From 044ca74ea9b849c27131d1a1df34add05b46dd74 Mon Sep 17 00:00:00 2001
From: Joe James <191664+the-undefined@users.noreply.github.com>
Date: Fri, 19 Jun 2020 13:37:37 +0100
Subject: [PATCH] Allow unmanaged autogenerated sequence names

To still support primary keys through db triggers, without adding back in
support for generating and maintaining them with migrations, add an
configuration boolen:

    unmanaged_autogenerated_sequences = false # default

Which can be used in an initializer file. When set to `true` there will not be
an exception raised when the sequence name is defined in the model with the
previously supported value:

   self.sequence_name = :autogenerated

This option allows for dbs managed outside of the application to use triggers
for primary keys. Without the `autogenerated` option an error is raised when
inserting the record:

    ORA-02289: sequence does not exist
---
 .../connection_adapters/oracle_enhanced_adapter.rb   | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb b/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb
index eca568235..749a189ec 100644
--- a/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb
+++ b/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb
@@ -212,6 +212,17 @@ class OracleEnhancedAdapter < AbstractAdapter
       cattr_accessor :default_sequence_start_value
       self.default_sequence_start_value = 1
 
+      ##
+      # :singleton-method:
+      # By default trigger based sequences are not supported.
+      # Enable this if you wish to manage your own primary key triggers, then you can avoid an
+      # exception being raised when using autogenerated sequence names in your ActiveRecord models:
+      #
+      #     self.sequence_name = :autogenerated
+      #
+      cattr_accessor :unmanaged_autogenerated_sequences
+      self.unmanaged_autogenerated_sequences = false
+
       ##
       # :singleton-method:
       # By default, OracleEnhanced adapter will use longer 128 bytes identifier
@@ -493,6 +504,7 @@ def discard!
       # called directly; used by ActiveRecord to get the next primary key value
       # when inserting a new database record (see #prefetch_primary_key?).
       def next_sequence_value(sequence_name)
+        return nil if unmanaged_autogenerated_sequences
         # if sequence_name is set to :autogenerated then it means that primary key will be populated by trigger
         raise ArgumentError.new "Trigger based primary key is not supported" if sequence_name == AUTOGENERATED_SEQUENCE_NAME
         # call directly connection method to avoid prepared statement which causes fetching of next sequence value twice