通过

Azure Cosmos DB for MongoDB vCore 上的$documents使用情况

$documents聚合管道阶段用于从一组提供的文档创建管道。 如果要在不查询集合的情况下处理特定文档，此阶段特别有用。

语法

{
  $documents: [
    <document1>,
    <document2>,
    ...
  ]
}

参数

参数 DESCRIPTION
<document> 表示要在管道中包含的文档的 JSON 对象。

例子

示例 1：从特定文档创建管道

以下示例演示如何使用 $documents 阶段来处理一组预定义文档：

db.aggregate([
  {
    $documents: [
      {
        "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
        "name": "Lakeshore Retail | Holiday Supply Hub - Marvinfort",
        "location": {
          "lat": 60.1441,
          "lon": -141.5012
        },
        "sales": {
          "fullSales": 3700
        },
        "tag": ["#ShopLocal", "#SeasonalSale"]
      },
      {
        "_id": "7e53ca0f-6e24-4177-966c-fe62a11e9af5",
        "name": "Contoso, Ltd. | Office Supply Deals - South Shana",
        "location": {
          "lat": 40.7128,
          "lon": -74.0060
        },
        "sales": {
          "fullSales": 5400
        },
        "tag": ["#TechDeals", "#FreeShipping"]
      }
    ]
  },
  {
    $project: {
      _id: 1,
      name: 1,
      "location.lat": 1,
      "location.lon": 1,
      "sales.fullSales": 1,
      tags: "$tag"  // renames "tag" to "tags"
    }
  }
]);

此查询将返回以下文档。

[
  {
    _id: '7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5',
    name: 'Lakeshore Retail | Holiday Supply Hub - Marvinfort',
    location: { lat: 60.1441, lon: -141.5012 },
    sales: { fullSales: 3700 },
    tags: [ '#ShopLocal', '#SeasonalSale' ]
  },
  {
    _id: '7e53ca0f-6e24-4177-966c-fe62a11e9af5',
    name: 'Contoso, Ltd. | Office Supply Deals - South Shana',
    location: { lat: 40.7128, lon: -74.006 },
    sales: { fullSales: 5400 },
    tags: [ '#TechDeals', '#FreeShipping' ]
  }
]

示例 2：与其他管道阶段合并$documents

db.aggregate([
  {
    $documents: [
      {
        "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
        "name": "Lakeshore Retail | Holiday Supply Hub - Marvinfort",
        "location": {
          "lat": 60.1441,
          "lon": -141.5012
        },
        "sales": {
          "fullSales": 3700
        },
        "tag": ["#ShopLocal", "#SeasonalSale"]
      },
      {
        "_id": "7e53ca0f-6e24-4177-966c-fe62a11e9af5",
        "name": "Contoso, Ltd. | Office Supply Deals - South Shana",
        "location": {
          "lat": 40.7128,
          "lon": -74.0060
        },
        "sales": {
          "fullSales": 5400
        },
        "tag": ["#TechDeals", "#FreeShipping"]
      }
    ]
  },
  {
    $match: { "sales.fullSales": { $gt: 4000 } }
  },
  {
    $sort: { "sales.fullSales": -1 }
  }
]);

此查询将返回以下文档。

[
  {
    _id: '7e53ca0f-6e24-4177-966c-fe62a11e9af5',
    name: 'Contoso, Ltd. | Office Supply Deals - South Shana',
    location: { lat: 40.7128, lon: -74.006 },
    sales: { fullSales: 5400 },
    tag: [ '#TechDeals', '#FreeShipping' ]
  }
]

局限性

  • $documents阶段仅在数据库级聚合管道中受支持。 它必须是管道中的第一个阶段才能正常运行。

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