failed in enter_locked_tables_mode".
Server was aborted due to assertion failure when one tried to
execute statement requiring prelocking (i.e. firing triggers
or using stored functions) while having open HANDLERs.
The problem was that THD::enter_locked_tables_mode() method
which was called at the beginning of execution of prelocked
statement assumed there are no open HANDLERs. It had to do
so because corresponding THD::leave_locked_tables_mode()
method was unable to properly restore MDL sentinel when
leaving LOCK TABLES/prelocked mode in the presence of open
HANDLERs.
This patch solves this problem by changing the latter method
to properly restore MDL sentinel and thus removing need for
this assumption. As a side-effect, it lifts unjustified
limitation by allowing to keep HANDLERs open when entering
LOCK TABLES mode.
Add a wait-for graph based deadlock detector to the
MDL subsystem.
Fixes bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and
bug #37346 "innodb does not detect deadlock between update and
alter table".
The first bug manifested itself as an unwarranted abort of a
transaction with ER_LOCK_DEADLOCK error by a concurrent ALTER
statement, when this transaction tried to repeat use of a
table, which it has already used in a similar fashion before
ALTER started.
The second bug showed up as a deadlock between table-level
locks and InnoDB row locks, which was "detected" only after
innodb_lock_wait_timeout timeout.
A transaction would start using the table and modify a few
rows.
Then ALTER TABLE would come in, and start copying rows
into a temporary table. Eventually it would stumble on
the modified records and get blocked on a row lock.
The first transaction would try to do more updates, and get
blocked on thr_lock.c lock.
This situation of circular wait would only get resolved
by a timeout.
Both these bugs stemmed from inadequate solutions to the
problem of deadlocks occurring between different
locking subsystems.
In the first case we tried to avoid deadlocks between metadata
locking and table-level locking subsystems, when upgrading shared
metadata lock to exclusive one.
Transactions holding the shared lock on the table and waiting for
some table-level lock used to be aborted too aggressively.
We also allowed ALTER TABLE to start in presence of transactions
that modify the subject table. ALTER TABLE acquires
TL_WRITE_ALLOW_READ lock at start, and that block all writes
against the table (naturally, we don't want any writes to be lost
when switching the old and the new table). TL_WRITE_ALLOW_READ
lock, in turn, would block the started transaction on thr_lock.c
lock, should they do more updates. This, again, lead to the need
to abort such transactions.
The second bug occurred simply because we didn't have any
mechanism to detect deadlocks between the table-level locks
in thr_lock.c and row-level locks in InnoDB, other than
innodb_lock_wait_timeout.
This patch solves both these problems by moving lock conflicts
which are causing these deadlocks into the metadata locking
subsystem, thus making it possible to avoid or detect such
deadlocks inside MDL.
To do this we introduce new type-of-operation-aware metadata
locks, which allow MDL subsystem to know not only the fact that
transaction has used or is going to use some object but also what
kind of operation it has carried out or going to carry out on the
object.
This, along with the addition of a special kind of upgradable
metadata lock, allows ALTER TABLE to wait until all
transactions which has updated the table to go away.
This solves the second issue.
Another special type of upgradable metadata lock is acquired
by LOCK TABLE WRITE. This second lock type allows to solve the
first issue, since abortion of table-level locks in event of
DDL under LOCK TABLES becomes also unnecessary.
Below follows the list of incompatible changes introduced by
this patch:
- From now on, ALTER TABLE and CREATE/DROP TRIGGER SQL (i.e. those
statements that acquire TL_WRITE_ALLOW_READ lock)
wait for all transactions which has *updated* the table to
complete.
- From now on, LOCK TABLES ... WRITE, REPAIR/OPTIMIZE TABLE
(i.e. all statements which acquire TL_WRITE table-level lock) wait
for all transaction which *updated or read* from the table
to complete.
As a consequence, innodb_table_locks=0 option no longer applies
to LOCK TABLES ... WRITE.
- DROP DATABASE, DROP TABLE, RENAME TABLE no longer abort
statements or transactions which use tables being dropped or
renamed, and instead wait for these transactions to complete.
- Since LOCK TABLES WRITE now takes a special metadata lock,
not compatible with with reads or writes against the subject table
and transaction-wide, thr_lock.c deadlock avoidance algorithm
that used to ensure absence of deadlocks between LOCK TABLES
WRITE and other statements is no longer sufficient, even for
MyISAM. The wait-for graph based deadlock detector of MDL
subsystem may sometimes be necessary and is involved. This may
lead to ER_LOCK_DEADLOCK error produced for multi-statement
transactions even if these only use MyISAM:
session 1: session 2:
begin;
update t1 ... lock table t2 write, t1 write;
-- gets a lock on t2, blocks on t1
update t2 ...
(ER_LOCK_DEADLOCK)
- Finally, support of LOW_PRIORITY option for LOCK TABLES ... WRITE
was abandoned.
LOCK TABLE ... LOW_PRIORITY WRITE from now on has the same
priority as the usual LOCK TABLE ... WRITE.
SELECT HIGH PRIORITY no longer trumps LOCK TABLE ... WRITE in
the wait queue.
- We do not take upgradable metadata locks on implicitly
locked tables. So if one has, say, a view v1 that uses
table t1, and issues:
LOCK TABLE v1 WRITE;
FLUSH TABLE t1; -- (or just 'FLUSH TABLES'),
an error is produced.
In order to be able to perform DDL on a table under LOCK TABLES,
the table must be locked explicitly in the LOCK TABLES list.
condition variable per context instead of one mutex and one conditional
variable for the whole subsystem.
This should increase concurrency in this subsystem.
It also opens the way for further changes which are necessary to solve
such bugs as bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock"
and bug #37346 "innodb does not detect deadlock between update and alter
table".
Two other notable changes done by this patch:
- MDL subsystem no longer implicitly acquires global intention exclusive
metadata lock when per-object metadata lock is acquired. Now this has
to be done by explicit calls outside of MDL subsystem.
- Instead of using separate MDL_context for opening system tables/tables
for purposes of I_S we now create MDL savepoint in the main context
before opening tables and rollback to this savepoint after closing
them. This means that it is now possible to get ER_LOCK_DEADLOCK error
even not inside a transaction. This might happen in unlikely case when
one runs DDL on one of system tables while also running DDL on some
other tables. Cases when this ER_LOCK_DEADLOCK error is not justified
will be addressed by advanced deadlock detector for MDL subsystem which
we plan to implement.
Conflicts:
Text conflict in .bzr-mysql/default.conf
Text conflict in mysql-test/extra/rpl_tests/rpl_loaddata.test
Text conflict in mysql-test/r/mysqlbinlog2.result
Text conflict in mysql-test/suite/binlog/r/binlog_stm_mix_innodb_myisam.result
Text conflict in mysql-test/suite/binlog/r/binlog_unsafe.result
Text conflict in mysql-test/suite/rpl/r/rpl_insert_id.result
Text conflict in mysql-test/suite/rpl/r/rpl_loaddata.result
Text conflict in mysql-test/suite/rpl/r/rpl_stm_auto_increment_bug33029.result
Text conflict in mysql-test/suite/rpl/r/rpl_udf.result
Text conflict in mysql-test/suite/rpl/t/rpl_slow_query_log.test
Text conflict in sql/field.h
Text conflict in sql/log.cc
Text conflict in sql/log_event.cc
Text conflict in sql/log_event_old.cc
Text conflict in sql/mysql_priv.h
Text conflict in sql/share/errmsg.txt
Text conflict in sql/sp.cc
Text conflict in sql/sql_acl.cc
Text conflict in sql/sql_base.cc
Text conflict in sql/sql_class.h
Text conflict in sql/sql_db.cc
Text conflict in sql/sql_delete.cc
Text conflict in sql/sql_insert.cc
Text conflict in sql/sql_lex.cc
Text conflict in sql/sql_lex.h
Text conflict in sql/sql_load.cc
Text conflict in sql/sql_table.cc
Text conflict in sql/sql_update.cc
Text conflict in sql/sql_view.cc
Conflict adding files to storage/innobase. Created directory.
Conflict because storage/innobase is not versioned, but has versioned children. Versioned directory.
Conflict adding file storage/innobase. Moved existing file to storage/innobase.moved.
Conflict adding files to storage/innobase/handler. Created directory.
Conflict because storage/innobase/handler is not versioned, but has versioned children. Versioned directory.
Contents conflict in storage/innobase/handler/ha_innodb.cc
"HANDLER statements within a transaction might lead to deadlocks".
Introduce a notion of a sentinel to MDL_context. A sentinel
is a ticket that separates all tickets in the context into two
groups: before and after it. Currently we can have (and need) only
one designated sentinel -- it separates all locks taken by LOCK
TABLE or HANDLER statement, which must survive COMMIT and ROLLBACK
and all other locks, which must be released at COMMIT or ROLLBACK.
The tricky part is maintaining the sentinel up to date when
someone release its corresponding ticket. This can happen, e.g.
if someone issues DROP TABLE under LOCK TABLES (generally,
see all calls to release_all_locks_for_name()).
MDL_context::release_ticket() is modified to take care of it.
******
A fix and a test case for Bug#46224 "HANDLER statements within a
transaction might lead to deadlocks".
An attempt to mix HANDLER SQL statements, which are transaction-
agnostic, an open multi-statement transaction,
and DDL against the involved tables (in a concurrent connection)
could lead to a deadlock. The deadlock would occur when
HANDLER OPEN or HANDLER READ would have to wait on a conflicting
metadata lock. If the connection that issued HANDLER statement
also had other metadata locks (say, acquired in scope of a
transaction), a classical deadlock situation of mutual wait
could occur.
Incompatible change: entering LOCK TABLES mode automatically
closes all open HANDLERs in the current connection.
Incompatible change: previously an attempt to wait on a lock
in a connection that has an open HANDLER statement could wait
indefinitely/deadlock. After this patch, an error ER_LOCK_DEADLOCK
is produced.
The idea of the fix is to merge thd->handler_mdl_context
with the main mdl_context of the connection, used for transactional
locks. This makes deadlock detection possible, since all waits
with locks are "visible" and available to analysis in a single
MDL context of the connection.
Since HANDLER locks and transactional locks have a different life
cycle -- HANDLERs are explicitly open and closed, and so
are HANDLER locks, explicitly acquired and released, whereas
transactional locks "accumulate" till the end of a transaction
and are released only with COMMIT, ROLLBACK and ROLLBACK TO SAVEPOINT,
a concept of "sentinel" was introduced to MDL_context.
All locks, HANDLER and others, reside in the same linked list.
However, a selected element of the list separates locks with
different life cycle. HANDLER locks always reside at the
end of the list, after the sentinel. Transactional locks are
prepended to the beginning of the list, before the sentinel.
Thus, ROLLBACK, COMMIT or ROLLBACK TO SAVEPOINT, only
release those locks that reside before the sentinel. HANDLER locks
must be released explicitly as part of HANDLER CLOSE statement,
or an implicit close.
The same approach with sentinel
is also employed for LOCK TABLES locks. Since HANDLER and LOCK TABLES
statement has never worked together, the implementation is
made simple and only maintains one sentinel, which is used either
for HANDLER locks, or for LOCK TABLES locks.
Bug#16565 mysqld --help --verbose does not order variablesBug#20413 sql_slave_skip_counter is not shown in show variables
Bug#20415 Output of mysqld --help --verbose is incomplete
Bug#25430 variable not found in SELECT @@global.ft_max_word_len;
Bug#32902 plugin variables don't know their names
Bug#34599 MySQLD Option and Variable Reference need to be consistent in formatting!
Bug#34829 No default value for variable and setting default does not raise error
Bug#34834 ? Is accepted as a valid sql mode
Bug#34878 Few variables have default value according to documentation but error occurs
Bug#34883 ft_boolean_syntax cant be assigned from user variable to global var.
Bug#37187 `INFORMATION_SCHEMA`.`GLOBAL_VARIABLES`: inconsistent status
Bug#40988 log_output_basic.test succeeded though syntactically false.
Bug#41010 enum-style command-line options are not honoured (maria.maria-recover fails)
Bug#42103 Setting key_buffer_size to a negative value may lead to very large allocations
Bug#44691 Some plugins configured as MYSQL_PLUGIN_MANDATORY in can be disabled
Bug#44797 plugins w/o command-line options have no disabling option in --help
Bug#46314 string system variables don't support expressions
Bug#46470 sys_vars.max_binlog_cache_size_basic_32 is broken
Bug#46586 When using the plugin interface the type "set" for options caused a crash.
Bug#47212 Crash in DBUG_PRINT in mysqltest.cc when trying to print octal number
Bug#48758 mysqltest crashes on sys_vars.collation_server_basic in gcov builds
Bug#49417 some complaints about mysqld --help --verbose output
Bug#49540 DEFAULT value of binlog_format isn't the default value
Bug#49640 ambiguous option '--skip-skip-myisam' (double skip prefix)
Bug#49644 init_connect and \0
Bug#49645 init_slave and multi-byte characters
Bug#49646 mysql --show-warnings crashes when server dies
WL#3771
"Audit Plugin Interface"
Implement new plug-in type - AUDIT
New plug-in: audit_null
simply increments counter for how many times it was called.
Introduce a counter for protection against global read lock on thread level.
The functions for protection against global read lock sometimes need a local
variable to signal when the protection is set, and hence need to be released.
It would be better to control this behaviour via a counter on the THD struct,
telling how many times the protection has been claimed by the current thread.
A side-effect of the fix is that if protection is claimed twice for a thread,
only a simple increment is required for the second claim, instead of a
mutex-protected increment of the global variable protect_against_global_read_lock.
----------------------------------------------------------
revno: 2617.69.20
committer: Konstantin Osipov <kostja@sun.com>
branch nick: 5.4-4284-1-assert
timestamp: Thu 2009-08-13 18:29:55 +0400
message:
WL#4284 "Transactional DDL locking"
A review fix.
Since WL#4284 implementation separated MDL_request and MDL_ticket,
MDL_request becamse a utility object necessary only to get a ticket.
Store it by-value in TABLE_LIST with the intent to merge
MDL_request::key with table_list->table_name and table_list->db
in future.
Change the MDL subsystem to not require MDL_requests to
stay around till close_thread_tables().
Remove the list of requests from the MDL context.
Requests for shared metadata locks acquired in open_tables()
are only used as a list in recover_from_failed_open_table_attempt(),
which calls mdl_context.wait_for_locks() for this list.
To keep such list for recover_from_failed_open_table_attempt(),
introduce a context class (Open_table_context), that collects
all requests.
A lot of minor cleanups and simplications that became possible
with this change.
2617.31.12, 2617.31.15, 2617.31.15, 2617.31.16, 2617.43.1
- initial changeset that introduced the fix for
Bug#989 and follow up fixes for all test suite failures
introduced in the initial changeset.
------------------------------------------------------------
revno: 2617.31.1
committer: Davi Arnaut <Davi.Arnaut@Sun.COM>
branch nick: 4284-6.0
timestamp: Fri 2009-03-06 19:17:00 -0300
message:
Bug#989: If DROP TABLE while there's an active transaction, wrong binlog order
WL#4284: Transactional DDL locking
Currently the MySQL server does not keep metadata locks on
schema objects for the duration of a transaction, thus failing
to guarantee the integrity of the schema objects being used
during the transaction and to protect then from concurrent
DDL operations. This also poses a problem for replication as
a DDL operation might be replicated even thought there are
active transactions using the object being modified.
The solution is to defer the release of metadata locks until
a active transaction is either committed or rolled back. This
prevents other statements from modifying the table for the
entire duration of the transaction. This provides commitment
ordering for guaranteeing serializability across multiple
transactions.
- Incompatible change:
If MySQL's metadata locking system encounters a lock conflict,
the usual schema is to use the try and back-off technique to
avoid deadlocks -- this schema consists in releasing all locks
and trying to acquire them all in one go.
But in a transactional context this algorithm can't be utilized
as its not possible to release locks acquired during the course
of the transaction without breaking the transaction commitments.
To avoid deadlocks in this case, the ER_LOCK_DEADLOCK will be
returned if a lock conflict is encountered during a transaction.
Let's consider an example:
A transaction has two statements that modify table t1, then table
t2, and then commits. The first statement of the transaction will
acquire a shared metadata lock on table t1, and it will be kept
utill COMMIT to ensure serializability.
At the moment when the second statement attempts to acquire a
shared metadata lock on t2, a concurrent ALTER or DROP statement
might have locked t2 exclusively. The prescription of the current
locking protocol is that the acquirer of the shared lock backs off
-- gives up all his current locks and retries. This implies that
the entire multi-statement transaction has to be rolled back.
- Incompatible change:
FLUSH commands such as FLUSH PRIVILEGES and FLUSH TABLES WITH READ
LOCK won't cause locked tables to be implicitly unlocked anymore.
----------------------------------------------------------
revno: 2617.23.20
committer: Konstantin Osipov <kostja@sun.com>
branch nick: mysql-6.0-runtime
timestamp: Wed 2009-03-04 16:31:31 +0300
message:
WL#4284 "Transactional DDL locking"
Review comments: "Objectify" the MDL API.
MDL_request and MDL_context still need manual construction and
destruction, since they are used in environment that is averse
to constructors/destructors.
-----------------------------------------------------------
2497.479.10 Sergei Golubchik 2008-08-27
proc_info_hook, mysys access to thd->proc_info
This patch is necessary for backport of WL#4284 "Transactional
DDL locking".
------------------------------------------------------------
revno: 2630.22.3
committer: Davi Arnaut <Davi.Arnaut@Sun.COM>
branch nick: 4284-6.0
timestamp: Thu 2008-08-07 22:33:43 -0300
message:
WL#4284: Transactional DDL locking
Make transaction management more modular through a new interface.
The overall objective of this change is to provide groundwork
for the design of transactional DDL locking by cleaning up the
transaction high level API to better distinguish operations implicit
and explicit, and single statement transaction from operations on
the normal transaction.
Having a a high-level interface for transaction management provides
a better base for implementing transactional concepts that are not
always tied to storage engines and also makes it easier to interect
with other higher level modules of the server.
------------------------------------------------------------
revno: 2630.4.39
committer: Dmitry Lenev <dlenev@mysql.com>
branch nick: mysql-6.0-3726-w2
timestamp: Thu 2008-06-26 13:08:27 +0400
message:
Fix warnings about passing pointer to not fully-initialized THD
object to constructor of base Open_tables_state classe, which
appeared on Windows and were introduced by one of the patches
implementing WL#3726 "DDL locking for all metadata objects".
----------------------------------------------------------
revno: 2630.10.1
committer: Konstantin Osipov <konstantin@mysql.com>
branch nick: mysql-6.0-lock-tables-tidyup
timestamp: Wed 2008-06-11 15:49:58 +0400
message:
WL#3726, review fixes.
Now that we have metadata locks, we don't need to keep a crippled
TABLE instance in the table cache to indicate that a table is locked.
Remove all code that used this technique. Instead, rely on metadata
locks and use the standard open_table() and close_thread_table()
to manipulate with the table cache tables.
Removes a list of functions that have become unused (see the comment
for sql_base.cc for details).
Under LOCK TABLES, keep a TABLE_LIST instance for each table
that may be temporarily closed. For that, implement an own class for
LOCK TABLES mode, Locked_tables_list.
This is a pre-requisite patch for WL#4144.
This is not exactly a backport: there is no new
online ALTER table in Celosia, so the old alter table
code was changed to work with the new table cache API.
----------------------------------------------------------
revno: 2630.4.26
committer: Konstantin Osipov <konstantin@mysql.com>
branch nick: mysql-6.0-prelocked_mode-to-push
timestamp: Fri 2008-06-06 23:19:04 +0400
message:
WL#3726: work on review comments.
Remove thd->locked_tables. Always store MYSQL_LOCK instances in
thd->lock.
Rename thd->prelocked_mode to thd->locked_tables_mode.
Use thd->locked_tables_mode to determine if we
are under LOCK TABLES. Update the code to not assume that
if thd->lock is set, LOCK TABLES mode is off.
Review comments.
Backport of:
------------------------------------------------------------
revno: 2630.4.1
committer: Dmitry Lenev <dlenev@mysql.com>
branch nick: mysql-6.0-3726-w
timestamp: Fri 2008-05-23 17:54:03 +0400
message:
WL#3726 "DDL locking for all metadata objects".
After review fixes in progress.
------------------------------------------------------------
This is the first patch in series. It transforms the metadata
locking subsystem to use a dedicated module (mdl.h,cc). No
significant changes in the locking protocol.
The import passes the test suite with the exception of
deprecated/removed 6.0 features, and MERGE tables. The latter
are subject to a fix by WL#4144.
Unfortunately, the original changeset comments got lost in a merge,
thus this import has its own (largely insufficient) comments.
This patch fixes Bug#25144 "replication / binlog with view breaks".
Warning: this patch introduces an incompatible change:
Under LOCK TABLES, it's no longer possible to FLUSH a table that
was not locked for WRITE.
Under LOCK TABLES, it's no longer possible to DROP a table or
VIEW that was not locked for WRITE.
******
Backport of:
------------------------------------------------------------
revno: 2630.4.2
committer: Dmitry Lenev <dlenev@mysql.com>
branch nick: mysql-6.0-3726-w
timestamp: Sat 2008-05-24 14:03:45 +0400
message:
WL#3726 "DDL locking for all metadata objects".
After review fixes in progress.
******
Backport of:
------------------------------------------------------------
revno: 2630.4.3
committer: Dmitry Lenev <dlenev@mysql.com>
branch nick: mysql-6.0-3726-w
timestamp: Sat 2008-05-24 14:08:51 +0400
message:
WL#3726 "DDL locking for all metadata objects"
Fixed failing Windows builds by adding mdl.cc to the lists
of files needed to build server/libmysqld on Windows.
******
Backport of:
------------------------------------------------------------
revno: 2630.4.4
committer: Dmitry Lenev <dlenev@mysql.com>
branch nick: mysql-6.0-3726-w
timestamp: Sat 2008-05-24 21:57:58 +0400
message:
WL#3726 "DDL locking for all metadata objects".
Fix for assert failures in kill.test which occured when one
tried to kill ALTER TABLE statement on merge table while it
was waiting in wait_while_table_is_used() for other connections
to close this table.
These assert failures stemmed from the fact that cleanup code
in this case assumed that temporary table representing new
version of table was open with adding to THD::temporary_tables
list while code which were opening this temporary table wasn't
always fulfilling this.
This patch changes code that opens new version of table to
always do this linking in. It also streamlines cleanup process
for cases when error occurs while we have new version of table
open.
******
WL#3726 "DDL locking for all metadata objects"
Add libmysqld/mdl.cc to .bzrignore.
******
Backport of:
------------------------------------------------------------
revno: 2630.4.6
committer: Dmitry Lenev <dlenev@mysql.com>
branch nick: mysql-6.0-3726-w
timestamp: Sun 2008-05-25 00:33:22 +0400
message:
WL#3726 "DDL locking for all metadata objects".
Addition to the fix of assert failures in kill.test caused by
changes for this worklog.
Make sure we close the new table only once.
------------------------------------------------------------
revno: 2630.13.2
committer: Davi Arnaut <davi@sun.com>
branch nick: WL4284-6.0
timestamp: Thu 2008-07-03 18:26:51 -0300
message:
Remove unused USING_TRANSACTIONS macro which unnecessarily
cumbers the code. This macro is a historical leftover and
has no practical use since its unconditionally defined.
revno: 2476.784.2
committer: davi@moksha.local
timestamp: Thu 2007-09-27 16:56:27 -0300
message:
Bug#28870 check that table locks are released/reset
The problem is that some mysql_lock_tables error paths are not
resetting the tables lock type back to TL_UNLOCK. If the lock
types are not reset properly, a table might be returned to the
table cache with wrong lock_type.
The proposed fix is to ensure that the tables lock type is always
properly reset when mysql_lock_tables fails. This is a
incompatible change with respect to the process state information.
