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Previous 30 Newer Entries Showing entries 61 to 90 of 1137 Next 30 Older Entries

Displaying posts with tag: Databases (reset)

Measuring MySQL Query Performance
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Measuring how well a MySQL is doing can be tough – most metrics are simply proxies for actual performance. Thankfully, the Percona build of MySQL allows you to see exactly how long your queries are taking. It provides a diagnostic view that shows how long queries take, allowing you to gauge its real-world performance. I’ll get to that in a little bit. Before we do that, I want to talk about some other tools you can use.

You can dump the status of the system by running “show global status;”. This will give you how many connections have aborted, rows written, and

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

SELECT routine_schema,routine_name
FROM information_schema.routines;
+----------------+-----------------------------------+
| routine_schema | routine_name                      |
+----------------+-----------------------------------+
| mysql          | rds_collect_global_status_history |
| mysql          | rds_disable_gsh_collector         |
| mysql          | rds_disable_gsh_rotation          |
| mysql          | rds_enable_gsh_collector          |
| mysql          | rds_enable_gsh_rotation           |
| mysql          | rds_kill
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MySQL MHA and Perl pathing
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I am certainly not a knowledgeable Perl person, however I recently ran into the error Can’t locate MHA/MasterMonitor.pm on Red Hat 6.x. I have installed MySQL MHA on various systems before without any issues.

$ masterha_manager -version
Can't locate MHA/MasterMonitor.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .) at /usr/bin/masterha_manager line 26.
BEGIN failed--compilation aborted at /usr/bin/masterha_manager line 26.

The issue was that MySQL MHA is not installed in any of the acceptable default paths for this disto default installation.

$ find / -type d -name MHA
/usr/lib/perl5/vendor_perl/MHA

The fix was simple on this OS, but I expect there is

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Cloning MySQL 5.6 instances
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A tip for all those cloud users that like cloning database servers (as reported in my book Effective MySQL – Replication Techniques in Depth).

Starting with MySQL 5.6, MySQL instances have a UUID. Cloning servers to quickly create slaves will result in the following error message.

mysql> SHOW SLAVE STATUS\G
...
  Last_IO_Error: Fatal error: The slave I/O thread stops because master and slave have equal MySQL server UUIDs; these UUIDs must be different for replication to work.
...

The solution is simple. Clear our the file based configuration file (located in the MySQL datadir) and restart the MySQL instance.

$ rm -f /mysql/data/auto.cnf
$ service mysql restart
Unnecessary 3am (emergency) call
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Help, the database is on fire. Well, it probably is but the solution may also be easy. Here are a few steps for the part-time MySQL DBA/sysadmin/developer. Total time to address this solution was 2 minutes, the inability to not go back to sleep, not priceless.

First, access to the DB server is possible, and also the mysql command line client. If you are getting “Too Many Connections” read Why GRANT ALL is bad.

Given the message “the database is on fire”, the likely cause is rogue SQL.

mysql> show global variables like 'max_connections';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 5000  |
+-----------------+-------+
1 row in set (0.02 sec)

mysql> show global status like 'threads%';
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Identifying empty tables in MySQL
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The following simple INFORMATION_SCHEMA statement will identify and also verify tables that have no rows. These may be candidate tables to remove from your data model.

mysql --defaults-file=.my.cnf -N -e "select CONCAT('SELECT \"',table_schema,'.',table_name,'\" AS tbl, COUNT(*) AS cnt FROM ',table_schema,'.',table_name,';') as cmd from information_schema.tables where table_schema not in ('mysql','performance_schema','information_schema') and table_rows=0;" | mysql --defaults-file=.my.cnf -N
Indexing Talk Online
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I am doing a quick blog post to announce that I have put an indexing talk online*. Most recently, I delivered this indexing talk at Confoo and Scale 11x.

The talk is on YouTube at Are You Getting the Best Out of Your MySQL Indexes? There are also PDF slides.
From the official conference description, if you want to know more:
MySQL indexes are often used to make performance better. However, they can make performance suffer if you are not using them properly. Oracle ACE Director Sheeri Cabral explains the pitfalls to avoid with indexes and how to utilize compound indexes to maximize index availability with the least amount of write overhead.

*I know I have not



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A simple FAILED SQL statement breaks MySQL 5.6 replication
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I setup 6 shiny new MySQL 5.6.13 MySQL servers, ready for testing and production deployment tomorrow.

I found that the New Relic MySQL Monitoring was throwing the following error.

[2013-08-08 03:53:33 +0000] com.newrelic.plugins.mysql.MySQL | SEVERE | An SQL error occured running 'SHOW ENGINE INNODB STATUS' Access denied; you need (at least one of) the PROCESS privilege(s) for this operation

Simple fix, the user I am gathering metrics requires the PROCESS privilege. Again simple enough.

mysql> grant PROCESS on xxx.* to xxx@'10.%';
ERROR 1221 (HY000): Incorrect usage of DB GRANT and GLOBAL PRIVILEGES
mysql> grant PROCESS on *.* to xxx@'10.%';
Query OK, 0 rows affected (0.00 sec)

As you can see I got

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Developing Applications for use with Continuent Tungsten and Tungsten Replicator in SDJ
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I’ve just had a new article published with the Software Developers Journal talking about how you can write applications to take full advantage of Continuent Tungsten and Tungsten Replicator.

As a developer of an application there really isn’t a problem better than finding that you have to scale up the application and the database that supports it to handle the increased load. The main bottleneck to most expansion is the database server and in many modern environments that replication is based around MySQL. Application servers are easy to add on to the front-end of your environment.

Read: Qt5 – How to Become a Professional

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DP#8 The disadvantages of row at a time processing
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It can be hard for software engineers to understand the following principle, however it is very important for improving performance and obtaining immediate scalability options. The principle is “Do Less Work”. That is, run less SQL statements.

Just one method to achieving the execution of less SQL statements is to eliminate Row At a Time (RAT) processing. In simple terms, do not perform identical repeating SQL statements in a loop. Relational algebra, and the Structure Query Language (SQL) specification is specifically designed to work with sets of data, or as I describe, Chunk At a Time (CAT) processing.

Customer Example

Your online social media website lets you send messages to multiple friends at one time. You enter the message, select the friends you want to receive the message and click send.

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MySQL configuration file created in /usr/my.cnf
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As part of uncovering a new security improvement in MySQL 5.6 with the default installation being secured with a unique root MySQL password, the MySQL provided rpm’s installed the MySQL configuration file in /usr.

I feel this maybe a bug, however this is just as an explanation for others to comment on.
The following steps reproduces this.

1. Launch a CentOS 6.4 AWS EC2 Instance

LOG=/tmp/create-instance.tmp.$$
INSTANCE_TYPE=m1.medium
ec2-run-instances ami-eb6b0182 --instance-type ${INSTANCE_TYPE} --region us-east-1 --availability-zone us-east-1b --key db --group db | tee ${LOG}
INSTANCE=`grep ^INSTANCE ${LOG} | awk '{print $2}'`
ec2-describe-instances ${INSTANCE} | tee ${LOG}
while [ `grep ^INSTANCE ${LOG} | awk '{print $6}'` !=

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DP#4 The importance of using sql_mode
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What if the data you retrieved from the database did not match the data the application claimed to had successfully stored? How comfortable would your organization feel about your skills and the products that are being used to store important information if data integrity was not guaranteed?

MySQL employs a terrible default technique known as silent truncation where the product determines that it knows about your data better than you. Never has the saying “do not assume” because it makes an “ass” out of “u” and “me” been more applicable.

Customer Example

A HTML form for new customers provide input fields for the customer first and last name. Good design was considered with the HTML form client validation to ensure that each field could not exceed 20 characters in length. However, the database design

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

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

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Improved Security with MySQL 5.6
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Installed on a clean CentOS 6.4 AWS instance.

sudo su -
cd /tmp
wget http://cdn.mysql.com/Downloads/MySQL-5.6/MySQL-5.6.13-1.el6.x86_64.rpm-bundle.tar
tar xvf MySQL-5.6.13-1.el6.x86_64.rpm-bundle.tar
yum install -y libaio perl
rpm -i MySQL*.rpm

The following output is the sign that security is being considered with new MySQL versions. Woot!

A RANDOM PASSWORD HAS BEEN SET FOR THE MySQL root USER !
You will find that password in '/root/.mysql_secret'.

You must change that password on your first connect,
no other statement but 'SET PASSWORD' will be accepted.
See the manual for the semantics of the 'password expired' flag.

Also, the account for the anonymous user has been removed.

In addition, you can run:

  /usr/bin/mysql_secure_installation

which will also give you the option of removing the test database.
This is strongly recommended for
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MySQL Presentations to the Colombia Oracle Users Group
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My slides for presentations on MySQL Backup and Recovery Essentials and Understanding and using MySQL in the Cloud from the Oracle Technology Network (OTN) event in Medellín‎ Colombia are now available.

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

MySQL Proxy and microseconds
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By default the included Lua within MySQL proxy (0.8.3) does not include socket, necessary for getting microsecond granularity. To setup you have to install Lua and socket on the OS first:

For CentO5

$ sudo yum install lua lua-socket

For Ubuntu

$ sudo apt-get install lua5.1 liblua5.1-socket2

The following enables use within MySQL Proxy.

cp /usr/share/lua/5.1/socket.lua /path/to/mysqlproxy/lib/mysql-proxy/lua
cp -r /usr/lib64/lua/5.1/socket /path/to/mysqlproxy/lib/mysql-proxy/lua
cp -r /usr/lib64/lua/5.1/mime /path/to/mysqlproxy/lib/mysql-proxy/lua

My lua script can now use syntax similar to:

require 'socket'

function read_query( packet )
...
  now=socket.gettime()
  print( string.format("# %s.%3d\n%s;\n",os.date("%X",now),select(2,math.modf(now))*1000 , query))
MySQL Monitoring With Cacti Using Percona Monitoring Plugins (1-minute resolution)
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Today, just like many times before, I needed to configure a monitoring server for MySQL using Cacti and awesome Percona Monitoring Templates. The only difference was that this time I wanted to get it to run with 1 min resolution (using ganglia and graphite, both with 10 sec resolution, for all the rest of our monitoring in Swiftype really spoiled me!). And that’s where the usual pain in the ass Cacti configuration gets really amplified by the million things you need to change to make it work. So, this is a short checklist post for those who need to configure a Cacti server with 1 minute resolution and setup Percona Monitoring Plugins on it.

Configuring Cacti for 60-seconds polling

First of all, we

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My MySQL bugs and feature requests
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My MySQL bugs is a list I recently created and intend to keep up to date with issues I have seen.

First Madrid MySQL Users Group scheduled for the 4th July
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As mentioned here and after talking to a few people we have created a meetup page, http://www.meetup.com/Madrid-MySQL-users-group/ and proposed the first meeting on Thursday, 4th July. If you are interested and in the area come along and say hello. It should be interesting to see a few others who work in the field.  If you can let us know you are coming so we have an idea of how much interest there is.

Announcing the MySQL Plugin for New Relic
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Many application developers would know of New Relic. A SaaS performance and monitoring tool targeted towards your web application monitoring including PHP, Ruby, Java, .Net, Python and Node.

With the release today (June 19, 2013) of the New Relic Platform, custom monitoring of data stores including MySQL are now possible. Try it now free. This link will provide you a free standard account (no cost, no billing details necessary), that enables you to perform application monitoring, server monitoring, MySQL instance monitoring and monitoring of many other products via many plugins.

Over the next few posts I will be discussing some of the design decisions I made for this MySQL plugin. New

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On operating system upgrades and a packager’s nightmare
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A fairy tale

Once upon a time I did an operating system upgrade, a minor one that should do no harm, but just get me up to date by fixing any bugs in the version I had been using. It seemed like a good idea.

All seemed to be fine. I use a package provided by an external vendor and not the one produced by the operating system provider as this vendor provides a newer version of the package and I need that. The vendor has to make his package fit in the os environment his package is built for and normally does a pretty good job.

I use automation to build my systems and when I built a new one some issues appeared. Related to the new version of the OS the provider had enhanced one of his packages and the installation pulled in new dependencies. The install of the external package I use then broke as it conflicted with the new dependency

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2013 SkySQL and MariaDB Solutions Videos Are Online!
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I do not recall seeing an announcement about it, but I went looking for the videos today and lo and behold, they were up! Forgive me if I missed a post about it….but if you also missed it, here they are:

2013 SkySQL and MariaDB Solutions Day for the MySQL Database videos

Madrid MySQL Users Group worth creating?
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I’m interested in meeting up and sharing experiences about using MySQL and managing MySQL servers with people here locally in Madrid. I had a quick look around and could see no MySQL user groups locally, so it might be nice to create such a group and exchange ideas over a beer, coffee or cola every once in a while. If you’re in Madrid and are interested please let me know. I’ve created a temporary  email address: madrid-mysql-users-2013 AT wl0.org (careful with the domain), which you can contact me on to confirm an interest.  Oh and I’d expect these meet ups to be in Spanish, but that’s not a requirement.

Estoy interesado en reunirme y compartir experiencias sobre el uso de MySQL y administración de servidores de MySQL con la gente aquí en Madrid. He echado un vistazo en Internet y no he visto ningún grupo de usuarios de MySQL a nivel

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MySQL Quirk with Not Null Columns and Default Values
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One of my coworkers came across a strange quirk in MySQL with default values for not null columns. Take a look at this table:

Create Table Posts
(
     PostID Int Auto_Increment Primary Key
    ,Title Varchar(30) Not Null
    ,Body Text Not Null
    ,Summary Varchar(25) Not Null Default ''
);

Note the column Summary that is marked not null but has a default value of an empty string. Now, try to insert a null value into this column.

Insert Into Posts (Title, Body, Summary) Values ('A title', 'A body', null);

You’ll get this error:

ERROR 1048 (23000): Column 'Summary' cannot be null

Now, using an extended insert (where you specify multiple rows in an insert statement), we can insert the same data and it will complete successfully,

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A Different Spin On the max_allowed_packet Problem
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Back in November, I filed MySQL bug 67448, talking about a different type of max_allowed_packet problem.

See, an application had put data into the database, but could not retrieve it without getting max_allowed_packet. With the help of some really smart community folks (named Jesper Hansen, Brandon Johnson and Shane Bester), we determined that MySQL actually has 2 different max_allowed_packet settings: client and server.

When you change the max_allowed_packet variable, you are changing the server variable if it is in [mysqld] and the client variable if it is in [client] or [mysql] or whatever client you have. As far as we can tell, there’s no way to actually view what the client variable is, as looking at both the session and global max_allowed_packet variable shows you the server

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ulimits and upgrading from Oracle MySQL 5.0 to Percona patched MySQL 5.1
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After upgrading to Percona’s patched MySQL 5.1*, end users were having connectivity problems, and reporting errors such as:

OperationalError: (2003, "Can't connect to MySQL server on 'db-amo-ro' (110)")

TimeoutError: Request timed out after 5.000000 seconds

OperationalError: (1135, "Can't create a new thread (errno 11); if you are not out of available memory, you can consult the manual for a possible OS-dependent bug")

We had these same problems a while back, before increasing ulimit settings in /etc/sysconfig/mysqld. Oracle’s MySQL startup script specifically sources this file:

[ -e /etc/sysconfig/$prog ] && . /etc/sysconfig/$prog

However, we saw these errors again when we upgraded to Percona’s MySQL 5.1.

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MySQL User Group Video – Determinism and Databases
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The May Boston MySQL User Group featured John Hugg of VoltDB talking about determinism and databases. I have uploaded the hour-long video to http://www.youtube.com/watch?v=mTDLyRauJtw. Seasoned MySQLers will nod their heads because the problems described are familiar, and those who are not exactly sure what “determinism and databases” means will learn a lot.

Enjoy!

(As always, videos are free on YouTube with no login or attempt to solicit your e-mail address or any other information)

Upgrading support.mozilla.org databases
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A while ago (November 2012 to be exact), we upgraded the support.mozilla.org databases from Percona 5.1 to MariaDB 5.5 (the next step, happening soon, is upgrading them to Oracle’s MySQL 5.6). One of the engineers and I had a conversation where he mentioned that “one of our worst performing views on SUMO is doing waaaayyy better with the upgraded databases”, that it “seems more stable” and that “I stopped receiving ‘MySQL went away or disconnected emails’ which came in once in a while.”

It’s always nice to see upgrades actually making a difference. In our case we saw a lot less CPU wait, though that might also be partially due to tuning the memory settings on the machines and adding in another read slave to handle queries. As a result, network traffic throughput went from less than 1 Mb/sec to about 18

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Percona Ireland??
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Anybody else noticed that Percona appears to not be a US entity any more?

I observed it today.

$ sudo /usr/bin/innobackupex ...
InnoDB Backup Utility v1.5.1-xtrabackup; Copyright 2003, 2009 Innobase Oy
and Percona Ireland Ltd 2009-2012.  All Rights Reserved.

This software is published under
the GNU GENERAL PUBLIC LICENSE Version 2, June 1991.

In previous versions this did say Percona Inc, 2009-2012.

The footer of the Documentation also states © Copyright Percona Ireland Ltd. 2009-2013.

Women in Science and Engineering (WISE) Computing Skills Boot Camp
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Software Carpentry is running a 2-day software skills boot camp in Boston, June 24-25th 2013, for women in science, engineering, medicine, and related research
areas. Registration is $20.

Boot camps alternate short tutorials with hands-on practical exercises. You are taught tools and concepts you can use immediately to increase your productivity and improve confidence in your results. Topics covered include the Unix shell, version control, basic Python programming, testing, and debugging — the core skills needed to write, test and manage research software.

This boot camp is open to women at all stages of their research careers, from graduate students, post-docs, and faculty to staff scientists


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