code: func (a *ArgType) colcount(fields []*Field, ignoreNames ...string) int {
  	ignore := map[string]bool{}
  	for _, n := range ignoreNames {
  		ignore[n] = true
  	}
  
  	i := 1
  	for _, f := range fields {
  		if ignore[f.Name] {
  			continue
  		}
  
  		i++
  	}
  	return i
  }
docs: // colcount returns the 1-based count of fields, excluding any Field with Name
  // contained in ignoreNames.
  //
  // Used to get the count of fields, and useful for specifying the last SQL
  // parameter.