can use to set/get
>>> session-local variables.
>>
>> Um, why do you need to do anything?  Don't current_setting() and
>> set_config() cover this?

> I thought those were supposed to be reserved for postgres's
> configuration options?

Oh, you meant arbitrary new variables.  You can (ab)use
custom_variable_classes for that.  I've also seen people do it
with plperl or pltcl, using those languages' inbuilt capacity
for process-lifetime variables.  (Probably plpython can do it
too, but I'm mostly clueless wrt python.)

Anyway, there are multiple ways to do this with just a couple
lines of code, so I don't see a need for a contrib module.

            regards, tom lane