On 6 June 2017 at 12:13, Ashutosh Bapat <ashutosh.bapat@enterprisedb.com> wrote:
> What happens when the epoch is so low that the rest of the XID does
> not fit in 32bits of tuple header? Or such a case should never arise?
Storing an epoch implies that rows can't have (xmin,xmax) different by
more than one epoch. So if you're updating/deleting an extremely old
tuple you'll presumably have to set xmin to FrozenTransactionId if it
isn't already, so you can set a new epoch and xmax.
-- Craig Ringer http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services