Use a field value to update another field in same document

user_2813152 0
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I am using Firebase Firestore and have documents with two fields:

field X
field Y

They are both numbers. Now I want to copy the value from X to Y. Of course I can just read the document to have the value X and then do a write operation on the same document and update field Y.

My question is, if there is a possibility to do this with just an update-operation as I couldn't find anything related but it seems to me like this might be something that's implemented by Firebase.

Thank you

google-cloud-firestore firebase java
2 Answers

Unfortunately, something like you described is not possible. One would simply read the document and update it with the read value.

user_44541570

Depending on your needs, you can use transactions. For instance, I used it for the rating functionality, and actually, you might find this thread helpful.

user_39613430
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