python3 dynamoDB Update_item不起作用

Question

我只是在AWS dynamoDB中練習使用示例代碼但是，更新代碼不能用於錯誤

botocore.exceptions.ClientError: An error occurred (ValidationException) when calling the UpdateItem operation: The document path provided in the update expression is invalid for update

我的python代碼在這里。 我可以在沒有'map'屬性的情況下更新DB。

table = dynamodb.Table('Movies')

title = "The Big New Movie"
year = 2015

response = table.update_item(
    Key={
        "year": year,
        "title": title
    },
    UpdateExpression="set #attrName.rating = :r, #attrName.plot=:p",
    ExpressionAttributeNames = {
        "#attrName" : "info"
    },
    ExpressionAttributeValues={
        ':r': decimal.Decimal(5.5),
        ':p': "Everything happens all at once."
    },
    ReturnValues="UPDATED_NEW"
)

Answer 1

發生這種情況是因為您正在嘗試更新頂級屬性info嵌套屬性，該屬性尚不存在（或者不是地圖類型 ）

因此，在運行此更新之前，您必須確保頂級屬性info已存在。

或者，如果拋出異常，您可以捕獲異常，並執行創建info屬性的另一個更新，如下所示：

from botocore.exceptions import ClientError

table = dynamodb.Table('Movies')

title = "The Big New Movie"
year = 2015

try:
    # Adding new nested attributes `rating` and `plot` 
    # if the top field `info` already exists and is a map
    response = table.update_item(
        Key={
            "year": year,
            "title": title
        },
        UpdateExpression="set #attrName.rating = :r, #attrName.plot=:p",
        ExpressionAttributeNames = {
            "#attrName" : "info"
        },
        ExpressionAttributeValues={
            ':r': decimal.Decimal(5.5),
            ':p': "Everything happens all at once."
        },
        ReturnValues="UPDATED_NEW"
    )

except ClientError as e:
    if e.response['Error']['Code'] == 'ValidationException':
      # Creating new top level attribute `info` (with nested props) 
      # if the previous query failed
      response = table.update_item(
          Key={
              "year": year,
              "title": title
          },
          UpdateExpression="set #attrName = :attrValue",
          ExpressionAttributeNames = {
              "#attrName" : "info"
          },
          ExpressionAttributeValues={
              ':attrValue': {
                  'rating': decimal.Decimal(5.5),
                  'plot': "Everything happens all at once."
              }
          },
          ReturnValues="UPDATED_NEW"
      )
    else:
      raise