本文對原文進行了格式化和排版操作,作者大神講得非常清楚。mongodb_修改器(set/push/$pop/upsert…)
mongodb CRUD 增刪改查一應俱全 Mark一下。希望能幫到更多的人。
原文:https://blog.csdn.net/MCpang/article/details/7752736 ,
對於文檔的更新除替換外,針對某個或多個文檔只需要部分更新可使用原子的更新修改器,能夠高效的進行文檔更新。更新修改器是中特殊的鍵,
用來指定複雜的操作,比如增加、刪除或者調整鍵,還可能是操作數組或者內嵌文檔。
1.$inc
這個修改器幹什麼使的呢?看看下面示例的具體操作後的結果即可知道。
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"},{"$inc":{"size" : -1}})
> db.b.find()
{ "_id" : ObjectId("5003b6135af21ff428dafbe6"),
"uid" : "201203",
"type" : "1",
"size" : 12
}
得出結論:修改器inc修改器之後,還是一樣嗎?)
2.$set
用來指定一個鍵並更新鍵值,若鍵不存在並創建。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"},
{"$set": {"sname":["java",".net","c++"]} }
)
> db.a.findOne({"uid" : "20120002","type" : "3"})
{
"_id" : ObjectId("500216de81b954b6161a7d8f"),
"desc" : "hello world2!",
"num" : 40,
"size" : 10,
"sname" : [
"java",
".net",
"c++"
],
"type" : "3",
"uid" : "20120002"
}
對於內嵌的文檔,$set又是如何進行更新的內嵌的文檔的呢,請看下面的示例:
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:對於內嵌文檔在使用$set更新時,使用"."連接的方式。
3.$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"
}
得出結論:使用修改器$unset時,不論對目標鍵使用1、0、-1或者具體的字符串等都是可以刪除該目標鍵。
4.數組修改器–$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一個當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" },
{$push : {"title":"t2"} }
)
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"),
"name" : "toyota",
"size" : {
"height" : 8,
"width" : 7,
"length" : 15 },
"title" : [ "t1", "t2", "t2" ],
"type" : "suv"
}
–再向一個已經存在的鍵值非數組類型的鍵push一個值
> db.c.update(
{"name" : "toyota"},
{$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
得出結論:$push–向文檔的某個數組類型的鍵添加一個數組元素,不過濾重複的數據。添加時鍵存在,要求鍵值類型必須是數組;鍵不存在,則創建數組類型的鍵。
5.數組修改器–addToSet
主要給數組類型鍵值添加一個元素時,避免在數組中產生重複數據,$ne在有些情況是不通行的。
> db.c.update(
{"title": {$ne:"t2"} }, #如果有重複的t2則不執行操作
{$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"},
{$addToSet:{"title":"t2"}} #如果有重複的t2則不執行操作
)
> db.c.find()
{ "_id" : ObjectId("5003be465af21ff428dafbe7"),
"name" : "toyota",
"size" : {
"height" : 8,
"width" : 7,
"length" : 15
},
"title" : [ "t1", "t2", "t2" ],
"type" : "suv"
}
相當於$ne是在選擇的時機執行,而addToSet是在添加的時候執行。
6.數組修改器–pull
$pop從數組的頭或者尾刪除數組中的元素,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" },
{ $pull : {"title":"t2"} }
)
> db.c.find()
{
"_id" : ObjectId("5003be465af21ff428dafbe7"),
"name" : "toyota",
"size" :
{
"height" : 8,
"width" : 7,
"length" : 15
},
"title" : [ "t1", "t3" ],
"type" : "suv"
}
7.數組的定位修改器
在需要對數組中的值進行操作的時候,可通過位置或者定位操作符("$").數組是0開始的,可以直接將下標作爲鍵來選擇元素。
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.$.size":1}}
)
> db.c.find({"uid":"001"})
{
"_id" : ObjectId("5003da405af21ff428dafbe8"),
"uid" : "001",
"comments" :
[
{"name" : "t1", "size" : 1 },
{"name" : "t2", "size" : 12}
]
}
–若爲多個文檔滿足條件,則只更新第一個文檔。
8.upsert
upsert是一種特殊的更新。當沒有符合條件的文檔,就以這個條件和更新文檔爲基礎創建一個新的文檔,如果找到匹配的文檔就正常的更新。
使用upsert,既可以避免競態問題,也可以減少代碼量(update的第三個參數就表示這個upsert,參數爲true時)
> db.c.remove()
> db.c.update({"size":11},{$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
1.可以在文檔不存在的時候插入,存在的時候更新,只有一個參數文檔。
2.要是文檔含有"_id",會調用upsert。否則,會調用插入。
> 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"
}