@Override
  public boolean isExceedReleaseThreshold() {
    return engineStatistics.getMemoryUsage() > releaseThreshold;
  }
Threshold strategy based on the number of nodes.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/memcontrol/ReleaseFlushStrategySizeBasedImpl.java