How to Convert a String to ObjectId in MongoDB Using _MONGOSH

Learn how to solve the error "Argument passed in must be a string of 12 bytes or a string of 24 hex characters or an integer" while updating MongoDB fields using _MONGOSH in Mongo Compass.
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How to Convert a String to ObjectId in MongoDB Using _MONGOSH

If you're working with MongoDB and encountered the error message: "Argument passed in must be a string of 12 bytes or a string of 24 hex characters or an integer," you're not alone. This can happen when you're attempting to update fields in your collection but passing a string value where a MongoDB ObjectId is expected.

In this guide, we'll explore how to effectively manage database updates using _MONGOSH in Mongo Compass and correctly convert string values to ObjectId for seamless operations.

Understanding the Problem

When you try to update a field in a MongoDB document with a string representation of an ID instead of a valid ObjectId, MongoDB throws an error. This is essential to watch out for, as MongoDB uses ObjectId as a unique identifier for documents, and direct string conversions will lead to issues.

Common Error Message:

"Argument passed in must be a string of 12 bytes or a string of 24 hex characters or an integer."

This indicates that the string you've provided isn't formatted as a valid ObjectId. Therefore, you'll need to handle it properly within your MongoDB query.

How to Successfully Convert String to ObjectId

Here's a step-by-step solution to correctly handle the conversion of strings to ObjectId within your MongoDB queries:

Step-by-Step Solution

Find Documents with String Fields:
You'll need to identify the documents in your collection that have the field in string format. This can be achieved using the find method with the $type operator.

[[See Video to Reveal this Text or Code Snippet]]

Iterate Through the Results:
Use forEach to loop through each document that has a string in the specified field.

[[See Video to Reveal this Text or Code Snippet]]

Convert String to ObjectId:
Within the loop, convert the string field to ObjectId using MongoDB's built-in ObjectId function.

[[See Video to Reveal this Text or Code Snippet]]

Update Each Document:
Finally, update each document with the new ObjectId value while preserving the document's unique _id.

[[See Video to Reveal this Text or Code Snippet]]

Complete Code Snippet

Here's how the complete code looks when put together:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the outlined steps, you should be able to effectively convert string fields to ObjectId and avoid the common error in MongoDB when updating your collections using _MONGOSH. Remember, working with the correct data types is crucial in maintaining database integrity and functionality.

By grasping these transformations, you empower your MongoDB skills and significantly enhance your database management capabilities. Happy coding!