[GitHub] [incubator-iotdb] Alima777 commented on a change in pull request #1345: [IOTDB-759] Refactor MNode by removing InternalMNode

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Alima777 commented on a change in pull request #1345:
URL: https://github.com/apache/incubator-iotdb/pull/1345#discussion_r438858487



##########
File path: server/src/main/java/org/apache/iotdb/db/metadata/mnode/MNode.java
##########
@@ -44,49 +57,100 @@
    */
   protected String fullPath;
 
+  Map<String, MNode> children;
+  Map<String, MNode> aliasChildren;
+
+  protected ReadWriteLock lock = new ReentrantReadWriteLock();
 
   /**
    * Constructor of MNode.
    */
   public MNode(MNode parent, String name) {
     this.parent = parent;
     this.name = name;
+    this.children = new LinkedHashMap<>();
   }
 
   /**
    * check whether the MNode has a child with the name
    */
-  public abstract boolean hasChild(String name);
+  public boolean hasChild(String name) {
+    return this.children.containsKey(name) ||
+        (aliasChildren != null && aliasChildren.containsKey(name));
+  }
 
   /**
    * node key, name or alias
    */
-  public abstract void addChild(String name, MNode child);
+  public void addChild(String name, MNode child) {
+    children.put(name, child);
+  }
 
   /**
-   * delete a child
+   * If delete a leafMNode, lock its parent, if delete an InternalNode, lock itself
    */
-  public abstract void deleteChild(String name) throws DeleteFailedException;
+  public void deleteChild(String name) throws DeleteFailedException {
+    if (children.containsKey(name)) {
+      Lock writeLock;
+      // if its child node is leaf node, we need to acquire the write lock of the current device node
+      if (children.get(name) instanceof MeasurementMNode) {
+        writeLock = lock.writeLock();
+      } else {
+        // otherwise, we only need to acquire the write lock of its child node.
+        writeLock = (children.get(name)).lock.writeLock();
+      }

Review comment:
       I'm not sure about this. Whether should we change the lock logic of this method? As the measurementNode maybe internalNode now.




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