@Override
    public boolean isFinished() {
        return currentStreamSplit == null || !streamFetchTask.isRunning();
    }
Fetcher to fetch data from table split, the split is the stream split {@link StreamSplit}.
Copy from com.ververica:flink-cdc-base:2.3.0.
inlong-sort/sort-flink/cdc-base/src/main/java/org/apache/inlong/sort/cdc/base/source/reader/external/IncrementalSourceStreamFetcher.java