@Override
    public void open() throws Exception {
        super.open();
        LOG.info("Opening IcebergMiniBatchGroupOperator");
        this.collector = new StreamRecordCollector<>(output);
    }
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