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 …

In this blog post, we will compare the performance of performing a backup from a MySQL database using mysqldump, MySQL Shell feature called Instance Dump, mysqlpump, mydumper, and Percona XtraBackup. All these available options are open source and free to use for the entire community.

To start, let’s see the results of the test.

Benchmark Results

The benchmark was run on an …

Percona XtraDB Cluster 8.0.25 (PXC) has introduced a new option to perform online schema modifications: NBO (Non-Blocking Operation).

When using PXC, the cluster relies on the wsrep_OSU_method parameter to define the Online Schema Upgrade (OSU) method the node uses to replicate DDL statements. 

Until now, we normally have three options:

• Use Total Isolation Order (TOI, the default)
• Use Rolling Schema Upgrade (RSU)
• Use Percona’s online schema change tool (TOI + PTOSC)

Each method has some positive and negative aspects. TOI will lock the whole …

We have a quickstart guide for how to install Percona Distribution for MySQL Operator on minikube. Installing the minimal version works well as it is described in the guide. After that, we will have one HAproxy and one Percona XtraDB Cluster (PXC) node to work with.

Minikube provides Kubernetes locally. One can try using the provided local k8s to try the more advanced scenarios such as the one described here.

Following that guide, everything works well, until we get to the part of deploying a cluster with

deploy/cr.yaml

Even after that, things seemingly work.

$ kubectl get pods
NAME READY STATUS RESTARTS …

For a long time, MyDumper has been in Max Bubenick’s personal GitHub repository. Now, we decided to move to a new MyDumper’s Organization as requested earlier this year by a user from the community.

There were also two other reasons why we decided to move it. The first one is related to how the project is evolving, and the second is that it will allow us to implement integrations to other projects.

We can see the evolution of the project, noting the increase in commits of the last year:

We tried to keep the release cycle every two months, focusing on closing as many bugs as possible and implementing new features requested. It was not an easy task, as lots of changes had to be implemented in mydumper and myloader engine to allow the new features to be developed. 

Working on a real case scenario in a five node Percona XtraDB Cluster (PXC), we were forced to use wsrep_sync_wait = 1, because the app does reads-after-write and we send reads to all the nodes. We had the idea to leave some nodes in DESYNC mode to reduce the flow control messages during peak load and expected to have a steadier write throughput keeping the read consistency.

We decided to test Perconas’s new PXC Scheduler Handler which is an application that manages integration between ProxySQL and Galera/PXC (the scope is to maintain the ProxySQL mysql_server table, if a negative scenario occurs, like: failures, service degradation, and maintenance). However, we realized that when a node is in DESYNC mode, it is kicked out of the read hostgroup. That is …

The new MyDumper 0.11.3 version, which includes many new features and bug fixes, is now available.  You can download the code from here.

We are very proud to announce that we were able to achieve the two main objectives for the milestone ZSTD and Stream support!  We added four packages with ZSTD support because not all the distributions have support for v1.4 or higher. Package libzstd is required to use ZSTD compression. ZSTD Bullseye package is only available with libraries for Percona Server for MySQL 8.0. There are two main use cases for the Stream functionality:

• Importing while you are exporting
• Remote backups
…

A recommendation we often give to our customers is along the lines of “archive old data” to reduce your database size. There is a tradeoff between keeping all our data online and archiving part of it to cold storage.

There could also be legal requirements to keep certain data online, or you might want to query old data occasionally without having to go through the hassle of restoring an old backup.

In this post, we will explore a very useful feature of AWS RDS/Aurora that allows us to export data to an S3 bucket and run SQL queries directly against it.

Archiving Data to S3

Let’s start by describing the steps we need to take to put our data into an S3 bucket in the required format, which is called Apache Parquet.

Amazon states the Parquet format is up to 2x faster to export and consumes up to 6x less storage in S3, compared to other text formats.

1. Create a snapshot of the database (or …

If you ever had to deal with performance and/or disk space issues related to temporary tables, I bet you eventually found yourself puzzled. There are many possible scenarios depending on the type of temporary table, settings, and MySQL version used. We have observed a pretty long evolution in that matter due to a couple of reasons. One of them was the need to completely eliminate the need to use the deprecated MyISAM engine, and at the same time introduce more performant and reliable alternatives. Another set of improvements was required related to InnoDB, where it was necessary to lower the overhead of temporary tables using that engine.

For that reason, I decided to gather them in a sort of summary which may help to troubleshoot their usage. Due to vast changes between major MySQL releases, I divided the article by them.

…

MySQL stores active table descriptors in a special memory buffer called the table open cache. This buffer is controlled by configuration variables table_open_cache that hold the maximum number of table descriptors that MySQL should store in the cache, and table_open_cache_instances that stores the number of the table cache instances. With default values of table_open_cache=4000 and table_open_cache_instances=16, MySQL will create 16 independent memory buffers that will store 250 table descriptors each. These table cache instances could be accessed concurrently, allowing DML to use cached table descriptors without locking each other.

If you use only tables, the table cache does not require a lot of memory because descriptors are lightweight, and even if you significantly increase the value of the table_open_cache, the required memory amount would not be so high. For example, …