Posts Tagged ‘MySQL’

What is FTS_BEING_DELETED.ibd

Wednesday, January 29th, 2014

I currently have on a MySQL 5.6 database using innodb_file_per_table the following individual tablespace file.

schema/FTS_00000000000001bb_BEING_DELETED.ibd

The schema is all InnoDB tables, and there ARE NO Full Text Indexes. I cannot comment on if a developer has tried to create one previously.
I am none the wiser in explaining the ongoing use of these files, or if it can be/should be deleted.

On closer inspection there are infact a number of FTS files.

$ ls -al FTS*
-rw-r----- 1 mysql mysql 98304 Jan 29 16:21 FTS_00000000000001bb_BEING_DELETED_CACHE.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:20 FTS_00000000000001bb_BEING_DELETED.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:26 FTS_00000000000001bb_CONFIG.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:21 FTS_00000000000001bb_DELETED_CACHE.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:00 FTS_00000000000001bb_DELETED.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:20 FTS_00000000000001c7_BEING_DELETED_CACHE.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:26 FTS_00000000000001c7_BEING_DELETED.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:21 FTS_00000000000001c7_CONFIG.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:20 FTS_00000000000001c7_DELETED_CACHE.ibd
-rw-r----- 1 mysql mysql 98304 Jan 29 16:20 FTS_00000000000001c7_DELETED.ibd

Any MySQL gurus with knowledge to share, and for the benefit of others that Internet search at a later time.

Related articles included Overview and Getting Started with InnoDB FTS and Difference between InnoDB FTS and MyISAM FTS but do not mention file specifics.

The article InnoDB Full-text Search in MySQL 5.6 (part 1) provides more insight that these files remain even if a full text index was created and has since being removed. It is not clear from the filename which tables these files relate to.

What SQL is running in MySQL

Monday, November 11th, 2013

Using the MySQL 5.6 Performance Schema it is very easy to see what is actually running on your MySQL instance. No more sampling or installing software or worrying about disk I/O performance with techniques like SHOW PROCESSLIST, enabling the general query log or sniffing the TCP/IP stack.

The following SQL is used to give me a quick 60 second view on a running MySQL system of ALL statements executed.

use performance_schema;
update setup_consumers set enabled='YES' where name IN ('events_statements_history','events_statements_current','statements_digest');
truncate table events_statements_current; truncate table events_statements_history; truncate table events_statements_summary_by_digest;
do sleep(60);
select now(),(count_star/(select sum(count_star) FROM events_statements_summary_by_digest) * 100) as pct, count_star, left(digest_text,150) as stmt, digest from events_statements_summary_by_digest order by 2 desc;
update setup_consumers set enabled='NO' where name IN ('events_statements_history','events_statements_current','statements_digest');

NOTE: These statements are for simple debugging and demonstration purposes. If you want to monitor SQL statements on an ongoing basis, you should not simply truncate tables and globally enable/disable options.

There are four performance schema tables that are applicable for looking at initial SQL analysis.

  1. The events_statements_summary_by_digest table shown below gives as the name suggests a way to summarize all queries into a common query pattern (or digest). This is great to get a picture of volume and frequency of SQL statements.
  2. The events_statements_current shows the currently running SQL statements
  3. The events_statements_history shows the fun, because it provides a *short, default 10 threads* history of the SQL statements that have run in any given thread.
  4. The events_statements_history_long (when enabled) gives you a history of the most recent 10,000 events.

One query can give me a detailed review of the type and frequency of ALL SQL statements run. The ALL is important, because on a slave you also get ALL replication applied events.

mysql> select now(),(count_star/(select sum(count_star) FROM events_statements_summary_by_digest) * 100) as pct, count_star, left(digest_text,150) as stmt, digest from events_statements_summary_by_digest order by 2 desc;
select * from events_statements_current where digest='ffb6231b78efc022175650d37a837b99'\G
+---------------------+---------+------------+--------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+
| now()               | pct     | count_star | stmt                                                                                                                                                   | digest                           |
+---------------------+---------+------------+--------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+
| 2013-11-07 18:24:46 | 60.6585 |       7185 | SELECT * FROM `D.....` WHERE `name` = ?                                                                                                                | d6399273d75e2348d6d7ea872489a30c |
| 2013-11-07 18:24:46 | 23.4192 |       2774 | SELECT nc . id , nc . name FROM A.................. anc JOIN N........... nc ON anc . ............_id = nc . id WHERE ......._id = ?                   | c6e2249eb91767aa09945cbb118adbb3 |
| 2013-11-07 18:24:46 |  5.5298 |        655 | BEGIN                                                                                                                                                  | 7519b14a899fd514365211a895f5e833 |
| 2013-11-07 18:24:46 |  4.6180 |        547 | INSERT INTO V........ VALUES (...) ON DUPLICATE KEY UPDATE v.... = v.... + ?                                                                           | ffb6231b78efc022175650d37a837b99 |
| 2013-11-07 18:24:46 |  1.0891 |        129 | SELECT COUNT ( * ) FROM T............... WHERE rule = ? AND ? LIKE concat ( pattern , ? )                                                              | 22d984df583adc9a1ac282239e7629e2 |
| 2013-11-07 18:24:46 |  1.0553 |        125 | SELECT COUNT ( * ) FROM T............... WHERE rule = ? AND ? LIKE concat ( ? , pattern , ? )                                                          | a8ee43287bb2ee35e2c144c569a8b2de |
| 2013-11-07 18:24:46 |  0.9033 |        107 | INSERT IGNORE INTO `K......` ( `id` , `k......` ) VALUES (...)                                                                                         | 675e32e9eac555f33df240e80305c013 |
| 2013-11-07 18:24:46 |  0.7936 |         94 | SELECT * FROM `K......` WHERE k...... IN (...)                                                                                                         | 8aa7dc3b6f729aec61bd8d7dfa5978fa |
| 2013-11-07 18:24:46 |  0.4559 |         54 | SELECT COUNT ( * ) FROM D..... WHERE NAME = ? OR NAME = ?                                                                                              | 1975f53832b0c2506de482898cf1fd37 |
| 2013-11-07 18:24:46 |  0.3208 |         38 | SELECT h . * FROM H........ h LEFT JOIN H............ ht ON h . id = ht . ......_id WHERE ht . ........._id = ? ORDER BY h . level ASC                 | ca838db99e40fdeae920f7feae99d19f |
| 2013-11-07 18:24:46 |  0.2702 |         32 | SELECT h . * , ( POW ( ? * ( lat - - ? ) , ? ) + POW ( ? * ( ? - lon ) * COS ( lat / ? ) , ? ) ) AS distance FROM H........ h FORCE INDEX ( lat ) WHER | cd6e32fc0a20fab32662e2b0a282845c |
| 2013-11-07 18:24:46 |  0.1857 |         22 | SELECT h . * , ( POW ( ? * ( lat - ? ) , ? ) + POW ( ? * ( - ? - lon ) * COS ( lat / ? ) , ? ) ) AS distance FROM H........ h FORCE INDEX ( lat ) WHER | a7b43944f5811ef36c0ded7e79793536 |
| 2013-11-07 18:24:46 |  0.0760 |          9 | SELECT h . * , ( POW ( ? * ( lat - ? ) , ? ) + POW ( ? * ( ? - lon ) * COS ( lat / ? ) , ? ) ) AS distance FROM H........ h FORCE INDEX ( lat ) WHERE  | 4ccd8b28ae9e87a9c0b372a58ca22af7 |
| 2013-11-07 18:24:46 |  0.0169 |          2 | SELECT * FROM `K......` WHERE k...... IN (?)                                                                                                           | 44286e824d922d8e2ba6d993584844fb |
| 2013-11-07 18:24:46 |  0.0084 |          1 | SELECT h . * , ( POW ( ? * ( lat - - ? ) , ? ) + POW ( ? * ( - ? - lon ) * COS ( lat / ? ) , ? ) ) AS distance FROM H........ h FORCE INDEX ( lat ) WH | 299095227a67d99824af2ba012b81633 |
| 2013-11-07 18:24:46 |  0.0084 |          1 | SELECT * FROM `H........` WHERE `id` = ?                                                                                                               | 2924ea1d925a6e158397406403a63e3a |
| 2013-11-07 18:24:46 |  0.0084 |          1 | SHOW ENGINE INNODB STATUS                                                                                                                              | 0b04d3acd555401f1cbc479f920b1bac |
| 2013-11-07 18:24:46 |  0.0084 |          1 | DO `sleep` (?)                                                                                                                                         | 3d6e973c2657d0d136bbbdad05e68c7a |
| 2013-11-07 18:24:46 |  0.0084 |          1 | SHOW ENGINE INNODB MUTEX                                                                                                                               | a031f0e6068cb12c5b7508106687c2cb |
| 2013-11-07 18:24:46 |  0.0084 |          1 | SELECT NOW ( ) , ( `count_star` / ( SELECT SUM ( `count_star` ) FROM `events_statements_summary_by_digest` ) * ? ) AS `pct` , `count_star` , LEFT ( `d | 8a9e990cd85d6c42a2e537d04c8c5910 |
| 2013-11-07 18:24:46 |  0.0084 |          1 | SHOW SLAVE STATUS                                                                                                                                      | d2a0ffb1232f2704cef785f030306603 |
| 2013-11-07 18:24:46 |  0.0084 |          1 | TRUNCATE TABLE `events_statements_summary_by_digest`                                                                                                   | a7bef5367816ca771571e648ba963515 |
| 2013-11-07 18:24:46 |  0.0084 |          1 | UPDATE `setup_consumers` SET `enabled` = ? WHERE NAME IN (...)                                                                                         | 8205ea424267a604a3a4f68a76bc0bbb |
| 2013-11-07 18:24:46 |  0.0084 |          1 | SHOW GLOBAL STATUS                                                                                                                                     | ddf94d7d7b176021b8586a3cce1e85c9 |
+---------------------+---------+------------+--------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+

This immediately shows me a single simple application query that is executed 60% of the time. Further review of the data and usage pattern shows that should be cached. This is an immediate improvement on system scalability.

While you can look at the raw performance schema data, using ps_helper from Mark Leith makes live easier using the statement_analysis view because of normalizing timers into human readable formats (check out lock_latency).

mysql> select * from ps_helper.statement_analysis order by exec_count desc limit 10;
+-------------------------------------------------------------------+-----------+------------+-----------+------------+---------------+-------------+-------------+--------------+-----------+---------------+--------------+------------+-----------------+-------------+-------------------+----------------------------------+
| query                                                             | full_scan | exec_count | err_count | warn_count | total_latency | max_latency | avg_latency | lock_latency | rows_sent | rows_sent_avg | rows_scanned | tmp_tables | tmp_disk_tables | rows_sorted | sort_merge_passes | digest                           |
+-------------------------------------------------------------------+-----------+------------+-----------+------------+---------------+-------------+-------------+--------------+-----------+---------------+--------------+------------+-----------------+-------------+-------------------+----------------------------------+
| CREATE VIEW `io_by_thread_by_l ... SUM ( `sum_timer_wait` ) DESC  |           |     146117 |         0 |          0 | 00:01:47.36   | 765.11 ms   | 734.74 us   | 00:01:02.00  |         3 |             0 |            3 |          0 |               0 |           0 |                 0 | c877ec02dce17ea0aca2f256e5b9dc70 |
| SELECT nc . id , nc . name FRO ...  nc . id WHERE ......._id = ?  |           |      41394 |         0 |          0 | 16.85 s       | 718.37 ms   | 407.00 us   | 5.22 s       |    155639 |             4 |       312077 |          0 |               0 |           0 |                 0 | c6e2249eb91767aa09945cbb118adbb3 |
| BEGIN                                                             |           |      16281 |         0 |          0 | 223.24 ms     | 738.82 us   | 13.71 us    | 0 ps         |         0 |             0 |            0 |          0 |               0 |           0 |                 0 | 7519b14a899fd514365211a895f5e833 |
| INSERT INTO V........ VALUES ( ...  KEY UPDATE v.... = v.... + ?  |           |      12703 |         0 |          0 | 1.73 s        | 34.23 ms    | 136.54 us   | 696.50 ms    |         0 |             0 |            0 |          0 |               0 |           0 |                 0 | ffb6231b78efc022175650d37a837b99 |
| SELECT * FROM `D.....` WHERE `name` = ?                           |           |      10620 |         0 |          0 | 3.85 s        | 25.21 ms    | 362.52 us   | 705.16 ms    |         1 |             0 |            1 |          0 |               0 |           0 |                 0 | d6399273d75e2348d6d7ea872489a30c |
| SELECT COUNT ( * ) FROM T..... ... ? LIKE concat ( pattern , ? )  |           |       2830 |         0 |          0 | 1.22 s        | 2.14 ms     | 432.60 us   | 215.62 ms    |      2830 |             1 |       101880 |          0 |               0 |           0 |                 0 | 22d984df583adc9a1ac282239e7629e2 |
| SELECT COUNT ( * ) FROM T..... ... KE concat ( ? , pattern , ? )  |           |       2727 |         0 |          0 | 932.01 ms     | 30.95 ms    | 341.77 us   | 189.47 ms    |      2727 |             1 |        38178 |          0 |               0 |           0 |                 0 | a8ee43287bb2ee35e2c144c569a8b2de |
| INSERT IGNORE INTO `K......` ( `id` , `k......` ) VALUES (...)    |           |       2447 |         0 |          0 | 499.33 ms     | 9.65 ms     | 204.06 us   | 108.28 ms    |         0 |             0 |            0 |          0 |               0 |           0 |                 0 | 675e32e9eac555f33df240e80305c013 |
| SELECT * FROM `K......` WHERE k...... IN (...)                    |           |       2237 |         0 |          0 | 1.58 s        | 62.33 ms    | 704.19 us   | 345.61 ms    |     59212 |            26 |        59212 |          0 |               0 |           0 |                 0 | 8aa7dc3b6f729aec61bd8d7dfa5978fa |
| SELECT COUNT ( * ) FROM D..... WHERE NAME = ? OR NAME = ?         |           |       1285 |         0 |          0 | 797.72 ms     | 131.29 ms   | 620.79 us   | 340.45 ms    |      1285 |             1 |            8 |          0 |               0 |           0 |                 0 | 1975f53832b0c2506de482898cf1fd37 |
+-------------------------------------------------------------------+-----------+------------+-----------+------------+---------------+-------------+-------------+--------------+-----------+---------------+--------------+------------+-----------------+-------------+-------------------+----------------------------------+

Indeed, this simple query highlights a pile of additional information necessary for analysis like:

  1. What is that CREATE VIEW command that’s executed many more times?
  2. In this view, query 2 is executed some 3x more then query 4, yet in my 60 second sample it was 3x less. Has the profile of query load changed. What exactly is being sampled in this view?
  3. The lock_latency shows some incredibility large lock times, over 5 seconds for the top SELECT statement. Is this an outlier. Unfortunately the views give min/avg/max for the total_latency but no breakdown on lock_latency to see how much of a problem this actually is?

A quick note, the statement_analysis_raw view gives you the full SQL statement, so for example the first point listed the statement actually was.

select query from ps_helper.statement_analysis_raw order by exec_count desc limit 1;
CREATE VIEW `io_by_thread_by_latency` AS SELECT IF ( `processlist_id` IS NULL , `SUBSTRING_INDEX` ( NAME , ? , - ? ) , `CONCAT` ( `processlist_user` , ? , `processlist_host` ) ) SYSTEM_USER , SUM ( `count_star` ) `count_star` , `format_time` ( SUM ( `sum_timer_wait` ) ) `total_latency` , `format_time` ( MIN ( `min_timer_wait` ) ) `min_latency` , `format_time` ( AVG ( `avg_timer_wait` ) ) `avg_latency` , `format_time` ( MAX ( `max_timer_wait` ) ) `max_latency` , `thread_id` , `processlist_id` FROM `performance_schema` . `events_waits_summary_by_thread_by_event_name` LEFT JOIN `performance_schema` . `threads` USING ( `thread_id` ) WHERE `event_name` LIKE ? AND `sum_timer_wait` > ? GROUP BY `thread_id` ORDER BY SUM ( `sum_timer_wait` ) DESC

An unexplained connection experience

Friday, October 4th, 2013

The “Too many connections” problem is a common issue with applications using excessive permissions (and those that grant said global permissions). MySQL will always grant a user with SUPER privileges access to a DB to investigate the problem with a SHOW PROCESSLIST and where you can check the limits. I however found the following.

mysql> show global variables like 'max_connections';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 2000  |
+-----------------+-------+
1 row in set (0.00 sec)

mysql> show global status like 'max%';
+----------------------+-------+
| Variable_name        | Value |
+----------------------+-------+
| Max_used_connections | 6637  |
+----------------------+-------+
1 row in set (0.00 sec)

How can the max_used_connection exceed max_connections? This is possible because you can dynamically change max_connections in a normal MySQL environment. However ,this is AWS RDS where you cannot change variables dynamically via mysql client. You can via other command line options but this has not happened. Furthermore, this server is using the defauly.mysql.5.5 parameter group to further validate the claim that it has not been changed.

I do not have an answer for the client in this case.

I would also add this as another ding on the usability of RDS in production environments. I was locked out of the DB for a long time, and with no visibility of what was going on. The only options were wait, or restart the server. RDS does not provide this level of visibility of the processlist using a privileged user that could see what was going on. Perhaps an interface they should consider in future.

Additional DB objects in AWS RDS

Friday, August 30th, 2013

To expand on Jervin’s Default RDS Account Privileges, RDS for MySQL provides a number of routines and triggers defined the the ‘mysql’ meta schema. These help in various tasks because the SUPER privilege is not provided.

SELECT routine_schema,routine_name
FROM information_schema.routines;
+----------------+-----------------------------------+
| routine_schema | routine_name                      |
+----------------+-----------------------------------+
| mysql          | rds_collect_global_status_history |
| mysql          | rds_disable_gsh_collector         |
| mysql          | rds_disable_gsh_rotation          |
| mysql          | rds_enable_gsh_collector          |
| mysql          | rds_enable_gsh_rotation           |
| mysql          | rds_kill                          |
| mysql          | rds_kill_query                    |
| mysql          | rds_rotate_general_log            |
| mysql          | rds_rotate_global_status_history  |
| mysql          | rds_rotate_slow_log               |
| mysql          | rds_set_configuration             |
| mysql          | rds_set_gsh_collector             |
| mysql          | rds_set_gsh_rotation              |
| mysql          | rds_show_configuration            |
| mysql          | rds_skip_repl_error               |
+----------------+-----------------------------------+
15 rows in set (0.00 sec)

SELECT trigger_schema, trigger_name,
          CONCAT(event_object_schema,'.',event_object_table) AS table_name,
          CONCAT(action_timing,' ',event_manipulation) AS trigger_action
FROM information_schema.triggers;
+----------------+--------------+------------+----------------+
| trigger_schema | trigger_name | table_name | trigger_action |
+----------------+--------------+------------+----------------+
| mysql          | block_proc_u | mysql.proc | BEFORE UPDATE  |
| mysql          | block_proc_d | mysql.proc | BEFORE DELETE  |
| mysql          | block_user_i | mysql.user | BEFORE INSERT  |
| mysql          | block_user_u | mysql.user | BEFORE UPDATE  |
| mysql          | block_user_d | mysql.user | BEFORE DELETE  |
+----------------+--------------+------------+----------------+

Unexplained (trivial) MySQL behavior

Friday, August 2nd, 2013

The -N or –skip-column-names is a convenient option with the mysql client to skip the header line of output.
However I found when viewing the output via the terminal, some interesting and unexplained output.

$ mysql -h*** -u*** -p -e "SELECT VARIABLE_NAME,VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS"
+--------------------------------+----------------+
| VARIABLE_NAME                  | VARIABLE_VALUE |
+--------------------------------+----------------+
| ABORTED_CLIENTS                | 710001         |
| ABORTED_CONNECTS               | 31             |
| BINLOG_CACHE_DISK_USE          | 0              |
| BINLOG_CACHE_USE               | 0              |
| BYTES_RECEIVED                 | 2522301004     |
| BYTES_SENT                     | 317785976      |
| COM_ADMIN_COMMANDS             | 2890667        |
| COM_ASSIGN_TO_KEYCACHE         | 0              |
| COM_ALTER_DB                   | 0              |
| COM_ALTER_DB_UPGRADE           | 0              |
$ mysql -N -h*** -u*** -p -e "SELECT VARIABLE_NAME,VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS"
+--------------------------------+--------------+
|                ABORTED_CLIENTS |       710001 |
|               ABORTED_CONNECTS |           31 |
|          BINLOG_CACHE_DISK_USE |            0 |
|               BINLOG_CACHE_USE |            0 |
|                 BYTES_RECEIVED |   2522947764 |
|                     BYTES_SENT |    348838502 |
|             COM_ADMIN_COMMANDS |      2890742 |

As you can see all the values of the first column are right aligned in terminal display. When written to a file (which is the intended outcome), the data is not.

$ mysql ... > /tmp/x
$ head /tmp/x
ABORTED_CLIENTS	710009
ABORTED_CONNECTS	31
BINLOG_CACHE_DISK_USE	0
BINLOG_CACHE_USE	0
BYTES_RECEIVED	2526760299
BYTES_SENT	530046795
COM_ADMIN_COMMANDS	2890742
COM_ASSIGN_TO_KEYCACHE	0
COM_ALTER_DB	0
COM_ALTER_DB_UPGRADE	0

MySQL Presentations to the Colombia Oracle Users Group

Monday, July 15th, 2013

My slides for presentations on MySQL Backup and Recovery Essentials and Understanding and using MySQL in the Cloud from the Oracle Technology Network (OTN) event in Medellín‎ Colombia are now available.

Thank you to the Colombia Oracle Users Group for inviting me to the event.

Upgrading to MySQL 5.5 on Ubuntu 10.04 LTS

Tuesday, January 22nd, 2013

Ubuntu does not provide an apt-get repository package for MySQL 5.5 on this older OS, however this is still a widely used long term support version. The following steps will upgrade an existing MySQL 5.1 apt-get version to a standard MySQL 5.5 binary.

Step 1. Remove existing MySQL 5.1 retaining data and configuration

sudo su -
service mysql stop
cp -r /etc/mysql /etc/mysql.51
cp -r /var/lib/mysql /var/lib/mysql.51
which mysqld
dpkg -P mysql-server mysql-server-5.1 mysql-server-core-5.1
which mysqld
which mysql
dpkg -P mysql-client-5.1 mysql-client-core-5.1
which mysql
dpkg -P libdbd-mysql-perl libmysqlclient16 mysql-common
# This will not remove /etc/mysql if any other files are in the directory
dpkg -l | grep mysql
[ -d /etc/mysql ] && mv /etc/mysql /etc/mysql.uninstall
cp -r /etc/mysql.51 /etc/mysql

2. Prepare configuration and required directories.

sudo su -
MYCNF="/etc/mysql/my.cnf"
grep basedir ${MYCNF}
sed -ie "s/^basedir.*$/basedir=\/opt\/mysql/" ${MYCNF}
grep basedir ${MYCNF}
sed -ie "/^\[mysqld_safe\]/a\
skip-syslog" ${MYCNF}
chown -R mysql:mysql /var/lib/mysql
mkdir -p /var/run/mysqld
sudo chown mysql:mysql /var/run/mysqld

Install MySQL 5.5

sudo su -
mkdir -p /opt
cd /opt
# Install MySQL 5.5 Binaries
apt-get install -y libaio-dev  # New 5.5 dependency
wget http://cdn.mysql.com/Downloads/MySQL-5.5/mysql-5.5.28-linux2.6-x86_64.tar.gz
tar xvfz mysql*.tar.gz
ln -s mysql-5.5.28-linux2.6-x86_64 /opt/mysql
echo "export MYSQL_HOME=/opt/mysql
export PATH=\$MYSQL_HOME/bin:\$PATH" > /etc/profile.d/mysql.sh
chmod +x /etc/profile.d/mysql.sh
. /etc/profile.d/mysql.sh
echo $MYSQL_HOME
echo $PATH
which mysql

4. Upgrade and verify MySQL Instance

su - mysql
cd $MYSQL_HOME
bin/mysqld_safe --skip-syslog &
tail /var/log/mysql/error.log
# There will be some expected ERRORS in error log
bin/mysql_upgrade -uroot
bin/mysqladmin -uroot  shutdown
bin/mysqld_safe --skip-syslog &
tail -100 /var/log/mysql/error.log
mysql -uroot -e "SELECT VERSION();"
bin/mysqladmin -uroot  shutdown
exit

5. Setup MySQL for system use

# As Root
sudo su -
INIT="/etc/init.d/mysqld"
cp /opt/mysql/support-files/mysql.server ${INIT}
sed -ie "s/^basedir=$/basedir=\/opt\/mysql/;s/^datadir=$/datadir=\/var\/lib\/mysql/" ${INIT}
${INIT} start
mysql -uroot -e "SELECT VERSION();"
${INIT} stop

Not a cool new feature for Master_Host

Friday, January 4th, 2013

I was surprised to find on a customer MySQL server this new syntax for Master_host in SHOW SLAVE STATUS.

mysql> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
               Slave_IO_State: Connecting to master
                  Master_Host: testdb1.xxx.com or 10.XXX.XX.XXX
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: db1-354215-bin-log.000005
          Read_Master_Log_Pos: 1624
               Relay_Log_File: db2-354214-relay-log.000001
   

Is this a fancy new Percona Server feature? No. It’s operator error.

We read a little further to find.

mysql> SHOW SLAVE STATUS\G
...
             Slave_IO_Running: Connecting

...
                Last_IO_Errno: 2005
                Last_IO_Error: error connecting to master 'repl@ testdb1.xxx.com or 10.XXX.XX.XXX' - retry-time: 60  retries: 86400

How can this be created.
Using MySQL MHA, you get the following message in the output of commands to manage replication.

...
Thu Jan  3 17:06:40 2013 - [info]  All other slaves should start replication from here.
Statement should be: CHANGE MASTER TO MASTER_HOST='testdb1.xxx.com or 10.XXX.XX.XXX', MASTER_PORT=3306,
 MASTER_LOG_FILE='db1-354215-bin-log.000005', MASTER_LOG_POS=1624, MASTER_USER='repl',
MASTER_PASSWORD='xxx';
...

Needless to say, this syntax was taken literately, and MySQL did not complain.

I would suggest here that while MySQL does not do any validation on the value of the MASTER_HOST value in the CHANGE MASTER TO command to ensure it is resolvable it should at least do some validation to ensure the value is either a DNS entry or an IPV4,IPV6 value, that is space ‘ ‘, is not a valid character in these situations.

SQLSTATE[HY000]: General error: 2006 MySQL server has gone away

Wednesday, January 2nd, 2013

This would have to be one of the most common MySQL error messages that is misleading to the end user developer. The MySQL Manual page confirms the broad range of possible conditions, but offers little to a PHP developer that does not speak MySQL Geek. I am commonly asked to help solve this issue from a developer.

The problem is that there are several conditions that can cause this error, and a more meaningful explanation to the end user would help in addressing the issue. In general terms, this actually means “Your SQL statement has failed because the connection to the database has been disconnected because of ???”.

Here are a few common situations and how to check for what “???” is.

1. Your MySQL server really did go away.

We can easily check this by looking at the server uptime and the server error log.

$ mysql -uroot -p -e "show global status like 'uptime';"
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Uptime        | 68928 |
+---------------+-------+
1 row in set (0.04 sec)
$ tail /var/log/mysql/error.log
130101 22:22:30 InnoDB: Initializing buffer pool, size = 256.0M
130101 22:22:30 InnoDB: Completed initialization of buffer pool
130101 22:22:30 InnoDB: highest supported file format is Barracuda.
130101 22:22:30 InnoDB: 1.1.8 started; log sequence number 63444325509
130101 22:22:30 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3306
130101 22:22:30 [Note]   - '127.0.0.1' resolves to '127.0.0.1';
130101 22:22:30 [Note] Server socket created on IP: '127.0.0.1'.
130101 22:22:30 [Note] Event Scheduler: Loaded 0 events
130101 22:22:30 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.5.28-cll'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MySQL Community Server (GPL)

In both these cases, the server has been up some time, and there are zero error messages to indicate problems.

If the MySQL server did go away, was it shutdown or did it crash? The MySQL error log will provide the answers. Generally the mysql daemon (mysqld) will be restarted by the mysqld_safe wrapper process.

2. The connection timed out

$ mysql -uroot -p -e "show global variables like '%timeout';"
+----------------------------+----------+
| Variable_name              | Value    |
+----------------------------+----------+
| connect_timeout            | 30       |
| delayed_insert_timeout     | 300      |
| innodb_lock_wait_timeout   | 50       |
| innodb_rollback_on_timeout | OFF      |
| interactive_timeout        | 28800    |
| lock_wait_timeout          | 31536000 |
| net_read_timeout           | 30       |
| net_write_timeout          | 60       |
| slave_net_timeout          | 3600     |
| wait_timeout               | 28800    |
+----------------------------+----------+

These values are relatively sane MySQL defaults. If however you have very short timeouts, you may get this error. Here is just one example.

mysql> SET SESSION wait_timeout=5;

## Wait 10 seconds

mysql> SELECT NOW();
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    132361
Current database: *** NONE ***

+---------------------+
| NOW()               |
+---------------------+
| 2013-01-02 11:31:15 |
+---------------------+
1 row in set (0.00 sec)

3. Your SQL statement was killed

Some systems will proactively kill SQL statements that have been running too long. You can easily check if this may be happening proactively by looking at how many KILL statements have been executed.

$ mysql -uroot -p -e "show global status like 'com_kill'"
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_kill      | 0     |
+---------------+-------+

Not killed this time.

4. Your SQL statement was too large.

A little harder to test and verify, but MySQL uses a maximum packet site for communications between the server and the client. If this includes large fields (for example BLOB columns), you may be getting a termination of your SQL statement due to size.

By default this is relatively small.

mysql> show global variables like 'max_allowed_packet';
+--------------------+---------+
| Variable_name      | Value   |
+--------------------+---------+
| max_allowed_packet | 1048576 |
+--------------------+---------+
1 row in set (0.00 sec)

You can increase, for example to 16M with:

mysql> set global max_allowed_packet=1024*1024*16;
mysql> show global variables like 'max_allowed_packet';
+--------------------+----------+
| Variable_name      | Value    |
+--------------------+----------+
| max_allowed_packet | 16777216 |
+--------------------+----------+
1 row in set (0.00 sec)

The good news, is this was the cause for the customer today, and now no more errors!

Be sure to keep this value during MySQL restarts.

#my.cnf
[mysqld]
max_allowed_packet = 16M

Joining the Continuent Team

Tuesday, September 11th, 2012

This month I have joined the team at Continuent. No stranger to the MySQL ecosystem, Continuent provides replication and clustering technology for managing data between MySQL, Oracle, PostgreSQL, Vertica and a growing list of data stores.

I have known many of the team at Continuent for some time, and will again be joining Giuseppe Maxia from our days at MySQL Inc/AB starting back in 2006.

I am looking forward to taking the hard work out of administration of MySQL systems with the simplicity of Continuent Tungsten, simplifying tasks including automatic failover, multi-master and geo cluster redundancy to a single command.

Catch me speaking at the upcoming MySQL Connect (San Francisco) and Percona Live (New York) conferences, and where the third book of the Effective MySQL Series Replication Techniques in Depth will also be available for sale.

MySQL client password security

Wednesday, August 15th, 2012

In case you missed it, MySQL 5.6.6, also known as Milestone 9, was recently released. I have yet to install this, however just one part of the MySQL 5.6.6 Release Notes makes placing installing and testing high on my TODO list.

Updated 20 Sep, 2012. Be sure to also read Todd’s post Understanding mysql_config_editor’s security aspects about a more in-depth and accurate description of this new feature. In summary, “It makes secure access via MySQL client applications easier to use”.

That is the reported improvements in password management. From the release notes:

Security Improvements

These security improvements were implemented:

MySQL now provides a method for storing authentication credentials securely in an option file named .mylogin.cnf. To create the file, use the mysql_config_editor utility. The file can be read later by MySQL client programs to obtain authentication credentials for connecting to a MySQL server. mysql_config_editor writes the .mylogin.cnf file using encryption so the credentials are not stored as clear text, and its contents when decrypted by client programs are used only in memory. In this way, passwords can be stored in a file in non-cleartext format and used later without ever needing to be exposed on the command line or in an environment variable. This improves security for interactive use of MySQL client programs, as well as security for noninteractive tasks that require a MySQL password from a file. For more information, see Section 4.6.6, “mysql_config_editor — MySQL Configuration Utility”.

The .mylogin.cnf file can contain multiple sets of options, known as “login paths.” To specify which option group to use from the .mylogin.cnf file for connecting to the server, use the –login-path option. See Section 4.2.3.4, “Command-Line Options that Affect Option-File Handling”.

There are additional improvements and modifications around encryption. Well worth reading about in MySQL 5.6.6 Release Notes.

Recent Presentations in Cali, Colombia

Friday, July 20th, 2012

On July 4 I gave two presentations at the OTN Tour Day, and on July 5 I have three presentations at the MySQL Training Days. This was my 3rd visit to Colombia and it was great to see a receptive audience. Thanks to Robin for organizing the events in 2010, 2011 and 2012.

You can download all presentations from the provided links.

Video interviews at OTN Colombia

Friday, July 20th, 2012

The following are short interviews from the Oracle Technology Network (OTN) event in Cali, Colombia. One with myself and another with Sheeri Cabral.


These Videos are sourced from OTN Tour Latin America 2012.

I will be speaking at Percona Live New York

Tuesday, July 17th, 2012

Percona Live New York City, October 1 - 2, 2012
Percona is back for a second New York Percona Live Conference. As the resident New York MySQL Expert, I will again be presenting. My session will be on MySQL Backup and Recovery Essentials.

You can only present so much in one hour, and this presentation just touches on the highlights of what is possible. More detailed information about the right backup and recovery strategy and associated tools is available in my current book Effective MySQL: Backup and Recovery.

Encrypting your MySQL backups and more

Monday, July 16th, 2012

Assuming you have a backup and recovery strategy in place, how secure is your data? Does a hacker need to obtain access to your production system bypassing all the appropriate security protection you have in place, or just the unencrypted data on the backup server?

Encryption with zNcrypt

The following steps demonstrate how I setup a mysqldump encrypted backup with zNcrypt, a product from Gazzang. You can request a free trial evaluation of the software from http://gazzang.com/request-a-trial. I asked for a AWS EC2 instance, and was able to provide my bootstrap instructions for OS and MySQL installation. Following installation and configuration, the first step is to verify the zNcrypt process is running:

$ sudo ezncrypt-service status
  ezncrypt | Checking system dependencies
** ezncrypt system is UP and running **
       log | File: /var/log/ezncrypt/ezncrypt-service.log

If the process is not running you would find the following error message:

$ sudo ezncrypt-service status
  ezncrypt | Checking system dependencies
** ezncrypt system is NOT running **
       log | File: /var/log/ezncrypt/ezncrypt-service.log

$ sudo ezncrypt-service start
  ezncrypt | Checking system dependencies
  ezncrypt | checking encryption directories
    keymgr | Retrieving key from KSS
           |  > Encryption password retrieved from KSS
  ezncrypt | starting service
           |  > using "aes_256" cipher algorithm
           | done!
    access | Loading access control list
           | done!
  ezncrypt | Thank you for using ezncrypt.
       log | File: /var/log/ezncrypt/ezncrypt-service.log

Under the covers you will find the following attached devices, and no actual processes.

$ df -h
Filesystem ...
...
/var/lib/ezncrypt/storage/encrypted_private
/var/lib/ezncrypt/ezncrypted

$ ps -ef | grep ezn
uid  4947  3327  0 23:15 pts/3    00:00:00 grep ezn

$ ps -ef | grep cry
root        30     2  0 21:41 ?        00:00:00 [ecryptfs-kthrea]
root        31     2  0 21:41 ?        00:00:00 [crypto]
uid  4951  3327  0 23:15 pts/3    00:00:00 grep cry

The first step is to create a backup directory and encrypt all contents that are placed in the directory. ezNcrypt uses the concept of an @category for reference with an encrypted file or directory.

$ mkdir /mysql/backup/encrypted
$ sudo ezncrypt --encrypt @backup /mysql/backup/encrypted
  ezncrypt | Checking system dependencies
           | Verifying ezncrypt license
           | getting information about location
           |   > path: /var/lib/ezncrypt/ezncrypted/backup
  ezncrypt | Checking encryption status
           | done!
    keymgr | Retrieving key from KSS
           |  > Encryption password retrieved from KSS
           | generating keys
           | done!
    backup | backing up data
           | This can take a while. Please be patient
           |  > backing up /mysql/backup/encrypted
           |  > File: /opt/ezncrypt/backup/2012-04-27/encrypted.tar.gz
           | done!
  ezncrypt | encrypting files
           |  > checking disk space
           |  > encrypting /mysql/backup/encrypted
           | done!
  ezncrypt | congratulations. you have encrypted your Files!!
       log | File: /var/log/ezncrypt/ezncrypt.log

The underlying regular directory is now replaced:

$ ls -l /mysql/backup
total 0
lrwxrwxrwx 1 root root 59 2012-04-27 00:03 encrypted -> /var/lib/ezncrypt/ezncrypted/backup//mysql/backup/encrypted

Any attempts to write to this encrypted directory will now fail, even with the Linux super user:

$ mysqldump --all-databases > /mysql/backup/encrypted/edump1.sql
-bash: /mysql/backup/encrypted/edump1.sql: Permission denied

$ sudo mysqldump --all-databases > /mysql/backup/encrypted/edump1.sql
-bash: /mysql/backup/encrypted/edump1.sql: Permission denied

In order to read and write from an encrypted directory you need to grant access controls to a given program, for example mysqldump:

$ sudo ezncrypt-access-control -a "ALLOW @backup * /usr/bin/mysqldump"
passphrase:
salt:
Rule added

You verify the defined access control rules with:

$ sudo ezncrypt-access-control -L
passphrase:
salt:
# -  Type     Category       Path    Process
1    ALLOW    @backup        *       /usr/bin/mysqldump

However, writing with mysqldump still causes an error because it is the shell redirection that is performing the writing, as seen in the system error log:

$ mysqldump --all-databases > /mysql/backup/encrypted/edump1.sql
-bash: /mysql/backup/encrypted/edump1.sql: Permission denied
$ dmesg | tail
[4138848.618559] ezncryptfs: DENIED type="acl" exec="/bin/bash" script="/dev/pts/4" comm="bash" path="/var/lib/ezncrypt/ezncrypted/backup" pid=7448 uid=1000

You can use the –result-file option with mysqldump to enable the process to create the file directly. For example:

$ time mysqldump --all-databases   --result-file=/mysql/backup/encrypted/edump2.sql
real      1m34.714s
user      0m59.388s
sys       0m9.589s

$ sudo ezncrypt-run "ls -l /mysql/backup/encrypted/"
passphrase:
salt:
total 3.0G
-rw-rw-r-- 1 uid gid 2.9G 2012-04-27 02:43 edump2.sql

In this single test, the transparent encryption added only a very nominal overhead to the mysqldump test backup used. You can easily extract the file from the encrypted directory, however that would defeat the purpose of using encryption. The following syntax is shown just to confirm the validity of the encrypted file:

$ sudo /usr/sbin/ezncrypt-run "cp /mysql/backup/encrypted/edump2.sql ."
passphrase:
salt:
$ ls –al edump*
total 3916
-rw-r--r-- 1 uid gid 2.9G 2012-04-27 02:55 edump2.sql

$ grep "^CREATE.*DATABASE" edump2.sql
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `book2` /*!40100 DEFAULT CHARACTER SET latin1 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `employees` ...
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `musicbrainz` ...
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `mysql` ...
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `sakila` ...
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `world_innodb` ...
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `world_myisam` ...

When using correctly configured directories and access controls, the use is truly transparent to the backup process.

Restoring an encrypted file is a little more involved. The best approach is to create a script to perform the work, than encrypt this script. When executed, this script will have the permissions necessary to read and apply the encrypted file.

Perhaps the best tip about using this type of transparent encryption is that it is possible to encrypt the MySQL user and password securely in a plain text configuration file and used with appropriate MySQL client commands. This helps to address another common security problem.

What compression do you use?

Friday, July 13th, 2012

The following is an evaluation of various compression utilities that I tested when reviewing the various options for MySQL backup strategies. The overall winner in performance was pigz, a parallel implementation of gzip. If you use gzip today as most organizations do, this one change will improve your backup compression times.

Details of the test:

  • The database is 5.4GB of data
  • mysqldump produces a backup file of 2.9GB
  • The server is an AWS t1.xlarge with a dedicated EBS volume for backups

The following testing was performed to compare the time and % compression savings of various available open source products. This was not an exhaustive test with multiple iterations and different types of data files.

Compression
Utility
Compression Time
(sec)
Decompression Time
(sec)
New Size
(% Saving)
lzo (-3) 21 34 1.5GB (48%)
pigz (-1) 43 33 995MB (64%)
pigz (-3) 56 34 967MB (67%)
gzip (-1) 81 43 995MB (64%)
fastlz 92 128 1.3GB (55%)
pigz [-6] 105 25 902MB (69%)
gzip (-3) 106 43 967MB (67%)
compress 145 36 1.1GB (62%)
pigz (-9) 202 23 893MB (70%)
gzip [-6] 232 78 902MB (69%)
zip 234 50 902MB (69%)
gzip (-9) 405 43 893MB (70%)
bzip2 540 175 757MB (74%)
rzip 11 minutes 360 756MB (74%)
lzo (-9) 20 minutes 82 1.2GB (58%)
7z 33 minutes 122 669MB (77%)
lzip 47 minutes 132 669MB (77%)
lzma 58 minutes 180 639MB (78%)
xz 59 minutes 160 643MB (78%)

Observations

  • The percentage savings and compression time of results will vary depending on the type of data that is stored in the MySQL database.
  • The pigz compression utility was the surprising winner in best compression time producing at least a size of gzip. This was a full 50% faster than gzip.
  • For this compression tests, only one large file was used. Some utilities work much better with many smaller files.

Find our more information of these tests and the results in Effective MySQL: Backup and Recovery

Recent Presentations Buenos Aires MySQL/NoSQL/Cloud Conference

Thursday, July 12th, 2012

The first annual Latin America MySQL/NoSQL/Cloud Conference was held in Buenos Aires Argentina from June 26-28. Kudos to Santiago Lertora from Binlogic who had the vision for the conference in his country and made it happen. I look forward to the second annual event.

My first presentation was “Improving Performance with Better Indexes”. This presentation details the six steps to SQL performance analysis, Capture, Identify, Confirm, Analyze, Optimize and Verify. An explanation of MySQL EXPLAIN, and working examples to create indexes and better covering indexes in several examples are provided. A production example of a 13 table join is used to detail how covering indexes and partial column indexes can make a dramatic improvement in performance. Download Presentation (PDF).

More detailed information about EXPLAIN and creating indexes is available in book Effective MySQL: Optimizing SQL Statements.

My second presentation was “MySQL Backup and Recovery Essentials”. This presentation covers the most common options for MySQL backup and the respective restore options. Also covered is the importance of the master binary logs and point in time recovery capabilities. Download Presentation (PDF)

More detailed information about the right backup and recovery strategy and associated tools is available in book Effective MySQL: Backup and Recovery.

References

Latin America MySQL/NoSQL/Cloud Conference Program.

UTF-8 with MySQL and LAMP

Wednesday, May 23rd, 2012

A recent question on a mailing list was the best practices for UTF-8 and PHP/MySQL. The following are the configurations I used in my multi-language projects.

MySQL UTF-8 Configuration

# my.cnf
[mysqld]
default_character_set = utf8
character_set_client       = utf8
character_set_server       = utf8
[client]
default_character_set = utf8

PHP UTF-8 Configuration

#php.ini
default_charset = "utf-8"

Apache UTF-8 Configuration

#httpd.conf
AddDefaultCharset UTF-8
<VirtualHost>
    AddCharset UTF-8   .htm
</VirtualHost>

HTML file UTF-8 Configuration

 <meta charset="utf-8">

PHP file UTF-8 Configuration

header('Content-type: text/html; charset=UTF-8');

MySQL connection (extra precaution)

SET NAMES utf8;

Shell UTF-8

And last but not least, even editing files in shell can be affected (.e.g UTF-8 data to be inserted into DB from file). Ensure at least

#~/.profile
export LC_CTYPE=en_US.UTF-8
export LANG=en_US.UTF-8

Amateurs – They give us professionals a bad name

Thursday, April 26th, 2012

Any person with half a brain would see from the error messages below that the MySQL server is not operating optimally, or more specifically the MySQL upgrade has not completely successfully and let users can go happily use the website. It amazing me when web hosting providers tell their paying client that an upgrade has been performed yet they did not have the intelligence to actually look at the error log for confirmation. Got a mysql> prompt, it’s all good. One of the first things I check is the error log.

When will people learn the MySQL error log is a valuable resource both for what it contains, and what it should not contain.

120426 17:36:00 [Note] /usr/libexec/mysqld: Shutdown complete

120426 17:36:00 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
120426 17:36:00 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
120426 17:36:00 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: Table 'mysql.plugin' doesn't exist
120426 17:36:00 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
120426 17:36:00 InnoDB: The InnoDB memory heap is disabled
120426 17:36:00 InnoDB: Mutexes and rw_locks use GCC atomic builtins
120426 17:36:00 InnoDB: Compressed tables use zlib 1.2.3
120426 17:36:00 InnoDB: Using Linux native AIO
120426 17:36:00 InnoDB: Initializing buffer pool, size = 128.0M
120426 17:36:00 InnoDB: Completed initialization of buffer pool
120426 17:36:00 InnoDB: highest supported file format is Barracuda.
120426 17:36:00  InnoDB: Waiting for the background threads to start
120426 17:36:01 InnoDB: 1.1.8 started; log sequence number 232577699
120426 17:36:01 [ERROR] Missing system table mysql.proxies_priv; please run mysql_upgrade to create it
120426 17:36:01 [ERROR] Can't open and lock privilege tables: Table 'mysql.servers' doesn't exist
120426 17:36:01 [ERROR] Native table 'performance_schema'.'events_waits_current' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'events_waits_history' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'events_waits_history_long' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'setup_consumers' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'setup_instruments' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'setup_timers' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'performance_timers' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'threads' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'events_waits_summary_by_thread_by_event_name' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'events_waits_summary_by_instance' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'events_waits_summary_global_by_event_name' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'file_summary_by_event_name' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'file_summary_by_instance' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'mutex_instances' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'rwlock_instances' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'cond_instances' has the wrong structure
120426 17:36:01 [ERROR] Native table 'performance_schema'.'file_instances' has the wrong structure
120426 17:36:01 [ERROR] Column count of mysql.db is wrong. Expected 22, found 20. Created with MySQL 50077, now running 50523. Please use mysql_upgrade to fix this error.
120426 17:36:01 [ERROR] mysql.user has no `Event_priv` column at position 29
120426 17:36:01 [ERROR] Cannot open mysql.event
120426 17:36:01 [ERROR] Event Scheduler: An error occurred when initializing system tables. Disabling the Event Scheduler.
120426 17:36:01 [Note] /usr/libexec/mysqld: ready for connections.
Version: '5.5.23-cll'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MySQL Community Server (GPL) by Atomicorp
120426 17:46:01 [ERROR] Missing system table mysql.proxies_priv; please run mysql_upgrade to create it
120426 17:46:01 [ERROR] Can't open and lock privilege tables: Table 'mysql.servers' doesn't exist
120426 17:46:01 [ERROR] Column count of mysql.proc is wrong. Expected 20, found 16. Created with MySQL 50077, now running 50523. Please use mysql_upgrade to fix this error.

Some more light reading at Have you checked your MySQL error log today? and Monitoring MySQL – The error log

An excellent conference (5 out of 5 stars)

Saturday, April 14th, 2012

I wanted to extend thanks as others have also about the excellent annual MySQL Conference, now a Percona Live event. This was easily the best run, attended and energetic event in at least the past 3 years. With over a 1000 attendees a well stocked exhibitors hall (and good involvement in the hall), and good talks; there was just a great community vibe. To Terry, Kortney and all Percona staff involved, well done. The event ran on time, I personally did not see or hear of any issues. The only complaint was from many that wanted to attend multiple talks at the same time, another indication of the quality of speakers for the event.

Thank you to those that attended my two sessions on Explaining the MySQL Explain and MySQL Idiosyncrasies that BITE. Many people thanked me after presentations, along also with people coming up to me to say they appreciated the first book of the Effective MySQL Series. My desires to speak and write are only for the benefit of the MySQL community to hopefully learn and appreciate how to best use MySQL.

It was of course great to see many MySQL alumni, and old friends I have seen since meeting at my first MySQL conference in 2006.

TIMESTAMP data types and CURRENT_TIMESTAMP attribute

Friday, March 16th, 2012

In the yet to be released MySQL 5.6.6 DMR, there has been a change to the restriction of just one TIMESTAMP column with the DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP syntax. It is now possible for any TIMESTAMP to have either column defintion.

More information at http://dev.mysql.com/doc/refman/5.6/en/news-5-6-5.html

SQL_MODE and storage engines

Friday, March 9th, 2012

I was again reminded why setting SQL_MODE is so important in any new MySQL environment. While performing benchmark tests on parallel backup features with a common InnoDB tablespace and per file tablespace, I inadvertently missed an important step in the data migration. The result was the subsequent test that performed data population worked without any issues however there was no data in any InnoDB tables.

These are the steps used in the migration of InnoDB tables from a common tablespace model to a per-table tablespace model.

  1. Dump all InnoDB tables
  2. Drop all InnoDB tables
  3. Shutdown MySQL
  4. Change the my.cnf to include innodb-file-per-table
  5. Remove the InnoDB ibdata1 tablespace file
  6. Remove the InnoDB transactional log files
  7. Start MySQL
  8. Verify the error log
  9. Create and load new InnoDB tables

However, step 6 was not performed correctly due to a sudo+shell wildcard issue. The result was MySQL started, and tables were subsequently created incorrectly. What should have happened was:

mysql> CREATE TABLE `album` (
    ->   `album_id` int(10) unsigned NOT NULL,
    ->   `artist_id` int(10) unsigned NOT NULL,
    ->   `album_type_id` int(10) unsigned NOT NULL,
    ->   `name` varchar(255) NOT NULL,
    ->   `first_released` year(4) NOT NULL,
    ->   `country_id` smallint(5) unsigned DEFAULT NULL,
    ->   PRIMARY KEY (`album_id`)
    -> ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
ERROR 1286 (42000): Unknown table engine 'InnoDB'

However, because by default MySQL will fallback to the legacy default of MyISAM, no actual error occurred. In order for this to produce an error, an appropriate SQL_MODE is necessary.

mysql> SET GLOBAL sql_mode='NO_ENGINE_SUBSTITUTION';

A check of the MySQL error log shows why InnoDB was not available.

120309  0:59:36  InnoDB: Starting shutdown...
120309  0:59:40  InnoDB: Shutdown completed; log sequence number 0 1087119693
120309  0:59:40 [Note] /usr/sbin/mysqld: Shutdown complete

120309  1:00:16 [Warning] No argument was provided to --log-bin, and --log-bin-index was not used; so replication may break when this MySQL server acts as a master and has his hostname changed!! Please use '--log-bin=ip-10-190-238-14-bin' to avoid this problem.
120309  1:00:16 [Note] Plugin 'FEDERATED' is disabled.
120309  1:00:16  InnoDB: Initializing buffer pool, size = 500.0M
120309  1:00:16  InnoDB: Completed initialization of buffer pool
InnoDB: The first specified data file ./ibdata1 did not exist:
InnoDB: a new database to be created!
120309  1:00:16  InnoDB: Setting file ./ibdata1 size to 64 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Error: all log files must be created at the same time.
InnoDB: All log files must be created also in database creation.
InnoDB: If you want bigger or smaller log files, shut down the
InnoDB: database and make sure there were no errors in shutdown.
InnoDB: Then delete the existing log files. Edit the .cnf file
InnoDB: and start the database again.
120309  1:00:17 [ERROR] Plugin 'InnoDB' init function returned error.
120309  1:00:17 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
120309  1:00:17 [Note] Event Scheduler: Loaded 0 events
120309  1:00:17 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.1.58-1ubuntu1-log'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  (Ubuntu)

NOTE: This was performed on Ubuntu using the standard distro MySQL version of MySQL 5.1.

As previously mentioned, SQL_MODE may not be perfect, however what features do exist warrant correctly configuration your MySQL environment not to use the default.

More Information.

Why SQL_MODE is essential even when not perfect

Thursday, February 16th, 2012

In a recent rant on Why I think SQL_MODE is useless…, I wanted to counteract this statement with why we MUST all use SQL_MODE, even with the inherit flaws.

The fundamental principle of a database is to restore and retrieve data. When I can insert data into the database and then I select this data it is different, this is fundamentally wrong. This is a loss of essential data integrity, something a database should NEVER do.

SQL_MODE solves the problem of “silent truncation” in most instances, and produces an all important error. As pointed out, the SQL_MODE has several limitations, however the benefits do out way the risks. Quality control on source code can reduce the limitations, but no amount of coding can stop the CRUD that comes out of the database without some SQL_MODE settings.

I would ask two more important questions.

  1. How in the first place can such a critical feature of silent data truncation ever be permitted in MySQL? Who made that decision and why?
  2. When is the owner of MySQL codebase realize this is rather ridiculous and enforce essential minimual data integrity that can be obtain with options including STRICT_ALL_TABLES, NO_ZERO_DATE, NO_ZERO_IN_DATE and NO_ENGINE_SUBSTITUTION.

References

Colorado MySQL Users Group Presentation

Thursday, February 16th, 2012

In addition to speaking at RMOUG event in Denver, I also spoke today in Broomfield on “Improving MySQL Performance with Better Indexes”.

This presentation included details on :

  • Effective examples of capture SQL via application logging and TCP/IP analysis necessary for identifying the best candidates. Slow is not always the best query to start with.
  • All the commands necessary to identify why you may need an index, how to create varying types of indexes, and how to confirm there true effectiveness.
  • How the number of table rows and different storage engines can greatly effect the optimization choice and query performance
  • The presentation shows how to determine/create and verify covering indexes for a single table example, a master/child example and a production 13 table join.

You can obtain the slides from Improving MySQL Performance With Better Indexes Presentation.

Event Details

MySQL Security Essentials Presentation

Wednesday, February 15th, 2012

Today at the RMOUG Training Days 2012 event I gave an introduction presentation on MySQL Security Essentials covering the following topics:

  • MySQL Security defaults
  • MySQL Security Improvements
  • OS Security
  • User Privileges
  • Data Integrity
  • Installation Practices
  • Auditing Options
  • Better Security
  • Further References

Download slides for MySQL Security Essentials.

Exciting upcoming MySQL events

Tuesday, January 24th, 2012

At the IOUC leaders’ summit in San Francisco this week, key leaders from Oracle, Java and MySQL user groups world wide have been meeting. This has included the key Oracle MySQL resources from the community, marketing and product teams. The Java User Groups and MySQL User Groups have been well represented and there has been very welcoming discussion with the IOUC about how we can become active within the Oracle Community.

There has been key discussions of upcoming and proposed MySQL events including the great outreach by the Oracle MySQL team with existing Open Source conferences this year including Scale, FOSDEM and South East Linuxfest just to name a few.

You can see the upcoming events at http://mysql.com/news-and-events/events/. In February alone there will be events in North Carolina, California, Texas, Frankfurt Germany and Stockholm Sweden. I will also be speaking in Denver at 2 events and Salt Lake City.

There is a much longer list then what is shown here, and we are working on getting the full list more available.

More info by Dave Stokes at SCaLE’s MySQL Day a big hit and Keith Larson More User Groups.

Why is searching the manual so hard

Saturday, January 14th, 2012

As a consultant I often use the MySQL Reference Manual to provide additional information for clients. I am very happy to recognize the quality of the content in the MySQL documentation, but why is the searching of the manual so, so bad?

While reading the General Security Issues section of the MySQL 5.5 manual, I performed a search for “CREATE USER”. I was not asking for anything abstract, this is an actual SQL command. I was rather horrified to find that the results could not even list the appropriate manual page in the first page of results.

I am not an expert in full-text search, however it does not take a rocket scientist to realize that a SQL keyword, the title of a page, in the language of the current page (English) and the current version of the Manual (5.5) should be an easy result. This is a simple weighted result right? Wrong.



The most important MySQL Reference Manual page

Thursday, January 5th, 2012

In my opinion, The Server Option and Variable Reference at http://dev.mysql.com/doc/refman/5.5/en/mysqld-option-tables.html rates as my most important page. This is a consolidated index that enables a drill down to the Server Command Options, System Variables, Startup and replication specifics, as well as important information on default values and differences between versions including point releases.

However, there is another page not in the actual manual, but at http://dev.mysql.com/doc/mysqld-version-reference/en/mysqld-version-reference-optvar.html which is an Options/Variables reference akin to the Reference Manual, but includes a 5.x version matrix.

Recently I was asked about some options that had to be removed from an upgrade to MySQL 5.5. Some of these were obvious, however not all. This page enabled me to confirm deprecation (as expected), and also point to important reference material.

These options where:

  • default_table_type
  • log_long_format
  • master-connect-retry
  • default-character-set

The use of table_type was a 3.x/4.x relic, replaced with engine, so I was surprised this option was still even valid. The option replaced with default_storage_engine. The page defined this as deprecated in MySQL 5.0
log_long_format is also old, and definitely modified since MySQL 5.1 with the general_log_xxx options. In fact this has been deprecated since 4.1
I have never liked the master-xxx options, in favor of a CHANGE MASTER command and synchronization issues with the master.info file and master-xx options. master-connect-retry and several other options were deprecated in 5.1.17. On a side note, if you look at this option in the MySQL 5.5 Reference Manual you get Obsolete options. The following options are removed in MySQL 5.5. If you attempt to start mysqld with any of these options in MySQL 5.5, the server aborts with an unknown variable error. To set the replication parameters formerly associated with these options, you must use the CHANGE MASTER TO … statement (see Section 12.4.2.1, “CHANGE MASTER TO Syntax”).
Finally default-character-set. Initially I thought that is definitely still applicable, however the handy cross reference reminded me, this is also deprecated in MySQL 5.0 and the Reference Manual again stating default-character-set is also deprecated in 5.0 in favor of character-set-server.. The name has simply changed in newer version.

With so many options and as a consultant I work with many different versions each week, I sometimes need a refresher of the changes in the versions of the past 5 years. Definitely my second most important page.

If you have a favorite page, please let me know.

I would also like to say thank you to the Oracle/MySQL Documentation team that do a great job in providing an excellent resource to an open source product. We would all do well to appreciate this in comparison to other open source documentation in companion technologies and related tools. With every new release of a MySQL product you don’t realize that somebody reviewed, tested and wrote about features without receive the limelight.

Binary Log Replayer

Thursday, December 22nd, 2011

When using the replication slave stream, or mysql command line client and mysqlbinlog output from a binary/relay log, all statements are executed in a single thread as quickly as possible.

I am seeking a tool to simulate the replay of the binary/relay log for a benchmark at a pace that is more representative to original statements. For a simple example, if the Binary Log has 3 transactions in the first second, 2 transactions in the second second, and 5 transactions in the third second, I am wanting to simulate the replay to take roughly 3 seconds, not as fast as possible (which would be sub-second). The tool should try to wait the remainder of a second before processing SQL statements in the incoming stream.

Does anybody know of a tool that currently provides this type of functionality? Any input appreciated before I create my own.

Reasons to use MySQL 5.5 Presentation

Tuesday, June 28th, 2011

I recently gave a presentation at the New York Effective MySQL Meetup on the new features of, and some of the compelling reasons to upgrade to MySQL 5.5. There are also a number of new MySQL variables that can have a dramatic effect on performance in a highly transactional environment, innodb_buffer_pool_instances and innodb_purge_threads are just two to consider.

For more information on all the new variables, status, reserved words and benchmarks of new features you can Download Presentation Slides.