On Wed, Aug 24, 2005 at 04:29:00PM +0200, Bo Lorentsen wrote:
> Michael Fuhr wrote:
> >...which is the same reason a cursor doesn't know how many rows it will
> >fetch until you fetch them all (or MOVE to the end of the cursor,
> >which fetches the rows internally).
>
> So, Postgresql is not hidding something for me, it just, like me, don't
> know ?
Right -- when you open a cursor PostgreSQL doesn't know how many
rows it will return. PostgreSQL selects a query plan based on an
*estimate* of how many rows the query will return, but until you
fetch all the rows you can't know for sure how many rows there will
be.
--
Michael Fuhr
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
