MongoDB—— 写操作 Core MongoDB Operations (CRUD)

MongoDB使用BSON文件存储在collection中，本文主要介绍MongoDB中的写操作和优化策略。

主要有三种写操作：

Create

Update

Delete

Create：可以分为两种基本操作——insert和updates with the upsert option

Insert（）

BSON文件最大为16M；_id通常作为主key

为了测试写操作是否成功，可以调用getLastError函数{ getLastError: 1 }

db.collection.insert( <document> )

insert方法在第一次调用的时候，自动创建collection。

以下例子中bios为collection名，根据自己情况修改。

例如:

db.bios.insert(

{

_id: 1,

name: { first: 'John', last: 'Backus' },

birth: new Date('Dec 03, 1924'),

death: new Date('Mar 17, 2007'),

contribs: [ 'Fortran', 'ALGOL', 'Backus-Naur Form', 'FP' ],

awards: [

{

award: 'W.W. McDowell Award',

year: 1967,

by: 'IEEE Computer Society'

},

{

award: 'National Medal of Science',

year: 1975,

by: 'National Science Foundation'

},

{

award: 'Turing Award',

year: 1977,

by: 'ACM'

},

{

award: 'Draper Prize',

year: 1993,

by: 'National Academy of Engineering'

}

]

}

)

如果插入操作没有指定_id，则会自动生成一个唯一的id。

使用中括号，同时插入多个文档。

db.bios.insert(

[

{

_id: 3,

name: { first: 'Grace', last: 'Hopper' },

title: 'Rear Admiral',

birth: new Date('Dec 09, 1906'),

death: new Date('Jan 01, 1992'),

contribs: [ 'UNIVAC', 'compiler', 'FLOW-MATIC', 'COBOL' ],

awards: [

{

award: 'Computer Sciences Man of the Year',

year: 1969,

by: 'Data Processing Management Association'

},

{

award: 'Distinguished Fellow',

year: 1973,

by: ' British Computer Society'

},

{

award: 'W. W. McDowell Award',

year: 1976,

by: 'IEEE Computer Society'

},

{

award: 'National Medal of Technology',

year: 1991,

by: 'United States'

}

]

},

{

_id: 4,

name: { first: 'Kristen', last: 'Nygaard' },

birth: new Date('Aug 27, 1926'),

death: new Date('Aug 10, 2002'),

contribs: [ 'OOP', 'Simula' ],

awards: [

{

award: 'Rosing Prize',

year: 1999,

by: 'Norwegian Data Association'

},

{

award: 'Turing Award',

year: 2001,

by: 'ACM'

},

{

award: 'IEEE John von Neumann Medal',

year: 2001,

by: 'IEEE'

}

]

},

{

_id: 5,

name: { first: 'Ole-Johan', last: 'Dahl' },

birth: new Date('Oct 12, 1931'),

death: new Date('Jun 29, 2002'),

contribs: [ 'OOP', 'Simula' ],

awards: [

{

award: 'Rosing Prize',

year: 1999,

by: 'Norwegian Data Association'

},

{

award: 'Turing Award',

year: 2001,

by: 'ACM'

},

{

award: 'IEEE John von Neumann Medal',

year: 2001,

by: 'IEEE'

}

]

}

]

)

调用save（）函数，通过查询collection中的_id域，来决定使用insert还是update。

upsert flags 当插入的文档已经存在，需要对原文当进行覆盖的时候使用此标记。

db.collection.update( <query>,

<update>,

{ upsert: true } )

如果没有文档符合查询要求<query>，则插入文档，举例如下：

db.bios.update(

{

_id: 7,

name: { first: 'Ken', last: 'Thompson' }

},

{

$set: {

birth: new Date('Feb 04, 1943'),

contribs: [ 'UNIX', 'C', 'B', 'UTF-8' ],

awards: [

{

award: 'Turing Award',

year: 1983,

by: 'ACM'

},

{

award: 'IEEE Richard W. Hamming Medal',

year: 1990,

by: 'IEEE'

},

{

award: 'National Medal of Technology',

year: 1998,

by: 'United States'

},

{

award: 'Tsutomu Kanai Award',

year: 1999,

by: 'IEEE'

},

{

award: 'Japan Prize',

year: 2011,

by: 'The Japan Prize Foundation'

}

]

}

},

{ upsert: true } //如果文档存在，覆盖

)

Update（）

主要包括两种操作，update和save

db.collection.update( <query>, <update>, <options>

使用方法同insert中介绍。

下面分情况举例：

1、更新文件中的域

db.bios.update(

{ _id: 1 },

{

$set: { 'name.middle': 'Warner' },

}

)

更新子文档name中的middle域为warner

2、添加新的域

db.bios.update(

{ _id: 3 },

{ $set: {

mbranch: 'Navy',

'name.aka': 'Amazing Grace'

}

}

)

添加mbranch域 和子文档name的aka域

3、移除域

db.bios.update(

{ _id: 3 },

{ $unset: { birth: 1 } }

)

4、更新数组

db.bios.update(

{ _id: 1 },

{ $set: { 'contribs.1': 'ALGOL 58' } }

)

更新contribs数组中第二个元素的值

5、定位，然后更新元素

db.bios.update(

{ _id: 3, 'contribs': 'compiler' },

{ $set: { 'contribs.$': 'A compiler' } }

)

定位id为3，contribs中存在compiler元素的位置，更新为A compiler

6、向数组添加元素

db.bios.update(

{ _id: 1 },

{

$push: { awards: { award: 'IBM Fellow', year: 1963, by: 'IBM' } }

}

)

添加一个新的awards域的元素

7、更新多个文档

db.bios.update(

{ 'awards.award': 'Turing' },

{ $set: { turing: true } },

{ multi: true }

)

save（）函数可以用以下函数来解释：function save( doc ) {

if( doc["_id"] ) {

update( {_id: doc["_id"] }, doc, { upsert: true } );

}

else {

insert(doc);

}

}

Update Operators 操作符

Fields

Name	Description
$inc	Increments the value of the field by the specified amount.
$rename	Renames a field.
$setOnInsert	Sets the value of a field upon documentation creation during an upsert. Has no effect on update operations that modify existing documents.
$set	Sets the value of a field in an existing document.
$unset	Removes the specified field from an existing document.

Array Operators

Name	Description
$	Acts as a placeholder to update the first element that matches the query condition in an update.
$addToSet	Adds elements to an existing array only if they do not already exist in the set.
$pop	Removes the first or last item of an array.
$pullAll	Removes multiple values from an array.
$pull	Removes items from an array that match a query statement.
$pushAll	Deprecated. Adds several items to an array.
$push	Adds an item to an array.

Modifiers

Name	Description
$each	Modifies the $push and$addToSet operators to append multiple items for array updates.
$slice	Modifies the $push operator to limit the size of updated arrays.
$sort	Modifies the $push operator to reorder documents stored in an array.

Bitwise

Name	Description
$bit	Performs bitwise AND andOR updates of integer values.

Isolation

Name	Description
$isolated	Modifies behavior of multi-updates to improve the isolation of the operation.