[FIX-14299][api]: check schedule exists (#14430)

* fix: check schedule exists

* put error message in result

---------

Co-authored-by: lutong <lutongtong211027@credithc.com>

dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/service/impl/SchedulerServiceImpl.java

@@ -167,6 +167,15 @@ public class SchedulerServiceImpl extends BaseServiceImpl implements SchedulerSe
         executorService.checkProcessDefinitionValid(projectCode, processDefinition, processDefineCode,
                 processDefinition.getVersion());
 
+        Schedule scheduleExists =
+                scheduleMapper.queryByProcessDefinitionCode(processDefineCode);
+        if (scheduleExists != null) {
+            log.error("Schedule already exist, scheduleId:{},processDefineCode:{}", scheduleExists.getId(),
+                    processDefineCode);
+            putMsg(result, Status.SCHEDULE_ALREADY_EXISTS, processDefineCode, scheduleExists.getId());
+            return result;
+        }
+
         Schedule scheduleObj = new Schedule();
         Date now = new Date();