@Override
  public TimeValuePair currentTimeValuePair() throws IOException {
    if (!hasCachedTimeValuePair) {
      cachedTimeValuePair = timeValuePairIterator.nextTimeValuePair();
      hasCachedTimeValuePair = true;
    }
    return cachedTimeValuePair;
  }
To read chunk data in memory.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/read/reader/chunk/MemChunkReader.java