[GitHub] [iotdb] WilliamSong11 commented on a change in pull request #2732: [ISSUE-2493] show child nodes path

[GitBox <gi...@apache.org>]

WilliamSong11 commented on a change in pull request #2732:
URL: https://github.com/apache/iotdb/pull/2732#discussion_r582504539



##########
File path: server/src/main/java/org/apache/iotdb/db/metadata/MTree.java
##########
@@ -1170,6 +1170,76 @@ private void findChildNodePathInNextLevel(
     }
   }
 
+  /**
+   * Get child node in the next level of the given path.
+   *
+   * <p>e.g., MTree has [root.sg1.d1.s1, root.sg1.d1.s2, root.sg1.d2.s1] given path = root.sg1,
+   * return [d1, d2]
+   *
+   * <p>e.g., MTree has [root.sg1.d1.s1, root.sg1.d1.s2, root.sg1.d2.s1] given path = root.sg1.d1
+   * return [s1, s2]
+   *
+   * @return All child nodes' seriesPath(s) of given seriesPath.
+   */
+  Set<String> getChildNodeInNextLevel(PartialPath path) throws MetadataException {
+    String[] nodes = path.getNodes();
+    if (nodes.length == 0 || !nodes[0].equals(root.getName())) {
+      throw new IllegalPathException(path.getFullPath());
+    }
+    Set<String> childNodes = new TreeSet<>();
+    findChildNodeInNextLevel(root, nodes, 1, "", childNodes, nodes.length + 1);
+    return childNodes;
+  }
+
+  /**
+   * Traverse the MTree to match all child node path in next level
+   *
+   * @param node the current traversing node
+   * @param nodes split the prefix path with '.'
+   * @param idx the current index of array nodes
+   * @param parent store the node string having traversed
+   * @param res store all matched device names
+   * @param length expected length of path
+   */
+  @SuppressWarnings("squid:S3776") // Suppress high Cognitive Complexity warning
+  private void findChildNodeInNextLevel(
+      MNode node, String[] nodes, int idx, String parent, Set<String> res, int length) {
+    if (node == null) {
+      return;
+    }
+    String nodeReg = MetaUtils.getNodeRegByIdx(idx, nodes);
+    if (!nodeReg.contains(PATH_WILDCARD)) {
+      if (idx == length) {
+        res.add(node.getName());
+      } else {
+        findChildNodeInNextLevel(
+            node.getChild(nodeReg),
+            nodes,
+            idx + 1,
+            parent + node.getName() + PATH_SEPARATOR,
+            res,
+            length);
+      }
+    } else {
+      if (node.getChildren().size() > 0) {
+        for (MNode child : node.getChildren().values()) {
+          if (!Pattern.matches(nodeReg.replace("*", ".*"), child.getName())) {
+            continue;
+          }
+          if (idx == length) {
+            res.add(node.getName());
+          } else {
+            findChildNodeInNextLevel(
+                child, nodes, idx + 1, parent + node.getName() + PATH_SEPARATOR, res, length);
+          }
+        }
+      } else if (idx == length) {
+        String nodeName = node.getName();
+        res.add(nodeName);
+      }

Review comment:
       Thank you for your reply 
   
   
    &ensp;I've run some local tests and the results seem to be in line with expectations
   
   &ensp;&ensp;1、Local client testing
   IoTDB> SET STORAGE GROUP TO root.gsxgt
   SET STORAGE GROUP TO root.gsxgt
   Msg: The statement is executed successfully.
   IoTDB> show child nodes root.gsxgt
   show child nodes root.gsxgt
   +-----------+
   |child nodes|
   +-----------+
   +-----------+
   Empty set.
   It costs 0.005s
   IoTDB> CREATE TIMESERIES root.gsxgt.d1 WITH DATATYPE=BOOLEAN, ENCODING=PLAIN
   CREATE TIMESERIES root.gsxgt.d1 WITH DATATYPE=BOOLEAN, ENCODING=PLAIN
   Msg: The statement is executed successfully.
   IoTDB> show child nodes root.gsxgt
   show child nodes root.gsxgt
   +-----------+
   |child nodes|
   +-----------+
   |         d1|
   +-----------+
   Total line number = 1
   It costs 0.009s
   IoTDB> show child nodes root.gsxgt.d1
   show child nodes root.gsxgt.d1
   +-----------+
   |child nodes|
   +-----------+
   +-----------+
   Empty set.
   It costs 0.004s
   IoTDB> CREATE TIMESERIES root.gsxgt.d1.s1 WITH DATATYPE=BOOLEAN, ENCODING=PLAIN
   CREATE TIMESERIES root.gsxgt.d1.s1 WITH DATATYPE=BOOLEAN, ENCODING=PLAIN
   Msg: The statement is executed successfully.
   IoTDB> show child nodes root.gsxgt.d1
   show child nodes root.gsxgt.d1
   +-----------+
   |child nodes|
   +-----------+
   |         s1|
   +-----------+
   Total line number = 1
   It costs 0.005s
   
   
   &ensp;&ensp;2、org.apache.iotdb.db.metadata.MTreeTest --> Add Child Node as an empty scene 
   ![image](https://user-images.githubusercontent.com/13831999/109099027-52d09f80-775d-11eb-85f0-e3745ae9abf5.png)
   




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