Bug #821: bug when using between or <= on varchar fields

Thomas Piszczek (t(dot)piszczek(at)tallence(dot)com) reports a bug with a severity of 3
The lower the number the more severe it is.

Short Description
bug when using between or <= on varchar fields

Long Description
I just recognized that when using between or <= and >= on varchar fields postgresql behaves quite strange. If i search for users in my user table which does contain last_name entries beginning with o or p and have an sql that searches for "lower(last_name)>='k' and lower(last_name)<='o'" i get all results between k and n, but no "o-entries". If i do a "lower(last_name)>='k' and lower(last_name)<=p it works. I then get all results between k and o(no p's).
Using "between 'k' and 'o'" behaves just the same.
I think this is a bug(i'm using postgresql 7.2.3 on suse linux 8.1 with php 4.2.3)

Sample Code
SELECT user_id,.......
FROM cma_user
WHERE
LOWER(last_name)>='k' AND LOWER(last_name)<='o'

SELECT user_id,.......
FROM cma_user
WHERE
LOWER(last_name) BETWEEN 'k' AND 'o'

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