As per the documentation.
However, it doesn't actually appear to be the case. For example, here is a list of order_id
properties I sent to the log while iterating through a list of ScoredDocuments
returned by a search query:
62083050
62083026
62083044
62083032
62083043
62083057
62083055
62083013
62083049
62083047
I am using SDK 1.7.3.