The assert was triggered if a connection executing TRUNCATE
on a InnoDB table was killed during open_tables.
This bug was fixed in the scope of Bug #45643
"InnoDB does not support replication of TRUNCATE TABLE".
This patch adds test coverage to innodb_mysql_sync.test.
subsystem. Fix a number of caveates that the previous
implementation suffered from, including unprotected
access to shared data and lax resource accounting
(share->ref_count) that could lead to deadlocks.
The new implementation still suffers from a number
of potential deadlocks in some edge cases, and this is
still not enabled by default. Especially since performance
testing has shown that it gives only marginable (not even
exceeding measuring accuracy) improvements.
@todo:
- Remove calls to close_cached_tables() with REFRESH_FAST,
and have_lock, because they break the MDL cache.
- rework FLUSH TABLES <list> to not use close_cached_tables()
- make sure that whenever we set TABLE_SHARE::version to
0 we free MDL cache references to it.
sql/mdl.cc:
We may cache references to TABLE_SHARE objects in
MDL_lock objects for tables. Create a separate
MDL_lock class to represent a table.
sql/mdl.h:
Adjust the MDL caching API to avoid races.
sql/sql_base.cc:
Move all caching functionality close together.
Implement a solution for deadlocks caused by
close_cached_tables() when MDL cache is enabled (incomplete).
sql/sql_yacc.yy:
Adjust FLUSH rule to do the necessary initialization of
TABLE_LIST elements used in for FLUSH TABLES <list>, and thus
work OK with flush_mdl_cache() function.
subsystem. Fix a number of caveates that the previous
implementation suffered from, including unprotected
access to shared data and lax resource accounting
(share->ref_count) that could lead to deadlocks.
The new implementation still suffers from a number
of potential deadlocks in some edge cases, and this is
still not enabled by default. Especially since performance
testing has shown that it gives only marginable (not even
exceeding measuring accuracy) improvements.
@todo:
- Remove calls to close_cached_tables() with REFRESH_FAST,
and have_lock, because they break the MDL cache.
- rework FLUSH TABLES <list> to not use close_cached_tables()
- make sure that whenever we set TABLE_SHARE::version to
0 we free MDL cache references to it.
an atomic counter"
Split the large LOCK_open section in open_table().
Do not call open_table_from_share() under LOCK_open.
Remove thd->version.
This fixes
Bug#50589 "Server hang on a query evaluated using a temporary
table"
Bug#51557 "LOCK_open and kernel_mutex are not happy together"
Bug#49463 "LOCK_table and innodb are not nice when handler
instances are created".
This patch has effect on storage engines that rely on
ha_open() PSEA method being called under LOCK_open.
In particular:
1) NDB is broken and left unfixed. NDB relies on LOCK_open
being kept as part of ha_open(), since it uses auto-discovery.
While previously the NDB open code was race-prone, now
it simply fails on asserts.
2) HEAP engine had a race in ha_heap::open() when
a share for the same table could be added twice
to the list of shares, or a dangling reference to a share
stored in HEAP handler. This patch aims to address this
problem by 'pinning' the newly created share in the
internal HEAP engine share list until at least one
handler instance is created using that share.
include/heap.h:
Add members to HP_CREATE_INFO.
Declare heap_release_share().
sql/lock.cc:
Remove thd->version, use thd->open_tables->s->version instead.
sql/repl_failsafe.cc:
Remove thd->version.
sql/sql_base.cc:
- close_thread_table(): move handler cleanup code outside the critical section protected by LOCK_open.
- remove thd->version
- split the large critical section in open_table() that
opens a new table from share and is protected by LOCK_open
into 2 critical sections, thus reducing the critical path.
- make check_if_table_exists() acquire LOCK_open internally.
- use thd->open_tables->s->version instead of thd->refresh_version to make sure that all tables in
thd->open_tables are in the same refresh series.
sql/sql_base.h:
Add declaration for check_if_table_exists().
sql/sql_class.cc:
Remove init_open_tables_state(), it's now equal to
reset_open_tables_state().
sql/sql_class.h:
Remove thd->version, THD::init_open_tables_state().
sql/sql_plugin.cc:
Use table->m_needs_reopen to mark the table as stale
rather than manipulate with thd->version, which is no more.
sql/sql_udf.cc:
Use table->m_needs_reopen to mark the table as stale
rather than manipulate with thd->version, which is no more.
sql/table.h:
Remove an unused variable.
sql/tztime.cc:
Use table->m_needs_reopen to mark the table as stale
rather than manipulate with thd->version, which is no more.
storage/heap/CMakeLists.txt:
Add heap tests to cmake build files.
storage/heap/ha_heap.cc:
Fix a race when ha_heap::ha_open() could insert two
HP_SHARE objects into the internal share list or store
a dangling reference to a share in ha_heap instance,
or wrongly set implicit_emptied.
storage/heap/hp_create.c:
Optionally pin a newly created share in the list of shares
by increasing its open_count. This is necessary to
make sure that a newly created share doesn't disappear while
a HP_INFO object is being created to reference it.
storage/heap/hp_open.c:
When adding a new HP_INFO object to the list of objects
in the heap share, make sure the open_count is not increased
twice.
storage/heap/hp_test1.c:
Adjust the test to new function signatures.
storage/heap/hp_test2.c:
Adjust the test to new function signatures.
an atomic counter"
Split the large LOCK_open section in open_table().
Do not call open_table_from_share() under LOCK_open.
Remove thd->version.
This fixes
Bug#50589 "Server hang on a query evaluated using a temporary
table"
Bug#51557 "LOCK_open and kernel_mutex are not happy together"
Bug#49463 "LOCK_table and innodb are not nice when handler
instances are created".
This patch has effect on storage engines that rely on
ha_open() PSEA method being called under LOCK_open.
In particular:
1) NDB is broken and left unfixed. NDB relies on LOCK_open
being kept as part of ha_open(), since it uses auto-discovery.
While previously the NDB open code was race-prone, now
it simply fails on asserts.
2) HEAP engine had a race in ha_heap::open() when
a share for the same table could be added twice
to the list of shares, or a dangling reference to a share
stored in HEAP handler. This patch aims to address this
problem by 'pinning' the newly created share in the
internal HEAP engine share list until at least one
handler instance is created using that share.
make tdc_refresh_version an atomic counter".
To avoid orphaned TABLE_SHARE objects left in the
cache, make sure that wherever we set table->s->version
we take care of removing all unused table share objects
from the table cache.
Always set table->s->version under LOCK_open, to make sure
that no other connection sees an old value of the
version and adds the table to unused_tables list.
Add an assert to table_def_unuse_table() that we never
'unuse' a talbe of a share that has an old version.
With this patch, only three places are left in the code
that manipulate with table->s->version:
- tdc_remove_table(). In most cases we have an X mdl lock
in tdc_remove_table(), the two remaining cases when we
don't are 'FLUSH TABLE' and mysql_admin_table().
- sql_view.cc - a crude hack that needs a separate fix
- initial assignment from refresh_version in table.cc.
sql/sql_base.cc:
Add an assert.
Don't manipulate with table->s->version in auto-repair, auto-discover.
Use tdc_remove_table() in auto_repair_table() and drop_open_table().
sql/sql_table.cc:
Remove dead code from mysql_admin_table().
Manipulate with table->s->version through the TDC API.
make tdc_refresh_version an atomic counter".
To avoid orphaned TABLE_SHARE objects left in the
cache, make sure that wherever we set table->s->version
we take care of removing all unused table share objects
from the table cache.
Always set table->s->version under LOCK_open, to make sure
that no other connection sees an old value of the
version and adds the table to unused_tables list.
Add an assert to table_def_unuse_table() that we never
'unuse' a talbe of a share that has an old version.
With this patch, only three places are left in the code
that manipulate with table->s->version:
- tdc_remove_table(). In most cases we have an X mdl lock
in tdc_remove_table(), the two remaining cases when we
don't are 'FLUSH TABLE' and mysql_admin_table().
- sql_view.cc - a crude hack that needs a separate fix
- initial assignment from refresh_version in table.cc.
mutex protecting thd->open_tables".
We should not manipulate with table->s->version outside the
table definition cache code, but use the TDC API
to achieve the desired result.
Fix one violation: close_all_tables_for_name().
sql/sql_base.cc:
Use tdc_remove_table(TDC_RT_REMOVE_ALL) to expel the
table share in close_all_tables_for_name, rather
than manipulate with the table cache explicitly.
Make sure that close_cached_tables() calls
close_all_tables_for_name() after closing all the involved
handlers. The rest of the code was inspected to
make sure that mysql_ha_rm_tables() is called.
sql/sql_handler.cc:
Add a method to close all HANDLER cursors for a list
of tables.
sql/sql_handler.h:
Add declaration for mysql_ha_flush_tables().
mutex protecting thd->open_tables".
We should not manipulate with table->s->version outside the
table definition cache code, but use the TDC API
to achieve the desired result.
Fix one violation: close_all_tables_for_name().
thd->open_tables"
thd->open_tables list is not normally accessed concurrently
except for one case: when the connection has open SQL
HANDLER tables, and we want to perform a DDL on the table,
we want to abort waits on MyISAM thr_lock of those connections
that prevent the DDL from proceeding, and iterate
over thd->open_tables list to find out the tables on which
the thread is waiting.
In 5.5 we mostly use deadlock detection and soft deadlock
prevention, as opposed to "hard" deadlock prevention
of 5.1, which would abort any transaction that
may cause a deadlock. The only remaining case when
neither deadlock detection nor deadlock prevention
is implemented in 5.5 is HANDLER SQL, where we use
old good thr_lock_abort() technique form 5.1.
Thus, replace use of LOCK_open to protect thd->open_tables
with thd->LOCK_ha_data (a lock protecting various session
private data).
This is a port of the work done for 5.5.4 for review
and inclusion into 5.5.5.
sql/sql_base.cc:
Use thd->LOCK_ha_data (systematically) to set
thd->open_tables.
sql/sql_class.h:
Implement THD::set_open_tables().
sql/sql_cursor.cc:
Use thd->LOCK_ha_data (systematically) to set
thd->open_tables.
sql/sql_handler.cc:
Use thd->LOCK_ha_data (systematically) to set
thd->open_tables.
Acquisition of LOCK_open is moved inside close_thread_table().
sql/sql_table.cc:
Acquisition of LOCK_open is moved inside close_thread_tables().
thd->open_tables"
thd->open_tables list is not normally accessed concurrently
except for one case: when the connection has open SQL
HANDLER tables, and we want to perform a DDL on the table,
we want to abort waits on MyISAM thr_lock of those connections
that prevent the DDL from proceeding, and iterate
over thd->open_tables list to find out the tables on which
the thread is waiting.
In 5.5 we mostly use deadlock detection and soft deadlock
prevention, as opposed to "hard" deadlock prevention
of 5.1, which would abort any transaction that
may cause a deadlock. The only remaining case when
neither deadlock detection nor deadlock prevention
is implemented in 5.5 is HANDLER SQL, where we use
old good thr_lock_abort() technique form 5.1.
Thus, replace use of LOCK_open to protect thd->open_tables
with thd->LOCK_ha_data (a lock protecting various session
private data).
This is a port of the work done for 5.5.4 for review
and inclusion into 5.5.5.
1) No mutex and no function call if we're not using
plugins.
2) If we're above the table definition cache limit,
delete the oldest unused share, not the share on our hands.
sql/sql_base.cc:
If we're above the table definition cache limit,
delete the oldest unused share, not the share on our hands.
sql/sql_lex.cc:
No mutex and no function call if we're not using
plugins.
1) No mutex and no function call if we're not using
plugins.
2) If we're above the table definition cache limit,
delete the oldest unused share, not the share on our hands.
locks for DML statements and changes the way MDL locks
are acquired/granted in contended case.
Instead of backing-off when a lock conflict is encountered
and waiting for it to go away before restarting open_tables()
process we now wait for lock to be released without releasing
any previously acquired locks. If conflicting lock goes away
we resume opening tables. If waiting leads to a deadlock we
try to resolve it by backing-off and restarting open_tables()
immediately.
As result both waiting for possibility to acquire and
acquiring of a metadata lock now always happen within the
same MDL API call. This has allowed to make release of a lock
and granting it to the most appropriate pending request an
atomic operation.
Thanks to this it became possible to wake up during release
of lock only those waiters which requests can be satisfied
at the moment as well as wake up only one waiter in case
when granting its request would prevent all other requests
from being satisfied. This solves thundering herd problem
which occured in cases when we were releasing some lock and
woke up many waiters for SNRW or X locks (this was the issue
in bug#52289 "performance regression for MyISAM in sysbench
OLTP_RW test".
This also allowed to implement more fair (FIFO) scheduling
among waiters with the same priority.
It also opens the door for introducing new types of requests
for metadata locks such as low-prio SNRW lock which is
necessary in order to support LOCK TABLES LOW_PRIORITY WRITE.
Notice that after this sometimes can report ER_LOCK_DEADLOCK
error in cases in which it has not happened before.
Particularly we will always report this error if waiting for
conflicting lock has happened in the middle of transaction
and resulted in a deadlock. Before this patch the error was
not reported if deadlock could have been resolved by backing
off all metadata locks acquired by the current statement.
mysql-test/r/mdl_sync.result:
Added test coverage for some aspects of deadlock handling in
metadata locking subsystem.
Adjusted test case after removing back-off in general case
when conflicting metadata lock is encountered during
open_tables() (now this happens only if waiting for
conflicting lock to go away leads to a deadlock).
mysql-test/r/sp_sync.result:
Adjusted test case after removing back-off in general case
when conflicting metadata lock is encountered during
open_tables() (now this happens only if waiting for
conflicting lock to go away leads to a deadlock).
mysql-test/suite/perfschema/r/dml_setup_instruments.result:
Adjusted test results after renaming MDL_context::
m_waiting_for_lock rwlock to m_LOCK_waiting_for.
mysql-test/suite/rpl/r/rpl_sp.result:
Adjusted test case after implementing new approach to
acquiring metadata locks in open_tables(). We no longer
release all MDL locks acquired by statement before waiting
for conflicting lock to go away. As result DROP FUNCTION
statement has to wait for DML statement which managed to
acquire metadata lock on function being dropped and now
waits for other conflicting metadata lock to go away.
mysql-test/suite/rpl/t/rpl_sp.test:
Adjusted test case after implementing new approach to
acquiring metadata locks in open_tables(). We no longer
release all MDL locks acquired by statement before waiting
for conflicting lock to go away. As result DROP FUNCTION
statement has to wait for DML statement which managed to
acquire metadata lock on function being dropped and now
waits for other conflicting metadata lock to go away.
mysql-test/t/mdl_sync.test:
Added test coverage for some aspects of deadlock handling in
metadata locking subsystem.
Adjusted test case after removing back-off in general case
when conflicting metadata lock is encountered during
open_tables() (now this happens only if waiting for
conflicting lock to go away leads to a deadlock).
mysql-test/t/sp_sync.test:
Adjusted test case after removing back-off in general case
when conflicting metadata lock is encountered during
open_tables() (now this happens only if waiting for
conflicting lock to go away leads to a deadlock).
sql/mdl.cc:
Changed MDL subsystem to support new approach to acquring
metadata locks in open tables and more fair and efficient
scheduling of metadata locks. To implement this:
- Made releasing of the lock and granting it to the most
appropriate pending request atomic operation. As result it
became possible to wake up only those waiters requests from
which can be satisfied at the moment as well as wake-up
only one waiter in case when granting its request would
prevent all other requests from being satisfied.
This solved thundering herd problem which occured in cases
when we were releasing some lock and woke up many waiters
for SNRW or X locks (this was the issue in Bug #52289
"performance regression for MyISAM in sysbench OLTP_RW
test".
To emphasize above changes wake_up_waiters() was renamed
to MDL_context::reschedule_waiters().
- Changed code to add tickets for new requests to the back of
waiters queue and to select tickets to be satisfied from
the head of the queue if possible (this makes scheduling of
requests with the same priority fair). To be able to do
this efficiently we now use for waiting and granted queues
version of I_P_List class which provides fast push_back()
method.
- Members and methods of MDL_context related to sending
and waiting for signal were moved to separate MDL_wait
class.
- Since in order to avoid race conditions we must grant the
lock only to the context which was not chosen as a victim
of deadlock, killed or aborted due to timeout
MDL_wait::set_status() (former awake()) was changed not to
send signal if signal slot is already occupied and to
indicate this fact through its return value. As another
consequence MDL_wait::timed_wait() method was changed to
handle timeout (optionally) and abort due to kill as
signals which make signal slot occupied.
- Renamed MDL_context::acquire_lock_impl() to acquire_lock().
Changed it to be able correctly process requests for shared
locks when there are open HANDLERs, made this method more
optimized for acquisition of shared locks. As part of this
change moved code common between try_acquire_lock() and
acquire_lock() to new try_acquire_lock_impl() method.
Also adjusted acquire_lock()'s code to take into account
the fact that in cases when lock is granted as result of
MDL_context::reschedule_waiters() call (i.e. when it is
granted after waiting for lock conflict to go away)
updating MDL_lock state is responsibility of the thread
calling reschedule_waiters().
- Changed MDL_context::find_deadlock() to send VICTIM
signal even if victim is the context which has initiated
deadlock detection. This is required in order to avoid
races in cases when the same context simultaneously is
chosen as a victim and its request for lock is satisfied.
As result return value of this method became unnecessary
and it was changed to return void.
Adjusted MDL_lock::find_deadlock() method to take into
account that now there can be a discrepancy between
MDL_context::m_waiting_for value being set and real state
of the ticket this member points to.
- Renamed MDL_context::m_waiting_for_lock to m_LOCK_waiting_for
and MDL_context::stop_waiting() to done_waiting_for().
- Finally, removed MDL_context::wait_for_lock() method.
sql/mdl.h:
Changed MDL subsystem to support new approach to acquring
metadata locks in open tables and more fair and efficient
scheduling of metadata locks. To implement this:
- Members and methods of MDL_context related to sending
and waiting for signal were moved to separate MDL_wait
class.
- Since now in order to avoid race conditions we must grant
the lock only to the context which was not chosen as a
victim of deadlock, killed or aborted due to timeout
MDL_wait::set_status (former awake()) was changed not to
send signal if signal slot is already occupied and to
indicate this fact through its return value.
Also NORMAL_WAKE_UP signal became GRANTED, and timeouts
and aborts due to kill became full blown signals rather
than simple return values.
- MDL_wait::timed_wait() now takes extra parameter that
indicates whether signal should be set if timeout is
reached.
- Enabled fast push_back() operation in MDL_context::m_tickets
list to make move_ticket_after_trans_sentinel() method more
efficient.
- Removed MDL_context::wait_for_lock() method.
- Renamed MDL_context::m_waiting_for_lock to m_LOCK_waiting_for
and MDL_context::stop_waiting() to done_waiting_for().
- MDL_context::acquire_lock_impl() became acquire_lock().
- Introduced MDL_context::try_acquire_lock_impl() as a
place for code shared by try_acquire_lock and
acquire_lock().
- Due to fact that now VICTIM signal is sent even if victim
is the context which has initiated deadlock detection
find_deadlock() no longer needs a return value.
sql/sql_base.cc:
Implemented new approach to acquiring metadata locks in
open_tables(). We no longer perform back-off when conflicting
metadata lock is encountered. Instead we wait for this lock
to go away while holding all locks which were acquired so
far. Back-off is only used in situation when further waiting
will cause a deadlock which could be avoided by performing
back-off and restarting open_tables() process. Absence of
waiting between back-off and restart of acquiring metadata
locks can't lead to livelocks as MDL subsystem was changed
to make release of lock and granting it to waiting lock
an atomic action, so back-off will automatically give way
to other participants of deadlock loop.
Accordingly:
- open_table_get_mdl_lock() and open_and_process_routine()
were changed to wait for conflicting metadata lock to
go away without back-off. Only if such wait leads to a
deadlock back-off is requested. As part of this change
new error handler class was introduced which converts,
if possible, ER_LOCK_DEADLOCK error to a request for
back-off and re-start of open_tables() process.
- Open_table_context::recover_from_failed_open() was changed
not to wait in case of metadata lock conflict. Instead we
immediately proceed to re-acquiring locks.
- Open_table_context::request_backoff_action() now always
emits error if back-off is requested in the middle of
transaction as we can't be sure that releasing lock
which were acquired only by current statement will
resolve a deadlock. Before this patch such situations were
successfully detected thanks to the fact that we called
MDL_context::wait_for_lock() method in
recover_from_failed_open().
- In order to avoid deadlocks open_tables() code was adjusted
to flush open HANDLERs for which there are pending requests
for X locks before restarting the process of acquiring
metadata locks.
- Changed close_tables_for_reopen() not to reset MDL_request
for tables belonging to the tail of prelocking list. It is
no longer necessary as these MDL_request objects won't be
used for any waiting.
- Adjusted comment in tdc_wait_for_old_version() to avoid
mentioning removed MDL_context::wait_for_lock() method.
sql/sql_base.h:
As we no longer wait for conflicting metadata lock away in
Open_table_context::recover_from_failed_open() method,
Open_table_context::OT_WAIT_MDL_LOCK action was renamed to
OT_MDL_CONFLICT.
Also Open_table_context::m_failed_mdl_request became
unnecessary and was removed.
sql/sql_plist.h:
Extended I_P_List template to support efficient push_back()
operation if it is parameterized with an appropriate policy
class.
sql/sql_show.cc:
Adjusted code after removal of MDL_context::wait_for_lock()
method. Now if one needs to acquire metadata lock with waiting
one has to use a variant of MDL_context::acquire_lock() method.
locks for DML statements and changes the way MDL locks
are acquired/granted in contended case.
Instead of backing-off when a lock conflict is encountered
and waiting for it to go away before restarting open_tables()
process we now wait for lock to be released without releasing
any previously acquired locks. If conflicting lock goes away
we resume opening tables. If waiting leads to a deadlock we
try to resolve it by backing-off and restarting open_tables()
immediately.
As result both waiting for possibility to acquire and
acquiring of a metadata lock now always happen within the
same MDL API call. This has allowed to make release of a lock
and granting it to the most appropriate pending request an
atomic operation.
Thanks to this it became possible to wake up during release
of lock only those waiters which requests can be satisfied
at the moment as well as wake up only one waiter in case
when granting its request would prevent all other requests
from being satisfied. This solves thundering herd problem
which occured in cases when we were releasing some lock and
woke up many waiters for SNRW or X locks (this was the issue
in bug#52289 "performance regression for MyISAM in sysbench
OLTP_RW test".
This also allowed to implement more fair (FIFO) scheduling
among waiters with the same priority.
It also opens the door for introducing new types of requests
for metadata locks such as low-prio SNRW lock which is
necessary in order to support LOCK TABLES LOW_PRIORITY WRITE.
Notice that after this sometimes can report ER_LOCK_DEADLOCK
error in cases in which it has not happened before.
Particularly we will always report this error if waiting for
conflicting lock has happened in the middle of transaction
and resulted in a deadlock. Before this patch the error was
not reported if deadlock could have been resolved by backing
off all metadata locks acquired by the current statement.
Conflicts:
Text conflict in mysql-test/r/archive.result
Contents conflict in mysql-test/r/innodb_bug38231.result
Text conflict in mysql-test/r/mdl_sync.result
Text conflict in mysql-test/suite/binlog/t/disabled.def
Text conflict in mysql-test/suite/rpl_ndb/r/rpl_ndb_binlog_format_errors.result
Text conflict in mysql-test/t/archive.test
Contents conflict in mysql-test/t/innodb_bug38231.test
Text conflict in mysql-test/t/mdl_sync.test
Text conflict in sql/sp_head.cc
Text conflict in sql/sql_show.cc
Text conflict in sql/table.cc
Text conflict in sql/table.h
Conflicts:
Text conflict in mysql-test/r/archive.result
Contents conflict in mysql-test/r/innodb_bug38231.result
Text conflict in mysql-test/r/mdl_sync.result
Text conflict in mysql-test/suite/binlog/t/disabled.def
Text conflict in mysql-test/suite/rpl_ndb/r/rpl_ndb_binlog_format_errors.result
Text conflict in mysql-test/t/archive.test
Contents conflict in mysql-test/t/innodb_bug38231.test
Text conflict in mysql-test/t/mdl_sync.test
Text conflict in sql/sp_head.cc
Text conflict in sql/sql_show.cc
Text conflict in sql/table.cc
Text conflict in sql/table.h
transactional SELECT and ALTER TABLE ... REBUILD PARTITION".
Make open flags part of Open_table_context.
This allows to simplify some code and (in future)
enforce the invariant that we don't, say, request a back
off on the table when there is MYSQL_OPEN_IGNORE_FLUSH
flag.
sql/sql_base.cc:
open_table() flags are part of Open_table_context.
Remove dead code that would check for OPEN_VIEW_NO_PARSE,
which is not an open table flag.
sql/sql_base.h:
Move flags to Open_table_context. Reorder Open_table_context
members to compact the structure footprint.
sql/sql_insert.cc:
Update with a new calling signature of open_table().
sql/sql_table.cc:
Update with a new calling signature of open_table().
transactional SELECT and ALTER TABLE ... REBUILD PARTITION".
Make open flags part of Open_table_context.
This allows to simplify some code and (in future)
enforce the invariant that we don't, say, request a back
off on the table when there is MYSQL_OPEN_IGNORE_FLUSH
flag.
transactional SELECT and ALTER TABLE ... REBUILD PARTITION".
Move declarations of sql_base.cc classes to sql_base.h
(previously declared in sql_class.h).
Became possible after a header file split.
sql/sql_base.cc:
Make sql_base.h the first include in sql_base.cc.
sql/sql_base.h:
Add declarations of Prelocking_strategy and Open_table_context.
sql/sql_class.h:
Remove declarations of Prelocking_strategy and Open_table_context
(moved).
transactional SELECT and ALTER TABLE ... REBUILD PARTITION".
Move declarations of sql_base.cc classes to sql_base.h
(previously declared in sql_class.h).
Became possible after a header file split.
without FOR UPDATE is causing a lock".
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 implements minimal version of the fix for the
specific problem described in the bug-report which supposed
to be not too risky for pushing into 5.1 tree.
The 5.5 tree already contains a more appropriate solution
which also addresses other related issues like bug 53921
"Wrong locks for SELECTs used stored functions may lead
to broken SBR".
This patch tries to solve the problem by ensuring that
TL_READ_DEFAULT lock which is set in the parser for
tables participating in subqueries at open_tables()
time is interpreted as TL_READ_NO_INSERT or TL_READ.
TL_READ is used only if we know that this is a SELECT
and that this particular table is not used by a stored
function.
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 (as well as in 5.0 and 5.1 before fix for bug 39843)
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.
The patch for bug 39843 broke this behaviour (which was not
documented or tested), and started to use locking reads for
all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE.
This patch restores 4.1 behaviour.
This patch should be mostly null-merged into 5.5 tree.
mysql-test/include/check_concurrent_insert.inc:
Added auxiliary script which allows to check if statement
reading table allows concurrent inserts in it.
mysql-test/include/check_no_concurrent_insert.inc:
Added auxiliary script which allows to check that statement
reading table doesn't allow concurrent inserts in it.
mysql-test/include/check_no_row_lock.inc:
Added auxiliary script which allows to check if statement
reading table doesn't take locks on its rows.
mysql-test/include/check_shared_row_lock.inc:
Added auxiliary script which allows to check if statement
reading table takes shared locks on some of its rows.
mysql-test/r/bug39022.result:
After bug #46947 'Embedded SELECT without FOR UPDATE is
causing a lock' was fixed test case for bug 39022 has to
be adjusted in order to trigger execution path on which
original problem was encountered.
mysql-test/r/innodb_mysql_lock2.result:
Added coverage for handling of locking in various cases when
we read data from InnoDB tables (includes test case for
bug #46947 'Embedded SELECT without FOR UPDATE is causing a
lock').
mysql-test/r/lock_sync.result:
Added coverage for handling of locking in various cases when
we read data from MyISAM tables.
mysql-test/t/bug39022.test:
After bug #46947 'Embedded SELECT without FOR UPDATE is
causing a lock' was fixed test case for bug 39022 has to
be adjusted in order to trigger execution path on which
original problem was encountered.
mysql-test/t/innodb_mysql_lock2.test:
Added coverage for handling of locking in various cases when
we read data from InnoDB tables (includes test case for
bug #46947 'Embedded SELECT without FOR UPDATE is causing a
lock').
mysql-test/t/lock_sync.test:
Added coverage for handling of locking in various cases when
we read data from MyISAM tables.
sql/mysql_priv.h:
Function read_lock_type_for_table() now takes pointers to
LEX and TABLE_LIST elements as its arguments since to
correctly determine lock type it needs to know what
statement is being performed and whether table element for
which lock type to be determined belongs to prelocking list.
sql/sql_base.cc:
Changed read_lock_type_for_table() to return a weak TL_READ
type of lock in cases when we are executing SELECT (and so
won't update tables directly) and table doesn't belong to
statement's prelocking list and thus can't be used by a
stored function. It is OK to do so since in this case table
won't be used by statement or function call which will be
written to the binary log, so serializability requirements
for it can be relaxed.
One of results from this change is that SELECTs on InnoDB
tables no longer takes shared row locks for tables which
are used in subqueries (i.e. bug #46947 is fixed).
Another result is that for similar SELECTs on MyISAM tables
concurrent inserts are allowed.
In order to implement this change signature of
read_lock_type_for_table() function was changed to
take pointers to LEX and TABLE_LIST objects.
sql/sql_update.cc:
Function read_lock_type_for_table() now takes pointers to
LEX and TABLE_LIST elements as its arguments since to
correctly determine lock type it needs to know what
statement is being performed and whether table element for
which lock type to be determined belongs to prelocking list.
without FOR UPDATE is causing a lock".
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 implements minimal version of the fix for the
specific problem described in the bug-report which supposed
to be not too risky for pushing into 5.1 tree.
The 5.5 tree already contains a more appropriate solution
which also addresses other related issues like bug 53921
"Wrong locks for SELECTs used stored functions may lead
to broken SBR".
This patch tries to solve the problem by ensuring that
TL_READ_DEFAULT lock which is set in the parser for
tables participating in subqueries at open_tables()
time is interpreted as TL_READ_NO_INSERT or TL_READ.
TL_READ is used only if we know that this is a SELECT
and that this particular table is not used by a stored
function.
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 (as well as in 5.0 and 5.1 before fix for bug 39843)
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.
The patch for bug 39843 broke this behaviour (which was not
documented or tested), and started to use locking reads for
all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE.
This patch restores 4.1 behaviour.
This patch should be mostly null-merged into 5.5 tree.
The thd->variables.option_bits & OPTION_BIN_LOG is currently abused:
it's both a system variable and an implementation switch. The current
approach to this option bit breaks the session variable encapsulation.
Besides it is allowed to change @@session.sql_bin_log within a
transaction what may lead to not correctly logging a transaction.
To fix the problems, we created a thd->variables variable to represent
the "sql_log_bin" and prohibited its update inside a transaction or
sub-statement.
mysql-test/suite/binlog/r/binlog_stm_unsafe_warning.result:
Updated result file. The reason the warnings are removed is
related to BUG#50312.
mysql-test/suite/binlog/r/binlog_switch_inside_trans.result:
Checks when is possible to change the option @@session.sql_log_bin.
mysql-test/suite/binlog/t/binlog_switch_inside_trans.test:
Checks when is possible to change the option @@session.sql_log_bin.
mysql-test/suite/rpl/r/rpl_non_direct_stm_mixing_engines.result:
Updated the result file with warnings that were being printed
due to the wrong use of the thd->variables.option_bits and
sql_log_bin_top_level variables.
mysql-test/suite/rpl/r/rpl_stm_mixing_engines.result:
Updated the result file with warnings that were being printed
due to the wrong use of the thd->variables.option_bits and
sql_log_bin_top_level variables.
sql/share/errmsg-utf8.txt:
Introduces two error messages to notify that the @@session.sql_log_bin
cannot be changed inside a sub-statement or transaction.
sql/sql_base.cc:
Removes the variable sql_log_bin_toplevel and uses
the session variable sql_log_bin.
sql/sql_class.cc:
Replaces the variable sql_log_bin_toplevel by the
(variables.option_bits & OPTION_BIN_LOG).
sql/sql_class.h:
Removes the variable sql_log_bin_toplevel and creates
a session variable sql_log_bin.
sql/sys_vars.cc:
Checks when the sql_log_bin can be correctly updated.
The thd->variables.option_bits & OPTION_BIN_LOG is currently abused:
it's both a system variable and an implementation switch. The current
approach to this option bit breaks the session variable encapsulation.
Besides it is allowed to change @@session.sql_bin_log within a
transaction what may lead to not correctly logging a transaction.
To fix the problems, we created a thd->variables variable to represent
the "sql_log_bin" and prohibited its update inside a transaction or
sub-statement.
SELECT and ALTER TABLE ... REBUILD PARTITION".
ALTER TABLE on InnoDB table (including partitioned tables)
acquired exclusive locks on rows of table being altered.
In cases when there was concurrent transaction which did
locking reads from this table this sometimes led to a
deadlock which was not detected by MDL subsystem nor by
InnoDB engine (and was reported only after exceeding
innodb_lock_wait_timeout).
This problem stemmed from the fact that ALTER TABLE acquired
TL_WRITE_ALLOW_READ lock on table being altered. This lock
was interpreted as a write lock and thus for table being
altered handler::external_lock() method was called with
F_WRLCK as an argument. As result InnoDB engine treated
ALTER TABLE as an operation which is going to change data
and acquired LOCK_X locks on rows being read from old
version of table.
In case when there was a transaction which already acquired
SR metadata lock on table and some LOCK_S locks on its rows
(e.g. by using it in subquery of DML statement) concurrent
ALTER TABLE was blocked at the moment when it tried to
acquire LOCK_X lock before reading one of these rows.
The transaction's attempt to acquire SW metadata lock on
table being altered led to deadlock, since it had to wait
for ALTER TABLE to release SNW lock. This deadlock was not
detected and got resolved only after timeout expiring
because waiting were happening in two different subsystems.
Similar deadlocks could have occured in other situations.
This patch tries to solve the problem by changing ALTER TABLE
implementation to use TL_READ_NO_INSERT lock instead of
TL_WRITE_ALLOW_READ. After this step handler::external_lock()
is called with F_RDLCK as an argument and InnoDB engine
correctly interprets ALTER TABLE as operation which only
reads data from original version of table. Thanks to this
ALTER TABLE acquires only LOCK_S locks on rows it reads.
This, in its turn, causes inter-subsystem deadlocks to go
away, as all potential lock conflicts and thus deadlocks will
be limited to metadata locking subsystem:
- When ALTER TABLE reads rows from table being altered it
can't encounter any locks which conflict with LOCK_S row
locks. There should be no concurrent transactions holding
LOCK_X row locks. Such a transaction should have been
acquired SW metadata lock on table first which would have
conflicted with ALTER's SNW lock.
- Vice versa, when DML which runs concurrently with ALTER
TABLE tries to lock row it should be requesting only LOCK_S
lock which is compatible with locks acquired by ALTER,
as otherwise such DML must own an SW metadata lock on table
which would be incompatible with ALTER's SNW lock.
mysql-test/r/innodb_mysql_lock2.result:
Added test for bug #51263 "Deadlock between transactional
SELECT and ALTER TABLE ... REBUILD PARTITION".
mysql-test/suite/rpl_ndb/r/rpl_ndb_binlog_format_errors.result:
Since CREATE TRIGGER no longer acquires write lock on table
it is no longer interpreted as an operation which modifies
table data and therefore no longer fails if invoked for
SBR-only engine in ROW mode.
mysql-test/suite/rpl_ndb/t/rpl_ndb_binlog_format_errors.test:
Since CREATE TRIGGER no longer acquires write lock on table
it is no longer interpreted as an operation which modifies
table data and therefore no longer fails if invoked for
SBR-only engine in ROW mode.
mysql-test/t/innodb_mysql_lock2.test:
Added test for bug #51263 "Deadlock between transactional
SELECT and ALTER TABLE ... REBUILD PARTITION".
sql/ha_partition.cc:
When ALTER TABLE creates a new partition to be filled from
other partition lock it in F_WRLCK mode instead of using
mode which was used for locking the whole table (it is
F_RDLCK now).
sql/lock.cc:
Replaced conditions which used TL_WRITE_ALLOW_READ
lock type with equivalent conditions using
TL_WRITE_ALLOW_WRITE. This should allow to get rid
of TL_WRITE_ALLOW_READ lock type eventually.
sql/mdl.cc:
Updated outdated comment to reflect current situation.
sql/sql_base.cc:
Replaced conditions which used TL_WRITE_ALLOW_READ
lock type with equivalent conditions using
TL_WRITE_ALLOW_WRITE. This should allow to get rid
of TL_WRITE_ALLOW_READ lock type eventually.
sql/sql_table.cc:
mysql_admin_table():
Use TL_WRITE_ALLOW_WRITE lock type instead of
TL_WRITE_ALLOW_READ to determine that we need to acquire
upgradable metadata lock. This should allow to completely
get rid of TL_WRITE_ALLOW_READ in long term.
mysql_recreate_table():
ALTER TABLE now requires TL_READ_NO_INSERT thr_lock.c lock
instead of TL_WRITE_ALLOW_READ.
sql/sql_trigger.cc:
Changed CREATE/DROP TRIGGER implementation to use
TL_READ_NO_INSERT lock instead of TL_WRITE_ALLOW_READ lock.
The latter is no longer necessary since:
a) We now can rely on metadata locks to achieve proper
isolation between two DDL statements or DDL and DML
statements.
b) This statement does not change any data in table so there
is no need to inform storage engine about it.
sql/sql_yacc.yy:
Changed implementation of ALTER TABLE (and CREATE/DROP INDEX
as a consequence) to use TL_READ_NO_INSERT lock instead of
TL_WRITE_ALLOW_READ lock. This is possible since:
a) We now can rely on metadata locks to achieve proper
isolation between two DDL statements or DDL and DML
statements.
b) This statement only reads data in table being open.
We write data only to the new version of table and
then replace with it old version of table under
X metadata lock.
Thanks to this change InnoDB will no longer acquire LOCK_X
locks on rows being read by ALTER TABLE (instead LOCK_S
locks will be acquired) and thus cause of bug #51263
"Deadlock between transactional SELECT and ALTER TABLE ...
REBUILD PARTITION" is removed.
Did the similar change for CREATE TRIGGER (see comments
for sql_trigger.cc for details).
SELECT and ALTER TABLE ... REBUILD PARTITION".
ALTER TABLE on InnoDB table (including partitioned tables)
acquired exclusive locks on rows of table being altered.
In cases when there was concurrent transaction which did
locking reads from this table this sometimes led to a
deadlock which was not detected by MDL subsystem nor by
InnoDB engine (and was reported only after exceeding
innodb_lock_wait_timeout).
This problem stemmed from the fact that ALTER TABLE acquired
TL_WRITE_ALLOW_READ lock on table being altered. This lock
was interpreted as a write lock and thus for table being
altered handler::external_lock() method was called with
F_WRLCK as an argument. As result InnoDB engine treated
ALTER TABLE as an operation which is going to change data
and acquired LOCK_X locks on rows being read from old
version of table.
In case when there was a transaction which already acquired
SR metadata lock on table and some LOCK_S locks on its rows
(e.g. by using it in subquery of DML statement) concurrent
ALTER TABLE was blocked at the moment when it tried to
acquire LOCK_X lock before reading one of these rows.
The transaction's attempt to acquire SW metadata lock on
table being altered led to deadlock, since it had to wait
for ALTER TABLE to release SNW lock. This deadlock was not
detected and got resolved only after timeout expiring
because waiting were happening in two different subsystems.
Similar deadlocks could have occured in other situations.
This patch tries to solve the problem by changing ALTER TABLE
implementation to use TL_READ_NO_INSERT lock instead of
TL_WRITE_ALLOW_READ. After this step handler::external_lock()
is called with F_RDLCK as an argument and InnoDB engine
correctly interprets ALTER TABLE as operation which only
reads data from original version of table. Thanks to this
ALTER TABLE acquires only LOCK_S locks on rows it reads.
This, in its turn, causes inter-subsystem deadlocks to go
away, as all potential lock conflicts and thus deadlocks will
be limited to metadata locking subsystem:
- When ALTER TABLE reads rows from table being altered it
can't encounter any locks which conflict with LOCK_S row
locks. There should be no concurrent transactions holding
LOCK_X row locks. Such a transaction should have been
acquired SW metadata lock on table first which would have
conflicted with ALTER's SNW lock.
- Vice versa, when DML which runs concurrently with ALTER
TABLE tries to lock row it should be requesting only LOCK_S
lock which is compatible with locks acquired by ALTER,
as otherwise such DML must own an SW metadata lock on table
which would be incompatible with ALTER's SNW lock.
The problem was that TRUNCATE TABLE didn't take a exclusive
lock on a table if it resorted to truncating via delete of
all rows in the table. Specifically for InnoDB tables, this
could break proper isolation as InnoDB ends up aborting some
granted locks when truncating a table.
The solution is to take a exclusive metadata lock before
TRUNCATE TABLE can proceed. This guarantees that no other
transaction is using the table.
Incompatible change: Truncate via delete no longer fails
if sql_safe_updates is activated (this was a undocumented
side effect).
libmysqld/CMakeLists.txt:
Add new files to the build list.
libmysqld/Makefile.am:
Add new files to the build list.
mysql-test/extra/binlog_tests/binlog_truncate.test:
Add test case for Bug#42643
mysql-test/include/mix1.inc:
Update test case as TRUNCATE TABLE now grabs a exclusive lock.
Ensure that TRUNCATE waits for granted locks on the table.
mysql-test/suite/binlog/t/binlog_truncate_innodb.test:
As with other data modifying statements, TRUNCATE is still not
possible in a transaction with isolation level READ COMMITTED
or READ UNCOMMITED. It would be possible to implement so, but
it is not worth the effort.
mysql-test/suite/binlog/t/binlog_truncate_myisam.test:
Test under different binlog formats.
mysql-test/suite/binlog/t/disabled.def:
Re-enable test case.
mysql-test/t/innodb_bug38231.test:
Truncate no longer works with row-level locks.
mysql-test/t/mdl_sync.test:
Ensure that a acquired lock is not given up due to a conflict.
mysql-test/t/partition_innodb_semi_consistent.test:
End transaction as to release metadata locks.
mysql-test/t/truncate.test:
A metadata lock is now taken before the object is verified.
sql/CMakeLists.txt:
Add new files to the build list.
sql/Makefile.am:
Add new files to the build list.
sql/datadict.cc:
Introduce a new file specific for data dictionary operations.
sql/datadict.h:
Add header file.
sql/sql_base.cc:
Rename data dictionary function.
sql/sql_bitmap.h:
Include dependency.
sql/sql_delete.cc:
Move away from relying on mysql_delete() to delete all rows of
a table. Thus, move any bits related to truncate to sql_truncate.cc
sql/sql_delete.h:
Remove parameter.
sql/sql_parse.cc:
Add protection against the global read lock -- a intention
exclusive lock can be acquired in the truncate path.
sql/sql_show.cc:
Add sync point for testing scenarios where a pending flush
is ignored.
sql/sql_truncate.cc:
Acquire a shared metadata lock before accessing table metadata.
Upgrade the lock to a exclusive one if the table can be re-created.
Rework binlog rules to better reflect the requirements.
sql/sql_yacc.yy:
Set appropriate lock types for table to be truncated.
sql/table.h:
Move to data dictionary header.
The problem was that TRUNCATE TABLE didn't take a exclusive
lock on a table if it resorted to truncating via delete of
all rows in the table. Specifically for InnoDB tables, this
could break proper isolation as InnoDB ends up aborting some
granted locks when truncating a table.
The solution is to take a exclusive metadata lock before
TRUNCATE TABLE can proceed. This guarantees that no other
transaction is using the table.
Incompatible change: Truncate via delete no longer fails
if sql_safe_updates is activated (this was a undocumented
side effect).
transactional SELECT and ALTER TABLE ... REBUILD PARTITION".
The goal of this patch is to decouple type of metadata
lock acquired for table by open_tables() from type of
table-level lock to be acquired on it.
To achieve this we change approach to how we determine what
type of metadata lock should be acquired on table to be open.
Now instead of inferring it at open_tables() time from flags
and type of table-level lock we rely on that type of metadata
lock is properly set at parsing time and is not changed
further.
sql/ha_ndbcluster.cc:
Now one needs to properly initialize table list element's
MDL_request object before calling mysql_rm_table_part2().
sql/lock.cc:
lock_table_names() no longer initializes table list elements'
MDL_request objects. Now proper initialization of these
requests is a responsibility of the caller.
sql/lock.h:
Removed MYSQL_OPEN_TAKE_UPGRADABLE_MDL flag which became
unnecessary. Thanks to the fact that we don't reset type of
requests for metadata locks between re-executions we now can
figure out that upgradable locks are requested by simply
looking at their type which were set in the parser. As result
this flag became redundant.
sql/mdl.h:
Added version of new operator which simplifies allocation of
MDL_request objects on a MEM_ROOT.
sql/sp_head.cc:
Added comment explaining why it is OK to infer type of
metadata lock to request from type of table-level lock
for prelocking.
Added enum_mdl_type argument to sp_add_to_query_tables()
to simplify its usage in trigger implementation.
sql/sp_head.h:
Added enum_mdl_type argument to sp_add_to_query_tables()
to simplify its usage in trigger implementation.
sql/sql_base.cc:
- open_table_get_mdl_lock():
Preserve type of MDL_request for table list element which
was set in the parser by creating MDL_request objects on
memory root if MYSQL_OPEN_FORCE_SHARED_MDL or
MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL flag were specified.
Thanks to this and to the fact that we no longer reset
type of requests for metadata locks between re-executions
we no longer need to acquire exclusive metadata lock on
table to be created in a special way. This lock is acquired
by code handling acquiring of upgradable locks.
Also changed signature/calling convention for this function
to simplify its usage.
- Accordingly special lock strategy for table list elements
which was used for such locks became unnecessary and was
removed. Other strategies were renamed.
- Since we no longer have guarantee that MDL_request object
which were not satisfied due to lock conflict belongs to
table list element Open_table_context class and its methods
were extended to remember pointer to MDL_request which has
caused problem at request_backoff_action() time and use it
in recover_from_failed_open(). Similar approach is used
for cases when problem from which we need to recover is
not related to MDL but to the table itself. In this case
we store pointer to the element of table list.
- Changed open_tables()/open_tables_check_upgradable_mdl()/
open_tables_acquire_upgradable_mdl() not to rely on
MYSQL_OPEN_TAKE_UPGRADABLE_MDL flag to understand when
upgradable metadata locks should be acquired and not to
infer type of MDL lock from type of table-level lock.
Instead we assume that type of MDL to be acquired was set
in the parser (we can do this as type of MDL_request is
no longer reset between re-executions).
sql/sql_class.h:
Since we no longer have guarantee that MDL_request object
which were not satisfied due to lock conflict belongs to
table list element Open_table_context class and its methods
were extended to remember pointer to MDL_request which has
caused problem at request_backoff_action() time and use it
in recover_from_failed_open(). Similar approach is used
for cases when problem from which we need to recover is
not related to MDL but to the table itself. In this case
we store pointer to the element of table list.
sql/sql_db.cc:
Now one needs to properly initialize table list element's
MDL_request object before calling mysql_rm_table_part2()
or mysql_rename_tables().
sql/sql_lex.cc:
st_select_lex/st_select_lex_node::add_table_to_list() method
now has argument which allows specify type of metadata lock
to be requested for table list element being added.
sql/sql_lex.h:
- st_select_lex/st_select_lex_node::add_table_to_list()
method now has argument which specifies type of metadata
lock to be requested for table list element being added.
This allows to explicitly set type of MDL lock to be
acquired for a DDL statement in parser. It is also more
future-proof than inferring type of MDL request from type
of table-level lock.
- Added Yacc_state::m_mdl_type member which specifies which
type of metadata lock should be requested for tables to be
added to table list by a grammar rule in cases when the same
rule is used in several statements requiring different kinds
of metadata locks.
sql/sql_parse.cc:
- st_select_lex::add_table_to_list() method now has argument
which specifies type of metadata lock to be requested for
table list element being added. This allows to explicitly
set type of MDL lock to be acquired for a DDL statement in
parser. It is also more future-proof than inferring type of
MDL request from type of table-level lock.
- EXCLUSIVE_DOWNGRADABLE_MDL lock strategy has a new name -
OTLS_DOWNGRADE_IF_EXISTS.
- Adjusted LOCK TABLES implementation to the fact that we no
longer infer type of metadata lock to be acquired from table
level lock and that type of MDL request is set at parsing.
And thus MYSQL_OPEN_TAKE_UPGRADABLE_MDL flag became
unnecessary.
sql/sql_prepare.cc:
TABLE_LIST's lock strategy SHARED_MDL was renamed to OTLS_NONE
as now it means that metadata lock should not be changed during
call to open_table() (if it has been already acquired) and is
also used for exclusive metadata lock.
sql/sql_show.cc:
st_select_lex::add_table_to_list() method now has argument
which specifies type of metadata lock to be requested for
table list element being added.
sql/sql_table.cc:
- Adjusted mysql_admin_table()'s code to the fact that
open_tables() no longer determines what kind of metadata
lock should be obtained basing on type of table-level
lock and flags. Instead type of metadata lock for table
to be open should be set before calling open_tables().
- Changed mysql_alter_table() code to the facts:
a) that now it is responsibility of caller to properly
initalize MDL_request in table list elements before calling
lock_table_names()
b) and that MYSQL_OPEN_TAKE_UPGRADABLE_MDL is no longer
necessary since type of metadata lock to be obtained
at open_tables() time is set during parsing.
- Changed code of mysql_recreate_table() to properly set
type of metadata and table-level lock to be obtained
by mysql_alter_table() which it calls.
sql/sql_trigger.cc:
Instead of relying on MYSQL_OPEN_TAKE_UPGRADABLE_MDL flag to
force open_tables() to take an upgradable lock we now specify
exact type of lock to be taken when constructing table list
element for table to be open for CREATE/DROP TRIGGER.
sql/sql_view.cc:
We no longer use TABLE_LIST::EXCLUSIVE_MDL strategy to force
open_tables() to take an exclusive metadata lock on view to
be created. Instead we rely on parser setting proper type of
metadata lock to request and open_tables() acquiring it.
This became possible thanks to the fact that we no longer
reset type of MDL_request between statement re-executions.
sql/sql_yacc.yy:
Instead of inferring type of MDL_request for table to be
open from type of table-level lock and flags passed to
open_tables() we now explicitly specify them at parsing.
This became possible thanks to the fact that we no longer
reset type of MDL_request between statement re-executions.
In future this should allow to decouple type of metadata
lock from type of table-level lock.
The only exception to this approach is statements implemented
through mysql_admin_table() which re-uses same table list
element several times with different types of table-level
and metadata locks.
We now also properly initialize MDL_request objects for table
list elements which are later passed to lock_table_names()
function.
sql/table.cc:
Do not reset type of MDL_request between statement
re-executions. This became unnecessesary as we no longer
change type of MDL_request residing in table list element.
In its turn this change allows to set type of MDL_request
only once - at parsing time.
sql/table.h:
Got rid of TABLE_LIST::EXCLUSIVE_MDL lock strategy.
Now we can specify that we need to acquire exclusive lock
on table to be processed by open_tables() through setting
an appropriate type of MDL_request at parsing time (this
became possible thanks to the fact that we no longer reset
types of MDL_request's belonging to table list elements
between statement re-execution).
Strategy SHARED_MDL was renamed to OTLS_NONE as now it
means that metadata lock should not be changed during call
to open_table() (if it has been already acquired) and is
also used for exclusive metadata lock.
Strategy EXCLUSIVE_DOWNGRADABLE_MDL was renamed to
OTLS_DOWNGRADE_IF_EXISTS.
transactional SELECT and ALTER TABLE ... REBUILD PARTITION".
The goal of this patch is to decouple type of metadata
lock acquired for table by open_tables() from type of
table-level lock to be acquired on it.
To achieve this we change approach to how we determine what
type of metadata lock should be acquired on table to be open.
Now instead of inferring it at open_tables() time from flags
and type of table-level lock we rely on that type of metadata
lock is properly set at parsing time and is not changed
further.
FOR UPDATE is causing a lock".
This patch tries to address problems which were exposed
during backporting of original patch to 5.1 tree.
- It ensures that we don't change locking behavior of simple
SELECT statements on InnoDB tables when they are executed
under LOCK TABLES ... READ and with @@innodb_table_locks=0.
Also we no longer pass TL_READ_DEFAULT/TL_WRITE_DEFAULT
lock types, which are supposed to be parser-only, to
handler::start_stmt() method.
- It makes check_/no_concurrent_insert.inc auxiliary scripts
more robust against changes in test cases that use them
and also ensures that they don't unnecessarily change
environment of caller.
mysql-test/include/check_concurrent_insert.inc:
Reset DEBUG_SYNC facility before and after using it in
auxiliary script. This makes this script more robust against
changes in test cases calling it. It also ensures that script
does not unnecessarily change environment of caller.
mysql-test/include/check_no_concurrent_insert.inc:
Reset DEBUG_SYNC facility before and after using it in
auxiliary script. This makes this script more robust against
changes in test cases calling it. It also ensures that script
does not unnecessarily change environment of caller.
mysql-test/r/innodb-lock.result:
Added coverage for LOCK TABLES ... READ behavior in
@@innodb_table_locks = 0 mode. This test also checks
that an appropriate type of lock is passed to
handler::start_stmt() method.
mysql-test/t/innodb-lock.test:
Added coverage for LOCK TABLES ... READ behavior in
@@innodb_table_locks = 0 mode. This test also checks
that an appropriate type of lock is passed to
handler::start_stmt() method.
sql/sql_base.cc:
Since we no longer set TL_READ as lock type for tables used
in simple SELECT right in the parser, in order to preserve
behavior for such statements on InnoDB tables when in
LOCK TABLES mode with @innodb_table_locks = 0,
check_lock_and_start_stmt() had to be changed to convert
TL_READ_DEFAULT to an appropriate type of read lock before
passing it to handler::start_stmt() method.
We do similar thing for TL_WRITE_DEFAULT as this lock type
is also supposed to be parser-only type.
As consequence read_lock_type_for_table() had to be
adjusted to behave properly when it is called from
check_lock_and_start_stmt() in prelocked mode.
FOR UPDATE is causing a lock".
This patch tries to address problems which were exposed
during backporting of original patch to 5.1 tree.
- It ensures that we don't change locking behavior of simple
SELECT statements on InnoDB tables when they are executed
under LOCK TABLES ... READ and with @@innodb_table_locks=0.
Also we no longer pass TL_READ_DEFAULT/TL_WRITE_DEFAULT
lock types, which are supposed to be parser-only, to
handler::start_stmt() method.
- It makes check_/no_concurrent_insert.inc auxiliary scripts
more robust against changes in test cases that use them
and also ensures that they don't unnecessarily change
environment of caller.
mode
Post-push fix after backporting the patch to 5.1-bugteam:
1 - changed the name of some variables to be equivalent to pe.
2 - fixed that patch to mark a statement as unsafe when both a
self-logging eng. and regular eng. are accessed and one of them
is updated.
mode
Post-push fix after backporting the patch to 5.1-bugteam:
1 - changed the name of some variables to be equivalent to pe.
2 - fixed that patch to mark a statement as unsafe when both a
self-logging eng. and regular eng. are accessed and one of them
is updated.
