Reg Me Please wrote:
While I would not spend resources in fine tuning the count(*), I would spend some to underastand why and how the other ones do it better. Just to be better.
The problem is well understood, and there is extensive discussion in the mailing lists archives. The basic problem is that with PG's implementation of MVCC the indexes don't have row visibility information. The simple solution of adding it to every index entry would increase index size substantially imposing costs on every index access and update.
There's a thread in -hackers called "Visibility map thoughts" that is looking at the situation again and if/how to implement visibility information in a compact form.
-- Richard Huxton Archonet Ltd ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
