MongoDB: remove unique constraint

"How does mongodb handle "alters" to the schema?"

MongoDB is schema-less

The only thing there uniqueness is enforced is on the indexing level where you can define indexes on a collection with unique criteria. So you may want to remove the related index and re-created it if necessary.

I hope this will be helpful.

db.collection_name.getIndexes()

Returns an array that holds a list of documents that identify and describe the existing indexes on the collection. Now find your index name from list and then remove that index as below:

db.users.dropIndex("your_index_name_here")

Here is an example:

db.product.dropIndex({ style: 1 })