module ActiveRecord module Associations class JoinDependency # :nodoc: # A JoinPart represents a part of a JoinDependency. It is inherited # by JoinBase and JoinAssociation. A JoinBase represents the Active Record which # everything else is being joined onto. A JoinAssociation represents an association which # is joining to the base. A JoinAssociation may result in more than one actual join # operations (for example a has_and_belongs_to_many JoinAssociation would result in # two; one for the join table and one for the target table). class JoinPart # :nodoc: # The Active Record class which this join part is associated 'about'; for a JoinBase # this is the actual base model, for a JoinAssociation this is the target model of the # association. attr_reader :base_klass delegate :table_name, :column_names, :primary_key, :reflections, :arel_engine, :to => :base_klass def initialize(base_klass) @base_klass = base_klass @cached_record = {} @column_names_with_alias = nil end def aliased_table Arel::Nodes::TableAlias.new table, aliased_table_name end def ==(other) raise NotImplementedError end # An Arel::Table for the active_record def table raise NotImplementedError end # The prefix to be used when aliasing columns in the active_record's table def aliased_prefix raise NotImplementedError end # The alias for the active_record's table def aliased_table_name raise NotImplementedError end # The alias for the primary key of the active_record's table def aliased_primary_key "#{aliased_prefix}_r0" end # An array of [column_name, alias] pairs for the table def column_names_with_alias unless @column_names_with_alias @column_names_with_alias = [] ([primary_key] + (column_names - [primary_key])).compact.each_with_index do |column_name, i| @column_names_with_alias << [column_name, "#{aliased_prefix}_r#{i}"] end end @column_names_with_alias end def extract_record(row) # This code is performance critical as it is called per row. # see: https://github.com/rails/rails/pull/12185 hash = {} index = 0 length = column_names_with_alias.length while index < length column_name, alias_name = column_names_with_alias[index] hash[column_name] = row[alias_name] index += 1 end hash end def record_id(row) row[aliased_primary_key] end def instantiate(row) @cached_record[record_id(row)] ||= base_klass.instantiate(extract_record(row)) end end end end end