On Wed, Mar 9, 2011 at 6:01 PM, Jim Nasby <j...@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 and a 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

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