checking the OperatorStateMetadata log for the state schema file

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/IncrementalExecution.scala

@@ -214,6 +214,7 @@ class IncrementalExecution(
             val metadata = stateStoreWriter.operatorStateMetadata()
             stateStoreWriter match {
               case tws: TransformWithStateExec =>
+                logError(s"### checkpointLocation: $checkpointLocation")
                 val metadataPath = OperatorStateMetadataV2.metadataFilePath(new Path(
                   checkpointLocation, tws.getStateInfo.operatorId.toString))
                 val operatorStateMetadataLog = new OperatorStateMetadataLog(sparkSession,

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/OperatorStateMetadataLog.scala

@@ -51,6 +51,8 @@ class OperatorStateMetadataLog(
       case 1 =>
         OperatorStateMetadataV1.serialize(fsDataOutputStream, metadata)
       case 2 =>
+        logError(s"### stateSchemaPath: ${metadata.asInstanceOf[OperatorStateMetadataV2].
+          stateStoreInfo.head.stateSchemaFilePath}")
         OperatorStateMetadataV2.serialize(fsDataOutputStream, metadata)
     }
   }

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/TransformWithStateExec.scala

@@ -380,19 +380,37 @@ case class TransformWithStateExec(
     )
   }
 
+  private def fetchOperatorStateMetadataLog(
+      hadoopConf: Configuration,
+      checkpointDir: String,
+      operatorId: Long): OperatorStateMetadataLog = {
+    val checkpointPath = new Path(checkpointDir, operatorId.toString)
+    val operatorStateMetadataPath = OperatorStateMetadataV2.metadataFilePath(checkpointPath)
+    new OperatorStateMetadataLog(hadoopConf, operatorStateMetadataPath.toString)
+  }
+
   override def validateAndMaybeEvolveStateSchema(
       hadoopConf: Configuration,
       batchId: Long,
       stateSchemaVersion: Int): Array[String] = {
     assert(stateSchemaVersion >= 3)
-    val newColumnFamilySchemas = getColFamilySchemas()
+    val newSchemas = getColFamilySchemas()
     val schemaFile = new StateSchemaV3File(
       hadoopConf, stateSchemaDirPath(StateStoreId.DEFAULT_STORE_NAME).toString)
     // TODO: Read the schema path from the OperatorStateMetadata file
     // and validate it with the new schema
 
+    val operatorStateMetadataLog = fetchOperatorStateMetadataLog(
+      hadoopConf, getStateInfo.checkpointLocation, getStateInfo.operatorId)
+    val mostRecentLog = operatorStateMetadataLog.getLatest()
+    val oldSchemas = mostRecentLog.map(_._2.asInstanceOf[OperatorStateMetadataV2])
+      .map(_.stateStoreInfo.map(_.stateSchemaFilePath)).getOrElse(Array.empty)
+      .flatMap { schemaPath =>
+        schemaFile.getWithPath(new Path(schemaPath))
+      }.toList
+    validateSchemas(oldSchemas, newSchemas)
     // Write the new schema to the schema file
-    val schemaPath = schemaFile.addWithUUID(batchId, newColumnFamilySchemas.values.toList)
+    val schemaPath = schemaFile.addWithUUID(batchId, newSchemas.values.toList)
     Array(schemaPath.toString)
   }