Python Boto3 查询 GSI 时的 DynamoDB Bug

Question

【以下的问题经过翻译处理】 假设在DynamoDB中有以下3行数据

| coin\_transaction\_id | coin\_amount | customer\_id | transaction\_time |
| --- | --- | --- | --- |
| 027072a5-fdf3-48ed-b36e-90a317d63c31 | 80 | bfbd221a-bc1f-4e96-943f-d809bb5e5af3 | 2022-06-15T18:52:40.044239+00:00 |
| f074d831-5791-4ba1-a596-ab114d14eaac | 40 | bfbd221a-bc1f-4e96-943f-d809bb5e5af3 | 2022-06-15T17:42:36.830859+00:00 |
| adafd372-03de-437a-887e-9027007517a2 | 160 | bfbd221a-bc1f-4e96-943f-d809bb5e5af3 | 2022-06-15T17:42:36.830859+00:00 |

GSI
分区键：customer_id
排序键：transaction_time

当使用以下代码在lambda中通过Python boto 3查询数据时，与行3相同的GSI的行2无法检索出来。结果返回仅可检索到行1和行3。

```
      coinResp = coinTable.query(
                IndexName = "customer_id-transaction_time-index",
                KeyConditionExpression = 'customer_id = :ci and transaction_time between :date1 and :date2',
                ExpressionAttributeValues = {
                    ':ci' : customerID,
                    ':date1' : startDate,
                    ':date2' : endDate,
                },
                Limit = 1,
                ExclusiveStartKey = receivedLastEvaluatedKey,
                ScanIndexForward = False,
            )

```

这是一个bug吗？

Answer

【以下的回答经过翻译处理】 您现在假设基表中的第二行将成为GSI中的第二行，但事实并非如此。基表中的项目按分区键分组并按排序键排序。而在GSI中，具有相同分区/排序键组合的多个项目可以具有多个项目，这意味着无法保证顺序。

至于您的问题，您在代码中将`LEK`设置为空字符串，导致您错过了响应中的最后一条记录。尝试以下代码片段：

```
import boto3

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('cust1')
customerID = 'bfbd221a-bc1f-4e96-943f-d809bb5e5af3'
startDate = '2022-06-14T17:42:36.830859+00:00'
endDate = '2022-06-16T18:52:40.044239+00:00'

def processItems(items):
    print(items)

kwargs = {
    'IndexName' : "my-index",
    'KeyConditionExpression' : 'customer_id = :ci and transaction_time between :date1 and :date2',
    'ExpressionAttributeValues' : {
        ':ci' : customerID,
        ':date1' : startDate,
        ':date2' : endDate,
    },
    'Limit' : 1,
    'ScanIndexForward' : False
}

while True:
    response = table.query( **kwargs )
    processItems( response[ u'Items' ] )
    if 'LastEvaluatedKey' in response:
        kwargs[ 'ExclusiveStartKey' ] = response[ 'LastEvaluatedKey' ]
    else:
        break

```

coin_transaction_id	coin_amount	customer_id	transaction_time
027072a5-fdf3-48ed-b36e-90a317d63c31	80	bfbd221a-bc1f-4e96-943f-d809bb5e5af3	2022-06-15T18:52:40.044239+00:00
f074d831-5791-4ba1-a596-ab114d14eaac	40	bfbd221a-bc1f-4e96-943f-d809bb5e5af3	2022-06-15T17:42:36.830859+00:00
adafd372-03de-437a-887e-9027007517a2	160	bfbd221a-bc1f-4e96-943f-d809bb5e5af3	2022-06-15T17:42:36.830859+00:00

Python Boto3 查询 GSI 时的 DynamoDB Bug

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