More about Declare
Index rules
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During execution of a Declare Index rule, the page on which
the rule operates becomes the primary page. The page keyword
PRIMARY and the results of the
tools.getPrimaryPage() PublicAPI method reflect
this change. When the Declare Index rule execution completes,
the primary page of the calling activity resumes as primary.
When
you save a rule form, Operator ID form, or other form defined
through the FormBuilder tool and saved as instances of the
Rule-File-Form class, Declare Index rules for that
class are not activated. (However, property changes made
to such instances through activities do cause Declare Index
rules to execute.)
As a best practice, use Declare Trigger rules, not Declare Index rules, to monitor property changes in classes that have a FormBuilder form defined.
No other rules explicitly reference Declare Index rules. After you save a Declare Index rule, Process Commander immediately runs it when and as needed.
You can use an index to improve access to a property that is not an exposed column in the database table supporting the source class, or to access embedded values that may appear more than once in the instances of the source class.
After you define an index through this rule, the system maintains index data automatically using forward chaining.
Index processing occurs at every database commit operation. Index processing automatically deletes old indexes that are no longer accurate, updates existing indexes, and adds new index instances, as required, to match current values of the source instance. When a data object is deleted (typically by an Obj-Delete method followed by a Commit method) the system examines all associated indexes and deletes them as appropriate.
Normally, the system updates indexes automatically during the Commit method that completes an earlier Obj-Save or Obj-Delete method. Index processing occurs only if any of the Source Class Property values (entered on the Index tab) have changed from their previous values.
The pyIndexCount value, a system-derived integer value, is included in as part of the key of every Index- instance, and makes the key unique.
Do not use Property-Set or
Obj-Save methods on instances in a class derived from the
Index- base class. Use only Declare Index rules to
change these properties and instances.
When a work object or other instance is committed, multiple Declare Index rules may automatically run to create and delete index instances. If such processing causes more than 100 indexes to be created, an alert is added to the Alert log, to draw attention to a possible design or performance issue. See How to detect when the number of declare indexes exceed the specified threshold.
For an example, see 
Pega Developer Network article PRKB-25678 Understanding the PEGA0034 Alert.
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 object is
indexed, you can report on all work objects containing a
specific UPC code. Reference the index class on the
Contents and Join tabs of the List View form or Summary View
form.
To produce detailed output
from the inference engine, use the Set Logging Level tool the
set logging for the following class to DEBUG:
com.pega.pegarules.engine.database.Indexer
Through planning and coordination with a database administrator, application developers can define indexes that greatly aid in user productivity. However, indexing introduces redundant data and extra processing. Be careful to avoid defining indexes that are not truly needed or that negatively affect performance.
Indexing can improve performance by allowing quick lookup of certain properties based on a property value that is not exposed in database table supporting the original instance, or that has multiple values (and so cannot be exposed).
For example, using appropriately defined indexes, you can quickly identify all work objects that contain a customer who resides in a specified Zip code.
If the index instances in your system are incomplete, or become corrupted or suspect, you can recreate them:
A system administrator can recompute Index- instances for some or all instances of the underlying class using the prdbutil utility option Populate Exposed Columns. (You can select the Reindex Instances option even when no database columns need to be populated. See Working with the PegaRULES database - Using the Column Populator utility.
You can force re-indexing to occur upon commit even if no tracked properties are changed. To do this, add the property @baseclass.pzReindex with a value of "true" to the page containing the object before saving and committing the object. This property causes the system to skip change tracking and recompute indexes for this object from scratch. Because of added overhead, use this technique only in testing, debugging, or low-volume situations.
