On 22 May 2012 18:24, Jeff Janes <
jeff.janes@gmail.com> wrote:
> Now that there are index only scans, there is a use case for having a
> composite index which has the primary key or a unique key as the
> prefix column(s) but with extra columns after that. Currently you
> would also need another index with exactly the primary/unique key,
> which seems like a waste of storage and maintenance.
>
> Should there be a way to declare a "unique" index with the unique
> property applying to a prefix of the indexed columns/expression? And
> having that, a way to turn that prefix into a primary key constraint?
>
> Of course this is easier said then done, but is there some reason for
> it not to be a to-do item?