instance method
pluck
Ruby on Rails 5.2.8.1
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(:name) # SELECT people.name FROM people # => ['David', 'Jeremy', 'Jose'] Person.pluck(:id, :name) # SELECT people.id, people.name FROM people # => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']] Person.distinct.pluck(: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']
See also #ids.
Parameters
-
column_namesrest
Source
# File activerecord/lib/active_record/relation/calculations.rb, line 185
def pluck(*column_names)
if loaded? && (column_names.map(&:to_s) - @klass.attribute_names - @klass.attribute_aliases.keys).empty?
return records.pluck(*column_names)
end
if has_include?(column_names.first)
relation = apply_join_dependency
relation.pluck(*column_names)
else
klass.enforce_raw_sql_whitelist(column_names)
relation = spawn
relation.select_values = column_names
result = skip_query_cache_if_necessary { klass.connection.select_all(relation.arel, nil) }
result.cast_values(klass.attribute_types)
end
end
Defined in activerecord/lib/active_record/relation/calculations.rb line 185
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Defined in ActiveRecord::Calculations