Class: ActiveRecord::Associations::JoinDependency::JoinPart

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

Overview

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).

Direct Known Subclasses

JoinAssociation, JoinBase

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(base_klass) ⇒ JoinPart

Returns a new instance of JoinPart.



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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 18

def initialize(base_klass)
  @base_klass = base_klass
  @cached_record = {}
  @column_names_with_alias = nil
end

Instance Attribute Details

#base_klass ⇒ Object (readonly)

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.



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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 14

def base_klass
  @base_klass
end

Instance Method Details

#==(other) ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 28

def ==(other)
  raise NotImplementedError
end

#aliased_prefix ⇒ Object

The prefix to be used when aliasing columns in the active_record’s table

Raises:

  • (NotImplementedError) 


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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 38

def aliased_prefix
  raise NotImplementedError
end

#aliased_primary_key ⇒ Object

The alias for the primary key of the active_record’s table



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

def aliased_primary_key
  "#{aliased_prefix}_r0"
end

#aliased_table ⇒ Object 



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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 24

def aliased_table
  Arel::Nodes::TableAlias.new table, aliased_table_name
end

#aliased_table_name ⇒ Object

The alias for the active_record’s table

Raises:

  • (NotImplementedError) 


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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 43

def aliased_table_name
  raise NotImplementedError
end

#column_names_with_alias ⇒ Object

An array of [column_name, alias] pairs for the table



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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 53

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

#extract_record(row) ⇒ Object 



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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 64

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

#instantiate(row) ⇒ Object 



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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 85

def instantiate(row)
  @cached_record[record_id(row)] ||= base_klass.instantiate(extract_record(row))
end

#record_id(row) ⇒ Object 



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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 81

def record_id(row)
  row[aliased_primary_key]
end

#table ⇒ Object

An Arel::Table for the active_record

Raises:

  • (NotImplementedError) 


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# File 'lib/active_record/associations/join_dependency/join_part.rb', line 33

def table
  raise NotImplementedError
end