Add a plan version field to QueryRequest Protobuf Message

pinot-common/src/main/proto/worker.proto

@@ -40,6 +40,7 @@ message CancelResponse {
 message QueryRequest {
   repeated StagePlan stagePlan = 1;
   bytes metadata = 2; // Serialized Properties
+  int32 version = 3;
 }
 
 // QueryResponse is the dispatched response from worker, it doesn't contain actual data, only dispatch status.

pinot-query-runtime/src/main/java/org/apache/pinot/query/service/dispatch/QueryDispatcher.java

@@ -151,6 +151,7 @@ void submit(long requestId, DispatchableSubPlan dispatchableSubPlan, long timeou
       _executorService.submit(() -> {
         try {
           Worker.QueryRequest.Builder requestBuilder = Worker.QueryRequest.newBuilder();
+          requestBuilder.setVersion(CommonConstants.MultiStageQueryRunner.PlanVersions.V1);
           for (int i = 0; i < numStages; i++) {
             int stageId = i + 1;
             DispatchablePlanFragment stagePlan = stagePlans.get(stageId);

pinot-spi/src/main/java/org/apache/pinot/spi/utils/CommonConstants.java

@@ -1145,6 +1145,13 @@ public enum JoinOverFlowMode {
     public enum WindowOverFlowMode {
       THROW, BREAK
     }
+
+    /**
+     * Constants related to plan versions.
+     */
+    public static class PlanVersions {
+      public static final int V1 = 1;
+    }
   }
 
   public static class NullValuePlaceHolder {