DynamoDB: ConditionalCheckFailedException

Question

I am dealing with a ConditionalCheckFailedException and I am not exactly sure which condition is failing the check. When I open up debugger and examine the exception variable, I can't find any useful info.

Below is my Java Dynamo Client code. I am trying to make a conditional write to DynamoDB using DynamoDBSaveExpression when:

The client date in the table comes before the current client date that I am trying to write (stored as EPOCH time) An entry does not exist in the table (I check for the FEEDBACK_KEY as it is the primary key in my table) When I write the first entry into the table, it works, but on updates when an entry exists, I get the ConditionalCheckFailedException exception. Any ideas?

final DynamoDBSaveExpression expression = new DynamoDBSaveExpression();

final Map<String, ExpectedAttributeValue> expectedAttributes =
        ImmutableMap.<String, ExpectedAttributeValue>builder()
            .put(ThemesMessageEligibility.TableKeys.CLIENT_DATE,
                    new ExpectedAttributeValue()
                        .withComparisonOperator(ComparisonOperator.LT)
                        .withValue(new AttributeValue().withN(clientDate)))
            .put(ThemesMessageEligibility.TableKeys.FEEDBACK_KEY,
                    new ExpectedAttributeValue(false))
            .build();

expression.setExpected(expectedAttributes);
expression.setConditionalOperator(ConditionalOperator.OR);

// Conditional write if the clientDate is after the dynamo's client Date
try {
    dynamoMapper.save(themesFeedbackComponentContainer, expression);
} catch (ConditionalCheckFailedException ex) {
   ...
}

Alexander Patrikalakis Alexander Patrikalakis · Accepted Answer · 2017-02-12T11:58:39

I would remove the second condition, or change it so that it conditions on the item existing (new ExpectedAttributeValue(true)). UpdateItem will just overwrite the existing item even if it exists, so it seems like the CLIENT_DATE condition is the only one you need.

The API call as written above will only succeed on the first write (that is, when the item does not exist). In retrospect, if you only want the first write to an item to succeed (and fail if the item already exists) the CLIENT_DATE condition is not necessary (as there are no attributes in the existing image to compare to).

DynamoDB: ConditionalCheckFailedException

1 Answers