DynamoDBMapper ConditionalCheckFailedException when range-key attribute for GSI is not present in update request - amazon-web-services

Question

I'm trying to reason about the cause of a ConditionalCheckFailedException I receive when using DynamoDBMapper with a specific save expression and with UPDATE_SKIP_NULL_ATTRIBUTES SaveBehavior.
My schema is as follows:
Member.java
#Data
#DynamoDBTable(tableName = "members")
public class Member implements DDBTable {
private static final String GROUP_GSI_NAME = "group-gsi";
#DynamoDBHashKey
#DynamoDBAutoGeneratedKey
private String memberId;
#DynamoDBVersionAttribute
private Long version;
#DynamoDBIndexHashKey(globalSecondaryIndexName = GROUP_GSI_NAME)
private String groupId;
#DynamoDBAutoGeneratedTimestamp(strategy = DynamoDBAutoGenerateStrategy.CREATE)
#DynamoDBIndexRangeKey(globalSecondaryIndexName = GROUP_GSI_NAME)
private Date joinDate;
#DynamoDBAttribute
private String memberName;
#Override
#DynamoDBIgnore
public String getHashKeyColumnName() {
return "memberId";
}
#Override
#DynamoDBIgnore
public String getHashKeyColumnValue() {
return memberId;
}
}
I use the following class to create/update/get the records in the members table.
DDBModelDAO.java
public class DDBModelDAO<T extends DDBTable> {
private final Class<T> ddbTableClass;
private final AmazonDynamoDB amazonDynamoDB;
private final DynamoDBMapper dynamoDBMapper;
public DDBModelDAO(Class<T> ddbTableClass, AmazonDynamoDB amazonDynamoDB, DynamoDBMapper dynamoDBMapper) {
this.ddbTableClass = ddbTableClass;
this.amazonDynamoDB = amazonDynamoDB;
this.dynamoDBMapper = dynamoDBMapper;
}
public T loadEntry(final String hashKey) {
return dynamoDBMapper.load(ddbTableClass, hashKey);
}
public T createEntry(final T item) {
dynamoDBMapper.save(item, getSaveExpressionForCreate(item));
return item;
}
public T updateEntry(final T item) {
dynamoDBMapper.save(item, getSaveExpressionForUpdate(item),
DynamoDBMapperConfig.SaveBehavior.UPDATE_SKIP_NULL_ATTRIBUTES.config());
return item;
}
private DynamoDBSaveExpression getSaveExpressionForCreate(final T item) {
// No record with the same hash key must be present when creating
return new DynamoDBSaveExpression().withExpectedEntry(item.getHashKeyColumnName(),
new ExpectedAttributeValue(false));
}
private DynamoDBSaveExpression getSaveExpressionForUpdate(final T item) {
// The hash key for the record being updated must be present.
return new DynamoDBSaveExpression().withExpectedEntry(item.getHashKeyColumnName(),
new ExpectedAttributeValue(new AttributeValue(item.getHashKeyColumnValue()))
.withComparisonOperator(ComparisonOperator.EQ)
);
}
}
I wrote a test class to insert and update records into the members table, which is as follows:
public static void main(String[] args) {
DDBTestClient testClient = new DDBTestClient();
AmazonDynamoDB amazonDynamoDB = testClient.buildAmazonDynamoDB();
DynamoDBMapper dynamoDBMapper = testClient.buildDynamoDBMapper(amazonDynamoDB);
DDBModelDAO<Member> memberDAO = new DDBModelDAO<>(Member.class, amazonDynamoDB, dynamoDBMapper);
DDBModelDAO<Group> groupDAO = new DDBModelDAO<>(Group.class, amazonDynamoDB, dynamoDBMapper);
try {
// Create a group
Group groupToCreate = new Group();
groupToCreate.setGroupName("group-0");
Group createdGroup = groupDAO.createEntry(groupToCreate);
System.out.println("Created group: " + createdGroup);
Thread.sleep(3000);
// Create a member for the group
Member memberToCreate = new Member();
memberToCreate.setGroupId(createdGroup.getGroupId());
memberToCreate.setMemberName("member-0");
Member createdMember = memberDAO.createEntry(memberToCreate);
System.out.println("Created member: " + createdMember);
Thread.sleep(3000);
// Update member name
createdMember.setMemberName("member-updated-0");
createdMember.setGroupId(null);
//createdMember.setJoinDate(null); // <---- Causes ConditionalCheckFailedException
memberDAO.updateEntry(createdMember);
System.out.println("Updated member");
} catch (Exception exception) {
System.out.println(exception.getMessage());
}
}
As can be seen above, if I do not pass a valid value for joinDate(which happens to be the range-key for the groups GSI), in the updateEntry call, DynamoDB returns a ConditionalCheckFailedException. This is the case, even when I use a save behavior of UPDATE_SKIP_NULL_ATTRIBUTES, as can be seen in DDBModelDAO.java.
Can someone help me understand, why I'm required to send the range-key attribute for the GSI, for a conditional write to succeed?

Answer 1

Not sure if this answers your question:
Interface DynamoDBAutoGenerator:
"DynamoDBAutoGenerateStrategy.CREATE, instructs to generate when
creating the item. The mapper, determines an item is new, or
overwriting, if it's current value is null. There is a limitation when
performing partial updates using either,
DynamoDBMapperConfig.SaveBehavior.UPDATE_SKIP_NULL_ATTRIBUTES, or DynamoDBMapperConfig.SaveBehavior.APPEND_SET. A new value will only be generated if the mapper is also generating the key."
So the last part is important: "A new value will only be generated if the mapper is also generating the key"
That should explain why you only see the behavior that you are experiencing.
Does this make sense?