The latest from the MySQL community

ARM community that has developers from varied organizations has contributed some really good patches to MySQL. Most of them are awaiting acceptance. Blog is meant to analyze these patches along with their pros and cons. Hopefully this would help ease MySQL/Oracle to accept these long-awaited patches.

Community Patches

1. Optimizing checksum

• MySQL uses 2 types of checksum: crc32c and crc32. They both are different since both uses different polynomials.
  • crc32c is used in MySQL by InnoDB to calculate page-checksum.
  • crc32 is used in MySQL for table checksum, binlog-checksum, etc…

crc32c

• Page checksum is calculated during each page read/write so crc32c can quickly show up as one of the top functions in perf report. Ensuring use of optimized versions of it could help improve the overall throughput of the system.
…

For more information on how to create a service look at man systemd.service Install Directory for MCM installation is /opt Download latest tar package of MCM from edelivery.oracle.com or support.oracle.com (today this is package: MySQL Cluster Manager 1.4.8 TAR for Generic Linux x86 (64bit)) Run commands below once you have downloaded the MCM package:

sudo su -
cd /opt
tar xzf /tmp/mcm-1.4.8-linux-glibc2.12-x86-64bit.tar.gz
mv mcm-1.4.8-linux-glibc2.12-x86-64bit mcm
cp /opt/mcm/mcm1.4.8/etc/mcmd.ini /opt/mcm/
mkdir /opt/mcm/mcm_data

Set manager-directory to folder /opt/mcm/mcm_data in configuration file:

cat /opt/mcm/mcmd.ini | sed 's/^##manager-directory.*/manager-directory = \/opt\/mcm\/mcm_data/' >> /opt/mcm/mcmd.ini

Structure should be:

 …

The MySQL Document Store is an quick and easy to use NoSQL JSON Document Database that was designed to be easy to use.  But there is one thing that may not be obvious if you are working to modify multiple documents. 

So let us start with a very simple example collection of three documents.

>db.xyz.find()
{
    "a": 1,
    "_id": "00005eb2ba3c0000000000000004"
}
{
    "b": 2,
    "_id": "00005eb2ba3c0000000000000005"
}
{
    "c": 3,
    "_id": "00005eb2ba3c0000000000000006"
}
3 documents in set (0.0008 sec)

So we have three different documents and later determine we need to add the same key/value pair for all of them.

But the following will not work:

>db.xyz.modify().set("fizz","buzz")
…

In Percona’s Managed Services, we start up and shut down MySQL servers all the time.  Over the years, we’ve seen various issues occur due to the way servers are shut down.  No matter if it is a situation where unexpected errors appear in the log or you’re stuck waiting for hours for a server to finishing shut down… Here are some steps we can take to minimize any trouble and prepare MySQL for shutdown.

This list of “super safe practices” was born from lessons we’ve learned in a wide variety of MySQL environments.

1. Stop Replication.

Under some (rare) circumstances, a slave may try to startup in the incorrect position. To help minimize this risk, stop the IO thread first so it’s not receiving new events.

STOP SLAVE IO_THREAD;

Wait for the SQL thread to apply all events, then stop it too.

SHOW SLAVE STATUS\G
STOP SLAVE SQL_THREAD;

This puts both of the …

On a busy server, the binary logs can end up being one of the largest contributors to amount of disk space used. That means higher I/O, larger backups (you are backing up your binary logs, right?), potentially more network traffic when replicas fetch the logs, and so on. In general, binary logs compress well, so it has been a long time wish for a feature that allowed you to compress the logs while MySQL are still using them. Starting from MySQL 8.0.20 that is now possible. I will take a look at the new feature in this post.

Configuration

The binary log compression feature is controlled by two variables, one for enabling the feature and another to specify the compression level. These are summarized in the below table.

Use MySQL Enterprise Audut plugin to track data changes on specific tables. Scripts and documentation on github: https://github.com/wwwted/Database-change-tracking Tracked data (audit logs) can then be inserted into reporting db using parser scripts. Limitations:

• Changing tracking rules stopps all tracking for existing connections until the reconnect. This is a limitation in MySQL EE Audit filter handling.
• No filtering for different users, easy to implement if needed in change_tracking.sql SP (START/STOP).
• Only tracking INSERT/UPDATE/DELETE statements. Easy to modify if needed.

1 Enable tracking on target server …

In this day and age, large enterprise companies make use of Ansible, Puppet, or Chef to provision MySQL servers, be it replica sets or clusters. This eases the burden of deployment and workflow management.

However, for some smaller companies, the learning curve hampers the immediate adoption of automation software. This is where the MySQL Shell helps, by allowing you to deploy an N-node InnoDB Cluster or ReplicaSet in less than 60 lines of code.

The Requirements

• Percona Server for MySQL version 8.0.17 or later, preferable version 8.0.19, each node started as standalone servers
• Percona MySQL Shell 8.0 or equivalent upstream version
• MySQL root user and password or equivalent user with grant option
• Hostname configured on each node, can be done with …

Since the beta of Galera Cluster 4 with MySQL 8 has been released, we’ve had people asking questions as to how to install it on Ubuntu 18.04. This blog post will cover just that.

Prerequisites

• All 3 nodes need to have Ubuntu 18.04 installed
• Firewall (if setup) needs to accept connections on 3306, 4444, 4567, 4568 (a default setup has the firewall disabled)
• AppArmor disabled (this is as simple as executing: systemctl stop apparmor and systemctl disable apparmor).

Installation and Configuration

We have good installation documentation as well as a quick how to get this installed in AWS (though this is CentOS centric).

First, you will need to ensure that the …

Update: Percona XtraBackup 8.0.12 now supports backup and restore processing for versions of MySQL 8.x; previous versions of Percona XtraBackup will not work with MySQL 8.0.20 and higher. More information

On Monday, April 27, 2020, Oracle released the highly anticipated 8.0.20 version of the MySQL database server. This release contains changes to the InnoDB redo log format which breaks compatibility with all currently released versions of the Percona XtraBackup 8.x series.

At this time, there are no known workarounds that will allow any version of Percona XtraBackup 8.x to function properly with MySQL 8.0.20.

We have identified the specific cause of the issue and diligently working towards a new release that will safely solve this issue as soon as possible.

Thank you for your …

As you know, today, MySQL 8.0.20 has been released. I started this new thread category with 8.0.19 (see this post).

A late thanks to Guoji Ma, for a contribution to bug #95801 “show create table output can’t be executed” that was used as inspiration for the actual fix that was pushed in MySQL 8.0.18.

MySQL 8.0.20, includes contributions from Daniel Black, Cai Yibo, Jericho Rivera, Matti Sillanpää, Nick Pollett, Bruce Feng, Kamil Holubicky, Facebook.

Thank you all for your great contributions. MySQL is an Open Source project, GPL, and we accept contribution of course. Sometimes it’s also good to remind it

Here is the list of the contributions above:

• Impossible WHERE for a!=a, a<a, …