刚试了 postgresql 7.4.6, 不行的

testonly=# CREATE TABLE test (id INTEGER PRIMARY KEY, name VARCHAR(20));
CREATE TABLE
testonly=# CREATE INDEX test_name_idx ON test (name);
CREATE INDEX
testonly=# EXPLAIN SELECT * FROM test WHERE (name like 'ab%');
QUERY PLAN
------------------------------------------------------
Seq Scan on test (cost=0.00..22.50 rows=5 width=28)
Filter: ((name)::text ~~ 'ab%'::text)
(2 rows)