instance method `pluck`

Ruby on Rails 8.1.2

Since v3.2.22.5

Available in: v3.2.22.5 v4.0.13 v4.1.16 v4.2.9 v5.2.8.1 v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

pluck(*column_names)

Use #pluck as a shortcut to select one or more attributes without loading an entire record object per row.

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]

Comment.joins(:person).pluck(:id, person: :id)
# SELECT comments.id, person.id FROM comments INNER JOIN people person ON person.id = comments.person_id
# => [[1, 2], [2, 2]]

Comment.joins(:person).pluck(:id, person: [:id, :name])
# SELECT comments.id, person.id, person.name FROM comments INNER JOIN people person ON person.id = comments.person_id
# => [[1, 2, 'David'], [2, 2, 'David']]

Person.pluck(Arel.sql('DATEDIFF(updated_at, created_at)'))
# SELECT DATEDIFF(updated_at, created_at) FROM people
# => ['0', '27761', '173']

Be aware that #pluck ignores any previous select clauses

Person.select(:name).pluck(:id)
# SELECT people.id FROM people

Parameters

column_names rest

Source

# File activerecord/lib/active_record/relation/calculations.rb, line 295
    def pluck(*column_names)
      if @none
        if @async
          return Promise::Complete.new([])
        else
          return []
        end
      end

      if loaded? && all_attributes?(column_names)
        result = records.pluck(*column_names)
        if @async
          return Promise::Complete.new(result)
        else
          return result
        end
      end

      if has_include?(column_names.first)
        relation = apply_join_dependency
        relation.pluck(*column_names)
      else
        model.disallow_raw_sql!(flattened_args(column_names))
        relation = spawn
        columns = relation.arel_columns(column_names)
        relation.select_values = columns
        result = skip_query_cache_if_necessary do
          if where_clause.contradiction? && !possible_aggregation?(column_names)
            ActiveRecord::Result.empty(async: @async)
          else
            model.with_connection do |c|
              c.select_all(relation.arel, "#{model.name} Pluck", async: @async)
            end
          end
        end
        result.then do |result|
          type_cast_pluck_values(result, columns)
        end
      end
    end

Defined in activerecord/lib/active_record/relation/calculations.rb line 295 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveRecord::Calculations

Signature

Parameters