MDEV-26753 Assertion state == TRX_STATE_PREPARED ||... failed

dict_stats_save(): Do not attempt to commit an already committed
transaction.

Author: dr-m

mysql-test/suite/innodb/r/stat_tables.result

@@ -13,3 +13,17 @@ a
 drop table t1;
 rename table mysql.table_stats_save to mysql.table_stats;
 flush tables;
+#
+# MDEV-26753 Assertion state == TRX_STATE_PREPARED ||... failed
+#
+CREATE TABLE t1(a INT PRIMARY KEY) ENGINE=InnoDB;
+XA START 'test';
+SELECT COUNT(*)>0 FROM mysql.innodb_index_stats LOCK IN SHARE MODE;
+COUNT(*)>0
+1
+INSERT INTO t1 VALUES (1),(2);
+UPDATE mysql.innodb_table_stats SET last_update=NULL WHERE table_name='t1';
+XA END 'test';
+XA ROLLBACK 'test';
+DROP TABLE t1;
+# End of 10.6 tests

mysql-test/suite/innodb/t/stat_tables.test

@@ -15,3 +15,17 @@ select * from t1;
 drop table t1;
 rename table mysql.table_stats_save to mysql.table_stats;
 flush tables;
+
+--echo #
+--echo # MDEV-26753 Assertion state == TRX_STATE_PREPARED ||... failed
+--echo #
+CREATE TABLE t1(a INT PRIMARY KEY) ENGINE=InnoDB;
+XA START 'test';
+SELECT COUNT(*)>0 FROM mysql.innodb_index_stats LOCK IN SHARE MODE;
+INSERT INTO t1 VALUES (1),(2);
+UPDATE mysql.innodb_table_stats SET last_update=NULL WHERE table_name='t1';
+XA END 'test';
+XA ROLLBACK 'test';
+DROP TABLE t1;
+
+--echo # End of 10.6 tests

storage/innobase/dict/dict0stats.cc

@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2009, 2019, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2015, 2021, MariaDB Corporation.
+Copyright (c) 2015, 2022, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -3115,7 +3115,9 @@ dict_stats_save(
 		ret = lock_table_for_trx(index_stats, trx, LOCK_X);
 	}
 	if (ret != DB_SUCCESS) {
-		trx->commit();
+		if (trx->state != TRX_STATE_NOT_STARTED) {
+			trx->commit();
+		}
 		goto unlocked_free_and_exit;
 	}