| Server IP : 185.86.78.101 / Your IP : 216.73.216.213 Web Server : Apache System : Linux 675867-vds-valikoshka1996.gmhost.pp.ua 5.4.0-150-generic #167-Ubuntu SMP Mon May 15 17:35:05 UTC 2023 x86_64 User : www ( 1000) PHP Version : 7.4.33 Disable Function : passthru,exec,system,putenv,chroot,chgrp,chown,shell_exec,popen,proc_open,pcntl_exec,ini_alter,ini_restore,dl,openlog,syslog,readlink,symlink,popepassthru,pcntl_alarm,pcntl_fork,pcntl_waitpid,pcntl_wait,pcntl_wifexited,pcntl_wifstopped,pcntl_wifsignaled,pcntl_wifcontinued,pcntl_wexitstatus,pcntl_wtermsig,pcntl_wstopsig,pcntl_signal,pcntl_signal_dispatch,pcntl_get_last_error,pcntl_strerror,pcntl_sigprocmask,pcntl_sigwaitinfo,pcntl_sigtimedwait,pcntl_exec,pcntl_getpriority,pcntl_setpriority,imap_open,apache_setenv MySQL : OFF | cURL : ON | WGET : ON | Perl : ON | Python : OFF | Sudo : ON | Pkexec : OFF Directory : /www/server/mysql/mysql-test/r/ |
Upload File : |
SET @query_cache_type= @@global.query_cache_type;
Warnings:
Warning 1287 '@@query_cache_type' is deprecated and will be removed in a future release.
SET @query_cache_limit= @@global.query_cache_limit;
Warnings:
Warning 1287 '@@query_cache_limit' is deprecated and will be removed in a future release.
SET @query_cache_min_res_unit= @@global.query_cache_min_res_unit;
Warnings:
Warning 1287 '@@query_cache_min_res_unit' is deprecated and will be removed in a future release.
SET @query_cache_size= @@global.query_cache_size;
Warnings:
Warning 1287 '@@query_cache_size' is deprecated and will be removed in a future release.
# Bug#28249 Query Cache returns wrong result with concurrent insert/ certain lock
# Establish connections user1,user2,user3 (user=root)
# Switch to connection user1
SET GLOBAL query_cache_type=1;
Warnings:
Warning 1287 '@@query_cache_type' is deprecated and will be removed in a future release.
SET GLOBAL query_cache_limit=10000;
Warnings:
Warning 1287 '@@query_cache_limit' is deprecated and will be removed in a future release.
SET GLOBAL query_cache_min_res_unit=0;
Warnings:
Warning 1287 '@@query_cache_min_res_unit' is deprecated and will be removed in a future release.
SET GLOBAL query_cache_size= 102400;
Warnings:
Warning 1287 '@@query_cache_size' is deprecated and will be removed in a future release.
FLUSH TABLES;
DROP TABLE IF EXISTS t1, t2;
CREATE TABLE t1 (a INT);
CREATE TABLE t2 (a INT);
INSERT INTO t1 VALUES (1),(2),(3);
# Switch to connection user2
LOCK TABLE t2 WRITE;
# Switch to connection user1
# "send" the next select, "reap" the result later.
# The select will be blocked by the write lock on the t1.
SELECT *, (SELECT COUNT(*) FROM t2) FROM t1;
# Switch to connection user3
# Poll till the select of connection user1 is blocked by the write lock on t1.
SELECT user,command,state,info FROM information_schema.processlist
WHERE state = 'Waiting for table metadata lock'
AND info = 'SELECT *, (SELECT COUNT(*) FROM t2) FROM t1';
user command state info
root Query Waiting for table metadata lock SELECT *, (SELECT COUNT(*) FROM t2) FROM t1
INSERT INTO t1 VALUES (4);
# Switch to connection user2
UNLOCK TABLES;
# Switch to connection user1
# Collecting ("reap") the result from the previously blocked select.
# The printing of the result (varies between 3 and 4 rows) set has to be suppressed.
# Switch to connection user3
# The next select enforces that effects of "concurrent_inserts" like the
# record with a = 4 is missing in result sets can no more happen.
SELECT 1 FROM t1 WHERE a = 4;
1
1
# Switch to connection user1
# The next result set must contain 4 rows.
SELECT *, (SELECT COUNT(*) FROM t2) FROM t1;
a (SELECT COUNT(*) FROM t2)
1 0
2 0
3 0
4 0
RESET QUERY CACHE;
Warnings:
Warning 1681 'RESET QUERY CACHE' is deprecated and will be removed in a future release.
SELECT *, (SELECT COUNT(*) FROM t2) FROM t1;
a (SELECT COUNT(*) FROM t2)
1 0
2 0
3 0
4 0
DROP TABLE t1,t2;
# Switch to connection default + close connections user1,user2,user3
SET GLOBAL query_cache_type= @query_cache_type;
Warnings:
Warning 1287 '@@query_cache_type' is deprecated and will be removed in a future release.
SET GLOBAL query_cache_limit= @query_cache_limit;
Warnings:
Warning 1287 '@@query_cache_limit' is deprecated and will be removed in a future release.
SET GLOBAL query_cache_min_res_unit= @query_cache_min_res_unit;
Warnings:
Warning 1287 '@@query_cache_min_res_unit' is deprecated and will be removed in a future release.
SET GLOBAL query_cache_size= @query_cache_size;
Warnings:
Warning 1287 '@@query_cache_size' is deprecated and will be removed in a future release.