API for User sorting on bases of number of posts

Hi
I am working on Custom Search using API v1 and v2. I did not find any api to sort users on bases of number of posts. 

   As I can sort users on bases of login and registration data like: 

<#assign sorted_data=rest("2.0", "/search?q=" + "select registration_data from users order by registration_data.registration_time DESC"?url).data.items />"

But how can it be possible in case of sort by number of post or sort by rank ???