@Override
    public void processElement(StreamRecord<RowData> element) throws Exception {
        partitionGroupBuffer.add(element.getValue());
    }
This Operator has two functional above:
1. Aggregating calculation in advance, reduce downstream computational workload
2. Clustering data according to partition, reduce memory pressure caused by opening multiple writers downstream
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/iceberg/src/main/java/org/apache/inlong/sort/iceberg/sink/IcebergMiniBatchGroupOperator.java