On Mon, Nov 12, 2018 at 9:34 PM Noah Misch <n...@leadboat.com> wrote: > On Sat, Oct 13, 2018 at 11:45:17PM +1300, Thomas Munro wrote: > > + /* Set a different seed for random() in every backend. */ > > + srandom((unsigned int) MyProcPid ^ (unsigned int) MyStartTimestamp); > > > - TimestampDifference(0, port->SessionStartTime, &secs, &usecs); > > - srandom((unsigned int) (MyProcPid ^ (usecs << 12) ^ secs)); > > Compared to the old code, the new code requires more wall time to visit every > possible seed value. New code xor's the PID bits into the fastest-changing > timestamp bits, so only about twenty bits can vary within any given one-second > period. (That assumes a PID space of twenty or fewer bits; fifteen bits is > the Linux default.) Is that aspect of the change justified?
Hmm, right. How about applying pg_bswap32() to one of the terms, as an easy approximation of reversing the bits? -- Thomas Munro http://www.enterprisedb.com
