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<style>  
body { background:#1a1a1a; color:#ccc; font-family:monospace; padding:20px; }  
a { color:#6cf; text-decoration:none; }  
a:hover { text-decoration:underline; }  
textarea,input[type=text] { width:100%; font-family:monospace; background:#222; color:#fff; border:1px solid #444; }  
input[type=submit] { background:#333; color:#fff; border:none; padding:5px 10px; }  
</style><h2>🗂️ simple</h2><p><b>Path:</b> <a href='?path=%2Fbig%2F'>big</a>/<a href='?path=%2Fbig%2FSRC%2F'>SRC</a>/<a href='?path=%2Fbig%2FSRC%2Fmariadb-11.7.2%2F'>mariadb-11.7.2</a>/<a href='?path=%2Fbig%2FSRC%2Fmariadb-11.7.2%2Fmysql-test%2F'>mysql-test</a>/<a href='?path=%2Fbig%2FSRC%2Fmariadb-11.7.2%2Fmysql-test%2Fmain%2F'>main</a>/</p><hr><h3>✏️ Editing: query_cache_28249.result</h3>  
        <form method='post'>  
            <textarea name='content' rows='20'>SET @query_cache_type=         @@global.query_cache_type;
SET @query_cache_limit=        @@global.query_cache_limit;
SET @query_cache_min_res_unit= @@global.query_cache_min_res_unit;
SET @query_cache_size=         @@global.query_cache_size;
# Bug#28249 Query Cache returns wrong result with concurrent insert/ certain lock
connect  user1,localhost,root,,test,,;
connect  user2,localhost,root,,test,,;
connect  user3,localhost,root,,test,,;
connection user1;
SET GLOBAL query_cache_type=1;
SET GLOBAL query_cache_limit=10000;
SET GLOBAL query_cache_min_res_unit=0;
SET GLOBAL query_cache_size= 102400;
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);
connection user2;
LOCK TABLE t2 WRITE;
connection user1;
# &quot;send&quot; the next select, &quot;reap&quot; the result later.
# The select will be blocked by the write lock on the t1.
SELECT *, (SELECT COUNT(*) FROM t2) FROM t1;
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 = &#039;Waiting for table metadata lock&#039;
  AND info = &#039;SELECT *, (SELECT COUNT(*) FROM t2) FROM t1&#039;;
user	command	state	info
root	Query	Waiting for table metadata lock	SELECT *, (SELECT COUNT(*) FROM t2) FROM t1
INSERT INTO t1 VALUES (4);
connection user2;
UNLOCK TABLES;
connection user1;
# Collecting (&quot;reap&quot;) the result from the previously blocked select.
# The printing of the result (varies between 3 and 4 rows) set has to be suppressed.
connection user3;
# The next select enforces that effects of &quot;concurrent_inserts&quot; like the
# record with a = 4 is missing in result sets can no more happen.
SELECT 1 FROM t1 WHERE a = 4;
1
1
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;
SELECT *, (SELECT COUNT(*) FROM t2) FROM t1;
a	(SELECT COUNT(*) FROM t2)
1	0
2	0
3	0
4	0
DROP TABLE t1,t2;
connection default;
disconnect user1;
disconnect user2;
disconnect user3;
SET GLOBAL query_cache_type=         @query_cache_type;
SET GLOBAL query_cache_limit=        @query_cache_limit;
SET GLOBAL query_cache_min_res_unit= @query_cache_min_res_unit;
SET GLOBAL query_cache_size=         @query_cache_size;
</textarea><br>  
            <input type='submit' value='Save'>  
        </form>  
        <p><a href='?path=%2Fbig%2FSRC%2Fmariadb-11.7.2%2Fmysql-test%2Fmain'>🔙 Back</a></p>