For now, you'd do something like
(hc.GetJSON 'post' (url,'?',hc.UrlEncode queryParams) bodyParams).Data.rows
I can envision extending the URL parameter to be more than a simple character vector and having HttpCommand build the URI with the query string, something like:
hc.GetJSON 'post' (url queryParams) bodyParams
You mentioned that the query fills your workspace. I've got an option in the forthcoming version of HttpCommand to direct the body of the response to a file. That might help in this case as well.