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mariadb/mysql-test/r/flush.result
Dmitry Lenev 5b225518ff Fix for bug #12641342 - "61401: UPDATE PERFORMANCE DEGRADES 
GRADUALLY IF A TRIGGER EXISTS".

This bug manifested itself in two ways:

- Firstly execution of any data-changing statement which
  required prelocking (i.e. involved stored function or
  trigger) as part of transaction slowed down a bit all
  subsequent statements in this transaction. So performance
  in transaction which periodically involved such statements
  gradually degraded over time.
- Secondly execution of any data-changing statement which
  required prelocking as part of transaction prevented
  concurrent FLUSH TABLES WITH READ LOCK from proceeding
  until the end of transaction instead of end of particular
  statement.
  
The problem was caused by incorrect handling of metadata lock
used in FTWRL implementation for statements requiring prelocked 
mode. 
Each statement which changes data acquires global IX lock
with STATEMENT duration. This lock is supposed to block 
concurrent FTWRL from proceeding until the statement ends.

When entering prelocked mode, durations of all metadata locks
acquired so far were changed to EXPLICIT, to prevent 
substatements from releasing these locks. When prelocked mode
was left, durations of metadata locks were changed to
TRANSACTIONAL (with a few exceptions) so they can be properly
released at the end of transaction. 
Unfortunately, this meant that the global IX lock blocking
FTWRL with STATEMENT duration was moved to TRANSACTIONAL
duration after execution of statement requiring prelocking.

Since each subsequent statement that required prelocking and
tried to acquire global IX lock with STATEMENT duration got
a new instance of MDL_ticket, which was later moved to
TRANSACTIONAL duration, this led to unwarranted growth of
number of tickets with TRANSACITONAL duration in this
connection's MDL_context. As result searching for other
tickets in it became slow and acquisition of other metadata
locks by this transaction started to hog CPU.

Moreover, this also meant that after execution of statement
requiring prelocking concurrent FTWRL was blocked
until the end of transaction instead of end of statement.

This patch solves this problem by not moving locks to EXPLICIT
duration when thread enters prelocked mode (unless it is a real 
LOCK TABLES mode). This step turned out to be not really 
necessary as substatements don't try to release metadata locks.
Consequently, the global IX lock blocking FTWRL keeps its
STATEMENT duration and is properly released at the end of
statement and the above issue goes away.

mysql-test/r/flush.result:
  Added test for bug #12641342 - "61401: UPDATE PERFORMANCE
  DEGRADES GRADUALLY IF A TRIGGER EXISTS".
mysql-test/t/flush.test:
  Added test for bug #12641342 - "61401: UPDATE PERFORMANCE
  DEGRADES GRADUALLY IF A TRIGGER EXISTS".
sql/mdl.h:
  Added comment describing various types of metadata lock
  duration.
sql/sql_class.cc:
  Since we no longer change duration of metadata locks to EXPLICIT
  when entering prelocked mode (unless it is a real LOCK TABLES)
  there is no need to restore proper duration of the locks when
  leaving prelocked mode.
sql/sql_class.h:
  Do not change duration of metadata locks to EXPLICIT when
  entering prelocking mode (unless it is a real LOCK TABLES).
  This allows to avoid problems with restoring correct duration
  when leaving this mode. It is possible to do this as
  substatements won't release metadata locks in any case.
sql/sql_parse.cc:
  Added assert checking that we won't release metadata locks
  when in substatement.
2011-06-16 19:18:16 +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 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;
#
# Bug#57649 FLUSH TABLES under FLUSH TABLES <list> WITH READ LOCK leads
# to assert failure.
#
DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (a INT);
FLUSH TABLES t1 WITH READ LOCK;
FLUSH TABLES;
ERROR HY000: Table 't1' was locked with a READ lock and can't be updated
CREATE TRIGGER t1_bi BEFORE INSERT ON t1 FOR EACH ROW SET @a= 1;
ERROR HY000: Table 't1' was locked with a READ lock and can't be updated
ALTER TABLE t1 COMMENT 'test';
ERROR HY000: Table 't1' was locked with a READ lock and can't be updated
UNLOCK TABLES;
DROP TABLE t1;
#
# Test for bug #12641342 - "61401: UPDATE PERFORMANCE DEGRADES
# GRADUALLY IF A TRIGGER EXISTS".
#
# One of side-effects of this bug was that a transaction which
# involved DML statements requiring prelocking blocked concurrent
# FLUSH TABLES WITH READ LOCK for the whole its duration, while
# correct behavior in this case is to block FTWRL only for duration
# of individual DML statements.
DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (id INT PRIMARY KEY, value INT);
INSERT INTO t1 VALUES (1, 1);
CREATE TRIGGER t1_au AFTER UPDATE ON t1 FOR EACH ROW SET @var = "a";
BEGIN;
UPDATE t1 SET value= value + 1 WHERE id = 1;
# Switching to connection 'con1'.
# The below FLUSH TABLES WITH READ LOCK should succeed and
# should not be blocked by the transaction in default connection.
FLUSH TABLES WITH READ LOCK;
UNLOCK TABLES;
# Switching to connection 'default'.
COMMIT;
DROP TABLE t1;
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