Unique Primary Index Considerations
The following factors describe the general performance considerations associated with
UPIs guarantee an even distribution of table rows across the AMPs when there are many
more unique values than AMPs on the system.
UPIs always guarantee the best retrieval and update performance for single table row
UPI values are never associated more than one base table row.
UPIs retrievals and updates never require a spool file.
Uniqueness is enforced by the system using the UPI (thereby avoiding the need for
duplicate row checks for multiset tables).