On Wed, Mar 9, 2011 at 6:01 PM, Jim Nasby <jim@nasby.net> wrote:
> Unfortunately, I don't think the planner actually has that level of knowledge.
Actually, I don't think it would be that hard to teach the planner
about that special case...
> A more reasonable fix might be to teach the executor that it can do 2 scans of the index: one to get non-null data
anda second to get null data. I don't know if the use case is prevalent enough to warrant the extra code though.
That would probably be harder, but useful. I thought about working on
it before but got sidetracked onto other things.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company