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mariadb/mysql-test/suite/storage_engine/select_high_prio.test
Sergei Golubchik bead24b7f3 mariadb-test: wait on disconnect
Remove one of the major sources of race condiitons in mariadb-test.
Normally, mariadb_close() sends COM_QUIT to the server and immediately
disconnects. In mariadb-test it means the test can switch to another
connection and sends queries to the server before the server even
started parsing the COM_QUIT packet and these queries can see the
connection as fully active, as it didn't reach dispatch_command yet.

This is a major source of instability in tests and many - but not all,
still less than a half - tests employ workarounds. The correct one
is a pair count_sessions.inc/wait_until_count_sessions.inc.
Also very popular was wait_until_disconnected.inc, which was completely
useless, because it verifies that the connection is closed, and after
disconnect it always is, it didn't verify whether the server processed
COM_QUIT. Sadly the placebo was as widely used as the real thing.

Let's fix this by making mariadb-test `disconnect` command _to wait_ for
the server to confirm. This makes almost all workarounds redundant.

In some cases count_sessions.inc/wait_until_count_sessions.inc is still
needed, though, as only `disconnect` command is changed:

 * after external tools, like `exec $MYSQL`
 * after failed `connect` command
 * replication, after `STOP SLAVE`
 * Federated/CONNECT/SPIDER/etc after `DROP TABLE`

and also in some XA tests, because an XA transaction is dissociated from
the THD very late, after the server has closed the client connection.

Collateral cleanups: fix comments, remove some redundant statements:
 * DROP IF EXISTS if nothing is known to exist
 * DROP table/view before DROP DATABASE
 * REVOKE privileges before DROP USER
 etc
2025-07-16 09:14:33 +07:00

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#
# SELECT HIGH_PRIOIRITY
#
--source have_engine.inc
# We will have 3 connections:
# con1 will lock a table in READ mode
# con0 will run UPDATE (and will wait on the lock)
# con2 will start another SELECT
# con1 will then unlock the table
#
# With standard SELECT we should see updated rows in the 2nd result set,
# while with SELECT HIGH_PRIORITY we should still see only old rows in con2 resultset
# (and it shouldn't wait till the table is unlocked and UPDATE is executed).
--connect (con0,localhost,root,,)
SET lock_wait_timeout = 4;
--connect (con1,localhost,root,,)
SET lock_wait_timeout = 4;
--connect (con2,localhost,root,,)
SET lock_wait_timeout = 4;
# Part 1: Standard SELECT
# should be executed after the UPDATE
--source create_table.inc
INSERT INTO t1 (a,b) VALUES (1,'f'),(2,'b');
--connection con1
LOCK TABLE t1 READ;
--connection con0
--send
UPDATE t1 SET b = CONCAT(b,b);
--connection con2
let $show_statement = SHOW PROCESSLIST;
let $field = State;
let $condition = LIKE 'Waiting for table%';
let $wait_timeout = 2;
--source include/wait_show_condition.inc
--send
SELECT a,b FROM t1;
--connection con1
let $show_statement = SHOW PROCESSLIST;
let $field = Info;
let $condition = = 'SELECT a,b FROM t1';
let $wait_timeout = 2;
--source include/wait_show_condition.inc
if (!$found)
{
--let $mysql_errname = timeout in wait_show_condition.inc
--let $functionality = Table locking or UPDATE
--source unexpected_result.inc
}
UNLOCK TABLES;
--connection con0
--reap
if ($mysql_errname)
{
--let $my_last_stmt = UPDATE t1 SET b = CONCAT(b,b)
--let $functionality = UPDATE
--source unexpected_result.inc
}
--connection con2
--echo # Should return the new data
--sorted_result
--reap
DROP TABLE t1;
# Part 2: SELECT HIGH_PRIORITY
# should be executed before the UPDATE
--source create_table.inc
INSERT INTO t1 (a,b) VALUES (1,'f'),(2,'b');
--connection con1
LOCK TABLE t1 READ;
--connection con0
--send
UPDATE t1 SET b = CONCAT(b,b,b);
--connection con2
let $condition = LIKE 'Waiting for table%';
let $field = State;
let $wait_timeout = 2;
--source include/wait_show_condition.inc
SET lock_wait_timeout = 1;
--echo # Should return old data
--sorted_result
SELECT HIGH_PRIORITY * FROM t1;
if ($mysql_errname)
{
--let $functionality = SELECT HIGH_PRIORITY
--source unexpected_result.inc
}
--connection con1
UNLOCK TABLES;
--connection con0
--reap
if ($mysql_errname)
{
--let $my_last_stmt = UPDATE t1 SET b = CONCAT(b,b,b)
--let $functionality = UPDATE
--source unexpected_result.inc
}
--disconnect con1
--disconnect con2
--disconnect con0
let $wait_timeout = 30;
--connection default
# Cleanup
DROP TABLE t1;
--source cleanup_engine.inc