具有空值的MongoDb查询数组 [英] MongoDb query array with null values

问题描述

我的收藏夹中的对象看起来像:

I have objects in my collection that look like:

{ MyArray:[null, "some value", null] }

我想查询具有空值作为数组元素的那些对象.查询

I want to query those objects that have a null value as an array element. The query

db.collection.find({"MyArray":null})

不起作用，似乎只能找到MyArray为空的对象，例如

does not work, it seems to find only the objects with MyArray being null, e.g.

{ MyArray:null }

如何定义查询?

请看我的真实对象之一:

Please see one of my real objects:

{
        "_id" : BinData(3,"ch9PrWveqU6niB6FGVhIOg=="),
        "PeerGroup" : "male",
        "ProductId" : BinData(3,"weRiKOtXEUSDZHkGHLcwzw=="),
        "CategoryIds" : [
                BinData(3,"BXzpwVQozECLaPkJy26t6Q=="),
                BinData(3,"ox303ZeM50KelvoUbPBJ8Q=="),
                BinData(3,"26ziaY+G9UKMyjmtVkkhcg=="),
                BinData(3,"D2X8vObte0eJHNcDfp2HBw==")
        ],
        "ShopId" : BinData(3,"ZdfPmrlKR0GkLPC4djJuKw=="),
        "BrandId" : BinData(3,"kCHyuyLvgECxPF1nxwr7qQ=="),
        "Created" : ISODate("2012-08-24T07:42:12.416Z"),
        "LastActivity" : ISODate("2013-01-14T19:38:11.776Z"),
        "Price" : 129.9,
        "Sale" : false,
        "Rating" : 11.057340703605368,
        "RatingTimed" : 0.05670431130054035,
        "Available" : null,
        "FreeDelivery" : null,
        "Attrs" : [
                null,
                null,
                null,
                null
        ]
}

然后我通过以下方式查询:

And then I query by:

db.collection.find({"Attrs":null})

没有结果.

推荐答案

好吧，我通过通过C#驱动程序加载空"候选对象来解决了这个问题，结果发现这些值不是null，而是Bson Undefined！它们在外壳中显示为"null"！请参阅 http://jira.mongodb.org/browse/SERVER-2426 . 这有效:

Ok, I figured it out by loading my "null" candidates via my C# driver and it turns out that the values are not null, but Bson Undefined!! They are displayed as "null" in the shell! See http://jira.mongodb.org/browse/SERVER-2426. This works:

db.xxx.find({"Attrs":{$type:6}})

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