diff options
Diffstat (limited to 'activerecord/lib/active_record/relation/finder_methods.rb')
| -rw-r--r-- | activerecord/lib/active_record/relation/finder_methods.rb | 96 |
1 files changed, 72 insertions, 24 deletions
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb index 3f5d6de78a..27dd0b4143 100644 --- a/activerecord/lib/active_record/relation/finder_methods.rb +++ b/activerecord/lib/active_record/relation/finder_methods.rb @@ -42,10 +42,10 @@ module ActiveRecord # Person.find_by(name: 'Spartacus', rating: 4) # # returns the first item or nil. # - # Person.where(name: 'Spartacus', rating: 4).first_or_initialize + # Person.find_or_initialize_by(name: 'Spartacus', rating: 4) # # returns the first item or returns a new instance (requires you call .save to persist against the database). # - # Person.where(name: 'Spartacus', rating: 4).first_or_create + # Person.find_or_create_by(name: 'Spartacus', rating: 4) # # returns the first item or creates it and returns it. # # ==== Alternatives for #find @@ -145,15 +145,21 @@ module ActiveRecord # # [#<Person id:4>, #<Person id:3>, #<Person id:2>] def last(limit = nil) - if limit - if order_values.empty? && primary_key - order(arel_table[primary_key].desc).limit(limit).reverse - else - to_a.last(limit) - end - else - find_last - end + return find_last(limit) if loaded? || limit_value + + result = limit(limit || 1) + result.order!(arel_attribute(primary_key)) if order_values.empty? && primary_key + result = result.reverse_order! + + limit ? result.reverse : result.first + rescue ActiveRecord::IrreversibleOrderError + ActiveSupport::Deprecation.warn(<<-WARNING.squish) + Finding a last element by loading the relation when SQL ORDER + can not be reversed is deprecated. + Rails 5.1 will raise ActiveRecord::IrreversibleOrderError in this case. + Please call `to_a.last` if you still want to load the relation. + WARNING + find_last(limit) end # Same as #last but raises ActiveRecord::RecordNotFound if no record @@ -242,6 +248,38 @@ module ActiveRecord find_nth! 41 end + # Find the third-to-last record. + # If no order is defined it will order by primary key. + # + # Person.third_to_last # returns the third-to-last object fetched by SELECT * FROM people + # Person.offset(3).third_to_last # returns the third-to-last object from OFFSET 3 + # Person.where(["user_name = :u", { u: user_name }]).third_to_last + def third_to_last + find_nth_from_last 3 + end + + # Same as #third_to_last but raises ActiveRecord::RecordNotFound if no record + # is found. + def third_to_last! + find_nth_from_last 3 or raise RecordNotFound.new("Couldn't find #{@klass.name} with [#{arel.where_sql(@klass.arel_engine)}]") + end + + # Find the second-to-last record. + # If no order is defined it will order by primary key. + # + # Person.second_to_last # returns the second-to-last object fetched by SELECT * FROM people + # Person.offset(3).second_to_last # returns the second-to-last object from OFFSET 3 + # Person.where(["user_name = :u", { u: user_name }]).second_to_last + def second_to_last + find_nth_from_last 2 + end + + # Same as #second_to_last but raises ActiveRecord::RecordNotFound if no record + # is found. + def second_to_last! + find_nth_from_last 2 or raise RecordNotFound.new("Couldn't find #{@klass.name} with [#{arel.where_sql(@klass.arel_engine)}]") + end + # 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: # @@ -298,7 +336,7 @@ module ActiveRecord end # This method is called whenever no records are found with either a single - # id or multiple ids and raises a ActiveRecord::RecordNotFound exception. + # id or multiple ids and raises an ActiveRecord::RecordNotFound exception. # # The error message is different depending on whether a single id or # multiple ids are provided. If multiple ids are provided, then the number @@ -468,7 +506,7 @@ module ActiveRecord def find_some_ordered(ids) ids = ids.slice(offset_value || 0, limit_value || ids.size) || [] - result = except(:limit, :offset).where(primary_key => ids).to_a + result = except(:limit, :offset).where(primary_key => ids).records if result.size == ids.size pk_type = @klass.type_for_attribute(primary_key) @@ -484,7 +522,7 @@ module ActiveRecord if loaded? @records.first else - @take ||= limit(1).to_a.first + @take ||= limit(1).records.first end end @@ -514,7 +552,7 @@ module ActiveRecord # TODO: once the offset argument is removed from find_nth, # find_nth_with_limit_and_offset can be merged into this method relation = if order_values.empty? && primary_key - order(arel_table[primary_key].asc) + order(arel_attribute(primary_key).asc) else self end @@ -523,19 +561,25 @@ module ActiveRecord relation.limit(limit).to_a end - def find_last + def find_nth_from_last(index) if loaded? - @records.last + @records[-index] else - @last ||= - if limit_value - to_a.last - else - reverse_order.limit(1).to_a.first - end + relation = if order_values.empty? && primary_key + order(arel_attribute(primary_key).asc) + else + self + end + + relation.to_a[-index] + # TODO: can be made more performant on large result sets by + # for instance, last(index)[-index] (which would require + # refactoring the last(n) finder method to make test suite pass), + # or by using a combination of reverse_order, limit, and offset, + # e.g., reverse_order.offset(index-1).first end end - + private def find_nth_with_limit_and_offset(index, limit, offset:) # :nodoc: @@ -546,5 +590,9 @@ module ActiveRecord find_nth_with_limit(index, limit) end end + + def find_last(limit) + limit ? records.last(limit) : records.last + end end end |