On Fri, Jul 3, 2015 at 1:55 PM, Sawada Masahiko <sawada.m...@gmail.com> wrote: > > On Fri, Jul 3, 2015 at 1:23 AM, Simon Riggs <si...@2ndquadrant.com> wrote: > > On 2 July 2015 at 16:30, Sawada Masahiko <sawada.m...@gmail.com> wrote: > > > >> > >> Also, the flags of each heap page header might be set PD_ALL_FROZEN, > >> as well as all-visible > > > > > > Is it possible to have VM bits set to frozen but not visible? > > > > The description makes those two states sound independent of each other. > > > > Are they? Or not? Do we test for an impossible state? > > > > It's impossible to have VM bits set to frozen but not visible.
In patch, during Vacuum first the frozen bit is set and then the visibility will be set in a later operation, now if the crash happens between those 2 operations, then isn't it possible that the frozen bit is set and visible bit is not set? > These bit are controlled independently. But eventually, when > all-frozen bit is set, all-visible is also set. > Yes, during normal operations it will happen that way, but I think there are corner cases where that assumption is not true. With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
