Search with default routing

Guys I met a problem that I mixed up my data in elastic with custom routing and default routing. Now I have a problem on splitting them with search. I could add "?routing=custom" to get custom routing docs, but how can I get default routing docs with no custom routing docs in them?

Just do a search, or get by ID, then they will return.

If I do a search, docs with routing will also return. I want to get doc without routing(or we could call with default routing).