flush status;
set query_cache_type=DEMAND;
set global query_cache_size= 1024*768;
drop table if exists t1;
create table t1 (a varchar(100));
insert into t1 values ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
Activate debug hook and attempt to retrieve the statement from the cache.
set session debug='+d,wait_in_query_cache_insert';
select SQL_CACHE * from t1;;
On a second connection; clear the query cache.
show status like 'Qcache_queries_in_cache';
Variable_name	Value
Qcache_queries_in_cache	1
set global query_cache_size= 0;
Signal the debug hook to release the lock.
select id from information_schema.processlist where state='wait_in_query_cache_insert' into @thread_id;
kill query @thread_id;
Show query cache status.
show status like 'Qcache_queries_in_cache';
Variable_name	Value
Qcache_queries_in_cache	0
set global query_cache_size= 0;
use test;
drop table t1;