Fix npe in TopKOperator when topKResult is null.

integration-test/src/test/java/org/apache/iotdb/db/it/alignbydevice/IoTDBAlignByDeviceWithTemplateIT.java

@@ -577,6 +577,22 @@ public void templateInvalidTest() {
         "select count(s1+1) from root.sg1.** align by device;", expectedHeader, retArray);
   }
 
+  @Test
+  public void emptyResultTest() {
+    String[] expectedHeader = new String[] {"Time,Device,s3,s1,s2"};
+    String[] retArray = new String[] {};
+    resultSetEqualTest(
+        "SELECT * FROM root.sg1.** where time>=now()-1d and time<=now() "
+            + "ORDER BY TIME DESC ALIGN BY DEVICE;",
+        expectedHeader,
+        retArray);
+    resultSetEqualTest(
+        "SELECT * FROM root.sg2.** where time>=now()-1d and time<=now() "
+            + "ORDER BY TIME DESC ALIGN BY DEVICE;",
+        expectedHeader,
+        retArray);
+  }
+
   private static void insertData() {
     try (Connection connection = EnvFactory.getEnv().getConnection();
         Statement statement = connection.createStatement()) {

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/process/TopKOperator.java

@@ -80,6 +80,8 @@ public class TopKOperator implements ProcessOperator {
   // the data of every childOperator is in order
   private final boolean childrenDataInOrder;
 
+  public static int operatorBatchUpperBound = 100000;
+
   public TopKOperator(
       OperatorContext operatorContext,
       List<Operator> deviceOperators,
@@ -98,7 +100,10 @@ public TopKOperator(
 
     initResultTsBlock();
 
-    deviceBatchStep = 10000 % topValue == 0 ? 10000 / topValue : 10000 / topValue + 1;
+    deviceBatchStep =
+        operatorBatchUpperBound % topValue == 0
+            ? operatorBatchUpperBound / topValue
+            : operatorBatchUpperBound / topValue + 1;
     canCallNext = new boolean[deviceOperators.size()];
   }
 
@@ -137,7 +142,14 @@ public boolean isFinished() throws Exception {
 
   @Override
   public boolean hasNext() throws Exception {
-    return !(deviceIndex >= deviceOperators.size() && resultReturnSize >= topKResult.length);
+    if (deviceIndex >= deviceOperators.size()) {
+      if (topKResult == null) {
+        return false;
+      }
+
+      return resultReturnSize < topKResult.length;
+    }
+    return true;
   }
 
   @Override
@@ -289,10 +301,13 @@ private TsBlock getResultFromCachedTopKResult() {
     }
 
     tsBlockBuilder.reset();
+
+    if (topKResult == null || topKResult.length == 0) {
+      return tsBlockBuilder.build();
+    }
+
     ColumnBuilder[] valueColumnBuilders = tsBlockBuilder.getValueColumnBuilders();
-    for (int i = resultReturnSize, size = (topKResult == null ? 0 : topKResult.length);
-        i < size;
-        i++) {
+    for (int i = resultReturnSize; i < topKResult.length; i++) {
       MergeSortKey mergeSortKey = topKResult[i];
       TsBlock targetBlock = mergeSortKey.tsBlock;
       tsBlockBuilder

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/analyze/TemplatedAnalyze.java

@@ -171,6 +171,7 @@ public static boolean canBuildPlanUseTemplate(
     // generate result set header according to output expressions
     analyzeOutput(analysis, queryStatement, outputExpressions);
 
+    context.generateGlobalTimeFilter(analysis);
     // fetch partition information
     analyzeDataPartition(analysis, schemaTree, partitionFetcher, context.getGlobalTimeFilter());
     return true;