I got a question a while ago that I thought was quite simple, but turned into an interesting discussion: How much hard disk space does a database take up?

As it happens, there's a simple answer and a much, much more involved (yet ill-defined) answer, and which one you choose depends on what you think goes into a database and how very, very pedantic you are.

The Simple Answer

You can query the size of table and index data using Information Schema or SHOW TABLE STATUS. The columns DATA_LENGTH and INDEX_LENGTH contain the number of bytes for the table and index data respectively. You can construct simple queries based on that data, or do a quick search on the web for more interesting queries (For example, Peter Zaitsev of Percona wrote a post …

“Application designers need to start by thinking about what level of data integrity they need, rather than what they want, and then design their technology stack around that reality. Everyone would like a database that guarantees perfect availability, perfect consistency, instantaneous response times, and infinite throughput, but it´s not possible to create a product with [...]

The main benefit of using GTIDs is to have much easier failover than with file-based replication. We will see how to change the replication topology when using GTID-based replication. That will show where GTIDs shine and where improvements are expected.

This is the second post of a series of articles focused on MySQL 5.6 GTIDs. You can find part one here.

Our goal will be to go from setup #1 to setup #2 on the picture below, following various scenarios:

For these tests, all servers are running on 127.0.0.1 with ports ranging from 10000 for s0 to 10004 for s4.

Scenario #1: All slaves have processed all the writes

This is the easiest case, we will …

MySQL can optimize aggregate functions like MIN and MAX as long as the columns specified are indexed. This means that, in the case of MIN and MAX, the optimizer should be able to identify the highest and lowest values of an indexed column from the B-Tree index. Say I have a table like below:

CREATE TABLE `history` (
   `h_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
   `u_id` int(10) unsigned NOT NULL,
   `cn_id` int(10) unsigned NOT NULL,
   `f_id` int(10) unsigned NOT NULL
   PRIMARY KEY (`h_id`)
 ) ENGINE=InnoDB

If I want to get the MAX value for cn_id, I’d to a query like this which will be a full table scan:

mysql (test) > EXPLAIN SELECT MAX(cn_id) FROM history \G
 *************************** 1. row ***************************
            id: 1
   select_type: SIMPLE
         table: history
          type: ALL
 possible_keys: NULL
           key: NULL
       key_len: NULL
           ref: NULL
          rows: 19908716 …

Read the original article at The Needle in Big Data Noise

Join 5500 others and follow Sean Hull on twitter @hullsean. Also take a look at: I hacked Disqus Digests to discover new blogs Who the heck is Bayes Thomas Bayes was a scientist & thinker, Fellow of the Royal Society, and back in 1763 author of “An Essay toward Solving a Problem in the Doctrine [...]

For more articles like these go to Sean Hull's Scalable Startups

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This is a step by step guide on installing apache with PHP, APC and MySQL. APC- Advance php cache. This tutorial will works for fedora/redhat/centos.

Install Apache httpd

[root@localhost ~]# yum -y install httpd

Start httpd service

[root@localhost ~]# /etc/init.d/httpd start           [  OK  ]
[root@localhost ~]# ps -ef | grep http
root      2011     1  0 11:46 ?        00:00:00 /usr/sbin/httpd
apache    2013  2011  0 11:46 ?        00:00:00 /usr/sbin/httpd
apache    2014  2011  0 11:46 …

If you are using Percona Replication Manager (PRM) with RHEL/CentOS prior to 6.4, upgrading your distribution to 6.4 may break your cluster. In this post I will explain you how to fix your cluster in case it breaks after a distribution upgrade that implies an update of pacemaker from 1.1.7 to 1.18. You can also follow the official documentation here.

The version of Pacemaker (always considered as Technology Preview by RedHat) provided with 6.4 is 1.1.8-x which is not 100% compatible with 1.1.7-x see this report.

So if you want to upgrade, you cannot apply any rolling upgrade process. So like for Pacemaker 0.6.x to 1.0.x, you need again to update all nodes as once. As notified in …

I thought I would take the new subquery optimizations in MySQL 5.6 for a spin today, using the world sample database provided by MySQL for certification and training.

Typical IN subquery

This is a very typical query developers run, which historically has performed very poorly on MySQL:

mysql5.5.31 > EXPLAIN SELECT * FROM City WHERE CountryCode IN
 (SELECT code FROM Country WHERE name = 'United States');
*************************** 1. row ***************************
           id: 1
  select_type: PRIMARY
        table: City
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 3984
        Extra: Using where
*************************** 2. row ***************************
           id: 2
  select_type: DEPENDENT SUBQUERY
        table: Country
         type: unique_subquery
possible_keys: PRIMARY …

Thank you for all of you who dropped by the MySQL booth at Drupalcon to say ‘Thank you’ for MySQL. At every show there are several folks who do this but at Drupalcon it seemed like half the 3,000 attending dropped by to say ‘thanks’, grab MySQL stickers, OurSQL Poscasts disks, and talk about MySQL 5.6. I’ll see all y’all next year in Austin.

Speaking of Austin, the Texaslinuxfest.org is this weekend. I will be talking Saturday in Track D at 11:25 on the Proper Care and Feeding of a MySQL Database.

And the FREE Southeast Linux Fest is June 7-9 in Charlotte. This year featuring a ‘Zero to DBA’ track to get all …

Two months ago I posted a performance comparison running Sysbench on MongoDB versus MongoDB with Fractal Tree Indexes v0.0.2. The benchmark showed a 133% improvement in throughput. Nice, but our engineering team had an effort on our road-map for lock refinement that we believed would really boost our performance, which is now available in v0.1.0. The benchmark application itself is unchanged and available on GitHub.

For anyone curious about Sysbench itself, the details are available from the prior blog. The only change for this run was hardware. Our Sun x4150 server recently began rebooting itself at random times, so it has been replaced with a newer HP server. Another change is …