On Tue, Apr 6, 2010 at 5:37 PM, Samuel Gendler
<sgendler@ideasculptor.com> wrote:
> In part, I'm surprised that the index scan takes as long as it does,
> since I'd think an index would be able to return the set of keys
> relatively quickly. But that's a secondary issue.
We don't actually have a facility built into the index-scan machinery
to scan for distinct keys. It's doing a full scan of the index and
then unique-ifying the results afterward. It produces the right
answers, but it's definitely not as fast as it could be.
The planner is not as smart about partitioned tables as it could be,
either. A scan of the partitioned tables is implemented as an append
node with one member per partition; and the planner isn't very good at
pushing things down through append nodes.
...Robert
