E11000 duplicate key error index in mongodb. I found this error after migrating my field from “unique” to “non-unique”. And in this problem we use mongoengine for flask.

First, i have a model such as bellow

class Tag(db.Document):
    title = db.StringField(max_length=50, unique=True)

and then, i need to change it without unique.

class Tag(db.Document):
    title = db.StringField(max_length=255, required=True)

And we found this error:

mongoengine.errors.NotUniqueError
NotUniqueError: Tried to save duplicate unique keys (insertDocument :: caused by :: 11000 E11000 duplicate key error index: myblog.tag.$name_1 dup key: { : null })

I found this answer to solve it: http://stackoverflow.com/questions/24430220/e11000…

$ mongo
> use yourdatabase;
> db.yourtable.getIndexes()
> db.yourtable.dropIndexes()

For example on my databases:

$ mongo
> use mysimpleblog;
> db.tag.getIndexes()
> db.tag.dropIndexes()

Hope it usefull..