Exclude backfill start date for versioning in join jobs

api/src/main/scala/ai/chronon/api/Extensions.scala

@@ -907,20 +907,28 @@ object Extensions {
       join
     }
 
-    /*
-     * Compute variants of semantic_hash with different flags. A flag is stored on Hive metadata and used to
-     * indicate which version of semantic_hash logic to use.
-     */
-    def semanticHash(excludeTopic: Boolean): Map[String, String] = {
+    /**
+      * Compute variants of semantic_hash with different flags. A flag is stored on Hive metadata and used to
+      * indicate which version of semantic_hash logic to use.
+      * @param excludeTopic exclude streaming topic for any potential streaming topic migrations
+      * @param excludeBackfillStartDateInJoinPart exclude the backfill start date in the join part, it is intended to
+      *                                           trigger separate group by backfill jobs, and semantic hash is only
+      *                                           used in join for versioning check, therefore, exclude it for more
+      *                                           flexibility of group by backfill jobs
+      */
+    def semanticHash(excludeTopic: Boolean, excludeBackfillStartDateInJoinPart: Boolean = true): Map[String, String] = {
+      // WARN: deepCopy doesn't guarantee same semantic_hash will be produced due to reordering of map keys
+      // but the behavior is deterministic
+      val joinCopy = if (excludeTopic || excludeBackfillStartDateInJoinPart) join.deepCopy() else join
+
       if (excludeTopic) {
-        // WARN: deepCopy doesn't guarantee same semantic_hash will be produced due to reordering of map keys
-        // but the behavior is deterministic
-        val joinCopy = join.deepCopy()
         cleanTopic(joinCopy)
-        joinCopy.baseSemanticHash
-      } else {
-        baseSemanticHash
       }
+
+      if (excludeBackfillStartDateInJoinPart) {
+        joinCopy.getJoinParts.toScala.foreach(_.groupBy.unsetBackfillStartDate())
+      }
+      joinCopy.baseSemanticHash
     }
 
     /*