set enable_seqscan=off;
CREATE TABLE test_char (
	i "char"
);
INSERT INTO test_char VALUES ('a'),('b'),('c'),('d'),('e'),('f');
CREATE INDEX idx_char ON test_char USING rum (i);
SELECT * FROM test_char WHERE i<'d'::"char" ORDER BY i;
 i 
---
(0 rows)

SELECT * FROM test_char WHERE i<='d'::"char" ORDER BY i;
 i 
---
(0 rows)

SELECT * FROM test_char WHERE i='d'::"char" ORDER BY i;
 i 
---
 d
(1 row)

SELECT * FROM test_char WHERE i>='d'::"char" ORDER BY i;
 i 
---
 d
 e
 f
(3 rows)

SELECT * FROM test_char WHERE i>'d'::"char" ORDER BY i;
 i 
---
 e
 f
(2 rows)