select max(parent_table) slow

We are testing 8.4 and noticed that the performance of

select max(indexed_col) from parent_Table

is the same (slow) as postgres 8.1.x ( our current version).    The
child tables are huge and the indexed_col is not the basis for
partitioning.

I remember that this was an issue from an earlier thread where the
optimizer was not able to use the child partitions only to get the max
value. Is this true for 8.4 ?