typo: XIDs are actually compared using modulo-2^32 arithmetic

Hi,

It seems there is a typo here:
 http://www.postgresql.org/docs/devel/static/routine-vacuuming.html#VACUUM-FOR-WRAPAROUND

where we say that we compare XIDs using arithmetic modulo 2^31, which
should instead be 2^32 (as it is with uint32, e.g. xid_age).

Best wishes,
Dr. Gianni Ciolli - 2ndQuadrant Italia
PostgreSQL Training, Services and Support
gianni.ciolli@2ndquadrant.it | www.2ndquadrant.it