7. A method for providing search results, comprising: determining a search label corresponding to a search query; determining, using one or more processors, a plurality of preprocessing functions and an execution sequence in which at least some of the plurality of preprocessing functions are to be performed on the search query based at least in part on the search label corresponding to the search query; performing the plurality of preprocessing functions on the search query to obtain a plurality of preprocessed search queries; selecting a preprocessed search query from the plurality of preprocessed search queries to include into a search plan, wherein selecting the preprocessed search query includes: determining two or more preprocessed search queries of the plurality of preprocessed search queries that meet a precision requirement; and in response to the determination that two or more preprocessed search queries meet the precision requirement, selecting the preprocessed search query from the two or more preprocessed search queries to include in the search plan based at least in part on confidence levels associated with respective ones of the two or more preprocessed search queries; and inputting the search plan into a search engine to obtain the search results.
8. The method of claim 7 , further comprising determining a plurality of precision levels corresponding to respective ones of the plurality of preprocessed search queries based on historical data.