ruby on rails - ActiveRecord: Scope to get parents with no children created at a specific date -

i want parent records no records created @ specific date on one-to-many relation in rails 4 activerecord , postgres database.

migrations:

class createparents < activerecord::migration   def change     enable_extension 'pgcrypto' unless extension_enabled?('pgcrypto')      create_table :parents, id: :uuid, default: 'gen_random_uuid()' |t|       t.string :name       t.timestamps null: false     end end  class createchilds < activerecord::migration   def change     create_table :childs, id: false |t|       t.uuid :parent_id, null: false       t.date :created_at, null: false       t.string :name     end      add_foreign_key :childs, :parents     add_index :childs, [:parent_id, :created_at], :unique => true   end end 

models:

class parent < activerecord::base   has_many :childs end  class child < activerecord::base   belongs_to :parent end 

now want parents no child @ specific date scope:

class parent < activerecord::base   has_many :childs    def self.with_no_childs_created_at(date)     ...   end end 

can me? i'm going crazy this. tried lot things .includes, .references, .where, .not, .joins etc. don't it.

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update 1

one suggested solution looked likes this:

def self.with_no_stats_created_at(date)   joins(:childs).where.not(childs: {created_at: date}) end 

but works if parent has child created in past. sql should demonstrate problem:

select "parents".* "parents" inner join "childs" on "childs"."parent_id" = "parents"."id" ("childs"."created_at" != $1)  [["created_at", "2016-04-19"]] 

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update 2

this solved problem (suggested @ilya):

def self.with_no_childs_created_at(date)   preload(:childs).select {|p| p.childs.all? {|c| c.created_at != date }} end 

you can preload childs avoid n+1 queries , process array:

def self.with_no_childs_created_at(date)   preload(:childs).select {|p| p.childs.all? {|c| c.created_at != date }} end