I'm a newbie in postgresql, I've installed it on a Windows XP machine
( I can't use linux, it's a company machine ), I'm courious why this
query takes so long

SELECT "Rut Cliente"
FROM "Internet_Abril"
WHERE "Rut Cliente"  NOT IN ((SELECT "Rut Cliente"  FROM
"Internet_Enero") UNION (SELECT "Rut Cliente"  FROM
"Internet_Febrero") UNION (SELECT "Rut Cliente"  FROM

it takes about 100 minutes to complete the query.
All tables has index created ( Rut Cliente is a VarChar ), and tables
has 50.000 records each.

The explain for the query tells the following

 Seq Scan on "Internet_Abril"  (cost=19406.67..62126112.70 rows=24731 width=13)
  Filter: (NOT (subplan))
       ->  Materialize  (cost=19406.67..21576.07 rows=136740 width=13)
        ->  Unique  (cost=17784.23..18467.93 rows=136740 width=13)
        ->  Sort  (cost=17784.23..18126.08 rows=136740 width=13)
Key: "Rut Cliente"
          ->  Append  (cost=0.00..3741.80 rows=136740 width=13)
          ->  Subquery Scan "*SELECT* 1"  (cost=0.00..1233.38
rows=45069 width=13)
           ->  Seq Scan on "Internet_Enero"  (cost=0.00..782.69
rows=45069 width=13)
           ->  Subquery Scan "*SELECT* 2"  (cost=0.00..1104.06
rows=40353 width=13)
             ->  Seq Scan on "Internet_Febrero"  (cost=0.00..700.53
rows=40353 width=13)
           ->  Subquery Scan "*SELECT* 3"  (cost=0.00..1404.36
rows=51318 width=13)
            ->  Seq Scan on "Internet_Marzo"  (cost=0.00..891.18
rows=51318 width=13)

Any help will be apreciated, It's for my thesis


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