postgresql – Find partial match with textsearch query

I have the following query that I did hard looking on this site:

FROM   renns
        to_tsvector('english', coalesce(numar_admin, '')) || 
        to_tsvector('english', coalesce(nume_strada, '')) || 
        to_tsvector('english', coalesce(nume_prenume, ''))|| 
        to_tsvector('english', coalesce(bloc, '')) ||
        to_tsvector('english', coalesce(apartament, '')) 
    ) @@ plainto_tsquery('english', '$q')

It works if I write in the variable $q all the text that appears in one of the columns present in the query. For example: cherry

I would like to write only: cher and return all rows fields in which it finds this string: “cher”.