绝好的MongoDB学习资料之一. Database

mongo 是 MongoDB 自带的交互式 Javascript shell，用来对 Mongod 进行操作和管理的交互式环境。

使用 "./mongo --help" 可查看相关连接参数。

$ ./mongo --helpMongoDB shell version: 1.5.3usage: ./mongo [options] [db address] [file names (ending in .js)]db address can be:  foo                   foo database on local machine  192.169.0.5/foo       foo database on 192.168.0.5 machine  192.169.0.5:9999/foo  foo database on 192.168.0.5 machine on port 9999options:  --shell               run the shell after executing files  --nodb                don't connect to mongod on startup - no 'db address'                        arg expected  --quiet               be less chatty  --port arg            port to connect to  --host arg            server to connect to  --eval arg            evaluate javascript  -u [ --username ] arg username for authentication  -p [ --password ] arg password for authentication  -h [ --help ]         show this usage information  --version             show version information  --ipv6                enable IPv6 support (disabled by default)file names: a list of files to run. files have to end in .js and will exit after unless --shell is specified

相关命令很多，要习惯使用 "help"。

$ ./mongoMongoDB shell version: 1.5.3connecting to: testtype "help" for help> help        help admin                   misc shell commands        show dbs                     show database names        show collections             show collections in current database        show users                   show users in current database        show profile                 show most recent system.profile entries with time >= 1ms        use <db name>                set current database to <db name>        db.help()                    help on DB methods        db.foo.help()                help on collection methods        db.foo.find()                list objects in collection foo        db.foo.find( { a : 1 } )     list objects in foo where a == 1        it                           result of the last line evaluated; use to further iterate        exit                         quit the mongo shell

(1) MongoDB 会自动创建数据库(db)和集合(collection)，无需显式执行。

$ ./mongoMongoDB shell version: 1.5.3connecting to: testtype "help" for help> show dbs // 查看当前数据库列表adminlocal> use blog // 切换到工作数据库switched to db blog> db // 当前数据库blog> for (var i = 0; i < 10; i++) db.users.save({name : "user" + i, age : i}) // 插入数据> show dbs // 数据库 blog 被创建adminbloglocal> show collections // 列表 users 被创建system.indexesusers> db.copyDatabase("blog", "blog2") // 复制数据库{ "ok" : true }> show dbs // 数据库 blog2 被创建adminblogblog2local> use blog2 // 切换到 blog2switched to db blog2> show collections // 查看集合列表system.indexesusers> db.users.find() // 查看被复制的数据{ "_id" : ObjectId("4c33f8fcecf2b9320ac2981a"), "name" : "user0", "age" : 0 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac2981b"), "name" : "user1", "age" : 1 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac2981c"), "name" : "user2", "age" : 2 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac2981d"), "name" : "user3", "age" : 3 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac2981e"), "name" : "user4", "age" : 4 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac2981f"), "name" : "user5", "age" : 5 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac29820"), "name" : "user6", "age" : 6 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac29821"), "name" : "user7", "age" : 7 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac29822"), "name" : "user8", "age" : 8 }{ "_id" : ObjectId("4c33f8fcecf2b9320ac29823"), "name" : "user9", "age" : 9 }> db.dropDatabase() // 删除数据库 blog2{ "dropped" : "blog2", "ok" : true }> show dbs // 确认数据库删除成功adminbloglocal> use blog // 切换回 blogswitched to db blog> db.users.drop()  // 删除集合 userstrue> show collections // 确认集合被删除system.indexes> exitbye

(2) 还可以在多台服务器之间复制数据库。

server64$ ./mongoMongoDB shell version: 1.5.3connecting to: testtype "help" for help> use blogswitched to db blog> for (var i = 0; i < 10; i++) db.users.save({name : "user" + i, age : i})> use newsswitched to db news> for (var i = 0; i < 10; i++) db.articles.save({title : "title" + i})> show dbsadminbloglocalnews> exitbye

准备好源数据库后，我们开始在复制。

server32:$ ./mongoMongoDB shell version: 1.5.4connecting to: test> db.copyDatabase("blog", "blog", "192.168.1.202") // 从源服务器复制 blog 数据库{ "ok" : true }> show dbs // 复制成功adminbloglocal> use blogswitched to db blog> show collectionssystem.indexesusers> db.users.find(){ "_id" : ObjectId("4c33fadb15b7f104d297e644"), "name" : "user0", "age" : 0 }{ "_id" : ObjectId("4c33fadb15b7f104d297e645"), "name" : "user1", "age" : 1 }{ "_id" : ObjectId("4c33fadb15b7f104d297e646"), "name" : "user2", "age" : 2 }{ "_id" : ObjectId("4c33fadb15b7f104d297e647"), "name" : "user3", "age" : 3 }{ "_id" : ObjectId("4c33fadb15b7f104d297e648"), "name" : "user4", "age" : 4 }{ "_id" : ObjectId("4c33fadb15b7f104d297e649"), "name" : "user5", "age" : 5 }{ "_id" : ObjectId("4c33fadb15b7f104d297e64a"), "name" : "user6", "age" : 6 }{ "_id" : ObjectId("4c33fadb15b7f104d297e64b"), "name" : "user7", "age" : 7 }{ "_id" : ObjectId("4c33fadb15b7f104d297e64c"), "name" : "user8", "age" : 8 }{ "_id" : ObjectId("4c33fadb15b7f104d297e64d"), "name" : "user9", "age" : 9 }> use newsswitched to db news> db.cloneDatabase("192.168.1.202") // 从源服务器克隆当前数据库(news){ "ok" : true }> show dbsadminbloglocalnews> show collectionsarticlessystem.indexes> db.articles.find(){ "_id" : ObjectId("4c33fb6215b7f104d297e64e"), "title" : "title0" }{ "_id" : ObjectId("4c33fb6215b7f104d297e64f"), "title" : "title1" }{ "_id" : ObjectId("4c33fb6215b7f104d297e650"), "title" : "title2" }{ "_id" : ObjectId("4c33fb6215b7f104d297e651"), "title" : "title3" }{ "_id" : ObjectId("4c33fb6215b7f104d297e652"), "title" : "title4" }{ "_id" : ObjectId("4c33fb6215b7f104d297e653"), "title" : "title5" }{ "_id" : ObjectId("4c33fb6215b7f104d297e654"), "title" : "title6" }{ "_id" : ObjectId("4c33fb6215b7f104d297e655"), "title" : "title7" }{ "_id" : ObjectId("4c33fb6215b7f104d297e656"), "title" : "title8" }{ "_id" : ObjectId("4c33fb6215b7f104d297e657"), "title" : "title9" }> exitbye

(3) 当我们使用 use 切换到某个数据库时，变量 db 表示当前数据库。还可以用 getSisterDB() 函数获取其他数据库的引用。

> use adminswitched to db admin> dbadmin> blog = db.getSisterDB("blog")blog> blog.users.insert({name : "abc"})> blog.users.find({name : "abc"}){ "_id" : ObjectId("4c3419b0492aa4cfbec11895"), "name" : "abc" }

(4) 调用 fsync 命令，可以强制将内存中缓存数据写回数据库文件。如果不想等待，可添加 async 参数异步执行。

> use adminswitched to db admin> db.runCommand({fsync : 1}){ "numFiles" : 6, "ok" : true }> db.runCommand({fsync : 1, async : true}){ "numFiles" : 6, "ok" : true }

(5) 某些时候需要锁定系统，阻塞所有写操作，诸如备份、整理数据库等等。锁定时读操作不受影响。

$ ./mongoMongoDB shell version: 1.5.3connecting to: testtype "help" for help> use blogswitched to db blog> admin = db.getSisterDB("admin")admin> admin.runCommand({fsync : 1, lock : 1}) // 锁定{        "info" : "now locked against writes, use db.$cmd.sys.unlock.findOne() to unlock",        "ok" : true}> db.users.find() // 读操作正常{ "_id" : ObjectId("4c33fadb15b7f104d297e644"), "name" : "user0", "age" : 0 }{ "_id" : ObjectId("4c33fadb15b7f104d297e645"), "name" : "user1", "age" : 1 }{ "_id" : ObjectId("4c33fadb15b7f104d297e646"), "name" : "user2", "age" : 2 }{ "_id" : ObjectId("4c33fadb15b7f104d297e647"), "name" : "user3", "age" : 3 }{ "_id" : ObjectId("4c33fadb15b7f104d297e648"), "name" : "user4", "age" : 4 }{ "_id" : ObjectId("4c33fadb15b7f104d297e649"), "name" : "user5", "age" : 5 }{ "_id" : ObjectId("4c33fadb15b7f104d297e64a"), "name" : "user6", "age" : 6 }{ "_id" : ObjectId("4c33fadb15b7f104d297e64b"), "name" : "user7", "age" : 7 }{ "_id" : ObjectId("4c33fadb15b7f104d297e64c"), "name" : "user8", "age" : 8 }{ "_id" : ObjectId("4c33fadb15b7f104d297e64d"), "name" : "user9", "age" : 9 }> db.users.save({name : "xyz" }) // 写操作被阻塞，等待 ...

另开启一个终端，解除锁定。

> use adminswitched to db admin> db.$cmd.sys.unlock.findOne(){ "ok" : 1, "info" : "unlock requested" }

解除后，前一终端被阻塞的写操作正确返回。

(6) 调用 validate() 验证集合是否存在错误。

> db.users.validate(){        "ns" : "blog.users",        "result" : "validate  firstExtent:0:2600 ns:blog.users  lastExtent:0:23d00 ns:blog.users  # extents:2  datasize?:4640 nrecords?:116 lastExtentSize:9216  padding:1  first extent:    loc:0:2600 xnext:0:23d00 xprev:null    nsdiag:blog.users    size:2304 firstRecord:0:26b0 lastRecord:0:2ec8  116 objects found, nobj:116  6496 bytes data w/headers  4640 bytes data wout/headers  deletedList: 0000000010000000000  deleted: n: 1 size: 4672  nIndexes:1    blog.users.$_id_ keys:116",        "ok" : true,        "valid" : true,        "lastExtentSize" : 9216}