Go - check Firestore document exists-CodePudding

I can't seem to check if a document exists. If it doesn't exist it goes to an error rather than just an empty document

 "error": "rpc error: code = NotFound desc = \"projects/PROJECTID/databases/(default)/documents/claimed/123abc\" not found"

The code in question, values have be replaced with placeholders.

package main

import (
    "context"
    "errors"
    "cloud.google.com/go/firestore"

func main() {

    ctx := context.Background()
    client, err := firestore.NewClient(ctx, "PROJECTID")
    if err != nil {
        log.Fatalln(err)
    }

    docRef := client.Collection("claimed").Doc("123abc")
    doc, err := docRef.Get(ctx)
    if err != nil {
        return err // <----- Reverts to here
    }

    // Doesn't make it to here
    if doc.Exists() {
        return errors.New("document ID already exists")
    } else {
        _, err := docRef.Set(ctx, /* custom object here */)
        if err != nil {
            return err
        }
    }
}

The code documentation for Get() says

// Get retrieves the document. If the document does not exist, Get return a NotFound error, which
// can be checked with
//    status.Code(err) == codes.NotFound
// In that case, Get returns a non-nil DocumentSnapshot whose Exists method return false and whose
// ReadTime is the time of the failed read operation.

So is my solution to just modify the error handling instead? `if err != nil { /* check it exists */ }

** Solution **


    docRef := client.Collection("claimed").Doc("123abc")
    doc, err := docRef.Get(ctx)
    if err != nil {
        if status.Code(err) == codes.NotFound {
            // Handle document not existing here
            _, err := docRef.Set(ctx, /* custom object here */)
            if err != nil {
                return err
            }
        } else {
            return err
        }
    }
    
    // Double handling (???)
    if doc.Exists() {
        // Handle document existing here
    }

CodePudding user response：

You will get an error if the document doesn't exist.

You use the fact that you get the error for non-existence.

See the documentation for Get for handling the error.

doc, err := docRef.Get(ctx)
  if err != nil {
    if status.Code(err) == codes.NotFound { ... }
  }
}

CodePudding user response：

You must replace "PROJECTID" in firestore.NewClient with the value of a Google Cloud Platform Project ID.

You can find the Project ID either in the Cloud Console or through the gcloud CLI using e.g. gcloud projects list.