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;
SET @old_concurrent_insert= @@GLOBAL.concurrent_insert;
SET @old_query_cache_size= @@GLOBAL.query_cache_size;
DROP TABLE IF EXISTS t1, t2;
CREATE TABLE t1 (a INT);
CREATE TABLE t2 (a INT);
INSERT INTO t1 VALUES (1),(2),(3);
SET GLOBAL concurrent_insert= 1;
SET GLOBAL query_cache_size= 1024*512;
SET GLOBAL query_cache_type= ON;
# Switch to connection con1
SET SESSION debug='+d,wait_after_query_cache_invalidate';
# Send concurrent insert, will wait in the query cache table invalidate
INSERT INTO t1 VALUES (4);
# Switch to connection default
# Wait for concurrent insert to reach the debug point
# Switch to connection con2
# Send SELECT that shouldn't be cached
SELECT * FROM t1;
a
1
2
3
# Switch to connection default
# Notify the concurrent insert to proceed
SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST
WHERE STATE = 'wait_after_query_cache_invalidate' INTO @thread_id;
KILL QUERY @thread_id;
# Switch to connection con1
# Gather insert result
SHOW STATUS LIKE "Qcache_queries_in_cache";
Variable_name	Value
Qcache_queries_in_cache	0
# Test that it's cacheable
SELECT * FROM t1;
a
1
2
3
4
SHOW STATUS LIKE "Qcache_queries_in_cache";
Variable_name	Value
Qcache_queries_in_cache	1
# Disconnect
# Restore defaults
RESET QUERY CACHE;
DROP TABLE t1,t2;
SET GLOBAL concurrent_insert= DEFAULT;
SET GLOBAL query_cache_size= DEFAULT;
SET GLOBAL query_cache_type= DEFAULT;
#
# Bug43758 Query cache can lock up threads in 'freeing items' state
#
FLUSH STATUS;
SET GLOBAL query_cache_type=DEMAND;
SET GLOBAL query_cache_size= 1024*768;
DROP TABLE IF EXISTS t1,t2,t3,t4,t5;
CREATE TABLE t1 (a VARCHAR(100));
CREATE TABLE t2 (a VARCHAR(100));
CREATE TABLE t3 (a VARCHAR(100));
CREATE TABLE t4 (a VARCHAR(100));
CREATE TABLE t5 (a VARCHAR(100));
INSERT INTO t1 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
INSERT INTO t2 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
INSERT INTO t3 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
INSERT INTO t4 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
INSERT INTO t5 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
=================================== Connection thd1
**
** Load Query Cache with a result set and one table.
**
SELECT SQL_CACHE * FROM t1;
a
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
*************************************************************************
** We want to accomplish the following state:
**  - Query cache status: TABLE_FLUSH_IN_PROGRESS
**  - THD1: invalidate_table_internal (iterating query blocks)
**  - THD2: query_cache_insert (cond_wait)
**  - THD3: query_cache_insert (cond_wait)
**  - No thread should be holding the structure_guard_mutex.
**
** First step is to place a DELETE-statement on the debug hook just
** before the mutex lock in invalidate_table_internal.
** This will allow new result sets to be written into the QC.
** 
SET SESSION debug='+d,wait_in_query_cache_invalidate1';
SET SESSION debug='+d,wait_in_query_cache_invalidate2';
DELETE FROM t1 WHERE a like '%a%';;
=================================== Connection default
** Assert that the expect process status is obtained.
**
=================================== Connection thd2
** On THD2: Insert a result into the cache. This attempt will be blocked
** because of a debug hook placed just before the mutex lock after which
** the first part of the result set is written.
SET SESSION debug='+d,wait_in_query_cache_insert';
SELECT SQL_CACHE * FROM t2 UNION SELECT * FROM t3;
=================================== Connection thd3
** On THD3: Insert another result into the cache and block on the same
** debug hook.
SET SESSION debug='+d,wait_in_query_cache_insert';
SELECT SQL_CACHE * FROM t4 UNION SELECT * FROM t5;;
=================================== Connection default
** Assert that the two SELECT-stmt threads to reach the hook.
**
**
** Signal the DELETE thread, THD1, to continue. It will enter the mutex
** lock and set query cache status to TABLE_FLUSH_IN_PROGRESS and then
** unlock the mutex before stopping on the next debug hook.
SELECT SQL_NO_CACHE id FROM information_schema.processlist WHERE state='wait_in_query_cache_invalidate1' LIMIT 1 INTO @flush_thread_id;
KILL QUERY @flush_thread_id;
** Assert that we reach the next debug hook.
**
** Signal the remaining debug hooks blocking THD2 and THD3.
** The threads will grab the guard mutex enter the wait condition and
** and finally release the mutex. The threads will continue to wait
** until a broadcast signal reaches them causing both threads to 
** come alive and check the condition.
SELECT SQL_NO_CACHE id FROM information_schema.processlist WHERE state='wait_in_query_cache_insert' ORDER BY id ASC LIMIT 1 INTO @thread_id;
KILL QUERY @thread_id;
SELECT SQL_NO_CACHE id FROM information_schema.processlist WHERE state='wait_in_query_cache_insert' ORDER BY id DESC LIMIT 1 INTO @thread_id;
KILL QUERY @thread_id;
**
** Finally signal the DELETE statement on THD1 one last time.
** The stmt will complete the query cache invalidation and return 
** cache status to NO_FLUSH_IN_PROGRESS. On the status change
** One signal will be sent to the thread group waiting for executing
** invalidations and a broadcast signal will be sent to the thread 
** group holding result set writers.
SELECT SQL_NO_CACHE id FROM information_schema.processlist WHERE state='wait_in_query_cache_invalidate2' LIMIT 1 INTO @flush_thread_id;
KILL QUERY @flush_thread_id;
**
*************************************************************************
** No tables should be locked
=================================== Connection thd2
a
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
DELETE FROM t1;
DELETE FROM t2;
DELETE FROM t3;
=================================== Connection thd3
a
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
DELETE FROM t4;
DELETE FROM t5;
=================================== Connection thd1
** Done.
SET GLOBAL query_cache_size= 0;
# Restore defaults
RESET QUERY CACHE;
FLUSH STATUS;
DROP TABLE t1,t2,t3,t4,t5;
SET GLOBAL query_cache_size= DEFAULT;
SET GLOBAL query_cache_type= DEFAULT;