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Class: Mongoid::Association::Referenced::HasManyThrough::Eager

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::Mongoid::Association::Eager
Instance Chain:
self, ::Mongoid::Association::Eager
Inherits: Mongoid::Association::Eager
Defined in: lib/mongoid/association/referenced/has_many_through/eager.rb

Overview

Two-query eager preloader for has_many :through associations.

Class Method Summary

::Mongoid::Association::Eager - Inherited

.new

Instantiate the eager load class.

Instance Method Summary

::Mongoid::Association::Eager - Inherited

#run

Run the preloader.
#each_loaded_document_of_class

Retrieves the documents of the specified class, that have the foreign key included in the specified list of keys.
#prepare_criteria_for_loaded_documents

Prepares the criteria to retrieve the documents of the specified class, that have the foreign key included in the specified list of keys.
#shift_association

Shift the current association metadata.

Constructor Details

This class inherits a constructor from Mongoid::Association::Eager

Instance Method Details

#build_targets_map(intermediates, through_fk, source_assoc) (private)

Build a ::Hash mapping each owner FK value to an array of target docs. Uses two different strategies depending on where the FK lives.

[ GitHub ] 

  


# File 'lib/mongoid/association/referenced/has_many_through/eager.rb', line 40



def build_targets_map(intermediates, through_fk, source_assoc)
  if source_assoc.stores_foreign_key?
    fk_on_intermediate_targets_map(intermediates, through_fk, source_assoc)
  else
    fk_on_source_targets_map(intermediates, through_fk, source_assoc)
  end
end


  








  

    #fk_on_intermediate_targets_map(intermediates, through_fk, source_assoc)   (private)
  



  

    
FK is on the intermediate (e.g. appointment.patient_id -> belongs_to :patient).

  



  [ GitHub ]


  

  


# File 'lib/mongoid/association/referenced/has_many_through/eager.rb', line 49



def fk_on_intermediate_targets_map(intermediates, through_fk, source_assoc)
  source_fk_vals = intermediates.filter_map { |i| i.public_send(source_assoc.foreign_key) }.uniq
  targets = source_assoc.klass.where(
    source_assoc.primary_key => { '$in' => source_fk_vals }
  ).to_a
  targets_by_pk = targets.group_by { |t| t.public_send(source_assoc.primary_key) }

  result = Hash.new { |h, k| h[k] = [] }
  intermediates.each do |i|
    owner_fk_val = i.public_send(through_fk)
    matched = targets_by_pk[i.public_send(source_assoc.foreign_key)] || []
    result[owner_fk_val].concat(matched)
  end
  result
end


  








  

    #fk_on_source_targets_map(intermediates, through_fk, source_assoc)   (private)
  



  

    
FK is on the source (e.g. reader.book_id -> has_many :readers on Book).

  



  [ GitHub ]


  

  


# File 'lib/mongoid/association/referenced/has_many_through/eager.rb', line 66



def fk_on_source_targets_map(intermediates, through_fk, source_assoc)
  source_pk = source_assoc.primary_key
  intermediate_pks = intermediates.filter_map { |i| i.public_send(source_pk) }.uniq
  targets = source_assoc.klass.where(
    source_assoc.foreign_key => { '$in' => intermediate_pks }
  ).to_a
  targets_by_source_fk = targets.group_by { |t| t.public_send(source_assoc.foreign_key) }

  result = Hash.new { |h, k| h[k] = [] }
  intermediates.each do |i|
    owner_fk_val = i.public_send(through_fk)
    matched = targets_by_source_fk[i.public_send(source_pk)] || []
    result[owner_fk_val].concat(matched)
  end
  result
end


  








  

    #group_by_key   (private)
  



  

    
Required by base class contract. Not called from preload since this
class manages its own two-query traversal directly.

  



  [ GitHub ]


  

  


# File 'lib/mongoid/association/referenced/has_many_through/eager.rb', line 92



def group_by_key
  @association.through_association.primary_key
end


  








  

    #preload   (private)
  

  [ GitHub ]


  

  


# File 'lib/mongoid/association/referenced/has_many_through/eager.rb', line 11



def preload
  @docs.each { |d| set_relation(d, []) }

  through_assoc = @association.through_association
  source_assoc  = @association.source_association

  owner_pk   = through_assoc.primary_key
  through_fk = through_assoc.foreign_key

  owner_ids = @docs.filter_map { |d| d.public_send(owner_pk) }.uniq
  return if owner_ids.empty?

  # Step 1: load all intermediate records
  intermediates = through_assoc.klass
                               .where(through_fk => { '$in' => owner_ids })
                               .to_a

  # Step 2: map owner FK values to arrays of target docs
  targets_by_owner_fk = build_targets_map(intermediates, through_fk, source_assoc)

  # Step 3: set relation on each owner doc
  @docs.each do |doc|
    key_val = doc.public_send(owner_pk)
    set_relation(doc, targets_by_owner_fk[key_val] || [])
  end
end


  








  

    #set_relation(doc, element)   (private)
  

  [ GitHub ]


  

  


# File 'lib/mongoid/association/referenced/has_many_through/eager.rb', line 83



def set_relation(doc, element)
  return if doc.blank?

  proxy = HasManyThrough::Proxy.new(doc, @association, preloaded: element)
  doc.set_relation(@association.name, proxy)
end