Bad plan on a huge table query

Hi,

I'm trying to figure out why does the planner found 1 row estimate using nested loops over a big table. There is no return from it:

It returns if disable nested loops, but the plan still poor:

I'm using PostgreSQL 9.2.3, default_statistics_target on 1000.

I can't remember what to make PostgreSQL sees a better estimate in the scan of aula_confirmacao and the join with presenca. I got rusty after a long time just doing modeling.

Does someone has some idea on that?

Thanks,