xtend | 易学教程

如何向数据库集群快速导入千万条数据

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一、数据导入的方式向MySQL数据库导入数据，通常有两种办法，第一种是利用SOURCE命令，第二种是使用LOAD DATA命令。 SOURCE命令是通过执行SQL文件中的INSERT语句来实现数据的导入。正常情况下，如果我们向单节点的MySQL，用INSERT语句批量写入数据，在普通的PC机上，写入10万条数据，大概需要7~8分钟时间。按照这个速度推算，写入1千万条数据大概需要10个小时以上。如果在集群条件下，这个速度会更慢。 MySQL的集群分为PXC和Replication集群。其中Replication集群是异步传输的，它只保证事物在当前节点成功写入，数据是否能同步到其他节点，Replication集群并不能给我们打包票。所以Replication集群经常出现A节点写入数据，但是在B节点读取不到数据的情况。每年Apple秋季发布会之后，很多人会到Apple官网抢购iPhone手机，然而每年都有顾客会遇到付款之后，订单依旧是未支付的状态。这就是典型的Replication集群的效果，数据出现了不一致。如果采用PXC集群，因为数据是同步传输，所以我们在A节点写入数据，提交事务的时候，PXC必须保证所有MySQL节点都成功写入这条数据，才算事务提交成功，所以不会出现A节点写入数据，在B节点上读取不到数据的情况。因此PXC更加适合保存重要的数据，例如交易记录、学籍信息、考试成绩

2018-01-19 Xtext试用: 快速实现简单领域专用语言(DSL)

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环境搭建使用的Eclipse版本: Oxygen.1a Release (4.7.1a) Build id: 20171005-1200, 通过添加 Xtext - Download 上列出的Releases update site安装xtext IDE和xtext SDK. 之后打开Eclipse, 打开任何文件就报错: An error has occurred. See error log for more details. loader constraint violation: loader (instance of org/eclipse/osgi/internal/loader/EquinoxClassLoader) previously initiated loading for a different type with name "org/aspectj/runtime/internal/AroundClosure" 为避免现有插件和它的冲突, 新安装了更新版Eclipse: Version: Oxygen.2 Release (4.7.2) Build id: 20171218-0600 官方教程原代码试用首先, 参考官方教程: 15 Minutes Tutorial 教程按部就班, 基本没有问题. 唯一碰到的坑是最后将一个dsl文件拆分成多个时,

Command line compiler for XTend

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问题 Hi all I've found XTend (http://xtend-lang.org) and it really sounds great! But, I can't see any standalone command line compiler for this language. It seems only to run under eclipse. I've done some research, and found some people saying, that it has a command line compiler, but I can't find a download link. Does the compiler exist, standalone, or do you need eclipse to use it? Regards 回答1: It is not documented, but there is indeed a command line compiler in the Xtend code base - the same

Programmatically setting a Xtend class as super class of a Java class

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问题 I am currently working on an Eclipse plugin. I want to set programmatically a Xtend class as super class of a Java class. If both classes were Java classes I would do that with the JDT API. The problem is that I cannot access the Xtend classes through the Java AST or the Java Model. This is what I tried to access the Xtend classes: using an ASTParser using IJavaProject.findType() Is there a way to set a Xtend class as super class? Is there a way to set a superclass with a string (package +

How do i diagnose and fix classpath problems?

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问题 I have a tycho project that includes xtend sources. One of my dependencies comes with an older version of JUnit that does not include all features that i need. I also have a dependency on JUnit 4.11. Tycho build is fine, but the xtend compiler (xtend-maven-plugin) seems to see the old JUnit version instead of the new one. How can i fix this? [EDIT] To clarify, this is how my dependencies look like: Project A |--Project B | |-- JUnit 4.8.2 |--JUnit 4.11 In the OSGi world of tycho, this is no

Xtext, multi-file Cross-reference

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问题 I want to call variables declared in another file. The include of the file is done using cross referencing. and the call of the declared too. this is the grammar: Script: includes+=(Include)* assignments+=(Assignment)* g=GetLog? clock=Clock? tests+=Test* ; Assignment: Config |Cosem ; Include: 'INCLUDE' includedScript=[Script|STRING]; Cosem: name=ID '=' 'COSEM' '(' classid=INT ',' version=INT ',' obis=STRING ')' ; AttributeRef: name=[Cosem] "." attributeRef =IDValue ; the declaration is the

Xtext - The type com.google.inject.Inject is not on the classpath

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问题 I am using the following code in JvmModelInferrer.xtend to generate a Java class @Inject extension JvmTypesBuilder def dispatch void infer(Model element, IJvmDeclaredTypeAcceptor acceptor, boolean isPreIndexingPhase) { acceptor.accept(element.toClass(element.name)) [ annotations += annotationRef(Inject); ] } When I try to run the whole project, I get the following error. 5226 [main] ERROR org.eclipse.xtext.xbase.jvmmodel.JvmTypesBuilder - Error initializing JvmElement java.lang

auto pretty formatting in xtext

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问题 I want to ask that is there a way to do Pretty formatting in xtext automatically without (ctrl+shift+f) or turning it on from preference menu. What I actually want is whenever a user completes writing the code it is automatically pretty formatted (or on runtime) without (ctrl+shift+f). 回答1: There is a way for doing that which is called "AutoEdit". It's not exactly when the user completes writing but it's with every token. That's at least what I have done. You can for sure change that. I will

Xtext - Validating for duplicate names

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问题 I have the following grammer, but I want to do some validation on this. I want to make an error if there are duplicate names in the "players" list. Grammer: Football: 'Club' name=STRING playerList=PlayerList footballObjects+=FootballObject ; FootballObject: Player | Coach ; PlayerList: players+=[Player] ( players+=[Player] )* ; Player: 'Player' name=ID ; I tried the following: @Check def checkGreetingStartsWithCapital(Football model) { val names = newHashSet for (g : model.playersList.players

code generation with Xtend

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问题 I am implementing my own DSL and using Xtend to generate C code. I have developed small prototype using XPand/Xtend but now I need to convert prototype into XTend. In Xpand, I used to define "Generate" function to generate C file but I don't know how can I do similar thing using XTend. Any help in this regard would be highly appreciated. «DEFINE Generate FOR dsl::defs::module» «FILE "Com.c" -» /* DATE «dateString()» */ «EXPAND COM_C::COM_Def_C » «ENDFILE» «ENDDEFINE» Thanks and Regards, Hemal