Add timestamp in Firestore documents

问题

I'm newbie to Firestore. Firestore docs says...

Important: Unlike "push IDs" in the Firebase Realtime Database, Cloud Firestore auto-generated IDs do not provide any automatic ordering. If you want to be able to order your documents by creation date, you should store a timestamp as a field in the documents.

Reference: https://firebase.google.com/docs/firestore/manage-data/add-data

So do I have to create key name as timestamp in document? Or created is suffice to fulfill above statement from Firestore documentation.

{
    "created": 1534183990,
    "modified": 1534183990,
    "timestamp":1534183990
}

回答1:

Whatever you want to call it is fine afaik. Then you can use orderByChild('created').

I also mostly use firebase.database.ServerValue.TIMESTAMP when setting time

ref.child(key).set({
  id: itemId,
  content: itemContent,
  user: uid,
  created: firebase.database.ServerValue.TIMESTAMP 
})

回答2:

Use firestore Timestamp class, firebase.firestore.Timestamp.now().

Since firebase.firestore.FieldValue.serverTimestamp() does not work with add method from firestore. Reference

回答3:

For Firestore

ref.doc(key).set({
  created: firebase.firestore.FieldValue.serverTimestamp()
})

回答4:

The documentation isn't suggesting the names of any of your fields. The part you're quoting is just saying two things:

The automatically generated document IDs for Firestore don't have a natural time-based ordering like they did in Realtime Database.
If you want time-based ordering, store a timestamp in the document, and use that to order your queries. (You can call it whatever you want.)

回答5:

Try this one for Swift 4 Timestamp(date: Date())

let docData: [String: Any] = [
"stringExample": "Hello world!",
"booleanExample": true,
"numberExample": 3.14159265,
"dateExample": Timestamp(Date()),
"arrayExample": [5, true, "hello"],
"nullExample": NSNull(),
"objectExample": [
    "a": 5,
    "b": [
        "nested": "foo"
    ]
]
]
db.collection("data").document("one").setData(docData) { err in
if let err = err {
    print("Error writing document: \(err)")
} else {
    print("Document successfully written!")
}
}

回答6:

The way it worked with me, is just taking the timestamp from the snapshot parameter snapshot.updateTime

exports.newUserCreated = functions.firestore.document('users/{userId}').onCreate(async (snapshot, context) => {
console.log('started!     v1.7');
const userID = context.params['userId'];

firestore.collection(`users/${userID}/lists`).add({
    'created_time': snapshot.updateTime,
    'name':'Products I ♥',
}).then(documentReference => {
    console.log("initial public list created");
    return null;
  }).catch(error => {
    console.error('Error creating initial list', error);
    process.exit(1);
});

});

回答7:

This solution worked for me:

Firestore.instance.collection("collectionName").add({'created': Timestamp.now()});

The result in Cloud Firestore is: Cloud Firestore Result

回答8:

Swift 5.1

...
"dateExample": Timestamp(date: Date()),
...

来源：https://stackoverflow.com/questions/51846914/add-timestamp-in-firestore-documents

标签

firebase

google-cloud-firestore