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purge *- discard historical data
purge classname [ before abstime ] [ after reltime ]
Purge allows a user to specify the historical retention properties of a class. The date specified is an absolute time such as Jan 1 1987, and POSTGRES will discard tuples whose validity expired before the indicated time. Purge with no before clause is equivalent to purge before now. Until specified with a purge command, instance preservation defaults to forever.
The user may purge a class at any time as long as the purge date never decreases. POSTGRES will enforce this restriction, silently.
/* Always discard data in the EMP class */ /* prior to January 1, 1989 */ purge EMP before "Jan 1 1989" /* Retain only the current data in EMP */ purge EMP
Error messages are quite unhelpful. A complaint about "inconsistent times" followed by several nine-digit numbers indicates an attempt to "back up" a purge date on a relation.