> Hmm,Index scan is chosen to select all rows.
> AFAIK,sequential scan + sort is much faster than index scan in
> most cases.
>
> cost of index scan < cost of sequential scan + cost of sort
>
This is usually true. It might need resources though that are not available,
e.g. 8 GB sort space. It also depends on whether the application is
interested in
first row (interactive), or all row performance (batch). Other DB's can
switch modes
to decide on the wanted behavior. So I think there is no yes/no decision on
this.
Andreas
