instance method `exists?`

Ruby on Rails 6.1.7.10

Since v3.0.20

Available in: v3.0.20 v3.1.12 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:

exists?(conditions = :none)

Returns true if a record exists in the table that matches the id or conditions given, or false otherwise. The argument can take six forms:

Integer - Finds the record with this primary key.
String - Finds the record with a primary key corresponding to this string (such as '5').
Array - Finds the record that matches these where-style conditions (such as ['name LIKE ?', "%#{query}%"]).
Hash - Finds the record that matches these where-style conditions (such as {name: 'David'}).
false - Returns always false.
No args - Returns false if the relation is empty, true otherwise.

For more information about specifying conditions as a hash or array, see the Conditions section in the introduction to ActiveRecord::Base.

Note: You can’t pass in a condition as a string (like name = 'Jamie'), since it would be sanitized and then queried against the primary key column, like id = 'name = \'Jamie\''.

Person.exists?(5)
Person.exists?('5')
Person.exists?(['name LIKE ?', "%#{query}%"])
Person.exists?(id: [1, 4, 8])
Person.exists?(name: 'David')
Person.exists?(false)
Person.exists?
Person.where(name: 'Spartacus', rating: 4).exists?

Parameters

conditions opt = :none

Source

# File activerecord/lib/active_record/relation/finder_methods.rb, line 302
    def exists?(conditions = :none)
      if Base === conditions
        raise ArgumentError, <<-MSG.squish
          You are passing an instance of ActiveRecord::Base to `exists?`.
          Please pass the id of the object by calling `.id`.
        MSG
      end

      return false if !conditions || limit_value == 0

      if eager_loading?
        relation = apply_join_dependency(eager_loading: false)
        return relation.exists?(conditions)
      end

      relation = construct_relation_for_exists(conditions)
      return false if relation.where_clause.contradiction?

      skip_query_cache_if_necessary { connection.select_rows(relation.arel, "#{name} Exists?").size == 1 }
    end

Defined in activerecord/lib/active_record/relation/finder_methods.rb line 302 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveRecord::FinderMethods

Signature

Parameters