The latest from the MySQL community

Recently we announced MySQL Data Recovery Portal. Here we automated some data recovery routines and published web interface to them.

First, it was a tool to estimate recovery chances from corrupted InnoDB tablespaces.

Now it’s even more exciting and useful feature – recovery table structure from FRM files online.

There are several methods to recover MySQL table structure from FRM files.

On MySQL Data Recovery Portal we utilize a combination of them.

Fake table method

The idea is to create a dummy InnoDB table, replace its .frm file with .frm file we want to recover and run SHOW CREATE TABLE.

Let’s say we have actor.frm and we want to get structure of table actor.

Algorithm is following:

Create a dummy table with the same name, actor. The …

My job is almost completely reliant upon my ability to perform work in lab of virtual machines. Almost every action plan I write is tested locally. When I need to troubleshoot an issue for a client one of the most common first steps I’ll perform is attempting to recreate the issue in a virtual environment so I can work on it there without the risk of impacting client data.

I believe that having a place to test and grow your skills is an absolute necessity for anyone working in the IT field today regardless of your specialization, even if you’re an IT generalist. But every now and then I hear about individuals who have issues with their virtual machines or with the virtual environment provided by their employer, so I figured this was a good time to share my method of creating a virtual lab. More specifically, one that allows you to do virtual work on a commodity laptop, one that won’t break down if you lose connectivity, one that …

What are odds MySQL table can be recovered?

This is the most asked question. Every single customer asks if their MySQL table can be recovered. Although it’s not possible to answer that with 100% confidence there are ways to estimate recovery chances. I will describe few tricks.

Generally speaking, if data is on media there are high odds TwinDB data recovery toolkit can fetch it. Where to look for depends on accident type.

Online MySQL data recovery toolkit

On our Data Recovery portal you can upload an .ibd file and check if the InnoDB tablespace contains any good records. The table space may be corrupt. The tool should handle that.

DROP TABLE or DATABASE with innodb_file_per_table=OFF

If …

Percona is glad to announce the new release of Percona XtraDB Cluster 5.6 on September 21st 2015. Binaries are available from downloads area or from our software repositories.

Based on Percona Server 5.6.25-73.1 including all the bug fixes in it, Galera Replicator 3.12, and on …

This post was written by Seppo Jaakola, CEO of Codership.

There appears to be great misunderstanding as to what MySQL transaction isolation levels Galera CLuster actually supports and how. This blog post tries to give answer to those uncertainties.

Galera Cluster provides SNAPSHOT ISOLATION between transactions running on separate cluster nodes. Transactions running on the same node are isolated by whatever was configured as the transaction isolation level in the MySQL configuration. So, if you have configured the default REPEATABLE READ isolation, transactions issued on the same node will behave under REPEATABLE READ semantics. However, for transactions issued on separate cluster nodes, the ‘first committer wins’ rule of SNAPSHOT ISOLATION is provided, and this will fix the lost update problem that generally hurts REPEATABLE READ isolation.

Therefore, it is not safe for the application to rely on SNAPSHOT …

I installed the MariaDB 10.1 Release Candidate. Nothing interesting happened, which from MariaDB's point of view is good. But here's how I tried to make it interesting. Some of this applies to late releases of MariaDB 10.0 as well.

Loop with MAKE INSTALL

My habit is to download the source to directory X and then say "cmake -DCMAKE_INSTALL_PREFIX=/X" (the same directory), then "make", then "make install". That doesn't work any more. Now I can't install in the same directory that I downloaded in. Not a big deal; perhaps I'm the only person who had this habit.

Crash with ALTER

In an earlier blog post General Purpose Storage Engines in MariaDB I mentioned a crash, which I'm happy to say is fixed now. Here's another way to crash, once again involving different storage engines.

Welcome to the …

Recently Aphyr (Kyle Kingsbury) published https://aphyr.com/posts/327-call-me-maybe-mariadb-galera-cluster

The article is technically valid, I am not going to dispute a conclusion Aphyr made, but it is also quite technically involved, so users who just jump to conclusion may get the wrong impression and we’re left with more questions than ever.

So, let me state what is the real conclusion of this article:
“Galera cluster does not support SNAPSHOT ISOLATION LEVEL, in contract to what was stated in the documentation”.
Following that conclusion is using Galera cluster may result in “corrupted” data.

I do not quite like the usage of the word “corrupted” here. For me, the more correct word be to use is “inconsistent”.

So with this clarification, the …

In the previous blog post we setup a replication topology with one master and 2 slaves, and we installed proxysql on a forth servers where the application should connect to.
The post was quite long, and we covered several topics, from installation and configuration of the cluster to installation of proxysql and creation of users and backends, from configuration of query rules for routing and their statistics to monitoring module and replication lag.

But ProxySQL can do more than this.
Among the most interesting features of proxysql is the ability to hold traffic until a backend is available (within a configurable time limit).
For instance, if a query should be send to hostgroup 0 but there is no servers in hostgroup 0, ProxySQL will wait until a server is available in hostgroup 0 or a timeout expires.

…

Hi all, keeping our steady release cycle, it is time again to do another preview release of MySQL Group Replication, the plugin that brings multi-master update everywhere to MySQL, like we described in Hello World post.

We are very proud to do the fourth preview release of MySQL Group Replication, version 0.5.0 based on MySQL Server 5.7.8, which introduces new exciting features, please enjoy the highlights!…

What is headless web browsing?
It's using a web-browser like application to do automated fetching and analysis of web pages, without a human user present.This is different from simply fetching HTML content via HTTP; headless web browsers typically also load images, process Javascript code, CSS and layout the page content (albeit in an invisible way). 
The developer can then use scripting (usually Javascript) to examine the page as it is laid out in memory, as if in a "real" web browser, to look at the style of text, etc.
We could even use OCR to look for text within images shown in the page. Why?

• More effectively analyse the content of pages. Lots of pages nowadays contain a huge amount of "boiler plate" uninteresting text, often in HTML elements without semantic meaning (e.g. DIV). Only by using CSS (and sometimes Javascript) are we able to have a computer see the page as a human would
• Generation …