public RelDataType inferReturnType(SqlOperatorBinding opBinding) { SqlCallBinding callBinding = (SqlCallBinding) opBinding; ExplicitOperatorBinding newOpBinding = new ExplicitOperatorBinding( opBinding, collectOperandTypes( callBinding.getValidator(), callBinding.getScope(), callBinding.getCall())); return SqlTypeStrategies.rtiNullableBoolean.inferReturnType(newOpBinding); }