Fix PBTree schema cache release after pre-delete (#17834)

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

@@ -230,6 +230,7 @@ public List<Integer> getRegionsToFlush(long windowsEndTime) {
   public void forceFlushAndRelease() {
     boolean needFlush;
     while (true) {
+      waitUntilWorkerTasksDone();
       needFlush = false;
       for (CachedMTreeStore store : regionToStoreMap.values()) {
         if (store.getMemoryManager().getBufferNodeNum() > 0) {
@@ -239,13 +240,29 @@ public void forceFlushAndRelease() {
       }
       if (needFlush) {
         scheduler.scheduleFlushAll().join();
+        waitUntilWorkerTasksDone();
         scheduler.scheduleRelease(true);
       } else {
+        // No volatile nodes left, but clean unpinned cache may still remain after previous flushes.
+        scheduler.scheduleRelease(true);
+        waitUntilWorkerTasksDone();
         break;
       }
     }
   }
 
+  @TestOnly
+  private void waitUntilWorkerTasksDone() {
+    while (scheduler.getActiveWorkerNum() > 0 || !flushingRegionSet.isEmpty()) {
+      try {
+        Thread.sleep(10);
+      } catch (InterruptedException e) {
+        Thread.currentThread().interrupt();
+        return;
+      }
+    }
+  }
+
   public void clear() {
     if (releaseMonitor != null) {
       releaseMonitor.shutdownNow();

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/traverser/Traverser.java

@@ -185,6 +185,7 @@ private N getChild(N parent, String childName, boolean skipTemplateChildren)
           && skipPreDeletedSchema
           && child.isMeasurement()
           && child.getAsMeasurementMNode().isPreDeleted()) {
+        releaseNode(child);
         child = null;
       }
     }

iotdb-core/datanode/src/test/java/org/apache/iotdb/db/metadata/schemaRegion/SchemaStatisticsTest.java

@@ -75,24 +75,12 @@ public void testPBTreeMemoryStatistics() throws Exception {
         || testParams.getTestModeName().equals("PBTree-NonMemory")) {
       final IMNodeFactory<ICachedMNode> nodeFactory =
           MNodeFactoryLoader.getInstance().getCachedMNodeIMNodeFactory();
-      // wait release and flush task
-      Thread.sleep(6000);
+      ReleaseFlushMonitor.getInstance().forceFlushAndRelease();
       // schemaRegion1
       final IMNode<ICachedMNode> sg1 = nodeFactory.createDatabaseMNode(null, "sg1");
       sg1.setFullPath("root.sg1");
       final long size1 = sg1.estimateSize();
-      if (size1 != schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage()) {
-        // There are two possibilities here in PartialMemory mode:
-        // 1. only the "sg1" node remains
-        // 2. the "sg1" node and the "n" node remain
-        Assert.assertEquals("PBTree-PartialMemory", testParams.getTestModeName());
-        Assert.assertEquals(
-            size1 + nodeFactory.createDeviceMNode(sg1.getAsMNode(), "n").estimateSize(),
-            schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage());
-        ReleaseFlushMonitor.getInstance().forceFlushAndRelease();
-        Assert.assertEquals(
-            size1, schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage());
-      }
+      Assert.assertEquals(size1, schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage());
     }
     Assert.assertEquals(0, schemaRegion1.getSchemaRegionStatistics().getSchemaRegionId());
     checkPBTreeStatistics(engineStatistics);
@@ -122,8 +110,7 @@ public void testMemoryStatistics2() throws Exception {
 
       final IMNodeFactory<?> nodeFactory =
           MNodeFactoryLoader.getInstance().getCachedMNodeIMNodeFactory();
-      // wait release and flush task
-      Thread.sleep(1000);
+      ReleaseFlushMonitor.getInstance().forceFlushAndRelease();
       // schemaRegion1
       final IMNode<?> sg1 = nodeFactory.createDatabaseMNode(null, "sg1");
       sg1.setFullPath("root.sg1");
@@ -231,36 +218,12 @@ public void testMemoryStatistics() throws Exception {
         || testParams.getTestModeName().equals("PBTree-NonMemory")) {
       final IMNodeFactory<ICachedMNode> nodeFactory =
           MNodeFactoryLoader.getInstance().getCachedMNodeIMNodeFactory();
-      // wait release and flush task
-      Thread.sleep(1000);
+      ReleaseFlushMonitor.getInstance().forceFlushAndRelease();
       // schemaRegion1
       final IMNode<ICachedMNode> sg1 = nodeFactory.createDatabaseDeviceMNode(null, "sg1");
       sg1.setFullPath("root.sg1");
       final long size1 = sg1.estimateSize();
-      if (sg1.estimateSize() != schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage()) {
-        // "d0" or "d1" node may remain in PartialMemory mode
-        Assert.assertEquals("PBTree-PartialMemory", testParams.getTestModeName());
-        final long d0ExistSize =
-            size1
-                + nodeFactory
-                    .createMeasurementMNode(
-                        sg1.getAsDeviceMNode(),
-                        "d0",
-                        new MeasurementSchema(
-                            "d0", TSDataType.INT64, TSEncoding.PLAIN, CompressionType.SNAPPY),
-                        null)
-                    .estimateSize();
-        final long d1ExistSize =
-            size1 + nodeFactory.createInternalMNode(sg1.getAsMNode(), "d1").estimateSize();
-        Assert.assertTrue(
-            d0ExistSize == schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage()
-                || d1ExistSize == schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage());
-        ReleaseFlushMonitor.getInstance().forceFlushAndRelease();
-        // wait release and flush task
-        Thread.sleep(1000);
-        Assert.assertEquals(
-            size1, schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage());
-      }
+      Assert.assertEquals(size1, schemaRegion1.getSchemaRegionStatistics().getRegionMemoryUsage());
       // schemaRegion2
       final IMNode<?> sg2 = nodeFactory.createDatabaseMNode(null, "sg2");
       sg2.setFullPath("root.sg2");
@@ -420,7 +383,11 @@ public void testPBTreeNodeStatistics() throws Exception {
       schemaRegion1.deleteTimeseriesInBlackList(patternTree);
       schemaRegion2.deleteTimeseriesInBlackList(patternTree);
 
-      Thread.sleep(1000);
+      if (testParams.getCachedMNodeSize() <= 3) {
+        ReleaseFlushMonitor.getInstance().forceFlushAndRelease();
+      } else {
+        Thread.sleep(1000);
+      }
       final CachedSchemaRegionStatistics cachedRegionStatistics1 =
           schemaRegion1.getSchemaRegionStatistics().getAsCachedSchemaRegionStatistics();
       final CachedSchemaRegionStatistics cachedRegionStatistics2 =
@@ -433,13 +400,7 @@ public void testPBTreeNodeStatistics() throws Exception {
         Assert.assertEquals(4, cachedRegionStatistics2.getUnpinnedMNodeNum());
       } else {
         Assert.assertEquals(1, cachedRegionStatistics1.getPinnedMNodeNum());
-        if (0 != cachedRegionStatistics1.getUnpinnedMNodeNum()) {
-          // "d0" may remain in PartialMemory mode
-          Assert.assertEquals("PBTree-PartialMemory", testParams.getTestModeName());
-          ReleaseFlushMonitor.getInstance().forceFlushAndRelease();
-          Thread.sleep(1000);
-          Assert.assertEquals(0, cachedRegionStatistics1.getUnpinnedMNodeNum());
-        }
+        Assert.assertEquals(0, cachedRegionStatistics1.getUnpinnedMNodeNum());
         Assert.assertEquals(1, cachedRegionStatistics2.getPinnedMNodeNum());
         Assert.assertEquals(0, cachedRegionStatistics2.getUnpinnedMNodeNum());
       }