SET @transaction_isolation= @@global.transaction_isolation;
SET GLOBAL TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
INSERT INTO cache_policies VALUES("cache_policy", "innodb_only",
"innodb_only", "innodb_only", "innodb_only");
INSERT INTO config_options VALUES("separator", "|");
INSERT INTO containers VALUES ("desc_t1", "test", "t1",
"c1", "c2",  "c3", "c4", "c5", "PRIMARY");
USE test;
connect  con1,localhost,root,,;
DROP TABLE IF EXISTS t1;
CREATE TABLE t1        (c1 VARCHAR(32),
c2 VARCHAR(1024),
c3 INT, c4 BIGINT UNSIGNED, c5 INT, primary key(c1))
ENGINE = INNODB;
INSERT INTO t1 VALUES ('D', 'Darmstadt', 0, 0, 0);
INSTALL PLUGIN daemon_memcached SONAME 'libmemcached.so';
SELECT c1,c2 FROM t1;
c1	c2
D	Darmstadt
SELECT c1,c2 FROM t1;
c1	c2
D	Darmstadt
ALTER TABLE test.t1 ADD COLUMN j JSON;
CREATE PROCEDURE alter_column()
BEGIN
SELECT SLEEP(10);
ALTER TABLE test.t1 ADD COLUMN foo varchar(200) AS (j->'$.foo') VIRTUAL;
END//
connection con1;
set session lock_wait_timeout=1;
call alter_column();;
connection default;
Here are the memcached results with E:
Darmstadt
connection con1;
SLEEP(10)
0
ERROR HY000: Lock wait timeout exceeded; try restarting transaction
connection default;
disconnect con1;
drop procedure alter_column;
DROP TABLE t1;
UNINSTALL PLUGIN daemon_memcached;
DROP DATABASE innodb_memcache;
SET @@global.transaction_isolation= @transaction_isolation;