private boolean doUnPin(ICachedMNode node) {
    CacheEntry cacheEntry = getCacheEntry(node);

    boolean isPinStatusChanged = false;
    synchronized (cacheEntry) {
      cacheEntry.unPin();
      if (!cacheEntry.isPinned()) {
        isPinStatusChanged = true;
        memoryStatistics.releasePinnedMemResource(node);
      }
    }

    if (isPinStatusChanged && !node.isDatabase()) {
      doUnPin(node.getParent());
    }

    return isPinStatusChanged;
  }
Unpin a node, and if the lock mayer on this node is zero, it will be evictable. Unpin a node
means decrease one mayer lock from the node. If the lock mayer reaches zero, the mayer lock of
its parent should decrease.

@param node
@return
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/memory/MemoryManager.java