Another question is, what should cmin and cmax system columns return? If
we overlay cmin and cmax, cmin and cmax on-disk will always be the same
value. And with phantom cids, it wouldn't be meaningful outside the
inserting/deleting transaction.
The options that I can think of are:
1. Only return cmin and cmax when they mean something, that is within
the inserting / deleting transaction. This is not good if you want to
use them for debugging (and what other use do they have?)
2. Cmin and cmax return the value that's stored on disk, whether or not
they make sense.
3. Remove cmin and cmax system columns to avoid confusion, and replace
them with cminmax, that returns what's on disk.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com