小编dsk*_*rvk的帖子

"从java调用clojure"的大多数顶级谷歌点击都已过时,建议使用clojure.lang.RT编译源代码.如果您已经从Clojure项目中构建了一个jar并将其包含在类路径中,您能否帮助清楚地解释如何从Java调用Clojure？

是否可以在DynamoDB中使用Query或Scan API对结果进行ORDER？

我需要知道DynamoDB是否有来自SQL查询的[ORDER BY'field']？

谢谢.

考虑一下,我有4个复制集,配置如下:

{
 "_id": "rs_0",
 "version": 5,
 "members" : [
  {"_id": 1, "host": "127.0.0.1:27001"},
  {"_id": 2, "host": "127.0.0.1:27002"},
  {"_id": 3, "host": "127.0.0.1:27003"},
  {"_id": 4, "host": "127.0.0.1:27004"}
 ]
}

我可以使用连接到所有集 mongo --port <port>

有关于获取有关将独立转换为副本集的信息的文档,但有人可以告诉我如何从副本集转换回独立版本吗？

我开始玩看似非常令人印象深刻的clojure.typed库,但是在我遇到问题之后不久,即使尝试将它应用于简单的函数.有没有人有图书馆的经验？

问题1

(typed/ann square [Double -> Double])
(defn square "Square of"
  [num]
  (* num  num))

类型错误(clojure_study/ideas/swarm/vector_algebra.clj:15:3)返回静态方法的类型clojure.lang.Numbers/multiply是java.lang.Long,期望java.lang.Double.

问题2

(typed/defalias CartesianVector '{:x Double :y Double})
(typed/ann v+ [CartesianVector * -> CartesianVector])
(defn v+ "Sum vector of vectors"
  [& vectors]
  (apply merge-with + vectors))

类型错误(clojure_study/ideas/swarm/vector_algebra.clj:28:3)应用于多态函数的错误参数:(应用合并 - +向量)

问题3

(typed/ann v- [CartesianVector CartesianVector -> CartesianVector])
(defn v- "Diff vector of vectors"
  [v1 v2]
  (merge-with - v1 v2))

类型错误(clojure_study/ideas/swarm/vector_algebra.clj:33:3)多态函数merge-with无法应用于参数:Polymorphic Variables:k v

感谢您提供的任何帮助.

正是按照本页的逐步说明,我试图将我的一个DynamoDB表的内容导出到S3存储桶.我完全按照指示创建了一个管道,但它无法运行.它似乎无法识别/运行EC2资源来执行导出.当我通过AWS Console访问EMR时,我看到如下条目:

Cluster: df-0..._@EmrClusterForBackup_2015-03-06T00:33:04Terminated with errorsEMR service role arn:aws:iam::...:role/DataPipelineDefaultRole is invalid

为什么我收到此消息？我是否需要为管道设置/配置其他东西？

更新:在IAM->RolesAWS控制台下我看到这个DataPipelineDefaultResourceRole:

{
    "Version": "2012-10-17",
    "Statement": [{
    "Effect": "Allow",
    "Action": [
        "s3:List*",
        "s3:Put*",
        "s3:Get*",
        "s3:DeleteObject",
        "dynamodb:DescribeTable",
        "dynamodb:Scan",
        "dynamodb:Query",
        "dynamodb:GetItem",
        "dynamodb:BatchGetItem",
        "dynamodb:UpdateTable",
        "rds:DescribeDBInstances",
        "rds:DescribeDBSecurityGroups",
        "redshift:DescribeClusters",
        "redshift:DescribeClusterSecurityGroups",
        "cloudwatch:PutMetricData",
        "datapipeline:PollForTask",
        "datapipeline:ReportTaskProgress",
        "datapipeline:SetTaskStatus",
        "datapipeline:PollForTask",
        "datapipeline:ReportTaskRunnerHeartbeat"
    ],
    "Resource": ["*"]
    }]
}

这个用于DataPipelineDefaultRole:

{
    "Version": "2012-10-17",
    "Statement": [{
    "Effect": "Allow",
    "Action": [
        "s3:List*",
        "s3:Put*",
        "s3:Get*",
        "s3:DeleteObject",
        "dynamodb:DescribeTable",
        "dynamodb:Scan",
        "dynamodb:Query",
        "dynamodb:GetItem",
        "dynamodb:BatchGetItem",
        "dynamodb:UpdateTable",
        "ec2:DescribeInstances",
        "ec2:DescribeSecurityGroups",
        "ec2:RunInstances",
        "ec2:CreateTags",
        "ec2:StartInstances", …