Alex,
> On postgres 7.2.3 I have found what follows:
>
> explain select * from documents where iddoc>1;
>
> Seq Scan on lotti (cost=0.00..831.79 rows=26783 width=98)
>
> EXPLAIN
> explain select * from documents where iddoc=1;
>
> Index Scan using lotti_pkey on lotti (cost=0.00..2.26 rows=1
> width=98)
>
> Why index is not used for operators > and < ????
Because ">" is returning 26,000 rows. When you return that many rows,
a Seq Scan is faster.
-Josh