As you know, foreign keys establish a sort of relationship between 2 tables. MySQL requires InnoDB storage engine to support foreign keys.

In our example, we have the following parent table in a MySQL 5.7.21 server:

mysqld3-(root@localhost) [sakila]> show create table actor\G
*************************** 1. row ***************************
       Table: actor
Create Table: CREATE TABLE `actor` (
  `actor_id` smallint(5) unsigned NOT NULL AUTO_INCREMENT,
  `first_name` varchar(45) NOT NULL,
  `last_name` varchar(45) NOT NULL,
  `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`actor_id`),
  KEY `idx_actor_last_name` (`last_name`)
) ENGINE=InnoDB AUTO_INCREMENT=201 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

and a foreign key is defined on the child table by using the “FOREIGN KEY… REFERENCES” syntax:

mysqld3-(root@localhost) [sakila]> show create …

Every MySQL database programmer should learn and apply the newly added MariaDB and MySQL Window Functions and Common Table Expressions(CTEs) in their daily work. Both CTEs and window functions enable easy solutions to many query challenges that in prior releases have been difficult and sometimes impossible to surmount. Mastering these features opens the door to query solutions that are more robust, execute faster, and are easier to maintain over time than prior solutions using older techniques.

In our last blog we compared User Roles in MySQL 8 vs. MariaDB.  Today, we will here compare Window Functions and Common Table Expressions in both databases.

Window Functions

While all database administrators are familiar with aggregate functions like COUNT(), SUM(), and AVG(), far less people make use of window functions in their queries.  Unlike aggregate functions, which operate on an entire table, window …

In part 1 of this series we looked at implementing support for the caching_sha2_password authentication plugin using the libmyqlclient C library.  This is possible for C based connectors or connectors that can make use of an external C library.  For some, this is not possible.  For example, Java and C# both function better if they don’t have to thunk out to an external library.  For these, implementing the MySQL client/server protocol natively is required.  This part 2 is about implementing support for the caching_sha2_password plugin natively.  It is expected that you already have a working connector and understand the client/server protocol.  For reference please internal documentation …

With MySQL 8.0, engineers improved the visibility of data locking. Usually it was not that easy to deal with the output of SHOW ENGINE INNODB STATUS and mixing Information_Schema tables like INNODB_LOCKS and INNODB_LOCK_WAITS.

So in MySQL 8.0 we instrument data locks in Performance_Schema and we changed the SYS Schema view related to the InnoDB Locks Wait too.

This means that when a transaction A is locking row R, and transaction B is waiting on this very same row, B is effectively blocked by A. What we added is extra instrumentation to expose which data is locked (R), who owns the lock (A), and who is waiting for the data (B).

Testing

Let’s have a look at this simple scenario in MySQL 5.7.21 and 8.0.4 to compare:

2 clients starting a …

As you may already know, MySQL 8.0 is coming with SQL Roles . I’ve already quoted them before in some posts (here and here). Giuseppe Maxia is doing a great job testing and promoting them (thank you for that!). Of course he also made some remarks on …

Prior to MySQL 8.0, MySQL was missing a very well know feature in other RDBMS: optimizer histograms.

The Optimizer Team implemented this feature as more and more MySQL DBAs were requesting it.

Definition

But what are histograms ? For wikipedia, a histogram is an accurate representation of the distribution of numerical data. For RDBMS, a histogram is an approximation of the data distribution within a specific column.

So in MySQL, histograms help the optimizer to find the most efficient Query Plan.

Example

To illustrate how histograms  influence the optimizer, I will use data from dbt3.

My query is simple: …

Come and listen to Percona CEO Peter Zaitsev on March 6, 2018 at 12:00 pm PST (UTC -8) / 3:00 pm EST (UTC -5) as Peter discusses Percona software news and what’s new in Percona open source software, including Percona Server for MySQL and MongoDB, Percona XtraDB Cluster, Percona XtraBackup, …

We've been busy in the MySQL Curriculum team and are pleased to announce the recent update of the MySQL Performance Tuning course.

This course has been substantially revised to take advantage of the performance enhancements available in MySQL 5.7, including new Performance Schema instrumentation and improvements in InnoDB and the Query Optimizer.

Even more so than in previous versions of the course, we try to filter out what's "nice to know" and focus on the really important configuration settings that can make the most positive impact on your server workload. We provide more in-depth coverage and practice of using system databases like Performance Schema/sys and graphical tools like MySQL Enterprise Monitor and MySQL Workbench that can help you identify performance bottlenecks and be proactive about resolving them before they start to become a major issue for your users. We also cover the use of Oracle tools like Oracle …

I’m pleased to announce that VividCortex has just released a number of new features since our last product update. If you have any questions regarding any of the updates below, contact us!

Short URLs

You can now share links with your coworkers and collaborate in VividCortex using URLs short enough to be copied and pasted into emails and chat apps, letting you get work done faster with less hassle. Just click the Link icon in the top right of the screen and copy the URL:

When anyone with appropriate permissions clicks the link, they’ll be taken directly to the URL you were looking at when you grabbed the link. Click “Freeze Time Range” to let your coworkers see the time frame you were viewing, no matter when they click the link. For more details, take a look at our …

Percona announces the release of Percona XtraDB Cluster 5.7.21-29.26 (PXC) on March 2, 2018. Binaries are available from the downloads section or our software repositories.

Percona XtraDB Cluster 5.7.21-29.26 is now the current release, based on the following:

• Percona Server for MySQL 5.7.21
• Galera/Codership WSREP API Release 5.7.21
• Galera Replication library 3.23

Starting from now, Percona XtraDB Cluster issue …