dqMongoDB 3. Schema Designaq

MongoDB: 3. Schema Design

1. Document-Oriented

MongoDB 是一种面向文档(document-oriented)的数据库?其内存储的是一种

JSON-like 结构化数据。尽管拥有和关系型数据库 Database/Table 类似的的

DB/Collection 概念?但同一 Collection 内的 Document 可以拥有不同的属

性。

(注: 以下 > 提示符表示 mongo JS 代码?>>> 为 Python 代码)

> use blog

switched to db blog

> db.users.insert({name:"user1", age:15}) > db.users.insert({name:"user2", age:20, sex:1})

> db.users.find()

{ "_id" : ObjectId("4c479885089df9b53474170a"), "name" : "user1", "age" :

15 }

{ "_id" : ObjectId("4c479896089df9b53474170b"), "name" : "user2", "age" :

20, "sex" : 1 }

可以通过 $exists 判断某个字段是否存在。

> db.users.find({sex:{$exists:true}}) { "_id" : ObjectId("4c479896089df9b53474170b"), "name" : "user2", "age" :

20, "sex" : 1 }

2. Embed vs. Reference

Document 采取 JSON-like 这种层级结构?因此我们可以直接用嵌入(Embed)代

替传统关系型数据库的关联引用(Reference)。

> u = db.users.findOne({name:"user1"}) {

"_id" : ObjectId("4c479885089df9b53474170a"),

"name" : "user1",

"age" : 15

}

> u.address = ["address1", "address2"] [ "address1", "address2" ]

> db.users.save(u)

> db.users.findOne({name:"user1"}) {

"_id" : ObjectId("4c479885089df9b53474170a"),

"name" : "user1",

"age" : 15,

"address" : [

"address1",

"address2"

]

}

> db.users.findOne({address:"address1"}) {

"_id" : ObjectId("4c479885089df9b53474170a"),

"name" : "user1",

"age" : 15,

"address" : [

"address1",

"address2"

]

}

MongoDB 支持以 “.” 分割的 namespace 路径?但需要注意 key 不能以

“$” 开头?不能包含 “.” 字符 (条件表达式中的多级路径须用引号)。

> u = db.users.findOne({address:"address1"}) {

"_id" : ObjectId("4c479885089df9b53474170a"),

"name" : "user1",

"age" : 15,

"address" : [

"address1",

"address2"

]

}

> u.im = {msn:"user1@hotmail.com", qq:12345678} { "msn" : "user1@hotmail.com", "qq" : 12345678 }

> db.users.save(u)

> u = db.users.findOne({"im.qq":12345678}) {

"_id" : ObjectId("4c479885089df9b53474170a"),

"name" : "user1",

"age" : 15,

"address" : [

"address1",

"address2"

],

"im" : {

"msn" : "user1@hotmail.com",

"qq" : 12345678

}

> u.im.qq

12345678

> u.im.msn

user1@hotmail.com

> db.users.update({"im.qq":12345678}, {$set:{"im.qq":12345}})

> u = db.users.findOne({"im.qq":12345}) {

"_id" : ObjectId("4c479885089df9b53474170a"),

"name" : "user1",

"age" : 15,

"address" : [

"address1",

"address2"

],

"im" : {

"msn" : "user1@hotmail.com",

"qq" : 12345

}

> u = db.users.find({"im.qq":{$exists:true}}, {"im.qq":1})

{ "_id" : ObjectId("4c479885089df9b53474170a"), "im" : { "qq" : 12345 } }

注意: 由于每篇文档都包含完整的 key 数据?因此使用尽可能短的 key 可以

有效节省存储空间。

3. Operator

(1) $all: 判断数组属性是否包含全部条件。

> db.users.insert({name:"user3", data:[1,2,3,4,5,6,7]}) > db.users.insert({name:"user4", data:[1,2,3]})

> db.users.find({data:{$all:[2,3,4]}})

{ "_id" : ObjectId("4c47a133b48cde79c6780df0"), "name" : "user3", "data" :

[ 1, 2, 3, 4, 5, 6, 7 ] }

注意和 $in 的区别。$in 是检查目标属性值是条件表达式中的一员?而 $all

则要求属性值包含全部条件元素。

(2) $size: 匹配数组属性元素数量。

> db.users.insert({name:"user3", data:[1,2,3,4,5,6,7]}) > db.users.insert({name:"user4", data:[1,2,3]})

> db.users.find({data:{$size:3}})

{ "_id" : ObjectId("4c47a13bb48cde79c6780df1"), "name" : "user4", "data" :

[ 1, 2, 3 ] }

(3) $type: 判断属性类型。

> db.users.insert({name:"user5", t:1})

> db.users.insert({name:"user6", t:1.34})

> db.users.insert({name:"user7", t:"abc"})

> db.users.find({t:{$type:1}})

{ "_id" : ObjectId("4c47a231b48cde79c6780df2"), "name" : "user5", "t" :

1 }

{ "_id" : ObjectId("4c47a23eb48cde79c6780df3"), "name" : "user6", "t" :

1.34 }

> db.users.find({t:{$type:2}})

{ "_id" : ObjectId("4c47a258b48cde79c6780df4"), "name" : "user7", "t" :

"abc" }

类型值:

; double:1

; string: 2

; object: 3

; array: 4

; binary data: 5

; object id: 7

; boolean: 8

; date: 9

; null: 10

; regular expression: 11

; javascript code: 13

; symbol: 14

; javascript code with scope: 15

; 32-bit integer: 16

; timestamp: 17

; 64-bit integer: 18

; min key: 255

; max key: 127

(4) 使用正则表达式进行查询。

> db.users.find({name:/user[135]/i}, {name:1})

{ "_id" : ObjectId("4c479885089df9b53474170a"), "name" : "user1" } { "_id" : ObjectId("4c47a133b48cde79c6780df0"), "name" : "user3" } { "_id" : ObjectId("4c47a231b48cde79c6780df2"), "name" : "user5" }

>>> users = db.users.find({"name" : {"$regex" : r"(?i)user[135]"}}, ["name"])

>>> for u in users: print u

...

{u'_id': ObjectId('4c479885089df9b53474170a'), u'name': u'user1'} {u'_id': ObjectId('4c47a133b48cde79c6780df0'), u'name': u'user3'} {u'_id': ObjectId('4c47a231b48cde79c6780df2'), u'name': u'user5'} 正则表达式标记:

i: 忽略大小写。

m: 默认为单行处理?此标记表示多行。

x: 扩展。

(5) 数组属性元素值匹配。

> db.users.find({data:"abc"})

{ "_id" : ObjectId("4c47a481b48cde79c6780df5"), "name" : "user8", "data" : [ { "a" : 1, "b" : 10 }, 3, "abc" ] }

> db.users.find({data:{$elemMatch:{a:1, b:{$gt:5}}}}) { "_id" : ObjectId("4c47a481b48cde79c6780df5"), "name" : "user8", "data" : [ { "a" : 1, "b" : 10 }, 3, "abc" ] }

{data:”abc”} 仅简单匹配数组属性是否包含该元素。$elemMatch 则可以处理

更复杂的元素查找条件。当然也可以写成如下方式。

> db.users.find({"data.a":1, "data.b":{$gt:5}})

{ "_id" : ObjectId("4c47a481b48cde79c6780df5"), "name" : "user8", "data" : [ { "a" : 1, "b" : 10 }, 3, "abc" ] }

还可以直接使用序号进行操作。

> db.users.find({"data.2":3})

{ "_id" : ObjectId("4c47a133b48cde79c6780df0"), "name" : "user3", "data" : [ 1, 2, 3, 4, 5, 6, 7 ] }

{ "_id" : ObjectId("4c47a13bb48cde79c6780df1"), "name" : "user4", "data" : [ 1, 2, 3 ] }

(6) $not: 取反?表示返回条件不成立的文档。

似乎只能跟正则和 $mod 一起使用????

> u = db.users.find({name:{$not:/user3/}}, {name:1})

{ "_id" : ObjectId("4c479885089df9b53474170a"), "name" : "user1" } { "_id" : ObjectId("4c47a13bb48cde79c6780df1"), "name" : "user4" } { "_id" : ObjectId("4c47a231b48cde79c6780df2"), "name" : "user5" } { "_id" : ObjectId("4c47a23eb48cde79c6780df3"), "name" : "user6" } { "_id" : ObjectId("4c47a258b48cde79c6780df4"), "name" : "user7" } { "_id" : ObjectId("4c47a481b48cde79c6780df5"), "name" : "user8" } { "_id" : ObjectId("4c479896089df9b53474170b"), "name" : "user2" } (7) $unset: 和 $set 相反?表示移除文档属性。

> u = db.users.find({name:"user1"})

{ "_id" : ObjectId("4c479885089df9b53474170a"), "name" : "user1", "age" : 15, "address" : [ "address1", "address2" ], "im" : { "msn" : "user1@hotmail.com", "qq" : 12345 } }

> db.users.update({name:"user1"}, {$unset:{address:1, im:1}})

> u = db.users.find({name:"user1"})

{ "_id" : ObjectId("4c479885089df9b53474170a"), "age" : 15, "name" : "user1" }

(8) $push: 和 $ pushAll 都是向数组属性添加元素。

> u = db.users.find({name:"user1"})

{ "_id" : ObjectId("4c479885089df9b53474170a"), "age" : 15, "name" : "user1" }

> db.users.update({name:"user1"}, {$push:{data:1}})

> u = db.users.find({name:"user1"})

{ "_id" : ObjectId("4c479885089df9b53474170a"), "age" : 15, "data" : [ 1 ], "name" : "user1" }

> db.users.update({name:"user1"}, {$pushAll:{data:[2,3,4,5]}})

> u = db.users.find({name:"user1"})

{ "_id" : ObjectId("4c479885089df9b53474170a"), "age" : 15, "data" : [ 1, 2, 3, 4, 5 ], "name" : "user1" }

(9) $addToSet: 和 $push 类似?不过仅在该元素不存在时才添加 (Set 表示不

重复元素集合)。

> db.users.update({name:"user2"}, {$addToSet:{data:1}})

> u = db.users.find({name:"user2"})

{ "_id" : ObjectId("4c479896089df9b53474170b"), "data" : [ 1 ], "name" : "user2" }

> db.users.update({name:"user2"}, {$push:{data:1}})

> u = db.users.find({name:"user2"})

{ "_id" : ObjectId("4c479896089df9b53474170b"), "data" : [ 1, 1 ], "name" : "user2" }

要添加多个元素?使用 $each。

> db.users.update({name:"user2"},

{$addToSet:{data:{$each:[1,2,3,4]}}})

> u = db.users.find({name:"user2"})

{ "_id" : ObjectId("4c479896089df9b53474170b"), "data" : [ 1, 2, 3, 4 ], "name" : "user2" }

(10) $pop: 移除数组属性的元素?$pull 按值移除?$pullAll 移除所有符合提

交的元素。

> u = db.users.find({name:"user3"})

{ "_id" : ObjectId("4c47a133b48cde79c6780df0"), "data" : [ 1, 2, 3, 4, 5, 6, 7, 2, 3 ], "name" : "user3" }

> db.users.update({name:"user3"}, {$pop:{data:1}}) // 移除最后一个元素

> u = db.users.find({name:"user3"})

{ "_id" : ObjectId("4c47a133b48cde79c6780df0"), "data" : [ 1, 2, 3, 4, 5, 6, 7, 2 ], "name" : "user3" }

> db.users.update({name:"user3"}, {$pop:{data:-1}}) // 移除第一个元素

> u = db.users.find({name:"user3"})

{ "_id" : ObjectId("4c47a133b48cde79c6780df0"), "data" : [ 2, 3, 4, 5, 6, 7, 2 ], "name" : "user3" }

> db.users.update({name:"user3"}, {$pull:{data:2}}) // 移除全部 2

> u = db.users.find({name:"user3"})

{ "_id" : ObjectId("4c47a133b48cde79c6780df0"), "data" : [ 3, 4, 5, 6, 7 ], "name" : "user3" }

> db.users.update({name:"user3"}, {$pullAll:{data:[4,5,6]}}) // 移除

4,5,6

> u = db.users.find({name:"user3"})

{ "_id" : ObjectId("4c47a133b48cde79c6780df0"), "data" : [ 3, 7 ], "name" : "user3" }

(11) $where: 用 JS 代码来代替有些丑陋的 $lt、$gt。

MongoDB 内置了 Javascript Engine (SpiderMonkey)。可直接使用 JS

Expression?甚至使用 JS Function 写更复杂的 Code Block。

> for (var i = 0; i < 10; i++) db.users.insert({name:"user"+i, age:i})

> db.users.find()

{ "_id" : ObjectId("4c47b3372a9b2be866da226e"), "name" : "user0", "age" : 0 }

{ "_id" : ObjectId("4c47b3372a9b2be866da226f"), "name" : "user1", "age" : 1 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2270"), "name" : "user2", "age" : 2 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2271"), "name" : "user3", "age" : 3 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2272"), "name" : "user4", "age" : 4 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2273"), "name" : "user5", "age" : 5 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2274"), "name" : "user6", "age" : 6 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2275"), "name" : "user7", "age" : 7 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2276"), "name" : "user8", "age" : 8 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2277"), "name" : "user9", "age" : 9 }

> db.users.find({$where:"this.age > 7 || this.age < 3"})

{ "_id" : ObjectId("4c47b3372a9b2be866da226e"), "name" : "user0", "age" : 0 }

{ "_id" : ObjectId("4c47b3372a9b2be866da226f"), "name" : "user1", "age" : 1 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2270"), "name" : "user2", "age" : 2 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2276"), "name" : "user8", "age" : 8 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2277"), "name" : "user9", "age" : 9 }

> db.users.find("this.age > 7 || this.age < 3")

{ "_id" : ObjectId("4c47b3372a9b2be866da226e"), "name" : "user0", "age" : 0 }

{ "_id" : ObjectId("4c47b3372a9b2be866da226f"), "name" : "user1", "age" : 1 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2270"), "name" : "user2", "age" : 2 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2276"), "name" : "user8", "age" : 8 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2277"), "name" : "user9", "age" : 9 }

> db.users.find({$where: function(){ return this.age > 7 || this.age < 3;}})

{ "_id" : ObjectId("4c47b3372a9b2be866da226e"), "name" : "user0", "age" : 0 }

{ "_id" : ObjectId("4c47b3372a9b2be866da226f"), "name" : "user1", "age" : 1 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2270"), "name" : "user2", "age" : 2 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2276"), "name" : "user8", "age" : 8 }

{ "_id" : ObjectId("4c47b3372a9b2be866da2277"), "name" : "user9", "age" : 9 }

>>> for u in db.users.find({"$where":"this.age > 7 || this.age < 3"}): print u

...

{u'age': 0.0, u'_id': ObjectId('4c47b3372a9b2be866da226e'), u'name': u'user0'}

{u'age': 1.0, u'_id': ObjectId('4c47b3372a9b2be866da226f'), u'name': u'user1'}

{u'age': 2.0, u'_id': ObjectId('4c47b3372a9b2be866da2270'), u'name': u'user2'}

{u'age': 8.0, u'_id': ObjectId('4c47b3372a9b2be866da2276'), u'name': u'user8'}

{u'age': 9.0, u'_id': ObjectId('4c47b3372a9b2be866da2277'), u'name': u'user9'}

>>> for u in db.users.find().where("this.age > 7 || this.age < 3"): print u

...

{u'age': 0.0, u'_id': ObjectId('4c47b3372a9b2be866da226e'), u'name': u'user0'}

{u'age': 1.0, u'_id': ObjectId('4c47b3372a9b2be866da226f'), u'name': u'user1'}

{u'age': 2.0, u'_id': ObjectId('4c47b3372a9b2be866da2270'), u'name': u'user2'}

{u'age': 8.0, u'_id': ObjectId('4c47b3372a9b2be866da2276'), u'name': u'user8'}

{u'age': 9.0, u'_id': ObjectId('4c47b3372a9b2be866da2277'), u'name': u'user9'}

>>> for u in db.users.find().where("function() { return this.age > 7 || this.age < 3;}"): print u

...

{u'age': 0.0, u'_id': ObjectId('4c47b3372a9b2be866da226e'), u'name': u'user0'}

{u'age': 1.0, u'_id': ObjectId('4c47b3372a9b2be866da226f'), u'name': u'user1'}

{u'age': 2.0, u'_id': ObjectId('4c47b3372a9b2be866da2270'), u'name': u'user2'}

{u'age': 8.0, u'_id': ObjectId('4c47b3372a9b2be866da2276'), u'name': u'user8'}

DOCSFORD

dqMongoDB 3. Schema Designaq