public int getReferenceCount() {
    return referenceCount.get();
  }
Unpin the wal if it is out of time to live.

@return true if the wal is unpinned physically (then it can be invalidated), false otherwise
@throws PipeRuntimeNonCriticalException if failed to unpin WAL of memtable.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/resource/wal/PipeWALResource.java