Revert "Merge pull request #16400 from bogdan/last-with-sql"

This reverts commit 9f3730a516f30beb0050caea9539f8d6b808e58a, reversing
changes made to 2637fb75d82e1c69333855abd58c2470994995d3.

There are additional issues with this commit that need to be addressed
before this change is ready (see #23377). This is a temporary revert in
order for us to have more time to address the issues with that PR,
without blocking the release of beta2.

1 files changed, 22 insertions, 17 deletions

diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 5d4a045097..3f5d6de78a 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -145,23 +145,15 @@ module ActiveRecord
     #
     #   [#<Person id:4>, #<Person id:3>, #<Person id:2>]
     def last(limit = nil)
-      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
+      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
     end
 
     # Same as #last but raises ActiveRecord::RecordNotFound if no record
@@ -531,6 +523,19 @@ 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: