jixuan1989 commented on a change in pull request #2828:
URL: https://github.com/apache/iotdb/pull/2828#discussion_r594068888
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File path: server/src/main/java/org/apache/iotdb/db/metadata/mnode/MNode.java
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@@ -102,6 +102,36 @@ public void addChild(String name, MNode child) {
children.putIfAbsent(name, child);
}
+ /**
+ * Add a child to the current mnode.
+ *
+ * <p>This method will not take the child's name as one of the inputs and
will also make this
+ * Mnode be child node's parent. All is to reduce the probability of
mistaken by users and be more
+ * convenient for users to use. And the return of this method is used to
conveniently construct a
+ * chain of time series for users.
+ *
+ * @param child child's node
+ * @return return the MNode already added
+ */
+ MNode addChild(MNode child) {
+ /* use cpu time to exchange memory
+ * measurementNode's children should be null to save memory
+ * add child method will only be called when writing MTree, which is not a
frequent operation
+ */
+ if (children == null) {
+ // double check, children is volatile
+ synchronized (this) {
+ if (children == null) {
+ children = new ConcurrentHashMap<>();
+ }
+ }
+ }
+
+ children.putIfAbsent(child.getName(), child);
+ child.parent = this;
Review comment:
Besides, if you set child.parent in this method, better to set its
parent before putting it in children map.
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