Question about indexing!

I made the table like this;

dsn=# \d pgsql_bbs                            Table "pgsql_bbs" Attribute  |  Type   |                    Modifier
              
 
-------------+---------+-------------------------------------------------id          | integer | not null default
nextval('pgsql_bbs_seq'::text)topic      | text    | cdate       | integer | default (abstime(now()))::int4subject
|text    | content     | text    | deleted     | integer | default 0gid         | integer | not nullpos         |
integer| not nullpid         | integer | not nullrdepth      | integer | not null
 
Indices: pgsql_bbs_pkey,        pgsql_cdate,        pgsql_deleted,        pgsql_gid,        pgsql_gid_pos,
pgsql_pid,       pgsql_pos,        pgsql_topic,        pgsql_topic_deleted,        pgsql_uid
 

And I tried next query;

select * from pgsql_bbs where topic = 'qna' and deleted < 2       order by gid desc, pos asc limit 20, 0;

But this query is not using index!

The next is result of explain of this query:

dsn=# explain select * from pgsql_bbs where topic = 'qna' and deleted < 2 
dsn-#        order by gid desc, pos asc limit 20, 0;
NOTICE:  QUERY PLAN:

Limit  (cost=15.71..15.71 rows=11 width=245) ->  Sort  (cost=15.71..15.71 rows=11 width=245)       ->  Index Scan using
pgsql_topic_deletedon pgsql_bbs  (cost=0.00..15.51 rows=11 width=245)
 

EXPLAIN

How method is exist enhancing performance of this query?

Thank you for read this question.

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