Set up replica identity index for context external tools

closes INTEROP-6237
flag=none

Test plan
- Verify that the replica identity index has been
  created
- Verify the replica identity for context_external_tools
  has been set to index (SELECT relname, relreplident
  FROM pg_class WHERE relname = 'context_external_tools';)

Change-Id: Ic9540381a82a1f10b8f930f40bf90b1fdf370aa9
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/252622
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Wagner Goncalves <wagner.goncalves@instructure.com>
QA-Review: Wagner Goncalves <wagner.goncalves@instructure.com>
Product-Review: Mysti Lilla <mysti@instructure.com>

config/initializers/active_record.rb

@@ -1537,7 +1537,7 @@ ActiveRecord::ConnectionAdapters::SchemaStatements.class_eval do
         fk_name_to_delete = foreign_key_for(from_table, **options)&.name
         return if fk_name_to_delete.nil?
       else
-        fk_name_to_delete = foreign_key_for!(from_table, **options).name        
+        fk_name_to_delete = foreign_key_for!(from_table, **options).name
       end
     end
 
@@ -1546,6 +1546,22 @@ ActiveRecord::ConnectionAdapters::SchemaStatements.class_eval do
 
     execute schema_creation.accept(at)
   end
+
+  def add_replica_identity(table_string, column_name, default_value)
+    klass = table_string.constantize
+    DataFixup::BackfillNulls.run(klass, column_name, default_value: default_value)
+    change_column_null klass.table_name, column_name, false
+    primary_column = klass.primary_key
+    index_name = "index_#{klass.table_name}_replica_identity"
+    add_index klass.table_name, [column_name, primary_column], name: index_name, algorithm: :concurrently, unique: true, if_not_exists: true
+    execute(%[ALTER TABLE #{klass.quoted_table_name} REPLICA IDENTITY USING INDEX #{index_name}])
+  end
+
+  def remove_replica_identity(table_string)
+    klass = table_string.constantize
+    execute(%[ALTER TABLE #{klass.quoted_table_name} REPLICA IDENTITY DEFAULT])
+    remove_index klass.table_name, name: "index_#{klass.table_name}_replica_identity", if_exists: true
+  end
 end
 
 ActiveRecord::Associations::CollectionAssociation.class_eval do

db/migrate/20201109175600_add_replica_identity_for_context_external_tools.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+#
+# Copyright (C) 2020 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+
+class AddReplicaIdentityForContextExternalTools < ActiveRecord::Migration[5.2]
+  tag :postdeploy
+  disable_ddl_transaction!
+
+  def up
+    add_replica_identity 'ContextExternalTool', :root_account_id, 0
+    remove_index :context_external_tools, name: 'index_context_external_tools_on_root_account_id', if_exists: true
+  end
+
+  def down
+    add_index :context_external_tools, :root_account_id, algorithm: :concurrently, if_not_exists: true
+    remove_replica_identity 'ContextExternalTool'
+    change_column_null :context_external_tools, :root_account_id, true
+  end
+end

spec/lib/data_fixup/populate_root_account_id_on_models_spec.rb

@@ -384,20 +384,6 @@ describe DataFixup::PopulateRootAccountIdOnModels do
       end
     end
 
-    context 'with ContextExternalTool' do
-      it_behaves_like 'a datafixup that populates root_account_id' do
-        let(:record) { external_tool_model(context: @course) }
-        let(:reference_record) { @course }
-      end
-
-      context 'when the tool context is a root account' do
-        it_behaves_like 'a datafixup that populates root_account_id' do
-          let(:record) { external_tool_model(context: @course.root_account) }
-          let(:reference_record) { @course }
-        end
-      end
-    end
-
     context 'with ContentMigration' do
       it 'should populate the root_account_id' do
         cm = @course.content_migrations.create!(user: @user)