Recently during the Swedish MySQL User Group (SMUG), I presented a session dedicated to MySQL InnoDB Primary Keys.

I forgot to mention a detail that many people are not aware, but Jeremy Cole has pointed out.

Primary Key always included in secondary indexes at the right-most column

When we define a secondary index, the secondary index includes the Primary Key as the right-most column of the index. It’s silently added, meaning that it’s not visible but it’s used to point back to the record in the clustered index.

This is an example with a table having a Primary Key composed of multiple columns:

CREATE TABLE `t1` (
`a` int NOT NULL,
`b` int NOT NULL, 
`c` int NOT NULL,
`d` int NOT NULL,
`e` int …

In this blog post, we will discuss how to validate at the operating system level the effects of changing the innodb_flush_method to variations other than the default (particularly for O_DIRECT which is most commonly used) and the use of innodb_use_fdatasync.IntroductionFirst, let’s define what the innodb_flush_method parameter does. It dictates how InnoDB manages the flushing of data […]

In the world of data backup and security, physical backups play an extremely important role. Physical backup methods are faster than logical because they involve only file copying without conversion. This type of backup is suitable for large, important databases that need to be recovered quickly when problems occur.

Physical backups are the backups that consist of raw copies of the directories and files that store database contents. In addition to databases, the backup can include any related files, such as log or configuration files. Now, since backup speed and compactness are important for busy, important databases, Percona’s open source physical backup solution – Percona XtraBackup (PXB), takes into account all these aspects and benefits MySQL world with its exceptional capabilities!

This blog post will walk you through how PXB …

This blog post will focus on failover and recovery scenarios inside the InnoDB Cluster and ClusterSet environment. To know more about the deployments of these topologies, you can refer to the manuals – InnoDB Cluster and Innodb ClusterSet setup.

In the below snippet, we have two clusters (cluster1 and cluster2), which are connected via an async channel and combined, known as a ClusterSet topology. We are going to use the below topology in all of our cases.

MySQL  127.0.0.1:3308 ssl  JS > myclusterset.status({extended: 1})
{
    "clusters": {
        "Cluster1": {
            "clusterRole": "PRIMARY", …

In InnoDB, the undo log and the redo log are two indispensable components that play a vital role in maintaining data integrity and ensuring transactional consistency. Both logs are crucial in the ACID (Atomicity, Consistency, Isolation, Durability) properties of database systems. Additionally, they are essential for the Multi-Version Concurrency Control (MVCC) mechanism. In this blog post, we will delve into the differences between the InnoDB undo log and redo log, exploring their significance and providing code examples to illustrate their usage.

InnoDB Undo Log

The undo log, also known as the rollback segment, is a crucial part of the InnoDB storage engine. Its primary purpose is to support transactional consistency and provide the ability to …

This blog was originally published in July 2017 and was updated in August 2023.

It’s a pretty common question around here, so let’s see what we can do about that.

So, What is MySQL Partitioning?

Partitioning is a way in which a database (MySQL in this case) splits its actual data down into separate tables but still gets treated as a single table by the SQL layer.

When partitioning in MySQL, it’s a good idea to find a natural partition key. You want to ensure that table lookups go to the correct partition or group of partitions. This means that all SELECT, UPDATE, and DELETE should include that column in the WHERE clause. Otherwise, the storage engine does a scatter-gather and queries ALL partitions in a UNION that is not concurrent.

Generally, you must add the partition key into the primary key along …

Fragmentation is a common concern in some database systems. Highly fragmented tables can affect performance and resource allocation. But reducing fragmentation often involves rebuilding the table completely. This blog post will discuss fragmentation and its impact on InnoDB.

What is fragmentation?

We say that something is fragmented when it is formed by parts that are separate or placed in a different order than the natural one. In databases, we can experiment with different types of fragmentation:

• Segment Fragmentation: segments are fragmented; they are stored not following the order of data, or there are empty pages gaps between the data pages.
• Tablespace Fragmentation: the tablespace is stored in non-consecutive filesystem blocks.
• Table Fragmentation: data is stored not following the primary key order (heap tables), …

Learn how Multi-Valued Indexing in MySQL 8.0 can enhance query performance by efficiently indexing and querying JSON arrays. Discover the benefits, implementation steps, and considerations for optimizing your MySQL database.

1. Multi-Valued Indexing in MySQL 8.0
2. Understanding Multi-Valued Indexes and their benefits
3. Creating Multi-Valued Indexes in MySQL …

Learn how to seamlessly add a new node to MySQL Group Replication from a backup. Scale your cluster, save time, and efficiently manage data updates and recoveries.

1. Hot Physical backup approach
2. Clone plugin approach
3. Logical backup approach

We highly recommend checking out our previous blog post on …

This blog post was originally published in November 2017 and was updated in June 2023.

In this blog, we’ll provide a comparison between MariaDB vs. MySQL (including Percona Server for MySQL).

Introduction: MariaDB vs. MySQL

The goal of this blog post is to evaluate, at a higher level, MariaDB vs. MySQL vs. Percona Server for MySQL side-by-side to better inform the decision making process. It is largely an unofficial response to published comments from the MariaDB Corporation.

It is worth noting that Percona Server for MySQL is a drop-in compatible branch of MySQL, where Percona contributes as much as possible upstream. MariaDB Server, on the other hand, is a fork of MySQL 5.5. They cherry-picked MySQL features and don’t …