查看并行的worker数

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postgres=# explain select count(1) from tbase_1;
                                      QUERY PLAN                                       
---------------------------------------------------------------------------------------
 Finalize Aggregate  (cost=118.81..118.83 rows=1 width=8)
   ->  Remote Subquery Scan on all (dn001,dn002)  (cost=118.80..118.81 rows=1 width=0)
         ->  Partial Aggregate  (cost=18.80..18.81 rows=1 width=8)
               ->  Seq Scan on tbase_1  (cost=0.00..18.80 rows=880 width=0)
(4 rows)
postgres=# analyze tbase_1;
ANALYZE
postgres=# explain select count(1) from tbase_1;
                                             QUERY PLAN                                             
----------------------------------------------------------------------------------------------------
 Parallel Finalize Aggregate  (cost=14728.45..14728.46 rows=1 width=8)
   ->  Parallel Remote Subquery Scan on all (dn001,dn002)  (cost=14728.33..14728.45 rows=1 width=0)
         ->  Gather  (cost=14628.33..14628.44 rows=1 width=8)
               Workers Planned: 2
               ->  Partial Aggregate  (cost=13628.33..13628.34 rows=1 width=8)
                     ->  Parallel Seq Scan on tbase_1  (cost=0.00..12586.67 rows=416667 width=0)
(6 rows)