对非关键属性查询DynamoDB

问题描述

是否可以过滤使用非关键属性在AWS版本2 DynamoDB查询？亚马逊表示，他们可以做到这一点： http://amzn.to/1FVgQ9B 。但是，他们也给了API？我发现AWSDynamoDBQueryEx pression，但我认为这只是让过滤的范围键（没有足够的文档）。我正在寻找在iOS和AWS版本正确的API 2.感谢！

Is it possible to filter DynamoDB queries using non-key attributes in AWS version 2 ? Amazon says that they can do it: http://amzn.to/1FVgQ9B. But do they also give the API? I found AWSDynamoDBQueryExpression, but I think it only lets filtering on the range key (not enough documentation). I'm looking for the proper API in iOS and AWS version 2. Thanks!

推荐答案

我回答我自己的问题。这是我张贴在AWS支持论坛以及：

I'm answering my own question. This is what I posted on AWS support forum as well:

您无法与高层次的API做到这一点 - AWSDynamoDBObjectMapper。当使用AWSDynamoDBObjectMapper，您需要提供一个AWSDynamoDBQueryEx pression对象的查询方法来指定查询条件。 AWSDynamoDBQueryEx pression不给你在非关键属性设置过滤器（条件）的选项。我不知道这是为什么不支持！然而，AWSDynamoDBScanEx pression让你指定的非关键属性的条件，当您使用的扫描方法。但你不希望扫描当你真正的意思是查询。

You can't do this with the high level API -- AWSDynamoDBObjectMapper. When using AWSDynamoDBObjectMapper, you need to provide an AWSDynamoDBQueryExpression object to the query method to specify the query conditions. AWSDynamoDBQueryExpression doesn't give you the option to set filters(conditions) on non-key attributes. I wonder why this isn't supported! However, AWSDynamoDBScanExpression lets you specify conditions on non-key attributes when you use the scan method. But you don't want to scan when you actually mean a query.

幸运的是，你可以使用低级别的API直接调用查询AWSDynamoDB提供AWSDynamoDBQueryInput它可以让你指定了很多低级别的参数做到这一点。 AWSDynamoDBQueryInput让你指定使用任何queryFilter或filterEx pression非关键属性过滤条件。 queryFilter是德precated，建议使用filterEx pression。这里有两个文件，​​帮助我摸不着头脑：

Fortunately, you can do this using the low level API by directly calling query on AWSDynamoDB providing an AWSDynamoDBQueryInput which lets you specify a lot of low level parameters. AWSDynamoDBQueryInput lets you specify the filter conditions on non-key attributes using either queryFilter or filterExpression. queryFilter is deprecated, it's recommended to use filterExpression.Here are the two documents that helped me to figure this out:

http://docs.aws.amazon.com/amazondynamodb/最新/ APIReference / API_Query.html 的

下面是在一个迅速code例子。在这种code根据我过滤批准字段是一个非关键属性。 recId是主键：

Here's a code example in swift. In this code I'm filtering based on "approved" field that is a non-key attribute. recId is the primary key:

    func getApprovedRecords(recId: Int) {



     let dynamoDB = AWSDynamoDB.defaultDynamoDB()

        var startKey = nil

        var queryInput = AWSDynamoDBQueryInput()

        queryInput.tableName = TABLE_NAME

        queryInput.limit = QUERY_SIZE

        queryInput.exclusiveStartKey = startKey



        var recIdValue = AWSDynamoDBAttributeValue()

        recIdValue.N = String(recId)

        var recIdCondition = AWSDynamoDBCondition()

        recIdCondition.comparisonOperator = AWSDynamoDBComparisonOperator.EQ

        recIdCondition.attributeValueList = [recIdValue]



        queryInput.keyConditions = [ "recId"\" : recIdCondition]


        var oneValue = AWSDynamoDBAttributeValue()

        oneValue.N = "1"



        queryInput.expressionAttributeValues = [ ":one" : oneValue ]

        queryInput.filterExpression = "approved = :one"

        dynamoDB.query(queryInput).continueWithBlock { (task: BFTask!) -> AnyObject! in

            if ((task.error) != nil) {

                NSLog("The request failed. Error: \(task.error)")

            }

            if ((task.exception) != nil) {

                NSLog("The request failed. Exception: \(task.exception)")

            }

            if ((task.result) != nil) {

                NSLog("The request  succeeded.")

                let results = task.result as! AWSDynamoDBQueryOutput

                for r in results.items {

                    // do whatever with the result

                }

            }

            return nil

        }

    }

这篇关于对非关键属性查询DynamoDB的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！