Question

您好我在mongo遇到了问题。我先向您展示一个数据示例。这是我表中的记录。

{
    "_id": "3691149613248",
    "following": [{
    "content_id": "2584833593728",
    "date": "2015-08-20 12:46:55"
    }, {
    "content_id": "3693447751360",
    "date": "2015-09-11 12:17:55"
    }, {
    "content_id": "2582396936896",
    "date": "2015-09-12 07:04:02"
    }, {
    "content_id": "3697346507456",
    "date": "2015-09-14 09:56:03"
    }, {
    "content_id": "3697755500800",
    "date": "2015-09-16 10:05:51"
    }, {
    "content_id": "2589701320192",
    "date": "2015-09-16 10:51:19"
    }, {
    "content_id": "2585723555136",
    "date": "2015-09-16 11:40:26"
    }, {
    "content_id": "3695996668352",
    "date": "2015-09-16 12:50:25"
    }, {
    "content_id": "3694290368512",
    "date": "2015-09-16 12:50:33"
    }, {
    "content_id": "3691210127552",
    "date": "2015-09-16 13:02:57"
    }, {
    "content_id": "3694134958464",
    "date": "2015-09-16 13:06:17"
    }, {
    "content_id": "3697315148736",
    "date": "2015-09-17 06:58:35"
    }, {
    "content_id": "3692104837824",
    "date": "2015-09-17 12:19:12"
    }, {
    "content_id": "3693400309376",
    "date": "2015-09-22 05:43:04"
    }]
}

我想获取following数组，条件是只提取特定记录，即前缀为content_ids的{{1}}，并在限制和偏移量中指定取值369。 / p>

我正在使用content_id来获取给定限制和记录的记录$slice数组的偏移量。但是如何过滤following以及content_id。

我当前的查询：

$slice

这是使用db.collectionName.find({ _id: "3691149613248" }, { "following": { "$slice": [0, 10] } });获取following数组，该数组在limit＆amp;偏移。但它提取了所有content_id，包括前缀content_id＆amp; 258但我只需要使用mongo查询369前缀为content_id。

任何人都可以帮忙吗??

Answer 1

您可以将$unwind和$match与mongo aggregation结合使用，以获得预期的输出，例如：

db.collection.aggregate({
    $match: {
    "_id": "3691149613248"  // you can skip this condition if not required
    }
}, {
    $unwind: "$following"
}, {
    $match: {
    "following.content_id": {
        $regex: /^369/
    }
    }
}, {
    $group: {
    _id: "$_id",
    "following": {
        $push: "$following"
    }
    }
})

如果您想将skip和limit应用于上述查询，则可以轻松使用它：

db.collection.aggregate({
    $match: {
    "_id": "3691149613248" //use this if you want to filter out by _id
    }
}, {
    $unwind: "$following"
}, {
    $match: {
    "following.content_id": {
        $regex: /^369/
    }
    }
}, {
    $skip: 4  // you can set offset here
}, {
    $limit: 3 // you can set limit here
}, {
    $group: {
    _id: "$_id",
    "following": {
        $push: "$following"
    }
    }
})

编辑：

如果您使用的PHP版本低于5.4，则查询将为：

$search = "369";
$criteria = array(array("$match" => array("_id" => "3691149613248")),
    array("$unwind" => "$following"),
    array("$match" => array("following.content_id" => array("$regex" => new MongoRegex("/^$search/")))),
    array("$skip" => 4), array("$limit" => 3),
    array("$group" => array("_id" => "$_id", "following" => array("$push" => "$following"))));
$collection - > aggregate($criteria);

如果您使用的PHP版本大于5.3，则只需将{和}括号分别替换为[和]。

在mongodb中将$ slice与$ regex一起用于subDocument数组

1 个答案: