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Impala 性能调整 下面的章节介绍影响 Impala 功能性能的各种因素，并对 Impala 查询和其他 SQL 操作进行性能调整、监控和基准测试。 这一章节同样描述了最大化 Impala 可扩展性的技术。可扩展性与性能相关：它意味着当系统负载增加时仍保持高性能(Scalability is tied to performance: it means that performance remains high as the system workload increases)。例如，减少查询的硬盘 I/O 可以加快单个的查询，与此同时，导致可以同时运行更多查询，从而提升了可扩展性。有时候，一种优化技术提升了性能的同时更增加了可扩展性。例如，减少查询的内存使用可能不会很大的提高查询性能，但是通过允许同时运行更多的 Impala 查询或其他类型的作业而不会耗尽内存，从而提升了可扩展性。 Note : 在开始任何性能调整和基准测试之前，请确保你的系统已经按照 Post-Installation Configuration for Impala 中的设置进行配置。 Partitioning . 这一技术基于频繁查询的列上的不同的值，把数据物理拆分开来，允许查询跳过读取表中很大部分的数据 Performance Considerations for Join Queries .

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: As I get it in RC2 there's a support for hosting applications within Windows Services. I tried to test it on a simple web api project (using .NET Framework 4.6.1). Here's my Program.cs code: using System; using System.IO; using System.Linq; using System.ServiceProcess; using Microsoft.AspNetCore.Hosting; using Microsoft.AspNetCore.Hosting.WindowsServices; namespace WebApplication4 { public class Program : ServiceBase { public static void Main(string[] args) { if (args.Contains("--windows-service")) { Run(new Program()); return; } var program

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I’m hoping to set up a SFTP server in Java using Apache MINA. It seems to start OK, but when I try to connect to it with an OpenSSH client, I get: $ ssh localhost -p 2222 Unable to negotiate with ::1: no matching host key type found. Their offer: ssh-dss $ ssh -V OpenSSH_7.1p1, OpenSSL 1.0.2d 9 Jul 2015 The Java app logs: ! java.lang.IllegalStateException: Unable to negotiate key exchange for server host key algorithms (client: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have a two-nodes kafka cluster (EC2 instances) where each node is used as a separate broker. When I run a producer on the leader instance with the following command: kafka-console-producer.sh --broker-list localhost:9092 --topic test I get the following errors. test message [2017-01-09 13:22:39,483] WARN Error while fetching metadata with correlation id 0 : {test=UNKNOWN_TOPIC_OR_PARTITION} (org.apache.kafka.clients.NetworkClient) [2017-01-09 13:22:39,562] WARN Error while fetching metadata with correlation id 1 : {test=UNKNOWN_TOPIC_OR

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Alright. I'm attempting to complete a school assignment and cannot for the life of me figure this out. I'm trying to use powershell to pass values from one function to another making a "modular" type script. I can't seem to figure out how to move the values out of the scope of the function without using the $script:xxxxx. Is there another way to move the values in powershell as a regular argument parameter pass by reference? Here's what I have: function main { inputGrams($carbGrams, $fatGrams) $carbGrams $carbGrams calcGrams displayInfo }

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I've been trying write safe code that supports -whatif with the ShouldProcess method so my users have an idea of what a cmdlet is supposed to do before they run it for real. However I’ve run into a bit of a snag. If I call a script with -whatif as an argument, $pscmdlet.ShouldProcess will return false. All well and good. If I call a cmdlet defined in the same file (that has SupportsShouldProcess=$true) it will return false as well. However, if I am calling a cmdlet defined in another module I have loaded using Import-Module, it will return

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have an web service call to bring down a JSON object and it only works if I have the IP address and not the host name. I have been fine using IP addresses but now I need to have the host name. Here is my code StringBuilder stringBuilder = new StringBuilder(); HttpParams httpParams = new BasicHttpParams(); HttpConnectionParams.setConnectionTimeout(httpParams, 3000); HttpConnectionParams.setSoTimeout(httpParams, 7000); DefaultHttpClient httpClient = new DefaultHttpClient(httpParams); HttpPost httpost = new HttpPost(URL); try { HashMap<String

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: When I execute the "make" command of source of Android 6.0, it failed. Here is the error message, I can't see and don't find any resolve method. Please help me. [ 31% 8837/27694] Build: out/host/darwin-x86/obj/EXECUTABLES/jack_intermediates/jack FAILED: /bin/bash -c "(true) && (out/host/darwin-x86/bin/jack-admin install-server out/host/darwin-x86/framework/jack-launcher.jar out/host/darwin-x86/framework/jack-server.jar 2>&1 || (exit 0)) && (JACK_SERVER_VM_ARGUMENTS=\"-Dfile.encoding=UTF-8 -XX:+TieredCompilation\" out/host/darwin-x86/bin/jack

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have a shared /home setup using Perceus Cluster Software ( http://perceus.org ) for our Cluster. Nodes are using CentOS 6.1 x86_64. /home is shared from the head to the nodes by nfs (NFSv4). root@head~]$ cat /etc/exports /var/lib/perceus/ 10.10.10.0/255.255.255.0(ro,no_root_squash,async) /home/ 10.10.10.0/255.255.255.0(rw,no_root_squash,no_all_squash,async) Here is the /etc/fstab on each node (all the same). ... 10.10.10.2:/var/lib/perceus/ /var/lib/perceus/ nfs ro,soft,bg 0 0 10.10.10.2:/home/ /home nfs rw,soft,bg 0 0 /etc/fstab on nodes

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I need to know the database name and database server name inside a symfony project. How can one access the current database connection settings programmatically in symfony (using Doctrine)? 回答1: for example: foreach(Doctrine_Manager::getInstance()->getConnections() as $connection){ $conn = $connection->getOptions(); preg_match('/host=(.*);/', $conn['dsn'], $host); var_dump($host); } 回答2: Assuming you have the EntityManager as $this->em Get Doctrine Database Name from Symfony2: $this->em->getConnection()->getDatabase(); Get Doctrine Host Name