build_subselect does not have ordering

[koic]

Fixes #2023.

This PR fixes ActiveRecord::StatementInvalid: OCIError: ORA-00907: missing right parenthesis error when using assoc has dependent: :delete_all and order.

has_many :assoc, -> { order(:foo) }, dependent: :delete_all

Oracle does not accept ORDER BY in DELETE and UPDATE's subquery. This PR adds the following reproduction test and passes it.

vagrant@rails-dev-box:~/src/oracle-enhanced$ bundle exec rspec
spec/active_record/connection_adapters/oracle_enhanced_adapter_spec.rb:187
==> Loading config from ENV or use default
==> Running specs with ruby version 2.7.2
==> Effective ActiveRecord version 6.1.0.rc1
Run options: include
{:locations=>{"./spec/active_record/connection_adapters/oracle_enhanced_adapter_spec.rb"=>[187]}}
F

Failures:

  1) OracleEnhancedAdapter `has_many` assoc has `dependent: :delete_all`
  with `order` should load included association with more than 1000
  records
     Failure/Error: @raw_cursor.exec

     ActiveRecord::StatementInvalid: OCIError: ORA-00907: missing right parenthesis
     # stmt.c:267:in oci8lib_270.so
     # /home/vagrant/.rvm/gems/ruby-2.7.2/bundler/gems/ruby-oci8-446ad166808c/lib/oci8/cursor.rb:137:in `exec'
     # ./lib/active_record/connection_adapters/oracle_enhanced/oci_connection.rb:150:in `exec_update'
     # ./lib/active_record/connection_adapters/oracle_enhanced/database_statements.rb:158:in `block (2 levels) in exec_update'

[yahonda]

Thanks for the pull request. What do you think about this change? It clearly shows the differences from other database drivers that Oracle DML does not support order by in subqueries.

$ git diff
diff --git a/lib/arel/visitors/oracle.rb b/lib/arel/visitors/oracle.rb
index 55830bd6..5bb59326 100644
--- a/lib/arel/visitors/oracle.rb
+++ b/lib/arel/visitors/oracle.rb
@@ -255,13 +255,7 @@ module Arel # :nodoc: all
         # This method has been overridden based on the following code.
         # https://github.com/rails/rails/blob/v6.1.0.rc1/activerecord/lib/arel/visitors/to_sql.rb#L815-L825
         def build_subselect(key, o)
-          stmt             = Nodes::SelectStatement.new
-          core             = stmt.cores.first
-          core.froms       = o.relation
-          core.wheres      = o.wheres
-          core.projections = [key]
-          stmt.limit       = o.limit
-          stmt.offset      = o.offset
+          stmt = super
           stmt.orders      = [] # `orders` will never be set to prevent `ORA-00907`.
           stmt
         end
diff --git a/lib/arel/visitors/oracle12.rb b/lib/arel/visitors/oracle12.rb
index 76a1b371..b08ee2bb 100644
--- a/lib/arel/visitors/oracle12.rb
+++ b/lib/arel/visitors/oracle12.rb
@@ -162,13 +162,7 @@ module Arel # :nodoc: all
         # This method has been overridden based on the following code.
         # https://github.com/rails/rails/blob/v6.1.0.rc1/activerecord/lib/arel/visitors/to_sql.rb#L815-L825
         def build_subselect(key, o)
-          stmt             = Nodes::SelectStatement.new
-          core             = stmt.cores.first
-          core.froms       = o.relation
-          core.wheres      = o.wheres
-          core.projections = [key]
-          stmt.limit       = o.limit
-          stmt.offset      = o.offset
+          stmt = super
           stmt.orders      = [] # `orders` will never be set to prevent `ORA-00907`.
           stmt
         end
$

[koic]

Wow, super cool suggestion! I updated this PR.

[causztic]

is it possible to cut this for a patch version update pre 6.1.0?
Currently on this merged commit it targets 6.1 but I'm currently facing this issue on 6.0.3.3.

I am in the midst of upgrading my application from rails 5 to 6 so I don't want to jump to 6.1 immediately

[yahonda]

I understand your concern. Technically, this pull request is not feasible to backport because the Arel file has been migrated from Rails code to Oracle enhanced adapter via #2002 which is only available for Oracle enhanced adapter 6.1.x and above.

Let me consider if I can take some options.

[causztic]

Thank you - let me know if there is anything I can do to help as well