CODEWITHSUNDEEP
node.jsfirebasegoogle-cloud-firestore
Dody
Dody

Reputation: 668

Firestore set doc with merge option true or update doc

I have to update a single field in an existed Firestore document.

However, I don't know if there is some difference between using

admin.firestore().doc('doc_id').set({name:'Bill'},{ merge: true })

or

admin.firestore().doc('doc_id').update({name:'Bill'})

If the document is: 

{
  name: Bart,
  age: 18
}

Should .update(...) just update the field and not remove the field "age" in this case?

Upvotes: 12

Views: 3257

Answers (2)

Yevhen Sokolov
Yevhen Sokolov

Reputation: 81

I'm not sure if it worked like this before but.

setDoc with merge will also merge child objects, when updateDoc overwrites them.

I mean if we have a document like:

{
  child: {
    a: 'a'
  }
}

And after setDoc(ref, { child: { b: 'b' } }, { merge: true }) we will have a document like:

{
  child: {
    a: 'a',
    b: 'b'
  }
}

updateDoc(ref, { child: { b: 'b' } }) results in:

{
  child: {
    b: 'b'
  }
}

Upvotes: 1

Doug Stevenson
Doug Stevenson

Reputation: 317692

There is no difference between those two options for existing documents.

The difference between them is only evident for documents that don't exist. set() with merge will create the document if it does't exist, and update() will fail if it doesn't exist.

Upvotes: 15

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