MySQL 8.0 GA: Quality or Not?

MySQL 8.0 GA

MySQL 8.0 GAWhat does Anton Ego – a fictional restaurant critic from the Pixar movie Ratatouille – have to do with MySQL 8.0 GA?

When it comes to being a software critic, a lot.

In many ways, the work of a software critic is easy. We risk very little and thrive on negative criticism, which is fun to read and write.

But what about those who give their many hours of code development, and those who have tested such code before release? How about the many people behind the scenes who brought together packaging, documentation, multiple hours of design, marketing, online resources and more?

And all of that, I might add, is open source! Free for the world to take, copy, adapt and even incorporate in full or in part into their own open development.

It is in exactly that area that the team at MySQL shines once again – they have from their humble beginnings build up a colossally powerful database software that handles much of the world’s data, fast.

Used in every area of life – aerospace, defense, education, finances, government, healthcare, pharma, manufacturing, media, retail, telecoms, hospitality, and finally the web – it truly is a community effort.

My little contribution to this effort is first and foremost to say: well done! Well done for such an all-in-all huge endeavor. When I tested MySQL 8.0, I experienced something new: an extraordinarily clean bug report screen when I unleashed our bug hunting rats, ahem, I mean tools. This was somewhat unexpected. Usually, new releases are a fun playground even for seasoned QA engineers who look for the latest toy to break.

I have a suspicion that the team at Oracle either uses newly-improved bug-finding tools or perhaps they included some of our methods and tools in their setup. In either case, it is, was and will be welcome.

When the unexpected occurs, a fight or flight syndrome happens. I tend to be a fighter, so I upped the battle and managed to find about 30 bugs, with 21 bugs logged already. Quite a few of them are Sig 11’s in release builds. Signal 11 exceptions are unexpected crashes, and release builds are the exact same build you would download at dev.mysql.com.

The debug build also had a number of issues, but less than expected, leading me to the conclusions drawn above. Since Oracle engineers marked many of the issues logged as security bugs, I didn’t list them here. I’ll give Oracle some time to fix them, but I might add them later.

In summary, my personal recommendation is this: unless you are a funky new web company thriving on the latest technology, give Oracle the opportunity to make a few small point bugfix releases before adapting MySQL 8.0 GA. After that, providing upgrade prerequisites are matched, and that your software application is compatible, go for it and upgrade.

Before that, this is a great time to start checking out the latest and greatest that MySQL 8.0 GA has to offer!

All in all, I like what I saw, and I expect MySQL 8.0 GA to have a bright future.

Signed, a seasoned software critic.

The post MySQL 8.0 GA: Quality or Not? appeared first on Percona Database Performance Blog.


ProxySQL Admin Configuration

ProxySQL Admin

ProxySQL AdminProxySQL Admin (proxysql-admin) is a powerful tool for configuring Percona XtraDB Cluster nodes into ProxySQL. You can install the proxysql-admin package using your OS packaging manager.

ProxySQL 1.3.2-1 is now available from the Percona repositories. This release is based on ProxySQL v1.3.2a and introduces the following new changes: proxysql-admin_v1.3.2a.md.

Installing on Red Hat or CentOS

If you are running an RPM-based Linux distribution, use the yum package manager to install proxysql-admin from the official Percona software repository.

First, if your system does not already have the Percona’s yum repository configured, please run the following command:

$ sudo yum install http://www.percona.com/downloads/percona-release/redhat/0.1-4/percona-release-0.1-4.noarch.rpm

Next, install the proxysql/proxysql-admin package:

$ sudo yum install proxysql

Installing on Debian or Ubuntu

If you are running a DEB-based Linux distribution, use the apt package manager to install proxysql-admin from the official Percona software repository.

First, if your system does not already have the Percona’s apt repository configured, please fetch the repository package:

$ wget https://repo.percona.com/apt/percona-release_0.1-4.$(lsb_release -sc)_all.deb

Next, install the repository package:

$ sudo dpkg -i percona-release_0.1-4.$(lsb_release -sc)_all.deb

Then update the local apt cache:

$ sudo apt-get update

Finally, install the proxysql/proxysql-admin package:

$ sudo apt-get install proxysql


  • ProxySQL and Percona XtraDB Cluster should be up and running.
  • For security purposes, please make sure to change the default user settings in the ProxySQL configuration file. It is recommend you use –config-file to run the proxysql-admin script.

This script will accept two different options to configure Percona XtraDB Cluster nodes;

1) ??enable

This option configures Percona XtraDB Cluster nodes into the ProxySQL database, and add two cluster monitoring scripts into the ProxySQL scheduler table for checking the cluster status.

_scheduler script info:

  • proxysql_node_monitor: checks cluster node membership, and re-configures ProxySQL if cluster membership changes occur
  • proxysql_galera_checker: checks desynced nodes, and temporarily deactivates them. It will also add two new users into the Percona XtraDB Cluster with the USAGE privilege. One monitors cluster nodes through ProxySQL, and the other connects to Cluster node via the ProxySQL console. Please make sure to use super user credentials from Percona XtraDB Cluster to setup the default users.
$ sudo proxysql-admin --config-file=/etc/proxysql-admin.cnf --enable
This script will assist with configuring ProxySQL (currently only Percona XtraDB cluster in combination with ProxySQL is supported)
ProxySQL read/write configuration mode is singlewrite
Configuring ProxySQL monitoring user..
ProxySQL monitor username as per command line/config-file is monitor
User 'monitor'@'127.%' has been added with USAGE privilege
Configuring the Percona XtraDB Cluster application user to connect through ProxySQL
Percona XtraDB Cluster application username as per command line/config-file is proxysql_user
Percona XtraDB Cluster application user 'proxysql_user'@'127.%' has been added with the USAGE privilege, please make sure to the grant appropriate privileges
Adding the Percona XtraDB Cluster server nodes to ProxySQL
You have not given the writer node info through the command line or in the config-file. Please enter the writer-node info (eg :
ProxySQL configuration completed!
ProxySQL has been successfully configured to use with Percona XtraDB Cluster
You can use the following login credentials to connect your application through ProxySQL
mysql --user=proxysql_user --password=***** --host= --port=6033 --protocol=tcp
mysql> select hostgroup_id,hostname,port,status,comment from mysql_servers;
| hostgroup_id | hostname  | port  | status | comment |
| 11           | | 25400 | ONLINE | READ    |
| 10           | | 25000 | ONLINE | WRITE   |
| 11           | | 25100 | ONLINE | READ    |
| 11           | | 25200 | ONLINE | READ    |
| 11           | | 25300 | ONLINE | READ    |
5 rows in set (0.00 sec)

2. ??disable

This option removes Percona XtraDB Cluster nodes from ProxySQL and stops the ProxySQL monitoring daemon.

$ proxysql-admin --config-file=/etc/proxysql-admin.cnf --disable
ProxySQL configuration removed!

Extra options

i) ??mode

This option sets up read/write mode for Percona XtraDB Cluster nodes in the ProxySQL database, based on the hostgroup. For now, the only supported modes are loadbal and singlewrite. singlewrite is the default mode, and it accepts writes only on one single node (and this node can be provided either interactively or by using the –write-node to specify the hostname and the port number for the one single write node). All other remaining nodes will be read-only and accept only read statements. The mode loadbal, on the other hand, is a load balanced set of evenly weighted read/write nodes.

singlewrite mode setup:

$ sudo grep "MODE" /etc/proxysql-admin.cnf
export MODE="singlewrite"
$ sudo proxysql-admin --config-file=/etc/proxysql-admin.cnf --write-node= --enable
ProxySQL read/write configuration mode is singlewrite
ProxySQL configuration completed!
mysql> select hostgroup_id,hostname,port,status,comment from mysql_servers;
| hostgroup_id | hostname  | port  | status | comment |
| 11           | | 25400 | ONLINE | READ    |
| 10           | | 25000 | ONLINE | WRITE   |
| 11           | | 25100 | ONLINE | READ    |
| 11           | | 25200 | ONLINE | READ    |
| 11           | | 25300 | ONLINE | READ    |
5 rows in set (0.00 sec)

loadbal mode setup:

$ sudo proxysql-admin --config-file=/etc/proxysql-admin.cnf --mode=loadbal --enable
This script will assist with configuring ProxySQL (currently only Percona XtraDB cluster in combination with ProxySQL is supported)
ProxySQL read/write configuration mode is loadbal
ProxySQL has been successfully configured to use with Percona XtraDB Cluster
You can use the following login credentials to connect your application through ProxySQL
mysql --user=proxysql_user --password=***** --host= --port=6033 --protocol=tcp
mysql> select hostgroup_id,hostname,port,status,comment from mysql_servers;
| hostgroup_id | hostname  | port  | status | comment   |
| 10           | | 25400 | ONLINE | READWRITE |
| 10           | | 25000 | ONLINE | READWRITE |
| 10           | | 25100 | ONLINE | READWRITE |
| 10           | | 25200 | ONLINE | READWRITE |
| 10           | | 25300 | ONLINE | READWRITE |
5 rows in set (0.01 sec)

ii) ??node-check-interval

This option configures the interval for monitoring via the proxysql_galera_checker script (in milliseconds):

$ proxysql-admin --config-file=/etc/proxysql-admin.cnf --node-check-interval=5000 --enable

iii) ??adduser

This option aids with adding the Percona XtraDB Cluster application user to the ProxySQL database:

$ proxysql-admin --config-file=/etc/proxysql-admin.cnf --adduser
Adding Percona XtraDB Cluster application user to ProxySQL database
Enter Percona XtraDB Cluster application user name: root
Enter Percona XtraDB Cluster application user password:
Added Percona XtraDB Cluster application user to ProxySQL database!

iv) ??test-run

This option sets up a test/dummy proxysql configuration:

$ sudo proxysql-admin --enable --quick-demo
You have selected the dry test run mode. WARNING: This will create a test user (with all privileges) in the Percona XtraDB Cluster & ProxySQL installations.
You may want to delete this user after you complete your testing!
Would you like to proceed with '--quick-demo' [y/n] ? y
Setting up proxysql test configuration!
Do you want to use the default ProxySQL credentials (admin:admin:6032: [y/n] ? y
Do you want to use the default Percona XtraDB Cluster credentials (root::3306: [y/n] ? n
Enter the Percona XtraDB Cluster username (super user): root
Enter the Percona XtraDB Cluster user password:
Enter the Percona XtraDB Cluster port: 25100
Enter the Percona XtraDB Cluster hostname: localhost
ProxySQL read/write configuration mode is singlewrite
Configuring ProxySQL monitoring user..
User 'monitor'@'127.%' has been added with USAGE privilege
Configuring the Percona XtraDB Cluster application user to connect through ProxySQL
Percona XtraDB Cluster application user 'pxc_test_user'@'127.%' has been added with ALL privileges, this user is created for testing purposes
Adding the Percona XtraDB Cluster server nodes to ProxySQL
ProxySQL configuration completed!
ProxySQL has been successfully configured to use with Percona XtraDB Cluster
You can use the following login credentials to connect your application through ProxySQL
mysql --user=pxc_test_user --host= --port=6033 --protocol=tcp
mysql> select hostgroup_id,hostname,port,status,comment from mysql_servers;
| hostgroup_id | hostname  | port  | status | comment |
| 11           | | 25300 | ONLINE | READ    |
| 10           | | 25000 | ONLINE | WRITE   |
| 11           | | 25100 | ONLINE | READ    |
| 11           | | 25200 | ONLINE | READ    |
4 rows in set (0.00 sec)

We hope you enjoy ProxySQL Admin!


MySQL 8.0.1: The Next Development Milestone

MySQL 8.0.1

MySQL 8.0.1This post discusses the next MySQL development milestone: MySQL 8.0.1.

From the outset, MySQL 8.0 has received plenty of attention. Both this blog (see the MySQL 8.0 search) and other sites around the Internet have covered it. Early reviews seem positive (including my own MySQL 8.0 early bugs review). There is plenty of excitement about the new features.

As for early feedback on MySQL 8.0, Peter Zaitsev (Percona CEO) listed a set of recommendations for benchmarking MySQL 8.0. I hope these get reviewed and implemented.

MySQL achieved the current development milestone (available for download on dev.mysql.com) on September 12, 2016. Its release immediately came with a detailed review by Geir Hoydalsvik from MySQL. If you haven’t had the opportunity to do so yet, you can also review the MySQL 8.0 release notes.

It now looks like we’re nearing 8.0.1, the next development milestone. I don’t have insider information, but it’s quite clear when navigating mysql.com that:

Regarding timing, it’s interesting to note that the “What Is New in MySQL 8.0” page was updated on the 6th of January.

It looks like the release might come soon. So, restrain your excitement for a few days (or weeks?) more. Maybe you’ll be able to checkout the all new MySQL 8.0.1!

PS: If MySQL quality interests you, have a look at this recent – and very interesting – change made to the MTR (MySQL Test Run, the MySQL test suite) program. I believe it improves quality for everyone who runs MySQL (including its forks). The tests (which are run worldwide, often for each code change made) will now test the product with its own defaults.


Percona Monitoring and Management (PMM) Information Script

Percona Monitoring and Management

Percona Monitoring and ManagementThis blog post discusses an information script for the Percona Monitoring and Management (PMM) tool.

In recent news, we announced the fresh-of-the-press Percona Monitoring and Management (or PMM for short) platform. Given the interaction of the different components that together make up PMM, I developed a script that helps provide you information about the status of your PMM installation.

You can use this script yourself, or one of our support might point you to this page to obtain the information they need to troubleshoot an issue you are experiencing.

You will likely want to execute this script once on the PMM server (i.e., the server on which you installed the docker image), and once on the client (i.e., where you installed the PMM client rpm/apt package), if they are not the same (virtual) machine. It provides a different output for each. When sending this information back to us, please ensure to identify which output belongs to which machine (either the server or the client).

To get/run the script, use (please note that this script requires



wget https://raw.githubusercontent.com/Percona-QA/percona-qa/master/pmm-info.sh && sh ./pmm-info.sh

If you would like to examine the script contents before executing it, you can split the command:

wget https://raw.githubusercontent.com/Percona-QA/percona-qa/master/pmm-info.sh
vi pmm-info.sh
sh ./pmm-info.sh

If you have both the PMM server and the PMM client on a single machine, the output looks similar to the following:

[roel@localhost ~]$ wget https://raw.githubusercontent.com/Percona-QA/percona-qa/master/pmm-info.sh && sh ./pmm-info.sh
--2016-11-01 09:49:22-- https://raw.githubusercontent.com/Percona-QA/percona-qa/master/pmm-info.sh
Resolving raw.githubusercontent.com (raw.githubusercontent.com)...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)||:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1451 (1.4K) [text/plain]
Saving to: ‘pmm-info.sh’
100%[=========================================================================================================================================>] 1,451 --.-K/s in 0s
2016-11-01 09:49:23 (218 MB/s) - ‘pmm-info.sh’ saved [1451/1451]
QA PMM Info Script v0.07
==================== uname -a
  Linux localhost.localdomain 3.10.0-123.13.2.el7.x86_64 #1 SMP Thu Dec 18 14:09:13 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
==================== /proc/version
  Linux version 3.10.0-123.13.2.el7.x86_64 (builder@kbuilder.dev.centos.org) (gcc version 4.8.2 20140120 (Red Hat 4.8.2-16) (GCC) ) #1 SMP Thu Dec 18 14:09:13 UTC 2014
==================== OS Release (filtered cat /etc/*-release):
  CentOS Linux release 7.2.1511 (Core)
  ID_LIKE="rhel fedora"
  NAME="CentOS Linux"
  PRETTY_NAME="CentOS Linux 7 (Core)"
  VERSION="7 (Core)"
==================== Docker release (docker --version):
  Docker version 1.10.3, build cb079f6-unsupported
==================== SELinux status if present (sestatus):
  SELinux status: enabled
  SELinuxfs mount: /sys/fs/selinux
  SELinux root directory: /etc/selinux
  Loaded policy name: targeted
  Current mode: enforcing
  Mode from config file: enforcing
  Policy MLS status: enabled
  Policy deny_unknown status: allowed
  Max kernel policy version: 28
==================== PMM server images (sudo docker images | grep pmm):
  docker.io/percona/pmm-server 1.0.5 0eade99a1612 2 weeks ago 652.9 MB
  docker.io/percona/pmm-server 1.0.4 1c83d650105e 6 weeks ago 677.3 MB
  docker.io/percona/pmm-server 1.0.4-dev20160908.24845ea 4406c13d0ba3 7 weeks ago 676 MB
==================== PMM server state (sudo docker ps -a | grep pmm):
  fdf5e6adca7e percona/pmm-server:1.0.4 "/opt/entrypoint.sh" 5 days ago Exited (137) 5 days ago pmm-server3
  843a2ee31c96 percona/pmm-server:1.0.4 "/opt/entrypoint.sh" 5 days ago Created pmm-server2
  f075314b529f percona/pmm-server:1.0.4 "/bin/true" 5 days ago Created pmm-data2
  2090c072b56a percona/pmm-server:1.0.5 "/opt/entrypoint.sh" 6 days ago Up 7 minutes>80/tcp, 443/tcp pmm-server
  653fb58ce723 percona/pmm-server:1.0.5 "/bin/true" 6 days ago Created pmm-data
==================== Exporter status (ps -ef | grep exporter):
  root 2748 1 0 09:44 ? 00:00:00 /bin/sh -c /usr/local/percona/pmm-client/node_exporter -web.listen-address= -collectors.enabled=diskstats,filesystem,loadavg,meminfo,netdev,netstat,stat,time,uname,vmstat >> /var/log/pmm-linux-metrics-42000.log 2>&1
  root 2749 1 0 09:44 ? 00:00:00 /bin/sh -c /usr/local/percona/pmm-client/mysqld_exporter -collect.auto_increment.columns=true -collect.binlog_size=true -collect.global_status=true -collect.global_variables=true -collect.info_schema.innodb_metrics=true -collect.info_schema.processlist=true -collect.info_schema.query_response_time=true -collect.info_schema.tables=true -collect.info_schema.tablestats=true -collect.info_schema.userstats=true -collect.perf_schema.eventswaits=true -collect.perf_schema.file_events=true -collect.perf_schema.indexiowaits=true -collect.perf_schema.tableiowaits=true -collect.perf_schema.tablelocks=true -collect.slave_status=true -web.listen-address= >> /var/log/pmm-mysql-metrics-42002.log 2>&1
  root 2750 2748 1 09:44 ? 00:00:37 /usr/local/percona/pmm-client/node_exporter -web.listen-address= -collectors.enabled=diskstats,filesystem,loadavg,meminfo,netdev,netstat,stat,time,uname,vmstat
  root 2751 2749 0 09:44 ? 00:00:05 /usr/local/percona/pmm-client/mysqld_exporter -collect.auto_increment.columns=true -collect.binlog_size=true -collect.global_status=true -collect.global_variables=true -collect.info_schema.innodb_metrics=true -collect.info_schema.processlist=true -collect.info_schema.query_response_time=true -collect.info_schema.tables=true -collect.info_schema.tablestats=true -collect.info_schema.userstats=true -collect.perf_schema.eventswaits=true -collect.perf_schema.file_events=true -collect.perf_schema.indexiowaits=true -collect.perf_schema.tableiowaits=true -collect.perf_schema.tablelocks=true -collect.slave_status=true -web.listen-address=
  roel 4445 4392 0 10:24 pts/0 00:00:00 grep exporter
==================== PMM agent (sudo pmm-admin --version):
==================== PMM info (sudo pmm-admin info):
  pmm-admin 1.0.5
  PMM Server |
  Client Name | localhost.localdomain
  Client Address |
  Service manager | linux-systemd
==================== PMM network check (sudo pmm-admin check-network):
  PMM Network Status
  Server |
  Client |
  * Client --> Server
  --------------- -------
  --------------- -------
  Consul API OK
  Prometheus API OK
  Connection duration | 102.017µs
  Request duration | 211.962µs
  Full round trip | 313.979µs
  * Client <-- Server
  -------------- ----- ---------------------- -------
  -------------- ----- ---------------------- -------
  linux:metrics test OK
  mysql:metrics test OK
==================== PMM list (sudo pmm-admin list):
  pmm-admin 1.0.5
  PMM Server |
  Client Name | localhost.localdomain
  Client Address |
  Service manager | linux-systemd
  -------------- ----- ------------ -------- --------------------------------------------------------------------------------------------- ------------------------
  -------------- ----- ------------ -------- --------------------------------------------------------------------------------------------- ------------------------
  linux:metrics test 42000 YES -
  mysql:queries test 42001 YES root:***@unix(/sda/COMP8-PS131016-percona-server-5.6.33-78.0-linux-x86_64-debug/socket.sock) query_source=perfschema
  mysql:metrics test 42002 YES root:***@unix(/sda/COMP8-PS131016-percona-server-5.6.33-78.0-linux-x86_64-debug/socket.sock)

Support might also ask you to run the extended version of the script. This produces a lot of output, and it easier to sent the output to a log file:

wget https://raw.githubusercontent.com/Percona-QA/percona-qa/master/pmm-info.sh && sh ./pmm-info.sh ext > pmm-server.log  # Please execute this on the PMM server, and sent us pmm-server.log
wget https://raw.githubusercontent.com/Percona-QA/percona-qa/master/pmm-info.sh && sh ./pmm-info.sh > pmm-client.log      # Please execute this on the PMM client, and sent us pmm-client.log


7 Fresh Bugs in MySQL 8.0

bugs in mysql 8.0

bugs in mysql 8.0This blog post will look at seven bugs in MySQL 8.0.

Friday afternoon is always ideal for a quick look at the early quality of MySQL 8.0! Last Friday, I did just that.

If you haven’t heard the news yet, MySQL 8.0 DMR is available for download on mysql.com!

Tools to the ready: pquery2, updated 8.0 compatible scripts in Percona-qa and some advanced regex to wade through the many cores generated by the test run. For those of you who know and use pquery-run.sh, this should mean a lot!

[09:41:50] [21492] ====== TRIAL #39308 ======

In other words, almost 40K trials and 21.5K core dumps (or other significant issues) detected! This run had been churning away on a server for a number of days. On to the bug logging fun!

After reducing test cases, and filtering duplicates, we have the following seven bugs logged in upstream;

  • Bug #83120 virtual void Field::store_timestamp(const timeval*): Assertion ‘false’ failed.
  • Bug #83118 handle_fatal_signal (sig=11) in replace_user_table
  • Bug #83117 Assertion MDL_checker::is_read_locked(m_thd, *object)’ failed.
  • Bug #83115 Assertion ‘maybe_null’ failed. handle_fatal_signal in tem_func_concat::val_str
  • Bug #83114 Assertion `strlen(db_name) <= (64*3) && strlen(table_name) <= (64*3)’ failed.
  • Bug #83113 SIGKILL myself on DROP TABLE
  • Bug #83112 handle_fatal_signal (sig=11) in sp_get_flags_for_command

My first impressions?

MySQL 8.0 DMR is a reasonably solid release for a first iteration.

It seems our friends at upstream are on an excellent path to making MySQL 8.0 another rock-solid release. Chapeau!


Regular Expressions Tutorial

regular expressions

regular expressionsThis blog post highlights a video on how to use regular expressions.

It’s been a while since I did the MySQL QA and Bash Training Series. The 13 episodes were quite enjoyable to make, and a lot of people watched the video’s and provided great feedback.

In today’s new video, I’d like to briefly go over regular expressions. The session will cover the basics of regular expressions, and then some. I’ll follow up later with a more advanced regex session too.

Regular expressions are very versatile, and once you know how to use them – especially as a script developer or software coder – you will return to them again and again. Enjoy!

Presented by Roel Van de Paar. Full-screen viewing @ 720p resolution recommended



MySQL 8.0


MySQL 8.0

If you haven’t heard the news yet, MySQL 8.0 is apparently the next release of the world-famous database server.

Obviously abandoning plans to name the next release 5.8, Percona Server’s upstream provider relabelled all 5.8-related bugs to 8.0 as follows:

Reported version value updated to reflect release name change from 5.8 to 8.0

What will MySQL 8.0 bring to the world?

While lossless RBR has been suggested by Simon Mudd (for example), the actual feature list (except a Boost 1.60.0 upgrade!) remains a secret.

As far as bug and feature requests go, a smart google query revealed which bugs are likely to be fixed in (or are feature requests for) MySQL 8.0.

Here is the full list:

  • MySQL Bug #79380: Upgrade to Boost 1.60.0
  • MySQL Bug #79037: get rid of dynamic_array in st_mysql_options
  • MySQL Bug #80793: EXTEND EXPLAIN to cover ALTER TABLE
  • MySQL Bug #79812: JSON_ARRAY and JSON_OBJECT return …
  • MySQL Bug #79666: fix errors reported by ubsan
  • MySQL Bug #79463: Improve P_S configuration behaviour
  • MySQL Bug #79939: default_password_lifetime &gt; 0 should print …
  • MySQL Bug #79330: DROP TABLESPACE fails for missing general …
  • MySQL Bug #80772: Excessive memory used in memory/innodb …
  • MySQL Bug #80481: Accesses to new data-dictionary add confusing …
  • MySQL Bug #77712: mysql_real_query does not report an error for …
  • MySQL Bug #79813: Boolean values are returned inconsistently with …
  • MySQL Bug #79073: Optimizer hint to disallow full scan
  • MySQL Bug #77732: REGRESSION: replication fails for insufficient …
  • MySQL Bug #79076: make hostname a dynamic variable
  • MySQL Bug #78978: Add microseconds support to UNIX_TIMESTAMP
  • MySQL Bug #77600: Bump major version of libmysqlclient in 8.0
  • MySQL Bug #79182: main.help_verbose failing on freebsd
  • MySQL Bug #80627: incorrect function referenced in spatial error …
  • MySQL Bug #80372: Built-in mysql functions are case sensitive …
  • MySQL Bug #79150: InnoDB: Remove runtime checks for 32-bit file …
  • MySQL Bug #76918: Unhelpful error for mysql_ssl_rsa_setup when …
  • MySQL Bug #80523: current_memory in sys.session can go negative!
  • MySQL Bug #78210: SHUTDOWN command should have an option …
  • MySQL Bug #80823: sys should have a mdl session oriented view
  • MySQL Bug #78374: “CREATE USER IF NOT EXISTS” reports an error
  • MySQL Bug #79522: can mysqldump print the fully qualified table …
  • MySQL Bug #78457: Use gettext and .po(t) files for translations
  • MySQL Bug #78593: mysqlpump creates incorrect ALTER TABLE …
  • MySQL Bug #78041: GROUP_CONCAT() truncation should be an …
  • MySQL Bug #76927: Duplicate UK values in READ-COMMITTED …
  • MySQL Bug #77997: Automatic mysql_upgrade
  • MySQL Bug #78495: Table mysql.gtid_executed cannot be opened.
  • MySQL Bug #78698: Simple delete query causes InnoDB: Failing …
  • MySQL Bug #76392: Assume that index_id is unique within a …
  • MySQL Bug #76671: InnoDB: Assertion failure in thread 19 in file …
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MySQL 5.7 By Default 1/3rd Slower Than 5.6 When Using Binary Logs

binary logs make MySQL 5.7 slower

binary logs make MySQL 5.7 slower

Researching a performance issue, we came to a startling discovery:

MySQL 5.7 + binlogs is by default 37-45% slower than MySQL 5.6 + binlogs when otherwise using the default MySQL settings

Test server MySQL versions used:
i7, 8 threads, SSD, Centos 7.2.1511

mysqld –options:

--no-defaults --log-bin=mysql-bin --server-id=2

Run details:
Sysbench version 0.5, 4 threads, socket file connection

Sysbench Prepare: 

sysbench --test=/usr/share/doc/sysbench/tests/db/parallel_prepare.lua --oltp-auto-inc=off --mysql-engine-trx=yes --mysql-table-engine=innodb --oltp_table_size=1000000 --oltp_tables_count=1 --mysql-db=test --mysql-user=root --db-driver=mysql --mysql-socket=/path_to_socket_file/your_socket_file.sock prepare

Sysbench Run:

sysbench --report-interval=10 --oltp-auto-inc=off --max-time=50 --max-requests=0 --mysql-engine-trx=yes --test=/usr/share/doc/sysbench/tests/db/oltp.lua --init-rng=on --oltp_index_updates=10 --oltp_non_index_updates=10 --oltp_distinct_ranges=15 --oltp_order_ranges=15 --oltp_tables_count=1 --num-threads=4 --oltp_table_size=1000000 --mysql-db=test --mysql-user=root --db-driver=mysql --mysql-socket=/path_to_socket_file/your_socket_file.sock run


5.6.30: transactions: 7483 (149.60 per sec.)
5.7.12: transactions: 4689 (93.71 per sec.)  — That is a 37.36% decrease!

Note: on high-end systems with premium IO (think Fusion-IO, memory-only, high-end SSD with good caching throughput), the difference would be much smaller or negligible.

The reason?

A helpful comment from Shane Bester on a related bug report made me realize what was happening. Note the following in the MySQL Manual:

“Prior to MySQL 5.7.7, the default value of sync_binlog was 0, which configures no synchronizing to disk—in this case, the server relies on the operating system to flush the binary log’s contents from time to time as for any other file. MySQL 5.7.7 and later use a default value of 1, which is the safest choice, but as noted above can impact performance.” — https://dev.mysql.com/doc/refman/5.7/en/replication-options-binary-log.html#sysvar_sync_binlog

The culprit is thus the


 change which was made in 5.7.7 (in 5.6 it is 0 by default). While this may indeed be “the safest choice,” one has to wonder why Oracle chose to implement this default change in 5.7.7. After all, there are many other options t aid crash safety.

A related blog post  from the MySQL HA team states;

“Indeed, [with sync_binlog=1,] it increases the total number of fsyncs called, but since MySQL 5.6, the server groups transactions and fsync’s them together, which minimizes greatly a potential performance hit.” — http://mysqlhighavailability.com/replication-defaults-in-mysql-5-7-7/ (ref item #4)

This seems incorrect given our findings, unless perhaps it requires tuning some other option.

This raises some actions points/questions for Oracle’s team: why change this now? Was 5.6 never crash-safe in terms of binary logging? How about other options that aid crash safety? Is anything [before 5.7.7] really ACID compliant by default?

In 2009 my colleague Peter Zaitsev had already posted on performance matters in connection with sync_binlog issues. More than seven years later, the questions asked in his post may still be valid today;

“May be opening binlog with O_DSYNC flag if sync_binlog=1 instead of using fsync will help? Or may be binlog pre-allocation would be good solution.” — PZ

Testing the same setup again, but this time with




  synchronized/setup on both servers, we see;

Results for sync_binlog=0:

5.6.30: transactions: 7472 (149.38 per sec.)
5.7.12: transactions: 6594 (131.86 per sec.)  — A 11.73% decrease

Results for sync_binlog=1:

5.6.30: transactions: 3854 (77.03 per sec.)
5.7.12: transactions: 4597 (91.89 per sec.)  — A 19.29% increase

Note: the increase here is to some extent negated by the fact that enabling sync_binlog is overall still causes a significant (30% on 5.7 and 48% on 5.6) performance drop. Also interesting is that this could be the effect of “tuning the defaults” of/in 5.7, and it also makes one think about the possibility o further defaults tuning/optimization in this area.

Results for sync_binlog=100:

5.6.30: transactions: 7564 (151.12 per sec.)
5.7.12: transactions: 6515 (130.22 per sec.) — A 13.83% decrease

Thus, while 5.7.12 made some improvements when it comes to


, when


 is turned off or is set to 100, we still see a ~11% decrease in performance. This is the same when not using binary logging at all, as a test with only


  (i.e. 100% vanilla out-of-the-box MySQL 5.6.30 versus MySQL 5.7.12) shows;

Results without binlogs enabled:

5.6.30: transactions: 7891 (157.77 per sec.)
5.7.12: transactions: 6963 (139.22 per sec.)  — A 11.76% decrease

This raises another question for Oracle’s team: with four threads, there is a ~11% decrease in performance for 5.7.12 versus 5.6.30 (both vanilla)?

Discussing this internally, we were interested to see whether the arbitrary low number of four threads skewed the results and perhaps only showed a less realistic use case. However, testing with more threads, the numbers became worse still:

Results with 100 threads:

5.6.30. transactions: 20216 (398.89 per sec.)
5.7.12. transactions: 11097 (218.43 per sec.) — A 45.24% decrease

Results with 150 threads:

5.6.30. transactions: 11852 (233.01 per sec.)
5.7.12. transactions: 6606 (129.80 per sec.) — A 44.29% decrease

The findings in this article were compiled from a group effort.


MySQL is crashing: a support engineer’s point of view

In MySQL QA Episode #12, “MySQL is Crashing, now what?,” Roel demonstrated how to collect crash-related information that will help Percona discover what the issue is that you are experiencing, and fix it.

As a Support Engineer I (Sveta) am very happy to see this post – but as a person who better understands writing than recording – I’d like to have same information, in textual form. We discussed it, and decided to do a joint blog post. Hence, this post :)

If you haven’t seen the video yet, or you do not have any experience with gdb, core files and crashes, I highly recommend to watch it first.

Once you have an idea of why crashes happen, what to do after it happens in your environment, and how to open a Support issue and/or a bug report, you’re ready for the next step: which information do you need to provide? Note that the more complete and comprehensive information you provide, the quicker the evaluation and potential fix process will go – it’s a win-win situation!

At first we need the MySQL error log file. If possible, please send us the full error log file. Often users like to send only the part which they think is relevant, but the error log file can contain other information, recorded before the crash happened. For example, records about table corruptions, lack of disk space, issues with InnoDB dictionary, etc.

If your error log is quite large, please note it would compress very well using a standard compression tool like gzip. If for some reason you cannot send the full error log file, please sent all lines, written after the words “mysqld: ready for connections” (as seen the last time before the actual crash), until the end of the error log file (alternatively, you can also search for rows, started with word “Version:”). Or, if you use scripts (or mysqld_safe) which automatically restart MySQL Server in case of disaster, obviously please search for the one-previous server start after the crash.

An example which includes an automatic restart as mentioned above:

2015-08-03 14:24:03 9911 [Note] /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld: ready for connections.
Version: '5.6.25-73.1-log'  socket: '/tmp/mysql_sandbox21690.sock'  port: 21690  Percona Server (GPL), Release 73.1, Revision 07b797f
2015-08-03 14:24:25 7f5b193f9700 InnoDB: Buffer pool(s) load completed at 150803 14:24:25
11:25:12 UTC - mysqld got signal 4 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.
Please help us make Percona Server better by reporting any
bugs at http://bugs.percona.com/
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 348059 K  bytes of memory
Hope that's ok; if not, decrease some variables in the equation.
Thread pointer: 0x0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0 thread_stack 0x40000
You may download the Percona Server operations manual by visiting
http://www.percona.com/software/percona-server/. You may find information
in the manual which will help you identify the cause of the crash.
150803 14:25:12 mysqld_safe Number of processes running now: 0
150803 14:25:12 mysqld_safe mysqld restarted
/home/sveta/SharedData/Downloads/5.6.25/bin/mysqld: /lib64/libssl.so.1.0.0: no version information available (required by /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld)
/home/sveta/SharedData/Downloads/5.6.25/bin/mysqld: /lib64/libcrypto.so.1.0.0: no version information available (required by /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld)
2015-08-03 14:25:12 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2015-08-03 14:25:12 0 [Note] /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld (mysqld 5.6.25-73.1-log) starting as process 10038 ...
2015-08-03 14:25:12 10038 [Warning] Buffered warning: Changed limits: max_open_files: 1024 (requested 50005)
2015-08-03 14:25:12 10038 [Warning] Buffered warning: Changed limits: max_connections: 214 (requested 10000)
2015-08-03 14:25:12 10038 [Warning] Buffered warning: Changed limits: table_open_cache: 400 (requested 4096)
2015-08-03 14:25:12 10038 [Note] Plugin 'FEDERATED' is disabled.
2015-08-03 14:25:12 10038 [Note] InnoDB: Using atomics to ref count buffer pool pages
2015-08-03 14:25:12 10038 [Note] InnoDB: The InnoDB memory heap is disabled
2015-08-03 14:25:12 10038 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2015-08-03 14:25:12 10038 [Note] InnoDB: Memory barrier is not used
2015-08-03 14:25:12 10038 [Note] InnoDB: Compressed tables use zlib 1.2.3
2015-08-03 14:25:12 10038 [Note] InnoDB: Using Linux native AIO
2015-08-03 14:25:12 10038 [Note] InnoDB: Using CPU crc32 instructions
2015-08-03 14:25:12 10038 [Note] InnoDB: Initializing buffer pool, size = 4.0G
2015-08-03 14:25:13 10038 [Note] InnoDB: Completed initialization of buffer pool
2015-08-03 14:25:13 10038 [Note] InnoDB: Highest supported file format is Barracuda.
2015-08-03 14:25:13 10038 [Note] InnoDB: The log sequence numbers 514865622 and 514865622 in ibdata files do not match the log sequence number 514865742 in the ib_logfiles!
2015-08-03 14:25:13 10038 [Note] InnoDB: Database was not shutdown normally!
2015-08-03 14:25:13 10038 [Note] InnoDB: Starting crash recovery.
2015-08-03 14:25:13 10038 [Note] InnoDB: Reading tablespace information from the .ibd files...
2015-08-03 14:25:14 10038 [Note] InnoDB: Restoring possible half-written data pages
2015-08-03 14:25:14 10038 [Note] InnoDB: from the doublewrite buffer...
InnoDB: Last MySQL binlog file position 0 150866, file name mysql-bin.000006
2015-08-03 14:25:16 10038 [Note] InnoDB: 128 rollback segment(s) are active.
2015-08-03 14:25:16 10038 [Note] InnoDB: Waiting for purge to start
2015-08-03 14:25:16 10038 [Note] InnoDB:  Percona XtraDB (http://www.percona.com) 5.6.25-rel73.1 started; log sequence number 514865742
2015-08-03 14:25:16 7f67ceff9700 InnoDB: Loading buffer pool(s) from .//ib_buffer_pool
2015-08-03 14:25:16 10038 [Note] Recovering after a crash using mysql-bin
2015-08-03 14:25:16 10038 [Note] Starting crash recovery...
2015-08-03 14:25:16 10038 [Note] Crash recovery finished.
2015-08-03 14:25:17 10038 [Note] RSA private key file not found: /home/sveta/sandboxes/rsandbox_Percona-Server-5_6_25/master/data//private_key.pem. Some authentication plugins will not work.
2015-08-03 14:25:17 10038 [Note] RSA public key file not found: /home/sveta/sandboxes/rsandbox_Percona-Server-5_6_25/master/data//public_key.pem. Some authentication plugins will not work.
2015-08-03 14:25:17 10038 [Note] Server hostname (bind-address): ''; port: 21690
2015-08-03 14:25:17 10038 [Note]   - '' resolves to '';
2015-08-03 14:25:17 10038 [Note] Server socket created on IP: ''.
2015-08-03 14:25:17 10038 [Warning] 'proxies_priv' entry '@ root@thinkie' ignored in --skip-name-resolve mode.
2015-08-03 14:25:17 10038 [Note] Event Scheduler: Loaded 0 events
2015-08-03 14:25:17 10038 [Note] /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld: ready for connections.
Version: '5.6.25-73.1-log'  socket: '/tmp/mysql_sandbox21690.sock'  port: 21690  Percona Server (GPL), Release 73.1, Revision 07b797f

Usually the error log file contains the actual query which caused the crash. If it does not and you know the query (for example, if your application logs errors / query problems), please send us this query too. Additionally, if possible, include the CREATE TABLE statements for any tables mentioned in the query. Actually working with the query is the first thing which you can do to resolve the issue: try to run this query (on a non-production/test server which is as close a copy to your production server as possible), to ensure it crashes MySQL Server consistently. If so, you can try and create a temporary workaround by avoiding this kind of queries in your application.

If you have doubts as to which query caused the crash, but have the general query log turned ON, you can use utility


  from percona-qa to create a potential test case. Simply execute:

$ sudo yum install bzr
$ cd ~
$ bzr branch lp:percona-qa
$ cp /path_that_contains_your_general_log/your_log_file.sql ~
$ ~/percona-qa/parse_general_log.pl -i./your_log_file.sql -o./output.sql

And subsequently execute output.sql against mysqld on a non-production test server to see if a crash is produced. Alternatively, you may mail us the output.sql file (provided your company privacy etc. policies allow for this). If you want to try and reduce the testcase further, please see QA Episode #7 on reducing testcases.

The next thing which we need is a backtrace. You usually have a simple backtrace showing in the error log directly after crash. An example (extracted from an error log) of what this looks like:

stack_bottom = 0 thread_stack 0x40000

Note that the above backtrace is mangled. You can send us the file like this (we can demangle it). However, if you want to work with it yourself more comfortably you can unmangle it with help of



sveta@linux-85fm:~/sandboxes/rsandbox_Percona-Server-5_6_25> cat master/data/msandbox.err | c++filt
terribly wrong...
stack_bottom = 0 thread_stack 0x40000
/home/sveta/SharedData/Downloads/5.6.25/bin/mysqld(mysqld_main(int, char**)+0x1b5d)[0x5fd87d]

Now the backtrace looks much nicer. When sending error log reports to us, please to not use 


 on them before sending. We have a list of known bugs, and to scan the known bugs list we need to receive the error log unaltered.

You can also turn core files ON. Core files are memory dump files, created when a process crashes. They are very helpful for debugging, because they contain not only the backtrace of crashing thread, but backtraces of all threads, and much of what was in memory at the time the crash occurred.

Sidenote: Please note it is always a good idea to have the debuginfo (for example Percona-Server-56-debuginfo.x86_64 from the Percona Repository) package installed. This package provides the debugging symbols for Percona server (there are similar packages for other distributions) and ensures that stack traces are more readable and contain more information. It is important to ensure that you have the right package version etc. as symbols are different for each version of mysqld. If you have installed Percona Server from our repository, you can simply install the debuginfo package, the version will be correct, and the package will be auto-updated when Percona Server is updated.

By default the MySQL server does not create core files. To let it do so, you can follow instructions from the “GDB Cheat sheet” (page 2 under header ‘Core Files Cheat Sheet’). In short:

  • Add the option core-file under the [mysqld] section of your configuration file
  • Tune your OS options, so it allows mysqld to create core files as described in the cheat sheet
    echo "core.%p.%e.%s" > /proc/sys/kernel/core_pattern
    ulimit -c unlimited
    sudo sysctl -w fs.suid_dumpable=2

    Note: some systems use ‘kernel’ instead of ‘fs’: use kernel.suid_dumpable=2 instead if you get key or file warnings/errors.
  • Restart the MySQL server

Besides the core file which is generated by the MySQL server, you can also setup the operating system to dump a core file. These are two different core files (for a single crash of the mysqld binary), and the amount of information contained within may differ. The procedure above shows how to setup the one for the MySQL Server alone.

If you like your operating system to dump a core file as well, please see the MySQL QA Episode #12 video. Also, please note that changing the ulimit and fs.suid_dumpable settings may alter the security of your system. Please read more about these options online before using them or leaving them permanently on a production system.

Once a core file is generated, you can use the GDB utility to debug the core file (also called a ‘coredump’). GDB allows you to better resolve backtraces (also called ‘stack traces’ or ‘stacks’), for example by taking a back trace of all threads instead of only the crashing threads. This is off-course better then the single backtrace available in the error log file. To use GDB, you need to first start it:

gdb /path_to_mysqld /path_to_core

/path_to_core is usually your data directory (for coredumps produced by mysqld as a result of using the –core-file option in your my.cnf file), or sometimes in the same directory where the crashing binary is (for coredumps produced by the OS) – though you can specify an alternate fixed location for OS coredumps as the cheat sheet. Note that OS generated dumps are sometimes written with very few privileges and so you may have to use chown/chmod/sudo to access it.

Once you’re into GDB, and all looks fine, run the commands


(backtrace) and  

bt thread apply all

(get backtrace for all threads) to get the stacktraces. bt should more or less match the backtrace seen in the error log, but sometimes this may differ.

For us, ideally you would run the following commands in GDB (as seen in the cheat sheet):

set trace-commands on
set pagination off
set print pretty on
set print array on
set print array-indexes on
set print elements 4096
set logging file gdb_standard.txt
set logging on
thread apply all bt
set logging off
set logging file gdb_full.txt
set logging on
thread apply all bt full

After you run these commands and have existed ( quit ) GDB, please send us the 





Finally, we would be happy to receive the actual core file from you. In terms of security and privacy, please note that a core file often contains fragments, or sections, or even the full memory of your server.

However, a core file without mysqld is useless, thus please add the mysqld binary together with the core file. If you use our compiled binaries you can also specify the exact package and file name which you downloaded, but if you use a self-compiled version of the server, the mysqld binary is required for us to resolve backtrace and other necessary information (like varialbes) from your core file. Generally speaking, it’s easier just to sent mysqld along.

Also, it would be really nice, if you send us library files which are dynamically linked with mysqld you use. You can get them by using a tool, called


  from the percona-qa suite. Just create a temporary directory, copy your


  binary to it and run the tool on it:

sveta@thinkie:~/tmp> wget http://bazaar.launchpad.net/~percona-core/percona-qa/trunk/download/head:/ldd_files.sh-20150713030145-8xdk0llrd3skfsan-1/ldd_files.sh
sveta@thinkie:~/tmp> mkdir tmp
sveta@thinkie:~/tmp> cd tmp/
sveta@thinkie:~/tmp/tmp> cp /home/sveta/SharedData/Downloads/5.6.25/bin/mysqld . # Copy of your mysqld
sveta@thinkie:~/tmp/tmp> ../ldd_files.sh mysqld # Run the tool on it
cp: cannot stat ‘./mysqld: /lib64/libssl.so.1.0.0: no version information available’: No such file or directory # Ignore
cp: cannot stat ‘./mysqld: /lib64/libcrypto.so.1.0.0: no version information available’: No such file or directory # Ignore
sveta@thinkie:~/tmp/tmp> ls
ld-linux-x86-64.so.2 libaio.so.1 libcrypto.so.1.0.0 libcrypt.so.1 libc.so.6 libdl.so.2 libgcc_s.so.1 libm.so.6 libpthread.so.0 librt.so.1 libssl.so.1.0.0 libstdc++.so.6 libz.so.1 mysqld # Files to supply in combination with mysqld

These library files are needed if case some of the frames from the stacktrace are system calls, so that our developers can resolve/check those frames also.


If you hit a crash, please send us (in order of preference, but even better ‘all of these’):

  • The error log file (please sent it unaltered – i.e. before c++filt was executed – which allows us to scan for known bugs)
  • The crashing query (from your application logs and/or extracted from the core file – ref the query extraction blog post)
    • Please include the matching CREATE TABLE statements
  • A resolved backtrace (and/or preferably the ./gdb_standard.txt and ./gdb_full.txt files)
  • The core file together with the mysqld binary and preferably the ldd files

Thank you!


The post MySQL is crashing: a support engineer’s point of view appeared first on MySQL Performance Blog.


MySQL Quality Assurance: A Vision for the Future by Roel Van de Paar (Final Episode 13)

Welcome to the final – but most important – episode in the MySQL QA Series.

In it, I present my vision for all MySQL Quality Assurance – for all distributions – worldwide.

Episode 13: A Better Approach to all MySQL Regression, Stress & Feature Testing: Random Coverage Testing & SQL Interleaving

1. pquery Review
2. Random Coverage Testing
3. SQL Interleaving
4. The past & the future

Presented by Roel Van de Paar. Full-screen viewing @ 720p resolution recommended

Interested in the full MySQL QA Series?

The post MySQL Quality Assurance: A Vision for the Future by Roel Van de Paar (Final Episode 13) appeared first on MySQL Performance Blog.

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