diff options
| -rw-r--r-- | activerecord/CHANGELOG.md | 20 | ||||
| -rw-r--r-- | activerecord/lib/active_record/relation/finder_methods.rb | 39 | ||||
| -rw-r--r-- | activerecord/test/cases/finder_test.rb | 32 |
3 files changed, 60 insertions, 31 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md index 50a0b291b3..faab0f9554 100644 --- a/activerecord/CHANGELOG.md +++ b/activerecord/CHANGELOG.md @@ -1,3 +1,23 @@ +* Rework `ActiveRecord::Relation#last` + + 1. Always find last with ruby if relation is loaded + 2. Always use SQL instead if relation is not loaded. + 3. Deprecated relation loading when SQL order can not be automatically reversed + + Topic.order("title").load.last(3) + # before: SELECT ... + # after: No SQL + + Topic.order("title").last + # before: SELECT * FROM `topics` + # after: SELECT * FROM `topics` ORDER BY `topics`.`title` DESC LIMIT 1 + + Topic.order("coalesce(author, title)").last + # before: SELECT * FROM `topics` + # after: Deprecation Warning for irreversible order + + *Bogdan Gusiev* + * `ActiveRecord::Relation#reverse_order` throws `ActiveRecord::IrreversibleOrderError` when the order can not be reversed using current trivial algorithm. Also raises the same error when `#reverse_order` is called on diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb index 3f5d6de78a..5d4a045097 100644 --- a/activerecord/lib/active_record/relation/finder_methods.rb +++ b/activerecord/lib/active_record/relation/finder_methods.rb @@ -145,15 +145,23 @@ 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? + + result = order_values.empty? && primary_key ? order(arel_table[primary_key].desc) : reverse_order + result = result.limit!(limit || 1) + 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 + + def find_last(limit) + limit ? to_a.last(limit) : to_a.last end # Same as #last but raises ActiveRecord::RecordNotFound if no record @@ -523,19 +531,6 @@ module ActiveRecord relation.limit(limit).to_a end - def find_last - if loaded? - @records.last - else - @last ||= - if limit_value - to_a.last - else - reverse_order.limit(1).to_a.first - end - end - end - private def find_nth_with_limit_and_offset(index, limit, offset:) # :nodoc: diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb index 75a74c052d..cbeb37dd22 100644 --- a/activerecord/test/cases/finder_test.rb +++ b/activerecord/test/cases/finder_test.rb @@ -506,7 +506,7 @@ class FinderTest < ActiveRecord::TestCase end end - def test_take_and_first_and_last_with_integer_should_use_sql_limit + def test_take_and_first_and_last_with_integer_should_use_sql assert_sql(/LIMIT|ROWNUM <=/) { Topic.take(3).entries } assert_sql(/LIMIT|ROWNUM <=/) { Topic.first(2).entries } assert_sql(/LIMIT|ROWNUM <=/) { Topic.last(5).entries } @@ -516,16 +516,30 @@ class FinderTest < ActiveRecord::TestCase assert_equal Topic.order("title").to_a.last(2), Topic.order("title").last(2) end - def test_last_with_integer_and_order_should_not_use_sql_limit - query = assert_sql { Topic.order("title").last(5).entries } - assert_equal 1, query.length - assert_no_match(/LIMIT/, query.first) + def test_last_with_integer_and_order_should_use_sql + relation = Topic.order("title") + assert_queries(1) { relation.last(5) } + assert !relation.loaded? end - def test_last_with_integer_and_reorder_should_not_use_sql_limit - query = assert_sql { Topic.reorder("title").last(5).entries } - assert_equal 1, query.length - assert_no_match(/LIMIT/, query.first) + def test_last_with_integer_and_reorder_should_use_sql + relation = Topic.reorder("title") + assert_queries(1) { relation.last(5) } + assert !relation.loaded? + end + + def test_last_on_loaded_relation_should_not_use_sql + relation = Topic.limit(10).load + assert_no_queries do + relation.last + relation.last(2) + end + end + + def test_last_with_irreversible_order + assert_deprecated do + Topic.order("coalesce(author_name, title)").last + end end def test_take_and_first_and_last_with_integer_should_return_an_array |