Greg Stark escribió:
> I think minmax indexes are more akin to bitmap indexes. They will be very
> effective for columns with low-cardinality, especially for columns that are
> very clustered. In the extreme if all the values in some regions of the
> table are the same then minmax indexes would be optimal. I wouldn't expect
> them to be very effective for a highly selective column that isn't well
> clustered.
I think clustering is more important than cardinality. I mean you can
have a very useful minmax index on a float column, on which maybe there
are no two identical values.
I certainly don't think minmax indexes will solve all indexing problems.
In the end, they're just one more tool in your DBA toolbox.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services