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

青旅半醒 2022-07-15 13:09 120阅读 0赞

对于文档的更新除替换外，针对某个或多个文档只需要部分更新可使用原子的更新修改器，能够高效的进行文档更新。更新修改器是中特殊的键，  
用来指定复杂的操作，比如增加、删除或者调整键，还可能是操作数组或者内嵌文档。

1.$inc  
\--------------------------------------------------------------------------  
这个修改器干什么使的呢？看看下面示例的具体操作后的结果即可知道。

示例文档：\{"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 \}

得出结论：修改器$inc可以对文档的某个值为数字型（只能为满足要求的数字）的键进行增减的操作。  
（这里有个问题：上篇中说到更新默认只对满足条件的记录集中第一个文档进行更新，那么使用$inc修改器之后，还是一样吗？）

2.$set  
\-------------------------------------------------------------------  
用来指定一个键并更新键值，若键不存在并创建。来看看下面的效果：

> db.a.findOne(\{"uid" : "20120002","type" : "3"\})  
\{ "\_id" : ObjectId("500216de81b954b6161a7d8f"), "desc" : "hello world2!", "num"  
: 40, "sname" : "jk", "type" : "3", "uid" : "20120002" \}  
\--size键不存在的场合  
> db.a.update(\{"uid" : "20120002","type" : "3"\},\{"$set":\{"size":10\}\})  
> db.a.findOne(\{"uid" : "20120002","type" : "3"\})  
\{ "\_id" : ObjectId("500216de81b954b6161a7d8f"), "desc" : "hello world2!", "num"  
: 40, "size" : 10, "sname" : "jk", "type" : "3", "uid" : "20120002" \}  
\--sname键存在的场合  
> db.a.update(\{"uid" : "20120002","type" : "3"\},\{"$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" \}  
\--可改变键的值类型  
> 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"  
\}

对于内嵌的文档，$set又是如何进行更新的内嵌的文档的呢，请看下面的示例：  
示例文档：\{"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  
        \}  
\}  
可见：对于内嵌文档在使用$set更新时，使用"."连接的方式。

3.$unset  
\----------------------------------------------------------------  
从字面就可以看出其意义，主要是用来删除键。  
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"  
\}

得出结论：使用修改器$unset时，不论对目标键使用1、0、-1或者具体的字符串等都是可以删除该目标键。

4.数组修改器--$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一个当前文档中不存在的键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一个值  
> 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一个值  
> 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" \}

\--再向一个已经存在的键值非数组类型的键push一个值  
> 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

得出结论：$push--向文档的某个数组类型的键添加一个数组元素，不过滤重复的数据。添加时键存在，要求键值类型必须是数组；键不存在，则创建数组类型的键。

5.数组修改器--$ne/$addToSet  
\---------------------------------------------------------------------  
主要给数组类型键值添加一个元素时，避免在数组中产生重复数据，$ne在有些情况是不通行的。

> 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.数组修改器--$pop、$pull  
\------------------------------------------------------------  
$pop从数组的头或者尾删除数组中的元素，示例如下：  
\{ "\_id" : ObjectId("5003be465af21ff428dafbe7"), "name" : "toyota", "size" : \{ "height" : 8,  
 "width" : 7, "length" : 15 \}, "title" : \[ "t1", "t2", "t3", "t4" \],"type" : "suv" \}

\--从数组的尾部删除 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" \}  
\--从数组的头部 -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" \}  
\--从数组的尾部删除 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从数组中删除满足条件的元素，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.数组的定位修改器  
\-------------------------------------------------------------------  
在需要对数组中的值进行操作的时候，可通过位置或者定位操作符（"$"）.数组是0开始的，可以直接将下标作为键来选择元素。  
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" : \[ \{  
"name" : "t1", "size" : 1 \}, \{ "name" : "t2", "size" : 12 \} \] \}

\--若为多个文档满足条件，则只更新第一个文档。

8.upsert  
\-----------------------------------------------------------------  
upsert是一种特殊的更新。当没有符合条件的文档，就以这个条件和更新文档为基础创建一个新的文档，如果找到匹配的文档就正常的更新。  
使用upsert，既可以避免竞态问题，也可以减少代码量（update的第三个参数就表示这个upsert，参数为true时）

> 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函数  
\-----------------------------------------------------------------  
1.可以在文档不存在的时候插入，存在的时候更新，只有一个参数文档。  
2.要是文档含有"\_id"，会调用upsert。否则，会调用插入。  
> 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" \}

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