Mongodb初探

一、Mongodb的优点：

l  支持地理空间索引

l  存取JavaScript的函数和值

l  支持MapReduce和其他聚合工具

二、Mongodb的概念

【1】mogodb中的文档

l  多个键及其关联的值有序地放在一起就是文档

 

【2】文档的键和值

l  文档的键-可以是任意utf-8字符串，除了\0,_,$

l  文档的值-其他数据类型（包括文档）

 

【3】文档注意事项：

l  文档中不能有重复的键值

l  文档区分数据类型

l  文档区分大小写

 

【4】集合

l  集合是一组文档

l  集合是无模式的

l  有很多理由，创建一个模式，将相同类型的文档规整到一起。比如索引就更高效

  

【5】数据库

l  多个集合可以组成数据库

l  一个mongodb实例可以承载多个数据库

l  在磁盘上，不同数据库放在不同的文件上

 

【6】保留数据库

l  admin

继承了所有数据库的权限；比如关闭所有的数据库或者关闭服务器

只能从这个用户执行

l  config

在mongodb分片的时候，config数据库存放分片的相关信息

 

三、Mongodb的启动

由于

(1)[main] 32-bit servers don't have journal
ing enabled by default. Please use --journal if you want durability.

(2)exception in initAndList
en: 28663 Cannot start server. The default storage engine 'wiredTiger' is not av
ailable with this build of mongod. Please specify a different storage engine exp
licitly, e.g. --storageEngine=mmapv1., terminating

所以启动参数为：

mongod --dbpath=D:\MongoDB\data --journal --storageEngine=mmapv1

启动之后，显示

2016-10-09T11:48:11.522+0800 I NETWORK  [initandlisten] waiting for connections on port 27017
2016-10-09T13:09:59.392+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:9524 #1 (1 connection now open)
2016-10-09T13:09:59.639+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:9525 #2 (2 connections now open)
2016-10-09T13:44:00.346+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:9559 #3 (3 connections now open)
2016-10-09T13:44:00.431+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:9560 #4 (4 connections now open)
2016-10-09T13:44:16.044+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:9561 #5 (5 connections now open)
2016-10-09T13:44:16.109+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:9562 #6 (6 connections now open)
2016-10-09T15:54:06.653+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:9745 #7 (7 connections now open)
2016-10-09T15:54:06.726+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:9746 #8 (8 connections now open)
2016-10-10T12:24:39.512+0800 I NETWORK  [conn8] end connection 127.0.0.1:9746 (7 connections now open)

启动shell，mongo

D:\MongoDB\Server\3.2\bin>mongo
2016-09-29T09:28:34.602+0800 I CONTROL  [main] Hotfix KB2731284 or later update is installed, no need to zero-out data files
MongoDB shell version: 3.2.9
connecting to: test
Welcome to the MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
        http://docs.mongodb.org/
Questions? Try the support group
        http://groups.google.com/group/mongodb-user
Server has startup warnings:

推荐使用runmogo工具客户端

 

四、Mongodb的使用

【1】javaScript函数

function f(n){

    if (n <= 1)

        return 1;

    else

        return n*f(n-1);

    }

f(4)=24

【2】使用js进行数据的遍历

var collections=["title","content","comments"];

for (i in collections){

    print(db.blog[collections[i]]);

    }

【3】shell的使用--插入更新

post={

    "title":"my blog post",

    "content":"here is my blog post",

    "date":new Date()

    }

 

/* 1 */

{

    "title" : "my blog post",

    "content" : "here is my blog post",

    "date" : ISODate("2016-10-09T06:51:54.710Z")

}

db.blog.insert(post)

 

db.blog.find()

 

/* 1 */

{

    "_id" : ObjectId("57f9eabbd01d44ba3aaeb26c"),

    "title" : "my blog post",

    "content" : "here is my blog post",

    "date" : ISODate("2016-10-09T06:51:54.710Z")

}

db.blog.update({title:"my blog post"},post)

 

/* 1 */

{

    "_id" : ObjectId("57f9eabbd01d44ba3aaeb26c"),

    "title" : "my blog post",

    "content" : "here is my blog post",

    "date" : ISODate("2016-10-09T06:51:54.710Z"),

    "comments" : [

        "test blog"

    ]

}

 

var a=db.blog.findOne();

a;

a.content='update';

db.blog.update({"title" : "my blog post"},a);

db.blog.find();

delete a.comments;

db.blog.update({"title" : "my blog post"},a);

【4】shell的使用--查看js对象

db.blog.insert

 

function ( obj , options, _allow_dot ){

    if ( ! obj )

        throw Error( "no object passed to insert!" );

 

    var flags = 0;

 

    var wc = undefined;

    var allowDottedFields = false;

    if ( options === undefined ) {

        // do nothing

    }

    else if ( typeof(options) == 'object' ) {

        if (options.ordered === undefined) {

            //do nothing, like above

        } else {

            flags = options.ordered ? 0 : 1;

        }

 

        if (options.writeConcern)

            wc = options.writeConcern;

        if (options.allowdotted)

            allowDottedFields = true;

    } else {

        flags = options;

    }

 

    // 1 = continueOnError, which is synonymous with unordered in the write commands/bulk-api

    var ordered = ((flags & 1) == 0);

 

    if (!wc)

        wc = this.getWriteConcern();

 

    var result = undefined;

    var startTime = (typeof(_verboseShell) === 'undefined' ||

                     !_verboseShell) ? 0 : new Date().getTime();

 

    if ( this.getMongo().writeMode() != "legacy" ) {

        // Bit 1 of option flag is continueOnError. Bit 0 (stop on error) is the default.

        var bulk = ordered ? this.initializeOrderedBulkOp() : this.initializeUnorderedBulkOp();

        var isMultiInsert = Array.isArray(obj);

 

        if (isMultiInsert) {

            obj.forEach(function(doc) {

                bulk.insert(doc);

            });

        }

        else {

            bulk.insert(obj);

        }

 

        try {

            result = bulk.execute(wc);

            if (!isMultiInsert)

                result = result.toSingleResult();

        }

        catch( ex ) {

            if ( ex instanceof BulkWriteError ) {

                result = isMultiInsert ? ex.toResult() : ex.toSingleResult();

            }

            else if ( ex instanceof WriteCommandError ) {

                result = isMultiInsert ? ex : ex.toSingleResult();

            }

            else {

                // Other exceptions thrown

                throw Error(ex);

            }

        }

    }

    else {

        if ( ! _allow_dot ) {

            this._validateForStorage( obj );

        }

 

        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];

            }

        }

 

        this.getMongo().insert( this._fullName , obj, flags );

 

        // enforce write concern, if required

        if (wc)

            result = this.runCommand("getLastError", wc instanceof WriteConcern ? wc.toJSON() : wc);

    }

 

    this._lastID = obj._id;

    this._printExtraInfo("Inserted", startTime);

    return result;

}

 

五、Mongodb的数据类型

【1】json:www.json.org仅包含六种数据类型；

l  null，布尔，数字，字符串，数组，对象

l  json没有日期类型，使得日期处理变得繁琐

l  只有一种数字类型，不能区分浮点数和整数，32位，64位数

l  不支持正则表达式和函数类型

【2】mongodb保留json的基本键值对特性

l  null

l  布尔：true,false

l  32位整数

l  64位整数

l  64位浮点数--默认的数字类型

l  字符串

l  符号

l  对象id，12字节，ObjectId()

l  日期：存放毫秒数，不存储时区  new Date()

l  正则表达式：

{"x":/foobar/i}

l  代码，存放js代码

{"x":function(){/******/}}

l  二进制数据

l  最大值：bson

l  最小值：bson

l  未定义：undefined

{"x":undifined}

l  数组：

{ "x" :  ["a","b","c"] }

l  内嵌文档

{"x" : {"fool" :"bar"} }