The latest from the MySQL community

Following my post MySQL/ZFS Performance Update, a few people have suggested I should take a look at BTRFS (“butter-FS”, “b-tree FS”) with MySQL. BTRFS is a filesystem with an architecture and a set of features that are similar to ZFS and with a GPL license. It is a copy-on-write (CoW) filesystem supporting snapshots, RAID, and data compression. These are compelling features for a database server so let’s have a look.

Many years ago, in 2012, Vadim wrote a blog post about BTRFS and the results were disappointing. Needless to say that since 2012, a lot of work and effort has been invested in BTRFS. So, this post will examine the BTRFS version that comes with the latest Ubuntu LTS, 20.04. It is not bleeding edge but it is likely the most 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 …

CodeIgniter 4 Query Builder class has an update() function used to process UPDATE Data Manipulation Language (DML) commands. Using update() as a standalone function call is perfectly valid. However, there is also a set() function used for setting column values as you would with the SET keyword in an SQL UPDATE statement. Used in conjunction with the Query Builder where() function, you can easily UPDATE column values for an individual row or multiple rows. Continue reading for more information…

Image by  …

To copy the data of the particular column of the table to another table/server, We have an option to export the data as CSV and import the data back to a different table. But when the table size is large and we need to copy the data only for the required data to the target table will cause the load in the server since the table scanning is huge.

To overcome this, we have the pt-archiver copy the data from the source table to the destination as a whole or only for required columns. And also we can do this in a controlled manner as well. So there will be no performance impact even on the production time.

Source table structure :

mysql> show create table source\G
*************************** 1. row ***************************
       Table: source
Create Table: CREATE TABLE `source` (
  `id` int unsigned NOT NULL …

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

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

Until now we normally have 3 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 cluster from being able to accept data modifications for the entire time it takes to perform the DDL operation. RSU …

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

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

Until now we normally have 3 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 cluster from being able to accept data modifications for the entire time it takes to perform the DDL operation. RSU …

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 …

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 …

MySQL window functions can be used to calculate daily averages or moving averages for a 24h time window relatively easily. In an earlier article

basic window functions were already discussed. In this article, we want to see how we can get daily buckets and moving averages.

A sample program is available, as usual, on GitHub

.

Getting sample data

We will be working with a data table named data, with three columns: a sensor id, a measurement datetime d and a metric value m that was sampled at that time. The table definition looks like this: …

While exporting the table with MySQL native utility, we don’t have any control on the process, and also there will be no progress update as well on the process completion. So when exporting the larger table will consume high resource utilization and also the disk space usage will also be high.

MySQL shell utility will make the process easier. It will export the table and we can import the data back with a parallel thread and also will provide the current progress status on export/import progress.

util.exportTable() utility was introduced in Shell – 8.0.22 version, will export the data in a controlled manner. We can store the data in either local or Cloud Infrastructure Object Storage bucket as well.

We will see about the compression ratio along with the time taken for native MySQL vs Shell utility

Feature :

• Compression
• Progress status
• Supported output …