plpgsql function to generate random readable strings

Question

I have written the following function but it's isn't returning anything when I run it. Can somebody help identify the issue?

CREATE OR REPLACE FUNCTION GenerateReadableRandomString (
len INT
) RETURNS varchar AS
$$
DECLARE
validchars VARCHAR;
randomstr VARCHAR;
randint INT;
i INT;

BEGIN

validchars := 'ABCEFHJKLMNPRTWXY3478';
i := 0;

LOOP
    randint := ceil(random() * char_length(validchars));
    randomstr := randomstr || substring(validchars from randint for 1);
    i := i + 1;
    EXIT WHEN i = len;
END LOOP;

RETURN randomstr;
END;
$$
LANGUAGE plpgsql;

Pavel Stehule · Accepted Answer · 2010-03-28 06:02:18Z

2

faster code can be

CREATE OR REPLACE FUNCTION rstr(int)
RETURNS text AS $$
SELECT array_to_string(ARRAY(SELECT substring('ABCEFHJKLMNPRTWXY3478' FROM (random()*21)::int + 1 FOR 1) 
                                FROM generate_series(1,$1)),
                       '') 
$$ LANGUAGE sql;

answered Mar 28, 2010 at 6:02

Pavel Stehule

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1 Comment

ealdent Over a year ago

This is at least an order of magnitude faster. +1

Scott Bailey · Accepted Answer · 2010-03-26 06:31:20Z

1

Yeah the problem is that you haven't initialized your variable randomstr. And when you concat something with null you get null

answered Mar 26, 2010 at 6:31

Scott Bailey

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