adding scaladoc

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

@@ -273,11 +273,16 @@ class StateStoreColumnFamilySchemaUtils(initializeAvroSerde: Boolean)
       ))
   }
 
-  // This function creates the StateStoreColFamilySchema for
-  // Timers' secondary index.
-  // Because we want to encode fixed-length types as binary types
-  // if we are using Avro, we need to do some schema conversion to ensure
-  // we can use range scan
+  /** Creates a StateStoreColFamilySchema for Timers' secondary index with proper encoding configuration.
+   *
+   * When using Avro encoding, fixed-length types need to be converted to binary types to support range scan operations.
+   * This function handles the necessary schema conversion to ensure range scan functionality works correctly.
+   *
+   * @param stateName The name of the state store
+   * @param keySchema The schema defining the structure of the key
+   * @param valSchema The schema defining the structure of the value
+   * @return A StateStoreColFamilySchema configured for Timer secondary indexing with appropriate encoding
+   */
   def getTimerStateSchemaForSecIndex(
       stateName: String,
       keySchema: StructType,
@@ -290,7 +295,7 @@ class StateStoreColumnFamilySchemaUtils(initializeAvroSerde: Boolean)
       valSchema,
       Some(RangeKeyScanStateEncoderSpec(keySchema, Seq(0))),
       avroEnc = getAvroSerde(
-        StructType(avroKeySchema.drop(2)),
+        StructType(avroKeySchema.drop(numRemainingKeyFieldsForTtlRangeScan)),
         valSchema
       ))
   }