ventricular septal defect_three identical strangers

ventricular septal defect_three identical strangers转一个BLOG,是美国一同行写的关于eXtremeDB的,但作者似乎是个中国人。这是BLOG原文地址:http://www.weiqigao.com/blog/2006/04/25/extremedb_exposed.html…

大家好,又见面了,我是你们的朋友全栈君。如果您正在找激活码,请点击查看最新教程,关注关注公众号 “全栈程序员社区” 获取激活教程,可能之前旧版本教程已经失效.最新Idea2022.1教程亲测有效,一键激活。

Jetbrains全系列IDE稳定放心使用

转一个BLOG,是美国一同行写的关于eXtremeDB的,但作者似乎是个中国人。这是BLOG原文地址:http://www.weiqigao.com/blog/2006/04/25/extremedb_exposed.html

 

eXtremeDB eXposed

Clever title, isn’t it? Jonathan thinks so.

OK. Today’s OCI C++ lunch features Rob Martin talking about McObject‘s eXtremeDB embedded database product.

First person is Rob now.

We evaluated this product because a key customer wanted to use a embedded database as the foundation for their next generation products. eXtremeDB won the evaluation.

It is a memory resident database; can be put in the process space, or in shared memory. If you put it in heap, there is a feature that allows you to persist the data.

Performance of this thing is extremely good. Transactions incur low overhead.

It is a commercial product.

We found it to be fairly reliable. We did hit some problems. But they are all resolved by either us understanding the product better, or by McObject acknowledges them as bugs and subsequently fixed.

Small foot print, not heavy weight.

Times Ten, a competitor of eXtremeDB was bought by Oracle.

They have a DDL and a schema compiler. It supports structs, including nested structs. But a structure needs to be inside a class for instantiation.

Ways to identify objects in the database: oid (database wide), autoid (system generated serial number), ref (embedded reference to an entity’s oid.)

Standard CRUD. Finders. Lookup by hash. Lookup by tree index (unique as well as non-unique.)

Transactions are simple: read, write, commit, rollback. Transactions are database scoped. You can change it through build time switches, but for our usage scenarios, database wide locking turns out to be optimal.

Kevin, our resident eXtremeDB expert, chimed in: “you have to understand how fast their transactions is. They are in microseconds.”

There is also a limit on the number of entities that you can touch within a transaction.

Supports persistence which is essentially transactions logging. It depends on the OS file system. On recovery, one “sync”s the disk image with the memory image.

eXtremeDB claims to have object semantics. But the content is rich structure types. The primary interface is structured procedure calls. There is a thin object wrapper that is generated from the DDL. It feels more relational to me than object based.

The company (McObject) is in Seattle with a group in Washington, DC. They do their thing through memory management and aggressive locking strategies tailored to the app. They avoid heap allocation of memory in the engine.

We felt very comfortable with this database. We didn’t do much C++ structures in our code and uses eXtremeDB extensively.

Their support staff is very responsive. The turn around time is usually within 24 hours. All of our support requests have been resolved. We did find out one bug regarding a clever bit of threading code (transaction without mutex) that only manifests itself on dual CPU machines running Windows and that one took two or three rounds.

OCI and McObject are partners of each other now.

Their DDL supports: signed, unsigned char (64K limit) enum, struct (only fixed size structs can be oids), autoid_t, blog, data, ref, string, time, vector.

And here’s an example:

declare database eeDemo;
declare oid personId[1024];

compact class Location {
  string streetAddress;
  string city;
  string state;
  string zipcode;
  autoid[4096];

  tree byZipCode;
};

compact class Person {
  oid;
  autoid_t home;
  autoid_t work;
  autoid_t temp;
};

We added MPC support for compiling the eXtremeDB schema. We don’t run it by hand.

The generated code are C and C++ header and implementation files. The generated C code will have functions for Person_home_get() and Person_home_put(). The generated C++ code will have a Person class that has home_get() and home_put() methods.

Search methods and comparison methods are generated. Cursor manipulation code for using any tree index is also generated. A checkpoint() method is generated to update hash indexes after entity manipulation.

The client code looks like this:

mco_error_set_handler(onError);
start();
uint4 dbSize = (1 * 1024 * 1024);
uint2 pageSize = 4096;
void * heap = malloc(dbSize);
mco_db_open("eeDemo");
mco_db_h dbHandle;
connect(dbName, &dbHandle);
mco_trans_h txn;
startWriteTxn(&dbHandle, &txn);
rollback(&txn);
startReadTxn(&dbHandle, &txn);

{
  mco_trans_h txn2;
  startReadTxn(&dbHandle, &txn2);
  commit(&txn2);
}

disconnect(&dbHandle);
closeDB("eeDemo");
stop();

We wrote a set of wrappers that made using eXtremeDB very handy, including a DB registry, Transaction, TransGuard, ReadTransGuard, WriteTransGuard, WriteTransGuardProxy. The various trans guards uses the C++ guard concept to make database code dead easy.

The eXtremeDB product has some features, such as SQL and events, that we did not use.

Rob is done. First person is Weiqi now.

Until next time.

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/16196379/viewspace-606989/,如需转载,请注明出处,否则将追究法律责任。

转载于:http://blog.itpub.net/16196379/viewspace-606989/

版权声明:本文内容由互联网用户自发贡献,该文观点仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 举报,一经查实,本站将立刻删除。

发布者:全栈程序员-用户IM,转载请注明出处:https://javaforall.cn/182192.html原文链接:https://javaforall.cn

【正版授权,激活自己账号】: Jetbrains全家桶Ide使用,1年售后保障,每天仅需1毛

【官方授权 正版激活】: 官方授权 正版激活 支持Jetbrains家族下所有IDE 使用个人JB账号...

(0)


相关推荐

  • tcp和udp的区别和使用场景_TCP跟UDP有什么不同

    tcp和udp的区别和使用场景_TCP跟UDP有什么不同TCPTCP是一种面向有连接的传输层协议,能够对自己提供的连接实施控制。适用于要求可靠传输的应用,例如文件传输。UDPUDP是一种面向无连接的传输层协议,不会对自己提供的连接实施控制。适用于实时应用,例如:IP电话、视频会议、直播等。…

  • 设被排序的节点序列共有N个节点_YFP载体N端序列

    设被排序的节点序列共有N个节点_YFP载体N端序列7-1 求奇数分之一序列前N项和 (20分)本题要求编写程序,计算序列 1 + 1/3 + 1/5 + … 的前N项之和。输入格式: 输入在一行中给出一个正整数N。输出格式: 在一行中按照“sum = S”的格式输出部分和的值S,精确到小数点后6位。题目保证计算结果不超过双精度范围。 输入样例: 23 输出样例: sum = 2.549541#include<io…

  • nginx 配置ssl

    nginx 配置sslnginx配置ssl

  • STM32项目总结及代码中delay函数需慎用

    STM32项目总结及代码中delay函数需慎用这半年实验室做了个智能XX的调度平台,大概思想是通过部署的端设备实时采集信息并且通过通信的方式发送给云端服务器,最后可以实现WEB端和小程序的实时访问和监控,上位机方面自不用说,硬件方面,昨天把做出的智能XX终端给实验室的嵌入式大牛徐老师指教下,徐老师看到代码第一眼就说你们这个是不是根据网上某些案例改的,我回答说是根据淘宝店家或者论坛上找到的代码改的,然后徐老师点评到,如果做的东西是…

  • 数电和模电的理解「建议收藏」

    数电和模电的理解「建议收藏」模电模拟信号:随处可见的自然信号都是模拟信号,模拟信号在时间上和取值上都是连续的,画出来就是一条连续的曲线,可以完全地“模拟”自然信号。模电是指用来对模拟信号进行传输、变换、处理、放大、测量和显示等工作的电路。模拟信号是指连续变化的电信号。模拟电路是电子电路的基础,它主要包括放大电路、信号运算和处理电路、振荡电路、调制和解调电路及电源等。数电数字信号:在时间上和取值上都是不连续的。数字信号存在“采样”,数字信号的值只能在采样点变化。数字信号存在“量化”,数字信号的值只

  • 百度面试题

    百度面试题1.一个int数组,里面数据无任何限制,要求求出所有这样的数a[i],其左边的数都小于等于它,右边的数都大于等于它。能否只用一个额外数组和少量其它空间实现。这道题的解答请看下一篇日志2.一个文件,内含一千万行字符串,每个字符串在1K以内,要求找出所有相反的串对,如abc和

发表回复

您的电子邮箱地址不会被公开。

关注全栈程序员社区公众号