message: Prevent newer operation from overriding older ones
  When executeQuery is used on urql the requestPolicy
  might be changed to reflect a forced update. We don't
  want to take overrides into account though, so it's
  safer to only store the first operation per unique
  operation key and ignore subsequent duplicates.
diff: @@ -83,8 +83,11 @@ export const cacheExchange = (opts: StoreOpts): Exchange => ({
  const updateDependencies = (op: Operation, dependencies: string[]) => {
  dependencies.forEach(dep => {
  const keys = deps[dep] || (deps[dep] = []);
  - ops.set(op.key, op);
  keys.push(op.key);
  +
  + if (!ops.has(op.key)) {
  + ops.set(op.key, op);
  + }
  });
  };
  