private void reportFinishedSnapshotSplitsIfNeed() {
        if (!finishedUnackedSplits.isEmpty()) {
            final Map<String, Offset> finishedOffsets = new HashMap<>();
            for (SnapshotSplit split : finishedUnackedSplits.values()) {
                finishedOffsets.put(split.splitId(), split.getHighWatermark());
            }
            FinishedSnapshotSplitsReportEvent reportEvent =
                    new FinishedSnapshotSplitsReportEvent(finishedOffsets);
            context.sendSourceEventToCoordinator(reportEvent);
            LOG.debug(
                    "The subtask {} reports offsets of finished snapshot splits {}.",
                    subtaskId,
                    finishedOffsets);
        }
    }
The multi-parallel source reader for table snapshot phase from {@link SnapshotSplit} and then
single-parallel source reader for table stream phase from {@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/IncrementalSourceReader.java