VividCortex is sponsoring and exhibiting at AWS Re:Invent October 6 - 9 this year. We will be serving up hats and database monitoring demos, so come check us out!

Click here for more details and registration.

I have been working for a very large Australian website for over six years and during this period have been fortunate enough to hire many Infrastructure Operations Engineers that now work for that company. I want to detail the evolution of the hiring process and what I have driven it to over the last six years.
How was I hired This is the interview process I went through at my current company:

• A technical and cultural pre-screening from a recruiter
• A short phone interview with a small set of adhoc questions around technical skill set. How does DNS work?
• An hour long face to face interview with the hiring manager and another senior engineer testing both technical capability and culture fit
• Another hour long face to face interview with a HR representative testing cultural fit 
• Lastly, a reference check to confirm technical capability and cultural fit performed over …

http://dom.as/2015/07/30/on-order-by-optimization/

An insightful exploration by Domas (Facebook) on how some of the MySQL optimiser’s decision logic is sometimes naive, in this case regarding ORDER BY optimisation.

Quite often, “simple” logic can work better than complex logic as chasing all the corner cases can just make things worse – but sometimes, logic can be too simple.

Everything must be made as simple as possible, but no simpler.
— Albert Einstein / Roger Sessions

VividCortex is sponsoring and exhibiting at Percona Live EU in Amsterdam September 21 - 23rd. Stop by our booth to get a free product demo and see how we can revolutionize your database monitoring.

Baron Schwartz will also be speaking on Redis Eye for the MySQL Guy, so be sure to learn from his experience.

Click here for more details and registration.

This Log Buffer Edition throws spotlight on some of the salient blog posts from Oracle, SQL Server and MySQL.

Oracle:

• STANDARD date considerations in Oracle SQL and PL/SQL
• My good friend, Oracle icon Karen Morton passed away.
• Multiple invisible indexes on the same column in #Oracle 12c
• Little things worth knowing: Data Guard Broker Setup changes in 12c …

Fri, 2015-07-31 12:14guillaumelefranc

Mandatory disclaimer: the techniques described in this blog post are experimental, so use at your own risk. Neither me nor MariaDB Corporation will be held responsible if anything bad happens to your servers.

Context

MaxScale 1.2.0 and above can call external scripts on monitor events. In the case of a classic Master-Slave setup, this can be used for automatic failover and promotion using MariaDB Replication Manager. The following use case is exposed using three MariaDB servers (one master, two slaves) and a MaxScale server. Please refer to my Vagrant files if you want to jumpstart such a testing platform.

Requirements

• A mariadb-repmgr binary, version 0.4.0 or above. Grab it from the github Releases page, and extract in /usr/local/bin/ on your MaxScale server. …

 Article on Information Age:

From obscurity to the mainstream, the journey of MySQL shows the power of the open source community to drive innovation. Read the full article here: http://goo.gl/bqFZPb

Welcome to the 10th episode in the MySQL QA series! Today we’ll talk about reproducing and simplifying: How to get it Right.

Note that unless you are a QA engineer stuck on a remote, and additionally difficult-to-reproduce or difficult-to-reduce bug, this episode will largely be non-interesting for you.

However, what you may like to see – especially if you watched episodes 7 (and possibly 8 and 9) – is how reducer automatically generates handy start/stop/client (cl) etc. scripts, all packed into a handy bug tarball, in combination with the reduced SQL testcase.

This somewhat separate part is covered directly after the introduction (ends at 11:17), as well as with an example towards the end of the video (starts at time index 30:35).

The “in between part” (11:17 to 30:35) is all about reproducing and simplifying, which – unless you are working on a remote case – can likely be skipped by …

Taxonomy upgrade extras:  max_used_connections user account connection configuration

How many connections can be opened concurrently against my MySQL or MariaDB database can be configured and checked with the following command:

SHOW GLOBAL VARIABLES LIKE 'max_connections';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 505   |
+-----------------+-------+

If this limit was ever reached in the past can be checked with:

SHOW GLOBAL STATUS LIKE 'max_use%';
+----------------------+-------+
| Variable_name        | …

Generally in MySQL we send queries massaged to a point where optimizer doesn’t have to think about anything. In our major user database environment 99.9% of queries don’t have alternative query plans available (either because of forced indexes or just straightforward Primary Key read). We have various other systems and from time to time we have to do SQL work there and chase optimizer errors.

There’re multiple places where optimizer can make a choice in very basic queries, for example:

• Which index returns less rows
• Which index can be used for ORDER BY

A query that I was looking asked a very basic question, on a job instances table, show state and status for latest-by-ID entry for job name=’Ship Christmas Presents’ (real name was a bit different ;-). So, it was SELECT c,d FROM t WHERE b=X ORDER BY a DESC LIMIT 1, where PK is (a) and a possible index is on …