mongodb - 如何重命名 MongoDB 对象数组中的嵌套键？

Question

文档结构

{
  _id: 5,
  grades: [
     { grade_ : 80, mean: 75, std: 8 },
     { mean: 90, std: 5 },
     { mean: 85, std: 3 }
  ]
}

根据上面的 mongodb 文档结构，我想将键 grade_ 重命名为 grade

db.collection.update({"_id":5},{"$rename":{"grades.grade_":"grades.grade"}},{"upsert":false,"multi":true})

给出以下错误

"writeError" : {
        "code" : 28,
        "errmsg" : "cannot use the part (grades of grades.grade_) to traverse the element ({grades: [ { grade_: 80.0, mean: 75.0, std: 8.0 }, { mean: 90.0, std: 5.0 }, { mean: 85.0, std: 3.0 } ]})"
    }

我想将键 grade_ 重命名为 grade，预期输出

{
  _id: 5,
  grades: [
     { grade : 80, mean: 75, std: 8 },
     { mean: 90, std: 5 },
     { mean: 85, std: 3 }
  ]
}

Answer 1

根据 MongoDB 文档:($rename 如果这些字段在数组元素中则不起作用。)

For fields in embedded documents, the $rename operator can rename these fields as well as move the fields in and out of embedded documents. $rename does not work if these fields are in array elements.

因此，您需要编写自定义逻辑来进行更新。

db.collection.find({
  "grades.grade_": { $exists : 1 }
}).forEach( function( doc ) {
  for( i=0; i < doc.grades.length; i++ ) {
    if(doc.grades[i].grade_ != undefined) {
      doc.grades[i].grade = doc.grades[i].grade_;
      delete doc.grades[i].grade_;
    }
  }
  db.collection.update({ _id : doc._id }, doc);
});