fix: strip schema from sequence name

sequence_name is shared across threads because it is stored in a class
ivar. This means that on threaded servers, the sequence_name might point
to a different tenant, if another tenant made the switch at the right
time. This race is likely the cause of
#81 as well.

This reverts commit f8eefc4.

lib/apartment.rb

@@ -8,6 +8,7 @@
 
 require_relative 'apartment/log_subscriber'
 
+require_relative 'apartment/active_record/postgresql_adapter'
 if ActiveRecord.version.release >= Gem::Version.new('6.0')
   require_relative 'apartment/active_record/connection_handling'
 end

lib/apartment/active_record/postgresql_adapter.rb

@@ -0,0 +1,16 @@
+module Apartment::PostgreSqlAdapterPatch
+  def default_sequence_name(table, _column)
+    res = super
+    schema_prefix = "#{Apartment::Tenant.current}."
+    if res.starts_with?(schema_prefix) && Apartment.excluded_models.none?{|m| m.constantize.table_name == table}
+      res.delete_prefix!("#{Apartment::Tenant.current}.")
+    end
+    res
+  end
+end
+
+require 'active_record/connection_adapters/postgresql_adapter'
+
+class ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
+  include Apartment::PostgreSqlAdapterPatch
+end

lib/apartment/adapters/postgresql_adapter.rb

@@ -41,7 +41,6 @@ def default_tenant
       def reset
         @current = default_tenant
         Apartment.connection.schema_search_path = full_search_path
-        reset_sequence_names
       end
 
       def init
@@ -83,7 +82,6 @@ def connect_to_new(tenant = nil)
         # there is a issue for prepared statement with changing search_path.
         # https://www.postgresql.org/docs/9.3/static/sql-prepare.html
         Apartment.connection.clear_cache! if postgresql_version < 90_300
-        reset_sequence_names
       rescue *rescuable_exceptions
         raise TenantNotFound, "One of the following schema(s) is invalid: \"#{tenant}\" #{full_search_path}"
       end
@@ -131,24 +129,6 @@ def postgresql_version
         # public from Rails 5.0.
         Apartment.connection.send(:postgresql_version)
       end
-
-      def reset_sequence_names
-        # sequence_name contains the schema, so it must be reset after switch
-        # There is `reset_sequence_name`, but that method actually goes to the database
-        # to find out the new name. Therefore, we do this hack to only unset the name,
-        # and it will be dynamically found the next time it is needed
-        descendants_to_unset = ActiveRecord::Base.descendants
-                                                 .select { |c| c.instance_variable_defined?(:@sequence_name) }
-                                                 .reject do |c|
-                                                   c.instance_variable_defined?(:@explicit_sequence_name) &&
-                                                     c.instance_variable_get(:@explicit_sequence_name)
-                                                 end
-        descendants_to_unset.each do |c|
-          # NOTE: due to this https://github.com/rails-on-services/apartment/issues/81
-          # unreproduceable error we're checking before trying to remove it
-          c.remove_instance_variable :@sequence_name if c.instance_variable_defined?(:@sequence_name)
-        end
-      end
     end
 
     # Another Adapter for Postgresql when using schemas and SQL

spec/examples/schema_adapter_examples.rb

@@ -27,13 +27,19 @@
       Apartment::Tenant.init
 
       expect(Company.table_name).to eq('public.companies')
+      expect(User.table_name).to eq('users')
+      expect(Company.sequence_name).to eq('public.companies_id_seq')
+      expect(User.sequence_name).to eq('users_id_seq')
     end
 
     context 'with a default_tenant', default_tenant: true do
       it 'should set the proper table_name on excluded_models' do
         Apartment::Tenant.init
 
         expect(Company.table_name).to eq("#{default_tenant}.companies")
+        expect(User.table_name).to eq('users')
+        expect(Company.sequence_name).to eq("#{default_tenant}.companies_id_seq")
+        expect(User.sequence_name).to eq('users_id_seq')
       end
 
       it 'sets the search_path correctly' do
@@ -121,11 +127,9 @@
     it 'connects and resets' do
       subject.switch(schema1) do
         expect(connection.schema_search_path).to start_with %("#{schema1}")
-        expect(User.sequence_name).to eq "#{schema1}.#{User.table_name}_id_seq"
       end
 
       expect(connection.schema_search_path).to start_with %("#{public_schema}")
-      expect(User.sequence_name).to eq "#{public_schema}.#{User.table_name}_id_seq"
     end
   end