Duplicates when using remote and prefetch

Hello

I am using prefetch to obtain most used data. When writing something more results are queried from server with remote option.

If prefetch data contains same items as the remote data, both of them are shown in the list (so they are duplicates).

I tried to Google it but only result is that "dupDetector" should be used like this
`dupDetector: function (remoteMatch, localMatch) {
return remoteMatch.id === localMatch.id;
}`

But it seems that there is no dupDetector option available, is that correct? How should I do this?