The DBA is considering whether it would be advantageous to partition the invoice table on invoice date using one-month ranges.
The primary index is currently defined as unique, but would have to be redefined as nonunique if the table were row‑partitioned. There is a business requirement to guarantee that invoice numbers are unique, so the DBA would need to define a uniqueness constraint on the invoice number column. If this uniqueness constraint is added, it creates an additional secondary index on the table (other than UPIs, all uniqueness constraints are implemented internally as USIs irrespective of whether they are specified explicitly as a UNIQUE constraint, a PRIMARY KEY constraint, or a USI constraint. See “Using Unique Secondary Indexes to Enforce Row Uniqueness” on page 457), which increases processing on insert, delete, and update operations, as well as requiring additional disk capacity to store the resulting secondary index subtable. The base table is also larger by two bytes per row, further increasing the required disk space.