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mariadb/mysql-test/r/flush.result
Dmitry Lenev 00496b7acd Fix for bug #52044 "FLUSH TABLES WITH READ LOCK and FLUSH 
TABLES <list> WITH READ LOCK are incompatible".

The problem was that FLUSH TABLES <list> WITH READ LOCK
which was issued when other connection has acquired global
read lock using FLUSH TABLES WITH READ LOCK was blocked
and has to wait until global read lock is released.

This issue stemmed from the fact that FLUSH TABLES <list>
WITH READ LOCK implementation has acquired X metadata locks
on tables to be flushed. Since these locks required acquiring
of global IX lock this statement was incompatible with global
read lock.

This patch addresses problem by using SNW metadata type of
lock for tables to be flushed by FLUSH TABLES <list> WITH
READ LOCK. It is OK to acquire them without global IX lock
as long as we won't try to upgrade those locks. Since SNW
locks allow concurrent statements using same table FLUSH
TABLE <list> WITH READ LOCK now has to wait until old
versions of tables to be flushed go away after acquiring
metadata locks. Since such waiting can lead to deadlock
MDL deadlock detector was extended to take into account
waits for flush and resolve such deadlocks.

As a bonus code in open_tables() which was responsible for
waiting old versions of tables to go away was refactored.
Now when we encounter old version of table in open_table()
we don't back-off and wait for all old version to go away,
but instead wait for this particular table to be flushed.
Such approach supported by deadlock detection should reduce
number of scenarios in which FLUSH TABLES aborts concurrent
multi-statement transactions.

Note that active FLUSH TABLES <list> WITH READ LOCK still
blocks concurrent FLUSH TABLES WITH READ LOCK statement
as the former keeps tables open and thus prevents the
latter statement from doing flush.

mysql-test/include/handler.inc:
  Adjusted test case after changing status which is set
  when FLUSH TABLES waits for tables to be flushed from
  "Flushing tables" to "Waiting for table".
mysql-test/r/flush.result:
  Added test which checks that "flush tables <list> with
  read lock" is compatible with active "flush tables with
  read lock" but not vice-versa. This test also covers
  bug #52044 "FLUSH TABLES WITH READ LOCK and FLUSH TABLES
  <list> WITH READ LOCK are incompatible".
mysql-test/r/mdl_sync.result:
  Added scenarios in which wait for table to be flushed
  causes deadlocks to the coverage of MDL deadlock detector.
mysql-test/suite/perfschema/r/dml_setup_instruments.result:
  Adjusted test results after removal of COND_refresh
  condition variable.
mysql-test/suite/perfschema/r/server_init.result:
  Adjusted test and its results after removal of COND_refresh
  condition variable.
mysql-test/suite/perfschema/t/server_init.test:
  Adjusted test and its results after removal of COND_refresh
  condition variable.
mysql-test/t/flush.test:
  Added test which checks that "flush tables <list> with
  read lock" is compatible with active "flush tables with
  read lock" but not vice-versa. This test also covers
  bug #52044 "FLUSH TABLES WITH READ LOCK and FLUSH TABLES
  <list> WITH READ LOCK are incompatible".
mysql-test/t/kill.test:
  Adjusted test case after changing status which is set
  when FLUSH TABLES waits for tables to be flushed from
  "Flushing tables" to "Waiting for table".
mysql-test/t/lock_multi.test:
  Adjusted test case after changing status which is set
  when FLUSH TABLES waits for tables to be flushed from
  "Flushing tables" to "Waiting for table".
mysql-test/t/mdl_sync.test:
  Added scenarios in which wait for table to be flushed
  causes deadlocks to the coverage of MDL deadlock detector.
sql/ha_ndbcluster.cc:
  Adjusted code after adding one more parameter for
  close_cached_tables() call - timeout for waiting for
  table to be flushed.
sql/ha_ndbcluster_binlog.cc:
  Adjusted code after adding one more parameter for
  close_cached_tables() call - timeout for waiting for
  table to be flushed.
sql/lock.cc:
  Removed COND_refresh condition variable. See comment
  for sql_base.cc for details.
sql/mdl.cc:
  Now MDL deadlock detector takes into account information
  about waits for table flushes when searching for deadlock.
  To implement this change:
  - Declaration of enum_deadlock_weight and
    Deadlock_detection_visitor were moved to mdl.h header
    to make them available to the code in table.cc which
    implements deadlock detector traversal through edges
    of waiters graph representing waiting for flush.
  - Since now MDL_context may wait not only for metadata
    lock but also for table to be flushed an abstract
    Wait_for_edge class was introduced. Its descendants
    MDL_ticket and Flush_ticket incapsulate specifics
    of inspecting waiters graph when following through
    edge representing wait of particular type.
  
  We no longer require global IX metadata lock when acquiring
  SNW or SNRW locks. Such locks are needed only when metadata
  locks of these types are upgraded to X locks. This allows
  to use SNW locks in FLUSH TABLES <list> WITH READ LOCK
  implementation and keep the latter compatible with global
  read lock.
sql/mdl.h:
  Now MDL deadlock detector takes into account information
  about waits for table flushes when searching for deadlock.
  To implement this change:
  - Declaration of enum_deadlock_weight and
    Deadlock_detection_visitor were moved to mdl.h header
    to make them available to the code in table.cc which
    implements deadlock detector traversal through edges
    of waiters graph representing waiting for flush.
  - Since now MDL_context may wait not only for metadata
    lock but also for table to be flushed an abstract
    Wait_for_edge class was introduced. Its descendants
    MDL_ticket and Flush_ticket incapsulate specifics
    of inspecting waiters graph when following through
    edge representing wait of particular type.
  - Deadlock_detection_visitor now has m_table_shares_visited
    member which allows to support recursive locking for
    LOCK_open. This is required when deadlock detector
    inspects waiters graph which contains several edges
    representing waits for flushes or needs to come through
    the such edge more than once.
sql/mysqld.cc:
  Removed COND_refresh condition variable. See comment
  for sql_base.cc for details.
sql/mysqld.h:
  Removed COND_refresh condition variable. See comment
  for sql_base.cc for details.
sql/sql_base.cc:
  Changed approach to how threads are waiting for table
  to be flushed. Now thread that wants to wait for old
  table to go away subscribes for notification by adding
  Flush_ticket to table's share and waits using
  MDL_context::m_wait object. Once table gets flushed
  (i.e. all tables are closed and table share is ready
  to be destroyed) all such waiters are notified
  individually.
  Thanks to this change MDL deadlock detector can take
  such waits into account.
  
  To implement this/as result of this change:
  - tdc_wait_for_old_versions() was replaced with
    tdc_wait_for_old_version() which waits for individual
    old share to go away and which is called by open_table()
    after finding out that share is outdated. We don't
    need to perform back-off before such waiting thanks
    to the fact that deadlock detector now sees such waits.
  - As result Open_table_ctx::m_mdl_requests became
    unnecessary and was removed. We no longer allocate
    copies of MDL_request objects on MEM_ROOT when
    MYSQL_OPEN_FORCE_SHARED/SHARED_HIGH_PRIO flags are
    in effect.
  - close_cached_tables() and tdc_wait_for_old_version()
    share code which implements waiting for share to be
    flushed - the both use TABLE_SHARE::wait_until_flush()
    method. Thanks to this close_cached_tables() supports
    timeouts and has extra parameter for this.
  - Open_table_context::OT_MDL_CONFLICT enum element was
    renamed to OT_CONFLICT as it is now also used in cases
    when back-off is required to resolve deadlock caused
    by waiting for flush and not metadata lock.
  - In cases when we discover that current connection tries
    to open tables from different generation we now simply
    back-off and restart process of opening tables. To
    support this Open_table_context::OT_REOPEN_TABLES enum
    element was added.
  - COND_refresh condition variable became unnecessary and
    was removed.
  - mysql_notify_thread_having_shared_lock() no longer wakes
    up connections waiting for flush as all such connections
    can be waken up by deadlock detector if necessary.
sql/sql_base.h:
  - close_cached_tables() now has one more parameter -
    timeout for waiting for table to be flushed.
  - Open_table_context::OT_MDL_CONFLICT enum element was
    renamed to OT_CONFLICT as it is now also used in cases
    when back-off is required to resolve deadlock caused
    by waiting for flush and not metadata lock.
    Added new OT_REOPEN_TABLES enum element to be used in
    cases when we need to restart open tables process even
    in the middle of transaction.
  - Open_table_ctx::m_mdl_requests became unnecessary and
    was removed.
sql/sql_class.h:
  Added assert ensuring that we won't use LOCK_open mutex
  with THD::enter_cond(). Otherwise deadlocks can arise in
  MDL deadlock detector.
sql/sql_parse.cc:
  Changed FLUSH TABLES <list> WITH READ LOCK to take SNW
  metadata locks instead of X locks on tables to be flushed.
  Since we no longer require global IX lock to be taken
  when SNW locks are taken this makes this statement
  compatible with FLUSH TABLES WITH READ LOCK statement.
  Since SNW locks allow other connections to have table
  opened FLUSH TABLES <list> WITH READ LOCK now has to
  wait during open_tables() for old version to go away.
  Such waits can lead to deadlocks which will be detected
  by MDL deadlock detector which now takes waits for table
  to be flushed into account.
  
  Also adjusted code after adding one more parameter for
  close_cached_tables() call - timeout for waiting for
  table to be flushed.
sql/sql_yacc.yy:
  FLUSH TABLES <list> WITH READ LOCK now needs only SNW
  metadata locks on tables.
sql/sys_vars.cc:
  Adjusted code after adding one more parameter for
  close_cached_tables() call - timeout for waiting for
  table to be flushed.
sql/table.cc:
  Implemented new approach to how threads are waiting for
  table to be flushed. Now thread that wants to wait for
  old table to go away subscribes for notification by
  adding Flush_ticket to table's share and waits using
  MDL_context::m_wait object. Once table gets flushed
  (i.e. all tables are closed and table share is ready
  to be destroyed) all such waiters are notified
  individually. This change allows to make such waits
  visible inside of MDL deadlock detector.
  To do it:
  
  - Added list of waiters/Flush_tickets to TABLE_SHARE
    class.
  - Changed free_table_share() to postpone freeing of
    share memory until last waiter goes away and to
    wake up subscribed waiters.
  - Added TABLE_SHARE::wait_until_flushed() method which
    implements subscription to the list of waiters for
    table to be flushed and waiting for this event.
  
  Implemented interface which allows to expose waits for
  flushes to MDL deadlock detector:
  
  - Introduced Flush_ticket class a descendant of
    Wait_for_edge class.
  - Added TABLE_SHARE::find_deadlock() method which allows
    deadlock detector to find out what contexts are still
    using old version of table in question (i.e. to find
    out what contexts are waited for by owner of
    Flush_ticket).
sql/table.h:
  In order to support new strategy of waiting for table flush
  (see comment for table.cc for details) added list of
  waiters/Flush_tickets to TABLE_SHARE class.
  
  Implemented interface which allows to expose waits for
  flushes to MDL deadlock detector:
  - Introduced Flush_ticket class a descendant of
    Wait_for_edge class.
  - Added TABLE_SHARE::find_deadlock() method which allows
    deadlock detector to find out what contexts are still
    using old version of table in question (i.e. to find
    out what contexts are waited for by owner of
    Flush_ticket).
2010-07-27 17:34:58 +04:00

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drop table if exists t1,t2;
drop database if exists mysqltest;
create temporary table t1(n int not null primary key);
create table t2(n int);
insert into t2 values(3);
select * from t1;
n
3
flush tables with read lock;
drop table t2;
ERROR HY000: Can't execute the query because you have a conflicting read lock
drop table t2;
unlock tables;
create database mysqltest;
create table mysqltest.t1(n int);
insert into mysqltest.t1 values (23);
flush tables with read lock;
drop database mysqltest;
select * from mysqltest.t1;
n
23
unlock tables;
create table t1 (n int);
flush tables with read lock;
insert into t1 values (345);
select * from t1;
n
345
drop table t1;
create table t1 (c1 int);
lock table t1 write;
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
lock table t1 read;
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
unlock tables;
flush tables with read lock;
lock table t1 write;
ERROR HY000: Can't execute the query because you have a conflicting read lock
lock table t1 read;
lock table t1 write;
ERROR HY000: Can't execute the query because you have a conflicting read lock
unlock tables;
create table t2 (c1 int);
create table t3 (c1 int);
lock table t1 read, t2 read, t3 write;
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
lock table t1 read, t2 read, t3 read;
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
unlock tables;
drop table t1, t2, t3;
create table t1 (c1 int);
create table t2 (c1 int);
lock table t1 write;
flush tables with read lock;
insert into t2 values(1);
unlock tables;
drop table t1, t2;
drop table if exists t1, t2;
set session low_priority_updates=1;
create table t1 (a int);
create table t2 (b int);
lock tables t1 write;
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
unlock tables;
lock tables t1 read, t2 write;
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
unlock tables;
lock tables t1 read;
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
unlock tables;
drop table t1, t2;
set session low_priority_updates=default;
select benchmark(200, (select sin(1))) > 1000;
End of 5.0 tests
set @old_general_log= @@general_log;
set @old_read_only= @@read_only;
set global general_log= on;
flush tables with read lock;
flush logs;
unlock tables;
set global read_only=1;
flush logs;
unlock tables;
flush tables with read lock;
flush logs;
unlock tables;
set global general_log= @old_general_log;
set global read_only= @old_read_only;
End of 5.1 tests
#
# Additional test for bug #51136 "Crash in pthread_rwlock_rdlock
# on TEMPORARY + HANDLER + LOCK + SP".
# Also see the main test for this bug in include/handler.inc.
#
drop tables if exists t1, t2;
create table t1 (i int);
create temporary table t2 (j int);
flush tables with read lock;
lock table t2 read;
# This commit should not release any MDL locks.
commit;
# The below statement crashed before the bug fix as it
# has attempted to release global shared metadata lock
# which was already released by commit.
unlock tables;
drop tables t1, t2;
#
# Tests for WL#5000 FLUSH TABLES|TABLE table_list WITH READ LOCK
#
# I. Check the incompatible changes in the grammar.
#
flush tables with read lock, hosts;
ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' hosts' at line 1
flush privileges, tables;
ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tables' at line 1
flush privileges, tables with read lock;
ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tables with read lock' at line 1
flush privileges, tables;
ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tables' at line 1
flush tables with read lock, tables;
ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' tables' at line 1
show tables;
Tables_in_test
#
# II. Check the allowed syntax.
#
drop table if exists t1, t2, t3;
create table t1 (a int);
create table t2 (a int);
create table t3 (a int);
lock table t1 read, t2 read;
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
unlock tables;
flush tables with read lock;
flush tables t1, t2 with read lock;
flush tables t1, t2 with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
flush tables with read lock;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
select * from t1;
a
select * from t2;
a
select * from t3;
ERROR HY000: Table 't3' was not locked with LOCK TABLES
insert into t1 (a) values (1);
ERROR HY000: Table 't1' was locked with a READ lock and can't be updated
insert into t2 (a) values (1);
ERROR HY000: Table 't2' was locked with a READ lock and can't be updated
insert into t3 (a) values (1);
ERROR HY000: Table 't3' was not locked with LOCK TABLES
lock table no_such_table read;
ERROR 42S02: Table 'test.no_such_table' doesn't exist
#
# We implicitly left the locked tables
# mode but still have the read lock.
#
insert into t2 (a) values (1);
ERROR HY000: Can't execute the query because you have a conflicting read lock
unlock tables;
insert into t1 (a) values (1);
insert into t2 (a) values (1);
flush table t1, t2 with read lock;
select * from t1;
a
1
select * from t2;
a
1
select * from t3;
ERROR HY000: Table 't3' was not locked with LOCK TABLES
insert into t1 (a) values (2);
ERROR HY000: Table 't1' was locked with a READ lock and can't be updated
insert into t2 (a) values (2);
ERROR HY000: Table 't2' was locked with a READ lock and can't be updated
insert into t3 (a) values (2);
ERROR HY000: Table 't3' was not locked with LOCK TABLES
lock table no_such_table read;
ERROR 42S02: Table 'test.no_such_table' doesn't exist
insert into t3 (a) values (2);
#
# III. Concurrent tests.
#
# --> connection default
#
# Check that flush tables <list> with read lock
# does not affect non-locked tables.
#
flush tables t1 with read lock;
# --> connection con1;
select * from t1;
a
1
select * from t2;
a
1
insert into t2 (a) values (3);
# --> connection default;
unlock tables;
#
# Check that "flush tables <list> with read lock" is
# compatible with active "flush tables with read lock".
# Vice versa is not true as tables read-locked by
# "flush tables <list> with read lock" can't be flushed.
flush tables with read lock;
# --> connection con1;
flush table t1 with read lock;
select * from t1;
a
1
unlock tables;
# --> connection default;
unlock tables;
# --> connection con1
drop table t1, t2, t3;
#
# Bug#51710 FLUSH TABLES <view> WITH READ LOCK kills the server
#
drop view if exists v1, v2, v3;
drop table if exists t1, v1;
create table t1 (a int);
create view v1 as select 1;
create view v2 as select * from t1;
create view v3 as select * from v2;
flush table v1, v2, v3 with read lock;
ERROR HY000: 'test.v1' is not BASE TABLE
flush table v1 with read lock;
ERROR HY000: 'test.v1' is not BASE TABLE
flush table v2 with read lock;
ERROR HY000: 'test.v2' is not BASE TABLE
flush table v3 with read lock;
ERROR HY000: 'test.v3' is not BASE TABLE
create temporary table v1 (a int);
flush table v1 with read lock;
ERROR HY000: 'test.v1' is not BASE TABLE
drop view v1;
create table v1 (a int);
flush table v1 with read lock;
drop temporary table v1;
unlock tables;
drop view v2, v3;
drop table t1, v1;
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