Should the function get_variable_numdistinct consider the case when stanullfrac is 1.0?

# create table t(a int, b int);

CREATE TABLE

# insert into t select i from generate_series(1, 10000)i;

INSERT 0 10000

gpadmin=# analyze t;

ANALYZE

# explain analyze select b, count(1) from t group by b;

                                                QUERY PLAN

-----------------------------------------------------------------------------------------------------------

 HashAggregate  (cost=195.00..197.00 rows=200 width=12) (actual time=5.928..5.930 rows=1 loops=1)

   Group Key: b

   Batches: 1  Memory Usage: 40kB

   ->  Seq Scan on t  (cost=0.00..145.00 rows=10000 width=4) (actual time=0.018..1.747 rows=10000 loops=1)

 Planning Time: 0.237 ms

 Execution Time: 5.983 ms

(6 rows)