Copy Specific Document in same collection

[Tre_Rush (Tre’)]

Is there a way to copy a specific document’s structure and insert it in the same collection but add new fields to the new document using MongoSH and not Compass?

[steevej (Steeve Juneau)]

What you could try is an aggregation that $match the desired document, then use $set and $unset stages to modify the document. You add a final $merge stage to insert back the modified document.

Just run the aggregation with the $merge, once you verified that your $set and $unset do the correct modification. Make sure you $unset the _id and use whenMatched:failed otherwise you risk modifying the original document.

[Tre_Rush (Tre’)]

Thank you! I appreciate the insight, I’ll try it out.

[Tarun_Gaur]

Hello @Tre_Rush ,

As well as @steevej’s suggestion, the following may fulfill your requirements as well using mongosh in particular. It is possible to copy a specific document’s structure and insert it into the same collection but with new fields and an updated _id using MongoDB’s shell (mongo shell). The reason you need to update _id also is because no two documents can have same _id and if we try to insert the document with same _id we will get below error.

MongoServerError: E11000 duplicate key error collection: Test.performer index: id dup key: { _id: *** }

Here’s an example in JavaScript using the MongoDB shell:

// Get the document you want to copy
var docToCopy = db.collectionName.findOne({});

// Create a new document with the same structure as the original
var newDoc = Object.assign({}, docToCopy);

// Remove the _id field from the new document
delete newDoc._id;

// Add new fields to the new document
newDoc.newField1 = "value1";
newDoc.newField2 = "value2";

// Generate a new ObjectId for the _id field
newDoc._id = new ObjectId();

// Insert the new document into the collection
db.collectionName.insertOne(newDoc);

This will copy the structure of the document you retrieved with findOne() into a new document, add two new fields newField1 and newField2, generate a new ObjectId for the _id field, and insert the new document into the collection. If this is not what you require, could you please post more details about the use case?

Regards,
Tarun