Each JavaScript filter must defined one or more functions that are used
to operate the filter process. The
filter() function must be
defined, as it contains the primary operation sequence for the defined
filter. The function is supplied the event from the THL as the events
are processed by the replicator.
In addition, two other JavaScript functions can optionally be defined that are executed before and after the filter process. Additional, user-specific, functions can be defined within the filter context to support the filter operations.
The prepare() function is
called when the replicator is first started, and initializes the
configured filter with any values that may be required during the
filter process. These can include loading and identifying
configuration values, creating lookup, exception or other reference
tables and other internal JavaScript tables based on the
configuration information, and reporting the generated configuration
or operation for debugging.
The filter() function is
the main function that is called each time an event is loaded from
the THL. The event is
parsed as the only parameter to the function and is an object
containing all the statement or row data for a given event.
The release() function is
called when the filter is deallocated and removed, typically during
shutdown of the replicator, although it may also occur when a
processing thread is restarted.