Re: [HACKERS] proposal: schema variables - Mailing list pgsql-hackers

AFAICS this patch does nothing to consider parallel safety -- that is,
as things stand, a variable is allowed in a query that may be
parallelised, but its value is not copied to workers, leading to
incorrect results. For example:

create table foo(a int);
insert into foo select * from generate_series(1,1000000);
create variable zero int;
let zero = 0;

explain (costs off) select count(*) from foo where a%10 = zero;

                  QUERY PLAN
-----------------------------------------------
 Finalize Aggregate
   ->  Gather
         Workers Planned: 2
         ->  Partial Aggregate
               ->  Parallel Seq Scan on foo
                     Filter: ((a % 10) = zero)
(6 rows)

select count(*) from foo where a%10 = zero;

 count
-------
 38037    -- Different random result each time, should be 100,000
(1 row)

Thoughts?

Regards,
Dean