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ImageMagick on Mac OS X

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Wanting to do some image manipulation I realized my Linux scripts don’t run under Mac OS X, as ImageMagick is not installed via my MacPorts.

However installation failed:

$ sudo port install imagemagick
--->  Computing dependencies for ImageMagick
--->  Verifying checksum(s) for xorg-libX11
Error: Checksum (md5) mismatch for libX11-1.3.3.tar.bz2
Error: Checksum (sha1) mismatch for libX11-1.3.3.tar.bz2
Error: Checksum (rmd160) mismatch for libX11-1.3.3.tar.bz2
Error: Target org.macports.checksum returned: Unable to verify file checksums
Error: The following dependencies failed to build: xorg-libXext xorg-libX11 xorg-libXt xorg-libsm xorg-libice
Error: Status 1 encountered during processing.
Before reporting a bug, first run the command again with the -d flag to get complete output.

Figuring that some of my packages may require upgrade:

$ sudo port selfupdate
sudo port -d upgrade outdated

The problem is this all failed. Turning to the FAQ it seemed what I needed to do was remove and re-install the offending package receiving the checksum error via the following syntax.

$ sudo port clean --all 
$ sudo port install

It seemed I had to do this for several packages manually however in the end removing and installing a number of packages addressed the problem and now ImageMagick is happily running on Mac OS X

bash-3.2$ sudo port clean --all xorg-libX11
--->  Cleaning xorg-libX11
bash-3.2$ sudo port install xorg-libX11
---->  Computing dependencies for ImageMagick
--->  Verifying checksum(s) for xorg-libX11
Error: Checksum (md5) mismatch for libX11-1.3.3.tar.bz2
Error: Checksum (sha1) mismatch for libX11-1.3.3.tar.bz2
Error: Checksum (rmd160) mismatch for libX11-1.3.3.tar.bz2
Error: Target org.macports.checksum returned: Unable to verify file checksums
Error: The following dependencies failed to build: xorg-libXext xorg-libX11 xorg-libXt xorg-libsm xorg-libice
Error: Status 1 encountered during processing.
Before reporting a bug, first run the command again with the -d flag to get complete output.
bash-3.2$ sudo port clean --all libX11
Error: Port libX11 not found
Before reporting a bug, first run the command again with the -d flag to get complete output.
bash-3.2$ sudo port clean --all xorg-libX11
--->  Cleaning xorg-libX11
bash-3.2$ sudo port install xorg-libX11

My favorite MySQL data type – DECIMAL(31,0)

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It may seem hard to believe, but I have seen DECIMAL(31,0) in action on a production server. Not just in one column, but in 15 columns just in the largest 4 tables of one schema. The column was being used to represent a integer primary or foreign key column.

In a representative production instance (one of a dozen plus distributed production database servers) the overall database footprint was decreased from ~10 GB to ~2 GB, a 78% saving. In total, 15 columns across just 4 tables were changed from DECIMAL(31,0) to INT UNSIGNED.

One single table > 5GB was reduced to under 1GB (a 81% saving). This being my record for any GB+ tables in my time working with the MySQL database.

Had this server for example had 4GB of RAM, and say 2.5GB allocated to the innodb_buffer_pool_size, this one change moved the system from requiring more consistent disk access (4x data to memory) to being able to store all data in memory. Tests showed a clear improvement in Innodb buffer pool reads and hit ratio.

Today’s lesson as described in my 2008 conference presentation Top 20 design tips for data architects is, choose the right integer data type for your data.

More woes with java version on Ubuntu

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Armed with more information on Drizzle JDBC being a JDBC 4.0 implementation (helps to explain my issues in Getting started with Drizzle JDBC) I took the time to read about some other new JDBC 4.0 features.

There was reference to handling chained exceptions, however when trying to get this working for SQLException was more complex on Ubuntu 9.04 then I anticipated.

My first problem was an apparent source level problem.

$ javac ExampleDrizzle.java
----------
1. ERROR in ExampleDrizzle.java (at line 14)
	for(Throwable e : sx ) {
	    ^^^^^^^^^^^^^^^^
Syntax error, 'for each' statements are only available if source level is 1.5

That’s weird, what java version was I running now I’d changed with update-alternatives –config java yesterday.

$ java -version
java version "1.6.0_16"
Java(TM) SE Runtime Environment (build 1.6.0_16-b01)
Java HotSpot(TM) 64-Bit Server VM (build 14.2-b01, mixed mode)

No issues here, a quick man reference gives me:

-1.5                    set compliance level to 1.5

I try that, and well that fixes one problem, but creates another.

$ javac -1.5 ExampleDrizzle.java
----------
1. ERROR in ExampleDrizzle.java (at line 14)
	for(Throwable e : sx ) {
	                  ^^
Can only iterate over an array or an instance of java.lang.Iterable

Now Class SQLException 1.6 javadocs shows SQLException as implementing the generics Iterable<Throwable>, while 1.5 javadoc does not. I guess I need to use 1.6 then.

$ javac -1.6 ExampleDrizzle.java
Annotation processing got disabled, since it requires a 1.6 compliant JVM
----------
1. ERROR in ExampleDrizzle.java (at line 14)
	for(Throwable e : sx ) {
	                  ^^
Can only iterate over an array or an instance of java.lang.Iterable

Wait a minute, I’m using a 1.6 compliant JVM. Double checking

$ ls -al /etc/alternatives/java*
lrwxrwxrwx 1 root root 36 2009-09-17 18:53 /etc/alternatives/java -> /usr/lib/jvm/java-6-sun/jre/bin/java
lrwxrwxrwx 1 root root 46 2009-09-17 18:53 /etc/alternatives/java.1.gz -> /usr/lib/jvm/java-6-sun/jre/man/man1/java.1.gz
lrwxrwxrwx 1 root root 31 2009-09-17 17:50 /etc/alternatives/javac -> /usr/lib/jvm/java-gcj/bin/javac
lrwxrwxrwx 1 root root 41 2009-09-17 17:50 /etc/alternatives/javac.1.gz -> /usr/lib/jvm/java-gcj/man/man1/javac.1.gz
lrwxrwxrwx 1 root root 33 2009-09-17 17:50 /etc/alternatives/javadoc -> /usr/lib/jvm/java-gcj/bin/javadoc
lrwxrwxrwx 1 root root 43 2009-09-17 17:50 /etc/alternatives/javadoc.1.gz -> /usr/lib/jvm/java-gcj/man/man1/javadoc.1.gz
lrwxrwxrwx 1 root root 31 2009-09-17 17:50 /etc/alternatives/javah -> /usr/lib/jvm/java-gcj/bin/javah
lrwxrwxrwx 1 root root 41 2009-09-17 17:50 /etc/alternatives/javah.1.gz -> /usr/lib/jvm/java-gcj/man/man1/javah.1.gz
lrwxrwxrwx 1 root root 33 2009-09-11 10:06 /etc/alternatives/javap -> /usr/lib/jvm/java-6-sun/bin/javap
lrwxrwxrwx 1 root root 43 2009-09-11 10:06 /etc/alternatives/javap.1.gz -> /usr/lib/jvm/java-6-sun/man/man1/javap.1.gz
lrwxrwxrwx 1 root root 39 2009-09-11 10:06 /etc/alternatives/java_vm -> /usr/lib/jvm/java-6-sun/jre/bin/java_vm
lrwxrwxrwx 1 root root 38 2009-09-11 10:06 /etc/alternatives/javaws -> /usr/lib/jvm/java-6-sun/jre/bin/javaws
lrwxrwxrwx 1 root root 48 2009-09-11 10:06 /etc/alternatives/javaws.1.gz -> /usr/lib/jvm/java-6-sun/jre/man/man1/javaws.1.gz

javac is not using Sun Java 6. I have no idea how that happened, but it explains now the problem, should be checking javac version, not java version.

$ javac -version
Eclipse Java Compiler 0.894_R34x, 3.4.2 release, Copyright IBM Corp 2000, 2008. All rights reserved.

What the? I was writing Java code on this server by hand, but decided last night to install eclipse after the fact. Did this affect this. I’m not certain whether I installed eclipse before or after my work last night.

I try to change the alternatives again.

$ sudo update-alternatives --config java

There are 4 alternatives which provide `java'.

  Selection    Alternative
-----------------------------------------------
*         1    /usr/lib/jvm/java-6-sun/jre/bin/java
          2    /usr/bin/gij-4.3
          3    /usr/bin/gij-4.2
 +        4    /usr/lib/jvm/java-gcj/jre/bin/java

Press enter to keep the default[*], or type selection number: 1
Using '/usr/lib/jvm/java-6-sun/jre/bin/java' to provide 'java'.

$ javac -version
Eclipse Java Compiler 0.894_R34x, 3.4.2 release, Copyright IBM Corp 2000, 2008. All rights reserved.

That doesn’t work. One needs to know that java and javac operate independently.

$ sudo update-alternatives --config javac

There are 4 alternatives which provide `javac'.

  Selection    Alternative
-----------------------------------------------
          1    /usr/lib/jvm/java-6-sun/bin/javac
          2    /usr/bin/ecj
          3    /usr/bin/gcj-wrapper-4.3
*+        4    /usr/lib/jvm/java-gcj/bin/javac

Press enter to keep the default[*], or type selection number: 1
Using '/usr/lib/jvm/java-6-sun/bin/javac' to provide 'javac'.
$ javac -version
javac 1.6.0_16

$ javac ExampleDrizzle.java

Buyer beware with Ubuntu and it’s rather messed up implementation approach toward alternative java JVM’s.

Explain this

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The EXPLAIN command is an important tool to review how a SQL query is executed and in this example includes what indexes are used.

By adding a covering index I ended up with the following EXPLAIN plan I was unable to explain. The end result was a boost in server performance which was the ultimate goal.

mysql> explain select max(md)  from e_r  where email = '[email protected]' and id = '36981';
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra                        |
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
|  1 | SIMPLE      | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | Select tables optimized away |
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
1 row in set (0.00 sec)

The queries still produced the expected results.

MySQL Replication 102

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One of the most asked questions is how to setup MySQL replication. The MySQL Reference Manual provides a good Replication How To as a starting guide on MySQL Replication 101.

MySQL replication has many uses including read scalability, backups, failover, online maintenance, upgrade testing and verification, software upgrades, alternative data or structure for performance queries and even benchmarking to name the popular uses.

When reviewing an installation of MySQL replication I use the following as part of my checklist of steps used for confirming your replication environment is operational.

Master Variables

  • server-id – Replication will not work without this correctly set and unique
  • log-bin – Pre-requisite for working replication
  • log-bin-index
  • max_binlog_size
  • binlog_cache_size
  • expire_logs_days – a value from 5 to 10 is good, not set can result in a full disk.
  • binlog-do-db/binlog-ignore-db – Use with caution
  • sync_binlog
  • innodb_support_xa

Slave Variables

  • server-id – Replication will not work without this correctly set and unique
  • read_only = TRUE
  • log-bin – may or may not be present
  • relay-log
  • relay-log-index
  • max_binlog_size
  • binlog_cache_size
  • expire_logs_days – a value from 5 to 10 is good, not set can result in a full disk.
  • replicate-do-???? – Warning, use these with caution. Your slave will not be the same as your master.
  • slave-skip-errors – Warning, this can lead to your slave being inconsistent with your slave.

On the Master I audit the following information.

  • SHOW MASTER STATUS
    • If any Binlog_Do_DB, then a SHOW SCHEMAS for verification
  • SHOW MASTER LOGS
    • Confirm physical files as well as available diskspace on log-bin disk partition
  • SHOW SLAVE STATUS (in a true master/slave environment this should be empty)
  • SHOW GLOBAL VARIABLES LIKE ‘binlog_cache_size';
  • SHOW GLOBAL STATUS LIKE ‘Binlog%’
  • SELECT host,user,password FROM mysql.user WHERE Repl_slave_priv=’Y’ AND Super_priv=’N';

On the Slave I audit the following information.

  • SHOW SLAVE STATUS
  • SHOW MASTER STATUS – This will determine if you have log-bin enabled on the slave

The key information for MySQL slaves is in the SHOW SLAVE STATUS command. An example output is:

mysql> show slave statusG
*************************** 1. row ***************************
             Slave_IO_State:
                Master_Host: 10.10.1.1
                Master_User: slave
                Master_Port: 3306
              Connect_Retry: 60
            Master_Log_File: bin-log.001817
        Read_Master_Log_Pos: 369684547
             Relay_Log_File: relay-log.000449
              Relay_Log_Pos: 42347742
      Relay_Master_Log_File: bin-log.001817
           Slave_IO_Running: No
          Slave_SQL_Running: No
            Replicate_Do_DB:
        Replicate_Ignore_DB:
         Replicate_Do_Table:
     Replicate_Ignore_Table:
    Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
                 Last_Errno: 0
                 Last_Error:
               Skip_Counter: 0
        Exec_Master_Log_Pos: 369684547
            Relay_Log_Space: 42347742
            Until_Condition: None
             Until_Log_File:
              Until_Log_Pos: 0
         Master_SSL_Allowed: No
         Master_SSL_CA_File:
         Master_SSL_CA_Path:
            Master_SSL_Cert:
          Master_SSL_Cipher:
             Master_SSL_Key:
      Seconds_Behind_Master: NULL
1 row in set (0.00 sec)

It is important that you learn and understand these values. In this above case, replication is NOT running as indicated by Slave_IO_Running and Slave_SQL_Running.

This information is just an introduction as to what to look at. In my next lesson, I’ll spend more detail of the output of the various commands, as well as describe in greater detail the relationship of underlying files that are important for a working MySQL Replication environment.

Other References

Verifying MySQL Replication in Action
MySQL Replication Architecture

Has your blog been hacked?

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While not a MySQL topic, as most of my readers view my MySQL Blog, my WordPress blog has been hacked? Has yours?

Like many, I’m sure you may have read about it like at WordPress blogs under attack from hack attack but I was surprised when my custom permlinks did not work.

Being surprised I looked at Administrator accounts, and I found that there was one more number then being displayed in the list. I had to dig into the database to find the problem.

mysql> select * from wp_users where ID in (select user_id from wp_usermeta where meta_key = 'wp_capabilities' and meta_value like '%admin%');
+-----+-------------+------------------------------------+---------------+------------------------------+---------------------------+---------------------+---------------------+-------------+--------------+
| ID  | user_login  | user_pass                          | user_nicename | user_email                   | user_url                  | user_registered     | user_activation_key | user_status | display_name |
+-----+-------------+------------------------------------+---------------+------------------------------+---------------------------+---------------------+---------------------+-------------+--------------+
|   1 | admin       | $P$BHZFK/prDplb/W/024yrH49JvAmmCE. | ronald        | [email protected] | http://ronaldbradford.com | 2005-11-21 23:43:47 |                     |           0 | Ronald       |
| 127 | ronald      | $P$B..e75VtFsv9bUGj5H5NTiXXPQIitr1 | ronald        | [email protected]    | http://ronaldbradford.com | 2009-02-22 20:13:33 |                     |           0 | ronald       |
| 133 | ChaseKent87 | $P$Bl8cVSzBums33Md6u2PQtUVY2PPBHK. | chasekent87   |                              |                           | 2009-09-05 06:36:59 |                     |           0 | ChaseKent87  |
+-----+-------------+------------------------------------+---------------+------------------------------+---------------------------+---------------------+---------------------+-------------+--------------+
3 rows in set (0.00 sec)

mysql> delete from wp_users where ID=133;
mysql> delete from wp_usermeta where user_id=133;

However the damage has been done, and an update to the recommend 2.8.4 is unlikely to fix the data corruption.

Being a good DBA I have a nightly backup of my database. Being a diligent system administrator, I have not 1 copy, by 3 copies of my system, one on my web site and two offsite.

The problem is I don’t keep older backups of my data, only a day old version.

SQL Analysis with MySQL Proxy – Part 2

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As I outlined in Part 1 MySQL Proxy can be one tool for performing SQL analysis. The impact with any monitoring is the art of monitoring will affect the results, in this case the performance. I don’t recommend enabling this level of detailed monitoring in production, these techniques are designed for development, testing, and possibly stress testing.

This leads to the question, how do I monitor SQL in production? The simple answer to this question is, Sampling. Take a representative sample of your production system. The implementation of this depends on many factors including your programming technology stack, and your MySQL topology.

If for example you are using PHP, then defining MySQL proxy on a production system, and executing firewall rules to redirect incoming 3306 traffic to 4040 for a period of time, e.g. 2 seconds can provide a wealth of information as to what’s happening on the server now. I have used this very successfully in production as an information gathering an analysis tool. It is also reasonably easy to configure, execute and the impact on any failures for example are minimized due to the sampling time.

If you run a distributed environment with MySQL Slaves, or many application servers, you can also introduce sampling to a certain extent as these specific points, however like scaling options, it is key to be able to handle and process the write load accurately.

Another performance improvement is to move processing of the gathered information in MySQL proxy to a separate thread or process, removing this work from the thread execution path and therefore increasing the performance. I’m interested to explore the option of passing this information off to memcached or gearman and having MySQL proxy simply capture the packet information and distributing the output. I have yet to see how memcached and/or gearman integrate with the Lua/C bindings. If anybody has experience or knowledge I would be interested to know more.

It is interesting to know that Drizzle provides a plugin to send this level of logging information to gearman automatically.

Seeking public data for benchmarks

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I have several side projects when time permits and one is that of benchmarking various MySQL technologies (e.g. MySQL 5.0,5.1,5.4), variants (e.g. MariaDB, Drizzle) and storage engines (e.g. Tokutek, Innodb plugin) and even other products like Tokyo Cabinet which is gaining large implementations.

You have two options with benchmarks, the brute force approach such as Sysbench, TPC, sysbench, Juice Benchmark, iibench, mysqlslap, skyload. I prefer the realistic approach however these are always on client’s private data. What is first needed is better access to public data for benchmarks. I have compiled this list to date and I am seeking additional sources for reference.

Of course, the data is only the starting point, having representative transactions and queries to execute and a framework to execute and a reporting module are also necessary. The introduction of Lua into Sysbench may now be a better option then my tool of choice mybench which I use simply because I can configure, write and deploy generally for a client in under 1 hour.

If anybody has other good references to free public data that’s easily loadable into MySQL please let me know.

Getting started with Gearman

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Gearman is an open source generic framework for distributed processing. At OSCON 2009 I attended the Gearman: Build Your Own Distributed Platform in 3 Hours tutorial.

While it’s very easy to install Gearman, and follow the first example, if you missed the all important additional PHP steps listed on just one slide you may be left with the “‘Class ‘GearmanClient’ not found” error.

The following are detailed instructions for the installation and configuration of Gearman and PHP on Ubuntu 9.04 Jaunty.

Add the Drizzle PPA to get pre-packaged versions of Gearman.

cp /etc/apt/sources.list /etc/apt/sources.list.orig
echo "deb http://ppa.launchpad.net/drizzle-developers/ppa/ubuntu intrepid main
deb-src http://ppa.launchpad.net/drizzle-developers/ppa/ubuntu intrepid main" >> /etc/apt/sources.list
apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 06899068
apt-get update

Get the gearman packages

apt-get install -y gearman gearman-job-server gearman-tools libgearman1 libgearman-dev libgearman-dbg libgearman-doc

Get the German PHP extension.

wget http://pecl.php.net/get/gearman-0.4.0.tgz
tar xvfz gearman-0.4.0.tgz
cd gearman-0.4.0/
phpize
./configure
make
make install

If phpize is not available then you are missing the development packages.

$ apt get php5-dev

You also configure PHP to load the extension. This will vary on different Linux environments. In this case.

echo 'extension="gearman.so"' >>/etc/php5/cli/php.ini

Verify the PHP Gearman extension is configured.

$ php --info | grep gearman
gearman
gearman support => enabled
libgearman version => 0.8

Now you are ready for working with the Gearman PHP examples.

Setting up sysbench with MySQL & Drizzle

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Sysbench is a open source product that enables you to perform various system benchmarks including databases. Drizzles performs regression testing of every trunk revision with a branched version of sysbench within Drizzle Automation.

A pending branch https://code.launchpad.net/~elambert/sysbench/trunk_drizzle_merge by Eric Lambert now enables side by side testing with MySQL and Drizzle. On a system running MySQL and Drizzle I was able install this sysbench branch with the following commands.

cd bzr
bzr branch lp:~elambert/sysbench/trunk_drizzle_merge
cd trunk_drizzle_merge/
./autogen.sh
./configure
make
sudo make install

Running the default lua tests supplied required me to ensure drizzle was in my path and that I created the ‘sbtest’ schema. I’ll be sure it add that checking to my future developed benchmark scripts.

$ cd sysbench/tests/db
$ sysbench --test=insert.lua --db_driver=drizzle prepare
sysbench v0.4.10:  multi-threaded system evaluation benchmark

FATAL: unable to connect to Drizzle server: 23
FATAL: error 0: Unknown database 'sbtest'
FATAL: failed to execute function `prepare': insert.lua:7: Failed to connect to the database

$ drizzle -e "create schema sbtest"
$ sysbench --test=insert.lua --db_driver=drizzle prepare
sysbench v0.4.10:  multi-threaded system evaluation benchmark

Creating table 'sbtest'...

And running produces the following results.

$ sysbench --num-threads=1 --test=insert.lua --db_driver=drizzle run
sysbench v0.4.10:  multi-threaded system evaluation benchmark

Running the test with following options:
Number of threads: 1

Threads started!

OLTP test statistics:
    queries performed:
        read:                            0
        write:                           10000
        other:                           0
        total:                           10000
    transactions:                        0      (0.00 per sec.)
    deadlocks:                           0      (0.00 per sec.)
    read/write requests:                 10000  (879.68 per sec.)
    other operations:                    0      (0.00 per sec.)

Test execution summary:
    total time:                          11.3678s
    total number of events:              10000
    total time taken by event execution: 11.3354s
    per-request statistics:
         min:                                  0.32ms
         avg:                                  1.13ms
         max:                                 68.74ms
         approx.  95 percentile:               2.41ms

Threads fairness:
    events (avg/stddev):           10000.0000/0.00
    execution time (avg/stddev):   11.3354/0.0

Rerunning the prepare also lacked some auto cleanup to allow for automated re-running.

$ sysbench --test=insert.lua --db_driver=drizzle prepare
Creating table 'sbtest'...
ALERT: Drizzle Query Failed: 1050:Table 'sbtest' already exists
FATAL: failed to execute function `prepare': insert.lua:57: Database query failed

For MySQL

$ sysbench --test=insert.lua --db_driver=mysql --mysql_table_engine=innodb prepare
sysbench v0.4.10:  multi-threaded system evaluation benchmark

Creating table 'sbtest'...

Unfortunately this doesn’t actually create the table in the right storage engine, I had to hack the code to ensure I was comparing InnoDB in each test.

$ sysbench --num-threads=1 --test=insert.l
ua --db_driver=mysql run
sysbench v0.4.10:  multi-threaded system evaluation benchmark

Running the test with following options:
Number of threads: 1

Threads started!

OLTP test statistics:
    queries performed:
        read:                            0
        write:                           10000
        other:                           0
        total:                           10000
    transactions:                        0      (0.00 per sec.)
    deadlocks:                           0      (0.00 per sec.)
    read/write requests:                 10000  (897.67 per sec.)
    other operations:                    0      (0.00 per sec.)

Test execution summary:
    total time:                          11.1399s
    total number of events:              10000
    total time taken by event execution: 11.1084s
    per-request statistics:
         min:                                  0.27ms
         avg:                                  1.11ms
         max:                                252.63ms
         approx.  95 percentile:               2.48ms

Threads fairness:
    events (avg/stddev):           10000.0000/0.00
    execution time (avg/stddev):   11.1084/0.00

Armed with a working environment I can now write some more realistic production like tests in Lua.

configure: error: mysql_config executable not found

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If your compiling a product that includes a dependency of MySQL, you can easily get the error

configure: error: mysql_config executable not found

I generally don’t see this problem, because I use MySQL binary tar files, however if you use MySQL packages, such as Ubuntu, you can easily miss the required dependency.

My currently installed MySQL packages on this Ubuntu machine are:

$ sudo dpkg -l | grep mysql
ii  libdbd-mysql                               0.8.2-1-4.1                               MySQL database server driver for libdbi
ii  libdbd-mysql-perl                          4.008-1                                   A Perl5 database interface to the MySQL data
ii  libmysqlclient15off                        5.1.30really5.0.75-0ubuntu10.2            MySQL database client library
ii  libmysqlclient16                           5.1.31-1ubuntu2                           MySQL database client library
ii  libqt4-sql-mysql                           4.5.0-0ubuntu4.1                          Qt 4 MySQL database driver
ii  mysql-client-5.1                           5.1.31-1ubuntu2                           MySQL database client binaries
ii  mysql-common                               5.1.30really5.0.75-0ubuntu10.2            MySQL database common files
ii  mysql-server-5.1                           5.1.31-1ubuntu2                           MySQL database server binaries
ii  php5-mysql                                 5.2.6.dfsg.1-3ubuntu4.1                   MySQL module for php5

The missing link is the development version of the libmysqlclient library.

sudo apt-get install libmysqlclient15-dev

Understanding Different MySQL Index Implementations

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It is important to know and understand that while indexing columns in MySQL will generally improve performance, using the appropriate type of index can make a greater impact on performance.

There are four general index types to consider when creating an appropriate index to optimize SQL queries.

  • Column Index
  • Concatenated Index
  • Covering Index
  • Partial Index

For the purpose of this discussion I am excluding other specialized index types such as fulltext, spatial and hash in memory engine.

Example Table

For the following examples, I will use this test table structure.

DROP TABLE IF EXISTS t1;
CREATE TABLE t1(
  id INT UNSIGNED NOT NULL AUTO_INCREMENT,
  user_name VARCHAR(20) NOT NULL,
  first_name VARCHAR(30) NOT NULL,
  last_name VARCHAR(30) NOT NULL,
  external_id INT UNSIGNED NOT NULL,
  country_id SMALLINT UNSIGNED NOT NULL,
  PRIMARY KEY(id)
) ENGINE=InnoDB;

Column Index

Quite simply, you have an index on a single column to help with performance. For example, if you were to query your data on external_id, without an index the system will need to read all data pages and then sequential scan pages to identify matching records. As there is no information known about how many rows satisfy the criteria, all data must be read. You can confirm this with the QEP.

SELECT id, user_name
FROM   t1
WHERE external_id = 1;

By adding an index to external_id, the query is optimized to only look at records that satisfy your criteria.

ALTER TABLE t1
  ADD INDEX (external_id);

Concatenated Index

I often see many single column indexes on tables, when these are simply not needed, and generally will be not used. This is easily identified when looking at the QEP and seeing multiple 3,4,5 possible keys.
You need to also consider in your MySQL Index theory, that in general only one index is used for each table in a MySQL query. There are a few exceptions however these are rare.

A concatenated index uses multiple columns. Let’s look a modified version of our query.

SELECT id, user_name
FROM   t1
WHERE external_id = 1
AND      country_id = 5;

The original external_id index will be used, however if we create a concatenated index on external_id and country_id we improve the query path.

ALTER TABLE t1
  DROP INDEX external_id,
  ADD INDEX (external_id, country_id);

What about an index on country_id, external_id? If your access to your data always includes these two columns, you can consider swapping the columns based on the cardinality. However, if you have queries that search on external_id or external_id and country_id, then creating an index on country_id, external_id will not be used.

Tip In the QEP look at the key length to determine how effective concatenated indexes are.

Covering Index

A covering index as the name describes covers all columns in a query. The benefit of a covering index is that the lookup of the various Btree index pages necessary satisfies the query, and no additional data page lookups are necessary.

If we revisit our earlier example, by modifying the external_id index, and create a concatenated index on external_id and user_name we actually satisfy

ALTER TABLE t1
  DROP INDEX external_id,
  ADD INDEX (external_id, user_name);

SELECT id, user_name
FROM   t1
WHERE external_id = 1;

With MySQL, the QEP will indicate in Extra, ‘Using Index’. This is not a reference to the index actually being used, but the index satisfies all requirements of the query.

Partial Index

The final type is the partial index. This is a MySQL feature which allows you specify a subset of a column for the index.

Let’s say we query data and allow pattern matching on last name.

SELECT id, first_name, last_name, user_name
FROM   t1
WHERE last_name like 'A%'

We should add an index to last_name to improve performance.

ALTER TABLE t1
  ADD INDEX (last_name);

Depending on the average length of data in last_name (you can use PROCEDURE ANALYSE as a quick tool to sample this), creating a partial index may greatly reduce the size of the index, and minimize the additional data lookups required.

ALTER TABLE t1
  DROP INDEX last_name,
  ADD INDEX (last_name(10));

In this example, you would want to investigate the size of the index, the improvement, and then the amount of additional reads necessary for sample queries. If your accessed data is generally hot, then the benefit of a smaller index will not be impacted by additional data seeks.

Conclusion

As with any performance tuning, sufficient analysis and before and after testing is necessary for your specific environment.

Some future topics on indexes not discussed here include:

  • Using UNIQUE Indexe
  • The impact of NULL columns and values on indexes
  • Eliminating filesort by using indexes
  • The affect of too many indexes
  • Index cardinality

You need to also consider in your MySQL Index theory, that in general only one index is used for each table in a MySQL query. There are a few exceptions however these are rare.

I common question I am also asked is about function based indexes? MySQL provides no means to use a scalar function against a column in an index.

mysql.com and related sites are down

by

I tried to go to mysql.com and Planet MySQL over my lunch break at OSCON 2009 to find the websites are down. Seems from conversions with fellow Drizzle colleagues this has been down for some time.

What does your site look like when your system is unavailable or down?

This is a question I ask clients. What redundancy do you have in place for DNS, for a site unavailable page, for a static copy of content?

I learned my first personal lesson several years ago when at The Planet, my server and 9,000 others were unavailable at least 40 hours due to explosion, fire at a data center. While I had copies of my site, and shared hosting options elsewhere, all DNS was also in the same unavailable data center. This was definitely a shortcoming of the Host Provider at the time.

For any commercial site, it is important that at least your have geographical redundancy for DNS. Let’s use mysql.com as an example investigation.

Identify DNS records

$ dig mysql.com

; < <>> DiG 9.4.3-P1 < <>> mysql.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER< <- opcode: QUERY, status: NOERROR, id: 63421
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 0

;; QUESTION SECTION:
;mysql.com.			IN	A

;; ANSWER SECTION:
mysql.com.		2839	IN	A	213.136.52.29

;; AUTHORITY SECTION:
mysql.com.		72	IN	NS	ns7.sun.com.
mysql.com.		72	IN	NS	ns8.sun.com.
mysql.com.		72	IN	NS	ns1.sun.com.
mysql.com.		72	IN	NS	ns2.sun.com.

;; ADDITIONAL SECTION:
ns1.sun.com.		86045	IN	A	192.18.128.11
ns2.sun.com.		86075	IN	A	192.18.99.5
ns7.sun.com.		86085	IN	A	192.18.43.15
ns8.sun.com.		86093	IN	A	192.18.43.12

;; Query time: 2 msec
;; SERVER: 10.10.16.2#53(10.10.16.2)
;; WHEN: Wed Jul 22 14:18:11 2009
;; MSG SIZE  rcvd: 183

I am definitely no expert in networking, my understanding is your defined DNS server contain your primary information that is then delegated to servers worldwide.

These servers are up and running. Having no ping response is not an indicator the server not available.

mactaz:~ rbradfor$ ping -c 1 ns1.sun.com
PING ns1.sun.com (192.18.128.11): 56 data bytes
64 bytes from 192.18.128.11: icmp_seq=0 ttl=242 time=66.891 ms

--- ns1.sun.com ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 66.891/66.891/66.891/0.000 ms
mactaz:~ rbradfor$ ping -c 1 ns2.sun.com
PING ns2.sun.com (192.18.99.5): 56 data bytes
64 bytes from 192.18.99.5: icmp_seq=0 ttl=239 time=58.879 ms

--- ns2.sun.com ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 58.879/58.879/58.879/0.000 ms
mactaz:~ rbradfor$ ping -c 1 ns7.sun.com
PING ns7.sun.com (192.18.43.15): 56 data bytes
64 bytes from 192.18.43.15: icmp_seq=0 ttl=244 time=3.921 ms

--- ns7.sun.com ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 3.921/3.921/3.921/0.000 ms
mactaz:~ rbradfor$ ping -c 1 ns8.sun.com
PING ns8.sun.com (192.18.43.12): 56 data bytes
64 bytes from 192.18.43.12: icmp_seq=0 ttl=244 time=4.076 ms

--- ns8.sun.com ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 4.076/4.076/4.076/0.000 ms

They even appear to be in different locations which is good.

$ traceroute 192.18.128.11
traceroute to 192.18.128.11 (192.18.128.11), 64 hops max, 40 byte packets
 1  10.10.0.1 (10.10.0.1)  1.575 ms  0.882 ms  1.538 ms
 2  10.10.16.2 (10.10.16.2)  0.329 ms  0.366 ms  0.376 ms
 3  gateway.above.net (209.133.114.1)  1.567 ms  0.785 ms  0.863 ms
 4  ge-11-0-2.er1.sjc2.us.above.net (64.124.196.161)  1.386 ms  1.567 ms  1.214 ms
 5  xe-0-1-0.mpr4.sjc7.us.above.net (64.125.30.178)  2.177 ms  1.907 ms  1.873 ms
 6  above-att.sjc7.us.above.net (64.125.12.118)  5.361 ms  3.927 ms  3.717 ms
 7  cr2.sffca.ip.att.net (12.123.15.162)  66.434 ms  66.523 ms  66.694 ms
 8  cr2.la2ca.ip.att.net (12.122.31.133)  67.472 ms  66.008 ms  65.632 ms
 9  cr2.dlstx.ip.att.net (12.122.28.177)  66.003 ms  66.372 ms  66.723 ms
10  cr1.attga.ip.att.net (12.122.28.173)  66.472 ms  66.001 ms  66.908 ms
11  gar1.chlnc.ip.att.net (12.122.141.77)  66.139 ms  65.835 ms  65.892 ms
12  12.125.220.10 (12.125.220.10)  67.209 ms  66.569 ms  66.529 ms
13  cltea-ns-1.sun.com (192.18.128.11)  66.357 ms  66.756 ms  66.386 ms
mactaz:~ rbradfor$ traceroute 192.18.99.5
traceroute to 192.18.99.5 (192.18.99.5), 64 hops max, 40 byte packets
 1  10.10.0.1 (10.10.0.1)  1.159 ms  0.763 ms  0.704 ms
 2  10.10.16.2 (10.10.16.2)  0.298 ms  0.303 ms  0.290 ms
 3  gateway.above.net (209.133.114.1)  0.637 ms  0.784 ms  0.937 ms
 4  ge-11-0-2.er1.sjc2.us.above.net (64.124.196.161)  1.513 ms  1.743 ms  1.746 ms
 5  xe-0-1-0.mpr4.sjc7.us.above.net (64.125.30.178)  2.066 ms  1.417 ms  4.144 ms
 6  above-att.sjc7.us.above.net (64.125.12.118)  3.835 ms  3.374 ms  4.001 ms
 7  cr2.sffca.ip.att.net (12.123.15.162)  56.427 ms  56.191 ms  55.553 ms
 8  cr1.dvmco.ip.att.net (12.122.28.54)  55.819 ms  55.508 ms  55.442 ms
 9  gar1.dvmco.ip.att.net (12.122.144.37)  55.429 ms  55.406 ms  55.401 ms
10  12.125.159.146 (12.125.159.146)  59.293 ms  59.501 ms  59.237 ms
11  192.18.101.249 (192.18.101.249)  58.936 ms  59.099 ms  60.184 ms
12  brm-ea-ns-1.Sun.COM (192.18.99.5)  60.090 ms  59.285 ms  59.289 ms
mactaz:~ rbradfor$ traceroute 192.18.43.15
traceroute to 192.18.43.15 (192.18.43.15), 64 hops max, 40 byte packets
 1  10.10.0.1 (10.10.0.1)  1.070 ms  0.639 ms  0.639 ms
 2  10.10.16.2 (10.10.16.2)  0.323 ms  0.238 ms  0.242 ms
 3  gateway.above.net (209.133.114.1)  1.524 ms  2.697 ms  0.615 ms
 4  ge-11-0-2.er1.sjc2.us.above.net (64.124.196.161)  1.463 ms  1.510 ms  1.922 ms
 5  xe-0-1-0.mpr4.sjc7.us.above.net (64.125.30.178)  7.735 ms  2.136 ms  66.881 ms
 6  xe-0-0-0.mpr3.sjc7.us.above.net (64.125.27.85)  1.744 ms  3.131 ms  1.874 ms
 7  * above-level3.sjc7.us.above.net (64.125.13.242)  49.976 ms  2.078 ms
 8  ae-11-69.car1.SanJose1.Level3.net (4.68.18.3)  124.861 ms  206.837 ms  5.631 ms
 9  SUN-MICROSY.car1.SanJose1.Level3.net (4.53.16.50)  3.182 ms  3.579 ms  3.348 ms
10  192.18.44.18 (192.18.44.18)  4.168 ms  4.611 ms  4.146 ms
11  * * *
12  * * *
13  * *^C
mactaz:~ rbradfor$ traceroute 192.18.43.12
traceroute to 192.18.43.12 (192.18.43.12), 64 hops max, 40 byte packets
 1  10.10.0.1 (10.10.0.1)  1.206 ms  0.818 ms  0.879 ms
 2  10.10.16.2 (10.10.16.2)  0.348 ms  0.485 ms  0.465 ms
 3  gateway.above.net (209.133.114.1)  10.055 ms  1.911 ms  1.775 ms
 4  ge-11-0-2.er1.sjc2.us.above.net (64.124.196.161)  1.278 ms  0.963 ms  1.307 ms
 5  xe-0-1-0.mpr4.sjc7.us.above.net (64.125.30.178)  2.243 ms  2.004 ms  2.041 ms
 6  * xe-0-0-0.mpr3.sjc7.us.above.net (64.125.27.85)  2.016 ms  2.104 ms
 7  above-level3.sjc7.us.above.net (64.125.13.242)  2.143 ms  1.471 ms  2.106 ms
 8  ae-41-99.car1.SanJose1.Level3.net (4.68.18.195)  2.970 ms  3.103 ms ae-31-89.car1.SanJose1.Level3.net (4.68.18.131)  2.876 ms
 9  SUN-MICROSY.car1.SanJose1.Level3.net (4.53.16.50)  3.054 ms  3.414 ms  2.925 ms
10  192.18.44.18 (192.18.44.18)  3.721 ms  3.643 ms  3.622 ms
11  scaea-ns-1.sun.com (192.18.43.12)  4.350 ms  3.905 ms  4.188 ms

A traceroute of mysql.com shows it’s outside of the Sun network that at least the DNS servers are at.

$ traceroute 213.136.52.29
traceroute to 213.136.52.29 (213.136.52.29), 64 hops max, 40 byte packets
 1  10.10.0.1 (10.10.0.1)  1.243 ms  0.750 ms  0.844 ms
 2  10.10.16.2 (10.10.16.2)  0.397 ms  0.353 ms  0.413 ms
 3  gateway.above.net (209.133.114.1)  1.254 ms  1.021 ms  0.976 ms
 4  ge-11-0-2.er1.sjc2.us.above.net (64.124.196.161)  1.448 ms  0.933 ms  14.524 ms
 5  * xe-0-1-0.mpr4.sjc7.us.above.net (64.125.30.178)  1.734 ms  2.025 ms
 6  sjo-bb1-link.telia.net (213.248.94.29)  2.001 ms  1.942 ms  2.212 ms
 7  nyk-bb2-link.telia.net (80.91.254.176)  75.310 ms  81.628 ms  75.063 ms
 8  kbn-bb2-link.telia.net (80.91.254.90)  175.072 ms  175.445 ms  174.846 ms
 9  s-bb2-pos7-0-0.telia.net (213.248.65.30)  181.580 ms  181.930 ms  182.126 ms
10  s-b3-link.telia.net (80.91.253.226)  184.610 ms  198.216 ms  184.766 ms
11  bahnhof-110262-s-b3.c.telia.net (213.248.97.42)  182.919 ms  185.830 ms  184.827 ms
12  * * *
13  tsic2-gw.bahnhof.net (85.24.151.133)  186.588 ms  186.847 ms  188.352 ms
14  tsic3-gw.bahnhof.net (85.24.151.135)  183.782 ms  183.355 ms  184.660 ms
15  pio-dr1.pio-dr2.bahnhof.net (85.24.151.7)  186.142 ms  186.809 ms  186.723 ms
16  mysql-gw-sec-c.bahnhof.net (85.24.153.74)  183.821 ms  183.793 ms  183.597 ms
17  * * *
18  * * *
19  * * *
20  * * *
21  * * *

For such a significant open source product, I’m surprised that this level of complete unavailability without even a site unavailable page is surprising.

NOTE Further update. It’s been reported the site has been down now for 8+ hours.

Drizzle Query logging

by

Currently Drizzle offers three (3) separate query logging plugins. These plugins offer an extensible means of gathering all or selected queries and provide the foundation for a query analyser tool. Additional filtering includes selecting queries by execution time, result size, rows processed and by any given regular expression via PCRE.

During this tutorial I’ll be stepping though the various logging_query parameters which log SQL in a CSV format.

Confirm Logging Plugins

You can view the current ACTIVE plugins in Drizzle with the following SQL.

drizzle> select version();
+--------------+
| version()    |
+--------------+
| 2009.07.1097 |
+--------------+

drizzle> select * from information_schema.plugins where plugin_name like 'logging%';
+-----------------+----------------+---------------+--------------------------------------+---------------------------------+----------------+
| PLUGIN_NAME     | PLUGIN_VERSION | PLUGIN_STATUS | PLUGIN_AUTHOR                        | PLUGIN_DESCRIPTION              | PLUGIN_LICENSE |
+-----------------+----------------+---------------+--------------------------------------+---------------------------------+----------------+
| logging_gearman | 0.1            | ACTIVE        | Mark Atwood  mark @fallenpegasus.com | Log queries to a Gearman server | GPL            |
| logging_query   | 0.2            | ACTIVE        | Mark Atwood  mark @fallenpegasus.com | Log queries to a CSV file       | GPL            |
| logging_syslog  | 0.2            | ACTIVE        | Mark Atwood  mark @fallenpegasus.com | Log to syslog                   | GPL            |
+-----------------+----------------+---------------+--------------------------------------+---------------------------------+----------------+
3 rows in set (0.01 sec)

Logging all queries

You can define the following configuration variables to enable query logging.

/etc/drizzle/drizzled.cnf
[drizzled]
logging_query_enable=true
logging_query_filename=/var/log/drizzle/general.csv

You can confirm the settings with the following SHOW VARIABLES.

drizzle> show global variables like 'logging_query%';
+---------------------------------------+------------------------------+
| Variable_name                         | Value                        |
+---------------------------------------+------------------------------+
| logging_query_enable                  | ON                           |
| logging_query_filename                | /var/log/drizzle/general.csv |
| logging_query_pcre                    |                              |
| logging_query_threshold_big_examined  | 0                            |
| logging_query_threshold_big_resultset | 0                            |
| logging_query_threshold_slow          | 0                            |
+---------------------------------------+------------------------------+

This command showing queries to be logged.

$ cat /var/log/drizzle/general.csv
1248214561824590,1,1,"","select @@version_comment limit 1","Query",1248214561824590,1240,1240,1,00,0
1248214582588346,1,3,"","show global variables like 'logging_query%'","Query",1248214582588346,1958,1706,6,62,0

Unfortunately the log does not yet provide a header. You need to turn the source code to get a better description of the columns.

      snprintf(msgbuf, MAX_MSG_LEN,
               "%"PRIu64",%"PRIu64",%"PRIu64","%.*s","%s","%.*s","
               "%"PRIu64",%"PRIu64",%"PRIu64",%"PRIu64",%"PRIu64
               "%"PRIu32",%"PRIu32"n",
               t_mark,
               session->thread_id,
               session->query_id,
               // dont need to quote the db name, always CSV safe
               dbl, dbs,
               // do need to quote the query
               quotify((unsigned char *)session->query,
                       session->query_length, qs, sizeof(qs)),
               // command_name is defined in drizzled/sql_parse.cc
               // dont need to quote the command name, always CSV safe
               (int)command_name[session->command].length,
               command_name[session->command].str,
               // counters are at end, to make it easier to add more
               (t_mark - session->connect_utime),
               (t_mark - session->start_utime),
               (t_mark - session->utime_after_lock),
               session->sent_row_count,
               session->examined_row_count,
               session->tmp_table,
               session->total_warn_count);

The important parts of this information include:

  • getmicrotime – 1248214561824590
  • Session Id – 1
  • Query Id – 1
  • Schema
  • The Query: “show global variables like ‘logging_query%'”
  • The Query type “Query”
  • Time session connected – 1248214582588346
  • The total execution time – 1958
  • The execution time after necessary locks – 1706
  • The number of rows returned – 6
  • The number of rows examined – 6
  • The number of temporary tables used – 2
  • The total warning count – 0

I also found what I believe is a formatting problem logged as Bug #402831.

You can enable logging dynamically.

drizzle> select now();
+---------------------+
| now()               |
+---------------------+
| 2009-07-22 02:14:31 |
+---------------------+
1 row in set (0 sec)

drizzle> set global logging_query_enable=true;
Query OK, 0 rows affected (0 sec)

drizzle> select curdate();
+------------+
| curdate()  |
+------------+
| 2009-07-22 |
+------------+
1 row in set (0 sec)

drizzle> set global logging_query_enable=false;
Query OK, 0 rows affected (0 sec)

drizzle> select now();
+---------------------+
| now()               |
+---------------------+
| 2009-07-22 02:14:54 |
+---------------------+
1 row in set (0 sec)

1248228876381645,4,3,"","set global logging_query_enable=true","Query",1248228876381645,761,761,0,00,0
1248228886866882,4,4,"","select curdate()","Query",1248228886866882,105,105,1,00,0

I was not able to alter the logging_query_filename dynamically. Need to confirm with the development team about this functionality for the future.

drizzle> set global logging_query_filename='/tmp/general.csv';
ERROR 1238 (HY000): Variable 'logging_query_filename' is a read only variable

Logging slow queries

If you just wanted to emulate the MySQL slow query log, with a long_query_time of 1 second, you could use the following.

/etc/drizzle/drizzled.cnf
[drizzled]
logging_query_enable=true
logging_query_filename=/var/log/drizzle/slow.csv
logging_query_threshold_slow=1000000

Drizzle supports the ability to set a threshold in microseconds.

NOTE: I wanted to demonstrate this using the popular MySQL SLEEP() function, only to find this is currently not available in Drizzle. This is an ideal example of a simple UDF that can be written and added to Drizzle. One day if I ever have the time.

Here is some sample output using queries > 1 second.

1248216457856195,1,43,"test","insert into numbers   select...","Query",1248216457856195,2160680,2160620,0,26214420,0
1248216462738678,1,45,"test","insert into numbers   select...","Query",1248216462738678,4530327,4530263,0,52428821,0
1248216472430813,1,47,"test","insert into numbers   select...","Query",1248216472430813,8990965,8990890,0,104857622,0
1248216473592812,1,48,"test","select @counter := count(*) from numbers","Query",1248216473592812,1152319,1152257,1,104857622,0

Logging by threshold

Drizzle Query Logging provides the ability to return results by 2 thresholds, the number of rows in the result, and the number of rows examined by the storage engine.

/etc/drizzle/drizzled.cnf
[drizzled]
logging_query_enable=true
logging_query_filename=/var/log/drizzle/slow.csv
logging_query_threshold_big_resultset=100

1248216631322097,1,5,"test","select * from numbers limit 100","Query",1248216631322097,281,217,100,1002,0
1248216642763174,1,6,"test","select * from numbers limit 101","Query",1248216642763174,268,215,101,1012,0

/etc/drizzle/drizzled.cnf
[drizzled]
logging_query_enable=true
logging_query_filename=/var/log/drizzle/slow.csv
logging_query_threshold_big_examined=1000

1248216785430588,1,6,"test","select * from numbers limit 1000","Query",1248216785430588,8055,7983,1000,10002,0
1248216800327928,1,7,"test","select count(*) from numbers","Query",1248216800327928,1041322,1041222,1,10485762,0

Logging by pattern

The final option is to return queries that match a given pattern via a PCRE expression.



/etc/drizzle/drizzled.cnf
[drizzled]
logging_query_enable=true
logging_query_filename=/var/log/drizzle/slow.csv
logging_query_pcre=now



drizzle> select now();
+---------------------+
| now()               |
+---------------------+
| 2009-07-22 03:24:32 |
+---------------------+
1 row in set (0 sec)

drizzle> select curdate();
+------------+
| curdate()  |
+------------+
| 2009-07-22 |
+------------+
1 row in set (0 sec)

drizzle> select "now";
+-----+
| now |
+-----+
| now |
+-----+
1 row in set (0 sec)

drizzle> select "know how";
+----------+
| know how |
+----------+
| know how |
+----------+
1 row in set (0 sec)



1248233072792211,3,2,"","select now()","Query",1248233072792211,154,154,1,00,0
1248233085807520,3,4,"","select "now"","Query",1248233085807520,92,92,1,00,0
1248233096659018,3,5,"","select "know how"","Query",1248233096659018,75,75,1,00,0



Another example using a pattern.


/etc/drizzle/drizzled.cnf
[drizzled]
logging_query_enable=true
logging_query_filename=/var/log/drizzle/slow.csv
logging_query_pcre="[0-9][0-9][0-9]"



drizzle> select 1;
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0 sec)

drizzle> select 11;
+----+
| 11 |
+----+
| 11 |
+----+
1 row in set (0 sec)

drizzle> select 111;
+-----+
| 111 |
+-----+
| 111 |
+-----+
1 row in set (0 sec)

drizzle> select 1111;
+------+
| 1111 |
+------+
| 1111 |
+------+
1 row in set (0 sec)

drizzle> select 11+22;
+-------+
| 11+22 |
+-------+
|    33 |
+-------+
1 row in set (0 sec)



1248233336460373,3,4,"","select 111","Query",1248233336460373,79,79,1,00,0
1248233339300429,3,5,"","select 1111","Query",1248233339300429,82,82,1,00,0



Unfortunately it seems that this variable is also not configurable dynamically at this time.


drizzle> set global logging_query_pcre="now";
ERROR 1238 (HY000): Variable 'logging_query_pcre' is a read only variable



This is definitely an improvement over current MySQL logging.


What's new in MySQL 5.4.1
 

 by   
Absolutely nothing?


5.4.0 was released with a change in the MySQL Binary distributions, delivering only 1 64bit Linux platform and two Sun Solaris platforms. This was officially announced on April 21 2009  however the 5.4.0 Release Notes state 05 April 2009.  So it’s not a big deal, but consistency would be nice.


I’ve seen in a few posts 5.4.1, so I decided to try it out. Spending the time to read what’s changed in 2 months with the 5.4.1 Release Notes before I go downloading and installing, you read.


This release does not differ from 5.4.0 except that binary distributions are available for all MySQL-supported platforms.


Is this going to be the new policy from Sun?  Release for Solaris platforms first, then later release for other platforms?


What to do at 3:25am
 

 by   
Look at MySQL bug reports of course?  Well actually I’m writing multiple blog posts, and I was confirming additional reference sources and links when I came across MySQL Bug #29847 – Large CPU usage of InnoDB crash recovery with a big buf pool.


Taking the time to actually read the information exchange I stumble upon.


[8 Jun 23:29] liz drachnik

Hello Heikki -

In order for us to continue the process of reviewing your contribution to MySQL - We need
you to review and sign the Sun|MySQL contributor agreement (the "SCA")

The process is explained here:

http://forge.mysql.com/wiki/Sun_Contributor_Agreement

Getting a signed/approved SCA on file will help us facilitate your contribution-- this
one, and others in the future.

Thank you !

Liz Drachnik  - Program Manager - MySQL



Oops. Well it made me laugh out loud for so many reasons. First your talking to the creator of InnoDB, a part of MySQL for at least 5+ years. Second, there is clearly an agreement between Oracle and MySQL already for the incorporation of InnoDB in the current builds, but mostly because at this late stage of probably Oracle acquisition (which side note has seemed too quite for too long) it seems rather a mute point to be chasing up paperwork.


Fortunately sanity obviously prevailed, unfortunately the public record persists. Still, humor is always good.


[9 Jun 18:04] Liz Drachnik

Please disregard the previous request for an SCA.
thank you



Never let your binlog directory fill up
 

 by   
Recently with a client while running a number of disaster recovery tests I came across a nasty situation which was not part of the original plan and provided a far worse disaster situation then expected.


I should preface this condition with some of the environment conditions.


    

  • MySQL 5.0 Enterprise 5.0.54
    • 

  • RHEL 5 64bit
    • 

  • Master and 2 Slaves
    • 

  • MySQL Data and MySQL Binary Logs/MySQL Error Logs are on separate disk partitions
    • 



While running stress tests under high load, we tested the filling of partition containing the logs. This partition included the binary log and MySQL error log.


The observed output was.


    

  • An error message was written to the MySQL error log. See below.
    • 

  • Application throughput dropped, but did not stop.
    • 

  • Binary logs stopped occurring.
    • 

  • MySQL proactively stopped logging but continued to process transactions.
    • 



The end result was:


    

  • The error log was ultimately truncated after reboot, so if the information was not captured while this was in action, this important messages would be lost.
    • 

  • The primary slave used for read scalability and the secondary slave used for backups are now unusable.
    • 

  • The backup and recovery process using slaves and point in time recovery via binary logs is not unusable.
    • 

  • The three backup methods in use for the client are ineffective. It was necessary to disable access to the Master, take a full backup, and then sync the slaves from this copy.
    • 



090710 19:01:25 [ERROR] /opt/mysql/bin/mysqld: Disk is full writing '/mysqllog/binlog/hostname-3306-bin.000020'
     (Errcode: 28). Waiting for someone to free space... Retry in 60 secs
090710 19:01:46 [ERROR] Error writing file '/mysqllog/slow_log/hostname_3306_slow_queries.log' (errno: 1)
090710 19:02:25 [ERROR] Error writing file '/mysqllog/binlog/hostname-3306-bin' (errno: 28)
090710 19:02:25 [ERROR] Could not use /mysqllog/binlog/hostname-3306-bin for logging (error 28).
    Turning logging off for the whole duration of the MySQL server process. 
    To turn it on again: fix the cause, shutdown the MySQL server and restart it.



Updated


I discuss in detail the options for the MySQL error log including recommendations for the MySQL error log file location in Monitoring MySQL – The error log


Understanding more InnoDB MVCC
 

 by   
As I had written earlier in  Understanding InnoDB MVCC, I am trying to understand why InnoDB is taking a lock on data during an UPDATE when I do not expect this to happen.


Not wanting to go looking at the InnoDB source code to understand the problem, I’m endeavouring to possibly use existing MySQL monitoring to try and understand the problem better. In this case, I’m going to investigate SHOW ENGINE INNODB STATUS first.  An old but still relevant article for reference is SHOW INNODB STATUS walk through. The MySQL High Performance book is also a good starting reference.


I’ve just installed 5.1.36 on a new Linux 64 bit laptop for this test.


For now all I’ve done is ensure the innodb_buffer_pool_size is sufficient to hold the entire table in memory.


So what happens in the 21.5 seconds these queries took to run.


–thread 1


mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)

mysql> update numbers
    -> set f2 = f2 +200
    -> where id between 1 and 1000000; commit;
Query OK, 1000000 rows affected (21.50 sec)
Rows matched: 1000000  Changed: 1000000  Warnings: 0
Query OK, 0 rows affected (0.02 sec)



–thread 2


Query OK, 0 rows affected (0.00 sec)

mysql> update numbers
    -> set f2 = f2 +300
    -> where id between 1000001 and 2000000; commit;
Query OK, 1000000 rows affected (20.06 sec)
Rows matched: 1000000  Changed: 1000000  Warnings: 0
Query OK, 0 rows affected (0.02 sec)



In SHOW ENGINE INNODB STATUS I sampled 1718 unique times. Probably not the best approach but it did highlight some things.


The overall state of the main Innodb thread process cycled though states including sleeping, making checkpoint, flushing log, waiting for server activity, purging and reserving kernel mutex.


     49 Main thread process no. 5489, id 139872150796624, state: flushing log
    709 Main thread process no. 5489, id 139872150796624, state: making checkpoint
      1 Main thread process no. 5489, id 139872150796624, state: purging
      2 Main thread process no. 5489, id 139872150796624, state: reserving kernel mutex
    956 Main thread process no. 5489, id 139872150796624, state: sleeping
      1 Main thread process no. 5489, id 139872150796624, state: waiting for server activity



I was surprised to see making checkpoint here.  I’ve actually run this monitoring on two separate servers, both running 5.1.x and both times this occured.   On this test machine, I also saw an increase in the flush list, and pending checkpoint writes to confirm this.  I’ve tried in the past to monitor this closely, so this test actually will be useful for a different problem analysis at a later time.


Some 3800 OS Waits (that’s context switches) indicates some critical code need to use a mutex. These mutexes listed in the Semaphores section occured in multiple areas including:


      4 Mutex at 0x1684b08 created file mem/mem0pool.c line 206, lock var 0
     61 Mutex at 0x7f369033e2b8 created file srv/srv0srv.c line 875, lock var 0
      1 Mutex at 0x7f36903408b8 created file fil/fil0fil.c line 1313, lock var 1
     22 Mutex at 0x7f3690340cb8 created file buf/buf0buf.c line 597, lock var 0
      5 Mutex at 0x7f36903410e0 created file btr/btr0sea.c line 139, lock var 0
      1 Mutex at 0x7f36903410e0 created file btr/btr0sea.c line 139, lock var 1
     21 Mutex at 0x7f3690341910 created file log/log0log.c line 738, lock var 0
     85 Mutex at 0x7f3690341910 created file log/log0log.c line 738, lock var 1
      8 Mutex at 0x7f36903508c0 created file trx/trx0rseg.c line 147, lock var 0
    232 Mutex at 0x7f36903508c0 created file trx/trx0rseg.c line 147, lock var 1



One transaction waited only a little more then 1 second, indicated by 58 samples.


---TRANSACTION 0 1327, ACTIVE 22 sec, process no 5489, OS thread id 139872177113424 fetching rows
mysql tables in use 1, locked 1
LOCK WAIT 2008 lock struct(s), heap size 292848, 1002005 row lock(s), undo log entries 1000000
MySQL thread id 66, query id 11435 localhost root Updating
update numbers
set f2 = f2 +200
where id between 1 and 1000000
------- TRX HAS BEEN WAITING 1 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 0 page no 2612 n bits 568 index `PRIMARY` of table `test`.`numbers` trx id 0 1327 lock_mode X waiting
Record lock, heap no 256 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
 0: len 4; hex 000f4241; asc   BA;; 1: len 6; hex 000000000530; asc      0;; 2: len 7; hex 00000000f20110; asc        ;; 3: len 4; hex 800f4241; asc   BA;; 4: len 4; hex 8005032c; asc    ,;;



And the blocker in this instance while waiting for this lock to be released was continuing to get row locks, and create undo log entries. That was to be expected.


963 lock struct(s), heap size 292848, 979851 row lock(s), undo log entries 977891
1979 lock struct(s), heap size 292848, 988001 row lock(s), undo log entries 986025
1989 lock struct(s), heap size 292848, 993013 row lock(s), undo log entries 991027



I doubled checked to ensure no other queries were inside the InnoDB queue.


      4 0 queries inside InnoDB, 0 queries in queue
    303 1 queries inside InnoDB, 0 queries in queue
   1411 2 queries inside InnoDB, 0 queries in queue



Only 12 of the 1718 samples showed any Pending asynchronous I/O writes, however there was a higher amount of pending buffer pool and log syncs. This is all to be expected.


This quick inspection, especially at 1am has not given me any answers. With greater information, the need for better understanding is required.


An important Drizzle/MySQL difference
 

 by   
There are many features that are similar in MySQL and Drizzle. There are also many that are not.


I’ve previously discussed topics like Datatypes and tables, SQL_MODE and SHOW.


A key difference in Drizzle is the definition of utf8 as 4 bytes, not 3 bytes as in MySQL. This combined with no other character sets leads to an impact on the length in keys supported in Innodb.


During a recent test with a client, I was unable to successfully migrated the schema and provide the same schema due to unique indexes defined for utf8 VARHAR(255) fields.


Here is the problem.


mysql> create table t1(c1 int unsigned not null auto_increment primary key, c2 varchar(255) not null, unique key (c2)) engine=innodb default charset latin1;
Query OK, 0 rows affected (0.05 sec)
mysql> create table t2(c1 int unsigned not null auto_increment primary key, c2 varchar(255) not null, unique key (c2)) engine=innodb default charset utf8;
Query OK, 0 rows affected (0.03 sec)
mysql> create table t3(c1 int unsigned not null auto_increment primary key, c2 varchar(256) not null, unique key (c2)) engine=innodb default charset utf8;
ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes



drizzle> create table t1(c1 int not null auto_increment primary key, c2 varchar(255) not null, unique key (c2)) engine=innodb default charset latin1;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your Drizzle server version for the right syntax to use near 'charset latin1' at line 1
drizzle> create table t1(c1 int not null auto_increment primary key, c2 varchar(255) not null, unique key (c2)) engine=innodb;
ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes



Only a maximum of 191 is now possible.


drizzle> create table t1(c1 int not null auto_increment primary key, c2 varchar(191) not null, unique key (c2)) engine=innodb;
Query OK, 0 rows affected (0.03 sec)
drizzle> create table t1(c1 int not null auto_increment primary key, c2 varchar(192) not null, unique key (c2)) engine=innodb;
ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes



The confusion over global and session status
 

 by   
I was trying to demonstrate to a client how to monitor queries that generate internal temporary tables.  With an EXPLAIN plan you see ‘Creating temporary’.  Within MySQL you can use the SHOW STATUS to look at queries that create temporary tables.


There is the issue that the act of monitoring impacts the results, SHOW STATUS actually creates a temporary table. You can see in this example.


mysql> select version();
+-----------------+
| version()       |
+-----------------+
| 5.1.31-1ubuntu2 |
+-----------------+
1 row in set (0.00 sec)

mysql> show global status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 48    |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 155   |
+-------------------------+-------+
3 rows in set (0.00 sec)

mysql> show global status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 48    |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 156   |
+-------------------------+-------+
3 rows in set (0.00 sec)



What has perplexed me in the past, and I can’t explain is that SHOW SESSION STATUS for this example does not increment.  It’s confusing to tell a client to use SHOW SESSION STATUS for SQL statements, but the behavior is different with SHOW GLOBAL STATUS. For example, no increment.


mysql> show session status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 0     |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 2     |
+-------------------------+-------+
3 rows in set (0.00 sec)

mysql> show session status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 0     |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 2     |
+-------------------------+-------+
3 rows in set (0.00 sec)



Let’s look at a query that creates a temporary table.


mysql> explain select t1.* from t1,t2 where t1.c1 = t2.c2 order by t2.c2, t1.c1;
+----+-------------+-------+------+---------------+------+---------+------+------+---------------------------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra                           |
+----+-------------+-------+------+---------------+------+---------+------+------+---------------------------------+
|  1 | SIMPLE      | t1    | ALL  | NULL          | NULL | NULL    | NULL |    3 | Using temporary; Using filesort |
|  1 | SIMPLE      | t2    | ALL  | NULL          | NULL | NULL    | NULL |    3 | Using where; Using join buffer  |
+----+-------------+-------+------+---------------+------+---------+------+------+---------------------------------+
2 rows in set (0.03 sec)



If we use session status we get an increment of 1.


mysql> show session status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 0     |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 2     |
+-------------------------+-------+
3 rows in set (0.00 sec)

mysql> show session status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 0     |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 2     |
+-------------------------+-------+
3 rows in set (0.00 sec)

mysql> select SQL_NO_CACHE t1.* from t1,t2 where t1.c1 = t2.c2 order by t2.c2, t1.c1;
Empty set (0.00 sec)

mysql> show session status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 0     |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 3     |
+-------------------------+-------+
3 rows in set (0.00 sec)




If we use global status, in this case it’s and idle server so I know there is no other activity, however in a real world situation that isn’t possible.



mysql> show global status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 48    |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 171   |
+-------------------------+-------+
3 rows in set (0.00 sec)

mysql> select SQL_NO_CACHE t1.* from t1,t2 where t1.c1 = t2.c2 order by t2.c2, t1.c1;
Empty set (0.00 sec)

mysql> show global status like 'created_tmp%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 48    |
| Created_tmp_files       | 5     |
| Created_tmp_tables      | 173   |
+-------------------------+-------+
3 rows in set (0.00 sec)



Benchmarking Drizzle with MyBench(DBD::drizzle)
 

 by   
With thanks to  Patrick Galbraith and his DBD::drizzle 0.200 I am now able to test client benchmarks side by side with MySQL and Drizzle.


For simple benchmarking with clients, generally when I have little time, I use a simple Perl framework mybench. I was able to change just the connection string and run tests.


The diff of my two scripts where:


---
> my $user      = $opt{u} || "appuser";
> my $pass      = $opt{p} || "password";
> my $port      = $opt{P} || 3306;
> my $dsn       = "DBI:mysql:$db:$host;port=$port";
---
< my $user      = $opt{u} || "root";
< my $pass      = $opt{p} || "";
< my $port      = $opt{P} || 4427;
< my $dsn       = "DBI:drizzle:$db:$host;port=$port";
---



It's too early to tell what improvement Drizzle will make. Just running my first test with single and multi thread tests shows an improvement in all figures in Drizzle via MySQL, however I will need to run this on various different versions of MySQL including the latest 5.0 to confirm.


MiFi Installation woes
 

 by   
As I mentioned in MiFi Introduction I took the plunge and purchased a Verizon MiFi.  I got this under a 2 year contract for $149.99 and $59.99 per month for 5GB of traffic.


While happy to have a new tech toy, the installation and use of, well that was a painful experience I’d rather not have to endure.  Unfortunately I didn’t document all steps with screen shots so I will need to describe what I have.


While it stated the device worked with a Mac, it was clearly not as simple as the instructions stated.


    

  1. The first problem is, you can’t use the device until you activate it. You can’t activate it unless you already have Internet Access. 
    2. 

  2. The Tips, hits and shortcuts manual also states “VZAccess Manager Installation”, … connect device …, VZAccess installer auto-launches and the drivers will install automatically.  You have to read one page further before you get “Mac customers are not required to use VZAccess Manager to use their device”.  First, you do have to install the software to use the device (for the first time), there seems no way around that, and second, it does not auto-launch.
    3. 

  3. Trying to install I read the instructions, “connect to a USB Port, … auto-launches”. This doesn’t happen.  Opening in Finder, hoping for an attached device no luck? Now what.
    4. 

  4. One page further, under Mac OS/X Users, the section that states “not required to use…” also includes a point stating that activation requires MAC OS X 10.4.0 or higher and WWAN Support Update 1.0.  It would be nice if you included this as Pre-Requistes in your documentation so it reads chronologically. The docs state this is a free download.
    5. 

  5. So I downloaded WWAN Support Update 1.0 from the apple web site, got to run it, and it states “Alert: This computer cannot use this update”. What the.   I did between my first two attempts to connect to the device, and now run a Software Update, so guessing it was in this because I know no easy way to confirm installed software on a Mac, I truck on.
    6. 

  6. The Important MiFI 2220 Connection Information
    7. 

     page, shown below states  you can access the MiFi Admin Portal at http://192.168.1.1.  See Exhibit 1 below. I try that and I get the admin page, and it states “Not Activated”.  Did the store not activate the device, or is my attempt to blunder through these steps not correct
    

  7. Being frustrated I try Verizon Phone Support, the number 1800 922 0204, conveniently absent from the docs FYI. The automated system asks are you a customer, yes I am, what is your number? Well my number is on AT&T, this is just a broadband device, not a phone, trying that doesn’t work.  Then trying to get out of the automated system to get an operator an ordeal. Finally a real person.
    8. 

  8. Real person asks, what is your number, I explain the same story, then I decide to grab the receipt from the store, and I find in small print, under the device name on the receipt a number? Is that my number? I give that and lone behold, that’s the Cell number for the device.  Would be nice if they told you that.
    9. 

  9. I explain my problem, and I’m put on hold, and hold a second time, and more hold a third time to talk to a more technical person.
    10. 

  10. During this time, I go back over the steps I undertook and lone behold, there is now a device in my Finder. See Exhibit 2.  Did it take like 10 mins to find it or what? Perplexing. So while waiting for a tech person, I move on.
    11. 

  11. I see VZAccess Manager install package, I take this route, and following system reboot on the Mac, the software auto starts, and I’m prompted with the VZAccess Manager screen, See Exhibit 3.
    12. 

  12. In fine print down the bottom, Activation required. Nice if that was in big letters on first usage of software.  A few menu buttons on the top, and a Connect WWan button bottom right. Again, lack of clear UI here.
    13. 

  13. Clicking Connect WWAN goes though a number of steps, which unfortunately I didn’t keep, but at the end, I finally get an I’m activated message.
    14. 

  14. To get the device working however, there was also some pain. I had to disconnect my Internet connect, disable Wireless, and talk to the device directly via USB. I could then confirm I could access the Internet. I then had to remove the USB, enable Wireless and connect to get it to communicate via wireless.  The activation process needed the USB connection.
    15. 

  15. I’m finally online, now the need to plug this into my network. The device has an Admin portal at http://192.168.1.1. The first pain, I can’t access this because my Internal network, and multiple devices runs from my router at the same address. Seeing no way around this, I have to reconfigure my internal network, which was a pain.  No I can access the Admin Portal.  My goal is to change SSID, change password that’s printed on multiple pieces of paper, and also change the address.
    16. 

  16. On the admin portal, an input box, and button for Login. See Exhibit 4.  Nothing in the documentation on this login box, the Verizon tech didn’t know any information about this, so while they were researching I started randomly choosing logins.  It was weird that the input was a password protected input (e.g. *****) and there was no username/password.    I try the WiFi Password, seems to get truncated.  I try admin and lone behold I’m logged in.  That’s about as insecure as having nothing.
    17. 

  17. After all this, I’m finally able to configure the device. See Exhibit 5. I trust it will work when I’m next on the road.  Documentation get’s a fail, it’s unclear and incomplete.  There needs to be clear and seperate sections for Windows and Mac OS/X, and it needs to detail the installation process correctly and clearly, and probably with some screen prints.  I’m not a novice user, and I had difficulty with this process.

    18. 



Exhibit 1 – Important Information Page






Exhibit 2 – VZAccess Manager Finder




Exhibit 3 – VZAccess Manager




Exhibit 4 – MiFi Administration Portal Login




Exhibit 5 – MiFi Administration Change Password




MiFi Introduction
 

 by   
My first news of the Verizon MiFi  was via Twitter when @DonMacAskill said “Think my iPhone 3G via MiFi is faster than AT&T 3G. Should I carry both all the time now?”


A few reviews later such as Verizon Mifi: Personal Wi-Fi Coming this Month and Verizon MiFI a personal broadband bubble to believe in but this on my to buy tech list.  I presently have a Generation 1 Day 1 iPhone, so no 3G there.


In summary, this device is the size of 5 credit cards, weighs not much more then 5 credit cards and enables 3G Wireless broadband access on the Verizon network, and also doubles as a WiFi router for up to 5 other devices.


I have been procrastinating about getting one, the combination to do urgent work at midnight on the AirTrain and NY Subway (the above ground part), and then the following day on a client site when the internet was flaky convinced me to get one.


The purchase process was relatively straightforward, except the usual credit check woes for an Australian living in this country. The installation and use, well that’s another painful story to share.


Using statpack with SHOW STATUS
 

 by   
Mark Leith, on of the MySQL Support Team managers wrote some time ago a very nice utility I use often called Statpack.


My use of Statpack is very simple. Take two snaphots of SHOW GLOBAL STATUS and compare to produce a text based version of the statistics.


Over time I’ve grown to love it’s simplicity, but notice a number of shortcomings.  Being open source there is always the ability to modify, improve and give back. This post is more about detailing those little annoyances that I’d like to improve, or see improved. It is also a means to collate points into one location that I often forget about over time.


I welcome any input, and specifically help in this open source venture.


Here is my wish list that I can currently remember. I do plan to action, time permitting.


    

  1. In Statement Activity, the total percentages are great to determine Read/Write ratio, however the ratio is for the Total, not for the period. I’m not sure how best to present, but would be good to know.  See Exhibit 1 for a good example.
    2. 

  2. When sections are not used, e.g. all ZERO values, then suppress for ease of reading. See Exhibit 2 for examples of Prepared Statements and Query Cache, where a simple line like No Prepared Statements activity, or Query Cache not enabled.
    3. 

  3. Incorporating SHOW VARIABLES output.  If this is included in one file, then adding some information may be very valuable when reviewing these audit files. For example in the InnoDB Buffer Pool show innodb_buffer_pool_size. In InnoDB Log Files show innodb_log_file_size, innodb_log_files_in_group, innodb_log_buffer_size. This can be used in most sections. See Exhibit 3 for an example. 
    4. 

  4. Incorporate a Date/Time in the report output. Again for historical purposes, at worst it could be the time the output is generated, however this is only an approximation.  With SHOW GLOBAL STATUS output from my hourly.sh monitoring I include the following line before each SHOW STATUS output.   ‘| date_time                        | 090611.161511 |’.  Note to Drizzle Development team, please add date/time output to SHOW GLOBAL STATUS and SHOW GLOBAL VARIABLES.
    5. 

  5. Negative numbers. There are occurrences when negative numbers occur, due to the wrapping of status numbers. See Exhibit 4 for example.
    6. 

  6. Bug I’ve raised about divide by zero error when the same file (operator error) is specified.
    7. 



Exhibit 1 – Percentages on Period/Total


                     SELECT:           56,019                    28.11              281,456,428 (41.00%)
                     INSERT:          420,083                   210.78              325,218,748 (47.38%)
                     UPDATE:               46                     0.02                  138,206 (0.02%)
                     DELETE:           48,590                    24.38               79,170,553 (11.53%)



Exhibit 2 – Suppress sections


 ====================================================================================================
                                        Prepared Statements
====================================================================================================

   Prepared Statement Count:                0                     0.00                        0
                    PREPARE:                0                     0.00                        0
                    EXECUTE:                0                     0.00                        0
         DEALLOCATE PREPARE:                0                     0.00                        0
           Fetch Roundtrips:                0                     0.00                        0
             Send Long Data:                0                     0.00                        0

====================================================================================================
                                            Query Cache
====================================================================================================

       QCache Hits / SELECT:           0.00%
   QCache Hit/Qcache Insert:           0.00%
  Qcache Hits/Invalidations:           0.00%
                    SELECTs:       13,503,876                 3,798.56            4,298,170,239
           Query Cache Hits:                0                     0.00                        0
        Query Cache Inserts:                0                     0.00                        0
         Queries Not Cached:                0                     0.00                        0
    Cache Low Memory Prunes:                0                     0.00                        0
         Total Cache Blocks:                0                     0.00                        0
           Queries In Cache:                0                     0.00                        0
          Cache Free Blocks:                0                     0.00                        0




Exhibit 3 – Including Variables



====================================================================================================
                                         InnoDB Buffer Pool
====================================================================================================

Variables: innodb_buffer_pool_size = 10G, innodb_additional_mem_pool_size = 20M, innodb_file_per_table

Buffer Pool Read Efficiency:          99.89%
                  Data Read:              17G                                            4,892G
               Data Written:              29M                                            6,167G
...

====================================================================================================
                                          InnoDB Log Files
====================================================================================================

Variables: innodb_log_file_size=256M; innodb_log_files_in_group=2;innodb_log_buffer_size=1M;innodb_flush_log_at_trx_commit=2

           Log Data Written:               1G                                              327G
                 Log Writes:            4,756                     1.34                1,785,842
         Log Write Requests:        4,195,878                 1,180.28              773,981,459
                  Log Waits:                0                     0.00                       13




Exhibit 4- Negative Numbers


====================================================================================================
                                            Index Usage
====================================================================================================

           Index Efficiency:           51.09%
           Full Index Scans:            7,056                     0.08                  142,549
           Full Table Scans:          191,051                     2.21                4,739,205
            Full Join Scans:              374                     0.00                    9,601
         Handler_read_first:            7,056                     0.08                  142,549 (0.00%)
           Handler_read_key:      136,956,475                 1,585.20            3,698,727,203 (47.29%)
          Handler_read_next:       55,431,938                   641.60              290,189,865 (3.71%)
          Handler_read_prev:          210,418                     2.44                7,283,443 (0.09%)
           Handler_read_rnd:       58,241,824                   674.12            1,862,365,188 (23.81%)
      Handler_read_rnd_next:   -1,682,312,703               -19,471.89            1,963,342,385 (25.10%)



A Full output Example


====================================================================================================
              Uptime: 17 days 17 hours 22 mins Snapshot Period 1: 59 minute interval
====================================================================================================
                    Variable	Delta/Percentage 	    Per Second			  Total
====================================================================================================
                                         Database Activity
====================================================================================================

          Threads Connected:               -5                                               115
            Threads Running:               -4                                                51
                  Questions:       24,190,027                 6,804.51            7,366,339,778
             Bytes Recieved:               1G                     501K                     522G
                 Bytes Sent:              11G                       3M                   2,808G
            Aborted Clients:                0                     0.00                      237
           Aborted Connects:              240                     0.07                  102,090

====================================================================================================
                                         Statement Activity
====================================================================================================

                     SELECT:       13,503,876                 3,798.56            4,298,170,239 (94.25%)
                     INSERT:           91,101                    25.63               25,327,062 (0.56%)
                     UPDATE:          782,004                   219.97              220,640,296 (4.84%)
                     DELETE:            9,674                     2.72                2,485,643 (0.05%)
                    REPLACE:                0                     0.00                    4,980 (0.00%)
          INSERT ... SELECT:                0                     0.00                        0 (0.00%)
         REPLACE ... SELECT:                0                     0.00                        0 (0.00%)
               Multi UPDATE:                0                     0.00                        0 (0.00%)
               Multi DELETE:                0                     0.00                        0 (0.00%)
                     COMMIT:           46,422                    13.06               13,700,478 (0.30%)
                   ROLLBACK:                0                     0.00                       13 (0.00%)

====================================================================================================
                                        Prepared Statements
====================================================================================================

   Prepared Statement Count:                0                     0.00                        0
                    PREPARE:                0                     0.00                        0
                    EXECUTE:                0                     0.00                        0
         DEALLOCATE PREPARE:                0                     0.00                        0
           Fetch Roundtrips:                0                     0.00                        0
             Send Long Data:                0                     0.00                        0

====================================================================================================
                                           Admin Commands
====================================================================================================

                       KILL:                0                     0.00                       21
                      FLUSH:                0                     0.00                       34
              ANALYZE TABLE:                0                     0.00                        0
             OPTIMIZE TABLE:                0                     0.00                        0
                CHECK TABLE:                0                     0.00                       51
               REPAIR TABLE:                0                     0.00                        0

====================================================================================================
                                            Thread Cache
====================================================================================================

          Thread Efficiency:           100.00%
                Connections:        2,404,601                   676.40              691,324,391
            Threads Created:                0                     0.00                    1,015

====================================================================================================
                                            Table Cache
====================================================================================================

     table_cache Efficiency:           12.94%
                Open Tables:               18                     0.01                    1,100
              Opened Tables:               18                     0.01                    8,501

====================================================================================================
                                          MyISAM Key Cache
====================================================================================================

      Cache Read Efficiency:           75.56%
     Cache Write Efficiency:           2.50%
                Memory Used:               0B                                               24B
                Memory Free:               0B                                               13K
                  Key Reads:                0                     0.00                       44
          Key Read Requests:                0                     0.00                      179
                 Key Writes:                0                     0.00                       39
         Key Write Requests:                0                     0.00                       39
         Blocks Not Flushed:                0                     0.00                        0

====================================================================================================
                                         InnoDB Buffer Pool
====================================================================================================

Buffer Pool Read Efficiency:          99.89%
               Memory Total:               0B                                               11G
                Memory Free:               0B                                                0B
                Memory Data:     -12,910,592B                                               10G
               Memory Dirty:             245M                                                3G
                  Data Read:              17G                                            4,892G
               Data Written:              29M                                            6,167G
          Buffer Pool Reads:          864,166                   243.08              234,058,329
  Buffer Pool Read Requests:      674,921,081               189,851.22          213,974,254,498
 Buffer Pool Write Requests:       34,337,556                 9,658.95            5,907,928,452

====================================================================================================
                                          InnoDB Log Files
====================================================================================================

           Log Data Written:               1G                                              327G
                 Log Writes:            4,756                     1.34                1,785,842
         Log Write Requests:        4,195,878                 1,180.28              773,981,459
                  Log Waits:                0                     0.00                       13

====================================================================================================
                                            Query Cache
====================================================================================================

       QCache Hits / SELECT:           0.00%
   QCache Hit/Qcache Insert:           0.00%
  Qcache Hits/Invalidations:           0.00%
                    SELECTs:       13,503,876                 3,798.56            4,298,170,239
           Query Cache Hits:                0                     0.00                        0
        Query Cache Inserts:                0                     0.00                        0
         Queries Not Cached:                0                     0.00                        0
    Cache Low Memory Prunes:                0                     0.00                        0
         Total Cache Blocks:                0                     0.00                        0
           Queries In Cache:                0                     0.00                        0
          Cache Free Blocks:                0                     0.00                        0

====================================================================================================
                                            Index Usage
====================================================================================================

           Index Efficiency:           96.38%
           Full Index Scans:                0                     0.00                    3,685
           Full Table Scans:           26,468                     7.45                9,336,473
            Full Join Scans:                0                     0.00                        0
         Handler_read_first:                0                     0.00                    3,685 (0.00%)
           Handler_read_key:       60,313,973                16,965.96           18,840,285,973 (14.08%)
          Handler_read_next:      284,810,290                80,115.41          109,257,639,924 (81.68%)
          Handler_read_prev:        2,524,541                   710.14              822,756,210 (0.62%)
           Handler_read_rnd:       10,268,347                 2,888.42            3,230,517,410 (2.42%)
      Handler_read_rnd_next:          780,215                   219.47            1,612,883,644 (1.21%)

====================================================================================================
                                          Temporary Space
====================================================================================================

  tmp_table_size Efficiency:           2.10%
         Memory Temp Tables:           26,467                     7.45                9,335,030
           Disk Temp Tables:           25,951                     7.30                9,138,705
                 Temp Files:                2                     0.00                      601

====================================================================================================
                                          Lock Contention
====================================================================================================

    Percent of Locks Waited:            0.00%
         Table Locks Waited:                0                     0.00                      230
      Table Locks Immediate:       14,411,359                 4,053.83            4,555,498,747

====================================================================================================
                                              Sorting
====================================================================================================

                Rows Sorted:          790,892                   222.47              251,683,065
                 Sort Range:            3,767                     1.06                  983,825
                  Sort Scan:           25,952                     7.30                9,137,325
          Sort Merge Passes:                1                     0.00                      298
           Full Range Joins:                0                     0.00                        0



The value of multi insert values
 

 by   
Baron got a great amount of response from his 50 things to know before migrating Oracle to MySQL.   I’m glad I invited him as a fellow MySQL colleague to my presentation to the Federal Government on Best Practices for Migrating to MySQL from Oracle and SQL Server for his inspiration.


Oracle will always be a more featured product then MySQL.   There are however features that MySQL has that Oracle does not. While I’ve got a draft of a list of my own, I have several hundred incomplete drafts.


One of these features I was able to demonstrate to a client is the ability to have multiple VALUES clauses for a single INSERT statement. For example.


INSERT INTO t1(c1) VALUES (1), (2), (3), (4), (5);



Instead of


INSERT INTO t1(c1) VALUES(1);
INSERT INTO t1(c1) VALUES(2);
INSERT INTO t1(c1) VALUES(3);
INSERT INTO t1(c1) VALUES(4);
INSERT INTO t1(c1) VALUES(5);



Does it make a difference? What is the performance improvement?


The number one reason for an improvement in performance is the lack of network latency for each command.  We ran a number of tests in a specific example for the client, taking multiple single insert statements, and combining into combined statements.


We ran tests across localhost and also a network test.


It was found that taking several thousand INSERT queries and combined into a maximum of 1M packets made sense.  Overall this single test showed a 88% improvement from 11.4 seconds to 1.4 seconds.


real        0m11.403s
user        0m0.175s
sys         0m0.157s

real        0m1.415s
user        0m0.019s
sys         0m0.012s



In the real world example, differences in the volumes of query to combine and system load  showed a reduction of 72%


What is max_tmp_tables?
 

 by   
Recently I came across another configuration option I’d not heard of before. I profess to not know them all,  however I do know when I find something unusual.  If you are a beginner DBA, learn what is normal and expected, and identify what is out of the normal, investigate, research and question if necessary.


I gave away a MySQL Administrator’s Book  based on seeing a configuration with safe-show-database, an option I’d not seen before, and then requesting people giving basic configuration options in that situation.


The latest is  max_tmp_tables.  So, what does the manual say for this option. I quote:


The maximum number of temporary tables a client can keep open at the same time. (This option does not yet do anything.) 


If this option doesn’t yet do anything, why is it there?  Does it actually do something and the documentation is misrepresenting the option? Did it provide some feature or functionality before?


I know MySQL has a number of features where are not fully featured or even production strength in a production environment.  This makes me wonder how many more parameters, options or features exist but don’t actual do anything or work as designed!


I then also question where organizations or people come up with using these options when the basic required options are not in place. Sometimes just using the basics is the best practice to start with.


O'Reilly Twitter Boot Camp a success
 

 by   
The first O’Reilly Twitter Boot Camp – #OTBC was held in New York as a pre cursor to 140 Characters Conference – #140conf on Monday 15th June, 2009.


With opening and closing keynotes were like matching bookends of The Twitter Book #twitterbook offered to all attendees and authored by the keynoters @timoreilly and @SarahM.


Attendees came from across the country.  Just a few I spoke with coming from LA – @EricMueller of @FLWbooks, Texas – @marlaerwin , Vancouver – HootSuite, Las Vegas -zappos, Boston – @mvolpe , Philadelphia, @SBrownCCI from Cincinnati and @sticky_mommy from Vermont.


The demographics of attendees was a little different from my usual O’Reilly conferences of MySQL, OSCON and Web 2.0.  There were less the half the attendees with laptops at hand for notes & twittering, offset by the high blackberry or should I say shaq-berry users (Thanks Ami @digitalroyalty), easily seen from the back of the steep and dark auditorium. A greater proportion of different industries and gender lead to many questions and discussions from users, not just technologists.


The morning panel sessions afforded no question time due to speakers providing good but overtime content.  Over lunch Mike Volpe of HubSpot a corporate sponsor for the day set the standard by asking his panel of speakers to stick on time. This afforded almost 30 minutes of question time and a roar of approval from the crowd.


There is a lot of valuable information you can find by Twitter Search of #OTBC. A few examples include:


    

  • @archivesnext: Good advice: RT @mpedson RT @timoreilly: Twitter usage policy from @zappos at #OTBC: “Just be real and use your best judgement.”  
    • 

  • @GeekGirlCamp: Hmmmm. Lots of conflicting views on following on Twitter here. What makes YOU follow someone? Would love to know… #OTBC  
    • 

  • @CarriBugbee: ROI is a tricky thing on twitter; if you’re using it solely to generate revenue, you might be there for the wrong reason – @wholefoods #otbc  
    • 

  • @mvolpe: “Driving ROI on Twitter” slides and video of my presentation later today for #OTBC – http://tinyurl.com/061509mvolpe
    • 

  • @ronaldbradford: Best Practices for Twitter – Build a commercial-grade profile. @CarriBugbee at #OTBC  
    • 

  • @journalismgal: Ask questions within your tweets even something as simple as your fab apple #otbc  
    • 

  • @ronaldbradford: Do stay tuned in. Nights, weekends, holidays are all twitter time. Maria Erwin @wholefoods at #OTBC
    • 

  • @harrybrelsford: Is Twitter the new Google? That is belief of @erictpeterson Twitter is creating entire new businesses (Flash Light books) #otbc #smbnation  
    • 



My individual brands of  @ronaldbradford and @MySQLExpert will certainly benefit from a wealth of knowledge of the day. If only I had my Twitter name on the tee shirt I was wearing for the event.


The only down sides to the venue the lack of power for attendees, flaky Internet and a basement auditorium with no cell phone service. Important things to re-consider for a online technology conference. In true form the attendees including myself @ronaldbradford, @SBrownCCI, @GeekGirlCamp, @14str8 used the medium of the conference and our voices were heard and some limited power made available. Thanks O’Reilly for listening.


Thank you to all speakers @katmeyer, @timoreilly, @steverubel, @zappos, @carribugbee, @twittermoms, @flwbooks, @davidjdeal, @bethharte, @dunkindonuts, @reggiebradford, @wholefoods, @tedmurphy, @adbroad, @digitalroyalty, @erictpeterson, @mvolpe, @laureltouby, @sarahm and to Zappos.com for the after event happy hour.


Wafflecloud with cream
 

 by   
I have been working recently with Matt Yonkovit to get Waffle Grid cloud enabled with  Amazon Web Services (AWS).


An initial version of Waffle Grid Cream – Version 0.5 release is now available.


We have elected to create one AMI for now, that is ready to be configured as either a MySQL Server, a memcached server, or as in the following example both. For this first version, we have also not configured MySQL or memcache, but rather provide a virgin Waffle Grid ready server for developers to experiment and benchmark with.


Future releases will include custom AMI’s and the automated ability to register new memcached servers with the Waffle Grid enabled MySQL server.


Instance Creation


We assume you have created an EC2 account and are using one of the many tools available to launch images.


The AMI you want to launch is ami-0575936c. This is an Ubunut Intrepid 8.10 32bit small instance, and includes MySQL 5.4.0 beta and Memcache 1.4.0 RC1.


Configuration


$ ssh -i [key] ubuntu@ec2-[hostname]
$ ps -ef | grep -e "mysql" - "memcached"
$ memcached -m 1024 -p 11211 -u nobody -l 127.0.0.1 -d
$ memstat -s localhost
$ sudo /etc/init.d/mysql start



Verification


$ mysql -uroot -e "SELECT VERSION"
$ mysql -uroot -e "SHOW ENGINE INNODB STATUSG"



The Innodb Status shows a new section.


---------
MEMCACHED
---------
Memcached puts    0
Memcached hits    0
Memcached misses  0
Memcached Prefix:  3576



Testing


$ mysql -uroot -e "SELECT COUNT(*) FROM sakila.actor"
$ mysql -uroot -e "SHOW ENGINE INNODB STATUSG"
$ memcached -s localhost



Verification will show the change of information in the INNODB STATUS output.


---------
MEMCACHED
---------
Memcached puts    4
Memcached hits    0
Memcached misses  4
Memcached Prefix:  3576
Memcached Miss Total Lat 103 (us)
Memcached Miss Recent Lat 103 (us)
Memcached Set Total Lat 760 (us)
Memcached Set Recent Lat 760 (us)



You can also confirm stats in memcached.


$memstat -s localhost
Listing 1 Server

Server: localhost (11211)
        pid: 3453
        uptime: 575
        time: 1245013741
        version: 1.4.0-rc1
        pointer_size: 32
        rusage_user: 0.0
        rusage_system: 0.0
        curr_items: 5
        total_items: 5
        bytes: 82265
        curr_connections: 6
        total_connections: 9
        connection_structures: 7
        cmd_get: 4
        cmd_set: 5
        get_hits: 0
        get_misses: 4
        evictions: 0
        bytes_read: 82265
        bytes_written: 82265
        limit_maxbytes: 1073741824
        threads: 5



multi-threaded memcached
 

 by   
I discovered while compiling Wafflegrid today that by default, the Ubuntu binaries for memcached are not-multithreaded.


Following the installation of memcached from apt-get and libmemcached I ran memslap for:


$ memslap -s localhost
    Threads connecting to servers 1
    Took 1.633 seconds to load data

$ memstat -s localhost
Listing 1 Server

Server: localhost (11211)
     pid: 23868
     uptime: 54
     time: 1244575816
     version: 1.2.2
     pointer_size: 32
     rusage_user: 0.90000
     rusage_system: 0.120000
     curr_items: 10000
     total_items: 10000
     bytes: 5430000
     curr_connections: 1
     total_connections: 3
     connection_structures: 2
     cmd_get: 0
     cmd_set: 10000
     get_hits: 0
     get_misses: 0
     evictions: 0
     bytes_read: 5430000
     bytes_written: 5430000
     limit_maxbytes: 0
     threads: 1



By installed the Latest RC 1.4.0 we see.


memslap -s localhost
    Threads connecting to servers 1
    Took 0.866 seconds to load data

memstat -s localhost

Listing 1 Server

Server: localhost (11211)
     pid: 8651
     uptime: 375
     time: 1244577237
     version: 1.4.0-rc1
     pointer_size: 32
     rusage_user: 0.110000
     rusage_system: 0.130000
     curr_items: 10000
     total_items: 10000
     bytes: 5510000
     curr_connections: 5
     total_connections: 8
     connection_structures: 6
     cmd_get: 0
     cmd_set: 10000
     get_hits: 0
     get_misses: 0
     evictions: 0
     bytes_read: 5510000
     bytes_written: 5510000
     limit_maxbytes: 0
     threads: 5



Thanks Matt for pointing that one out.


Problems compiling MySQL 5.4
 

 by   
Seem’s the year Sun had for improving MySQL, and with an entire new 5.4 branch the development team could not fix the autoconf and compile dependencies that has been in MySQL for all the years I’ve been compiling MySQL.  Drizzle has got it right, thanks to the great work of Monty Taylor.


I’m working on the Wafflegrid AWS EC2 AMI’s for Matt Yonkovit and while compiling 5.1 was straight forward under Ubuntu 8.10 Intrepid, compiling 5.4 was more complicated.


For MySQL 5.1 I needed only to do the following:


apt-get install -y build-essential
apt-get install libncurses5-dev
./configure
make
make install



For MySQL 5.4, I elected to use the BUILD scripts (based on Wafflegrid recommendations).  That didn’t go far before I needed.


apt-get install -y automake libtool



You then have to go compiling MySQL 5.4 for 10+ minutes to get an abstract error, then you need to consider what dependencies may be missing.

I don’t like to do a blanket apt-get of a long list of proposed packages unless I know they are actually needed.


The error was:


make[1]: Entering directory `/src/mysql-5.4.0-beta/sql'
make[1]: warning: -jN forced in submake: disabling jobserver mode.
/bin/bash ../ylwrap sql_yacc.yy y.tab.c sql_yacc.cc y.tab.h sql_yacc.h y.output sql_yacc.output -- -d --verbose
make -j 6 gen_lex_hash
make[2]: Entering directory `/src/mysql-5.4.0-beta/sql'
rm -f mini_client_errors.c
/bin/ln -s ../libmysql/errmsg.c mini_client_errors.c
make[2]: warning: -jN forced in submake: disabling jobserver mode.
rm -f pack.c
../ylwrap: line 111: -d: command not found
/bin/ln -s ../sql-common/pack.c pack.c
....
make[1]: Leaving directory `/src/mysql-5.4.0-beta/sql'
make: *** [all-recursive] Error 1



What a lovely error  ../ylwrap: line 111: -d: command not found


ylwrap is part of yacc, and by default in this instance it’s not even an installed package. I’ve compiled MySQL long enough that it requires yacc, and actually bison but to you think it would hurt if the configure told the user this.


It’s also been some time since I’ve compiled MySQL source, rather focusing on Drizzle.  I had forgotten just how many compile warnings MySQL throws. Granted a warning is not an error, but you should not just ignore them in building a quality product.