BEGIN;
SET max_parallel_workers_per_gather=4;
SET force_parallel_mode=on;
CREATE TABLE parallel_test(i int, b1 base36, b2 bigbase36) WITH (parallel_workers = 4);
INSERT INTO parallel_test (i, b1, b2)
SELECT i, i::int, i::bigint
FROM generate_series(1,1e6) i;
EXPLAIN (costs off,verbose)
SELECT COUNT(*) FROM parallel_test WHERE b1 = '1ftese';
                            QUERY PLAN                             
-------------------------------------------------------------------
 Finalize Aggregate
   Output: count(*)
   ->  Gather
         Output: (PARTIAL count(*))
         Workers Planned: 4
         ->  Partial Aggregate
               Output: PARTIAL count(*)
               ->  Parallel Seq Scan on public.parallel_test
                     Output: i, b1, b2
                     Filter: (parallel_test.b1 = '1ftese'::base36)
(10 rows)

EXPLAIN (costs off,verbose)
SELECT COUNT(*) FROM parallel_test WHERE b2 = '1ftese';
                              QUERY PLAN                              
----------------------------------------------------------------------
 Finalize Aggregate
   Output: count(*)
   ->  Gather
         Output: (PARTIAL count(*))
         Workers Planned: 4
         ->  Partial Aggregate
               Output: PARTIAL count(*)
               ->  Parallel Seq Scan on public.parallel_test
                     Output: i, b1, b2
                     Filter: (parallel_test.b2 = '1ftese'::bigbase36)
(10 rows)

EXPLAIN (costs off,verbose)
SELECT b1, COUNT(*) FROM parallel_test GROUP BY 1;
                            QUERY PLAN                             
-------------------------------------------------------------------
 Finalize GroupAggregate
   Output: b1, count(*)
   Group Key: parallel_test.b1
   ->  Gather Merge
         Output: b1, (PARTIAL count(*))
         Workers Planned: 4
         ->  Sort
               Output: b1, (PARTIAL count(*))
               Sort Key: parallel_test.b1
               ->  Partial HashAggregate
                     Output: b1, PARTIAL count(*)
                     Group Key: parallel_test.b1
                     ->  Parallel Seq Scan on public.parallel_test
                           Output: i, b1, b2
(14 rows)

ROLLBACK;