在 `$elemMatch` 中引用子文档的另一个字段

发布于 2025-01-20 08:19:06 字数 458 浏览 1 评论 0原文

我正在尝试在$ match聚合阶段中执行$ elemmatch，我想在数组中查找是否有文档（commitchments）属性trackSthisweek的子图表小于其频率属性，但我不确定如何引用所讨论的子记录的另一个字段，我提出了：

{
    $match: {
        commitments: {
            $elemMatch: {
                tracksThisWeek: {
                    $lt: '$frequency',
                },
            },
        },
    },
},

我在集合中有一个文档，应从此聚合中返回，但不是，任何帮助都将受到赞赏:)

原文

I'm trying to perform an $elemMatch in a $match aggregation stage where I want to find if there is a document in an array (commitments) of subdocuments whose property tracksThisWeek is smaller than its frequency property, but I'm not sure how can I reference another field of the subdocument in question, I came up with:

{
    $match: {
        commitments: {
            $elemMatch: {
                tracksThisWeek: {
                    $lt: '$frequency',
                },
            },
        },
    },
},

I have a document in the collection that should be returned from this aggregation but isn't, any help is appreciated :)

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成熟的代价 2025-01-27 08:19:06

这是无法做到的，您无法在查询语言中引用任何字段，您可以使用$ expr与聚合运算符，诸如此类：

db.collection.aggregate([
  {
    $match: {
      $expr: {
        $gt: [
          {
            $size: {
              $filter: {
                input: "$commitments",
                cond: {
                  $lt: [
                    "$this.tracksThisWeek",
                    "$this.frequency"
                  ]
                }
              }
            }
          },
          0
        ]
      }
    }
  }
])

mongo playground

This can't be done, you can't reference any fields in the query language, What you can do is use $expr with aggregation operators, like this:

db.collection.aggregate([
  {
    $match: {
      $expr: {
        $gt: [
          {
            $size: {
              $filter: {
                input: "$commitments",
                cond: {
                  $lt: [
                    "$this.tracksThisWeek",
                    "$this.frequency"
                  ]
                }
              }
            }
          },
          0
        ]
      }
    }
  }
])

Mongo Playground

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