"Sergey E. Koposov" <math@xxxxxxxxxx> writes: > So among 10^5 random numbers there are already 3 collisions. Which doesn't > seem right for the function which generate randoms of double precision The underlying random() function only generates 31-bit integers, so collisions aren't as improbable as they might seem. See http://en.wikipedia.org/wiki/Birthday_paradox > It is also interesting that in the table tmpx1 (if I actually output the > values using select id from tmpx1) I do not see equal numbers at all but I see > for example two values which are close to each other: > 0.511193082667887 > 0.511194097343832 > First it seems strange that they have been merged into one group by "groupby". They aren't; or at least you've not provided any evidence that they were. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
