Class: ActiveRecord::UnionRelation::Subquery

Inherits:
Object
  • Object
show all
Defined in:
lib/active_record/union_relation.rb

Overview

This represents a combination of an ActiveRecord::Relation and a set of columns that it will pull.

Constant Summary collapse

NULL =

Sometimes you need some columns in some subqeries that you don’t need in others. In order to accomplish that and still maintain the matching number of columns, you can put a null in space of a column instead.

Arel.sql('NULL')

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(relation, sources) ⇒ Subquery

Returns a new instance of Subquery.



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# File 'lib/active_record/union_relation.rb', line 38

def initialize(relation, sources)
  @relation = relation
  @model_name = relation.model.name
  @sources = sources.map { |source| source ? source.to_s : NULL }
end

Instance Attribute Details

#model_name ⇒ Object (readonly)

Returns the value of attribute model_name.



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# File 'lib/active_record/union_relation.rb', line 36

def model_name
  @model_name
end

#relation ⇒ Object (readonly)

Returns the value of attribute relation.



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# File 'lib/active_record/union_relation.rb', line 36

def relation
  @relation
end

#sources ⇒ Object (readonly)

Returns the value of attribute sources.



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# File 'lib/active_record/union_relation.rb', line 36

def sources
  @sources
end

Instance Method Details

#to_arel(columns, discriminator) ⇒ Object 



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# File 'lib/active_record/union_relation.rb', line 44

def to_arel(columns, discriminator)
  relation
    .select(
      Arel.sql("'#{model_name}'").as(quote_column_name(discriminator)),
      *sources.zip(columns).map do |(source, column)|
        Arel.sql(source.to_s).as(quote_column_name(column))
      end
    )
    .arel
end

#to_mapping(columns) ⇒ Object 



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# File 'lib/active_record/union_relation.rb', line 55

def to_mapping(columns)
  [model_name, columns.zip(sources).to_h]
end