making multiple updates use indexes: howto?

Hi.

I have a doubt:

If I make:

update stockline set status=3 where id IN (select id from lap_mpdetail_view where lap=3976)

postgres makes an Seq Scan on stockline.

when stockline is big, it is better to make an select id from
lap_mpdetail_view where lap=3976) and programaticaly build the query of the
type update stockline set status=3 where id=X or id=Y or...

There must be a better way... EXISTS also make a seq scan

update stockline set status=3 where id = (select id from
lap_mpdetail_view where lap=3976); returns more than one tuple

Thanks

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Pedro Miguel G. Alves pmalves(at)think(dot)pt
THINK - Tecnologias de Informação www.think.pt
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