Optimistic Locking while using Enhanced DDB Client.

[RushinNaik]

Describe the issue

Need to upgrade SDK version to 2 for DDB client. I want to understand how to enforce optimistic locking while doing CRUD operation by enhanced DDB client. I am already using @DynamoDbVersionAttribute annotation.

Steps to Reproduce

1. Insert item using TransactWriteItemsEnhancedRequest - PutItem.
2. Fetch the item using table.getItem(GetItemEnhancedRequest). (recordVersion would be 1)
3. Update one field of item using TransactWriteItemsEnhancedRequest - UpdateItem. (recordVersion will updated to 2 in the DDB.)
4. Delete item using TransactWriteItemsEnhancedRequest - DeleteItem but use object fetched from Step 2 for deletion.

Current Behavior

Item is deleted successfully without any exception for record number mismatch.

Your Environment

• AWS Java SDK version used: 2
• JDK version used: 11
• Operating System and version: macOS 10.15.7

[debora-ito]

Hi @RushinNaik I'm able to reproduce it.

The optimistic locking works as expected for TransactWriteItemsEnhancedRequest putItem and updateItem, so this looks like a bug in deleteItem.

[RushinNaik]

Thanks @debora-ito for looking into it. Is there any workaround for this? or any timeline for the fix.

[debora-ito]

As a workaround, you can use the DeleteItemEnhancedRequest conditionExpression to define that the recordVersion value must be the same of the value fetched in step 2.

DeleteItemEnhancedRequest deleteItemRequest =
            DeleteItemEnhancedRequest.builder()
                                     .key(KEY)
                                     .conditionExpression(Expression.builder()
                                                                    .expression("recordVersion = :old_version_value")
                                                                    .putExpressionValue(":old_version_value", oldVersionAttributeValue)
                                                                    .build()).build();

If the condition is not met, the delete operation fails.

[RushinNaik]

This workaround solved the issue for me. Thanks. Also, I would recommend putting a note in the existing documentation for this scenario.

[The-Zona-Zoo]

Seems like if anything, this would be a bug in putItem not incrementing the java object's version once the item is successfully updated in the DB. That said, this could be expected behavior and not a bug. I.e. your code needs to make sure to increment the version upon a successful put/update.

[saikumarsuvanam]

Can we correct the documentation for deleteItem meanwhile before fixing this issue? https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.OptimisticLocking.html

[TheMarvelFan]

Hi is anyone working on this issue?