Create a Declare Index rule to define criteria under which Pega Platform automatically maintains index instances for faster access. An index can improve search and reporting access for properties that cannot be exposed as database columns because they are embedded within an aggregate property. Creating a Declare Index rule is an alternative to the approach used by the Property Optimization tool.
After you implement a declarative index, reports can use the indexed property value as a selection criteria. For example, if an array of embedded Universal Product Code (UPC) codes in a work item is indexed, you can report on all work items containing a specific UPC code by referencing the index class on the Contents and Join tabs of the report definition form.
As a best practice, do not create declarative indexes for top-level Single Value properties.