Arrays 查询具有JSON文档数组的MongoDB集合

我有一个mongodb集合，格式如下：

    {
    _id:"xxxx"
    comments : [
            {
                comment:"I know good art is supposed to be controversial"
                commentid:"820168"
                username:"bleckfella"
                isprocessed:0
            },
            {
                comment:"Next thing.."
                commentid:"820846"
                username:"egzegs"
                isprocessed:0
            },
            {
                comment:"Good decision, please stay away Jamie."
                commentid:"820901"
                username:"Capt_mulch"
                isprocessed:1
            }
        ]

    some fields.....
    ....
    ....
}
{
    _id:"xxxx"
    comments : [
            {
                comment:"who REALLY cares?"
                commentid:"820162"
                username:"BigBunny"
                isprocessed:0
            },
            {
                comment:"Double oh dear ..."
                commentid:"820849"
                username:"MrX"
                isprocessed:1
            },
            {
                comment:"Good decision."
                commentid:"830501"
                username:"mark11"
                isprocessed:0
            }
        ]

    some fields.....
    ....
    ....
}
{
        _id:"xxxx"
    comments : [
            {
                comment:"my condolences Mick. My thoughts are with you."
                commentid:"821164"
                username:"BigBunny"
                isprocessed:0
            },
            {
                comment:"Three letters.     O. M. G."
                commentid:"840844"
                username:"MrX"
                isprocessed:0
            }

        ]

    some fields.....
    ....
    ....
}

现在我想查询这些数据，查找值为“isprocessed”字段为“1”的注释 我从shell尝试过的查询有：

db.coll.find({comments:{$elemMatch: {isProcessed:1}}},{"comments.isProcessed":1,"comments.comment":1}).pretty()

&

两者的输出相同，即：

{
    _id : "xxxx"
    "comments : [
            {
                comment:"I know good art is supposed to be controversial"
                isprocessed:0
            },
            {
                comment:"Next thing.."
                isprocessed:0
            },
            {
                comment:"Good decision, please stay away Jamie."
                isprocessed:1
            }
        ]

}
{
    _id : "xxxx"
    comments : [
            {
                comment:"who REALLY cares?"
                isprocessed:0
            },
            {
                comment:"Double oh dear ..."
                isprocessed:1
            },
            {
                comment:"Good decision."
                isprocessed:0
            }
        ]

}

这意味着它显示了我不需要的匹配文档的带有“isprocessed”字段值“0”的注释。 我需要输出为：

{
    "_id":"xxxx"
    comments : [
            {
                comment:"Good decision, please stay away Jamie."
                isprocessed:1
            }
        ]
}
{
    _id:"xxxx"
    comments : [
            {
                comment:"Double oh dear ..."
                isprocessed:1
            }
        ]
}

在以这种格式读取字段“isprocessed”后，我还需要更新其值。 如何为此编写查询。请建议任何解决方案。

尝试以下命令

db.coll.aggregate([{$unwind: '$comments'}, {$match : {'comments.isprocessed' : 1}}, {$project : {_id : 1, 'comments.comment' : 1, 'comments.isprocessed' : 1}}])

---

它成功了。非常感谢你，迪克什。但还有一个问题。如何使用查询将此isprocessed字段从一个更改为0。表示要打印isprocessed值为0的记录。对吗？不，我想将数据库中isprocessed字段的值从1更新为0。此答案将能够帮助您。

db.coll.aggregate([{$unwind: '$comments'}, {$match : {'comments.isprocessed' : 1}}, {$project : {_id : 1, 'comments.comment' : 1, 'comments.isprocessed' : 1}}])