presto-cassandra/src/main/java/io/prestosql/plugin/cassandra/CassandraSplit.java/CassandraSplit/getWhereClause
class CassandraSplit:    public String getWhereClause()
    {
        if (partitionId.equals(CassandraPartition.UNPARTITIONED_ID)) {
            if (splitCondition != null) {
                return " WHERE " + splitCondition;
            }
            else {
                return "";
            }
        }
        else {
            if (splitCondition != null) {
                return " WHERE " + partitionId + " AND " + splitCondition;
            }
            else {
                return " WHERE " + partitionId;
            }
        }
    }