插入数组奇怪的行为或错误？ 在蒙戈

Question

db.foo.remove();
var a10001 = Array(90,0,5,134);
var a10002 = Array(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,107);
var a10003 = Array(202);

db.foo.insert({
a10001 : a10001,
a10002 : a10002,
a10003 : a10003
});

前两个数组 a10001 a10002 与插入的第三个 a10003 不同！

db.foo.find( {} , { "a10003" : 1} );

{ "_id" : ObjectId("534e031ad1844c26ea167205"), "a10003" : [    null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null,   null, null,     null,   null,   null,   null,   null,   null,   null,   null,   null ] }

但是当我向第三个数组添加一个元素时

var a10003 = Array(202,1);

它表现良好。

{ "_id" : ObjectId("534e0402d1844c26ea167206"), "a10003" : [  202,  1 ] }

版本：

mongod --version
db version v2.4.9
Wed Apr 16 06:02:33.649 git version: 52fe0d21959e32a5bdbecdc62057db386e4e029c

Answer 1

我认为你的语法不正确，正如你在这里看到的那样创建一个包含 1...N 的 JavaScript 数组。 这意味着 Array(202) 创建大小为 202 的空数组。

         var foo = new Array(202);//create a 202 element array

你可以这样试试

        var foo = new Array();
        foo.push(202);

Answer 2

@Devesh 是对的。 当您尝试创建一个带有单个参数 x 的数组对象时，x 是一个整数（如果它不是整数，那么它将创建一个包含该元素的数组，您可以尝试使用布尔值或字符串）那么这意味着您正在初始化具有未定义值的某个长度的数组。

如果您在插入 mongoDB 集合时使用该数组，那么 mongoDB 将插入空值。 查看我在 mongo shell 中运行的命令。

> var arr = new Array(1);
> arr
[ undefined ]
> arr.length
1


> var arr = new Array(5)
> arr.length
5
> arr
[ undefined, undefined, undefined, undefined, undefined ]

> var arr = new Array(5,3,4)
> arr.length
3
> arr
[ 5, 3, 4 ]

> var arr = new Array(5)
> arr
[ undefined, undefined, undefined, undefined, undefined ]

> db.testing.insert({arr:arr})
WriteResult({ "nInserted" : 1 })
> db.testing.find().pretty();
{
        "_id" : ObjectId("534e0f9fbdb7d435d4bc46d5"),
        "arr" : [
                null,
                null,
                null,
                null,
                null
        ]
}

> var arr = new Array(5,4,3,2,1)
> db.testing.insert({arr:arr})
WriteResult({ "nInserted" : 1 })
> db.testing.find().pretty();
{
        "_id" : ObjectId("534e0f9fbdb7d435d4bc46d5"),
        "arr" : [
                null,
                null,
                null,
                null,
                null
        ]
}
{
        "_id" : ObjectId("534e10c8bdb7d435d4bc46d6"),
        "arr" : [
                5,
                4,
                3,
                2,
                1
        ]
}

我希望它有帮助。

您可以参考的其他链接http://docs.mongodb.org/manual/reference/operator/update-array/ http://docs.mongodb.org/manual/reference/method/db.collection.insert /