1. One or more processor-accessible tangible media comprising processor-executable instructions for combining rankers to perform a search operation, wherein the processor-executable instructions, when executed, direct a system to perform acts comprising: ascertaining a count of query-identifier pair instances in log data based on a query; performing a search for the query to produce a set of search results; and ranking the set of search results by relevance score with a document-based ranker and a log-based ranker using a weighting factor that is adapted responsive to the count of the query-identifier pair instances in the log data such that a relative contribution of the log-based ranker increases as the count of the query-identifier pair instances in the log data increases.