Do you wonder if MySQL tells you the truth about writes to tables that have foreign key constraints? The situation is complex, and getting visibility on what is really happening can be a problem.

I found this issue intriguing and decided to share and highlight some examples.

Query Plan

Let us take this example table:

CREATE TABLE `product` (
  `category` int NOT NULL,
  `id` int NOT NULL,
  `price` decimal(10,0) DEFAULT NULL,
  PRIMARY KEY (`category`,`id`)
) ENGINE=InnoDB;

We want to know how costly an example UPDATE against this table will be:

mysql > EXPLAIN update product set id=id+1 where id=65032158 and category=3741760\G
*************************** 1. row ***************************
           id: 1
  select_type: UPDATE
        table: product
   partitions: NULL
         type: range
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 8
          ref: const,const
         rows: 1 …

MySQL Shell For VS Code integrates the MySQL Shell directly into VS Code development workflows and was released last week. This extension to the popular VS Code platform enables interactive editing and execution of SQL for MySQL Databases and optionally the MySQL Database Service for several simultaneous sessions.  It is a preview release and not ready for production but it does have several features that may make the MySQL GUI of choice.

Installation

The installation itself is easy but you will need to download the code from here and not the usual places for MySQL products.  You will, of course, have to have VS Code installed first, and be warned that some of the more tantalizing links for things like documentation are not connected.

MySQL Shell for VS Code installation screen and yes, you will need VS Code installed first.

Usage

The interface is familiar to that of MySQL Workbench but …

The utf8mb4 character set is the new default as of MySQL 8.0, and this change neither affects existing data nor forces any upgrades.

Migration to utf8mb4 has many advantages including:

• It can store more symbols, including emojis
• It has new collations for Asian languages
• It is faster than utf8mb3

Still, you may wonder how migration affects your existing data. This blog covers multiple aspects of it.

Storage Requirements

As the name suggests, the maximum number of bytes that one character can take with character set utf8mb4 is four bytes. This is larger than the requirements for utf8mb3 which takes three bytes and many other MySQL character sets.

Fortunately, utf8mb3 is a subset of …

Oracle released MySQL 8.0.28 on January 18th with little fanfare, as part of their four times a year release cycle.  So what is included in the new release? Over the past few years, there have been some cool new features included in these ‘dot’ releases that some in the community say would have been better off being labeled as a major release. But what is in .28? Below are the more interesting changes in the database server and the shell, as there was not a whole lot changed in the other products such as router or MEM… I put my asides in italics and my views probably do not reflect the views of anyone else.

And remember, 8.0.29 is due in April.

The TL;DR

The TL;DR synopsis is that a lot of excellent work went into MySQL Server & shell 8.0.28 but the pressing question is do you really need to install it right away?  On the scale from ‘you probably should wait to upgrade’ to ‘update ASAP’ …

KMIP (Key Management Interoperability Protocol) is an open standard developed by OASIS (Organization for Advancement of Structured Information Standards) for the encryption of stored data and cryptographic key management.

Percona Server for MySQL 8.0.27 and Percona XtraBackup 8.0.27 now include a KMIP keyring plugin to enable the exchange of cryptographic keys between a key management server and the database for encryption purposes. The procedure to use them with HashiCorp Vault Enterprise is described below.

Install Hashicorp Vault Enterprise

We will first install Hashicorp Vault Enterprise on Ubuntu Linux “Bionic” and then enable …

It is always hard to select a CPU for your own purpose. You could waste hours reviewing different benchmarks, reviews, and bloggers, and in the end, we would limit all our requirements to performance and price. For performance measuring we already have some specific metrics (e.g. in MHz to some specific tool), however, for economic comparison, it is quite hard.  Mostly we are limited by our budget. Again, for our personal purposes, we are limited only with the cash in our pockets. It is easy to compare only two or three CPUs; it is required just to compare their price and performance and then create a simple bar plot and then check the results. However, what do you do if you have at least three types of CPU, a different number of CPUs cores on board, and seven different scenarios?  It was a challenge to do it for performance, and for economic efficiency, it has become a nightmare. For a one-time purchase, it should be easier than for the …

Working with hundreds of different customers I often face similar problems around running queries. One very common problem when trying to optimize a database environment is index usage. A query that cannot use an index is usually a long-running one, consuming more memory or triggering more disk iops.

A very common case is when a query uses a filter condition against a column that is involved in some kind of functional expression. An index on that column can not be used.

Starting from MySQL 8.0.13 functional indexes are supported. In this article, I’m going to show what they are and how they work.

The Well-Known Problem

As already mentioned, a very common problem about index usage is when you have a filter condition against one or more columns involved in some kind of functional expression.

Let’s see a simple example.

You have a table called products containing the details of your products, …

With modern application design, systems are becoming more diverse, varied and have more components than ever before. Developers are often forced to become master chefs adding the ingredients from dozens of different technologies and blending them together to create something tasty and amazing. But with so many different ingredients, it is often difficult to understand how the individual ingredients interact with each other. The more diverse the application, the more likely it is that some seemingly insignificant combination of technology may cause cascading effects.

Many people I talk to have hundreds if not thousands of different libraries, APIs, components, and services making up the systems they support. In this type of environment, it is very difficult to know what small thing could add up to something much bigger. Look at some of the more recent …

First I want to thank everyone who attended my November 16, 2021 webinar “MySQL Performance for DevOps“. Recording and slides are available on the webinar page.

Here are answers to the questions from participants which I was not able to provide during the webinar.

Q: Hi! We have troubles with DELETE queries. We have to remove some data periodically (like, hourly, daily) and we have short-term server stalls during these DELETEs. Server is running on modern NVMe’s so we wonder why do we have this situation. Those DELETE’s are not so large, like 10 000 – 15 000 records, but tables on which DELETE’s are performed update frequently.

A: I would test if a similar

DELETE

  statement is slow when you run it on …

Well, let me say if that happens it’s because there is a logic mistake in your application. But you need to know and understand what happens in MySQL to be able to avoid the problem. 

In short, the WHY of this article is to inform you about possible pitfalls and how to prevent them from causing you damage.

Let us start by having a short introduction to what Repeatable reads are about. Given I am extremely lazy, I am going to use (a lot) existing documentation from the MySQL documentation.

Transaction isolation is one of the foundations of database processing. Isolation is the I in the acronym ACID; the isolation level is the setting that fine-tunes the balance between performance and reliability, consistency, and reproducibility of results when multiple transactions are making changes and performing …