如何将逗号分隔的字符串字段变成MongoDB中的数组？

Question

我有三个看起来像这样的文档：

_id: ObjectId('61e1312ad435c7124aa883a1')
name: "Brian"
languages: "English,Spanish,French"

_id: ObjectId('52e1312ad435c7124aa883a2')
name: "Max"
languages: "English"

_id: ObjectId('37e1312ad435c7124aa883a9')
name: "Mike"
languages: ""

如您所见，语言字段可以是空的，有一个项目，也可以用逗号分隔的多个项目。

如何将语言字段变成数组？最终结果应该看起来像这样：

_id: ObjectId('61e1312ad435c7124aa883a1')
name: "Brian"
languages: [
    "English",
    "Spanish",
    "French"
]

_id: ObjectId('52e1312ad435c7124aa883a2')
name: "Max"
languages: [
    "English"
]

_id: ObjectId('37e1312ad435c7124aa883a9')
name: "Mike"
languages: []

Answer 1

您可以使用 $ split ：

db.collection.aggregate([
  {
    $addFields: {
      "languages": {
        $filter: {
          input: {
            $split: [
              "$languages",
              ","
            ]
          },
          cond: {
            $gt: [
              {
                $strLenCP: "$this"
              },
              0
            ]
          }
        }
      }
    }
  }
])

mongo playground

如果您想更新整个集合带有“管道更新”语法：

db.collection.updateMany(
{},
[
  {
    "$set": {
      "languages": {
        $filter: {
          input: {
            $split: [
              "$languages",
              ","
            ]
          },
          cond: {
            $gt: [
              {
                $strLenCP: "$this"
              },
              0
            ]
          }
        }
      }
    }
  }
])