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Created October 21, 2013 18:48
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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;
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