MySQL

MySQL makes community server edition difficult to find and download!

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Read this post today, http://mysqlha.blogspot.com/2010/02/dude-where-is-my-link.html. And I was amazed to find that on mysql.com it was so hard to download the community version of MySQL Server.

On the home page, could see links for

  • Enterprise Products
  • Resources
  • Consulting
  • Training
  • News and Events

Couldn't find a link for Community Server Download or something similar, I've been working with MySQL for over 5 yrs, I know that the downloads and most of the useful stuff for open source devs like me is on http://dev.mysql.com. The Developer Zone hosts the following for us

  • Community Server Downloads
  • Documentation (which keeps changing its links)
  • Articles
  • Forums
  • Beginner articles
  • MySQL forge
  • ... and much more

I'm really surprised and ashamed of this MySQL's or Ora@#$'s move to hide such a widely used link.

I've done my part in adding rel='nofollow' attribute to http://mysql.com

Redis, Memcached, Tokyo Tyrant and MySQL comparision (rectification skip-name-resolve)

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My previous post Redis, Memcache, Tokyp Tyrant, MySQL comparison had a flaw as pointed out by this comment. The MySQL was taking a huge time for doing a reverse DNS lookup.

I turned on the skip-name-resolve parameter in the my.cnf and the Throughput of MySQL grew considerably, almost more than double.

Redis, Memcached, Tokyo Tyrant and MySQL comparision

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I wanted to compare the following DBs, NoSQLs and caching solutions for speed and connections. Tested the following

My test had the following criteria

  • 2 client boxes
  • All clients connecting to the server using Python
  • Used Python's threads to create concurrency
  • Each thread made 10,000 open-close connections to the server
  • The server was
    • Intel(R) Pentium(R) D CPU 3.00GHz
    • Fedora 10 32bit
    • Intel(R) Pentium(R) D CPU 3.00GHz
    • 2.6.27.38-170.2.113.fc10.i686 #1 SMP
    • 1GB RAM
  • Used a md5 as key and a value that was saved
  • Created an index on the key column of the table
  • Each server had SET and GET requests as a different test at same concurrency

Results please !

MySQL DB Pie Graph

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Its same as what http://blog.olindata.com/2009/02/using-the-google-graph-api-with-mysql-stored-functions/ had posted, I've just updated a little. And there are no smart quotes here. So u can copy paste ;)

DELIMITER $$

DROP FUNCTION IF EXISTS `test`.`FNC_GOOGRAPH_DB_SIZE`$$
CREATE FUNCTION `test`.`FNC_GOOGRAPH_DB_SIZE` (
  p_chart_type CHAR,
  p_height INT,
  p_width INT) RETURNS varchar(3000) CHARSET latin1
  READS SQL DATA
BEGIN
  /* Author:    Walter Heck - OlinData */
  /* Date:      20090216 */
  /* Note:      After an idea by Alex Gorbachev - Pythian */
  /*            http://www.pythian.com/blogs/1490/google-charts-for-dba-tablespaces-allocation */

  /* variable declaration */
  DECLARE v_done BOOLEAN default false;
  DECLARE v_url varchar(3000);

  DECLARE v_schema_name varchar(3000);
  DECLARE v_data_length_sum int;
  DECLARE v_data_length_total int;
    
  DECLARE v_legend_labels varchar(3000);
  DECLARE v_chart_labels varchar(3000);
  DECLARE v_chart_data varchar(3000);

  /* Cursor declaration */
  DECLARE c_schema_sizes cursor for
      select
        t.table_schema,
        round(sum(t.data_length + t.index_length) / 1024 / 1024) as data_length_schema
      from
        information_schema.tables t
      group by
        t.table_schema
      order by
        t.table_schema;

  /* Handler declaration */
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_done = true;

  /* Initialize the variables */
  SET v_legend_labels = '';
  SET v_chart_labels = '';
  SET v_chart_data = '';

  /* Get the total data length + index_length for all tables */
  select
      round(sum(t.data_length + t.index_length) / 1024 / 1024) as data_length_total
  into
      v_data_length_total
  from
      information_schema.tables t;
    
  /* Open the cursor */
  OPEN c_schema_sizes;

  /* Loop through the cursor */
  get_data: LOOP

      /* Fetch the next row of data into our variables */
      FETCH c_schema_sizes INTO v_schema_name, v_data_length_sum;

      /* if there is no more data, v_done will be true */
      IF v_done THEN
        /* Exit the loop */
        LEAVE get_data;
      END IF;

      /* Add the schema name to the labels for the legend */
      IF v_legend_labels = '' THEN
        SET v_legend_labels = v_schema_name;
      ELSE
        SET v_legend_labels = concat(v_legend_labels, '|', v_schema_name);
      END IF;

      /* Add the total size of the schema to the labels */
      IF v_chart_labels = '' THEN
        SET v_chart_labels = v_data_length_sum;
      ELSE
        SET v_chart_labels = concat(v_chart_labels, '|', v_data_length_sum);
      END IF;

      /* Get the percentage of the total size as the graph's data */
      IF v_chart_data = '' THEN
        SET v_chart_data = ROUND(v_data_length_sum / v_data_length_total, 2) * 100;
      ELSE
        SET v_chart_data = concat(v_chart_data, ',', ROUND(v_data_length_sum / v_data_length_total, 2) * 100);
      END IF;

  END LOOP get_data;

  /* Close the cursor */
  CLOSE c_schema_sizes;
    
  /* Build up the google graph url */
  SET v_url = 'http://chart.apis.google.com/chart?';
  SET v_url = CONCAT(v_url, 'cht=', p_chart_type);
  SET v_url = CONCAT(v_url, '&chs=', p_width , 'x', p_height);
  SET v_url = CONCAT(v_url, '&chtt=Database Sizes (MB)');
  SET v_url = CONCAT(v_url, '&chl=', v_chart_labels);
  SET v_url = CONCAT(v_url, '&chd=t:', v_chart_data);
  SET v_url = CONCAT(v_url, '&chdl=', v_legend_labels);

  /* return the url as the function's result */
  RETURN v_url;
END$$

DELIMITER ; 

PHP, Python Consistent Hashing

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I found out the hashing algorithm used in PHP-Memcache is different from that of Python-Memcache. The keys went to different servers as the hash created by python and php were different.

I posted a question on the memcache groups and was lucky to find this wonderful reply.

import memcache
import binascii
m = memcache.Client(['192.168.28.7:11211', '192.168.28.8:11211
', '192.168.28.9:11211'])

def php_hash(key):
    return (binascii.crc32(key) >> 16) & 0x7fff

for i in range(30):
       key = 'key' + str(i)
       a = m.get((php_hash(key), key))
       print i, a

This is the only thing that has to be done on Python's end, change the way the hash is calculated. The coding on PHP end remains same. All you guys using PHP for web based front-end with MySQL and Python for back-end scripts shall find this helpful.

Thanks Brian Rue.

Reference: http://groups.google.com/group/memcached/msg/7bb75a026c44ec43

MySQL, Memcache, Replication and Delay

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An interesting article on Facebook, Which deals with MySQL's replication system, Memcache and the replication delay.

... by setting a cookie in your browser with the current time whenever you write something to our databases. The load balancer also looks for that cookie and, if it notices that you wrote something within 20 seconds, will unconditionally send you to California. Then when 20 seconds have passed and we're certain the data has replicated to Virginia, we'll allow you to go back for safe pages.

Light weight MySQL - Drizzle

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What started off as a fast light weight DB and came off as MySQL, has now grown into a heavy dB for some (we always have these :) ).

Introducing Drizzle http://krow.livejournal.com/602409.html

In short it is...

  • ... for Web based apps.
  • ... for Cloud components.
  • Databases without business logic (aka stored procedures).

...more

MySQL Replication Manager screenshot and screencast

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I've uploaded MySQL Replication Manager's (mysqlreplicationmanager) screenshot and Screencast

Screenshot
MySQL Replication Manager Screenshot

Video / Screencast

You can download a full size video from here.

MySQL Replication Manager

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MySQL replication manager has ability to

  1. Start, Stop Slave
  2. Set Status of Slave

Download

License: GNU General Public License

MySQL: Efficient Stored Procedure Editing

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This is not about how to write a Stored Procedure (SP), But how to efficiently write a SP.

MySQL Query Browser

The easiest way to write a SP is to use a MySQL Query Browser, Just select the database and right click the dB and "Create Stored Routite..." This shall help you do easily modify, edit and create procedures.

Command Line

Unfortunately, not many of the dB guys could have access to GUI and create/edit access permissions, they may have to rely on the CLI. This is where create / edit of SPs is the most tedious. Lets set something in our system, before we log into MySQL.

  • In your ~/.bashrc add the following...
    export EDITOR=vim VISUAl=vim
    
  • Create / Edit ~/.vimrc file, and add the following...
    set noai
    set nonu
    
  • Log into the MySQL CLI, and set the following command
    delimiter //