11. The system of claim 9 , wherein the indexing module is configured to: perform a hash function to associate the user identifier to a particular partition of the user-term index; and select the particular partition of the user-term index.
11. The system of claim 9 , wherein the indexing module is configured to: perform a hash function to associate the user identifier to a particular partition of the user-term index; and select the particular partition of the user-term index. 14. The system of claim 11 , wherein the hash function takes the modulo of the user identifier by the number of partitions.