MongoDB常用操作
首先，我們啓動mongoDB:
[root@h3 /]# mongod -f /etc/mongod.conf
Wed Jul 24 23:38:58.195
Wed Jul 24 23:38:58.195 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability.
Wed Jul 24 23:38:58.195
about to fork child process, waiting until server is ready for connections.
forked process: 14093
all output going to: /var/log/mongo/mongod.log
child process started successfully, parent exiting
[root@h3 /]#
然後，我們進入mongo shell:
[root@h3 /]# mongo
MongoDB shell version: 2.4.5
connecting to: test
Server has startup warnings:
Wed Jul 24 23:38:58.244 [initandlisten]
Wed Jul 24 23:38:58.244 [initandlisten] ** NOTE: This is a 32 bit MongoDB binary.
Wed Jul 24 23:38:58.244 [initandlisten] ** 32 bit builds are limited to less than 2GB of data (or less with --journal).
Wed Jul 24 23:38:58.244 [initandlisten] ** Note that journaling defaults to off for 32 bit and is currently off.
Wed Jul 24 23:38:58.244 [initandlisten] ** See http://dochub.mongodb.org/core/32bit
Wed Jul 24 23:38:58.244 [initandlisten]
>
1，具有功能完備的javascript解釋器；
2，可以完成任何javascript命令；
3，可以完成mongoDB操作管理命令，這些命令帶有強烈javascript風格。
例如，我們在shell中執行javascript 操作：
> var x = 100;
> x / 3
33.333333333333336
> x + 20
120
> x -40
60
>
來點更強大的：
> Math.sin(Math.PI / 2)
1
> function fac(n){
... if (n <= 1){
... return 1;
... }
... return n * fac(n - 1);
... }
> fac(5);
120
>
在MongoDB中切換數據庫：
> use foobar
switched to db foobar
> use xyz
switched to db xyz
> db
xyz
>
在MongoDB中新增記錄。
在插入記錄時，MongoDB會檢查文檔是否包含_id，如果文檔沒有包含_id，MongoDB會爲其創建。
> use blog
switched to db blog
> post = {'title' : 'My Blog Post', 'content': 'Here is my blog post.', 'date':new Date()}
{
"title" : "My Blog Post",
"content" : "Here is my blog post.",
"date" : ISODate("2013-07-24T17:15:29.168Z")
}
> db.blog.insert(post)
> db.blog.find()
{ "_id" : ObjectId("51f00bbecd26ce7df43a2e86"), "title" : "My Blog Post", "content" : "Here is my blog post.", "date" : ISODate("2013-07-24T17:15:29.168Z") }
>
在這裏，小述一下： "_id" 爲系統默認增加的字段，用於唯一標示文檔，類似於oracle中的rowid,ObjectId是Id的缺省產生辦法，由12個字節（24個16進制數字）組成，第0-3字節爲時間戳，第4-6字節爲機器標示（一般是主機名的散列值），第7-8字節爲pid,9-11字節爲計數器。
讀取數據：
> db.blog.findOne()
{
"_id" : ObjectId("51f00bbecd26ce7df43a2e86"),
"title" : "My Blog Post",
"content" : "Here is my blog post.",
"date" : ISODate("2013-07-24T17:15:29.168Z")
}
>
修改數據：
> post.comments = []
[ ]
> db.blog.update({title : 'My Blog Post'}, post)
> db.blog.find()
{ "_id" : ObjectId("51f00bbecd26ce7df43a2e86"), "title" : "My Blog Post", "content" : "Here is my blog post.", "date" : ISODate("2013-07-24T17:15:29.168Z"), "comments" : [ ] }
>
刪除數據：
> db.blog.remove({title : 'My Blog Post'})
> db.blog.find()
>
尋求幫助：
> help
db.help() help on db methods
db.mycoll.help() help on collection methods
sh.help() sharding helpers
rs.help() replica set helpers
help admin administrative help
help connect connecting to a db help
help keys key shortcuts
help misc misc things to know
help mr mapreduce
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
show logs show the accessible logger names
show log [name] prints out the last segment of log in memory, 'global' is default
use <db_name> set current database
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
DBQuery.shellBatchSize = x set default number of items to display on shell
exit quit the mongo shell
>
查看函數源碼：
> db.blog.insert
function ( obj , options, _allow_dot ){
if ( ! obj )
throw "no object passed to insert!";
if ( ! _allow_dot ) {
this._validateForStorage( obj );
}
if ( typeof( options ) == "undefined" ) options = 0;
if ( typeof( obj._id ) == "undefined" && ! Array.isArray( obj ) ){
var tmp = obj; // don't want to modify input
obj = {_id: new ObjectId()};
for (var key in tmp){
obj[key] = tmp[key];
}
}
var startTime = (typeof(_verboseShell) === 'undefined' ||
!_verboseShell) ? 0 : new Date().getTime();
this._mongo.insert( this._fullName , obj, options );
this._lastID = obj._id;
this._printExtraInfo("Inserted", startTime);
}
>
MongoDB在非正常關閉後，啓動會出現以下錯誤：
[root@h3 ~]# mongod -f /etc/mongod.conf
Wed Jul 24 23:25:10.802
Wed Jul 24 23:25:10.802 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability.
Wed Jul 24 23:25:10.802
about to fork child process, waiting until server is ready for connections.
forked process: 14043
all output going to: /var/log/mongo/mongod.log
ERROR: child process failed, exited with error number 100
[root@h3 ~]#
PS:
正常關閉MongoDB的方法爲：
進入 mongo shell ,運行如下命令：
> use admin
switched to db admin
> db.shutdownServer()
Wed Jul 24 23:41:42.497 DBClientCursor::init call() failed
server should be down...
Wed Jul 24 23:41:42.536 trying reconnect to 127.0.0.1:27017
Wed Jul 24 23:41:42.539 reconnect 127.0.0.1:27017 failed couldn't connect to server 127.0.0.1:27017
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