How to replace substring in mongodb document

Question

I have a lot of mongodb documents in a collection of the form:

{ .... "URL":"www.abc.com/helloWorldt/..." ..... } 

I want to replace helloWorldt with helloWorld to get:

{ .... "URL":"www.abc.com/helloWorld/..." ..... } 

How can I achieve this for all documents in my collection?

Answer 1

db.media.find({mediaContainer:"ContainerS3"}).forEach(function(e,i) {     e.url=e.url.replace("//a.n.com","//b.n.com");     db.media.save(e); }); 

Answer 2

Nowadays,

• starting Mongo 4.2, db.collection.updateMany (alias of db.collection.update) can accept an aggregation pipeline, finally allowing the update of a field based on its own value.
• starting Mongo 4.4, the new aggregation operator $replaceOne makes it very easy to replace part of a string.

// { URL: "www.abc.com/helloWorldt/..." } // { URL: "www.abc.com/HelloWo/..." } db.collection.updateMany(   { URL: { $regex: /helloWorldt/ } },   [{     $set: { URL: {       $replaceOne: { input: "$URL", find: "helloWorldt", replacement: "helloWorld" }     }}   }] ) // { URL: "www.abc.com/helloWorld/..." } // { URL: "www.abc.com/HelloWo/..." } 

• The first part ({ URL: { $regex: /helloWorldt/ } }) is the match query, filtering which documents to update (the ones containing "helloWorldt") and is just there to make the query faster.
• The second part ($set: { URL: {...) is the update aggregation pipeline (note the squared brackets signifying the use of an aggregation pipeline):
  • $set is a new aggregation operator (Mongo 4.2) which in this case replaces the value of a field.
  • The new value is computed with the new $replaceOne operator. Note how URL is modified directly based on the its own value ($URL).

---

Before Mongo 4.4 and starting Mongo 4.2, due to the lack of a proper string $replace operator, we have to use a bancal mix of $concat and $split:

db.collection.updateMany(   { URL: { $regex: "/helloWorldt/" } },   [{     $set: { URL: {       $concat: [         { $arrayElemAt: [ { $split: [ "$URL", "/helloWorldt/" ] }, 0 ] },         "/helloWorld/",         { $arrayElemAt: [ { $split: [ "$URL", "/helloWorldt/" ] }, 1 ] }       ]     }}   }] )