MongoDB是一个介于关系数据库和非关系数据库之间的产品, 是非关系数据库当中功能最丰富,最像关系数据库的。他支持的数据结构非
MongoDB是一个介于关系数据库和非关系数据库之间的产品,, 是非关系数据库当中功能最丰富,最像关系数据库的。他支持的数据结构非常松散,是类似json的bjson格式,因此可以存储比较复杂的数据类型。 Mongo最大的特点是他支持的查询语言非常强大,其语法有点类似于面向对象的查询语言,几乎可以实现类似关系数据库单表查询的绝大部分功能,而且还支持 对数据建立索引。
它的特点是高性能、易部署、易使用,存储数据非常方便。主要功能特性有:
面向集合存储,易存储对象类型的数据。
模式自由。
支持动态查询。
支持完全索引,包含内部对象。
支持查询。
支持复制和故障恢复。
使用高效的二进制数据存储,包括大型对象(如视频等)。
自动处理碎片,以支持云计算层次的扩展性
支持RUBY,PYTHON,JAVA,C++,PHP等多种语言。
文件存储格式为BSON(一种JSON的扩展)
可通过网络访问
所谓“面向集合”(Collenction-Orented),意思是数据被分组存储在数据集中,被称为一个集合(Collenction)。每个 集合在数据库中都有一个唯一的标识名,并且可以包含无限数目的文档。集合的概念类似关系型数据库(RDBMS)里的表(table),不同的是它不需要定 义任何模式(schema)。
模式自由(schema-free),意味着对于存储在mongodb数据库中的文件,我们不需要知道它的任何结构定义。如果需要的话,你完全可以把不同结构的文件存储在同一个数据库里。
存储在集合中的文档,被存储为键-值对的形式。键用于唯一标识一个文档,为字符串类型,而值则可以是各中复杂的文件类型。我们称这种存储形式为BSON(Binary Serialized dOcument Format)。
MongoDB服务端可运行在Linux、Windows或OS X平台,支持32位和64位应用,默认端口为27017。推荐运行在64位平台,因为MongoDB
在32位模式运行时支持的最大文件尺寸为2GB。
MongoDB把数据存储在文件中(默认路径为:/data/db),为提高效率使用内存映射文件进行管理。
2012-02-28发布2.0.3正式版。上一个版本是2011-12-14的2.0.2.这个版本经过两个RC.包括如下改进
Bug
[SERVER-3112] - mongo* tools logs should not log to stdout (broken w/--out -)
[SERVER-3641] - support mongostat through mongos with authentication
[SERVER-3672] - use min(majority, all "real" nodes) for majority
[SERVER-3763] - when one shard goes down, mongos starts returning failure in getlasterror for all the shards, to already connected client.
[SERVER-3817] - Increment opcounters for bulk insert
[SERVER-3939] - Rollback is trying to log something in the oplog
[SERVER-4115] - copyCollectionFromRemote needs to authenticate
[SERVER-4238] - Make sure authentication always happens when a ScopedConn connects
[SERVER-4387] - command should force reload of config data after multiple stale config exceptions
[SERVER-4399] - mongos doesn't always update shards in response to replica set changes
[SERVER-4400] - attempt to record query plan for a dropped cursor triggers bad file number assertion
[SERVER-4401] - query optimizer cursor may return partial result set for a $or query if the last index match for a $or clause is deleted while it is "current"
[SERVER-4474] - Initial sync should ignore capped collection dup key error, too
[SERVER-4546] - Oplog replay can assert on initial sync if there's no _id index on a capped collection
[SERVER-4547] - Disable full restore of sharded cluster
[SERVER-4591] - MongoDB 2.0.2 fails to build: 'str' object has no attribute 'rpartition'
[SERVER-4626] - If update does not contain an _id in criteria, sync apply can assert and get stuck
[SERVER-4634] - --use-system-all (and --use-system-snappy?) don't actually use system snappy
[SERVER-4643] - one of the shard is down
[SERVER-4665] - Querying against sparse index creates bad state, affecting later queries
[SERVER-4695] - getLog auth checks needs backport
[SERVER-4699] - mongos can segfault after primary failover
[SERVER-4712] - Shards crash fairly frequently when memory is low
[SERVER-4714] - ScopedConn is segfaulting
[SERVER-4745] - Figuring out which shard to send a query to takes a long time when doing large $in queries on the shard key
[SERVER-4749] - fix concurrency api when using openssl
[SERVER-4765] - sharded currentOp doesn't actually pass query
Improvement
[SERVER-2612] - support logRotate under windows
[SERVER-4673] - Don't lock authenticate command if we don't need to
[SERVER-4780] - Improve Memory Leak Warning Message
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