Sample filter implementation restricting sources based on a SQL query result. This SQL query can select from any regular SQL table or view accessible from the namespace the filter is instantiated from. The query should select sources through returning either of the following as result columns (case sensitive!):
- IdField and GroupField: the two columns used together as identifiers when adding the sources to the domain: Local Reference (IdField) and Group Name (GroupField). See also %iKnow.Source.SQL.Lister.
- ExternalId: the full External ID of the sources to be selected.
- SourceId: the (internal) Source ID of the sources to be selected.
WARNING: these filters are not invalidated automatically if the values in the tables accessed by the supplied SQL query change. It is up to the user to decide, based on the specifics of the environment, whether filter instances of this class can be cached meaningfully (see the useCache parameter of Initialize) and/or should be invalidated explicitly (see Invalidate or ClearCachedFilter).
Subclasses should implement this method to build a string representation of the filter instance. It should start with the filter class name, followed by a pipe (|) character and then a string representation that can be interpreted by its RestoreFilterFromStringInternal implementation.