MongoDB: 1. Database

mongo 是 MongoDB 自帶的交互式 Javascript shell，用來對 Mongod 進行操作和管理的交互式環境。

使用 "./mongo --help" 可查看相關連接參數。

$ ./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

相關命令很多，要習慣使用 "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 會自動創建數據庫(db)和集合(collection)，無需顯式執行。

$ ./mongoMongoDB shell version: 1.5.3connecting to: testtype "help" for help> show dbs // 查看當前數據庫列表adminlocal> use blog // 切換到工作數據庫switched to db blog> db // 當前數據庫blog> for (var i = 0; i < 10; i++) db.users.save({name : "user" + i, age : i}) // 插入數據> show dbs // 數據庫 blog 被創建adminbloglocal> show collections // 列表 users 被創建system.indexesusers> db.copyDatabase("blog", "blog2") // 復制數據庫{ "ok" : true }> show dbs // 數據庫 blog2 被創建adminblogblog2local> use blog2 // 切換到 blog2switched to db blog2> show collections // 查看集合列表system.indexesusers> db.users.find() // 查看被復制的數據{ "_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() // 刪除數據庫 blog2{ "dropped" : "blog2", "ok" : true }> show dbs // 確認數據庫刪除成功adminbloglocal> use blog // 切換回 blogswitched to db blog> db.users.drop()  // 刪除集合 userstrue> show collections // 確認集合被刪除system.indexes> exitbye

(2) 還可以在多臺服務器之間復制數據庫。

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

準備好源數據庫后，我們開始在復制。

server32:$ ./mongoMongoDB shell version: 1.5.4connecting to: test> db.copyDatabase("blog", "blog", "192.168.1.202") // 從源服務器復制 blog 數據庫{ "ok" : true }> show dbs // 復制成功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") // 從源服務器克隆當前數據庫(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) 當我們使用 use 切換到某個數據庫時，變量 db 表示當前數據庫。還可以用 getSisterDB() 函數獲取其他數據庫的引用。

> 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) 調用 fsync 命令，可以強制將內存中緩存數據寫回數據庫文件。如果不想等待，可添加 async 參數異步執行。

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

(5) 某些時候需要鎖定系統，阻塞所有寫操作，諸如備份、整理數據庫等等。鎖定時讀操作不受影響。

$ ./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}) // 鎖定{        "info" : "now locked against writes, use db.$cmd.sys.unlock.findOne() to unlock",        "ok" : true}> db.users.find() // 讀操作正常{ "_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" }) // 寫操作被阻塞，等待 ...

另開啟一個終端，解除鎖定。

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

解除后，前一終端被阻塞的寫操作正確返回。