[熵增] 由无序到有序 http://spark.apache.org/docs/latest/rdd-programming-guide.html#shuffle-operations Shuffle operations Certain operations within Spark trigger an event known as the shuffle. The shuffle is Spark’s mechanism for re-distributing data so that…

一 简介 Shuffle,简而言之,就是对数据进行重新分区,其中会涉及大量的网络io和磁盘io,为什么需要shuffle,以词频统计reduceByKey过程为例, serverA:partition1: (hello, 1), (word, 1)serverB:partition2: (hello, 2) shuffle之后: serverA:partition1: (hello, 1), (hello, 2)serverB:partition2: (word, 1) 最后才能得到结果: (h…

参考: http://spark.apache.org/docs/latest/programming-guide.html 后面懒得翻译了,英文记的,以后复习时再翻. 摘要:每个Spark application包含一个driver program 来运行main 函数,在集群上进行各种并行操作. RDD是Spark的核心.除了RDD,Spark的另一个抽象时并行操作中使用的两种 shared variables: broadcast variables和accumulators. Spark…

http://acm.hdu.edu.cn/showproblem.php?pid=3280 用了简单的枚举. Equal Sum Partitions Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 453    Accepted Submission(s): 337 Problem Description An equal sum…

Equal Sum Partitions Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 551    Accepted Submission(s): 409 Problem Description An equal sum partition of a sequence of numbers is a grouping of the…

Reference: http://blogs.msdn.com/b/felixmar/archive/2011/08/29/partitioning-amp-archiving-tables-in-sql-server-part-2-split-merge-and-switch-partitions.aspx In the 1st part of this post, I explained how to create a partitioned table using a partition…

Rotating partitions   You can use the ALTER TABLE statement to rotate any logical partition to become the last partition. Rotating partitions is supported for partitioned (non-universal) table spaces and range-partitioned table spaces, but not for pa…

This is a common question asked by many Kafka users. The goal of this post is to explain a few important determining factors and provide a few simple formulas. More Partitions Lead to Higher Throughput The first thing to understand is that a topic pa…

集群为了保证数据一致性,在同步数据的同时也会通过节点之间的心跳通信来保证对方存活.那如果集群节点通信异常会发生什么,系统如何保障正常提供服务,使用何种策略回复呢? rabbitmq提供的处理脑裂的方法有两种:autoheal.pause_minority. autoheal指的是在出现脑裂且恢复时采用分区中与客户端连接数最多的一个分区来作为winner,并将所有的losers分区重启. pause_miniroty指的是在出现脑裂后判断自己是否为众数者majority,即自己所在分区是否为总节点…

Self-made millionaire Steve Siebold spent 26 years interviewing some of the wealthiest people in the world before condensing his findings in his book "How Rich People Think." He found that the secret to getting rich "is not in the mechanics…

2013-05-01 Created By BaoXinjian…

why we need partitions The first and most demanding reason to use partitions in a database is to increase the performance of the database. This is achieved by partition-wise joins; if a user’s queries perform a lot of full-table scans, partitioning w…

[user@username home]$ lspci00:00.0 Host bridge: Intel Corporation 4th Gen Core Processor DRAM Controller (rev 06)00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor PCI Express x16 Controller (rev 06)00:14.0 USB controller: I…

概述:在Oracle数据库中,分区(partitioning)可以使非常大的表(table)或索引(index)分解为小的易管理的块(pieces),这些块被称作分区(partitions).每个分区都必须有相同的逻辑结构,如列名.数据类型.约束条件等,但是每个分区都可以都各自独立的物理结构. 分区的好处: 1.增加可用性: 2.易于模式对象的管理 3.减少在OLTP系统中对资源的争用 4.提高在数据仓库中查询的性能 分区键(Partition Key) 分区键是一或多个用来决定每一行去哪个分区…

在前面2篇关于Table View的介绍中,我们使用的Style都是Plain,没有分组,没有index,这次学习的Table View和iphone中的通讯录很像,有一个个以字符为分割的组,最右边有一列小字符作为index,最顶端有一个搜索栏可以进行搜索,好了,下面开始这次的学习. 1)创建一个新的项目,template选择Single View Application,命名为Sections 2)添加Table View,连接delegate和data source到File's Owner…

Coin partitions Let p(n) represent the number of different ways in which n coins can be separated into piles. For example, five coins can separated into piles in exactly seven different ways, so p(5)=7. OOOOOOOOO OOOO OOOOO O OOO OO OOO O O OO O O O…

from: http://www.addictivetips.com/mobile/android-partitions-explained-boot-system-recovery-data-cache-misc/ Unless you have been using your Android phone just for calls, SMS, browsing and basic apps, you should know that Android uses several partiti…

问题概述 Oracle Advanced Supply Chain Planning最初的设置职责的时候有点问题,不知是不是要打什么补丁或其它配置什么东东,, 这个提示,,但我查到的分区是还有可用分区的,里面的逻辑关系有点搞乱 解决方法 原因:因为 ORA-02149: 指定的分区不存在 ORA-06512: 在 "SYSTEM.AD_DDL", line 165 ORA-06512: 在 "APPS.MSC_MANAGE_PLAN_PARTITIONS", lin…

Author: kwu [解决]hive动态添加partitions不能超过100的问题,全量动态生成partitions超过100会出现例如以下异常: The maximum number of dynamic partitions is controlled by hive.exec.max.dynamic.partitions and hive.exec.max.dynamic.partitions.pernode. Maximum was set to: 100 解决100限制,可设置例…

1.partitions 表中的常用列说明: 1.table_schema:表所在的数据库名 2.table_name:表名 3.partition_method:表分区采用的分区方法 4.partition_expression:分区键 5.partions_name:分区名 6.table_rows:分区中所包涵的数据行数 7.data_free:分区中还未使用的空间 2.例子: 查询实例中的分区表.分区方法,分区字段 select concat(table_schema,'.',table…

Problem Description An equal sum partition of a sequence of numbers is a grouping of the numbers (in the same order as the original sequence) in such a way that each group has the same sum. For example, the sequence: 2 5 1 3 3 7 may be grouped as: (2…

UITableView的style有plain和grouped两种样式,两种样式各有不同的风格和功能,plain样式已经封装好了悬停功能,gouped样式则为我们在区头和区尾在实际项目开发中需要我们选择不同的样式完成不同的功能,下面就说说grouped样式的UITableView在开发中的那些值得注意的事项 1.grouped样式的UITableView顶部默认会有一段空白,很多人理解成是tableHeaderView,笔者验证后得出的结论确是如此,很多时候我们不想保留这个效果,可以有两种解决方…

https://docs.microsoft.com/en-us/sql/analysis-services/multidimensional-models-olap-logical-cube-objects/partitions-partition-storage-modes-and-processing The storage mode of a partition affects the query and processing performance, storage requireme…

网络分区的意义 RabbitMQ的模型类似交换机模型,且采用erlang这种电信网络方面的专用语言实现.RabbitMQ集群是不能跨LAN部署(如果要WAN部署需要采用专门的插件)的,也就是基于网络情况良好的前提下运行的. 为什么RabbitMQ需要这种前提假设?这个和它本身的数据一致性复制原理有关.RabbitMQ采用的镜像队列是一种环形的逻辑结构,如下图: RabbitMQ除了发布(Publish)消息之外,所有的其余操作都是在master上完成,之后再将有影响的操作同步到slave节点上.…

错误如下: 11:57:24 [org.springframework.kafka.KafkaListenerEndpointContainer#0-0-C-1] WARN  o.apache.kafka.clients.NetworkClient - [Consumer clientId=consumer-2, groupId=test_api] 3 partitions have leader brokers without a matching listener, including [t…

GParted Projects GNOME Partition Editor for creating, reorganizing, and deleting disk partitions. It uses libparted from the parted project to detect and manipulate partition tables. Optional file system tools permit managing file systems not include…

版本: scala:2.11.8 spark:2.11 hbase:1.2.0-cdh5.14.0 报错信息: java.lang.IllegalStateException: Consumer is not subscribed to any topics or assigned any partitions 分析原因: 从指定的主题或者分区获取数据,在poll之前,你没有订阅任何主题或分区是不行的,每一次poll,消费者都会尝试使用最后一次消费的offset作为接下来获取数据的start o…

[ZOJ1482]Partitions 题目大意: 给定一个\(n\times n(n\le3000)\)的\(\texttt 0/\texttt1\)矩阵,求去掉所有的\(1\)以后,矩阵被分成几个四连通块. 空间限制1M. 思路: 由于空间限制为1M,因此我们需要一个空间\(\mathcal O(n)\)的做法. 考虑并查集,每次遇到相邻的连通块就合并. 由于合并时只需要考虑上下两行,此时连通块个数不超过\(2n\),因此我们只需要空间回收,使得并查集上只保留这不超过\(2n\)个结点即可.…

[CF961G]Partitions 题意:给出n个物品,每个物品有一个权值$w_i$,定义一个集合$S$的权值为$W(S)=|S|\sum\limits_{x\in S} w_x$,定义一个划分的权值为$V(R)=\sum\limits_{S\in R} W(S)$.求将n个物品划分成k个集合的所有方案的权值和. $n,k\le 2\cdot 10^5,w_i\le 10^9$ 题解:第二类斯特林数针是太好用辣! 显然每个物品都是独立的,所以我们只需要处理出每个物品被统计的次数即可,说白了就是…

[CF961G]Partitions(第二类斯特林数) 题面 CodeForces 洛谷 题解 考虑每个数的贡献,显然每个数前面贡献的系数都是一样的. 枚举当前数所在的集合大小,所以前面的系数\(p\)就是: \[\begin{aligned} p&=\sum_{i=1}^n{n-1\choose i-1}i\begin{Bmatrix}n-i\\k-1\end{Bmatrix}\\ &=\sum_{i=1}^n{n-1\choose i-1}i\frac{1}{(k-1)!}\sum_{…