Daniel: On Thu, Aug 18, 2016 at 5:24 PM, Daniel Verite <dan...@manitou-mail.org> wrote: >> unless you know of an easy way to generate a random permutation on the >> fly without using a lot of memory, I do not. > It could be done by encrypting the stream. > For 32 bits integers: > https://wiki.postgresql.org/wiki/Skip32 > For 64 bits integers: > https://wiki.postgresql.org/wiki/XTEA
Nearly, probably good enough for tests, but only generates a pseudorandom permutation if you encrypt 2**32/64 values, not with the 1..1E7 range, it will map them into 1E7 different numbers in the range 2**32/64. I think there are some pseudo-random number generators which can be made to work with any range, but do not recall which ones right now. Francisco Olarte. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
