On Sat, Jan 25, 2014 at 5:25 PM, Andres Freund <and...@2ndquadrant.com> wrote: >> I'm also wondering about >> whether we've got the right naming here. AFAICT, it's not the case >> that we're going to use the "catalog xmin" for catalogs and the "data >> xmin" for non-catalogs. Rather, the "catalog xmin" is going to always >> be included in globalxmin calculations, so IOW it should just be >> called "xmin". > > Well, not really. That's true for GetSnapshotData(), but not for > GetOldestXmin() where we calculate an xmin *not* including the catalog > xmin. And the data_xmin is always used, regardless of > catalog/non_catalog, we peg the xmin further for catalog tables, based > on that value. > The reason for doing things this way is that it makes all current usages > of RecentGlobalXmin safe, since that is the more conservative > value. Only in inspected location we can use RecentGlobalDataXmin which > *does* include data_xmin but *not* catalog_xmin.
Well, OK, so I guess I'm turned around. But I guess my point is - if one of data_xmin and catalog_xmin is really just xmin, then I think it would be more clear to call that one "xmin". -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers