[#MDEV-21226] open_tables count is increasing with >=mariadb:10.1.36 to 10.4.10

Comment by Elena Stepanova [ 2020-01-30 ]

Thanks for the report.

MTR test case which demonstrates the problem is below.
It is for debugging purposes only, do not put it into the regression suite.

--source include/have_innodb.inc

CREATE TABLE t0 (

  `id` int(10) unsigned NOT NULL,

  a int,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB;

--let $num= 500

while ($num)

    --eval CREATE DATABASE db$num

    --eval USE db$num

    CREATE TABLE t (

        x int(10) unsigned NOT NULL,

        CONSTRAINT fk FOREIGN KEY (x) REFERENCES test.t0 (id)

    ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

    --dec $num

--let $num= 32

while ($num)

    --connect (con$num,localhost,root,,)

    --delimiter $

    --send

        LOOP

            UPDATE test.t0 SET a = 1 WHERE id = 1;

        END LOOP$

    --delimiter ;

    --dec $num

--connection default

show variables like 'table_open_cache';

--let $num= 10

while ($num)

    SHOW GLOBAL STATUS LIKE 'open_tables';

    --sleep 1

    --dec $num

10.1.36
show variables like 'table_open_cache';
Variable_name Value
table_open_cache 421
SHOW GLOBAL STATUS LIKE 'open_tables';
Variable_name Value
Open_tables 5868
SHOW GLOBAL STATUS LIKE 'open_tables';
Variable_name Value
Open_tables 7899
SHOW GLOBAL STATUS LIKE 'open_tables';
Variable_name Value
Open_tables 7442
SHOW GLOBAL STATUS LIKE 'open_tables';
Variable_name Value
Open_tables 8460
...

10.1.35
show variables like 'table_open_cache';
Variable_name Value
table_open_cache 421
SHOW GLOBAL STATUS LIKE 'open_tables';
Variable_name Value
Open_tables 52
SHOW GLOBAL STATUS LIKE 'open_tables';
Variable_name Value
Open_tables 54
SHOW GLOBAL STATUS LIKE 'open_tables';
Variable_name Value
Open_tables 54
SHOW GLOBAL STATUS LIKE 'open_tables';
Variable_name Value
Open_tables 54
...

Comment by Sergei Golubchik [ 2020-04-23 ]

Please, see ~~MDEV-22180~~ and the discussion therein

[MDEV-21226] open_tables count is increasing with >=mariadb:10.1.36 to 10.4.10 Created: 2019-12-05 Updated: 2020-04-23 Resolved: 2020-04-23
Status:	Closed
Project:	MariaDB Server
Component/s:	Server
Affects Version/s:	10.1.36, 10.4.10, 10.2, 10.3
Fix Version/s:	N/A