MySQL Tech-Feed (en)

In my former Blog Post Partial Table or Schema restore from mariabackup full backup we worked out the basics of a partial restore of a table into a MariaDB database instance.

An now we use this know-how to try the same procedure on a Galera Cluster.

The backup is done in the exact same way as described in the mentioned article. We can even use the backup made there.

For the restore we use the following procedure:

Prepare and Restore a table

# BACKUPDIR="/home/mysql/bck/qamariadb105/daily"
# …

For me it was for a long time not clear if a mariadb-backup full backup can be used to do partial table or schema restores. Now we faced this challenge with a customer. So time to try it out…

This test was made with MariaDB 10.5.5. So it may not work with some older MariaDB releases…

Backup

Because I do not know during the backup if I need a full or a partial restore I always want to do a full mariadb-backup backup!

The full backup can be done as normal but the prepare should not be done yet …

Table of Contents

• Global Options
• Service Options
• Server Options
• Routing Modules
• Listener Options
• Monitor Options
• Filter Options

Global Options

FromDual has the pleasure to announce the release of the new version 2.2.2 of its popular Backup and Recovery Manager for MariaDB and MySQL (brman).

The new FromDual Backup and Recovery Manager can be downloaded from here. The FromDual Repositories were updated. How to install and use the Backup and Recovery Manager is describe in FromDual Backup and Recovery Manager (brman) installation guide.

In the inconceivable case that you find a bug in the FromDual Backup and Recovery Manager please report it to the …

How could the following SQL queries be improved performance wise and otherwise and can you also explain why your change is more optimal?

Please consider, when testing, that your results are not confused by the Query Cache or by reading data from your I/O system which are an order of magnitude faster (Query Cache) or slower (I/O) than the in-memory behaviour.

Table of Contents

• Covering function
• LIKE search
• Covering function twice
• Compare 2 indexed columns
• Function and 2 indexed columns
• Time series problem …

When it comes to SQL Query tuning with customers we often get the slow running SQL query and possibly, in good cases, also the table structure. But very often, for various reasons, we do not get the data.

SQL query tuning on an empty table or a table with only little data is not really fun because either the results of the optimizer have nothing to do with reality or the response times do not really show if your change has improved anything. For example if your query response time before the change was 2 ms …

And this is what the Linux kernel documentation says about it: https://www.kernel.org/doc/Documentation/networking/bonding.txt

Yes, I know, MyISAM is deprecated and unofficially discontinued by the vendors. But we still have from time to time customers using MyISAM and even evangelize for MyISAM…

And to be honest in some cases MyISAM has even advantages (beside some huge disadvantages) over other Storage Engines (simple file copy, footprint, single-query latency, …). But most of our customers are not aware of these advantages and are using MyISAM just because they did it since ever…

One of the biggest problems …

802.3ad bond interface have show high RX dropped packets

I found a god explanation for dropped packages on bonded interfaces: [ 1 ]

This is related to the bonding mode and _not_ a bug. The bonding module will drop duplicate frames received on inactive ports, which is normal behaviour. Overall the packets should be getting into the machine without problems since they are received on the active slave. To confirm this do the following

1) Check dropped packets from all interfaces. So if eth0/eth1 are …

Repositories from your favourite Linux distribution and from your favourite database software vendor get regular package updates. If you do periodic system upgrades (for example every 2 weeks as we do) you get the newest packages of a release series.
Unfortunately recently the software vendors started not only to fix bugs in new releases but also to introduce new features. And when you fix bugs or introduce new stuff new bugs might appear.
To avoid being hit unexpectedly by new bugs you do not want to …

When you are for too long in business you think you know already everything and you are getting lazy. This happened to me again a few weeks ago. A customer asked me about the SQL Error Log Plugin. First I though he was talking about the MariaDB Error Log or the General Query Log. But then I have learned that there is something “new” I did not know yet…

MariaDB introduced in 5.5.22 (March 2012) a new plugin called the SQL Error Log Plugin. This Plugin collects all the errors which were …

With the FromDual Ops Center file transfer tool you can easily upload files from your personal computer to the focmm machine, download files from the focmm machine to your personal computer or transfer files from the focmm machine to any of your database machines or between them. This feature is made for importing, exporting or transferring data from, to or between your different database instances. For example to copy a production schema to a testing database instance.

For backup and restore of a database …

One of the tools of FromDual Ops Center for MariaDB and MySQL is the centralized crontab for all of your database machines. Instead of maintaining various different crontabs on different machines you can manage them now in one place within the Ops Center.

Under the Tools menu on the left you find Crontab. Here you get a first overview of crontab jobs available:

• The first column shows if the crontab job is active or not.
• The second column indicates the O/S user the crontab job should run as.
• Then we have …

We have found a strong correlation between VMware snapshots and Veeam backups and those dropped packets.

In a recent customer engagement we experienced a lot of corrupted (normal) indexes and also corrupted full-text indexes on InnoDB tables in a Galera Cluster (v10.4.13).

In the error log we did not see which table it was but we have only a few log entries every here and there indicating a full-table index is corrupt:

2020-07-08 22:09:03 0 [ERROR] InnoDB: (Duplicate key) writing word node to FTS auxiliary index table.
2020-07-08 22:09:06 0 [ERROR] InnoDB: (Duplicate key) writing word node to FTS auxiliary …

Asking stupid questions and googling for them is fun some times…

Today I was asking myself if one could rise the file limit for a running MariaDB mysqld process online without restarting the database instance?

And I found an answer on serverfault: Set max file limit on a running process:

PID=$(pidof mysqld)

grep -e 'Max open files' -e Limit /proc/${PID}/limits 
Limit                     Soft Limit           Hard Limit           Units     
Max open files            1024                 4096 …

With this new version of fpmmm you probably get a new warning in your fpmmm error log:

INFO: FromDual Performance Monitor for MySQL and MariaDB (fpmmm) (1.2.0) run started.
WARN:     P_S Metadata Lock instrumentation is disabled. (rc=1411)
INFO: FromDual Performance Monitor for MySQL and MariaDB (fpmmm) run finished (rc=0).

In this fpmmm release we start monitoring MariaDB/MySQL Metadata locking problems. For this new functionality the Metadata locking plugin in MariaDB or the Metadata …

Sources:

• RSyslog Documentation
• How to Configure Remote Logging with Rsyslog on Ubuntu 18.04

This notes are intended for Ubuntu 18.04!

Install and Configure Rsyslog Server

dpkg -l | grep rsyslogd
apt-get update && apt-get install rsyslog

systemctl start rsyslog
systemctl enable rsyslog
systemctl status rsyslog

Check rsyslog version (v7 vs. v8!):

rsyslogd -v

General configuration

#
# /etc/rsyslog.conf
#

# provides UDP syslog reception
module(load="imudp")
input(type="imudp" …

FromDual has the pleasure to announce the release of the new version 1.2.0 of its popular Database Performance Monitor for MariaDB and Galera Cluster fpmmm.

The FromDual Performance Monitor for MariaDB (fpmmm) enables DBAs and System Administrators to monitor and understand what is going on inside their MariaDB database instances and on the machines where the databases reside.

More detailed information you can find in the fpmmm Installation Guide.

Download

The new FromDual Performance Monitor for MariaDB ( …

FromDual has the pleasure to announce the release of the new version 1.2.0 of its popular Database Performance Monitor for MySQL fpmmm.

The FromDual Performance Monitor for MySQL (fpmmm) enables DBAs and System Administrators to monitor and understand what is going on inside their MySQL database instances and on the machines where the databases reside.

More detailed information you can find in the fpmmm Installation Guide.

Download

The new FromDual Performance Monitor for MySQL (fpmmm) can be downloaded …