djb2.sql

CREATE OR REPLACE FUNCTION djb2_hash(string text)
 RETURNS bigint
 LANGUAGE sql
AS $$
WITH RECURSIVE t(seed, string) AS (
    VALUES (
        87049::bigint,
        $1
    )
UNION ALL
    SELECT
        (
            (
                (t.seed << 5) #
                t.seed #
                ascii (
                    substr (
                        t.string,
                        1,
                        1
                    )
                )
            )
        ),
        substr (
            t.string,
            2
        )
    FROM t
)
SELECT seed & ~(1::bigint << 31)
FROM t
WHERE string = ''
$$;

WITH v(s) AS (
    VALUES
        ('foo'),
        ('bar'),
        ('http://www.disqus.com'),
        ('etc'),
        ('etc.')
)
SELECT s, djb2_hash(s)
FROM v;