Force update mongodb document using same values

I have enabled field level encryption.
But I have some existing unencrypted values in db. To update those I was trying to run an update query to update existing values using the same value. But mongodb is not updating the document if we try to update using the same value.
Is there any way I can force update mongodb document using same values?

Hi @Navin_Devassy,

Welcome to MongoDB community.

I am not certain what exactly you mean, but if you want to update fieldX with fieldY values you can use a pipeline update:

db.collection.update({},[{ $set { fieldX : "$fieldY" } }],{multi : true});