public FlinkSink.Builder appendMode(boolean appendMode) {
            this.appendMode = appendMode;
            return this;
        }
The appendMode properties is used to insert data without equality field columns.

@param appendMode append mode properties.
@return {@link FlinkSink.Builder} to connect the iceberg table.
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/iceberg/src/main/java/org/apache/inlong/sort/iceberg/sink/FlinkSink.java