| Commit message (Collapse) | Author | Age | Files | Lines |
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bug #46947 "Embedded SELECT without FOR UPDATE is causing
a lock".
Fixed comments in tests. Improved comments and performance of
auxiliary scripts.
mysql-test/include/check_concurrent_insert.inc:
Changed script to use temporary table for backing up data in
order to make this operation less expensive. Made script more
a bit generic by allowing to use multi-column tables with it.
Improved comments.
mysql-test/include/check_no_concurrent_insert.inc:
Changed script to use temporary table for backing up data in
order to make this operation less expensive. Made script more
a bit generic by allowing to use multi-column tables with it.
Improved comments.
mysql-test/include/check_no_row_lock.inc:
Improved comments in auxiliary script.
mysql-test/r/innodb_mysql_lock2.result:
Fixed errors in comments for test.
mysql-test/r/lock_sync.result:
Fixed typo in comments for test.
mysql-test/t/innodb_mysql_lock2.test:
Fixed errors in comments for test.
mysql-test/t/lock_sync.test:
Fixed typo in comments for test.
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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).
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Fix for bug #46947 "Embedded SELECT without FOR UPDATE is
causing a lock", with after-review fixes.
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 tries to solve this problem by rethinking our
approach to how we handle locking for SELECT and subqueries.
Now we always set TL_READ_DEFAULT lock type for all cases
when we read data. When at open_tables() time this lock
is interpreted as TL_READ_NO_INSERT or TL_READ depending
on whether this statement as a whole or call to function
which uses particular table should be written to the
binary log or not (if yes then statement should be properly
serialized with concurrent statements and stronger lock
should be acquired).
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 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.
On of the patches for 5.0 broke this behaviour (which was not documented
or tested), and started to use locking reads fora all subqueries in SELECT ...
FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
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/log_event.cc:
Since LEX::lock_option member was removed we no longer can
rely on its value in Load_log_event::print_query() to
determine that log event correponds to LOAD DATA CONCURRENT
statement (this was not correct in all situations anyway).
A new Load_log_event's member was introduced as a replacement.
It is initialized at event object construction time and
explicitly indicates whether LOAD DATA was concurrent.
sql/log_event.h:
Since LEX::lock_option member was removed we no longer can
rely on its value in Load_log_event::print_query() to
determine that log event correponds to LOAD DATA CONCURRENT
statement (this was not correct in all situations anyway).
A new Load_log_event's member was introduced as a replacement.
It is initialized at event object construction time and
explicitly indicates whether LOAD DATA was concurrent.
sql/sp_head.cc:
sp_head::reset_lex():
Before parsing substatement reset part of parser state
which needs this (e.g. set Yacc_state::m_lock_type to
default value).
sql/sql_acl.cc:
Since LEX::reset_n_backup_query_tables_list() now also
resets LEX::sql_command member (as it became part of
Query_tables_list class) we have to restore it in cases
when while working with proxy Query_table_list we assume
that LEX::sql_command still corresponds to original SQL
command being executed (for example, when we are logging
statement to the binary log while having Query_tables_list
reset and backed up).
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 statement which
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 Query_tables_list and TABLE_LIST objects.
sql/sql_base.h:
- Function read_lock_type_for_table() now takes pointers
to Query_tables_list 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_lex.cc:
- Removed LEX::lock_option and st_select_lex::lock_option
members. Places in parser that were using them now use
Yacc_state::m_lock_type instead.
- To emphasize that LEX::sql_command member is used during
process of opening and locking of tables it was moved to
Query_tables_list class. It is now reset by
Query_tables_list::reset_query_tables_list() method.
sql/sql_lex.h:
- Removed st_select_lex::lock_option member as there is no
real need for per-SELECT lock type (HIGH_PRIORITY option
should apply to the whole statement. FOR UPDATE/LOCK IN
SHARE MODE clauses can be handled without this member).
The main effect which was achieved by introduction of this
member, i.e. using TL_READ_DEFAULT lock type for
subqueries, is now achieved by setting LEX::lock_option
(or rather its replacement - Yacc_state::m_lock_type) to
TL_READ_DEFAULT in almost all cases.
- To emphasize that LEX::sql_command member is used during
process of opening and locking of tables it was moved to
Query_tables_list class.
- Replaced LEX::lock_option with Yacc_state::m_lock_type
in order to emphasize that this value is relevant only
during parsing. Unlike for LEX::lock_option the default
value for Yacc_state::m_lock_type is TL_READ_DEFAULT.
Note that for cases when it is OK to take a "weak" read
lock (e.g. simple SELECT) this lock type will be converted
to TL_READ at open_tables() time. So this change won't
cause negative change in behavior for such statements.
OTOH this change ensures that, for example, for SELECTs
which are used in stored functions TL_READ_NO_INSERT lock
is taken when necessary and as result calls to such stored
functions can be written to the binary log with correct
serialization.
sql/sql_load.cc:
Load_log_event constructor now requires a parameter that
indicates whether LOAD DATA is concurrent.
sql/sql_parse.cc:
LEX::lock_option was replaced with Yacc_state::m_lock_type.
And instead of resetting the latter implicitly in
mysql_init_multi_delete() we do it explicitly in the
places in parser which call this function.
sql/sql_priv.h:
- To be able more easily distinguish high-priority SELECTs
in st_select_lex::print() method added flag for
HIGH_PRIORITY option.
sql/sql_select.cc:
Changed code not to rely on LEX::lock_option to determine
that it is high-priority SELECT. It was replaced with
Yacc_state::m_lock_type which is accessible only at
parse time. So instead of LEX::lock_option we now rely
on a newly introduced flag for st_select_lex::options -
SELECT_HIGH_PRIORITY.
sql/sql_show.cc:
Since LEX::reset_n_backup_query_tables_list() now also
resets LEX::sql_command member (as it became part of
Query_tables_list class) we have to restore it in cases
when while working with proxy Query_table_list we assume
that LEX::sql_command still corresponds to original SQL
command being executed.
sql/sql_table.cc:
Since LEX::reset_query_tables_list() now also resets
LEX::sql_command member (as it became part of
Query_tables_list class) we have to restore value of this
member when this method is called by mysql_admin_table(),
to make this code safe for re-execution.
sql/sql_trigger.cc:
Since LEX::reset_n_backup_query_tables_list() now also
resets LEX::sql_command member (as it became part of
Query_tables_list class) we have to restore it in cases
when while working with proxy Query_table_list we assume
that LEX::sql_command still corresponds to original SQL
command being executed (for example, when we are logging
statement to the binary log while having Query_tables_list
reset and backed up).
sql/sql_update.cc:
Function read_lock_type_for_table() now takes pointers
to Query_tables_list 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_yacc.yy:
- Removed st_select_lex::lock_option member as there is no
real need for per-SELECT lock type (HIGH_PRIORITY option
should apply to the whole statement. FOR UPDATE/LOCK IN
SHARE MODE clauses can be handled without this member).
The main effect which was achieved by introduction of this
member, i.e. using TL_READ_DEFAULT lock type for
subqueries, is now achieved by setting LEX::lock_option
(or rather its replacement - Yacc_state::m_lock_type) to
TL_READ_DEFAULT in almost all cases.
- Replaced LEX::lock_option with Yacc_state::m_lock_type
in order to emphasize that this value is relevant only
during parsing. Unlike for LEX::lock_option the default
value for Yacc_state::m_lock_type is TL_READ_DEFAULT.
Note that for cases when it is OK to take a "weak" read
lock (e.g. simple SELECT) this lock type will be converted
to TL_READ at open_tables() time. So this change won't
cause negative change in behavior for such statements.
OTOH this change ensures that, for example, for SELECTs
which are used in stored functions TL_READ_NO_INSERT lock
is taken when necessary and as result calls to such stored
functions can be written to the binary log with correct
serialization.
- To be able more easily distinguish high-priority SELECTs
in st_select_lex::print() method we now use new flag
in st_select_lex::options bit-field.
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