MongoDB修改器
在mongodb中通常文档只会有一部分要更新，利用原子的更新修改器，可以做到只更新文档的一部分键值，而且更新极为高效，更新修改器是种特殊的键，用来指定复杂的更新操作，比如调整、增加、或者删除键，还可以操作数组和内嵌文档。增加、修改或删除键的时候，应该使用$修改器
1. $set修改器
$set修改器用来指定一个键值. 如果这个键不存在, 则创建它,它对于更新模式或者用户定义键来说很方便.
> db.users.findOne() { "_id" : ObjectId("56fe7df8b322e3ff1dabf834"), "name" : "joe", "age" : 30, "sex" : "male", "location" : "Wisconsin", "favorite book" : "war and pace" } > db.users.update({"name":"joe"},{"$set":{"favorite book":["cat's cardle","foundation trilogy","ender's game"]}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.findOne() { "_id" : ObjectId("56fe7df8b322e3ff1dabf834"), "name" : "joe", "age" : 30, "sex" : "male", "location" : "Wisconsin", "favorite book" : [ "cat's cardle", "foundation trilogy", "ender's game" ] }
2. $set用来修改内嵌文档
> db.blog.insert({"title":"a blog post","author":{"name":"joe","email":"joe@example.com"}})
WriteResult({ "nInserted" : 1 })
> db.blog.findOne()
{
"_id" : ObjectId("57709da84f533aa7535d46d3"),
"title" : "a blog post",
"author" : {
"name" : "joe",
"email" : "joe@example.com"
}
}
> db.blog.update({"author.name":"joe"},{"$set":{"author.name":"joe schmoe"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.blog.findOne()
{
"_id" : ObjectId("57709da84f533aa7535d46d3"),
"title" : "a blog post",
"author" : {
"name" : "joe schmoe",
"email" : "joe@example.com"
}
}
> db.blog.update({"title":"a blog post"},{"$set":{"author.name":"joe schmoe op"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.blog.findOne()
{
"_id" : ObjectId("57709da84f533aa7535d46d3"),
"title" : "a blog post",
"author" : {
"name" : "joe schmoe op",
"email" : "joe@example.com"
}
}
3. $unset修改器
$unset修改用于将键删除
> db.users.findOne() { "_id" : ObjectId("56fe7df8b322e3ff1dabf834"), "name" : "joe", "age" : 30, "sex" : "male", "location" : "Wisconsin", "favorite book" : [ "cat's cardle", "foundation trilogy", "ender's game" ] } > db.users.update({"name":"joe"},{"$unset":{"favorite book":1}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.findOne() { "_id" : ObjectId("56fe7df8b322e3ff1dabf834"), "name" : "joe", "age" : 30, "sex" : "male", "location" : "Wisconsin" }
4. $inc修改器
$inc其用来增加或减少已有的键的键值，或者在键不存在的时候创建一个键。
> db.games.insert({"game":"pinball","user":"joe"})
WriteResult({ "nInserted" : 1 })
> db.games.findOne()
{
"_id" : ObjectId("5770a1394f533aa7535d46d4"),
"game" : "pinball",
"user" : "joe"
}
> db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":50}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.games.findOne()
{
"_id" : ObjectId("5770a1394f533aa7535d46d4"),
"game" : "pinball",
"user" : "joe",
"score" : 50
}
为"score"键增加50再减少20
> db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":50}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.games.findOne()
{
"_id" : ObjectId("5770a1394f533aa7535d46d4"),
"game" : "pinball",
"user" : "joe",
"score" : 100
}
> db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":-20}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.games.findOne()
{
"_id" : ObjectId("5770a1394f533aa7535d46d4"),
"game" : "pinball",
"user" : "joe",
"score" : 80
}
以上"$inc"与"$set"的用法类似，就是专门用来增加或减少数字的。"$inc"只能用于整数、长整数或双精度浮点数，要是在其他类型的数据上就会导致操作失败，其中包括很多语言会自动转换成数字的类型，例如null,布尔类型，或数字构成的字符串。"$inc"键的值必须为数字，不能使用字符串、数组和其他非数字的值，否则会报错，要修改其他类型，只能使用"$set"。
> db.foo.insert({"count":"1"})
WriteResult({ "nInserted" : 1 })
> db.foo.find()
{ "_id" : ObjectId("5770befc4f533aa7535d46d5"), "count" : "1" }
> db.foo.update({},{"$inc":{"count":1}})
WriteResult({
"nMatched" : 0,
"nUpserted" : 0,
"nModified" : 0,
"writeError" : {
"code" : 16837,
"errmsg" : "Cannot apply $inc to a value of non-numeric type. {_id: ObjectId('5770befc4f533aa7535d46d5')} has the field 'count' of non-numeric type String"
}
})
> db.foo.update({},{$set:{count:2}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.foo.find()
{ "_id" : ObjectId("5770befc4f533aa7535d46d5"), "count" : 2 }
>
5. 数组修改器 $push
数组修改器，顾名思义它只可以用于操作数组，只能用在值为数组的键上。$push修改器如果指定的值已经存在，"$push"会想已有的数组末尾加入一个元素，要是没有就会创建一个新的数组
> db.blog.findOne() { "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post", "author" : { "name" : "joe schmoe op", "email" : "joe@example.com" } } > db.blog.update({"title":"a blog post"},{"$unset":{"author":1}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.blog.findOne() { "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post" } > db.blog.update({"title":"a blog post"},{"$push":{"comments":{"name":"joe","email":"joe@example.com","content":"nice post"}}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.blog.findOne() { "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post", "comments" : [ { "name" : "joe", "email" : "joe@example.com", "content" : "nice post" } ] }
6. 数组修改器 $ne
$ne也是用来操作数组的修改器，在查询文档中，如果一个值不在数组里面就把他加进去，如果在不添加
> db.users.insert({"name":"joe","emails":["joe@example.com","joe@gmail.com","joe@yahoo.com"]})
WriteResult({ "nInserted" : 1 })
> db.users.findOne()
{
"_id" : ObjectId("5770ca42e90c1adc80040a08"),
"name" : "joe",
"emails" : [
"joe@example.com",
"joe@gmail.com",
"joe@yahoo.com"
]
}
> db.users.update({"name":"joe","emails":{$ne:"joe@gmail.com"}},{$push:{"emails":"joe@gmail.com"}})
WriteResult({ "nMatched" : 0, "nUpserted" : 0, "nModified" : 0 }) --nMatched为0表示没有修改
> db.users.update({"name":"joe","emails":{$ne:"joe@itpub.com"}},{$push:{"emails":"joe@itpub.com"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.users.findOne()
{
"_id" : ObjectId("5770ca42e90c1adc80040a08"),
"name" : "joe",
"emails" : [
"joe@example.com",
"joe@gmail.com",
"joe@yahoo.com",
"joe@itpub.com"
]
}
以上这种方式也可以使用$addToSet实现。
7. 数组修改器 $addToSet
$addToSet也是用来操作数组的修改器，实现的功能与$ne修改器相同，且更为方便。使用$addToSet修改器可以避免重复
> db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@example.com", "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com" ] } > db.users.update({"_id":ObjectId("5770ca42e90c1adc80040a08")},{$addToSet:{"emails":"joe@gmail.com"}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 0 }) --原文档里已有"joe@gmail.com",修改完也没有产生重复值 > db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@example.com", "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com" ] } > db.users.update({"_id":ObjectId("5770ca42e90c1adc80040a08")},{$addToSet:{"emails":"joe@163.com"}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@example.com", "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com", "joe@163.com" ] }
8. 数组修改器 $each
$each数组修改器要和$addToSet修改结合起来用，可以一次添加多个不同的值。例如上面的例子中，我们一次添加多个email值， 如下：
> db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@example.com", "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com", "joe@163.com" ] } > db.users.update({"_id":ObjectId("5770ca42e90c1adc80040a08")},{$addToSet:{$each:["joe@example.com","joe@python.com","joe@php.com"]}}) WriteResult({ "nMatched" : 0, "nUpserted" : 0, "nModified" : 0, "writeError" : { "code" : 52, "errmsg" : "The dollar ($) prefixed field '$each' in '$each' is not valid for storage." } }) > db.users.update({"_id":ObjectId("5770ca42e90c1adc80040a08")},{$addToSet:{"emails":{$each:["joe@example.com","joe@python.com","joe@php.com"]}}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@example.com", "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com", "joe@163.com", "joe@python.com", "joe@php.com" ] }
9. 数组修改器 $pop
$pop修改器主要于从数组中删除元素，他可以从数组中的任何一端删除元素，
例如:
{$pop:{key:1}} 从数组末尾删除一个元素
{$pop:{key:-1}} 从数组头部删除一个元素
> db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@example.com", "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com", "joe@163.com", "joe@python.com", "joe@php.com" ] } > db.users.update({"name":"joe"},{$pop:{"emails":1}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@example.com", "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com", "joe@163.com", "joe@python.com" ] } > db.users.update({"name":"joe"},{$pop:{"emails":-1}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com", "joe@163.com", "joe@python.com" ] }
有时我们需要基于特定条件来删除元素，而不仅仅依据位置，就可以使用$pull修改器
10. 数组修改器 $pull
$pull修改器和$pop修改类似，都是用来删除数组中的元素
$pull可以基于特定条件来删除元素
$pull会将所有匹配到的数据全部删掉，如对数组[1,2,1,1]执行pull 1,得到的结果就是只有一个元素的数组[2]
例如我们想删除emails数组中的"joe@163.com"和"joe@itpub.com"两个元素：
> db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com", "joe@163.com", "joe@python.com" ] } > db.users.update({"name":"joe"},{$pull:{"emails":["joe@163.com","joe@itpub.com"]}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 0 }) --好像不能一次删除多个，没有起作用 > db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@gmail.com", "joe@yahoo.com", "joe@itpub.com", "joe@163.com", "joe@python.com" ] } > db.users.update({"name":"joe"},{$pull:{"emails":"joe@163.com"}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.update({"name":"joe"},{$pull:{"emails":"joe@itpub.com"}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.users.findOne() { "_id" : ObjectId("5770ca42e90c1adc80040a08"), "name" : "joe", "emails" : [ "joe@gmail.com", "joe@yahoo.com", "joe@python.com" ] }
11. 数组的定位修改器 $
若是数组有多个值，而我们只想对其中一部分进行操作，有两种方法可以实现这种操作。
两种方法操作数组中的值：通过位置或定位操作符("$")
数组都是以0开头的，可以将下标直接作为键来选择元素。
> db.blog.findOne() { "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post", "comments" : [ { "name" : "joe", "email" : "joe@example.com", "content" : "nice post" }, { "name" : "bob", "email" : "bob@example.com", "content" : "good post" } ] } > db.blog.update({"title":"a blog post"},{$set:{"comments.1.name":"livan"}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.blog.findOne() { "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post", "comments" : [ { "name" : "joe", "email" : "joe@example.com", "content" : "nice post" }, { "name" : "livan", "email" : "bob@example.com", "content" : "good post" } ] } > db.blog.update({"title":"a blog post"},{$set:{"comments.1.email":"livan@example.com"}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.blog.findOne() { "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post", "comments" : [ { "name" : "joe", "email" : "joe@example.com", "content" : "nice post" }, { "name" : "livan", "email" : "livan@example.com", "content" : "good post" } ] }
在很多情况下，不预先查询文档就不能知道要修改数组的下标，为了克服这种困难，mongodb提供了定位操作符"$",
用来定位查询文档已经匹配的元素，并进行更新,定位符只更新第一个匹配的元素。
例如：用户john把名字改成了jim，就可以用定位符来替换评论中的名字:
db.blog.update({"comments.author":"john"},{$set:{"comments.$.author:"john"}})
可以理解为{"comments.author":"john"}查询条件定位到第一个元素，就执行{$set: {"comments.$.author:"john"}}，"$"定位符就表示找到的第一个元素
> db.blog.findOne() { "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post", "comments" : [ { "name" : "joe", "email" : "joe@example.com", "content" : "nice post" }, { "name" : "livan", "email" : "livan@example.com", "content" : "good post" } ] } > db.blog.update({"comments.name":"livan"},{$set:{"comments.$.email":"bob@example.com"}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.blog.update({"comments.name":"livan"},{$set:{"comments.$.name":"bob"}}) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) > db.blog.findOne() { "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post", "comments" : [ { "name" : "joe", "email" : "joe@example.com", "content" : "nice post" }, { "name" : "bob", "email" : "bob@example.com", "content" : "good post" } ] }