How to query a entity from datastore with Namespace In golang? - google-app-engine

Question

I am working on a multi tenant application, I need to query a particular user from a KIND and From Particular Namespace.
I am able to get the values from default Namespace.the package i am using here is "google.golang.org/appengine/datastore"
q := datastore.NewQuery(ENTITYNAME).Filter("Name =", ed.Expense.Name)
var expenses []ExpenseEntiry
return q.GetAll(ed.Ctx, &expenses)

Answer 1

The namespace value is not part of the query (it's not a property of the query). The namespace comes from the context which you pass when executing the query, e.g. to Query.GetAll().
If you have a context (you do as you pass it to q.GetAll()), you can create a derivative context with a given namespace using the appengine.Namespace() function.
For example:
ctx2, err := appengine.Namespace(ed.Ctx, "mynamespace")
// check err
And use this new context to pass to Query.GetAll():
return q.GetAll(ctx2, &expenses)
It is rare that you need to create a new context with a different namespace, ed.Ctx should already be a context with the right namespace. So when / where you create ed.Ctx, you should already apply the namespace there, so you can avoid "accidental" exposure of data of other tenants (which is a major security issue).

Answer 2

If you are using the old lib: google.golang.org/appengine/datastore, then you need to create the context with the namespace:
ctx2, err := appengine.Namespace(ed.Ctx, "mynamespace")
if err != nil {
return err
}
But you WANT to be using the latest lib: cloud.google.com/go/datastore. The Namespace can be set directly on the Query object. This is new. You must then run the query using datastoreClient.Run(ctx, query).
func deleteTestNamespace(ctx context.Context, namespaces string) error {
dsClient, err := datastore.NewClient(ctx, log, datastore.Config{...})
err := dsClient.DeleteMulti(ctx, keys[i:i+chunk])
if err != nil {
return err
}
var keys []*datastore.Key
for _, kind := range envKinds {
// Get all keys
query := datastore.NewQuery(kind).KeysOnly().Namespace(namespace)
it := dsClient.Run(ctx, query)
for {
var key datastore.Key
_, err := it.Next(&key)
if err == iterator.Done {
break
}
if err != nil {
return err
}
keys = append(keys, &key)
}
// Delete all records in chunks of 500 or less
for i := 0; i < len(keys); i += 500 {
chunk := min(len(keys)-i, 500)
err := dsClient.DeleteMulti(ctx, keys[i:i+chunk])
if err != nil {
return err
}
}
}
return nil
}
func min(num1 int, num2 int) int {
if num1 < num2 {
return num1
}
return num2
}