On Tue, May 7, 2019 at 3:12 PM Myles Miller wrote:
> No, the function is returning just one letter, either 'A' or 'B', not
> multiple values.
Your random function is being evaluated ONCE FOR EACH ROW.
i.e, it's doing something like:
select y from
( SELECT y, chr(round(random())::int + 65) as
> > # SELECT y FROM x WHERE y = chr(round(random())::int + 65);
> > y
> > ---
> > A
> > B
> > (2 rows)
> Here you got a random value in the lower range of 0..1 for the record with
> value ‘A’, so that’s a match, and one in the higher range for value ‘B’, a
> match again, so you get 2 rows.
No,
On Tue, May 07, 2019 at 12:17:12PM +, Daniel Perrett wrote:
> The WHERE expression (and therefore the random function) is being evaluated
> once per row, not once per query.
> If you run this query a few times, you will see the problem:
> SELECT y, chr(round(random())::int + 65) FROM (SELECT '
> On 7 May 2019, at 13:53, Myles Miller wrote:
>
> PROBLEM:
> Strings or characters generated by any random function (including pg_crypto
> gen_random_bytes) are matching a string/char index in surprising ways.
I fail to see anything surprising in your examples.
> Reduced down to its simplest
