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mariadb/mysql-test/r/flush.result
Dmitry Lenev 378cdc58c1 Patch that refactors global read lock implementation and fixes 
bug #57006 "Deadlock between HANDLER and FLUSH TABLES WITH READ
LOCK" and bug #54673 "It takes too long to get readlock for
'FLUSH TABLES WITH READ LOCK'".

The first bug manifested itself as a deadlock which occurred
when a connection, which had some table open through HANDLER
statement, tried to update some data through DML statement
while another connection tried to execute FLUSH TABLES WITH
READ LOCK concurrently.

What happened was that FTWRL in the second connection managed
to perform first step of GRL acquisition and thus blocked all
upcoming DML. After that it started to wait for table open
through HANDLER statement to be flushed. When the first connection
tried to execute DML it has started to wait for GRL/the second
connection creating deadlock.

The second bug manifested itself as starvation of FLUSH TABLES
WITH READ LOCK statements in cases when there was a constant
stream of concurrent DML statements (in two or more
connections).

This has happened because requests for protection against GRL
which were acquired by DML statements were ignoring presence of
pending GRL and thus the latter was starved.

This patch solves both these problems by re-implementing GRL
using metadata locks.

Similar to the old implementation acquisition of GRL in new
implementation is two-step. During the first step we block
all concurrent DML and DDL statements by acquiring global S
metadata lock (each DML and DDL statement acquires global IX
lock for its duration). During the second step we block commits
by acquiring global S lock in COMMIT namespace (commit code
acquires global IX lock in this namespace).

Note that unlike in old implementation acquisition of
protection against GRL in DML and DDL is semi-automatic.
We assume that any statement which should be blocked by GRL
will either open and acquires write-lock on tables or acquires
metadata locks on objects it is going to modify. For any such
statement global IX metadata lock is automatically acquired
for its duration.

The first problem is solved because waits for GRL become
visible to deadlock detector in metadata locking subsystem
and thus deadlocks like one in the first bug become impossible.

The second problem is solved because global S locks which
are used for GRL implementation are given preference over
IX locks which are acquired by concurrent DML (and we can
switch to fair scheduling in future if needed).

Important change:
FTWRL/GRL no longer blocks DML and DDL on temporary tables.
Before this patch behavior was not consistent in this respect:
in some cases DML/DDL statements on temporary tables were
blocked while in others they were not. Since the main use cases
for FTWRL are various forms of backups and temporary tables are
not preserved during backups we have opted for consistently
allowing DML/DDL on temporary tables during FTWRL/GRL.

Important change:
This patch changes thread state names which are used when
DML/DDL of FTWRL is waiting for global read lock. It is now
either "Waiting for global read lock" or "Waiting for commit
lock" depending on the stage on which FTWRL is.

Incompatible change:
To solve deadlock in events code which was exposed by this
patch we have to replace LOCK_event_metadata mutex with
metadata locks on events. As result we have to prohibit
DDL on events under LOCK TABLES.

This patch also adds extensive test coverage for interaction
of DML/DDL and FTWRL.

Performance of new and old global read lock implementations
in sysbench tests were compared. There were no significant
difference between new and old implementations.
2010-11-11 20:11:05 +03:00

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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 it is not true, since 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;
#
# Check that FLUSH TABLES t1 WITH READ LOCK
# does not conflict with an existing FLUSH TABLES t2
# WITH READ LOCK.
#
flush table t1 with read lock;
# --> connection con1
flush table t2 with read lock;
unlock tables;
# --> connection default
unlock tables;
#
# Check that FLUSH TABLES t1 WITH READ LOCK
# does not conflict with SET GLOBAL read_only=1.
#
set global read_only=1;
# connection con1
flush table t1 with read lock;
unlock tables;
# connection default
set global read_only=0;
#
# Check that it's possible to read-lock
# tables locked with FLUSH TABLE <list> WITH READ LOCK.
#
flush tables t1, t2 with read lock;
# connection con1
lock table t1 read, t2 read;
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;
#
# FLUSH TABLES <list> WITH READ LOCK and HANDLER
#
drop table if exists t1;
create table t1 (a int, key a (a));
insert into t1 (a) values (1), (2), (3);
handler t1 open;
handler t1 read a next;
a
1
handler t1 read a next;
a
2
flush tables t1 with read lock;
handler t1 read a next;
ERROR HY000: Can't execute the given command because you have active locked tables or an active transaction
unlock tables;
#
# Sic: lost handler position.
#
handler t1 read a next;
a
1
handler t1 close;
drop table t1;
#
# Bug#52117 Pending FLUSH TALBES <list> aborts
# transactions unnecessarily.
#
drop table if exists t1;
# --> conection default
create table t1 (a int);
begin;
select * from t1;
a
# --> connection con1
#
# Issue a LOCK TABLE t1 READ. We could use HANDLER t1 OPEN
# or a long-running select -- anything that
# prevents FLUSH TABLE t1 from immediate completion would do.
#
lock table t1 read;
# --> connection con2
#
# FLUSH TABLE expels the table definition from the cache.
# Sending 'flush table t1'...
flush table t1;
# --> connection default
# Let flush table sync in.
select * from t1;
# --> connection con1
select * from t1;
a
unlock tables;
# --> connection con2
# Reaping 'flush table t1'...
# --> connection default
# Reaping 'select * from t1'...
a
commit;
#
# Repeat the same test but with FLUSH TABLES
#
begin;
select * from t1;
a
# --> connection con1
#
# Issue a LOCK TABLE t1 READ.
#
lock table t1 read;
# --> connection con2
#
# FLUSH TABLES expels the table definition from the cache.
# Sending 'flush tables'...
flush tables;
# --> connection default
# Let flush table sync in.
select * from t1;
# --> connection con1
select * from t1;
a
unlock tables;
# --> connection con2
# Reaping 'flush tables'...
# --> connection default
# Reaping 'select * from t1'...
a
commit;
# Cleanup
# --> connection con1
# --> connection con2
# --> connection default
drop table t1;
#
# Test for bug #55273 "FLUSH TABLE tm WITH READ LOCK for Merge table
# causes assert failure".
#
drop table if exists t1, t2, tm;
create table t1 (i int);
create table t2 (i int);
create table tm (i int) engine=merge union=(t1, t2);
insert into t1 values (1), (2);
insert into t2 values (3), (4);
# The below statement should succeed and lock merge
# table for read. Only merge table gets flushed and
# not underlying tables.
flush tables tm with read lock;
select * from tm;
i
1
2
3
4
# Check that underlying tables are locked.
select * from t1;
i
1
2
select * from t2;
i
3
4
unlock tables;
# This statement should succeed as well and flush
# all tables in the list.
flush tables tm, t1, t2 with read lock;
select * from tm;
i
1
2
3
4
# Naturally, underlying tables should be locked in this case too.
select * from t1;
i
1
2
select * from t2;
i
3
4
unlock tables;
drop tables tm, t1, t2;
#
# Test for bug #57006 "Deadlock between HANDLER and
# FLUSH TABLES WITH READ LOCK".
#
drop table if exists t1, t2;
create table t1 (i int);
create table t2 (i int);
handler t1 open;
# Switching to connection 'con1'.
# Sending:
flush tables with read lock;
# Switching to connection 'con2'.
# Wait until FTWRL starts waiting for 't1' to be closed.
# Switching to connection 'default'.
# The below statement should not cause deadlock.
# Sending:
insert into t2 values (1);
# Switching to connection 'con2'.
# Wait until INSERT starts to wait for FTWRL to go away.
# Switching to connection 'con1'.
# FTWRL should be able to continue now.
# Reap FTWRL.
unlock tables;
# Switching to connection 'default'.
# Reap INSERT.
handler t1 close;
# Cleanup.
drop tables t1, t2;
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