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 +207,46 @@
     }
   }
 
+  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) {
+    final IMNodeIterator<IMemMNode> iterator = store.getChildrenIterator(node);
+    try {
+      while (iterator.hasNext()) {
+        final IMemMNode child = iterator.next();
+        if (child.isDevice() || child.hasDeviceDescendant()) {
+          return true;
+        }
+      }
+      return false;
+    } finally {
+      iterator.close();
+    }
+  }
+
+  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 +355,7 @@
       if (device.isDevice()) {
         entityMNode = device.getAsDeviceMNode();
       } else {
-        entityMNode = store.setToEntity(device);
+        entityMNode = setToEntityAndUpdateFlags(device);
       }
 
       // create a non-aligned time series
@@ -352,7 +392,7 @@
    * @param encodings encodings list
    * @param compressors compressor
    */
   public List<IMeasurementMNode<IMemMNode>> createAlignedTimeSeries(
       final PartialPath devicePath,
       final List<String> measurements,
       final List<TSDataType> dataTypes,
@@ -409,7 +449,7 @@
       if (device.isDevice()) {
         entityMNode = device.getAsDeviceMNode();
       } else {
-        entityMNode = store.setToEntity(device);
+        entityMNode = setToEntityAndUpdateFlags(device);
         entityMNode.setAligned(true);
       }
 
@@ -673,6 +713,7 @@
         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 +1074,7 @@
       if (cur.isDevice()) {
         entityMNode = cur.getAsDeviceMNode();
       } else {
-        entityMNode = store.setToEntity(cur);
+        entityMNode = setToEntityAndUpdateFlags(cur);
       }
     }
 
@@ -1141,7 +1182,7 @@
     if (cur.isDevice()) {
       entityMNode = cur.getAsDeviceMNode();
     } else {
-      entityMNode = store.setToEntity(cur);
+      entityMNode = setToEntityAndUpdateFlags(cur);
     }
 
     if (!entityMNode.isAligned()) {
@@ -1196,14 +1237,24 @@
 
   private long rebuildSubtreeMeasurementCountFromNode(final IMemMNode node) {
     long count = node.isMeasurement() ? 1L : 0L;
+    boolean hasDeviceDescendant = false;
     final IMNodeIterator<IMemMNode> iterator = store.getChildrenIterator(node);
-    while (iterator.hasNext()) {
-      count += rebuildSubtreeMeasurementCountFromNode(iterator.next());
+    try {
+      while (iterator.hasNext()) {
+        final IMemMNode child = iterator.next();
+        count += rebuildSubtreeMeasurementCountFromNode(child);
+        if (child.isDevice() || child.hasDeviceDescendant()) {
+          hasDeviceDescendant = true;
+        }
+      }
+    } finally {
+      iterator.close();
     }
     if (node.isDevice() && node.getAsDeviceMNode().isUseTemplate()) {
       count += getTemplateMeasurementCount(node.getAsDeviceMNode().getSchemaTemplateId());
     }
     node.setSubtreeMeasurementCount(count);
+    node.setHasDeviceDescendant(hasDeviceDescendant);
     return count;
   }
 
@@ -1786,7 +1837,7 @@
       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 +1974,7 @@
             (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 +2091,7 @@
       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

@@ -29,4 +29,12 @@ public interface IMemMNode extends IMNode<IMemMNode> {
   long getSubtreeMeasurementCount();
 
   void setSubtreeMeasurementCount(long 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.
+   */
+  boolean hasDeviceDescendant();
+
+  void setHasDeviceDescendant(boolean 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;
 
@@ -112,6 +115,16 @@ 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 +252,7 @@ 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 +264,7 @@ 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

@@ -43,4 +43,14 @@ public long getSubtreeMeasurementCount() {
   public void setSubtreeMeasurementCount(long subtreeMeasurementCount) {
     basicMNode.setSubtreeMeasurementCount(subtreeMeasurementCount);
   }
+
+  @Override
+  public boolean hasDeviceDescendant() {
+    return basicMNode.hasDeviceDescendant();
+  }
+
+  @Override
+  public void setHasDeviceDescendant(final boolean hasDeviceDescendant) {
+    basicMNode.setHasDeviceDescendant(hasDeviceDescendant);
+  }
 }

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

@@ -55,4 +55,14 @@ public long getSubtreeMeasurementCount() {
   public void setSubtreeMeasurementCount(long subtreeMeasurementCount) {
     basicMNode.setSubtreeMeasurementCount(subtreeMeasurementCount);
   }
+
+  @Override
+  public boolean hasDeviceDescendant() {
+    return basicMNode.hasDeviceDescendant();
+  }
+
+  @Override
+  public void setHasDeviceDescendant(final boolean hasDeviceDescendant) {
+    basicMNode.setHasDeviceDescendant(hasDeviceDescendant);
+  }
 }

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

@@ -62,4 +62,14 @@ public long getSubtreeMeasurementCount() {
   public void setSubtreeMeasurementCount(long subtreeMeasurementCount) {
     basicMNode.setSubtreeMeasurementCount(subtreeMeasurementCount);
   }
+
+  @Override
+  public boolean hasDeviceDescendant() {
+    return basicMNode.hasDeviceDescendant();
+  }
+
+  @Override
+  public void setHasDeviceDescendant(final boolean hasDeviceDescendant) {
+    basicMNode.setHasDeviceDescendant(hasDeviceDescendant);
+  }
 }

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

@@ -137,6 +137,71 @@
   private final int levelOfDB;
   private final CachedSchemaRegionStatistics regionStatistics;
 
+  private IDeviceMNode<ICachedMNode> setToEntityAndUpdateFlags(final ICachedMNode node)
+      throws MetadataException {
+    final boolean wasDevice = node.isDevice();
+    if (!node.isDeviceDescendantComputed()) {
+      node.setHasDeviceDescendant(hasDeviceDescendantInChildren(node));
+      node.setDeviceDescendantComputed(true);
+    }
+    final IDeviceMNode<ICachedMNode> deviceMNode = store.setToEntity(node);
+    if (!wasDevice) {
+      markAncestorsHavingDeviceDescendant(node);
+    }
+    return deviceMNode;
+  }
+
+  private void markAncestorsHavingDeviceDescendant(final ICachedMNode deviceNode) {
+    ICachedMNode current = deviceNode.getParent();
+    while (current != null && !current.hasDeviceDescendant()) {
+      current.setHasDeviceDescendant(true);
+      current.setDeviceDescendantComputed(true);
+      current = current.getParent();
+    }
+  }
+
+  private boolean hasDeviceDescendantInChildren(final ICachedMNode node) throws MetadataException {
+    final IMNodeIterator<ICachedMNode> iterator = store.getChildrenIterator(node);
+    try {
+      while (iterator.hasNext()) {
+        final ICachedMNode child = iterator.next();
+        try {
+          if (child.isDevice() || hasDeviceDescendant(child)) {
+            return true;
+          }
+        } finally {
+          unPinMNode(child);
+        }
+      }
+      return false;
+    } finally {
+      iterator.close();
+    }
+  }
+
+  private boolean hasDeviceDescendant(final ICachedMNode node) throws MetadataException {
+    if (node.isMeasurement()) {
+      node.setHasDeviceDescendant(false);
+      node.setDeviceDescendantComputed(true);
+      return false;
+    }
+    if (!node.isDeviceDescendantComputed()) {
+      node.setHasDeviceDescendant(hasDeviceDescendantInChildren(node));
+      node.setDeviceDescendantComputed(true);
+    }
+    return node.hasDeviceDescendant();
+  }
+
+  private void refreshAncestorsHavingDeviceDescendant(ICachedMNode startNode)
+      throws MetadataException {
+    ICachedMNode current = startNode;
+    while (current != null) {
+      current.setHasDeviceDescendant(hasDeviceDescendantInChildren(current));
+      current.setDeviceDescendantComputed(true);
+      current = current.getParent();
+    }
+  }
+
   // region MTree initialization, clear and serialization
   public MTreeBelowSGCachedImpl(
       PartialPath storageGroupPath,
@@ -291,7 +356,7 @@
    * @param props props
    * @param alias alias of measurement
    */
   public IMeasurementMNode<ICachedMNode> createTimeSeriesWithPinnedReturn(
       final PartialPath path,
       final TSDataType dataType,
       final TSEncoding encoding,
@@ -353,7 +418,7 @@
           if (device.isDevice()) {
             entityMNode = device.getAsDeviceMNode();
           } else {
-            entityMNode = store.setToEntity(device);
+            entityMNode = setToEntityAndUpdateFlags(device);
             device = entityMNode.getAsMNode();
           }
 
@@ -395,7 +460,7 @@
    * @param encodings encodings list
    * @param compressors compressor
    */
   public List<IMeasurementMNode<ICachedMNode>> createAlignedTimeSeries(
       final PartialPath devicePath,
       final List<String> measurements,
       final List<TSDataType> dataTypes,
@@ -458,7 +523,7 @@
           if (device.isDevice()) {
             entityMNode = device.getAsDeviceMNode();
           } else {
-            entityMNode = store.setToEntity(device);
+            entityMNode = setToEntityAndUpdateFlags(device);
             entityMNode.setAligned(true);
             device = entityMNode.getAsMNode();
           }
@@ -703,6 +768,7 @@
 
         if (!hasMeasurement) {
           curNode = store.setToInternal(entityMNode);
+          refreshAncestorsHavingDeviceDescendant(curNode.getParent());
         } else if (!hasNonViewMeasurement) {
           // has some measurement but they are all logical view
           store.updateMNode(entityMNode.getAsMNode(), o -> o.getAsDeviceMNode().setAligned(null));
@@ -1075,7 +1141,7 @@
           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.
@@ -1197,7 +1263,7 @@
         if (cur.isDevice()) {
           entityMNode = cur.getAsDeviceMNode();
         } else {
-          entityMNode = store.setToEntity(cur);
+          entityMNode = setToEntityAndUpdateFlags(cur);
         }
 
         if (entityMNode.isUseTemplate()) {
@@ -1243,7 +1309,7 @@
       if (cur.isDevice()) {
         entityMNode = cur.getAsDeviceMNode();
       } else {
-        entityMNode = store.setToEntity(cur);
+        entityMNode = setToEntityAndUpdateFlags(cur);
       }
 
       store.updateMNode(

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

@@ -24,6 +24,14 @@
 import org.apache.iotdb.db.schemaengine.schemaregion.mtree.impl.pbtree.memory.cache.CacheEntry;
 
 public interface ICachedMNode extends IMNode<ICachedMNode> {
+  boolean hasDeviceDescendant();
+
+  void setHasDeviceDescendant(boolean hasDeviceDescendant);
+
+  boolean isDeviceDescendantComputed();
+
+  void setDeviceDescendantComputed(boolean deviceDescendantComputed);
+
   CacheEntry getCacheEntry();
 
   void setCacheEntry(CacheEntry cacheEntry);