DynamoDb putItem ConditionExpression in c++ - add or update - c++

Question

My putItem is working. Now I want to make sure I update only newer information to an existing item, or add this as a new item:
ConditionlExpression:
Create new item if partition:sort doesn't exist
Update if attribute generated < :newTimestamp
So I added one line to code:
putItemRequest.SetConditionExpression(" attribute_not_exists(" + partitionName + ") OR (attribute_exists(" + partitionName + ") AND (" + timestampName + " < :" + timestamp + "))");
This should create a new item, but it looks to be trying to evaluate the attribute 'generated' when it does not exist for a new item.
The error on putItem return:
Invalid ConditionExpression: An expression attribute value used in expression is not defined; attribute value: :1461782160
From the debugger the conditionExpression look like:
m_conditionExpression = " attribute_not_exists(airport) OR (attribute_exists(airport) AND (generated < :1461782160))"
I am trying to avoid:
looking up the partition:sort
if it does not exist, putItem
else check the generated attribute
then if generated < newTimestamp update the item
Is there a way to construct the conditionExpression to meet my expectation?
Edit: Same problem when using updateItem
Code:
UpdateItemRequest updateItemRequest;
updateItemRequest.WithTableName(dynamoDbTableName);
AttributeValue hashPartition;
hashPartition.SetS(partition);
updateItemRequest.AddKey(partitionName, hashPartition);
AttributeValue hashSort;
hashSort.SetS(sort);
updateItemRequest.AddKey(sortName, hashSort);
AttributeValue hashAttribute;
hashAttribute.SetS(attribute);
Aws::Map<Aws::String, AttributeValue> attributeMap;
attributeMap[":a"] = hashAttribute;
updateItemRequest.SetUpdateExpression("SET " + timestampName + " = :" + timestamp + ", " + attributeName + " = :a");
updateItemRequest.SetExpressionAttributeValues(attributeMap);
// Allow only older items to be updated
updateItemRequest.SetConditionExpression("(" + timestampName + " < :" + timestamp + ")");
auto updateItemOutcome = dynamoDbClient.UpdateItem(updateItemRequest);
Error:
Invalid UpdateExpression: An expression attribute value used in expression is not defined; attribute value: :1461781980
That attribute value is the timestamp. It's not defined because this item doesn't exist and should be created.
Here is my current work around:
ClientConfiguration config;
config.region = Aws::Region::US_WEST_2;
Aws::DynamoDB::DynamoDBClient dynamoDbClient(config);
Aws::Map<Aws::String, AttributeValue> aMap;
PutItemRequest putItemRequest;
putItemRequest.WithTableName(dynamoDbTableName);
AttributeValue hashPartition;
hashPartition.SetS(partition);
putItemRequest.AddItem(partitionName, hashPartition);
aMap[":p"] = hashPartition;
AttributeValue hashSort;
hashSort.SetS(sort);
putItemRequest.AddItem(sortName, hashSort);
aMap[":s"] = hashSort;
AttributeValue hashTimestamp;
hashTimestamp.SetN(timestamp);
putItemRequest.AddItem(timestampName, hashTimestamp);
AttributeValue hashAttribute;
hashAttribute.SetS(attribute);
putItemRequest.AddItem(attributeName, hashAttribute);
// Do not update existing items
putItemRequest.SetConditionExpression("NOT((" + partitionName + " = :p) AND (" + sortName + " = :s))");
putItemRequest.SetExpressionAttributeValues(aMap);
auto putItemOutcome = dynamoDbClient.PutItem(putItemRequest);
if(putItemOutcome.IsSuccess())
{
poco_information(logger, "writeDb PutItem Success: " + partition + ":" + sort);
status = SWIMPROCESSOR_OK;
}
else
{
if(putItemOutcome.GetError().GetErrorType() == DynamoDBErrors::CONDITIONAL_CHECK_FAILED) {
// item exists, try to update
Aws::Map<Aws::String, AttributeValue> uMap;
uMap[":t"] = hashTimestamp;
uMap[":a"] = hashAttribute;
UpdateItemRequest updateItemRequest;
updateItemRequest.WithTableName(dynamoDbTableName);
updateItemRequest.AddKey(partitionName, hashPartition);
updateItemRequest.AddKey(sortName, hashSort);
updateItemRequest.SetUpdateExpression("SET " + timestampName + " = :t, " + attributeName + " = :a");
updateItemRequest.SetExpressionAttributeValues(uMap);
// Allow only older items to be updated
updateItemRequest.SetConditionExpression(timestampName + " < :t");
auto updateItemOutcome = dynamoDbClient.UpdateItem(updateItemRequest);
if(updateItemOutcome.IsSuccess())
{
poco_information(logger, "writeDb UpdateItem Success: " + partition + ":" + sort);
status = SWIMPROCESSOR_OK;
}
else
{
if(putItemOutcome.GetError().GetErrorType() == DynamoDBErrors::CONDITIONAL_CHECK_FAILED) {
poco_information(logger, "writeDB UpdateItem new timestamp is older then current timestamp");
status = SWIMPROCESSOR_OK;
} else {
std::string msg(updateItemOutcome.GetError().GetMessage());
poco_error(logger, "writeDb UpdateItem Failure: " + msg);
status = SWIMPROCESSOR_DBWRITEERROR;
}
}
} else {
std::string msg(putItemOutcome.GetError().GetMessage());
poco_error(logger, "writeDb PutItem Failure: " + msg);
status = SWIMPROCESSOR_DBWRITEERROR;
}
}

Answer 1

The service's error message says that you need to put :1461782160 in the attributeMap. UpdateExpression should be "SET " + timestampName + " = :timestamp, " + attributeName + " = :a"
and your map should be defined as follows.
AttributeValue hashAttributeA;
hashAttributeA.SetS(attribute)
AttributeValue hashAttributeTimestamp;
hashAttributeTimestamp.SetN(timestamp)
Aws::Map<Aws::String, AttributeValue> attributeMap;
attributeMap[":a"] = hashAttributeA;
attributeMap[":timestamp"] = hashAttributeTimestamp;