Class: Arel::Project

Inherits:
Compound show all
Defined in:
lib/arel/engines/memory/relations/operations.rb,
lib/arel/algebra/relations/operations/project.rb

Instance Attribute Summary

Attributes inherited from Compound

#relation

Attributes included from Relation

#count

Instance Method Summary collapse

Methods inherited from Compound

#build_query, #engine, #eql?, #hash, requires, #unoperated_rows

Methods included from Relation

#bind, #call, #christener, #compiler, #exclusion_predicate_sql, #externalize, #inclusion_predicate_sql, #join?, #primary_key, #session, #to_sql

Methods included from Relation::DefaultOperations

#groupings, #havings, #inserts, #joins, #locked, #orders, #projections, #skipped, #sources, #taken, #wheres

Methods included from Relation::AttributeAccessable

#[], #find_attribute_matching_attribute, #find_attribute_matching_name, #position_of

Methods included from Relation::Operable

#alias, #join, #lock, #outer_join

Methods included from Relation::Operable::Writable

#delete, #insert, #update

Methods included from Relation::Enumerable

#each, #first

Constructor Details

#initialize(relation, *projections, &block) ⇒ Project

Returns a new instance of Project.



6
7
8
9
10
 
# File 'lib/arel/algebra/relations/operations/project.rb', line 6

def initialize(relation, *projections, &block)
  @relation = relation
  @projections = (projections + arguments_from_block(relation, &block)) \
    .collect { |p| p.bind(relation) }
end

Instance Method Details

#attributes ⇒ Object 



12
13
14
 
# File 'lib/arel/algebra/relations/operations/project.rb', line 12

def attributes
  @attributes ||= Header.new(projections).bind(self)
end

#eval ⇒ Object 



18
19
20
 
# File 'lib/arel/engines/memory/relations/operations.rb', line 18

def eval
  unoperated_rows.collect { |r| r.slice(*projections) }
end

#externalizable? ⇒ Boolean

Returns:

  • (Boolean) 


16
17
18
 
# File 'lib/arel/algebra/relations/operations/project.rb', line 16

def externalizable?
  attributes.any? { |a| a.respond_to?(:aggregation?) && a.aggregation? } || relation.externalizable?
end