foreign keys in salesforce.com adapter

Hi,

according the API documentation of salesforce.com is possible access records using the foreign keys

Please see http://www.salesforce.com/us/developer/docs/api/index.htm at Reference > Core Calls > upsert()

“You can use external ID fields as a foreign key, allowing you to access records in a single step instead of querying a record to get the ID first. To do this, specify the foreign key name and the external ID field value.