QUERY PLAN                                   
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 Merge Join  (cost=xxx rows=1 width=29)
   Merge Cond: (t_1.c1 = t_2.c1)
   ->  Index Scan using t1_i1 on t1 t_1  (cost=xxx rows=1000 width=15)
   ->  Sort  (cost=xxx rows=100 width=14)
         Sort Key: t_2.c1
         ->  Seq Scan on t2 t_2  (cost=xxx rows=100 width=14)
(6 rows)