[Fix-17831] Fix incorrect parallelism num when complement data in parallel excution mode (#17853)

Author: SbloodyS

dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/executor/workflow/BackfillWorkflowExecutorDelegate.java

@@ -35,6 +35,7 @@
 import org.apache.dolphinscheduler.service.process.ProcessService;
 
 import java.time.ZonedDateTime;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -95,9 +96,9 @@ private List<Integer> doParallelBackfillWorkflow(final BackfillWorkflowDTO backf
             expectedParallelismNumber = listDate.size();
         }
 
-        log.info("In parallel mode, current expectedParallelismNumber:{}", expectedParallelismNumber);
+        log.info("In parallel mode, current expectedParallelismNumber: {}", expectedParallelismNumber);
         final List<Integer> workflowInstanceIdList = Lists.newArrayList();
-        for (List<ZonedDateTime> stringDate : Lists.partition(listDate, expectedParallelismNumber)) {
+        for (List<ZonedDateTime> stringDate : splitDateTime(listDate, expectedParallelismNumber)) {
             final Integer workflowInstanceId = doBackfillWorkflow(
                     backfillWorkflowDTO,
                     stringDate.stream().map(DateUtils::dateToString).collect(Collectors.toList()));
@@ -106,6 +107,30 @@ private List<Integer> doParallelBackfillWorkflow(final BackfillWorkflowDTO backf
         return workflowInstanceIdList;
     }
 
+    /**
+     * split date time list into n parts, the last part may be larger if not divisible
+     */
+    private List<List<ZonedDateTime>> splitDateTime(List<ZonedDateTime> dateTimeList, int numParts) {
+        List<List<ZonedDateTime>> result = new ArrayList<>();
+        int n = dateTimeList.size();
+
+        int baseSize = n / numParts;
+        int remainder = n % numParts;
+
+        int start = 0;
+        for (int i = 0; i < numParts; i++) {
+            int currentSize = baseSize;
+            if (i == numParts - 1) {
+                currentSize += remainder;
+            }
+            List<ZonedDateTime> part = dateTimeList.subList(start, start + currentSize);
+            result.add(part);
+            start += currentSize;
+        }
+
+        return result;
+    }
+
     private Integer doBackfillWorkflow(final BackfillWorkflowDTO backfillWorkflowDTO,
                                        final List<String> backfillTimeList) {
         final Server masterServer = registryClient.getRandomServer(RegistryNodeType.MASTER).orElse(null);