数组修改器 $push $ne ($addToSet $each ) $pop $pull

 $push 向已有数组末尾 增加一个元素，如果数组不存在则创建。

如：

给blog 增加评论数组 ，本来没有 comments 数组 ，则创建了 comments 数组。

> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "title" : "My Blog post",
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z")
}
> db.foo.update({"title":"My Blog post"},
... {$push : {"comments":
... {"name":"joe","email":"joe@example.com","content":"nice post."}}})

> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "title" : "My Blog post"
}

再增加一条评论 ，插入在 comments 数组 末尾。

> db.foo.update({"title":"My Blog post"},
... {$push : {"comments":
... {"name":"bob","email":"bob@example.com","content":"good post."}}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "title" : "My Blog post"
}

$ne 跟 $push 连用

$ne 表示 数组中不存在 这个条件，才执行 后面的条件 ( 跟 $push 连用表示 不存在条件 则 把 它 插入到 数组末尾）。

> db.foo.update({"title":"My Blog post"},
... {$set:{"authors":["joe","bob"]}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "title" : "My Blog post"
}

 给 authors 键 增加 Richie 用户。

> db.foo.update({"authors":{"$ne":"Richie"}},
... {$push : { "authors":"Richie"}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "title" : "My Blog post"
}

 增加成功。

增加一个重复的 joe 看看

> db.foo.update({"authors":{"$ne":"joe"}},
... {$push:{"authors":"joe"}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "title" : "My Blog post"
}
>

没有加进去。

$addToSet 可以实现 跟"$ne"相同的功能。

加入已经存在的

> db.foo.update({"title":"My Blog post"},
... {"$addToSet":{"authors":"joe"}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "title" : "My Blog post"
}

跟 $ne 一样 没有任何变化

加入 新作者 Apple

> db.foo.update({"title":"My Blog post"},
... {"$addToSet":{"authors":"Apple"}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie",
                "Apple"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "title" : "My Blog post"
}

 $addToSet  可以跟  $each 组合使用  （x 完成 $ne 和 $push 组合不能完成的 X）

一次添加多个 邮件地址

> db.foo.update({"title":"My Blog post"},
... {"$addToSet":
... {"emails":{"$each":["joe@php.net","joe@example.com","joe@python.org"]}}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie",
                "Apple"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "emails" : [
                "joe@php.net",
                "joe@example.com",
                "joe@python.org"
        ],
        "title" : "My Blog post"
}

删除数组元素

$pop  删除 数组中指定位置的元素

$pull   删除 数组中指定条件的元素，跟位置无关，会删掉所有匹配条件的元素。

{$pop : { key : 1}} 从数组末尾 删掉一个元素。

> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie",
                "Apple"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "emails" : [
                "joe@php.net",
                "joe@example.com",
                "joe@python.org"
        ],
        "title" : "My Blog post"
}
> db.foo.update({"title":"My Blog post"},
... {"$pop":{"emails":1}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie",
                "Apple"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "emails" : [
                "joe@php.net",
                "joe@example.com"
        ],
        "title" : "My Blog post"
}

 {$pop : { key : -1}}从数组头部删除一个元素。

> db.foo.update({"title":"My Blog post"},
... {"$pop":{"emails":-1}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie",
                "Apple"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "emails" : [
                "joe@example.com"
        ],
        "title" : "My Blog post"
}

$pull 删除指定条件的字段，删掉 authors 中的  Apple ：

> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie",
                "Apple"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "emails" : [
                "joe@example.com"
        ],
        "title" : "My Blog post"
}
> db.foo.update({"title":"My Blog post"},
... {"$pull":{"authors":"Apple"}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdee24389834bfb0bd267a9"),
        "authors" : [
                "joe",
                "bob",
                "Richie"
        ],
        "comments" : [
                {
                        "name" : "joe",
                        "email" : "joe@example.com",
                        "content" : "nice post."
                },
                {
                        "name" : "bob",
                        "email" : "bob@example.com",
                        "content" : "good post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "emails" : [
                "joe@example.com"
        ],
        "title" : "My Blog post"
}

 $pull 删除所有匹配条件的元素

> db.foo.update({"title":"My Blog post"},
... {"$set":{"test":[1,1,2,1]}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdefcb789834bfb0bd267ac"),
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "test" : [
                1,
                1,
                2,
                1
        ],
        "title" : "My Blog post"
}
> db.foo.update({"title":"My Blog post"},
... {"$pull":{"test":1}})
> db.foo.findOne()
{
        "_id" : ObjectId("4fdefcb789834bfb0bd267ac"),
        "content" : "Here's my blog post.",
        "date" : ISODate("2012-06-16T12:19:25.163Z"),
        "test" : [
                2
        ],
        "title" : "My Blog post"
}
>