English on FromDual GmbH

Recover lost .frm files for InnoDB tables

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 20 Dec 2011 22:51:03 +0000

Recently I found in a forum the following request for help:

Rolling upgrade of Galera 1.0 to 1.1

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 14 Dec 2011 15:38:27 +0000

A few days ago Codership announced their new version Galera v1.1 - synchronous Replication Cluster for MySQL. Before we look at the new feature of Rolling Online Schema Upgrade (OSU) we have a look at how to upgrade to the new Galera release.

Migrating from MySQL Master-Master Replication to Galera Multi-Master Replication

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 02 Dec 2011 14:48:58 +0000

Introduction

Galera is a synchronous Multi-Master Replication for MySQL. It is therefore in competition with several other MySQL architectures:

How MySQL behaves with many schemata, tables and partitions

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 30 Nov 2011 15:35:28 +0000

Introduction

Recently a customer claimed that his queries were slow some times and sometimes they were fast.

Building Galera Replication from Scratch

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sun, 13 Nov 2011 12:29:54 +0000

Introduction

MySQL/Galera synchronous Multi-Master Replication consists of 2 parts:

The wsrep patches for MySQL (codership-mysql) and
the Galera Replication Plugin (galera).

If you do not want to download the prepared binaries you can build it on you own.
First you have to download the native MySQL sources, then patch it with the Galera wsrep patches and compile it. In a second step you have to build the Galera Plugin.

MySQL Vala Program Example

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 08 Sep 2011 13:28:10 +0000

Summary: In this article we have a short look at a simple MySQL example program written in Vala.

Exercises of Advanced MySQL Developer Workshop

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 18 Aug 2011 13:01:26 +0000

Our Advanced MySQL Developer Workshop is over now and IMHO it was quite a success.
During the workshop it is planned to have some exercises. If you are curious and if you want to test or train your MySQL skills, find the exercises here: Advanced MySQL Developer Workshop Exercises.

MySQL JMeter Webshop Benchmark

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 10 Aug 2011 17:23:02 +0000

Abstract: In this article we provide a little JMeter WebShop Example Benchmark for MySQL.

To zip, or not to zip, that is the question

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 08 Aug 2011 11:12:20 +0000

Abstract: In this article we have a look at the compression options of common zipping tools and its impact on the size of the compressed files and the compression time. Further we look at the new parallel zip tools which make use of several cores.

How good is MySQL INSERT TRIGGER performance

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 03 Aug 2011 17:08:36 +0000

Abstract: In this article we discuss how big is the performance impact of MySQL TRIGGERs compared to application side logging (with INSERT) into a MySQL table.

ER-Diagram of the InnoDB Data Dictionary

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 29 Jul 2011 17:37:30 +0000

With the new MySQL 5.6 release there are some more InnoDB Data Dictionary Tables in the INFORMATION_SCHEMA:

Warming up the InnoDB Buffer Pool during start-up

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 22 Jul 2011 17:12:51 +0000

Abstract: Heating up the InnoDB Buffer Pool during the MySQL instance startup should significantly improve InnoDB Performance in the beginning of the life of the Instance. This is achieved by sequential scans of the needed data instead of random I/O reads which would happen when we just let the system work it out by itself.
How to find the database objects which can be loaded during MySQL start-up and how to load them automatically is described in this article.

Using NULL as default values

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 21 Jul 2011 18:35:34 +0000

Abstract:

It is common practice in MySQL table design that fields are declared as NOT NULL but some non-sense DEFAULT values are specified for unknown field contents. In this article we show why this behavior is non optimal an why you should better declare a field to allow NULL values and use NULL values instead of some dummy values.

MySQL out in the wild

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 30 Jun 2011 14:29:37 +0000

One of our partners recently asked me on what platforms do we usually see MySQL installed out there…

MySQL Query Cache does not work with Complex Queries in Transactions

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 29 Jun 2011 13:28:27 +0000

We did recently a review of one of our customers systems and we found that the Query Cache was disabled even thought it had significant more read than write queries.
When we asked the customer why he has not enabled the Query Cache he mentioned a review that was done a few years ago and which stated that the Query Cache hit ratio was non optimal.
This was verified on a testing system which had the Query Cache enabled by accident.

Regularly flushing the MySQL Query Cache

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 17 Jun 2011 21:26:00 +0000

When we analyze our customers systems we see typically a high fragmentation of the query cache after a while. This leads to a less optimal use of the Query Cache than possible.

Be cautious when using Virtualized System with your Database

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 08 Jun 2011 15:01:29 +0000

A customer rose a support case with a problem on his Master-Master set-up. The 2^nd Master claims to have a problem:

Advanced MySQL Developer Workshop

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 08 Jun 2011 10:44:27 +0000

From August 15^th to 17^th FromDual will have an Advanced MySQL Developer Workshop with Citrus in Helsinki (Finland). The workshop will be held in English. The workshop topics you can find here and the registration form is available here.

German speaking MySQL User Group (DMySQLAG) founded today

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 06 Jun 2011 17:14:48 +0000

Today the German speaking MySQL User Group (DMySQLAG) was officially founded in Berlin. The association advocates:

When a MySQL table was last touched

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 02 Jun 2011 20:56:29 +0000

In our last customer project we had around 600 Gbyte of data in a MySQL database. Because this database consumed a significant amount of our disk space and backups with the InnoDB backup tool took pretty long we wanted to find out if we could get rid of some of the tables.

Dumping BLOB's from the MySQL database

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 22 Apr 2011 13:52:42 +0000

A customer who is handling digital certificates had a problem with one of those. So we had to investigate.

PrimeBase Technologies and FromDual form a Service-Cooperation for MySQL products

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 28 Feb 2011 14:58:00 +0000

From the Cooperation of these two companies arises the biggest independent service provider for MySQL and MariaDB in Europe.

MySQL Cluster - Cluster circular replication with 2 replication channels

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 10 Jan 2011 22:30:52 +0000

A few days ago I had to deal with MySQL Cluster replication. I did not do this for a while so I was prepared to expect some interesting surprises once again.

How can I find what InnoDB version I am using?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sat, 01 Jan 2011 12:05:22 +0000

In the old days everything was simpler. We had one maker of our favourite database management system and possibly the choice between different Storage Engines. Mostly the decision has to be taken between MyISAM and InnoDB. When you care about your data integrity you have chosen InnoDB.

Impact of indices on MySQL

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 31 Dec 2010 17:05:17 +0000

It is generally well known that indexes help a lot to speed up database queries (especially SELECT but also UPDATE and DELETE). It is less known, that indexes also have some disadvantages.

MySQL logon and logoff trigger for auditing

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 10 Dec 2010 23:23:51 +0000

A while ago I did some research about MySQL audit functionality and logon a and logoff triggers. MySQL and MariaDB provide a logon trigger in the form of the init_connect variable but no logoff trigger where most of the work for auditing would be done. When we would have a logoff trigger we could track the login and possibility some activity of a user and implement auditing functionality.

Transactional memory resident tables with PBXT

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sun, 21 Nov 2010 21:32:18 +0000

Introduction

In his presentation about PBXT at the DOAG Conference 2010 Paul McCullagh was speaking about memory resident PBXT tables. They will be available in version 1.1 of the PBXT Storage Engine Plugin. Memory resident PBXT tables should have similar characteristics like normal MySQL MEMORY</span> tables</a>. But in addition to the MEMORY tables they are transactional and can handle BLOB</span> and TEXT attributes.

How many warm MyISAM key blocks do you have?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 18 Oct 2010 17:56:44 +0000

When you are working with MyISAM [ 1 ] tables MySQL provides a feature called the Midpoint Insertion Strategy [ 2 ]. You can enable it with the parameter key_cache_division_limit [ 3 ].

FromDual plans Advanced MySQL DBA Workshop

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Sep 2010 15:59:40 +0000

With one of its partners FromDual plans to offer an Advanced MySQL DBA Workshop. The first workshop should run in November 2010.

MySQL Cluster Local Checkpoint (LCP) and Global Checkpoint (GCP)

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 29 Jul 2010 16:29:48 +0000

MySQL Cluster is mainly an in-memory database. Nevertheless it requires a good I/O system for writing various different information to disk.

ODBA Interview with FromDual about the MySQL/MariaDB future

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 03 Jun 2010 15:29:16 +0000

Henrik Ingo from the Open Database Alliance (ODBA) did an interview with Oli Sennhauser of FromDual about the European MySQL database landscape and its future. If you want to know more about our opinion in this matter please read here.

MySQL, where are you going?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sun, 28 Mar 2010 20:51:09 +0000

Our presentation MySQL, where are you going? of March 25 at the OpenExpo in Bern is now available in German and English.

Logging users to the MySQL error log

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 15 Feb 2010 16:18:00 +0000

Problem

A customer recently showed up with the following problem:

Can you trust your MySQL backup?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 11 Feb 2010 22:06:00 +0000

Today a customer with corrupted data files showed up. When we enquired a bit more he told us that he had a broken I/O controller. This is one of the worst things which can happen to you!

What is CHECK TABLE doing with InnoDB tables?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 29 Jan 2010 21:37:00 +0000

Recently we had a case where a customer got some corrupted blocks in his InnoDB tables. His largest tables where quite big, about 30 to 100 Gbyte. Why he got this corrupted blocks we did not find out yet (disk broken?).

MySQL reporting to syslog

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 07 Jan 2010 10:20:00 +0000

There are 2 different possible situations you can face when you have to deal with MySQL and syslog:

My wish for the New Year: MySQL DBA's, please install iostat on your servers!

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 30 Dec 2009 14:00:00 +0000

iostat is a very handy tool to help you investigating what kind of performance problems you have. Especially your databases can cause a lot of troubles to your I/O system and thus it would be very nice if every DBA has installed iostat on all of his MySQL database servers.

MySQL useful add-on collection using UDF

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 19 Oct 2009 11:14:00 +0000

I really like this new toy (for me) called UDF. So I try to provide some more, hopefully useful, functionality.

Using MySQL User-Defined Functions (UDF) to get MySQL internal informations

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 15 Oct 2009 20:34:00 +0000

In one of my previous posts I was writing about how to read other processes memory
[ 1
]. As an example I tried to get the value of the hard coded MySQL internal InnoDB variable spin_wait_delay (srv_spin_wait_delay).

Determine in MySQL if we are in summer time or winter time (daylight saving time, DST)

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 02 Oct 2009 11:24:00 +0000

Recently a colleague at Sun was asking me if MySQL can tell him to determine if we are currently in summer time or winter time. He was doing some data analysis of his house where he has installed solar panels.

Reading other processes memory

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 14 Aug 2009 14:49:00 +0000

As you probably have experienced yet MySQL does not always provide all internal information as you might want to have them and as you are used to have from other RDBMS.

MySQL licenses for dummies

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 23 Dec 2008 12:03:00 +0000

The following summary shows my personal understanding of MySQL 5.1 licenses, packages and products. It does not necessarily reflect 100% the way MySQL understands it. But after all the discussions I hope it is as close as possible to the reality: