instance method
pluck
Ruby on Rails 4.2.9
Since v3.2.22.5Signature
pluck(*column_names)Use pluck as a shortcut to select one or more attributes without loading a bunch of records just to grab the attributes you want.
Person.pluck(:name)
instead of
Person.all.map(&:name)
Pluck returns an Array of attribute values type-casted to match the plucked column names, if they can be deduced. Plucking an SQL fragment returns String values by default.
Person.pluck(:id) # SELECT people.id FROM people # => [1, 2, 3] Person.pluck(:id, :name) # SELECT people.id, people.name FROM people # => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']] Person.pluck('DISTINCT role') # SELECT DISTINCT role FROM people # => ['admin', 'member', 'guest'] Person.where(age: 21).limit(5).pluck(:id) # SELECT people.id FROM people WHERE people.age = 21 LIMIT 5 # => [2, 3] Person.pluck('DATEDIFF(updated_at, created_at)') # SELECT DATEDIFF(updated_at, created_at) FROM people # => ['0', '27761', '173']
Parameters
-
column_namesrest
Source
# File activerecord/lib/active_record/relation/calculations.rb, line 170
def pluck(*column_names)
column_names.map! do |column_name|
if column_name.is_a?(Symbol) && attribute_alias?(column_name)
attribute_alias(column_name)
else
column_name.to_s
end
end
if has_include?(column_names.first)
construct_relation_for_association_calculations.pluck(*column_names)
else
relation = spawn
relation.select_values = column_names.map { |cn|
columns_hash.key?(cn) ? arel_table[cn] : cn
}
result = klass.connection.select_all(relation.arel, nil, relation.arel.bind_values + bind_values)
result.cast_values(klass.column_types)
end
end
Defined in activerecord/lib/active_record/relation/calculations.rb line 170
· View on GitHub
· Improve this page
· Find usages on GitHub
Defined in ActiveRecord::Calculations