MDEV-7974 review/contribution:

gtid record of XA-prepare should no be merged into the replicated
trx. This patch redirects it into the default mysql.gtid_slave_pos table. A test is added.

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

 include/master-slave.inc
 [connection master]
+connection master;
 create table t1 (a int, b int) engine=InnoDB;
 xa start 't';
 insert into t1 values(1, 2);
 xa end 't';
 xa prepare 't';
 xa commit 't';
-select * from t1;
-a	b
-1	2
 connection slave;
-select * from t1;
-a	b
-1	2
+include/diff_tables.inc [master:t1, slave:t1]
 connection master;
 xa start 't';
 insert into t1 values(3, 4);
 xa end 't';
 xa prepare 't';
 xa rollback 't';
-select * from t1;
-a	b
-1	2
 connection slave;
-select * from t1;
-a	b
-1	2
+include/diff_tables.inc [master:t1, slave:t1]
 connection master;
 SET pseudo_slave_mode=1;
 create table t2 (a int) engine=InnoDB;
@@ -37,26 +28,20 @@ xa start 's';
 insert into t2 values (0);
 xa end 's';
 xa prepare 's';
+include/sync_with_master_gtid.inc
+xa recover;
+formatID	gtrid_length	bqual_length	data
+1	1	0	t
+1	1	0	s
+connection master;
 xa commit 't';
 xa commit 's';
 SET pseudo_slave_mode=0;
 Warnings:
 Warning	1231	Slave applier execution mode not active, statement ineffective.
-select * from t1;
-a	b
-1	2
-5	6
-select * from t2;
-a
-0
 connection slave;
-select * from t1;
-a	b
-1	2
-5	6
-select * from t2;
-a
-0
+include/diff_tables.inc [master:t1, slave:t1]
+include/diff_tables.inc [master:t2, slave:t2]
 connection master;
 drop table t1, t2;
 include/rpl_end.inc

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

+include/master-slave.inc
+[connection master]
+connection slave;
+call mtr.add_suppression("The automatically created table.*name may not be entirely in lowercase");
+include/stop_slave.inc
+CHANGE MASTER TO master_use_gtid=slave_pos;
+SET @@global.gtid_pos_auto_engines="innodb";
+include/start_slave.inc
+connection master;
+create table t1 (a int, b int) engine=InnoDB;
+insert into t1 values(0, 0);
+xa start 't';
+insert into t1 values(1, 2);
+xa end 't';
+xa prepare 't';
+xa commit 't';
+connection slave;
+include/diff_tables.inc [master:t1, slave:t1]
+connection master;
+xa start 't';
+insert into t1 values(3, 4);
+xa end 't';
+xa prepare 't';
+xa rollback 't';
+connection slave;
+include/diff_tables.inc [master:t1, slave:t1]
+connection master;
+SET pseudo_slave_mode=1;
+create table t2 (a int) engine=InnoDB;
+xa start 't';
+insert into t1 values (5, 6);
+xa end 't';
+xa prepare 't';
+xa start 's';
+insert into t2 values (0);
+xa end 's';
+xa prepare 's';
+connection slave;
+include/sync_with_master_gtid.inc
+SELECT @@global.gtid_slave_pos = CONCAT(domain_id,"-",server_id,"-",seq_no) FROM mysql.gtid_slave_pos WHERE seq_no = (SELECT DISTINCT max(seq_no) FROM mysql.gtid_slave_pos);
+@@global.gtid_slave_pos = CONCAT(domain_id,"-",server_id,"-",seq_no)
+1
+xa recover;
+formatID	gtrid_length	bqual_length	data
+1	1	0	t
+1	1	0	s
+connection master;
+xa commit 't';
+xa commit 's';
+SET pseudo_slave_mode=0;
+Warnings:
+Warning	1231	Slave applier execution mode not active, statement ineffective.
+connection slave;
+include/diff_tables.inc [master:t1, slave:t1]
+include/diff_tables.inc [master:t2, slave:t2]
+connection master;
+drop table t1, t2;
+connection slave;
+include/stop_slave.inc
+SET @@global.gtid_pos_auto_engines="";
+SET @@session.sql_log_bin=0;
+DROP TABLE mysql.gtid_slave_pos_InnoDB;
+SET @@session.sql_log_bin=1;
+include/start_slave.inc
+include/rpl_end.inc

mysql-test/suite/rpl/t/rpl_xa.inc

+#
+# This "body" file checks general properties of XA transaction replication
+# as of MDEV-7974.
+# Parameters:
+# --let rpl_xa_check= SELECT ...
+#
+connection master;
+create table t1 (a int, b int) engine=InnoDB;
+insert into t1 values(0, 0);
+xa start 't';
+insert into t1 values(1, 2);
+xa end 't';
+xa prepare 't';
+xa commit 't';
+
+sync_slave_with_master;
+let $diff_tables= master:t1, slave:t1;
+source include/diff_tables.inc;
+
+connection master;
+
+xa start 't';
+insert into t1 values(3, 4);
+xa end 't';
+xa prepare 't';
+xa rollback 't';
+
+sync_slave_with_master;
+let $diff_tables= master:t1, slave:t1;
+source include/diff_tables.inc;
+
+connection master;
+SET pseudo_slave_mode=1;
+create table t2 (a int) engine=InnoDB;
+xa start 't';
+insert into t1 values (5, 6);
+xa end 't';
+xa prepare 't';
+xa start 's';
+insert into t2 values (0);
+xa end 's';
+xa prepare 's';
+
+connection slave;
+source include/sync_with_master_gtid.inc;
+if ($rpl_xa_check)
+{
+  --eval $rpl_xa_check
+  if ($rpl_xa_verbose)
+  {
+    --eval SELECT $rpl_xa_check_lhs
+    --eval SELECT $rpl_xa_check_rhs
+  }
+}
+xa recover;
+
+connection master;
+xa commit 't';
+xa commit 's';
+SET pseudo_slave_mode=0;
+
+sync_slave_with_master;
+let $diff_tables= master:t1, slave:t1;
+source include/diff_tables.inc;
+let $diff_tables= master:t2, slave:t2;
+source include/diff_tables.inc;
+
+connection master;
+drop table t1, t2;

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

 source include/have_innodb.inc;
 source include/master-slave.inc;
 
-create table t1 (a int, b int) engine=InnoDB;
-xa start 't';
-insert into t1 values(1, 2);
-xa end 't';
-xa prepare 't';
-xa commit 't';
-select * from t1;
-sync_slave_with_master;
-select * from t1;
-connection master;
-
-xa start 't';
-insert into t1 values(3, 4);
-xa end 't';
-xa prepare 't';
-xa rollback 't';
-select * from t1;
-sync_slave_with_master;
-select * from t1;
-
-connection master;
-SET pseudo_slave_mode=1;
-create table t2 (a int) engine=InnoDB;
-xa start 't';
-insert into t1 values (5, 6);
-xa end 't';
-xa prepare 't';
-xa start 's';
-insert into t2 values (0);
-xa end 's';
-xa prepare 's';
-xa commit 't';
-xa commit 's';
-SET pseudo_slave_mode=0;
-select * from t1;
-select * from t2;
-sync_slave_with_master;
-select * from t1;
-select * from t2;
-
-connection master;
-drop table t1, t2;
+source rpl_xa.inc;
 source include/rpl_end.inc;

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

+--source include/have_innodb.inc
+--source include/master-slave.inc
+
+--connection slave
+call mtr.add_suppression("The automatically created table.*name may not be entirely in lowercase");
+
+--source include/stop_slave.inc
+CHANGE MASTER TO master_use_gtid=slave_pos;
+
+SET @@global.gtid_pos_auto_engines="innodb";
+--source include/start_slave.inc
+--let $rpl_xa_check_lhs= @@global.gtid_slave_pos
+--let $rpl_xa_check_rhs= CONCAT(domain_id,"-",server_id,"-",seq_no) FROM mysql.gtid_slave_pos WHERE seq_no = (SELECT DISTINCT max(seq_no) FROM mysql.gtid_slave_pos)
+--let $rpl_xa_check=SELECT $rpl_xa_check_lhs = $rpl_xa_check_rhs
+--source rpl_xa.inc
+
+--connection slave
+--source include/stop_slave.inc
+SET @@global.gtid_pos_auto_engines="";
+SET @@session.sql_log_bin=0;
+DROP TABLE mysql.gtid_slave_pos_InnoDB;
+SET @@session.sql_log_bin=1;
+--source include/start_slave.inc
+
+--source include/rpl_end.inc