How to update subset of a string in MongoDB?

Question

I want to update the following subset of a string in monogdb

Collection: Paper
Field: URL

Document Current: 
   Name : House
   URL : www.home.com/300x300
Document Updated
   Name : House
   URL : www.home.com/600x600

I have already tried this but it doesn't seem to be working:

db.Paper.find({Name:"House"}).forEach(function(e,i) {
    e.URL=e.URL.replace("300","600");
    db.Paper.save(e);
});

Any ideas?

Also if you want to replace all partials I'm pretty sure you'll have to do `e.URL.replace(/300/g, '600')` — Taplar, Dec 23 '19 at 23:32
yes sorry 'db.Paper.save(e);' Ill try that second suggestion now. Thanks — Kingswoop, Dec 23 '19 at 23:39
Does this answer your question? [How to replace substring in mongodb document](https://stackoverflow.com/questions/12589792/how-to-replace-substring-in-mongodb-document) — mwilson, Dec 24 '19 at 00:03
I think you have to use `regex` instead of string in the first arguments of the `replace` method. see the details answer below. — krishna Prasad, Dec 24 '19 at 01:10

score 1 · Accepted Answer · answered Dec 24 '19 at 05:07

You can use one of the following aggregations to query and update:

db.test.aggregate( [
  {
      $match: {
           url: { $regex: "300x300" }
      }
  },
  { 
      $addFields: { 
          url: { $split: [ "$url", "300" ] } 
      } 
  },
  { 
      $addFields: { 
          url: { 
              $concat: [ 
                        { $arrayElemAt: [ "$url", 0 ] }, 
                        "600", 
                        { $arrayElemAt: [ "$url", 1 ] }, 
                        "600", 
                        { $arrayElemAt: [ "$url", 2 ] }
              ] 
          }
      }
 }
] ).forEach( doc => db.test.updateOne( { _id: doc._id }, { $set: { url: doc.url } } ) )

With MongoDB version 4.2+ you can specify the aggregation instead of an update operation with updateMany:

db.test.updateMany(
  { 
      url: { $regex: "300x300" }
  },
  [
    { 
      $addFields: { 
          url: { $split: [ "$url", "300" ] } 
      } 
    },
    { 
      $addFields: { 
          url: { 
              $concat: [ 
                        { $arrayElemAt: [ "$url", 0 ] }, 
                        "600", 
                        { $arrayElemAt: [ "$url", 1 ] }, 
                        "600", 
                        { $arrayElemAt: [ "$url", 2 ] }
              ] 
          }
      }
    }
  ] 
)

score 0 · Answer 2 · answered Dec 24 '19 at 01:07

Pretty simple, you have to use regex instead of string in the pattern of replace function as below:

> db.Paper.find({Name:"House"}).forEach(function (e, i) {e.URL =  e.URL.replace(/300/g, "600"), printjson(e); db.Paper.save(e);}  )
{
    "_id" : ObjectId("5e016224a16075c5bd26fbe2"),
    "Name" : "House",
    "URL" : "www.home.com/600x600"
}
> db.Paper.find()
{ "_id" : ObjectId("5e016224a16075c5bd26fbe2"), "Name" : "House", "URL" : "www.home.com/600x600" }
>

So, there is a difference between e.URL.replace("300", "600") and e.URL.replace(/300/g, "600"). You should figureout it yourself.

For references, please go through this: https://flaviocopes.com/how-to-replace-all-occurrences-string-javascript/

How to update subset of a string in MongoDB?

2 Answers2

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