How to insert server timestamp in Firestore document using REST? - rest

Question

I want to insert a document using a REST call to Firestore createDocument method. One of the fields is a timestamp field that should be set on the server. With Android SDK it's as simple as annotating a Date field with #ServerTimestamp and keeping it null — now how do I do it in REST?
{
"fields": {
"timezoneId": {
"stringValue": "Europe\/London"
},
"city": {
"stringValue": "London"
},
"timestamp": {
"timestampValue": "???"
}
}
}
I tried using null, 0, empty string, timestamp — everything fails with an error requiring the standard RFC3339 format (e.g. 2018-01-31T13:50:30.325631Z). Is there any placeholder value I can use, or any way to obtain that timestamp?

Answer 1

The Android SDK doesn't execute a createDocument request when creating the document. Instead it uses the write request to issue an update and a transform request at the same time. If you are wanting to only use createDocument, then the answer is no.
Your payload would look something like this:
{
"writes": [
{
"update": {
"name": "projects/{projectId}/databases/{databaseId}/documents/{document_path}",
"fields": {
"timezoneId": {
"stringValue": "Europe\/London"
},
"city": {
"stringValue": "London"
}
}
},
// ensure the document doesn't exist
"currentDocument": {
"exists": false
}
},
{
"transform": {
"document": "projects/{projectId}/databases/{databaseId}/documents/{document_path}",
"fieldTransforms": [
{
"fieldPath": "timestamp",
"setToServerValue": "REQUEST_TIME"
}
]
}
}
]
}
The only downside to adding documents this way is you would need to generate the Document ID yourself (the SDK's generate them). I hope this helps.