public RowType getSplitKeyType() {
        return splitKeyType;
    }
read the whole table when split start and split end are null
@return whether the split reads the whole table
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/mysql-cdc/src/main/java/org/apache/inlong/sort/cdc/mysql/source/split/MySqlSnapshotSplit.java