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MDEV-14589 InnoDB should not lock a delete-marked record

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When the transaction isolation level is SERIALIZABLE, or when
a locking read is performed in the REPEATABLE READ isolation level,
InnoDB must lock delete-marked records in order to prevent another
transaction from inserting something.

However, at READ UNCOMMITTED or READ COMMITTED isolation level or
when the parameter innodb_locks_unsafe_for_binlog is set, the
repeatability of the reads does not matter, and there is no need
to lock any records.

row_search_mvcc(): Skip locks on delete-marked committed records upfront,
instead of invoking row_unlock_for_mysql() afterwards. The unlocking
never worked for secondary index records.
This commit is contained in:
Marko Mäkelä 2017-12-11 14:39:53 +02:00
parent 434c9e6f0e
commit 13b9ec651a
3 changed files with 167 additions and 13 deletions
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57
mysql-test/suite/innodb/r/lock_deleted.result Normal file
View file

@ -0,0 +1,57 @@
connect stop_purge, localhost, root,,;
START TRANSACTION WITH CONSISTENT SNAPSHOT;
connect delete, localhost, root,,;
connection default;
CREATE TABLE t1(a INT PRIMARY KEY, b INT UNIQUE) ENGINE=InnoDB;
INSERT INTO t1 VALUES(1,1);
DELETE FROM t1;
SET DEBUG_SYNC='row_ins_sec_index_unique SIGNAL inserted WAIT_FOR locked';
BEGIN;
INSERT INTO t1 VALUES(1,1);
connection delete;
SET DEBUG_SYNC='now WAIT_FOR inserted';
SET DEBUG_SYNC='innodb_row_search_for_mysql_exit SIGNAL locked';
SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;
BEGIN;
DELETE FROM t1 WHERE b=1;
connection default;
connection delete;
COMMIT;
connection default;
SET DEBUG_SYNC='RESET';
ROLLBACK;
SET DEBUG_SYNC='row_ins_sec_index_unique SIGNAL inserted WAIT_FOR locked';
BEGIN;
INSERT INTO t1 VALUES(1,1);
connection delete;
SET DEBUG_SYNC='now WAIT_FOR inserted';
SET DEBUG_SYNC='innodb_row_search_for_mysql_exit SIGNAL locked';
SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
BEGIN;
DELETE FROM t1 WHERE b=1;
connection default;
connection delete;
COMMIT;
connection default;
SET DEBUG_SYNC='RESET';
ROLLBACK;
SET DEBUG_SYNC='row_ins_sec_index_unique SIGNAL inserted WAIT_FOR locked';
BEGIN;
SET innodb_lock_wait_timeout=1;
INSERT INTO t1 VALUES(1,1);
connection delete;
SET DEBUG_SYNC='now WAIT_FOR inserted';
SET DEBUG_SYNC='innodb_row_search_for_mysql_exit SIGNAL locked';
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
BEGIN;
DELETE FROM t1 WHERE b=1;
connection default;
ERROR HY000: Lock wait timeout exceeded; try restarting transaction
COMMIT;
SET DEBUG_SYNC='RESET';
connection delete;
COMMIT;
disconnect delete;
disconnect stop_purge;
connection default;
DROP TABLE t1;

72
mysql-test/suite/innodb/t/lock_deleted.test Normal file
View file

@ -0,0 +1,72 @@
--source include/have_innodb.inc
--source include/have_debug.inc
--source include/have_debug_sync.inc
--source include/count_sessions.inc
connect(stop_purge, localhost, root,,);
START TRANSACTION WITH CONSISTENT SNAPSHOT;
connect(delete, localhost, root,,);
connection default;
CREATE TABLE t1(a INT PRIMARY KEY, b INT UNIQUE) ENGINE=InnoDB;
INSERT INTO t1 VALUES(1,1);
DELETE FROM t1;
let $i=2;
while ($i) {
let $iso= `SELECT CASE $i WHEN 1 THEN 'UNCOMMITTED' ELSE 'COMMITTED' END`;
SET DEBUG_SYNC='row_ins_sec_index_unique SIGNAL inserted WAIT_FOR locked';
BEGIN;
send INSERT INTO t1 VALUES(1,1);
connection delete;
SET DEBUG_SYNC='now WAIT_FOR inserted';
SET DEBUG_SYNC='innodb_row_search_for_mysql_exit SIGNAL locked';
eval SET SESSION TRANSACTION ISOLATION LEVEL READ $iso;
BEGIN;
send DELETE FROM t1 WHERE b=1;
connection default;
reap;
connection delete;
reap;
COMMIT;
connection default;
SET DEBUG_SYNC='RESET';
ROLLBACK;
dec $i;
}
SET DEBUG_SYNC='row_ins_sec_index_unique SIGNAL inserted WAIT_FOR locked';
BEGIN;
SET innodb_lock_wait_timeout=1;
send INSERT INTO t1 VALUES(1,1);
connection delete;
SET DEBUG_SYNC='now WAIT_FOR inserted';
SET DEBUG_SYNC='innodb_row_search_for_mysql_exit SIGNAL locked';
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
BEGIN;
send DELETE FROM t1 WHERE b=1;
connection default;
--error ER_LOCK_WAIT_TIMEOUT
reap;
COMMIT;
SET DEBUG_SYNC='RESET';
connection delete;
reap;
COMMIT;
disconnect delete;
disconnect stop_purge;
connection default;
DROP TABLE t1;
--source include/wait_until_count_sessions.inc

51
storage/innobase/row/row0sel.cc
View file

@ -4890,9 +4890,44 @@ wrong_offs:
ulint lock_type; ulint lock_type;
if (srv_locks_unsafe_for_binlog
|| trx->isolation_level <= TRX_ISO_READ_COMMITTED) {
/* At READ COMMITTED or READ UNCOMMITTED
isolation levels, do not lock committed
delete-marked records. */
if (!rec_get_deleted_flag(rec, comp)) {
goto no_gap_lock;
}
if (index == clust_index) {
trx_id_t trx_id = row_get_rec_trx_id(
rec, index, offsets);
/* In delete-marked records, DB_TRX_ID must
always refer to an existing undo log record. */
ut_ad(trx_id);
if (!trx_rw_is_active(trx_id, NULL, false)) {
/* The clustered index record
was delete-marked in a committed
transaction. Ignore the record. */
goto locks_ok_del_marked;
}
} else if (trx_t* trx = row_vers_impl_x_locked(
rec, index, offsets)) {
/* The record belongs to an active
transaction. We must acquire a lock. */
trx_release_reference(trx);
} else {
/* The secondary index record does not
point to a delete-marked clustered index
record that belongs to an active transaction.
Ignore the secondary index record, because
it is not locked. */
goto next_rec;
}
goto no_gap_lock;
}
if (!set_also_gap_locks if (!set_also_gap_locks
|| srv_locks_unsafe_for_binlog
|| trx->isolation_level <= TRX_ISO_READ_COMMITTED
|| (unique_search && !rec_get_deleted_flag(rec, comp)) || (unique_search && !rec_get_deleted_flag(rec, comp))
|| dict_index_is_spatial(index)) { || dict_index_is_spatial(index)) {
@ -5096,6 +5131,7 @@ locks_ok:
page_rec_is_comp() cannot be used! */ page_rec_is_comp() cannot be used! */
if (rec_get_deleted_flag(rec, comp)) { if (rec_get_deleted_flag(rec, comp)) {
locks_ok_del_marked:
/* In delete-marked records, DB_TRX_ID must /* In delete-marked records, DB_TRX_ID must
always refer to an existing undo log record. */ always refer to an existing undo log record. */
ut_ad(index != clust_index ut_ad(index != clust_index
@ -5103,17 +5139,6 @@ locks_ok:
/* The record is delete-marked: we can skip it */ /* The record is delete-marked: we can skip it */
if ((srv_locks_unsafe_for_binlog
|| trx->isolation_level <= TRX_ISO_READ_COMMITTED)
&& prebuilt->select_lock_type != LOCK_NONE
&& !did_semi_consistent_read) {
/* No need to keep a lock on a delete-marked record
if we do not want to use next-key locking. */
row_unlock_for_mysql(prebuilt, TRUE);
}
/* This is an optimization to skip setting the next key lock /* This is an optimization to skip setting the next key lock
on the record that follows this delete-marked record. This on the record that follows this delete-marked record. This
optimization works because of the unique search criteria optimization works because of the unique search criteria