Patent attributes
Methods, systems, and apparatus, including computer programs encoded on computer storage media, for information retrieval. One of the methods includes receiving a search query from a user device at a messaging system; determining one or more relevant messages responsive to the search query, the determining comprising: processing the search query using a first stage of a ranking system, the first stage using a first set of features to identify a first set of relevant message, processing the search query using a second stage of the ranking system, the second stage using a second set of features and the first set of relevant messages to determine a second set of relevant messages, and ranking the second set of relevant messages according to respective scores; and providing one or more results to the user device for display as search results.
