WITH READ LOCK and FLUSH TABLES <list> WITH READ LOCK are
incompatible", which adds information about waits caused by
FLUSH TABLES statement to deadlock detector in MDL subsystem.
Remove API supporting caching of pointers to TABLE_SHARE
object in MDL subsystem and all code related to it.
The problem was that locking requirements of code
implementing this API conflicted with locking requirements
of code which adds information about waits caused by flushes
to deadlock detector in MDL subsystem (the former needed to
lock LOCK_open or its future equivalent while having
write-lock on MDL_lock's rwlock, and the latter needs to be
able to read-lock MDL_lock rwlock while owning LOCK_open or
its future equivalent).
Since caching of pointers to TABLE_SHARE objects in MDL
subsystem didn't bring expected performance benefits we
decided to remove caching API rather than try to come up
with some complex solution for this problem.
WITH READ LOCK and FLUSH TABLES <list> WITH READ LOCK are
incompatible", which adds information about waits caused by
FLUSH TABLES statement to deadlock detector in MDL subsystem.
Remove API supporting caching of pointers to TABLE_SHARE
object in MDL subsystem and all code related to it.
The problem was that locking requirements of code
implementing this API conflicted with locking requirements
of code which adds information about waits caused by flushes
to deadlock detector in MDL subsystem (the former needed to
lock LOCK_open or its future equivalent while having
write-lock on MDL_lock's rwlock, and the latter needs to be
able to read-lock MDL_lock rwlock while owning LOCK_open or
its future equivalent).
Since caching of pointers to TABLE_SHARE objects in MDL
subsystem didn't bring expected performance benefits we
decided to remove caching API rather than try to come up
with some complex solution for this problem.
libmysqld/Makefile.am:
The new file added.
mysql-test/r/index_merge_myisam.result:
subquery_cache optimization option added.
mysql-test/r/myisam_mrr.result:
subquery_cache optimization option added.
mysql-test/r/subquery_cache.result:
The subquery cache tests added.
mysql-test/r/subselect3.result:
Subquery cache switched off to avoid changing read statistics.
mysql-test/r/subselect3_jcl6.result:
Subquery cache switched off to avoid changing read statistics.
mysql-test/r/subselect_no_mat.result:
subquery_cache optimization option added.
mysql-test/r/subselect_no_opts.result:
subquery_cache optimization option added.
mysql-test/r/subselect_no_semijoin.result:
subquery_cache optimization option added.
mysql-test/r/subselect_sj.result:
subquery_cache optimization option added.
mysql-test/r/subselect_sj_jcl6.result:
subquery_cache optimization option added.
mysql-test/t/subquery_cache.test:
The subquery cache tests added.
mysql-test/t/subselect3.test:
Subquery cache switched off to avoid changing read statistics.
sql/CMakeLists.txt:
The new file added.
sql/Makefile.am:
The new files added.
sql/item.cc:
Expression cache item (Item_cache_wrapper) added.
Item_ref and Item_field fixed for correct usage of result field and fast resolwing in SP.
sql/item.h:
Expression cache item (Item_cache_wrapper) added.
Item_ref and Item_field fixed for correct usage of result field and fast resolwing in SP.
sql/item_cmpfunc.cc:
Subquery cache added.
sql/item_cmpfunc.h:
Subquery cache added.
sql/item_subselect.cc:
Subquery cache added.
sql/item_subselect.h:
Subquery cache added.
sql/item_sum.cc:
Registration of subquery parameters added.
sql/mysql_priv.h:
subquery_cache optimization option added.
sql/mysqld.cc:
subquery_cache optimization option added.
sql/opt_range.cc:
Fix due to subquery cache.
sql/opt_subselect.cc:
Parameters of the function cahnged.
sql/procedure.h:
.h file guard added.
sql/sql_base.cc:
Registration of subquery parameters added.
sql/sql_class.cc:
Option to allow add indeces to temporary table.
sql/sql_class.h:
Item iterators added.
Option to allow add indeces to temporary table.
sql/sql_expression_cache.cc:
Expression cache for caching subqueries added.
sql/sql_expression_cache.h:
Expression cache for caching subqueries added.
sql/sql_lex.cc:
Registration of subquery parameters added.
sql/sql_lex.h:
Registration of subqueries and subquery parameters added.
sql/sql_select.cc:
Subquery cache added.
sql/sql_select.h:
Subquery cache added.
sql/sql_union.cc:
A new parameter to the function added.
sql/sql_update.cc:
A new parameter to the function added.
sql/table.cc:
Procedures to manage temporarty tables index added.
sql/table.h:
Procedures to manage temporarty tables index added.
storage/maria/ha_maria.cc:
Fix of handler to allow destoy a table in case of error during the table creation.
storage/maria/ha_maria.h:
.h file guard added.
storage/myisam/ha_myisam.cc:
Fix of handler to allow destoy a table in case of error during the table creation.
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.
client/mysqldump.c:
Pass my_free directly as its signature is compatible with the
callback type -- which wasn't the case for free_table_ent.
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.
Apart strict-aliasing warnings, fix the remaining warnings
generated by GCC 4.4.4 -Wall and -Wextra flags.
One major source of warnings was the in-house function my_bcmp
which (unconventionally) took pointers to unsigned characters
as the byte sequences to be compared. Since my_bcmp and bcmp
are deprecated functions whose only difference with memcmp is
the return value, every use of the function is replaced with
memcmp as the special return value wasn't actually being used
by any caller.
There were also various other warnings, mostly due to type
mismatches, missing return values, missing prototypes, dead
code (unreachable) and ignored return values.
BUILD/SETUP.sh:
Remove flags that are implied by -Wall and -Wextra.
Do not warn about unused parameters in C++.
BUILD/check-cpu:
Print only the compiler version instead of verbose banner.
Although the option is gcc specific, the check was only
being used for GCC specific checks anyway.
client/mysql.cc:
bcmp is no longer defined.
client/mysqltest.cc:
Pass a string to function expecting a format string.
Replace use of bcmp with memcmp.
cmd-line-utils/readline/Makefile.am:
Always define _GNU_SOURCE when compiling GNU readline.
Required to make certain prototypes visible.
cmd-line-utils/readline/input.c:
Condition for the code to be meaningful.
configure.in:
Remove check for bcmp.
extra/comp_err.c:
Use appropriate type.
extra/replace.c:
Replace use of bcmp with memcmp.
extra/yassl/src/crypto_wrapper.cpp:
Do not ignore the return value of fgets. Retrieve the file
position if fgets succeed -- if it fails, the function will
bail out and return a error.
extra/yassl/taocrypt/include/blowfish.hpp:
Use a single array instead of accessing positions of the sbox_
through a subscript to pbox_.
extra/yassl/taocrypt/include/runtime.hpp:
One definition of such functions is enough.
extra/yassl/taocrypt/src/aes.cpp:
Avoid potentially ambiguous conditions.
extra/yassl/taocrypt/src/algebra.cpp:
Rename arguments to avoid shadowing related warnings.
extra/yassl/taocrypt/src/blowfish.cpp:
Avoid potentially ambiguous conditions.
extra/yassl/taocrypt/src/integer.cpp:
Do not define type within a anonymous union.
Use a variable to return a value instead of
leaving the result in a register -- compiler
does not know the logic inside the asm.
extra/yassl/taocrypt/src/misc.cpp:
Define handler for pure virtual functions.
Remove unused code.
extra/yassl/taocrypt/src/twofish.cpp:
Avoid potentially ambiguous conditions.
extra/yassl/testsuite/test.hpp:
Function must have C language linkage.
include/m_string.h:
Remove check which relied on bcmp being defined -- they weren't
being used as bcmp is only visible when _BSD_SOURCE is defined.
include/my_bitmap.h:
Remove bogus helpers which were used only in a few files and
were causing warnings about dead code.
include/my_global.h:
Due to G++ bug, always silence false-positive uninitialized
variables warnings when compiling C++ code with G++.
Remove bogus helper.
libmysql/Makefile.shared:
Remove built-in implementation of bcmp.
mysql-test/lib/My/SafeProcess/safe_process.cc:
Cast pid to largest possible type for a process identifier.
mysys/mf_loadpath.c:
Leave space of the ending nul.
mysys/mf_pack.c:
Replace bcmp with memcmp.
mysys/my_bitmap.c:
Dead code removal.
mysys/my_gethwaddr.c:
Remove unused variable.
mysys/my_getopt.c:
Silence bogus uninitialized variable warning.
Do not cast away the constant qualifier.
mysys/safemalloc.c:
Cast to expected type.
mysys/thr_lock.c:
Silence bogus uninitialized variable warning.
sql/field.cc:
Replace bogus helper with a more appropriate logic which is
used throughout the code.
sql/item.cc:
Remove bogus logical condition which always evaluates to TRUE.
sql/item_create.cc:
Simplify code to avoid signedness related warnings.
sql/log_event.cc:
Replace use of bcmp with memcmp.
No need to use helpers for simple bit operations.
sql/log_event_old.cc:
Replace bmove_align with memcpy.
sql/mysqld.cc:
Move use declaration of variable to the ifdef block where it
is used. Remove now-unnecessary casts and arguments.
sql/set_var.cc:
Replace bogus helpers with simple and classic bit operations.
sql/slave.cc:
Cast to expected type and silence bogus warning.
sql/sql_class.h:
Don't use enum values as bit flags, the supposed type safety is
bogus as the combined bit flags are not a value in the enumeration.
sql/udf_example.c:
Only declare variable when necessary.
sql/unireg.h:
Replace use of bmove_align with memcpy.
storage/innobase/os/os0file.c:
Silence bogus warning.
storage/myisam/mi_open.c:
Remove bogus cast, DBUG_DUMP expects a pointer to unsigned
char.
storage/myisam/mi_page.c:
Remove bogus cast, DBUG_DUMP expects a pointer to unsigned
char.
strings/bcmp.c:
Remove built-in bcmp.
strings/ctype-ucs2.c:
Silence bogus warning.
tests/mysql_client_test.c:
Use a appropriate type as expected by simple_command().
Apart strict-aliasing warnings, fix the remaining warnings
generated by GCC 4.4.4 -Wall and -Wextra flags.
One major source of warnings was the in-house function my_bcmp
which (unconventionally) took pointers to unsigned characters
as the byte sequences to be compared. Since my_bcmp and bcmp
are deprecated functions whose only difference with memcmp is
the return value, every use of the function is replaced with
memcmp as the special return value wasn't actually being used
by any caller.
There were also various other warnings, mostly due to type
mismatches, missing return values, missing prototypes, dead
code (unreachable) and ignored return values.
DROP/ALTER/CREATE DATABASE with open HANDLER".
Remove wait_for_condition() which became unused after
database locks were replaced with MDL scoped locks.
If one needs functionality provided by this call one can
always use THD::enter_cond()/exit_cond() methods.
Also removed an unused include from sql_db.cc and updated
comment describing one of used includes to reflect current
situation.
DROP/ALTER/CREATE DATABASE with open HANDLER".
Remove wait_for_condition() which became unused after
database locks were replaced with MDL scoped locks.
If one needs functionality provided by this call one can
always use THD::enter_cond()/exit_cond() methods.
Also removed an unused include from sql_db.cc and updated
comment describing one of used includes to reflect current
situation.
DATABASE with open HANDLER"
Remove LOCK_create_db, database name locks, and use metadata locks instead.
This exposes CREATE/DROP/ALTER DATABASE statements to the graph-based
deadlock detector in MDL, and paves the way for a safe, deadlock-free
implementation of RENAME DATABASE.
Database DDL statements will now take exclusive metadata locks on
the database name, while table/view/routine DDL statements take
intention exclusive locks on the database name. This prevents race
conditions between database DDL and table/view/routine DDL.
(e.g. DROP DATABASE with concurrent CREATE/ALTER/DROP TABLE)
By adding database name locks, this patch implements
WL#4450 "DDL locking: CREATE/DROP DATABASE must use database locks" and
WL#4985 "DDL locking: namespace/hierarchical locks".
The patch also changes code to use init_one_table() where appropriate.
The new lock_table_names() function requires TABLE_LIST::db_length to
be set correctly, and this is taken care of by init_one_table().
This patch also adds a simple template to help work with
the mysys HASH data structure.
Most of the patch was written by Konstantin Osipov.
DATABASE with open HANDLER"
Remove LOCK_create_db, database name locks, and use metadata locks instead.
This exposes CREATE/DROP/ALTER DATABASE statements to the graph-based
deadlock detector in MDL, and paves the way for a safe, deadlock-free
implementation of RENAME DATABASE.
Database DDL statements will now take exclusive metadata locks on
the database name, while table/view/routine DDL statements take
intention exclusive locks on the database name. This prevents race
conditions between database DDL and table/view/routine DDL.
(e.g. DROP DATABASE with concurrent CREATE/ALTER/DROP TABLE)
By adding database name locks, this patch implements
WL#4450 "DDL locking: CREATE/DROP DATABASE must use database locks" and
WL#4985 "DDL locking: namespace/hierarchical locks".
The patch also changes code to use init_one_table() where appropriate.
The new lock_table_names() function requires TABLE_LIST::db_length to
be set correctly, and this is taken care of by init_one_table().
This patch also adds a simple template to help work with
the mysys HASH data structure.
Most of the patch was written by Konstantin Osipov.
Remove mysql_lock_have_duplicate(), since now we always
have TABLE_LIST objects for MyISAMMRG children
in lex->query_tables and keep it till the end of the
statement (sub-statement).
mysql-test/r/merge.result:
Update results (Bug#54811).
mysql-test/t/merge-big.test:
Update to new wait state.
mysql-test/t/merge.test:
Add a test case for Bug#54811.
sql/lock.cc:
Remove a function that is now unused.
sql/lock.h:
Remove a function that is now unused.
sql/sql_base.cc:
Don't try to search for duplicate table among THR_LOCK objects, TABLE_LIST list contains all used tables.
Remove mysql_lock_have_duplicate(), since now we always
have TABLE_LIST objects for MyISAMMRG children
in lex->query_tables and keep it till the end of the
statement (sub-statement).
switching binlog format to ROW
BUG 52616 fixed the case which the user would switch from STMT to
ROW binlog format, but the server would silently ignore it. After
that fix thd->is_current_stmt_binlog_format_row() reports correct
value at logging time and events are logged in ROW (as expected)
instead of STMT as they were previously and wrongly logged.
However, the fix was only partially complete, because on
disconnect, at THD cleanup, the implicit logging of temporary
tables is conditionally performed. If the binlog_format==ROW and
thd->is_current_stmt_binlog_format_row() is true then DROPs are
not logged. Given that the user can switch from STMT to ROW, this
is wrong because the server cannot tell, just by relying on the
ROW binlog format, that the tables have been dropped before. This
is effectively similar to the MIXED scenario when a switch from
STMT to ROW is triggered.
We fix this by removing this condition from
close_temporary_tables.
mysql-test/extra/binlog_tests/drop_temp_table.test:
Added binlog test case.
mysql-test/suite/binlog/r/binlog_row_drop_tmp_tbl.result:
Result changes because:
- there is a missing drop on three temporary tables
- it now contains results for the test added
mysql-test/suite/binlog/r/binlog_row_mix_innodb_myisam.result:
Result now contains the implicit drop for the temporary table.
mysql-test/suite/binlog/r/binlog_stm_drop_tmp_tbl.result:
Result file changed because it now contains results for added
test case.
mysql-test/suite/rpl/r/rpl_drop_temp.result:
Result file changed because it now contains results for added
test case.
mysql-test/suite/rpl/t/rpl_drop_temp.test:
Added replication test case.
sql/sql_base.cc:
Removed the condition that would make the server to skip
logging implicit drops when ROW binary log format mode was
in use.
Additionally, deployed DBUG_ENTER/RETURN macros.
switching binlog format to ROW
BUG 52616 fixed the case which the user would switch from STMT to
ROW binlog format, but the server would silently ignore it. After
that fix thd->is_current_stmt_binlog_format_row() reports correct
value at logging time and events are logged in ROW (as expected)
instead of STMT as they were previously and wrongly logged.
However, the fix was only partially complete, because on
disconnect, at THD cleanup, the implicit logging of temporary
tables is conditionally performed. If the binlog_format==ROW and
thd->is_current_stmt_binlog_format_row() is true then DROPs are
not logged. Given that the user can switch from STMT to ROW, this
is wrong because the server cannot tell, just by relying on the
ROW binlog format, that the tables have been dropped before. This
is effectively similar to the MIXED scenario when a switch from
STMT to ROW is triggered.
We fix this by removing this condition from
close_temporary_tables.
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.
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.
