1. A method implemented by one or more computing devices of a search service, the method comprising: using a model to rank item in a search result, the model formed using an initial set of data; generating an update using a subsequent set of data, which is formed after the initial set of data, that provides feedback describing user interaction with one or more of the items in the search result, the generating of the update performed without use of at least a portion of the initial set of data; and employing the model and the update to rank items in a search result for a subsequent search.