Heroku で ransack による日付一致検索 ref: http://qiita.com/ysaito8015@github/items/66b1985f695da4efc528

file4.txt

app[web.1]: Parameters: {"utf8"=>"✓", "q"=>{"order_date_cont"=>"2015-03-02"}}
app[web.1]: Purchase Load (4.9ms)  SELECT DISTINCT "purchases".* FROM "purchases" WHERE ("purchases"."order_date" ILIKE '%2015-03-02%')  ORDER BY "purchases"."order_date" DESC
app[web.1]: PG::UndefinedFunction: ERROR:  operator does not exist: date ~~* unknown
app[web.1]: LINE 1: ... FROM "purchases" WHERE ("purchases"."order_date" ILIKE '%20...
app[web.1]:                                                              ^
app[web.1]: HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
app[web.1]: SELECT DISTINCT "purchases".* FROM "purchases" WHERE ("purchases"."order_date" ILIKE '%2015-03-02%')  ORDER BY "purchases"."order_date" DESC
app[web.1]: Rendered shared/_search_result_box.html.erb(6.9ms)
app[web.1]: Completed 500 Internal Server Error in 69ms

purchase.rb

private 
  ransacker :order_date do
    Arel.sql('date(order_date)')
  end

purchase_controller.rb

class PurchaseController < ApplicationController
  private
  def search_params
    search_conditions = %i(
      order_date_date_equals
    )
    params.require(:q).permit(search_conditions)
  end
end

ransack.rb

Ransack.configure do |config|
  config.add_predicate 'date_equals',
  arel_predicate: 'eq',
  formatter: proc { |v| v.to_date },
  formatter: proc { |v| v.present? },
  type: :string
end

search.html.erb

<label>注文日</label>
<%= f.search_field :order_date_date_equals, class: 'date' %>