7. The method of claim 1 , wherein, random sampling is used for sampling query data in the query keyword subset according to the sampled size.
7. The method of claim 1 , wherein, random sampling is used for sampling query data in the query keyword subset according to the sampled size. 8. The method of claim 7 , wherein, random sampling includes generating a random number and selecting a query keyword in the query keyword subset that is associated with the random number.