postgres=#
postgres=# CREATE TABLE test1 (a character(4));
CREATE TABLE
postgres=#
postgres=# INSERT INTO test1 VALUES ('ok');
INSERT 0 1
postgres=# SELECT a, char_length(a) FROM test1;
a | char_length
------+-------------
ok | 2
(1 row)
postgres=#
postgres=# drop table test1;
DROP TABLE
postgres=#
postgres=#