This Log Buffer edition covers Oracle, SQL Server and MySQL blog posts with a touch of Cloud.

Oracle:

Provisioning EBS on Oracle Cloud: Latest Enhancements

ORA-54002 when trying to create Virtual Column using REGEXP_REPLACE on Oracle 12cR2

Business rules, common sense and query performance

Problem with V$RECOVERY_AREA_USAGE view and FRA space not being reclaimed

Updated …

This Log Buffer Edition searches through various blogs of Oracle, SQL Server and MySQL and picks a few contemporary ones.

Oracle:

Comma separated search and search with check-boxes in Oracle APEX

Once you have defined your users for your Express Cloud Service, all users with the role of Database Developer or higher can access the database Service Console.

Big Data Lite 4.7.0 is now available on OTN!

Install and configure Oracle HTTP Server Standalone

Can I …

This edition of Log Buffer covers Oracle, Microsoft SQL Server, and MySQL.

Oracle:

Data Pump or Data Pain Part02 – tablespace/user

Monday Spotlight: It’s About Security – Oracle Exadata SL6

0001_specify_date_format_mask.md copy

OGG Custom Adapters: How to include a unique identifier for …

Whenever we want a query’s results sorted, you may think of using the clause “order by.” You are correct: most of the time, MySQL will return the results in expected order with “order by.”

Be careful, though. Sometimes MySQL may return results in the non-deterministic order even with “order by.”

Indeed, if a query is ordered by a non-unique column, it may return results in an unexpected order. I tested the below example on MySQL 5.1.73, 5.5.54 and 5.6.19 and got the same result. However, when I applied the same example on MySQL 5.7.17, it returned the results in an unexpected order differently.

Follow me step-by-step and see how MySQL returns results in a non-deterministic order. Step 1-4 is for MySQL 5.1.73, 5.5.54 and 5.6.19, Step 5 is for MySQL 5.7.17. After the example, I will explain the reason behind this output.

Step 1. Create the table as …

Valeriy Kravchuk’s great recent post on using oprofile to profile MySQL mentioned how pt-stalk, the script from Percona Toolkit to capture diagnostics data based on a detected condition, currently does not support the new operf comand, and relies instead on the deprecated and soon to be removed, opcontrol.

Fortunately, in the Open Source world, we deal with these situations by contributing, and this seemed a simple enough change that I could get a PR ready quickly and reply …

Why do we sometimes want to keep duplicate indexes?

I’ve done dutiful DBA work in the past to identify and remove what are commonly called duplicate indexes. That is, those indexes that look like (a) and (a,b). The thought is that a query will utilize an index as easily on (a) as on (a,b), and removing (a) will save storage cost and write performance. I’ve had the experience, though, of removing (a) and seeing performance tank.

(As an aside, these are really redundant indexes. A duplicate index would be (a,b) and (a,b) by two different names – this can commonly be done by object relational mapping (ORM) or other automated schema creation tools. I’ll call (a) and (a,b) redundant indexes below.)

This test is on Percona Server 5.7.14 with the sys schema installed and performance schema enabled.

Given two tables with the same number of rows and …

When moving your MySQL instances to AWS, you would probably have to deal with this decision. This article will highlight some of the key factors that need to be considered in order to help you determine which is the most cost-effective solution for serving your data.

Introduction

RDS is based on EC2, so in this post I will focus on the benefits and disadvantages of using the former, versus migrating MySQL into user-managed EC2 instances.

The value of RDS resides in simplified provisioning and administration. Several of the most common maintenance tasks such as minor version upgrades, backups, and slave creation are automated and can be managed from the AWS console. On the other hand, RDS imposes some limitations to MySQL functionality so it could be offered “as a Service” while delivering a safe and consistent user experience. Within those limitations we can mention:

• Storage …

A quick look at ProxySQL

There is a lot of buzz in the MySQL community around ProxySQL, an open-source SQL-aware proxy. I was lucky enough to give a ProxySQL Tutorial at PerconaLive Amsterdam 2016 with the creator of ProxySQL, René Cannaò.

Some of ProxySQL’s features include:

• Query rules based on Google’s RE2-style regex
• Failover detection
• Connection multiplexing

ProxySQL’s approach to implementing regex-style query rules opens the door to some pretty fascinating possibilities. Just to name a few examples:

• Read/write splitting between the write master and read slaves
• Query firewall, for those times you wish you could prevent queries from hitting the database. Perhaps you are …

What is InnoDB Cluster?

Hot off of Oracle Open World 2016 is the lab release of MySQL’s InnoDB Cluster.

InnoDB Cluster uses the Group Replication plugin to allow for virtually synchronous replication, while also providing a MySQL Router that is aware of the cluster state. By connecting your application to the router, your application will be able to withstand failover of any node participating in the cluster.

InnoDB Cluster also provides a new MySQL Shell to interact with the cluster commands.

MySQL’s server team gives us a very good hands-on tutorial if you’re interested in getting …

It is a common auditing requirement to log user connection events, including whether or not authentication was successful.
There are a number of alternatives available for MySQL, but unfortunately there is no built-in functionality at the time of this writing. In this post we will discuss auditing MySQL users with McAfee plugin, which is available under GPL Version 2 license.

Installation instructions

These apply to debian-based hosts, but instructions for red hat are similar.

1. Download latest plugin release from github.

At the time of this post for MySQL 5.5 you can get:

wget https://bintray.com/mcafee/mysql-audit-plugin/download_file?file_path=1.0.9-release%2Faudit-plugin-mysql-5.5-1.0.9-585-linux-x86_64.zip

2. Decompress …