Regexps and Indices.

Hi,
    I'm sure that this has come up many times before but :

I have just upgraded from 7.0.2 to 7.2.2 using the latest Mandrake 9.0 RPMS.
The database structure is unchanged but I now find that the db refuses to use
the available index WHERE NAME ~ '^NAME' even with enable_seqscan set off. Am
I missing something ?


                                        Table "t_patient"
        Column        |         Type               |
Modifiers
----------------------+-----------------------+---------------------------------------------------
 prn                    | integer                     | not null default
nextval('patient_prn_seq'::text)
 caseno              | character(14)            | not null
 surname            | character varying(20) | not null
 forename           | character varying(16) |
 dob                  | date                          |
 approx_date      | boolean                     |
 sex                   | character(1)              |
 hospital             | character(4)              |
 ward                 | character(4)              |
 cons_type         | character(1)              |
 cons_attr           | character(4)              |
 consultant          | text                          |
 maiden_name     | character varying(20) |
 nhs_no              | character varying(16) |
 pat_address       | text                          |
 cardinal_blood_group | character varying(16) |
 displist                 | character(8)             |

Indexes: t_patient_caseno,
            t_patient_mn_fn,
            t_patient_surname_forename
Unique keys: t_patient_prn

pathology=# explain select * from t_patient where surname ~ '^SMIT';
NOTICE:  QUERY PLAN:

Seq Scan on t_patient  (cost=100000000.00..100000440.89 rows=64 width=245)

EXPLAIN
pathology=# set enable_seqscan to off;
SET VARIABLE
pathology=# explain select * from t_patient where surname ~ '^SMIT';
NOTICE:  QUERY PLAN:

Seq Scan on t_patient  (cost=100000000.00..100000440.89 rows=64 width=245)

EXPLAIN