Class: ActiveRecord::Associations::JoinDependency

Inherits:
Object
  • Object
show all
Defined in:
lib/active_record/associations/join_dependency.rb,
lib/active_record/associations/join_dependency/join_base.rb,
lib/active_record/associations/join_dependency/join_part.rb,
lib/active_record/associations/join_dependency/join_association.rb

Overview

:nodoc:

Defined Under Namespace

Classes: Aliases, JoinAssociation, JoinBase, JoinPart

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(base, associations, joins) ⇒ JoinDependency

base is the base class on which operation is taking place. associations is the list of associations which are joined using hash, symbol or array. joins is the list of all string join commands and arel nodes.

Example :

class Physician < ActiveRecord::Base
  has_many :appointments
  has_many :patients, through: :appointments
end

If I execute `@physician.patients.to_a` then
  base # => Physician
  associations # => []
  joins # =>  [#<Arel::Nodes::InnerJoin: ...]

However if I execute `Physician.joins(:appointments).to_a` then
  base # => Physician
  associations # => [:appointments]
  joins # =>  []



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# File 'lib/active_record/associations/join_dependency.rb', line 95

def initialize(base, associations, joins)
  @alias_tracker = AliasTracker.create(base.connection, joins)
  @alias_tracker.aliased_table_for(base.table_name, base.table_name) # Updates the count for base.table_name to 1
  tree = self.class.make_tree associations
  @join_root = JoinBase.new base, build(tree, base)
  @join_root.children.each { |child| construct_tables! @join_root, child }
end

Instance Attribute Details

#alias_tracker ⇒ Object (readonly)

Returns the value of attribute alias_tracker.



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# File 'lib/active_record/associations/join_dependency.rb', line 48

def alias_tracker
  @alias_tracker
end

#base_klass ⇒ Object (readonly)

Returns the value of attribute base_klass.



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# File 'lib/active_record/associations/join_dependency.rb', line 48

def base_klass
  @base_klass
end

#join_root ⇒ Object (readonly)

Returns the value of attribute join_root.



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# File 'lib/active_record/associations/join_dependency.rb', line 48

def join_root
  @join_root
end

Class Method Details

.make_tree(associations) ⇒ Object 



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# File 'lib/active_record/associations/join_dependency.rb', line 50

def self.make_tree(associations)
  hash = {}
  walk_tree associations, hash
  hash
end

.walk_tree(associations, hash) ⇒ Object 



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# File 'lib/active_record/associations/join_dependency.rb', line 56

def self.walk_tree(associations, hash)
  case associations
  when Symbol, String
    hash[associations.to_sym] ||= {}
  when Array
    associations.each do |assoc|
      walk_tree assoc, hash
    end
  when Hash
    associations.each do |k,v|
      cache = hash[k] ||= {}
      walk_tree v, cache
    end
  else
    raise ConfigurationError, associations.inspect
  end
end

Instance Method Details

#aliases ⇒ Object 



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# File 'lib/active_record/associations/join_dependency.rb', line 123

def aliases
  Aliases.new join_root.each_with_index.map { |join_part,i|
    columns = join_part.column_names.each_with_index.map { |column_name,j|
      Aliases::Column.new column_name, "t#{i}_r#{j}"
    }
    Aliases::Table.new(join_part, columns)
  }
end

#instantiate(result_set, aliases) ⇒ Object 



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# File 'lib/active_record/associations/join_dependency.rb', line 132

def instantiate(result_set, aliases)
  primary_key = aliases.column_alias(join_root, join_root.primary_key)

  seen = Hash.new { |h,parent_klass|
    h[parent_klass] = Hash.new { |i,parent_id|
      i[parent_id] = Hash.new { |j,child_klass| j[child_klass] = {} }
    }
  }

  model_cache = Hash.new { |h,klass| h[klass] = {} }
  parents = model_cache[join_root]
  column_aliases = aliases.column_aliases join_root

  message_bus = ActiveSupport::Notifications.instrumenter

  payload = {
    record_count: result_set.length,
    class_name: join_root.base_klass.name
  }

  message_bus.instrument('instantiation.active_record', payload) do
    result_set.each { |row_hash|
      parent = parents[row_hash[primary_key]] ||= join_root.instantiate(row_hash, column_aliases)
      construct(parent, join_root, row_hash, result_set, seen, model_cache, aliases)
    }
  end

  parents.values
end

#join_constraints(outer_joins) ⇒ Object 



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# File 'lib/active_record/associations/join_dependency.rb', line 107

def join_constraints(outer_joins)
  joins = join_root.children.flat_map { |child|
    make_inner_joins join_root, child
  }

  joins.concat outer_joins.flat_map { |oj|
    if join_root.match? oj.join_root
      walk join_root, oj.join_root
    else
      oj.join_root.children.flat_map { |child|
        make_outer_joins oj.join_root, child
      }
    end
  }
end

#reflections ⇒ Object 



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# File 'lib/active_record/associations/join_dependency.rb', line 103

def reflections
  join_root.drop(1).map!(&:reflection)
end