mongodb的修改器

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。要把"foo"的值设备"bar",常见的错误做法如下：

db.coll.update(criteria,{"foo":"bar"})

这种情况是不对的，实际上这种做法会把整个文档用{"foo":"bar"}替换掉，一定要使用以$开头的修改器来修改键/值对。

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，则创建他，他对更新模式或者用户定义键来说非常方便。

> db.users.findOne()
{
        "_id" : ObjectId("56fe7df8b322e3ff1dabf834"),
        "name" : "joe",
        "age" : ,
        "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" : , "nUpserted" : , "nModified" :  })
> db.users.findOne()
{
        "_id" : ObjectId("56fe7df8b322e3ff1dabf834"),
        "name" : "joe",
        "age" : ,
        "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" :  })
> db.blog.findOne()
{
        "_id" : ObjectId("57709da84f533aa7535d46d3"),
        "title" : "a blog post",
        "author" : {
                "name" : "joe",
                "email" : "joe@example.com"
        }
}
> db.blog.update({"author.name":"joe"},{"$set":{"author.name":"joe schmoe"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.blog.findOne()
{
        "_id" : ObjectId("57709da84f533aa7535d46d3"),
        "title" : "a blog post",
        "author" : {
                "name" : "joe schmoe",
                "email" : "joe@example.com"
        }
}
> db.blog.update({"title":"a blog post"},{"$set":{"author.name":"joe schmoe op"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> 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" : ,
        "sex" : "male",
        "location" : "Wisconsin",
        "favorite book" : [
                "cat's cardle",
                "foundation trilogy",
                "ender's game"
        ]
}
> db.users.update({"name":"joe"},{"$unset":{"favorite book":}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.users.findOne()
{
        "_id" : ObjectId("56fe7df8b322e3ff1dabf834"),
        "name" : "joe",
        "age" : ,
        "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" :  })
> db.games.findOne()
{
        "_id" : ObjectId("5770a1394f533aa7535d46d4"),
        "game" : "pinball",
        "user" : "joe"
}
> db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.games.findOne()
{
        "_id" : ObjectId("5770a1394f533aa7535d46d4"),
        "game" : "pinball",
        "user" : "joe",
        "score" :
}

为"score"键增加50再减少20

> db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.games.findOne()
{
        "_id" : ObjectId("5770a1394f533aa7535d46d4"),
        "game" : "pinball",
        "user" : "joe",
        "score" :
}
> db.games.update({"game":"pinball","user":"joe"},{"$inc":{"score":-}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.games.findOne()
{
        "_id" : ObjectId("5770a1394f533aa7535d46d4"),
        "game" : "pinball",
        "user" : "joe",
        "score" :
}

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"。

如下：

> db.foo.insert({"count":""})
WriteResult({ "nInserted" :  })
> db.foo.find()
{ "_id" : ObjectId("5770befc4f533aa7535d46d5"), "count" : "" }
> db.foo.update({},{"$inc":{"count":}})
WriteResult({
        "nMatched" : ,
        "nUpserted" : ,
        "nModified" : ,
        "writeError" : {
                "code" : ,
                "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:}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.foo.find()
{ "_id" : ObjectId("5770befc4f533aa7535d46d5"), "count" :  }
>

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"},{"$unset":{"author":}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.blog.findOne()
{ "_id" : ObjectId("57709da84f533aa7535d46d3"), "title" : "a blog post" }
> db.blog.update({"title":"a blog post"},{"$push":{"comments":{"name":"joe","email":"joe@example.com","content":"nice post"}}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.blog.findOne()
{
        "_id" : ObjectId("57709da84f533aa7535d46d3"),
        "title" : "a blog post",
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post"
                }
        ]
}

为blog集合"a blog post"文档再增加一条评论：

> db.blog.update({"title":"a blog post"},{"$push":{"comments":{"name":"bob","email":"bob@example.com","content":"good post"}}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> 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"
                }
        ]
}

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" :  })
> 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" : , "nUpserted" : , "nModified" :  })                                    --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" : , "nUpserted" : , "nModified" :  })
> 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")},{$addToSet:{"emails":"joe@gmail.com"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })     --原文档里已有"joe@gmail.com",修改完也没有产生重复值
> db.users.findOne()
{
        "_id" : ObjectId("5770ca42e90c1adc80040a08"),
        "name" : "joe",
        "emails" : [
                "joe@example.com",
                "joe@gmail.com",
                "joe@yahoo.com",
                "joe@itpub.com"
        ]
}
> db.users.update({"_id":ObjectId("5770ca42e90c1adc80040a08")},{$addToSet:{"emails":"joe@163.com"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> 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" : ,
        "nUpserted" : ,
        "nModified" : ,
        "writeError" : {
                "code" : ,
                "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" : , "nUpserted" : , "nModified" :  })
> 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"},{$pop:{"emails":}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.users.findOne()
{
        "_id" : ObjectId("5770ca42e90c1adc80040a08"),
        "name" : "joe",
        "emails" : [
                "joe@example.com",
                "joe@gmail.com",
                "joe@yahoo.com",
                "joe@itpub.com",
                "joe@163.com",
                "joe@python.com"
        ]
}
> db.users.update({"name":"joe"},{$pop:{"emails":-}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> 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"},{$pull:{"emails":["joe@163.com","joe@itpub.com"]}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })  --好像不能一次删除多个，没有起作用
> db.users.findOne()
{
        "_id" : ObjectId("5770ca42e90c1adc80040a08"),
        "name" : "joe",
        "emails" : [
                "joe@gmail.com",
                "joe@yahoo.com",
                "joe@itpub.com",
                "joe@163.com",
                "joe@python.com"
        ]
}
> db.users.update({"name":"joe"},{$pull:{"emails":"joe@163.com"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.users.update({"name":"joe"},{$pull:{"emails":"joe@itpub.com"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> 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"},{$set:{"comments.1.name":"livan"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> db.blog.findOne()
{
        "_id" : ObjectId("57709da84f533aa7535d46d3"),
        "title" : "a blog post",
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post"
                },
                {
                        "name" : "livan",
                        "email" : "bob@example.com",
                        "content" : "good post"
                }
        ]
}
> db.blog.update({"title":"a blog post"},{$set:{"comments.1.email":"livan@example.com"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> 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" : , "nUpserted" : , "nModified" :  })
> db.blog.update({"comments.name":"livan"},{$set:{"comments.$.name":"bob"}})
WriteResult({ "nMatched" : , "nUpserted" : , "nModified" :  })
> 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"
                }
        ]
}

《MongoDB权威指南中文版》

mongdb数组修改     http://blog.163.com/wm_at163/blog/static/1321734902012526111917601/