MDEV-22757 Assertion !binlog || exist_hton_without_prepare' failed in...

MDEV-22757 Assertion !binlog || exist_hton_without_prepare' failed in MYSQL_BIN_LOG::unlog_xa_prepare

The assert fired falsely having not captured two more not apparent
possiblities in its condition.

They are masked out hton error out of REPLACE execution (so at later xa-prepare
that engine is still present as read-write) and a prepare-capable engine
which also may not be an actual participant in the xa transation. That
engine, such as SEQUENCE, though does create its own event block.

mysql-test/suite/binlog/r/binlog_empty_xa_prepared.result

@@ -29,3 +29,82 @@ master-bin.000001	#	Query	#	#	XA END X'33',X'',1
 master-bin.000001	#	XA_prepare	#	#	XA PREPARE X'33',X'',1
 master-bin.000001	#	Gtid	#	#	GTID #-#-#
 master-bin.000001	#	Query	#	#	XA ROLLBACK X'33',X'',1
+RESET MASTER;
+CREATE TABLE t1 (a INT) ENGINE=MyISAM;
+CREATE TABLE t2 (id INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1),(2);
+INSERT INTO t2 VALUES (1),(2);
+XA START '1';
+REPLACE INTO t1 SELECT * FROM t1;
+REPLACE INTO t2 SELECT * FROM t2;
+XA END '1';
+XA PREPARE '1';
+XA ROLLBACK '1';
+Warnings:
+Warning	1196	Some non-transactional changed tables couldn't be rolled back
+DROP TABLE t1, t2;
+# Proof of  correct logging incl empty XA-PREPARE
+include/show_binlog_events.inc
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; CREATE TABLE t1 (a INT) ENGINE=MyISAM
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; CREATE TABLE t2 (id INT PRIMARY KEY) ENGINE=InnoDB
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; INSERT INTO t1 VALUES (1),(2)
+master-bin.000001	#	Query	#	#	COMMIT
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; INSERT INTO t2 VALUES (1),(2)
+master-bin.000001	#	Xid	#	#	COMMIT /* XID */
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Annotate_rows	#	#	REPLACE INTO t1 SELECT * FROM t1
+master-bin.000001	#	Table_map	#	#	table_id: # (test.t1)
+master-bin.000001	#	Write_rows_v1	#	#	table_id: # flags: STMT_END_F
+master-bin.000001	#	Query	#	#	COMMIT
+master-bin.000001	#	Gtid	#	#	XA START X'31',X'',1 GTID #-#-#
+master-bin.000001	#	Query	#	#	XA END X'31',X'',1
+master-bin.000001	#	XA_prepare	#	#	XA PREPARE X'31',X'',1
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	XA ROLLBACK X'31',X'',1
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; DROP TABLE `t1`,`t2` /* generated by server */
+RESET MASTER;
+CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1);
+CREATE SEQUENCE s ENGINE=InnoDB;
+XA START '2';
+SELECT NEXT VALUE FOR s;
+NEXT VALUE FOR s
+1
+REPLACE INTO t1 SELECT * FROM t1;
+XA END '2';
+XA PREPARE '2';
+XA ROLLBACK '2';
+DROP SEQUENCE s;
+DROP TABLE t1;
+# Proof of  correct logging incl empty XA-PREPARE
+include/show_binlog_events.inc
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Annotate_rows	#	#	INSERT INTO t1 VALUES (1)
+master-bin.000001	#	Table_map	#	#	table_id: # (test.t1)
+master-bin.000001	#	Write_rows_v1	#	#	table_id: # flags: STMT_END_F
+master-bin.000001	#	Xid	#	#	COMMIT /* XID */
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; CREATE SEQUENCE s ENGINE=InnoDB
+master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
+master-bin.000001	#	Annotate_rows	#	#	SELECT NEXT VALUE FOR s
+master-bin.000001	#	Table_map	#	#	table_id: # (test.s)
+master-bin.000001	#	Write_rows_v1	#	#	table_id: # flags: STMT_END_F
+master-bin.000001	#	Query	#	#	COMMIT
+master-bin.000001	#	Gtid	#	#	XA START X'32',X'',1 GTID #-#-#
+master-bin.000001	#	Query	#	#	XA END X'32',X'',1
+master-bin.000001	#	XA_prepare	#	#	XA PREPARE X'32',X'',1
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	XA ROLLBACK X'32',X'',1
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; DROP SEQUENCE `s` /* generated by server */
+master-bin.000001	#	Gtid	#	#	GTID #-#-#
+master-bin.000001	#	Query	#	#	use `test`; DROP TABLE `t1` /* generated by server */

mysql-test/suite/binlog/t/binlog_empty_xa_prepared.test

@@ -33,3 +33,50 @@ XA ROLLBACK '3';
 
 --echo # Proof of  correct logging incl empty XA-PREPARE
 --source include/show_binlog_events.inc
+
+# The test verifies execution and binary logging of user XA that produce empty
+# XA-PREPARE group of events.
+#
+# MDEV-22757 Assertion `!binlog || exist_hton_without_prepare'
+#            in MYSQL_BIN_LOG::unlog_xa_prepare
+
+RESET MASTER;
+CREATE TABLE t1 (a INT) ENGINE=MyISAM;
+CREATE TABLE t2 (id INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1),(2);
+INSERT INTO t2 VALUES (1),(2);
+
+XA START '1';
+REPLACE INTO t1 SELECT * FROM t1;
+REPLACE INTO t2 SELECT * FROM t2;
+XA END '1';
+XA PREPARE '1';
+
+# Cleanup
+XA ROLLBACK '1';
+DROP TABLE t1, t2;
+
+--echo # Proof of  correct logging incl empty XA-PREPARE
+--source include/show_binlog_events.inc
+
+
+# MDEV-22430 Assertion ... in MYSQL_BIN_LOG::unlog_xa_prepare
+
+RESET MASTER;
+CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1);
+CREATE SEQUENCE s ENGINE=InnoDB;
+
+XA START '2';
+SELECT NEXT VALUE FOR s;
+REPLACE INTO t1 SELECT * FROM t1;
+XA END '2';
+XA PREPARE '2';
+
+# Cleanup
+XA ROLLBACK '2';
+DROP SEQUENCE s;
+DROP TABLE t1;
+
+--echo # Proof of  correct logging incl empty XA-PREPARE
+--source include/show_binlog_events.inc

sql/log.cc

@@ -10218,28 +10218,13 @@ int TC_LOG_BINLOG::unlog_xa_prepare(THD *thd, bool all)
     uint rw_count= ha_count_rw_all(thd, &ha_info);
     bool rc= false;
 
-#ifndef DBUG_OFF
-    if (rw_count > 1)
-    {
-      /*
-        There must be no binlog_hton used in a transaction consisting of more
-        than 1 engine, *when* (at this point) this transaction has not been
-        binlogged. The one exception is if there is an engine without a
-        prepare method, as in this case the engine doesn't support XA and
-        we have to ignore this check.
-      */
-      bool binlog= false, exist_hton_without_prepare= false;
-      for (ha_info= thd->transaction->all.ha_list; ha_info;
-           ha_info= ha_info->next())
-      {
-        if (ha_info->ht() == binlog_hton)
-          binlog= true;
-        if (!ha_info->ht()->prepare)
-          exist_hton_without_prepare= true;
-      }
-      DBUG_ASSERT(!binlog || exist_hton_without_prepare);
-    }
-#endif
+    /*
+      This transaction has not been binlogged as indicated by need_unlog.
+      Such exceptional cases include transactions with no effect to engines,
+      e.g REPLACE that does not change the dat but still the Engine
+      transaction branch claims to be rw, and few more.
+      In all such cases an empty XA-prepare group of events is bin-logged.
+    */
     if (rw_count > 0)
     {
       /* an empty XA-prepare event group is logged */