Changing the value of the uid (UserID) on Google Analytics

Question

I'm using Google Analytics from the backend, and I'm setting the values as following:

• cid : The "visitor's" value. When the first request, I generated a unique ID and save it via Cookie
• uid : The user's value (when an account is created - unique ID too). - I'm hoping that Google ties those two values when both set, which would allow me to just send the uid in future uses and they would be linked to the cid.

My question is the following:

It might happen that the value of the uid changes (when the user merges his account with another one). In that case, I need to tell Google: this uid is now this new value.

Is there a way to do that? How?

Answer 1

No there's no way to "merge" two or more user IDs in Analytics. Consider keeping the first ever used value of uid in your user data record for sending data to Analytics.

Answer 2

Historical values ​​cannot be changed in Google Analytics.