q# This is a combination of 2 commits.

MDEV-31503 ALTER SEQUENCE ends up in optimistic parallel slave binlog out-of-order

The OOO error still was possible even after MDEV-31077. This time
it occured through open_table() when the sequence table was not in
the table cache *and* the table was created before the last server
restart.
In such context a internal (read-only) transaction is committed
and it was not blocked from doing a wakeup() call to subsequent
transactions.

Fixed with extending suspend_subsequent_commits() effect for the entirety
of Sql_cmd_alter_sequence::execute().
An elaborated MDEV-31077 test proves the fixes of both failure scenarios.

Also the bug condition suggests a workaround to pre-SELECT sequence
tables before START SLAVE.
Reviewed-by: Brandon Nesterenko <brandon.nesterenko@mariadb.com>

mysql-test/suite/rpl/r/rpl_parallel_seq.result

@@ -47,11 +47,21 @@ Warnings:
 Note	1255	Slave already has been stopped
 RESET MASTER;
 SET @@global.gtid_slave_pos="";
-SET @@global.gtid_strict_mode=1;
 connection master;
 RESET MASTER;
 CREATE TABLE ti (a INT) ENGINE=innodb;
 CREATE SEQUENCE s2 ENGINE=innodb;
+include/save_master_gtid.inc
+connection slave;
+include/start_slave.inc
+include/sync_with_master_gtid.inc
+include/stop_slave.inc
+include/rpl_restart_server.inc [server_number=2]
+SET @@global.slave_parallel_threads=2;
+SET @@global.slave_parallel_mode=optimistic;
+SET @@global.debug_dbug="+d,hold_worker_on_schedule";
+SET @@global.gtid_strict_mode=1;
+connection master;
 SET @@gtid_seq_no=100;
 ALTER SEQUENCE s2 restart with 1;
 INSERT INTO ti SET a=1;
@@ -60,6 +70,7 @@ SELECT @@global.gtid_binlog_state "Master gtid state";
 Master gtid state
 0-1-101
 connection slave;
+SET STATEMENT sql_log_bin=0 FOR FLUSH TABLES;
 include/start_slave.inc
 SELECT @@global.gtid_binlog_state, @@global.gtid_slave_pos as "no 100,101 yet in both";
 @@global.gtid_binlog_state	no 100,101 yet in both

mysql-test/suite/rpl/t/rpl_parallel_seq.test

@@ -77,15 +77,28 @@ SET DEBUG_SYNC = 'now SIGNAL continue_worker';
 --source include/stop_slave.inc
 RESET MASTER;
 SET @@global.gtid_slave_pos="";
---let $slave_gtid_strict_mode=`select @@global.gtid_strict_mode`
-SET @@global.gtid_strict_mode=1;
 --connection master
 RESET MASTER;
 
 # Load from master
 CREATE TABLE ti (a INT) ENGINE=innodb;
 CREATE SEQUENCE s2 ENGINE=innodb;
+--source include/save_master_gtid.inc
+
+--connection slave
+--source include/start_slave.inc
+--source include/sync_with_master_gtid.inc
+--source include/stop_slave.inc
+--let $rpl_server_number= 2
+--source include/rpl_restart_server.inc
+# upon restart
+SET @@global.slave_parallel_threads=2;
+SET @@global.slave_parallel_mode=optimistic;
+SET @@global.debug_dbug="+d,hold_worker_on_schedule";
+--let $slave_gtid_strict_mode=`select @@global.gtid_strict_mode`
+SET @@global.gtid_strict_mode=1;
 
+--connection master
 SET @@gtid_seq_no=100;
 ALTER SEQUENCE s2 restart with 1;
 INSERT INTO ti SET a=1;
@@ -93,6 +106,10 @@ INSERT INTO ti SET a=1;
 SELECT @@global.gtid_binlog_state "Master gtid state";
 
 --connection slave
+# The following FT complicates the opening table time with committing
+# an internal transaction. The rest of the test also proves
+# MDEV-31503 "branch" of the OOO error is fixed.
+SET STATEMENT sql_log_bin=0 FOR FLUSH TABLES;
 --source include/start_slave.inc
 
 --let $wait_condition= SELECT count(*) = 1 FROM information_schema.processlist WHERE state LIKE "Waiting for prior transaction to commit"

sql/sql_sequence.cc

@@ -900,6 +900,20 @@ int SEQUENCE::set_value(TABLE *table, longlong next_val, ulonglong next_round,
   DBUG_RETURN(error);
 }
 
+#if defined(HAVE_REPLICATION)
+class wait_for_commit_raii
+{
+private:
+  THD *m_thd;
+  wait_for_commit *m_wfc;
+
+public:
+  wait_for_commit_raii(THD* thd) :
+      m_thd(thd), m_wfc(thd->suspend_subsequent_commits())
+    {}
+  ~wait_for_commit_raii() { m_thd->resume_subsequent_commits(m_wfc); }
+};
+#endif
 
 bool Sql_cmd_alter_sequence::execute(THD *thd)
 {
@@ -912,7 +926,10 @@ bool Sql_cmd_alter_sequence::execute(THD *thd)
   SEQUENCE *seq;
   No_such_table_error_handler no_such_table_handler;
   DBUG_ENTER("Sql_cmd_alter_sequence::execute");
-
+#if defined(HAVE_REPLICATION)
+  /* No wakeup():s of subsequent commits is allowed in this function. */
+  wait_for_commit_raii suspend_wfc(thd);
+#endif
 
   if (check_access(thd, ALTER_ACL, first_table->db.str,
                    &first_table->grant.privilege,
@@ -1010,19 +1027,15 @@ bool Sql_cmd_alter_sequence::execute(THD *thd)
   else
     table->file->print_error(error, MYF(0));
   table->s->sequence->write_unlock(table);
-  {
-    wait_for_commit* suspended_wfc= thd->suspend_subsequent_commits();
-    if (trans_commit_stmt(thd))
-      error= 1;
-    if (trans_commit_implicit(thd))
-      error= 1;
-    thd->resume_subsequent_commits(suspended_wfc);
-    DBUG_EXECUTE_IF("hold_worker_on_schedule",
-                    {
-                      /* delay binlogging of a parent trx in rpl_parallel_seq */
-                      my_sleep(100000);
-                    });
-  }
+  if (trans_commit_stmt(thd))
+    error= 1;
+  if (trans_commit_implicit(thd))
+    error= 1;
+  DBUG_EXECUTE_IF("hold_worker_on_schedule",
+                  {
+                    /* delay binlogging of a parent trx in rpl_parallel_seq */
+                    my_sleep(100000);
+                  });
   if (likely(!error))
     error= write_bin_log(thd, 1, thd->query(), thd->query_length());
   if (likely(!error))