Re: Schema variables - new implementation for Postgres 15

Hi,

On Fri, Nov 04, 2022 at 03:07:48PM +0100, Dmitry Dolgov wrote:
> > On Fri, Nov 04, 2022 at 05:58:06AM +0100, Pavel Stehule wrote:
> > Hi
> >
> > fix clang warning
>
> I've stumbled upon something that looks weird to me (inspired by the
> example from tests):
>
> =# create variable v2 as int;
> =# let v2 = 3;
> =# create view vv2 as select coalesce(v2, 0) + 1000 as result
>
> =# select * from vv2;
> result
> --------
> 1003
>
> =# set force_parallel_mode to on;
> =# select * from vv2;
> result
> --------
> 1000
>
> In the second select the actual work is done from a worker backend.
> Since values of session variables are stored in the backend local
> memory, it's not being shared with the worker and the value is not found
> in the hash map. Does this suppose to be like that?

There's code to serialize and restore all used variables for parallel workers
(see code about PARAM_VARIABLE and queryDesc->num_session_variables /
queryDesc->plannedstmt->sessionVariables). I haven't reviewed that part yet,
but it's supposed to be working. Blind guess would be that it's missing
something in expression walker.