Kari,
Why not select count(*) from the table and multiply it by a true 0.0 - 1.0
pseudo random number generator? Then adjust the outcome for the range of
uids. If the uids (or some other column) are contiguous starting at 0,
this would be a snap.
Rick
Tom Lane
<[EMAIL PROTECTED]> To: Kari Lavikka <[EMAIL
PROTECTED]>
Sent by: cc: [EMAIL PROTECTED]
[EMAIL PROTECTED] Subject: Re: [GENERAL] Selecting a
random row
tgresql.org
11/04/2004 10:25 AM
Kari Lavikka <[EMAIL PROTECTED]> writes:
> --
> -- Choose a random point between 0 and max_uid and select the first
> -- value from the bigger part
> --
> CREATE OR REPLACE FUNCTION random_uid() RETURNS int4 AS
> 'SELECT uid FROM users u WHERE u.status = ''a'' AND uid >=
> cast(cast(max_uid() - 1 AS FLOAT) * random() AS INTEGER) ORDER BY uid
> ASC LIMIT 1'
> LANGUAGE 'sql';
This isn't going to do what you think because the random() function is
re-evaluated at every row of the table. (For that matter, so is
max_uid(), which means performance would suck even if it worked ...)
I'd suggest rewriting in plpgsql so you can assign the (max_uid-1)*random()
expression to a variable and then just use the variable in the SELECT.
regards, tom lane
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