public long getPinnedMemorySize() {
    return pinnedMemorySize.get();
  }
This class is used to record statistics within a SchemaRegion in PBTree mode, which is a superset
of the statistics in Memory mode.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/rescon/CachedSchemaRegionStatistics.java