Django admin search: how to override the default handler?

Question

I wish to customize the way in which search queries across the search_fields.

Is there a way to do it without hacking deeply into the Django code or creating a totally independent view?

For instance, I would like to return the union of the querysets for each of the items of the querystring.split(). So that searching for "apple bar" would return results with EITHER apple OR bar, unlike the default search which applies an AND operator.