> But you don't really need to look at the index (if it even exists
> at the time you do the ANALYZE). The extent to which the data is
> ordered in the table is a property of the table, not the index.
Think compound, ascending, descending and functional index.
The (let's call it) cluster statistic for estimating indexscan cost can only
be deduced from the index itself (for all but the simplest one column btree).
Andreas