Very slow queries

Check this:

query: Delete From ceroriesgo.salarios Where numero_patrono Not In (Select 
numero_patrono From ceroriesgo.patronos)

Seq Scan on salarios  (cost=51021.78..298803854359.95 rows=14240077 width=6)
  Filter: (NOT (subplan))
  SubPlan
    ->  Materialize  (cost=51021.78..69422.58 rows=1032980 width=25)
          ->  Seq Scan on patronos  (cost=0.00..41917.80 rows=1032980 
width=25)


These query took a day to finish, how or who can improove better performance 
of my PostgreSQL.

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