Index scan?

Hi

Does anyone know why the following occurs?
 coza=> explain select * from accounts where domain >= '%' order by domain; NOTICE:  QUERY PLAN:
 Index Scan using domain_idx on accounts  (cost=1434.50 rows=19611 width=106)

and
 coza=> explain select * from accounts order by domain; NOTICE:  QUERY PLAN:
 Sort  (cost=3068.39 rows=58830 width=106)   ->  Seq Scan on accounts  (cost=3068.39 rows=58830 width=106)

Surely both queries give the same result set, yet the second example does not
use the index causing unnecessary overhead.

I am running version 6.5 (haven't upgraded to 6.5.1 as yet)

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Regards
Theo