问题描述
- Why should I use document based database instead of relational database?
- Pros/Cons of document based database vs relational database
我不太了解Google的Bigtable，但想知道Google的BigTable和像MySQL这样的关系数据库。两者有什么限制？
I don't know much about Google's Bigtable but am wondering what the difference between Google's Bigtable and relational databases like MySQL is. What are the limitations of both?
推荐答案
Bigtable是Google发明来处理公司经常处理的大量信息。Bigtable数据集可以增长巨大的大小（许多PB），存储分布在大量的服务器上。使用BigTable的系统包括Google的网络索引和Google地球等项目。
Bigtable is Google's invention to deal with the massive amounts of information that the company regularly deals in. A Bigtable dataset can grow to immense size (many petabytes) with storage distributed across a large number of servers. The systems using Bigtable include projects like Google's web index and Google Earth.
根据：
Bigtable的内部机制与MySQL的内部机制是完全不同的使得比较困难，并且预期目标也不重叠。但你可以认为Bigtable有点像单表数据库。例如，假设您尝试使用MySQL数据库实现Google的整个网络搜索系统时遇到的困难 - Bigtable是为解决这些问题而构建的。
The internal mechanics of Bigtable versus, say, MySQL are so dissimilar as to make comparison difficult, and the intended goals don't overlap much either. But you can think of Bigtable a bit like a single-table database. Imagine, for example, the difficulties you would run into if you tried to implement Google's entire web search system with a MySQL database -- Bigtable was built around solving those problems.
Bigtable数据集可以使用一种基于SQL子集的称为GQL（gee-kwal）的语言从AppEngine之类的服务查询。从GQL显然缺少任何类型的 JOIN 命令。由于Bigtable数据库的分布式特性，在两个表之间执行连接将是非常低效的。相反，程序员必须在他的应用程序中实现这样的逻辑，或者设计他的应用程序，以便不需要它。
Bigtable datasets can be queried from services like AppEngine using a language called GQL ("gee-kwal") which is a based on a subset of SQL. Conspicuously missing from GQL is any sort of JOIN command. Because of the distributed nature of a Bigtable database, performing a join between two tables would be terribly inefficient. Instead, the programmer has to implement such logic in his application, or design his application so as to not need it.
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