DynamoDB Conditional SaveAsync
DynamoDB Conditional SaveAsync
提问于 2019-08-17 19:50:16
我使用了以下代码：
DynamoDBContextConfig config = new DynamoDBContextConfig()
{
ConsistentRead = false,
Conversion = DynamoDBEntryConversion.V2
};
using (DynamoDBContext context = new DynamoDBContext(config))
{
long unixTimestamp = (long)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds;
QTrackStatus qTrackStatus = new QTrackStatus()
{
Key = "m@m.com",
EventCode = "CC",
EventDateTime = "2019-09-09 14:00:30",
EventLocation = "BFS",
EventLastUpdate = unixTimestamp
};
DynamoDBOperationConfig dynamoDBOperationConfig = new DynamoDBOperationConfig()
{
QueryFilter = new List<ScanCondition>()
{
{ new ScanCondition("EventCode", ScanOperator.NotEqual, "CC") }
},
ConditionalOperator = ConditionalOperatorValues.And
};
await context.SaveAsync(qTrackStatus, dynamoDBOperationConfig);
}我要做的是只有在EventCode不是CC的情况下才保存记录。目前，它总是在保存。我可以首先检索记录，进行检查，然后在需要时调用SaveAsync -但是我希望在SaveAsync调用中完成所有这些工作。这个是可能的吗？
回答 1
Stack Overflow用户
发布于 2019-08-18 21:24:34
除非我遗漏了什么，否则使用更高级别的api看起来是不可能的。我最终重新分解成以下几个部分：
AmazonDynamoDBClient client = new AmazonDynamoDBClient();
UpdateItemRequest updateItemRequest = new UpdateItemRequest()
{
TableName = "QTrackStatus",
ReturnValues = ReturnValue.ALL_NEW,
ConditionExpression = "EventCode <> :ec",
UpdateExpression = "SET EventCode = :ec, EventDateTime = :edt, EventLocation = :el, EventLastUpdate = :elu",
ExpressionAttributeValues = new Dictionary<string, AttributeValue>()
{
{ ":ec", new AttributeValue("CC") },
{ ":edt", new AttributeValue("2019-09-09 14:00:30") },
{ ":el", new AttributeValue("BFS") },
{ ":elu", new AttributeValue() { N = ((long)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds).ToString() } }
},
Key = new Dictionary<string, AttributeValue>()
{
{ "Key", new AttributeValue("m@m.com") }
}
};
try
{
UpdateItemResponse updateItemResponse = await client.UpdateItemAsync(updateItemRequest);
}
catch(ConditionalCheckFailedException e)
{
}这让我可以实现我的目标。
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原文链接：
https://stackoverflow.com/questions/57536030
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