code: func (a *ArgType) colvals(fields []*Field, ignoreNames ...string) string {
  	ignore := map[string]bool{}
  	for _, n := range ignoreNames {
  		ignore[n] = true
  	}
  
  	str := ""
  	i := 0
  	for _, f := range fields {
  		if ignore[f.Name] {
  			continue
  		}
  
  		if i != 0 {
  			str = str + ", "
  		}
  		str = str + a.Loader.NthParam(i)
  		i++
  	}
  
  	return str
  }
docs: // colvals creates a list of value place holders for fields excluding any Field
  // with Name contained in ignoreNames.
  //
  // Used to present a comma separated list of column place holders, used in a
  // SELECT or UPDATE statement (ie, "$1, $2, $3 ...").