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8280fdd3c3
Fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock", with after-review fixes. SELECT statements with subqueries referencing InnoDB tables were acquiring shared locks on rows in these tables when they were executed in REPEATABLE-READ mode and with statement or mixed mode binary logging turned on. This was a regression which were introduced when fixing bug 39843. The problem was that for tables belonging to subqueries parser set TL_READ_DEFAULT as a lock type. In cases when statement/mixed binary logging at open_tables() time this type of lock was converted to TL_READ_NO_INSERT lock at open_tables() time and caused InnoDB engine to acquire shared locks on reads from these tables. Although in some cases such behavior was correct (e.g. for subqueries in DELETE) in case of SELECT it has caused unnecessary locking. This patch tries to solve this problem by rethinking our approach to how we handle locking for SELECT and subqueries. Now we always set TL_READ_DEFAULT lock type for all cases when we read data. When at open_tables() time this lock is interpreted as TL_READ_NO_INSERT or TL_READ depending on whether this statement as a whole or call to function which uses particular table should be written to the binary log or not (if yes then statement should be properly serialized with concurrent statements and stronger lock should be acquired). Test coverage is added for both InnoDB and MyISAM. This patch introduces an "incompatible" change in locking scheme for subqueries used in SELECT ... FOR UPDATE and SELECT .. IN SHARE MODE. In 4.1 the server would use a snapshot InnoDB read for subqueries in SELECT FOR UPDATE and SELECT .. IN SHARE MODE statements, regardless of whether the binary log is on or off. If the user required a different type of read (i.e. locking read), he/she could request so explicitly by providing FOR UPDATE/IN SHARE MODE clause for each individual subquery. On of the patches for 5.0 broke this behaviour (which was not documented or tested), and started to use locking reads fora all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
63 lines
1.6 KiB
Text
63 lines
1.6 KiB
Text
-- source include/have_log_bin.inc
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-- source include/have_innodb.inc
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-- source include/not_binlog_format_row.inc
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--echo #
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--echo # Bug #39022: Mysql randomly crashing in lock_sec_rec_cons_read_sees
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--echo #
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CREATE TABLE t1(a TINYINT NOT NULL,b TINYINT,PRIMARY KEY(b)) ENGINE=innodb;
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CREATE TABLE t2(d TINYINT NOT NULL,UNIQUE KEY(d)) ENGINE=innodb;
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INSERT INTO t1 VALUES (13,0),(8,1),(9,2),(6,3),
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(11,5),(11,6),(7,7),(7,8),(4,9),(6,10),(3,11),(11,12),
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(12,13),(7,14);
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INSERT INTO t2 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),
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(11),(12),(13),(14);
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connect (thread1, localhost, root,,);
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connect (thread2, localhost, root,,);
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connection thread1;
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--echo # in thread1
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START TRANSACTION;
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connection thread2;
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--echo # in thread2
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REPLACE INTO t2 VALUES (-17);
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SELECT d FROM t2,t1 WHERE d=(SELECT MAX(a) FROM t1 WHERE t1.a > t2.d) LOCK IN SHARE MODE;
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connection thread1;
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--echo # in thread1
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REPLACE INTO t1(a,b) VALUES (67,20);
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connection thread2;
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--echo # in thread2
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COMMIT;
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START TRANSACTION;
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REPLACE INTO t1(a,b) VALUES (65,-50);
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REPLACE INTO t2 VALUES (-91);
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send;
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SELECT d FROM t2,t1 WHERE d=(SELECT MAX(a) FROM t1 WHERE t1.a > t2.d) LOCK IN SHARE MODE; #waits
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connection thread1;
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--echo # in thread1
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--echo # should not crash
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--error ER_LOCK_DEADLOCK
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SELECT d FROM t2,t1 WHERE d=(SELECT MAX(a) FROM t1 WHERE t1.a > t2.d) LOCK IN SHARE MODE; #crashes
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connection thread2;
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--echo # in thread2
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REAP;
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disconnect thread2;
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--source include/wait_until_disconnected.inc
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connection thread1;
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--echo # in thread1;
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disconnect thread1;
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--source include/wait_until_disconnected.inc
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connection default;
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DROP TABLE t1,t2;
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