Diagramm is not created when FK has no name

[s13o]

The constraint name of FK is optional. This example is fully correct. When you doing schema export in Spanner web console with the "Show Equivalent DDL" button you can easily get something like this.

CREATE TABLE Orders (
  OrderID INT64 NOT NULL,
  CustomerID INT64 NOT NULL,
  ProductID INT64 NOT NULL,
  FOREIGN KEY (CustomerID) REFERENCES Customers (CustomerID)
) PRIMARY KEY (OrderID);

But the diagram will be not created for it