public void clear() {
        buffer.clear();
        allPartition.clear();
    }
A buffer that stores data grouped according to partition information, and caches data for
one checkpoint cycle each time.
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/iceberg/src/main/java/org/apache/inlong/sort/iceberg/sink/collections/PartitionGroupBuffer.java