Database 获取MongoDb中以前处理过的文档

我有以下收集结构：

{
   "col1": "col1_value1",
   "col2": "col2_value1"
}

{
   "col1": "col1_value2",
   "col2": "col2_value2"
}

如何在MongoDB中获得以下结果：

  {
   "previous_col1": "", // init value
   "col1": "col1_value1",
   "previous_col2": "",
   "col2": "col2_value1"
  }

 {
  "previous_col1": "col1_value1",  // previous value
  "col1": "col1_value2",

  "previous_col2": "col2_value1",
  "col2": "col2_value2"
 }

在SQL中，我可以通过定义两个变量@previous_col1和@previous_col2来保持前面的行，从而获得相同的结果

此mongo shell查询执行以下操作：

var cur = db.collection.find();

var result_docs = [ ];
var prev_col1 = "", prev_col2 = "";

while (cur.hasNext()) {
    let thisDoc = cur.next();
    thisDoc.previous_col1 = prev_col1;
    thisDoc.previous_col2 = prev_col2;
    prev_col1 = thisDoc.col1;
    prev_col2 = thisDoc.col2;
    result_docs.push(thisDoc);
}

---

result\u docs

数组将所有文档更新为以前文档的值。

非常感谢您的支持。我得到了预期的结果。