trackIds

The track IDs of the dynamic entities to query for. If this array is populated, the query will only return entities with track IDs that match the values in this array.

The track ID is an attribute value in a DynamicEntityDataSource that uniquely identifies a dynamic entity. For an ArcGISStreamService, the track ID attribute is defined by the ArcGISStreamServiceInfo.trackIdField property. For a custom DynamicEntityDataSource, the track ID attribute is defined by the DynamicEntityDataSourceInfo.entityIdFieldName property.