[英]DynamoDB Query / Scan with combined conditions
我正面临一个体系结构问题(或合乎逻辑的问题),并且不确定最好的处理方法是什么。 我正在构建一个小型配对应用程序,以研究AWS Mobile HUB及其服务,并对它更加熟悉。
我的DynamoDB包含一个具有rendezvous
的表,该表具有以下2个属性(还有一些此处不重要的属性):
Rendezvous
- from_gender
- interest_gender
另外,我正在使用Cognito,并让我的用户拥有财产
User
- usr_gender
- interest_gender
基本上,我想匹配对from_gender
感兴趣且性别为interest_gender
目前, User
可以是male
或female
而interest_gender
可以是male
, female
或all
。
这意味着对于一个用户,我们有6种组合:
Gender -> Interested In
Male -> female
Female -> female
Female -> all
Male -> all
Male -> male
Female -> male
现在变得棘手:
例
用户A(对all
感兴趣的female
)正在寻找rendezvous
应该为她显示以下4种会合类型:
from_gender, interest_gender
male, female
male, all
female, female
female, all
这意味着我需要一个查询(dummycode):
rendevous.query(“
(from_gender =男性)AND((interest_gender =女性“)或(interest_gender =全部))OR
(from_gender =女性)AND((interest_gender =女性“)或(interest_gender =全部))
”)
然而
我还没有找到一种方法来处理查询或扫描,因为它们不支持对同一属性的OR查询。
我尝试创建indees(使用不同组合的代码,但没有找到为所有情况创建可查询索引的方法), 请注意 ,除此兴趣外,我还需要按年龄(最小/最大)排序和位置最小/最大纬度,最小/最大时长。
是否有使用DynamoDB的智能方法,还是我被迫走SQL路线?
这是我最近尝试过的查询表达式:Works
func generateScanExpression() -> AWSDynamoDBScanExpression {
let usr = UserHelper.sharedHelper.currentUser
let expression = AWSDynamoDBScanExpression()
expression.limit = 10
// Male interested in male
if (usr?.interest == Constants.CONST_MALE) && (usr?.gender == Constants.CONST_MALE){
expression.filterExpression = "details_fromGender = :fg AND ( match_interest = :ig OR match_interest = :all )"
expression.expressionAttributeValues = [":fg": Constants.CONST_MALE, ":ig": Constants.CONST_MALE, ":all": Constants.CONST_ALL ]
}
// Female interested in female
if (usr?.interest == Constants.CONST_FEMALE) && (usr?.gender == Constants.CONST_FEMALE){
expression.filterExpression = "details_fromGender = :fg AND ( match_interest = :ig OR match_interest = :all )"
expression.expressionAttributeValues = [":fg": Constants.CONST_FEMALE, ":ig": Constants.CONST_FEMALE, ":all": Constants.CONST_ALL ]
}
// Male interested in female
if (usr?.interest == Constants.CONST_FEMALE) && (usr?.gender == Constants.CONST_MALE){
expression.filterExpression = "details_fromGender = :fg AND ( match_interest = :ig OR match_interest = :all )"
expression.expressionAttributeValues = [":fg": Constants.CONST_FEMALE, ":ig": Constants.CONST_MALE, ":all": Constants.CONST_ALL ]
}
// Female interested in male
if (usr?.interest == Constants.CONST_MALE) && (usr?.gender == Constants.CONST_FEMALE){
expression.filterExpression = "details_fromGender = :fg AND ( match_interest = :ig OR match_interest = :all )"
expression.expressionAttributeValues = [":fg": Constants.CONST_MALE, ":ig": Constants.CONST_FEMALE, ":all": Constants.CONST_ALL ]
}
// Male interested in all
if (usr?.interest == Constants.CONST_ALL) && (usr?.gender == Constants.CONST_MALE){
expression.filterExpression = "( details_fromGender = :fg OR details_fromGender = :all ) AND match_interest = :ig"
expression.expressionAttributeValues = [":fg": Constants.CONST_MALE, ":ig": Constants.CONST_MALE ]
}
// Female interested in all
if (usr?.interest == Constants.CONST_ALL) && (usr?.gender == Constants.CONST_FEMALE){
expression.filterExpression = "( details_fromGender = :fg OR details_fromGender = :all ) AND match_interest = :ig"
expression.expressionAttributeValues = [":fg": Constants.CONST_MALE, ":ig": Constants.CONST_FEMALE ]
}
return expression
}
您是否绝对确定不能在DynamoDB scan
操作上使用OR
条件? 我并不是说您错了,我只是记得记得这么做了。 如果我正在处理相同的问题,请尝试以下代码:
func findMatches(interestGender: String, userGender: String, allCondition: String, map: AWSDynamoDBObjectMapper) -> AWSTask<AnyObject> {
let scan = AWSDynamoDBScanExpression()
scan.filterExpression = "interest_gender = :interestGender AND usr_gender = :userGender OR interest_gender = :allCondition"
scan.expressionAttributeValues = [":interest_gender":interestGender, ":usr_gender":userGender, ":interest_gender":allCondition]
return map.scan(Rendezvous.self, expression: scan).continue({ (task: AWSTask) -> AnyObject? in
if (task.error != nil) {
print(task.error)
}
if (task.exception != nil){
print(task.exception)
}
if let result = task.result {
return result.items as! [Rendezvous] as AnyObject?
}
return nil
})
}
这将假定您具有符合AWSDynamoDBObjectModel
和AWSDynamoDBModeling
Rendezvous
对象。 尝试一下,让我知道它是否适合您,否则我将删除答案。 直到今晚晚些时候,我才有能力为您进行测试,因此我不确定100%是否可以运行。
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