[GitHub] [kafka] satishd commented on a change in pull request #10848: MINOR Updated transaction index as optional in LogSegmentData.

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satishd commented on a change in pull request #10848:
URL: https://github.com/apache/kafka/pull/10848#discussion_r648768897



##########
File path: storage/api/src/main/java/org/apache/kafka/server/log/remote/storage/LogSegmentData.java
##########
@@ -33,31 +34,32 @@
     private final Path logSegment;
     private final Path offsetIndex;
     private final Path timeIndex;
-    private final Path txnIndex;
+    private final Optional<Path> transactionIndex;
     private final Path producerSnapshotIndex;
     private final ByteBuffer leaderEpochIndex;
 
     /**
      * Creates a LogSegmentData instance with data and indexes.
-     *  @param logSegment            actual log segment file
+     *
+     * @param logSegment            actual log segment file
      * @param offsetIndex           offset index file
      * @param timeIndex             time index file
-     * @param txnIndex              transaction index file
+     * @param transactionIndex      transaction index file, which can be null
      * @param producerSnapshotIndex producer snapshot until this segment
      * @param leaderEpochIndex      leader-epoch-index until this segment
      */
     public LogSegmentData(Path logSegment,
                           Path offsetIndex,
                           Path timeIndex,
-                          Path txnIndex,
+                          Path transactionIndex,

Review comment:
       Passing `Optional` as arguments is not considered as a good practice. We still need to do null check for that Optional instance. 
   [SO answer from Brian Goetz](https://stackoverflow.com/questions/26327957/should-java-8-getters-return-optional-type/26328555#26328555) mentioned the right usage of `Optional`. I have also update PR not to use it as a field.
   
   ```
   You should almost never use it as a field of something or a method parameter.
   ```
   
   [Javadoc of Optional ](https://docs.oracle.com/javase/10/docs/api/java/util/Optional.html)suggests returning as an argument mentioned below.
   ```
   API Note:
   Optional is primarily intended for use as a method return type where there is a clear need to represent "no result," and where using null is likely to cause errors. A variable whose type is Optional should never itself be null; it should always point to an Optional instance.
   ```
   
   I do not have strong opinions on this, I am fine with the conventions that we are following in this project if we have any on `Optional` usage. 




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