PostgreSQL example:
CREATE OR REPLACE FUNCTION f_random_text(
length integer
)
RETURNS text AS
$body$
WITH chars AS (
SELECT unnest(string_to_array('A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 0 1 2 3 4 5 6 7 8 9', ' ')) AS _char
),
charlist AS
(
SELECT _char FROM chars ORDER BY random() LIMIT $1
)
SELECT string_agg(_char, '')
FROM charlist
;
$body$
LANGUAGE sql;
DROP TABLE IF EXISTS tmp_test;
CREATE TEMPORARY TABLE tmp_test (
id serial,
data text default f_random_text(12)
);
INSERT INTO tmp_test
VALUES
(DEFAULT, DEFAULT),
(DEFAULT, DEFAULT)
;
SELECT * FROM tmp_test;
id | data
----+--------------
1 | RYMUJH4E0NIQ
2 | 7U4029BOKAEJ
(2 rows)
Apparently you can do this. (Of course, you can add other characters as well, or use other random string generator as well - like this, for example.)
Enhancing Jack Douglas's answer to avoid the need for PL/PgSQL looping and bytea concatenation, you can use:
CREATE OR REPLACE FUNCTION random_bytea(bytea_length integer)
RETURNS bytea AS $body$
SELECT decode(string_agg(lpad(to_hex(width_bucket(random(), 0, 1, 256)-1),2,'0') ,''), 'hex')
FROM generate_series(1, $1);
$body$
LANGUAGE 'sql'
VOLATILE
SET search_path = 'pg_catalog';
It's a simple SQL function that's cheaper to call than PL/PgSQL.
The difference in performance due to the changed aggregation method is immense for larger bytea values. Though the original function is actually up to 3x faster for sizes < 50 bytes, this one scales much better for larger values.
Or use a C extension function:
I've implemented a random bytea generator as a simple C extension function. It's in my scrapcode repository on GitHub. See the README there.
It nukes the performance of the above SQL version:
regress=# \a
regress=# \o /dev/null
regress=# \timing on
regress=# select random_bytea(2000000);
Time: 895.972 ms
regress=# drop function random_bytea(integer);
regress=# create extension random_bytea;
regress=# select random_bytea(2000000);
Time: 24.126 ms
Best Answer
If you're happy with a hex string, you could do:
You could also write a user-defined function if you want a very specific type of string. For this, you would need SSH access on the Netezza appliance and some basic knowledge of C++. It may be simpler for you to write these functions in Lua if you're not comfortable with C++ or if you don't have an account on the appliance, but this requires Netezza Analytics to be installed.