International Business Machines Corporation
Enable merge join on encrypted data

Abstract:

An approach is provided for encrypting data. Using an encryption function, values of keys in a first database table are encrypted. The encryption function is determined to be homomorphic to sorting operators. A decryption function that decrypts the encrypted keys is determined to be homomorphic to sorting operators. Responsive to the encryption and decryption functions being determined to be homomorphic, a merge join operation is selected. The merge join operation operates on the first database table and a second database table and includes the decryption function in a joining condition. Using the merge join operation, an execution of a query is optimized. The query accesses one or more data items in the first or second database table.