Extract `SchemaMigration.all_versions`

Use `SchemaMigration.all_versions` instead of
`SchemaMigration.all.map(&:version)` to avoid to instantiate AR objects.

1 files changed, 5 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/schema_migration.rb b/activerecord/lib/active_record/schema_migration.rb
index 5efbcff96a..f59737afb0 100644
--- a/activerecord/lib/active_record/schema_migration.rb
+++ b/activerecord/lib/active_record/schema_migration.rb
@@ -39,7 +39,11 @@ module ActiveRecord
       end
 
       def normalized_versions
-        pluck(:version).map { |v| normalize_migration_number v }
+        all_versions.map { |v| normalize_migration_number v }
+      end
+
+      def all_versions
+        order(:version).pluck(:version)
       end
     end