Re: Query returning tuples that does not satisfy the WHERE clause

Manuel Sugawara <masm@fciencias.unam.mx> writes:
> Using the second plan the query is returning tuples where
>    a=F1o_semestre <> 20071

You seem to have worse problems than that, because as given the
insc_registra_grupo function never returns non-NULL, and so the
query ought not be returning any tuples at all.  I suspect pilot
error --- perhaps looking at the wrong schema or some such?
        regards, tom lane