Revert "Merge pull request #27636 from mtsmfm/disable-referential-integrity-without-superuser-privilege-take-2"

This reverts commit c1faca6333abe4b938b98fedc8d1f47b88209ecf, reversing
changes made to 8c658a0ecc7f2b5fc015d424baf9edf6f3eb2b0b.

See https://github.com/rails/rails/pull/27636#issuecomment-297534129

2 files changed, 4 insertions, 49 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
index 730e7c7137..44a7338bf5 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
@@ -6,50 +6,8 @@ module ActiveRecord
           true
         end
 
-        def disable_referential_integrity(&block) # :nodoc:
+        def disable_referential_integrity # :nodoc:
           if supports_disable_referential_integrity?
-            if supports_alter_constraint?
-              disable_referential_integrity_with_alter_constraint(&block)
-            else
-              disable_referential_integrity_with_disable_trigger(&block)
-            end
-          else
-            yield
-          end
-        end
-
-        private
-
-          def disable_referential_integrity_with_alter_constraint
-            tables_constraints = execute(<<-SQL).values
-              SELECT table_name, constraint_name
-              FROM information_schema.table_constraints
-              WHERE constraint_type = 'FOREIGN KEY'
-              AND is_deferrable = 'NO'
-            SQL
-
-            execute(
-              tables_constraints.collect { |table, constraint|
-                "ALTER TABLE #{quote_table_name(table)} ALTER CONSTRAINT #{constraint} DEFERRABLE"
-              }.join(";")
-            )
-
-            begin
-              transaction do
-                execute("SET CONSTRAINTS ALL DEFERRED")
-
-                yield
-              end
-            ensure
-              execute(
-                tables_constraints.collect { |table, constraint|
-                  "ALTER TABLE #{quote_table_name(table)} ALTER CONSTRAINT #{constraint} NOT DEFERRABLE"
-                }.join(";")
-              )
-            end
-          end
-
-          def disable_referential_integrity_with_disable_trigger
             original_exception = nil
 
             begin
@@ -81,7 +39,10 @@ Rails needs superuser privileges to disable referential integrity.
               end
             rescue ActiveRecord::ActiveRecordError
             end
+          else
+            yield
           end
+        end
       end
     end
   end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 7ae9bd9a5f..541013c1e7 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -314,12 +314,6 @@ module ActiveRecord
         postgresql_version >= 90400
       end
 
-      def supports_alter_constraint?
-        # PostgreSQL 9.4 introduces ALTER TABLE ... ALTER CONSTRAINT but it has a bug and fixed in 9.4.2
-        # https://www.postgresql.org/docs/9.4/static/release-9-4-2.html
-        postgresql_version >= 90402
-      end
-
       def get_advisory_lock(lock_id) # :nodoc:
         unless lock_id.is_a?(Integer) && lock_id.bit_length <= 63
           raise(ArgumentError, "Postgres requires advisory lock ids to be a signed 64 bit integer")