使用 Python 更新 DynamoDB 表中的 JSON 记录

Question

I have a JSON record which looks like:

 {'ip_address': data['src_ip'],
  'first_seen': data['timestamp'],
  'last_seen': data['timestamp']
                        }

The record gets stored in DynamoDB table with ip_address as the primary key.

When the same IP appears again, I want to update the last seen value. I created a function with below lines:

def update_db(json_result):
    ddb_data = json.loads(json.dumps(json_result), parse_float=Decimal)
    database = boto3.resource('dynamodb', endpoint_url="https://dynamodb.us-west-2.amazonaws.com")
    table = database.Table('IPData')
    print("adding :", json_result)
    #db_add = table.put_item(Item = ddb_data)
    response = table.update_item(
                        Key = {
                            'ip_address': json_result['ip_address'] 
                        },
                        UpdateExpression="SET 'last_seen' = :s",
                        ExpressionAttributeValues = {
                                        ':s': json_result['last_seen']
                        },
                        ReturnValues="UPDATED_NEW"
                    )
    return response

This results into an error as:

{
  "errorMessage": "An error occurred (ValidationException) when calling the UpdateItem operation: Invalid UpdateExpression: Syntax error; token: \"'\", near: \"SET 'last_seen\"",
  "errorType": "ClientError",

Not sure what is wrong in my syntax here. Can someone help me fix the issue.

Answer 1

See the doc for update expressions and a boto3 example here .

Your UpdateExpression should probably be (no single-quotes):

                        UpdateExpression="SET last_seen = :s",