查看是否为分布key join

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postgres=# explain  select tbase_1.* from tbase_1,tbase_2 where tbase_1.f1=tbase_2.f1 ;           
                                           QUERY PLAN                                           
------------------------------------------------------------------------------------------------
 Remote Subquery Scan on all (dn001,dn002)  (cost=29.80..186.32 rows=3872 width=40)
   ->  Hash Join  (cost=29.80..186.32 rows=3872 width=40)
         Hash Cond: (tbase_1.f1 = tbase_2.f1)
         ->  Remote Subquery Scan on all (dn001,dn002)  (cost=100.00..158.40 rows=880 width=40)
               Distribute results by S: f1
               ->  Seq Scan on tbase_1  (cost=0.00..18.80 rows=880 width=40)
         ->  Hash  (cost=18.80..18.80 rows=880 width=4)
               ->  Seq Scan on tbase_2  (cost=0.00..18.80 rows=880 width=4)
(8 rows)
postgres=# explain  select tbase_1.* from tbase_1,tbase_2 where tbase_1.f2=tbase_2.f1 ;   
                                   QUERY PLAN                                    
---------------------------------------------------------------------------------
 Remote Fast Query Execution  (cost=0.00..0.00 rows=0 width=0)
   Node/s: dn001, dn002
   ->  Hash Join  (cost=18904.69..46257.08 rows=500564 width=14)
         Hash Cond: (tbase_1.f2 = tbase_2.f1)
         ->  Seq Scan on tbase_1  (cost=0.00..9225.64 rows=500564 width=14)
         ->  Hash  (cost=9225.64..9225.64 rows=500564 width=4)
               ->  Seq Scan on tbase_2  (cost=0.00..9225.64 rows=500564 width=4)
(7 rows)