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Code Activity

MDEV-27962 Instant DDL downgrades the MDL when table is empty

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- Server incorrectly downgrading the MDL after prepare phase when
table is empty. mdl_exclusive_after_prepare is being set in
prepare phase only. But mdl_exclusive_after_prepare condition was
misplaced and checked before prepare phase by
commit d270525dfd and it is now
changed to check after prepare phase.

 - main.innodb_mysql_sync test case was changed to avoid locking
optimization when table is empty.
This commit is contained in:
Thirunarayanan Balathandayuthapani
2022-03-01 13:01:48 +05:30
parent 3c58cdd91d
commit 446ec64651
5 changed files with 54 additions and 17 deletions
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12
mysql-test/main/innodb_mysql_sync.result
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@ -131,6 +131,7 @@ connection default;
DROP DATABASE db1;
# Test 2: Primary index (implicit), should block writes.
CREATE TABLE t1(a INT NOT NULL, b INT NOT NULL) engine=innodb;
INSERT INTO t1 VALUES(1, 2);
SET DEBUG_SYNC= "alter_table_inplace_after_lock_downgrade SIGNAL manage WAIT_FOR query";
# Sending:
ALTER TABLE t1 ADD UNIQUE INDEX(a), LOCK=SHARED;
@ -139,15 +140,16 @@ SET DEBUG_SYNC= "now WAIT_FOR manage";
USE test;
SELECT * FROM t1;
a b
1 2
# Sending:
UPDATE t1 SET a=NULL;
UPDATE t1 SET a=3;
connection con2;
# Waiting for SELECT to be blocked by the metadata lock on t1
SET DEBUG_SYNC= "now SIGNAL query";
connection default;
# Reaping: ALTER TABLE t1 ADD UNIQUE INDEX(a)
connection con1;
# Reaping: UPDATE t1 SET a=NULL
# Reaping: UPDATE t1 SET a=3
# Test 3: Primary index (explicit), should block writes.
connection default;
ALTER TABLE t1 DROP INDEX a;
@ -158,15 +160,16 @@ connection con1;
SET DEBUG_SYNC= "now WAIT_FOR manage";
SELECT * FROM t1;
a b
3 2
# Sending:
UPDATE t1 SET a=NULL;
UPDATE t1 SET a=4;
connection con2;
# Waiting for SELECT to be blocked by the metadata lock on t1
SET DEBUG_SYNC= "now SIGNAL query";
connection default;
# Reaping: ALTER TABLE t1 ADD PRIMARY KEY (a)
connection con1;
# Reaping: UPDATE t1 SET a=NULL
# Reaping: UPDATE t1 SET a=4
# Test 4: Secondary unique index, should not block reads.
connection default;
SET DEBUG_SYNC= "alter_table_inplace_after_lock_downgrade SIGNAL manage WAIT_FOR query";
@ -176,6 +179,7 @@ connection con1;
SET DEBUG_SYNC= "now WAIT_FOR manage";
SELECT * FROM t1;
a b
4 2
SET DEBUG_SYNC= "now SIGNAL query";
connection default;
# Reaping: ALTER TABLE t1 ADD UNIQUE (b)