On Thu, 31 Oct 2002 pgsql-bugs@postgresql.org wrote:
> Philip Warner (pjw@rhyme.com.au) reports a bug with a severity of 2
> The lower the number the more severe it is.
>
> Short Description
> View not using index
>
> Long Description
> It seems that a UNION view fails to use underlying table indexes. This
> is a major pain when using subclassed tables which are updated
> frquently - even if the underlying tables are vacuumued regularly, the
> seq scan can take a very long time.
Reasonably current 7.3 beta sources show it doing an index scan for a
sequence like the below on t1.