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mongodb 修改器（$inc/$set/$unset/$push/$pop/upsert)

對(duì)于文檔的更新除替換外，針對(duì)某個(gè)或多個(gè)文檔只需要部分更新可使用原子的更新修改器，能夠高效的進(jìn)行文檔更新。更新修改器是中特殊的鍵，
用來指定復(fù)雜的操作，比如增加、刪除或者調(diào)整鍵，還可能是操作數(shù)組或者內(nèi)嵌文檔。

1.$inc

這個(gè)修改器干什么使的呢？看看下面示例的具體操作后的結(jié)果即可知道。
示例文檔：{"uid":"201203","type":"1",size:10}

> db.b.insert({"uid":"201203","type":"1",size:10})
> db.b.find()
{ "_id" : ObjectId("5003b6135af21ff428dafbe6"), "uid" : "201203", "type" : "1",
"size" : 10 }
> db.b.update({"uid" : "201203"},{"$inc":{"size" : 1}})
> db.b.find()
{ "_id" : ObjectId("5003b6135af21ff428dafbe6"), "uid" : "201203", "type" : "1",
"size" : 11 }
> db.b.update({"uid" : "201203"},{"$inc":{"size" : 2}})
> db.b.find()
{ "_id" : ObjectId("5003b6135af21ff428dafbe6"), "uid" : "201203", "type" : "1",
"size" : 13 }
> db.b.update({"uid" : "201203"},{"$inc":{"size" : -1}})
> db.b.find()
{ "_id" : ObjectId("5003b6135af21ff428dafbe6"), "uid" : "201203", "type" : "1",
"size" : 12 }

得出結(jié)論：修改器$inc可以對(duì)文檔的某個(gè)值為數(shù)字型（只能為滿足要求的數(shù)字）的鍵進(jìn)行增減的操作。
（這里有個(gè)問題：上篇中說到更新默認(rèn)只對(duì)滿足條件的記錄集中第一個(gè)文檔進(jìn)行更新，那么使用$inc修改器之后，還是一樣嗎？）

2.$set

用來指定一個(gè)鍵并更新鍵值，若鍵不存在并創(chuàng)建。來看看下面的效果：

> db.a.findOne({"uid" : "20120002","type" : "3"})
{ "_id" : ObjectId("500216de81b954b6161a7d8f"), "desc" : "hello world2!", "num"
: 40, "sname" : "jk", "type" : "3", "uid" : "20120002" }
--size鍵不存在的場(chǎng)合
> db.a.update({"uid" : "20120002","type" : "3"},{"$set":{"size":10}})
> db.a.findOne({"uid" : "20120002","type" : "3"})
{ "_id" : ObjectId("500216de81b954b6161a7d8f"), "desc" : "hello world2!", "num"
: 40, "size" : 10, "sname" : "jk", "type" : "3", "uid" : "20120002" }
--sname鍵存在的場(chǎng)合
> db.a.update({"uid" : "20120002","type" : "3"},{"$set":{"sname":"ssk"}})
> db.a.find()
{ "_id" : ObjectId("500216de81b954b6161a7d8f"), "desc" : "hello world2!", "num"
: 40, "size" : 10, "sname" : "ssk", "type" : "3", "uid" : "20120002" }
{ "_id" : ObjectId("50026affdeb4fa8d154f8572"), "desc" : "hello world1!", "num"
: 50, "sname" : "jk", "type" : "1", "uid" : "20120002" }
--可改變鍵的值類型
> db.a.update({"uid" : "20120002","type" : "3"},{"$set":{"sname":["Java",".net","c++"]}})
> db.a.findOne({"uid" : "20120002","type" : "3"})
{
  "_id" : ObjectId("500216de81b954b6161a7d8f"),
  "desc" : "hello world2!",
  "num" : 40,
  "size" : 10,
  "sname" : [
    "java",
    ".net",
    "c++"
  ],
  "type" : "3",
  "uid" : "20120002"
}

對(duì)于內(nèi)嵌的文檔，$set又是如何進(jìn)行更新的內(nèi)嵌的文檔的呢，請(qǐng)看下面的示例：
示例文檔：{"name":"toyota","type":"suv","size":{"height":10,"width":5,"length":15}}

> db.c.findOne({"name":"toyota"})
{
  "_id" : ObjectId("5003be465af21ff428dafbe7"),
  "name" : "toyota",
  "type" : "suv",
  "size" : {
    "height" : 10,
    "width" : 5,
    "length" : 15
  }
}
> db.c.update({"name":"toyota"},{"$set":{"size.height":8}})
> db.c.findOne({"name":"toyota"})
{
  "_id" : ObjectId("5003be465af21ff428dafbe7"),
  "name" : "toyota",
  "type" : "suv",
  "size" : {
    "height" : 8,
    "width" : 5,
    "length" : 15
  }
}
> db.c.update({"name":"toyota"},{"$set":{"size.width":7}})
> db.c.findOne({"name":"toyota"})
{
  "_id" : ObjectId("5003be465af21ff428dafbe7"),
  "name" : "toyota",
  "type" : "suv",
  "size" : {
    "height" : 8,
    "width" : 7,
    "length" : 15
  }
}

可見：對(duì)于內(nèi)嵌文檔在使用$set更新時(shí)，使用"."連接的方式。

3.$unset

從字面就可以看出其意義，主要是用來刪除鍵。
示例操作效果如下：

> db.a.update({"uid" : "20120002","type" : "3"},{"$unset":{"sname":1}})
> db.a.findOne({"uid" : "20120002","type" : "3"})
{
  "_id" : ObjectId("500216de81b954b6161a7d8f"),
  "desc" : "hello world2!",
  "num" : 40,
  "size" : 10,
  "type" : "3",
  "uid" : "20120002"
}
> db.a.update({"uid" : "20120002","type" : "3"},{"$unset":{"num":0}})
> db.a.findOne({"uid" : "20120002","type" : "3"})
{
  "_id" : ObjectId("500216de81b954b6161a7d8f"),
  "desc" : "hello world2!",
  "size" : 10,
  "type" : "3",
  "uid" : "20120002"
}
> db.a.update({"uid" : "20120002","type" : "3"},{"$unset":{"size":-1}})
> db.a.findOne({"uid" : "20120002","type" : "3"})
{
  "_id" : ObjectId("500216de81b954b6161a7d8f"),
  "desc" : "hello world2!",
  "type" : "3",
  "uid" : "20120002"
}
> db.a.update({"uid" : "20120002","type" : "3"},{"$unset":{"desc":"sssssss"}})
> db.a.findOne({"uid" : "20120002","type" : "3"})
{
  "_id" : ObjectId("500216de81b954b6161a7d8f"),
  "type" : "3",
  "uid" : "20120002"
}

得出結(jié)論：使用修改器$unset時(shí)，不論對(duì)目標(biāo)鍵使用1、0、-1或者具體的字符串等都是可以刪除該目標(biāo)鍵。

4.數(shù)組修改器--$push

示例操作效果如下：

> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "type" : "suv",
"size" : { "height" : 8, "width" : 7, "length" : 15 } }
--先push一個(gè)當(dāng)前文檔中不存在的鍵title
> db.c.update({"name" : "toyota"},{$push:{"title":"t1"}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1" ], "type" : "suv" }
 
--再向title中push一個(gè)值
> db.c.update({"name" : "toyota"},{$push:{"title":"t2"}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1", "t2" ], "type" : "suv" }
--再向title中push一個(gè)值
> db.c.update({"name" : "toyota"},{$push:{"title":"t2"}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1", "t2", "t2" ], "type" : "suv" }
--再向一個(gè)已經(jīng)存在的鍵值非數(shù)組類型的鍵push一個(gè)值
> db.c.update({"name" : "toyota"},{$push:{"size.height":10}})
Cannot apply $push/$pushAll modifier to non-array
> db.c.update({"name" : "toyota"},{$push:{"name":"ddddddd"}})
Cannot apply $push/$pushAll modifier to non-array

得出結(jié)論：$push--向文檔的某個(gè)數(shù)組類型的鍵添加一個(gè)數(shù)組元素，不過濾重復(fù)的數(shù)據(jù)。添加時(shí)鍵存在，要求鍵值類型必須是數(shù)組；鍵不存在，則創(chuàng)建數(shù)組類型的鍵。

5.數(shù)組修改器--$ne/$addToSet

主要給數(shù)組類型鍵值添加一個(gè)元素時(shí)，避免在數(shù)組中產(chǎn)生重復(fù)數(shù)據(jù)，$ne在有些情況是不通行的。

> db.c.update({"title" : {$ne:"t2"}},{$push:{"title":"t2"}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1", "t2", "t2" ], "type" : "suv" }
> db.c.update({"name" : "toyota"},{$addToSet:{"title":"t2"}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1", "t2", "t2" ], "type" : "suv" }

6.數(shù)組修改器--$pop、$pull

$pop從數(shù)組的頭或者尾刪除數(shù)組中的元素，示例如下：

{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1", "t2", "t3", "t4" ],"type" : "suv" }
--從數(shù)組的尾部刪除 1
> db.c.update({"name" : "toyota"},{$pop:{"title":1}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1", "t2", "t3" ], "type" : "suv" }
--從數(shù)組的頭部 -1
> db.c.update({"name" : "toyota"},{$pop:{"title":-1}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t2", "t3" ], "type" : "suv" }
--從數(shù)組的尾部刪除 0
> db.c.update({"name" : "toyota"},{$pop:{"title":0}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t2" ], "type" : "suv" }
 
$pull從數(shù)組中刪除滿足條件的元素，示例如下：
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1", "t2", "t2", "t3" ],"type" : "suv" }
 
> db.c.update({"name" : "toyota"},{$pull:{"title":"t2"}})
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : { "height" : 8,
 "width" : 7, "length" : 15 }, "title" : [ "t1", "t3" ], "type" : "suv" }

7.數(shù)組的定位修改器

在需要對(duì)數(shù)組中的值進(jìn)行操作的時(shí)候，可通過位置或者定位操作符（"$"）.數(shù)組是0開始的，可以直接將下標(biāo)作為鍵來選擇元素。
示例如下：

{"uid":"001",comments:[{"name":"t1","size":10},{"name":"t2","size":12}]}
> db.c.find({"uid":"001"})
{ "_id" : ObjectId("5003da405af21ff428dafbe8"), "uid" : "001", "comments" : [ {
"name" : "t1", "size" : 10 }, { "name" : "t2", "size" : 12 } ] }
> db.c.update({"uid":"001"},{$inc:{"comments.0.size":1}})
> db.c.find({"uid":"001"})
{ "_id" : ObjectId("5003da405af21ff428dafbe8"), "uid" : "001", "comments" : [ {
"name" : "t1", "size" : 11 }, { "name" : "t2", "size" : 12 } ] }
> db.c.update({"comments.name":"t1"},{$set:{"comments.$.size":1}})
> db.c.find({"uid":"001"})
{ "_id" : ObjectId("5003da405af21ff428dafbe8"), "uid" : "001", "comments" : [ {
"name" : "t1", "size" : 1 }, { "name" : "t2", "size" : 12 } ] }
--若為多個(gè)文檔滿足條件，則只更新第一個(gè)文檔。

8.upsert

upsert是一種特殊的更新。當(dāng)沒有符合條件的文檔，就以這個(gè)條件和更新文檔為基礎(chǔ)創(chuàng)建一個(gè)新的文檔，如果找到匹配的文檔就正常的更新。
使用upsert，既可以避免競(jìng)態(tài)問題，也可以減少代碼量（update的第三個(gè)參數(shù)就表示這個(gè)upsert，參數(shù)為true時(shí)）

> db.c.remove()
> db.c.update({"size":11},{$inc:{"size":3}})
> db.c.find()
> db.c.update({"size":11},{$inc:{"size":3}},false)
> db.c.find()
> db.c.update({"size":11},{$inc:{"size":3}},true)
> db.c.find()
{ "_id" : ObjectId("5003ded6c28f67507a6df1de"), "size" : 14 }

9.save函數(shù)

1.可以在文檔不存在的時(shí)候插入，存在的時(shí)候更新，只有一個(gè)參數(shù)文檔。
2.要是文檔含有"_id"，會(huì)調(diào)用upsert。否則，會(huì)調(diào)用插入。

> db.a.find()
{ "_id" : ObjectId("50026affdeb4fa8d154f8572"), "desc" : "hello world1!", "num": 50,
 "sname" : "jk", "type" : "1", "uid" : "20120002" }
> var o = db.a.findOne()
> o.num = 55
55
> db.a.save(o)
> db.a.find()
{ "_id" : ObjectId("50026affdeb4fa8d154f8572"), "desc" : "hello world1!", "num": 55,
 "sname" : "jk", "type" : "1", "uid" : "20120002" }

標(biāo)簽：銅川湘潭崇左湖南仙桃黃山衡水蘭州

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