The MTR based test innodb_defrag_concurrent is not repeatable.

Logging: ./mtr  --mem --repeat=2 innodb_defrag_concurrent

..

=================================================

TEST                                      RESULT   TIME (ms) or COMMENT

--------------------------------------------------------------------------

worker[1] Using MTR_BUILD_THREAD 300, with reserved ports 16000..16019

innodb.innodb_defrag_concurrent 'innodb' [ pass ]  29589

innodb.innodb_defrag_concurrent 'innodb' [ 2 fail ]

        Test ended at 2022-05-13 12:39:55

CURRENT_TEST: innodb.innodb_defrag_concurrent

--- /Server_bin/10.8_asan/mysql-test/suite/innodb/r/innodb_defrag_concurrent.result     2022-03-01 17:39:21.000000000 +0100

+++ /Server_bin/10.8_asan/mysql-test/suite/innodb/r/innodb_defrag_concurrent.reject     2022-05-13 12:39:54.905656077 +0200

@@ -46,7 +46,7 @@

 15800

 select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and  stat_name  in ('n_pages_freed');

 count(stat_value) > 0

-0

+1

 select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and  stat_name  in ('n_page_split');

 count(stat_value) > 0

 1

mysqltest: Result content mismatch

The reason for that is the following:

The creation of the table t1 leads to records like

select database_name, table_name, index_name, stat_name, stat_value, sample_size

from mysql.innodb_index_stats where table_name like '%t1%' and  stat_name  in ('n_page_split');

database_name	table_name	index_name	stat_name	stat_value	sample_size	

test	t1	PRIMARY	n_page_split	#	NULL	

test	t1	second	n_page_split	#	NULL

After some OPTIMIZE t1 we get some additional record

test	t1	FTS_DOC_ID_INDEX	n_page_split  #	NULL

And these records do not disappear if the table t1 gets dropped.

IMHO this is rather harmless as long as parts of the server

- do not use these values at all

or

- are aware that whatever statistics which is older than the create

  data of a table mentioned is no more valid.

The repetition of innodb_defrag_concurrent meets at its begin this

historic data of the previous execution and fails with result set difference.