1. A method comprising: in response to a first query to which a search engine returns a first query result, comparing, at a server configured to receive the query results from a search engine, the first query result to multiple prior query results returned by the search engine in response to prior queries, to determine a similarity measure between the first query result and each of the multiple prior query results; identifying unique result items in at least one of the multiple prior query results that are not included in the first query result, in response to determining the similarity measure for the at least one of the multiple prior query results is not less than a defined similarity threshold; and combining the first query result and the unique result items as a combined search result responsive to the first query.