1. A system, comprising: one or more computer processors; and a memory containing a program, which when executed by the one or more computer processors, performs an operation comprising: determining that a received query comprises a first predicate specifying a comparison operator and a second predicate specifying an IS NULL operator; modifying the received query, wherein modifying the received query comprises: replacing the comparison operator of the first predicate with an extended comparison operator, wherein the extended comparison operator is not a NULL operator and returns column values having a value predefined to represent NULL values; and removing the second predicate and the IS NULL operator from the received query; and processing the modified query, wherein processing the modified query comprises: searching a set of column values in a database management system (DBMS) satisfying the extended comparison operator of the first predicate; and returning at least a first column value, of the set of column values, as responsive to the modified query, wherein the first column value satisfies the extended comparison operator of the first predicate by matching the value predefined to represent NULL values.