Added flags to mark whether a device has device descendants to optimize query like select xx from xxx.**

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/mem/MTreeBelowSGMemoryImpl.java

@@ -207,6 +207,43 @@
     }
   }
 
+  private IDeviceMNode<IMemMNode> setToEntityAndUpdateFlags(final IMemMNode node) {
+    final boolean wasDevice = node.isDevice();
+    final IDeviceMNode<IMemMNode> deviceMNode = store.setToEntity(node);
+    if (!wasDevice) {
+      markAncestorsHavingDeviceDescendant(node);
+    }
+    return deviceMNode;
+  }
+
+  private void markAncestorsHavingDeviceDescendant(final IMemMNode deviceNode) {
+    IMemMNode current = deviceNode.getParent();
+    while (current != null && !current.hasDeviceDescendant()) {
+      current.setHasDeviceDescendant(true);
+      current = current.getParent();
+    }
+  }
+
+  private boolean hasDeviceDescendantInChildren(final IMemMNode node) {
+    try (final IMNodeIterator<IMemMNode> iterator = store.getChildrenIterator(node)) {
+      while (iterator.hasNext()) {
+        final IMemMNode child = iterator.next();
+        if (child.isDevice() || child.hasDeviceDescendant()) {
+          return true;
+        }
+      }
+      return false;
+    }
+  }
+
+  private void refreshAncestorsHavingDeviceDescendant(IMemMNode startNode) {
+    IMemMNode current = startNode;
+    while (current != null) {
+      current.setHasDeviceDescendant(hasDeviceDescendantInChildren(current));
+      current = current.getParent();
+    }
+  }
+
   private long getTemplateMeasurementCount(final int templateId) {
     final Template template = ClusterTemplateManager.getInstance().getTemplate(templateId);
     return template == null ? 0L : template.getMeasurementNumber();
@@ -315,7 +352,7 @@
       if (device.isDevice()) {
         entityMNode = device.getAsDeviceMNode();
       } else {
-        entityMNode = store.setToEntity(device);
+        entityMNode = setToEntityAndUpdateFlags(device);
       }
 
       // create a non-aligned time series
@@ -353,7 +390,7 @@
    * @param compressors compressor
    */
   public List<IMeasurementMNode<IMemMNode>> createAlignedTimeSeries(
       final PartialPath devicePath,
       final List<String> measurements,
       final List<TSDataType> dataTypes,
       final List<TSEncoding> encodings,
@@ -409,7 +446,7 @@
       if (device.isDevice()) {
         entityMNode = device.getAsDeviceMNode();
       } else {
-        entityMNode = store.setToEntity(device);
+        entityMNode = setToEntityAndUpdateFlags(device);
         entityMNode.setAligned(true);
       }
 
@@ -657,14 +694,15 @@
       boolean hasMeasurement = false;
       boolean hasNonViewMeasurement = false;
       IMemMNode child;
-      IMNodeIterator<IMemMNode> iterator = store.getChildrenIterator(curNode);
-      while (iterator.hasNext()) {
-        child = iterator.next();
-        if (child.isMeasurement()) {
-          hasMeasurement = true;
-          if (!child.getAsMeasurementMNode().isLogicalView()) {
-            hasNonViewMeasurement = true;
-            break;
+      try (final IMNodeIterator<IMemMNode> iterator = store.getChildrenIterator(curNode)) {
+        while (iterator.hasNext()) {
+          child = iterator.next();
+          if (child.isMeasurement()) {
+            hasMeasurement = true;
+            if (!child.getAsMeasurementMNode().isLogicalView()) {
+              hasNonViewMeasurement = true;
+              break;
+            }
           }
         }
       }
@@ -673,6 +711,7 @@
         synchronized (this) {
           curNode = store.setToInternal(entityMNode);
         }
+        refreshAncestorsHavingDeviceDescendant(curNode.getParent());
       } else if (!hasNonViewMeasurement) {
         // has some measurement but they are all logical view
         entityMNode.setAligned(null);
@@ -1033,7 +1072,7 @@
       if (cur.isDevice()) {
         entityMNode = cur.getAsDeviceMNode();
       } else {
-        entityMNode = store.setToEntity(cur);
+        entityMNode = setToEntityAndUpdateFlags(cur);
       }
     }
 
@@ -1141,7 +1180,7 @@
     if (cur.isDevice()) {
       entityMNode = cur.getAsDeviceMNode();
     } else {
-      entityMNode = store.setToEntity(cur);
+      entityMNode = setToEntityAndUpdateFlags(cur);
     }
 
     if (!entityMNode.isAligned()) {
@@ -1196,14 +1235,21 @@
 
   private long rebuildSubtreeMeasurementCountFromNode(final IMemMNode node) {
     long count = node.isMeasurement() ? 1L : 0L;
-    final IMNodeIterator<IMemMNode> iterator = store.getChildrenIterator(node);
-    while (iterator.hasNext()) {
-      count += rebuildSubtreeMeasurementCountFromNode(iterator.next());
+    boolean hasDeviceDescendant = false;
+    try (final IMNodeIterator<IMemMNode> iterator = store.getChildrenIterator(node)) {
+      while (iterator.hasNext()) {
+        final IMemMNode child = iterator.next();
+        count += rebuildSubtreeMeasurementCountFromNode(child);
+        if (child.isDevice() || child.hasDeviceDescendant()) {
+          hasDeviceDescendant = true;
+        }
+      }
     }
     if (node.isDevice() && node.getAsDeviceMNode().isUseTemplate()) {
       count += getTemplateMeasurementCount(node.getAsDeviceMNode().getSchemaTemplateId());
     }
     node.setSubtreeMeasurementCount(count);
+    node.setHasDeviceDescendant(hasDeviceDescendant);
     return count;
   }
 
@@ -1786,7 +1832,7 @@
       if (device.isDevice()) {
         entityMNode = device.getAsDeviceMNode();
       } else {
-        entityMNode = store.setToEntity(device);
+        entityMNode = setToEntityAndUpdateFlags(device);
         // this parent has no measurement before. The leafName is his first child who is a logical
         // view.
         entityMNode.setAligned(null);
@@ -1923,7 +1969,7 @@
             (TableDeviceInfo<IMemMNode>) entityMNode.getDeviceInfo();
         attributeUpdater.accept(deviceInfo.getAttributePointer());
       } else {
-        entityMNode = store.setToEntity(cur);
+        entityMNode = setToEntityAndUpdateFlags(cur);
         final TableDeviceInfo<IMemMNode> deviceInfo = new TableDeviceInfo<>();
         deviceInfo.setAttributePointer(attributePointerGetter.getAsInt());
         entityMNode.getAsInternalMNode().setDeviceInfo(deviceInfo);
@@ -2040,6 +2086,7 @@
       collector.traverse();
     }
     databaseMNode.deleteChild(tableName);
+    refreshAncestorsHavingDeviceDescendant(databaseMNode);
     regionStatistics.resetTableDevice(tableName);
     store.releaseMemory(memoryReleased.get());
     return true;

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/mem/mnode/IMemMNode.java

@@ -19,14 +19,33 @@
 package org.apache.iotdb.db.schemaengine.schemaregion.mtree.impl.mem.mnode;
 
 import org.apache.iotdb.commons.schema.node.IMNode;
+import org.apache.iotdb.db.schemaengine.schemaregion.mtree.impl.mem.mnode.basic.BasicMNode;
 
 public interface IMemMNode extends IMNode<IMemMNode> {
 
+  BasicMNode getBasicMNode();
+
   /**
    * The count of measurement nodes contained in the subtree rooted at this node. The counter is
    * maintained in memory only.
    */
-  long getSubtreeMeasurementCount();
+  default long getSubtreeMeasurementCount() {
+    return getBasicMNode().getSubtreeMeasurementCount();
+  }
+
+  default void setSubtreeMeasurementCount(final long subtreeMeasurementCount) {
+    getBasicMNode().setSubtreeMeasurementCount(subtreeMeasurementCount);
+  }
+
+  /**
+   * Whether there is any device node in the subtree rooted at this node, excluding the node itself.
+   * This flag is maintained in memory only.
+   */
+  default boolean hasDeviceDescendant() {
+    return getBasicMNode().hasDeviceDescendant();
+  }
 
-  void setSubtreeMeasurementCount(long subtreeMeasurementCount);
+  default void setHasDeviceDescendant(final boolean hasDeviceDescendant) {
+    getBasicMNode().setHasDeviceDescendant(hasDeviceDescendant);
+  }
 }

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/mem/mnode/basic/BasicMNode.java

@@ -49,6 +49,9 @@ public class BasicMNode implements IMemMNode {
   /** Cached count of measurements in this node's subtree, rebuilt on restart. */
   private long subtreeMeasurementCount = 0L;
 
+  /** Cached flag showing whether there is any device in the subtree below this node. */
+  private boolean hasDeviceDescendant = false;
+
   /** from root to this node, only be set when used once for InternalMNode */
   private String fullPath;
 
@@ -58,6 +61,11 @@ public BasicMNode(IMemMNode parent, String name) {
     this.basicMNodeInfo = new BasicMNodeInfo(name);
   }
 
+  @Override
+  public BasicMNode getBasicMNode() {
+    return this;
+  }
+
   @Override
   public String getName() {
     return basicMNodeInfo.getName();
@@ -112,6 +120,16 @@ public void setSubtreeMeasurementCount(final long subtreeMeasurementCount) {
     this.subtreeMeasurementCount = subtreeMeasurementCount;
   }
 
+  @Override
+  public boolean hasDeviceDescendant() {
+    return hasDeviceDescendant;
+  }
+
+  @Override
+  public void setHasDeviceDescendant(final boolean hasDeviceDescendant) {
+    this.hasDeviceDescendant = hasDeviceDescendant;
+  }
+
   @Override
   public PartialPath getPartialPath() {
     final List<String> detachedPath = new ArrayList<>();
@@ -239,6 +257,7 @@ public <R, C> R accept(final MNodeVisitor<R, C> visitor, final C context) {
    *         <li>parent reference, 8B
    *         <li>fullPath reference, 8B
    *         <li>subtreeMeasurementCount, 8B
+   *         <li>hasDeviceDescendant, 1B
    *       </ol>
    *   <li>MapEntry in parent
    *       <ol>
@@ -250,7 +269,7 @@ public <R, C> R accept(final MNodeVisitor<R, C> visitor, final C context) {
    */
   @Override
   public int estimateSize() {
-    return 8 + 8 + 8 + 8 + 8 + 8 + 8 + 28 + basicMNodeInfo.estimateSize();
+    return 8 + 8 + 8 + 8 + 8 + 1 + 8 + 8 + 28 + basicMNodeInfo.estimateSize();
   }
 
   @Override

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/mem/mnode/impl/AboveDatabaseMNode.java

@@ -33,14 +33,4 @@ public AboveDatabaseMNode(IMemMNode parent, String name) {
   public IMemMNode getAsMNode() {
     return this;
   }
-
-  @Override
-  public long getSubtreeMeasurementCount() {
-    return basicMNode.getSubtreeMeasurementCount();
-  }
-
-  @Override
-  public void setSubtreeMeasurementCount(long subtreeMeasurementCount) {
-    basicMNode.setSubtreeMeasurementCount(subtreeMeasurementCount);
-  }
 }

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/mem/mnode/impl/DatabaseMNode.java

@@ -45,14 +45,4 @@ public IDeviceInfo<IMemMNode> getDeviceInfo() {
   public void setDeviceInfo(IDeviceInfo<IMemMNode> deviceInfo) {
     basicMNode.setDeviceInfo(deviceInfo);
   }
-
-  @Override
-  public long getSubtreeMeasurementCount() {
-    return basicMNode.getSubtreeMeasurementCount();
-  }
-
-  @Override
-  public void setSubtreeMeasurementCount(long subtreeMeasurementCount) {
-    basicMNode.setSubtreeMeasurementCount(subtreeMeasurementCount);
-  }
 }

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/mem/mnode/impl/MeasurementMNode.java

@@ -52,14 +52,4 @@ public IMNodeContainer<IMemMNode> getChildren() {
   public final boolean isLogicalView() {
     return false;
   }
-
-  @Override
-  public long getSubtreeMeasurementCount() {
-    return basicMNode.getSubtreeMeasurementCount();
-  }
-
-  @Override
-  public void setSubtreeMeasurementCount(long subtreeMeasurementCount) {
-    basicMNode.setSubtreeMeasurementCount(subtreeMeasurementCount);
-  }
 }