# Firestore update

<https://firebase.google.com/docs/firestore/manage-data/add-data#update-data>

## **set vs update**

> The way I understood the difference:
>
> * **set** without merge will overwrite a document or create it if it doesn't exist yet
> * **set** with merge will update fields in the document or create it if it doesn't exists
> * **update** will update fields but will fail if the document doesn't exist
> * **create** will create the document but fail if the document already exists
>
> There's also a difference in the kind of data you provide to set and update.
>
> For set you always have to provide document-shaped data:
>
> ```javascript
> set(
>   {a: {b: {c: true}}},
>   {merge: true}
> )
> ```
>
> With update you can also use field paths for updating nested values:
>
> ```javascript
> update({
>   'a.b.c': true
> })
> ```

from [Difference between set with {merge: true} and update](https://stackoverflow.com/questions/46597327/difference-between-set-with-merge-true-and-update)


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