Firestore document not incrementing using REST API - php

Question

I am trying to increment my Cloud Firestore using the REST API, however the documentation is unclear as to how this works. Here is my current implementation:-
I am trying to increment the integer value 'c' by 2, so if server value stored is 10 I want it to become 12 with this. Please help.
{
"writes": [
{
"currentDocument": {
"exists": true
}
},
{
"transform": {
"document": "projects/project_name/databases/(default)/documents/collection_name/user_id",
"fieldTransforms": [
{
"increment": {
"c": {
"integerValue": "2"
}
}
}
]
}
}
]
}
Error I keep getting:-
{
"error": {
"code": 400,
"message": "Invalid JSON payload received. Unknown name \"\": Root element must be a message.",
"status": "INVALID_ARGUMENT",
"details": [
{
"#type": "type.googleapis.com/google.rpc.BadRequest",
"fieldViolations": [
{
"description": "Invalid JSON payload received. Unknown name \"\": Root element must be a message."
}
]
}
]
}
}
Edit: Here's the error after fixing my payload:
{
"error": {
"code": 400,
"message": "Invalid JSON payload received. Unknown name \"writes\" at 'document': Cannot find field.",
"status": "INVALID_ARGUMENT",
"details": [
{
"#type": "type.googleapis.com/google.rpc.BadRequest",
"fieldViolations": [
{
"field": "document",
"description": "Invalid JSON payload received. Unknown name \"writes\" at 'document': Cannot find field."
}
]
}
]
}
}

Answer 1

As per the FieldTransform documentation, you must set a fieldPath on your JSON representation. Here's the list of possible types for union field transform_type:
{
"fieldPath": string,
// Union field transform_type can be only one of the following:
"setToServerValue": enum (ServerValue),
"increment": {
object (Value)
},
"maximum": {
object (Value)
},
"minimum": {
object (Value)
},
"appendMissingElements": {
object (ArrayValue)
},
"removeAllFromArray": {
object (ArrayValue)
}
// End of list of possible types for union field transform_type.
}
You should remove the fieldPath which is c inside the increment:
"fieldTransforms": [
{
"increment": {
"c": {
"integerValue": "2"
}
}
}
]
and change it to this structure:
"fieldTransforms": [
{
"fieldPath": "<FieldName>",
"increment": {
"integerValue": "2"
}
}
]
And also, just want to note that currentDocument and transform should be both inside the objects of writes. For reference, here's the full JSON representation based on your given JSON representation above:
{
"writes": [
{
"currentDocument": {
"exists": true
},
"transform": {
"document": "projects/project_name/databases/(default)/documents/collection_name/user_id",
"fieldTransforms": [
{
"fieldPath": "c",
"increment": {
"integerValue": "2"
}
}
]
}
}
]
}
Here's the result by using the Postman:
For more information, you may want to check Firebase REST API: Write.