Re: index in desc order

Szymon Guz <mabewlun@gmail.com> writes:
> On 2 November 2010 10:36, AI Rumman <rummandba@gmail.com> wrote:
>> Is it possible to create an index in descending order?

> create index i on t(i desc);

Note that there is actually no point at all in such a declaration.
The planner is perfectly capable of using backwards indexscans at
need, so the above index doesn't do anything you couldn't do with
a regular ascending-order index.

The cases where this feature is actually worth something is where
you have a multi-column index and you need different sort orders
for the components, for example

    create index xy on t (x asc, y desc);

which could be used to satisfy SELECT ... ORDER BY x ASC, y DESC.

The OP didn't say what he wanted to use the feature for, but
unless it's something like that, there's probably a better way.

            regards, tom lane