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MDEV-3917 multiple use locks (GET_LOCK) in one connection.

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The patch contributed by Konstantin Osipov applied.
    Native comments:
      Implement multiple user-level locks per connection.

      GET_LOCK() function in MySQL allows a connection  to hold at most
      one user level lock. Taking a new lock automatically releases the
      old lock, if any.

      The limit of one lock per session existed since  early versions
      of MySQL didn't have a deadlock detector for SQL locks.
      MDL patches in MySQL 5.5 added a deadlock detector,
      so starting from 5.5 it became possible to take multiple locks
      in any order -- a deadlock, should it occur, would be detected
      and an error returned to the client which closed the wait chain.

      This is exactly what is done in this patch: ULLs are moved
      to use MDL subsystem.
This commit is contained in:
Alexey Botchkov
2013-04-12 18:06:51 +05:00
parent ff3407a111
commit 1a600125ff
14 changed files with 869 additions and 353 deletions
Download Patch File Download Diff File Expand all files Collapse all files

221
mysql-test/r/func_misc.result
View File

@@ -338,6 +338,227 @@ set optimizer_switch=@optimizer_switch_save;
drop view v_merge, vm;
drop table t1,tv;
#
# GET_LOCK, RELEASE_LOCK, IS_USED_LOCK functions test
#
# IS_USED_LOCK, IS_FREE_LOCK: the lock is not acquired
# Note: IS_USED_LOCK returns NULL if the lock is unused
select is_used_lock('test');
is_used_lock('test')
NULL
select is_free_lock('test');
is_free_lock('test')
1
# GET_LOCK returns 1 if it manages to acquire a lock
select get_lock('test', 0);
get_lock('test', 0)
1
# IS_USED_LOCK, IS_FREE_LOCK: the lock is acquired
select is_free_lock('test');
is_free_lock('test')
0
select is_used_lock('test') = connection_id();
is_used_lock('test') = connection_id()
1
# -> Switching to connection 'con1'
# IS_USED_LOCK, IS_FREE_LOCK: the lock is acquired in another
# connection
select is_used_lock('test') = connection_id();
is_used_lock('test') = connection_id()
0
select is_free_lock('test');
is_free_lock('test')
0
# GET_LOCK returns 0 if it can't acquire a lock (wait timeout)
select get_lock('test', 0);
get_lock('test', 0)
0
# RELEASE_LOCK returns 0 if the lock belongs to another connection
select release_lock('test');
release_lock('test')
0
# -> Switching to connection 'default'
# RELEASE_LOCK returns 1 if it successfully releases a lock
select release_lock('test');
release_lock('test')
1
# RELEASE_LOCK returns NULL if it doesn't release a lock and there is no such lock
select release_lock('test');
release_lock('test')
NULL
# Test that get_lock() returns NULL if error.
select get_lock('test', 0);
get_lock('test', 0)
1
# -> Switching to connection 'con1'
create table t1 select connection_id() as id;
select get_lock('test', 7200);
# -> Switching to connection 'default'
select (@id := id) - id from t1;
(@id := id) - id
0
kill query @id;
# -> Switching to connection 'con1'
get_lock('test', 7200)
NULL
# -> Switching to connection 'default'
# GET_LOCK() works recursively
select get_lock('test', 0);
get_lock('test', 0)
1
select get_lock('test', 0);
get_lock('test', 0)
1
select get_lock('test', 0);
get_lock('test', 0)
1
# RELEASE_LOCK() needs to be called recursively then, too
select release_lock('test');
release_lock('test')
1
select release_lock('test');
release_lock('test')
1
select release_lock('test');
release_lock('test')
1
# Once the last instance of the lock is released,
# the next call returns NULL
select release_lock('test');
release_lock('test')
1
# Multiple locks in the same session are OK
select get_lock('test1', 0);
get_lock('test1', 0)
1
select get_lock('test2', 0);
get_lock('test2', 0)
1
select get_lock('test3', 0);
get_lock('test3', 0)
1
select release_lock('test1');
release_lock('test1')
1
select release_lock('test2');
release_lock('test2')
1
select release_lock('test3');
release_lock('test3')
1
# Deadlocks are detected e.g. in case of a mutual wait
select get_lock('test1', 0);
get_lock('test1', 0)
1
# -> Switching to connection 'con1'
select get_lock('test2', 0);
get_lock('test2', 0)
1
select get_lock('test1', 7200);
# -> Switching to connection 'default'
select get_lock('test2', 7200);
ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
select release_lock('test1');
release_lock('test1')
1
# -> Switching to connection 'con1'
get_lock('test1', 7200)
1
select release_lock('test2');
release_lock('test2')
1
select release_lock('test1');
release_lock('test1')
1
# -> Switching to connection 'default'
# LOCK/UNLOCK TABLES works fine with a user lock.
lock table t1 write;
select get_lock('test', 0);
get_lock('test', 0)
1
unlock tables;
commit;
select release_lock('test');
release_lock('test')
1
# GLOBAL READ LOCK works with fine with user locks
select get_lock('test1', 0);
get_lock('test1', 0)
1
flush tables with read lock;
select get_lock('test2', 0);
get_lock('test2', 0)
1
unlock tables;
commit;
select release_lock('test1');
release_lock('test1')
1
select release_lock('test2');
release_lock('test2')
1
# BEGIN/COMMIT/ROLLBACK don't unlock user locks.
begin;
select get_lock('test1', 0);
get_lock('test1', 0)
1
select get_lock('test2', 0);
get_lock('test2', 0)
1
select count(*) from t1;
count(*)
1
rollback;
select release_lock('test1');
release_lock('test1')
1
select release_lock('test2');
release_lock('test2')
1
# Deadlocks between user locks and LOCK TABLES locks
# are detected OK.
select get_lock('test', 0);
get_lock('test', 0)
1
# -> Switching to connection 'con1'
lock table t1 write;
select get_lock('test', 7200);
# -> Switching to connection 'default'
lock table t1 read;
ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
select release_lock('test');
release_lock('test')
1
# -> Switching to connection 'con1'
get_lock('test', 7200)
1
select release_lock('test');
release_lock('test')
1
unlock tables;
# cleanup
drop table t1;
# check too long identifier names
select get_lock(repeat('a', 192), 0);
get_lock(repeat('a', 192), 0)
1
select is_used_lock(repeat('a', 192)) = connection_id();
is_used_lock(repeat('a', 192)) = connection_id()
1
select is_free_lock(repeat('a', 192));
is_free_lock(repeat('a', 192))
0
select release_lock(repeat('a', 192));
release_lock(repeat('a', 192))
1
select get_lock(repeat('a', 193), 0);
ERROR 42000: Identifier name 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' is too long
select is_used_lock(repeat('a', 193));
ERROR 42000: Identifier name 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' is too long
select is_free_lock(repeat('a', 193));
ERROR 42000: Identifier name 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' is too long
select release_lock(repeat('a', 193));
ERROR 42000: Identifier name 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' is too long
#
# End of 5.5 tests
#
#