1. A method comprising: by one or more computing devices, receiving a search query requesting one or more first search results of a first object type, the search query comprising an inner query requesting one or more second search results of a second object type; by one or more computing devices, accessing an inverted index of a data store corresponding to the second object type; by one or more computing devices, retrieving the second search results requested by the inner query using the inverted index of the data store corresponding to the second object type; by one or more computing devices, accessing a forward index of the data store corresponding to the second object type; and by one or more computing devices, retrieving the first search results requested by the search query using the second search results and the forward index of the data store corresponding to the second object type.