3. The optimizing method according to claim 1 , wherein said determining the filtering performance for each of the complex predicates comprises: determining a number of data records obtained by performing a query using only the complex predicate; and calculating a filter factor for the complex predicate based on the number of the data records obtained by performing the query.
3. The optimizing method according to claim 1 , wherein said determining the filtering performance for each of the complex predicates comprises: determining a number of data records obtained by performing a query using only the complex predicate; and calculating a filter factor for the complex predicate based on the number of the data records obtained by performing the query. 4. The optimizing method according to claim 3 , wherein said re-ordering the complex predicates in the predetermined layer comprises: re-ordering the complex predicates in the predetermined layer based on the filter factor, according to the predicate conjunction between the complex predicates in the predetermined layer, wherein the re-ordering the complex predicates is performed in at least one of manners of: the complex predicate with a filter factor of a smaller value is ranked before the complex predicate with a filter factor of a larger value, in the case that the predicate conjunction is AND; and the complex predicate with a filter factor of a larger value is ranked before the complex predicate with a filter factor of a smaller value, in the case that the predicate conjunction is OR.