Adding multiple fields to documents in mongodb using pymongo-CodePudding

I have a sample collection of documents in mongo db like below

[{"name":"hans","age":30,"test":"pass","pre":"no","calc":"no"},
{"name":"abs","age":20,"test":"not_pass","pre":"yes","calc":"no"},
{"name":"cdf","age":40,"test":"pass"},
{"name":"cvf","age":30,"test":"not_pass","pre":"no","calc":"yes"},
{"name":"cdf","age":23,"test":"pass"},
{"name":"asd","age":35,"test":"not_pass"}]

For some documents the fields pre and calc are not present. I want to add those two fields to the documents which dont have those fields with value null for both "pre":"null", "calc":"null".

The final document should look like

[{"name":"hans","age":30,"test":"pass","pre":"no","calc":"no"},
{"name":"abs","age":20,"test":"not_pass","pre":"yes","calc":"no"},
{"name":"cdf","age":40,"test":"pass","pre":"null","calc":"null"},
{"name":"cvf","age":30,"test":"not_pass","pre":"no","calc":"yes"},
{"name":"cdf","age":23,"test":"pass","pre":"null","calc":"null"},
{"name":"asd","age":35,"test":"not_pass","pre":"null","calc":"null"}]

I tried this way but didnt work.

db.users.update({}, { "$set" : { "pre":"null","calc":"null" }}, false,true)

CodePudding user response：

Thinking that you need an update with the aggregation pipeline.

And use $ifNull operator.

db.users.update({},
[
  {
    "$set": {
      "pre": {
        $ifNull: [
          "$pre",
          "null"
        ]
      },
      "calc": {
        $ifNull: [
          "$calc",
          "null"
        ]
      }
    }
  }
],
false,
true
)

Sample Mongo Playground

CodePudding user response：

The easiest option is to run this query for every missing field that you have , for example for pre:

db.collection.update({
pre: {
    $exists: false
  }
},
{
 "$set": {
   "pre": null
 }
},
{
  multi: true
})

Playground