MySQL membership conditions are in the MySQL 8 Documentation. They’re found in the 13.2.11.3 Subqueries with ANY, IN, or SOME section. The IN and =ANY operators both perform equality matches with one twist. The IN operator works with a set of values or a subquery but the =ANY operator only works with a subquery.

I created the digits, letters, and words tables for this example. They hold the following values respectively:

• The numbers table holds the values of 1, 2, 3, and 4
• The letters table holds the values of 'a', 'b', 'c', and 'd'
• The words table holds the values of 'Captain America', 'Iron …

There was an excellent question from Francis on my MySQL X DevAPI tutorial on how to work with NULL values:

Is it possible to store an attribute with the null value, and how to find it (xxx is null ?

It may sound like a trivial question, but the answer is not all that simple, so instead of just replying directly to the comment, I think it is worth covering the subject of NULL values in the X DevAPI in a separate post.

The Short Story

In short there are two ways to work with “not a value” in the X DevAPI. One way is to not set a value for those fields in which case you can compare the retrieved values with IS NULL as you would for a relational table, for example in MySQL Connector/Python:

# Find documents where "Birthday IS NULL"
stmt_find = …

We recently saw how the new Invisible Column feature works in MySQL since 8.0.23 and how we can use it as a Primary Key for InnoDB tables when no Primary Key was defined.

As I wrote earlier, a good Primary Key is important for InnoDB (storage, IOPS, secondary indexes, memory…) but there is another important domain where a Primary Key is important in MySQL: replication !

Asynchronous Replication

When using “traditional” replication, if you modify a record (UPDATE and DELETE), the record(s) to modify on the replica are identified using indexes, and of course the Primary Key if any. The hidden global 6-bytes auto generated by InnoDB primary key is never used as never exposed and as it’s global, …

Although how range_optimizer_max_mem_size operates is explained in the official doc, it’s not a well-known variable and surely not a variable you need to modify under most circumstances. But from time to time we get some performance tickets related to this.

What problem does this variable cause if it is not properly sized? Let’s find out with an example!

Given the following table definition:

CREATE TABLE `joinit` (
  `i` int(11) NOT NULL AUTO_INCREMENT,
  `s` varchar(64) DEFAULT NULL,
  `t` time NOT NULL,
  `g` int(11) NOT NULL,
  PRIMARY KEY (`i`)
) ENGINE=InnoDB AUTO_INCREMENT=2490316 DEFAULT CHARSET=latin1

With ~2M rows

select count(*) from joinit ;
+----------+
| count(*) |
+----------+
|  2097152 |
+----------+

With the default value of  range_optimizer_max_mem_size = 8388608, the following …

… an expedition to uncover (and fix) database performance issues!

© 2021 Tiago L. Alves. All rights reserved.

One of the worse things that can happen when upgrading to a newer database version is discovering that the performance is not as good as before. Despite the effort put into gate-keeping MySQL NDB Cluster’s strict performance requirements, one of our customers found a performance regression when upgrading from our 7.4 version to our 7.6 version. How did that happen when our automated performance test suite failed to show it? To answer that, and fix the issue we enrolled on a database performance archaeology expedition…

When your performance is not good enough

MySQL NDB Cluster is an open-source in-memory distributed database developed for high-availability (99.999% or more) and predictable query times. It can be found at the core of gaming, banking, telecommunication, and online services. …

This article is the second part of the series related to MySQL Invisible Column started here.

This post covers why Invisible Column is important for InnoDB Storage Engine.

To start, let me explain briefly how InnoDB deals with Primary Key and why an good primary key is important. And finally, why having a Primary Key is also important.

How does InnoDB Stores Data?

InnoDB stores data in table spaces. The records are stored and sorted using the clustered index (the primary key): they are called index-organized tables.

All secondary indexes also contain the primary key as the right-most column in the index (even if this is not exposed). That means when a secondary …

The MySQL Development Team is happy to announce a new 8.0 Maintenance Release of MySQL Shell AdminAPI – 8.0.23!

In addition to several bug fixes and minor changes, some significant enhancements regarding monitoring/troubleshooting and performance were included.

MySQL Shell AdminAPI Cluster diagnostics

Checking how a Cluster is running and, whenever the cluster is not 100% healthy, perform troubleshooting tasks is certainly one of the main tasks of a DBA.…

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In a previous blog, we had discussed how to migrate a standalone Moodle setup to scalable setup based on a clustered database.  The next step you will need to think about is the failover mechanism - what do you do if and when your database service goes down. 

A failed database server is not unusual if you have MySQL Replication as your backend Moodle database, and if it happens, you will need to find a way to recover your topology by for instance promoting a standby server to become a new primary server. Having automatic failover for your Moodle MySQL database helps  application uptime. We will explain how failover mechanisms work, and how to build automatic failover into …

With the new MySQL 8.0.23, something very interesting has been released: Invisible Column.

This is the first post dedicated to this new feature, I expect to write a series of 3. This one is the introduction.

Prior to MySQL 8.0.23, all columns of a table were always visible (if you had the privilege to see it). Now, an invisible column can be specified and will be hidden to queries. It can always be accessed if explicitly referenced.

Let’s see how it works:

create table table1 (
   id int auto_increment primary key, 
   name varchar(20), 
   age int invisible);

In the table description we can see the INVISIBLE keyword in the Extra column:

desc table1; …

I recently published a blog post about a portfolio project I am developing using the LAMP stack, Bootstrap 4, jQuery, and the MVC (Model-View-Controller) design pattern in core PHP. In this post, I will introduce an additional feature I integrated into the existing project.

Image by xresch from Pixabay

Self-Promotion:

If you enjoy the content written here, by all means, share this blog and …