WHERE中不允许使用ajax-datatables-rails聚合函数

Question

我已经为一个表实现了ajax-datatables-rails，我使用group

获取带有查询的原始记录

    class ListcontractorsDatatable < AjaxDatatablesRails::Base

  def view_columns
    # Declare strings in this format: ModelName.column_name
    # or in aliased_join_table.column_name format
    @view_columns ||= {
       id: { source: "Contractor.id", cond: :eq },
       name: { source: "Contractor.name" },
       city: { source: "Contractor.city" },
       ico: { source: "Contractor.ico" },
       country: { source: "Contractor.country" },
       count: {source: "Contract.count"}
    }
  end
def_delegators :@view, :link_to, :showcontractor_path, :content_tag
  def data
    records.map do |contractor|
      {
        # example:
         id: contractor.id,
         name: link_to(contractor.name, showcontractor_path(contractor.id)),
         city: contractor.city,
         ico: contractor.ico,
         country: contractor.country,
         count: contractor.count,
         extlink: link_to(content_tag(:i,nil,class: 'fa fa-external-link'), 'https://www.somepage.com/'+contractor.ico.to_s)
        }
    end
  end
  private
def get_raw_records
  Contractor.joins(:contracts).select("contractors.id,name,ico,city,country,count(resultinfo_id) as count")
              .group("contractors.id,contractors.name,contractors.ico,contractors.city,contractors.country")

end

end

一切正常（排序，分页，所有列都正确），搜索除外。当我把任何东西都搜索到时我得到了错误

  

PG :: GroupingError：错误：不允许使用聚合函数   WHERE

我在查询分支0.4.0时找不到任何有组的工作解决方案。请你帮助我好吗？ THX