This week we discuss advanced pt-table-sync, including bidirectional sync. Ear Candy is starting MySQL on low-memory virtual machines, and At the Movies is "What's New With MySQL and MariaDB?"

pt-table-sync
Episode 188, where we talked about pt-table-sync basics
pt-table-sync documentation

Options discussed:
--bidirectional
--chunk-column
--conflict-column
--conflict-comparison - greatest, least, newest, oldest, equals, matches
--conflict-value
--conflict-error

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I have just released version 3.5.5 of MyQuery, which is a minor feature, cleanup and bugfix release. If you don't know MyQuery since before, this is an Open-Source Windows based MySQL and MariaDB ad-hoc query tool. What makes MyQuery slightly different from all the other similar tools is that MyQuery has a focus on SQL-scripting, allowing statements in a script to be run one at the time, to restart a script where it left of in the case of an error and some other features like this. MyQuery features colour coded syntax as it uses Scintilla for editing, and this is highly configurable. Also, multiple editing tabs are supported. Another thing that makes MyQuery stand out a bit is that it is highly flexible. If you have SQL statements that you run often to monitor the state of the server or your application, then it is real easy to implement this as a simple tool accessible from the MyQuery menu.

There …

In the latest release of MySQL Utilities 1.4.3 GA, the performance of the mysqldbcompare utility has been considerably improved along with some bug fixes. This blog briefly explains some of the improvements that were made and shows evidence of the increased performance of database comparison.

• A new step was added to the data consistency check. It now executes a full table checksum, which is faster when no differences are expected. The algorithm to find row differences is only executed if this preliminary table
  checksum fails.

• A new --skip-checksum-table option was added to skip this new step should you wish to (when you know there are differences it saves a bit of time).

• The current algorithm to find row differences was optimized to internally store and access the generated hash values.

What follows are some examples comparing the world database with …

June 16, 2014 By Severalnines

MongoDB is great at storing clickstream data, but using it to analyze millions of documents can be challenging. Hadoop provides a way of processing and analyzing data at large scale. Since it is a parallel system, workloads can be split on multiple nodes and computations on large datasets can be done in relatively short timeframes. MongoDB data can be moved into Hadoop using ETL tools like Talend or Pentaho Data Integration (Kettle).

In this blog, we’ll show you how to integrate your MongoDB and Hadoop datastores using Talend. We have a MongoDB database collecting clickstream data from several websites. We’ll create a job in Talend to extract the documents from MongoDB, transform and then load them into HDFS. We will also show you how to schedule this job to be executed every 5 minutes.

Test Case

We have an application …

Before you start creating database entities, spend some time designing your database to ensure that it is fit for your purpose. The time you invest in this process saves a lot of time and trouble later. Professional database designers fine-tune their design using a process called 'normalization'. The normalization process takes your database design through a number of 'normal forms', which aim to ensure efficient data access, greater query flexibility, and easier maintenance.

For example, the First Normal Form (or '1NF') ensures that all your database columns contain only a single value. A column that contains multiple data values is difficult to access and keep up to date. It also ensures that each table row only represents a single 'real world' item. Like all the other normal forms, this encourages you to split your data across multiple tables, with less rows in each table. You can quickly see the benefits of this approach as your database …

MariaDB Roadshow Helsinki

One could say that MariaDB originates from Finland’s capital Helsinki. In fact so does MySQL. It was in the Helsinki area that MySQL saw daylight. It was here that Monty Widenius laid the ground for MySQL already in the 80’s, maybe even 1979, when he created UNIREG from which parts were reused when he together with the other 2 founders of MySQL released the first version of MySQL in 1995.

Last week, 19 years later, a MariaDB event was held in Helsinki. It was SkySQL that arranged the first in a row of this year’s MariaDB Roadshow events. The agenda included a walkthrough of MariaDB 10.0, some roadmap and MariaDB high availability options, which consisted of MariaDB Galera Cluster and …

Why Does InnoDB Need Dictionary

InnoDB dictionary is a set of internal tables InnoDB uses to maintain various information about user tables. It serves as API between a human and the database. While the humans refer tables by their names, InnoDB works with integer identifiers. The dictionary stores correspondence between table name and index_id.

The dictionary tables are normal InnoDB tables, but they’re not visible for a user. However some versions of MySQL provide read-only access to the dictionary in information_schema database.

The dictionary is stored in ibdata1. Root page of SYS_TABLES, for example, has id 8, so it’s eighth page from the beginning of ibdata1.

The dictionary pages are in REDUNDANT format even if you use MySQL 5.6. More about record formats I will write in future posts, I hope. For now it’s enough to mention REDUNDANT is the oldest record format. It was available since 4.0 and was the …

While working with an error that my students surfaced in the Oracle Database 12c, I blogged about the limit of using a subquery in an Oracle INSERT statement, and I discovered something when retesting it in MySQL. It was a different limitation. I was also surprised when I didn’t find any mention of it through a Google search, but then I may just not have the right keywords.

The original test case uses a subquery to create a multiple row result set for an INSERT statement. Unfortunately, I discovered that you can’t always embed a UNION or UNION ALL inside a subquery. At least, you can’t when you call the subquery inside an INSERT statement. For example, let’s create a DESTINATION table and then we’ll try to insert records with a query that …

So of course Percona has documentation that explain the process. The goal of this blog is to go into a little more detail in hopes that can help someone.

Hyperlinks for review:

• CentOS - http://www.percona.com/doc/percona-xtradb-cluster/5.5/howtos/cenots_howto.html
• Ubuntu - http://www.percona.com/doc/percona-xtradb-cluster/5.5/howtos/ubuntu_howto.html
• Installing Percona XtraDB Cluster from Binaries -   
  • http://www.percona.com/doc/percona-xtradb-cluster/5.5/installation.html
…

Taxonomy upgrade extras: myenvoperationMySQL Operationsmulti instanceconsolidationBackup

FromDual has the pleasure to announce the release of the new version 1.0.5 of its popular MySQL, MariaDB and Percona Server multi-instance environment MyEnv.

The majority of improvements happened on the MySQL Backup Manager (mysql_bman) utility.

You can download MyEnv from …