I have been reading this conversation for a few days now and I just wanted to ask this. From the release notes, one of the new additions in 8.3 is (Allow col IS NULL to use an index (Teodor)).
Sorry, if I am missing something here, but shouldn't something like this allow us to get a (fast) accurate count ?
SELECT COUNT(*) from table WHERE indexed_field IS NULL + SELECT COUNT(*) from table WHERE indexed_field IS NOT NULL
For PostgreSQL: You still don't know whether the row is visible until you check the row. That it's NULL or NOT NULL does not influence this truth.
