Congratulations to Oracle on MySQL 8.0

Post Syndicated from Michael "Monty" Widenius original http://monty-says.blogspot.com/2018/04/congratulations-to-oracle-on-mysql-80.html

Last week, Oracle announced the general availability of MySQL 8.0. This is good news for database users, as it means Oracle is still developing MySQL.

I decide to celebrate the event by doing a quick test of MySQL 8.0. Here follows a step-by-step description of my first experience with MySQL 8.0.
Note that I did the following without reading the release notes, as is what I have done with every MySQL / MariaDB release up to date; In this case it was not the right thing to do.

I pulled MySQL 8.0 from [email protected]:mysql/mysql-server.git
I was pleasantly surprised that ‘cmake . ; make‘ worked without without any compiler warnings! I even checked the used compiler options and noticed that MySQL was compiled with -Wall + several other warning flags. Good job MySQL team!

I did have a little trouble finding the mysqld binary as Oracle had moved it to ‘runtime_output_directory’; Unexpected, but no big thing.

Now it’s was time to install MySQL 8.0.

I did know that MySQL 8.0 has removed mysql_install_db, so I had to use the mysqld binary directly to install the default databases:
(I have specified datadir=/my/data3 in the /tmp/my.cnf file)

> cd runtime_output_directory
> mkdir /my/data3
> ./mysqld –defaults-file=/tmp/my.cnf –install

2018-04-22T12:38:18.332967Z 1 [ERROR] [MY-011011] [Server] Failed to find valid data directory.
2018-04-22T12:38:18.333109Z 0 [ERROR] [MY-010020] [Server] Data Dictionary initialization failed.
2018-04-22T12:38:18.333135Z 0 [ERROR] [MY-010119] [Server] Aborting

A quick look in mysqld –help –verbose output showed that the right command option is –-initialize. My bad, lets try again,

> ./mysqld –defaults-file=/tmp/my.cnf –initialize

2018-04-22T12:39:31.910509Z 0 [ERROR] [MY-010457] [Server] –initialize specified but the data directory has files in it. Aborting.
2018-04-22T12:39:31.910578Z 0 [ERROR] [MY-010119] [Server] Aborting

Now I used the right options, but still didn’t work.
I took a quick look around:

> ls /my/data3/
binlog.index

So even if the mysqld noticed that the data3 directory was wrong, it still wrote things into it.  This even if I didn’t have –log-binlog enabled in the my.cnf file. Strange, but easy to fix:

> rm /my/data3/binlog.index
> ./mysqld –defaults-file=/tmp/my.cnf –initialize

2018-04-22T12:40:45.633637Z 0 [ERROR] [MY-011071] [Server] unknown variable ‘max-tmp-tables=100’
2018-04-22T12:40:45.633657Z 0 [Warning] [MY-010952] [Server] The privilege system failed to initialize correctly. If you have upgraded your server, make sure you’re executing mysql_upgrade to correct the issue.
2018-04-22T12:40:45.633663Z 0 [ERROR] [MY-010119] [Server] Aborting

The warning about the privilege system confused me a bit, but I ignored it for the time being and removed from my configuration files the variables that MySQL 8.0 doesn’t support anymore. I couldn’t find a list of the removed variables anywhere so this was done with the trial and error method.

> ./mysqld –defaults-file=/tmp/my.cnf

2018-04-22T12:42:56.626583Z 0 [ERROR] [MY-010735] [Server] Can’t open the mysql.plugin table. Please run mysql_upgrade to create it.
2018-04-22T12:42:56.827685Z 0 [Warning] [MY-010015] [Repl] Gtid table is not ready to be used. Table ‘mysql.gtid_executed’ cannot be opened.
2018-04-22T12:42:56.838501Z 0 [Warning] [MY-010068] [Server] CA certificate ca.pem is self signed.
2018-04-22T12:42:56.848375Z 0 [Warning] [MY-010441] [Server] Failed to open optimizer cost constant tables
2018-04-22T12:42:56.848863Z 0 [ERROR] [MY-013129] [Server] A message intended for a client cannot be sent there as no client-session is attached. Therefore, we’re sending the information to the error-log instead: MY-001146 – Table ‘mysql.component’ doesn’t exist
2018-04-22T12:42:56.848916Z 0 [Warning] [MY-013129] [Server] A message intended for a client cannot be sent there as no client-session is attached. Therefore, we’re sending the information to the error-log instead: MY-003543 – The mysql.component table is missing or has an incorrect definition.
….
2018-04-22T12:42:56.854141Z 0 [System] [MY-010931] [Server] /home/my/mysql-8.0/runtime_output_directory/mysqld: ready for connections. Version: ‘8.0.11’ socket: ‘/tmp/mysql.sock’ port: 3306 Source distribution.

I figured out that if there is a single wrong variable in the configuration file, running mysqld –initialize will leave the database in an inconsistent state. NOT GOOD! I am happy I didn’t try this in a production system!

Time to start over from the beginning:

> rm -r /my/data3/*
> ./mysqld –defaults-file=/tmp/my.cnf –initialize

2018-04-22T12:44:45.548960Z 5 [Note] [MY-010454] [Server] A temporary password is generated for [email protected]: px)NaaSp?6um
2018-04-22T12:44:51.221751Z 0 [System] [MY-013170] [Server] /home/my/mysql-8.0/runtime_output_directory/mysqld (mysqld 8.0.11) initializing of server has completed

Success!

I wonder why the temporary password is so complex; It could easily have been something that one could easily remember without decreasing security, it’s temporary after all. No big deal, one can always paste it from the logs. (Side note: MariaDB uses socket authentication on many system and thus doesn’t need temporary installation passwords).

Now lets start the MySQL server for real to do some testing:

> ./mysqld –defaults-file=/tmp/my.cnf

2018-04-22T12:45:43.683484Z 0 [System] [MY-010931] [Server] /home/my/mysql-8.0/runtime_output_directory/mysqld: ready for connections. Version: ‘8.0.11’ socket: ‘/tmp/mysql.sock’ port: 3306 Source distribution.

And the lets start the client:

> ./client/mysql –socket=/tmp/mysql.sock –user=root –password=”px)NaaSp?6um”
ERROR 2059 (HY000): Plugin caching_sha2_password could not be loaded: /usr/local/mysql/lib/plugin/caching_sha2_password.so: cannot open shared object file: No such file or directory

Apparently MySQL 8.0 doesn’t work with old MySQL / MariaDB clients by default 🙁

I was testing this in a system with MariaDB installed, like all modern Linux system today, and didn’t want to use the MySQL clients or libraries.

I decided to try to fix this by changing the authentication to the native (original) MySQL authentication method.

> mysqld –skip-grant-tables

> ./client/mysql –socket=/tmp/mysql.sock –user=root
ERROR 1045 (28000): Access denied for user ‘root’@’localhost’ (using password: NO)

Apparently –skip-grant-tables is not good enough anymore. Let’s try again with:

> mysqld –skip-grant-tables –default_authentication_plugin=mysql_native_password

> ./client/mysql –socket=/tmp/mysql.sock –user=root mysql
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 8.0.11 Source distribution

Great, we are getting somewhere, now lets fix “root”  to work with the old authenticaion:

MySQL [mysql]> update mysql.user set plugin=”mysql_native_password”,authentication_string=password(“test”) where user=”root”;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘(“test”) where user=”root”‘ at line 1

A quick look in the MySQL 8.0 release notes told me that the PASSWORD() function is removed in 8.0. Why???? I don’t know how one in MySQL 8.0 is supposed to generate passwords compatible with old installations of MySQL. One could of course start an old MySQL or MariaDB version, execute the password() function and copy the result.

I decided to fix this the easy way and use an empty password:

(Update:: I later discovered that the right way would have been to use: FLUSH PRIVILEGES;  ALTER USER’ root’@’localhost’ identified by ‘test’  ; I however dislike this syntax as it has the password in clear text which is easy to grab and the command can’t be used to easily update the mysql.user table. One must also disable the –skip-grant mode to do use this)

MySQL [mysql]> update mysql.user set plugin=”mysql_native_password”,authentication_string=”” where user=”root”;
Query OK, 1 row affected (0.077 sec)
Rows matched: 1 Changed: 1 Warnings: 0
 
I restarted mysqld:
> mysqld –default_authentication_plugin=mysql_native_password

> ./client/mysql –user=root –password=”” mysql
ERROR 1862 (HY000): Your password has expired. To log in you must change it using a client that supports expired passwords.

Ouch, forgot that. Lets try again:

> mysqld –skip-grant-tables –default_authentication_plugin=mysql_native_password

> ./client/mysql –user=root –password=”” mysql
MySQL [mysql]> update mysql.user set password_expired=”N” where user=”root”;

Now restart and test worked:

> ./mysqld –default_authentication_plugin=mysql_native_password

>./client/mysql –user=root –password=”” mysql

Finally I had a working account that I can use to create other users!

When looking at mysqld –help –verbose again. I noticed the option:

–initialize-insecure
Create the default database and exit. Create a super user
with empty password.

I decided to check if this would have made things easier:

> rm -r /my/data3/*
> ./mysqld –defaults-file=/tmp/my.cnf –initialize-insecure

2018-04-22T13:18:06.629548Z 5 [Warning] [MY-010453] [Server] [email protected] is created with an empty password ! Please consider switching off the –initialize-insecure option.

Hm. Don’t understand the warning as–initialize-insecure is not an option that one would use more than one time and thus nothing one would ‘switch off’.

> ./mysqld –defaults-file=/tmp/my.cnf

> ./client/mysql –user=root –password=”” mysql
ERROR 2059 (HY000): Plugin caching_sha2_password could not be loaded: /usr/local/mysql/lib/plugin/caching_sha2_password.so: cannot open shared object file: No such file or directory

Back to the beginning 🙁

To get things to work with old clients, one has to initialize the database with:
> ./mysqld –defaults-file=/tmp/my.cnf –initialize-insecure –default_authentication_plugin=mysql_native_password

Now I finally had MySQL 8.0 up and running and thought I would take it up for a spin by running the “standard” MySQL/MariaDB sql-bench test suite. This was removed in MySQL 5.7, but as I happened to have MariaDB 10.3 installed, I decided to run it from there.

sql-bench is a single threaded benchmark that measures the “raw” speed for some common operations. It gives you the ‘maximum’ performance for a single query. Its different from other benchmarks that measures the maximum throughput when you have a lot of users, but sql-bench still tells you a lot about what kind of performance to expect from the database.

I tried first to be clever and create the “test” database, that I needed for sql-bench, with
> mkdir /my/data3/test

but when I tried to run the benchmark, MySQL 8.0 complained that the test database didn’t exist.

MySQL 8.0 has gone away from the original concept of MySQL where the user can easily
create directories and copy databases into the database directory. This may have serious
implication for anyone doing backup of databases and/or trying to restore a backup with normal OS commands.

I created the ‘test’ database with mysqladmin and then tried to run sql-bench:

> ./run-all-tests –user=root

The first run failed in test-ATIS:

Can’t execute command ‘create table class_of_service (class_code char(2) NOT NULL,rank tinyint(2) NOT NULL,class_description char(80) NOT NULL,PRIMARY KEY (class_code))’
Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘rank tinyint(2) NOT NULL,class_description char(80) NOT NULL,PRIMARY KEY (class_’ at line 1

This happened because ‘rank‘ is now a reserved word in MySQL 8.0. This is also reserved in ANSI SQL, but I don’t know of any other database that has failed to run test-ATIS before. I have in the past run it against Oracle, PostgreSQL, Mimer, MSSQL etc without any problems.

MariaDB also has ‘rank’ as a keyword in 10.2 and 10.3 but one can still use it as an identifier.

I fixed test-ATIS and then managed to run all tests on MySQL 8.0.

I did run the test both with MySQL 8.0 and MariaDB 10.3 with the InnoDB storage engine and by having identical values for all InnoDB variables, table-definition-cache and table-open-cache. I turned off performance schema for both databases. All test are run with a user with an empty password (to keep things comparable and because it’s was too complex to generate a password in MySQL 8.0)

The result are as follows
Results per test in seconds:

Operation         |MariaDB|MySQL-8|

———————————–
ATIS              | 153.00| 228.00|
alter-table       |  92.00| 792.00|
big-tables        | 990.00|2079.00|
connect           | 186.00| 227.00|
create            | 575.00|4465.00|
insert            |4552.00|8458.00|
select            | 333.00| 412.00|
table-elimination |1900.00|3916.00|
wisconsin         | 272.00| 590.00|
———————————–

This is of course just a first view of the performance of MySQL 8.0 in a single user environment. Some reflections about the results:

  • Alter-table test is slower (as expected) in 8.0 as some of the alter tests benefits of the instant add column in MariaDB 10.3.
  • connect test is also better for MariaDB as we put a lot of efforts to speed this up in MariaDB 10.2
  • table-elimination shows an optimization in MariaDB for the  Anchor table model, which MySQL doesn’t have.
  • CREATE and DROP TABLE is almost 8 times slower in MySQL 8.0 than in MariaDB 10.3. I assume this is the cost of ‘atomic DDL’. This may also cause performance problems for any thread using the data dictionary when another thread is creating/dropping tables.
  • When looking at the individual test results, MySQL 8.0 was slower in almost every test, in many significantly slower.
  • The only test where MySQL was faster was “update_with_key_prefix”. I checked this and noticed that there was a bug in the test and the columns was updated to it’s original value (which should be instant with any storage engine). This is an old bug that MySQL has found and fixed and that we have not been aware of in the test or in MariaDB.
  • While writing this, I noticed that MySQL 8.0 is now using utf8mb4 as the default character set instead of latin1. This may affect some of the benchmarks slightly (not much as most tests works with numbers and Oracle claims that utf8mb4 is only 20% slower than latin1), but needs to be verified.
  • Oracle claims that MySQL 8.0 is much faster on multi user benchmarks. The above test indicates that they may have done this by sacrificing single user performance.
  •  We need to do more and many different benchmarks to better understand exactly what is going on. Stay tuned!

Short summary of my first run with MySQL 8.0:

  • Using the new caching_sha2_password authentication as default for new installation is likely to cause a lot of problems for users. No old application will be able to use MySQL 8.0, installed with default options, without moving to MySQL’s client libraries. While working on this blog I saw MySQL users complain on IRC that not even MySQL Workbench can authenticate with MySQL 8.0. This is the first time in MySQL’s history where such an incompatible change has ever been done!
  • Atomic DDL is a good thing (We plan to have this in MariaDB 10.4), but it should not have such a drastic impact on performance. I am also a bit skeptical of MySQL 8.0 having just one copy of the data dictionary as if this gets corrupted you will lose all your data. (Single point of failure)
  • MySQL 8.0 has several new reserved words and has removed a lot of variables, which makes upgrades hard. Before upgrading to MySQL 8.0 one has to check all one’s databases and applications to ensure that there are no conflicts.
  • As my test above shows, if you have a single deprecated variable in your configuration files, the installation of MySQL will abort and can leave the database in inconsistent state. I did of course my tests by installing into an empty data dictionary, but one can assume that some of the problems may also happen when upgrading an old installation.

Conclusions:
In many ways, MySQL 8.0 has caught up with some earlier versions of MariaDB. For instance, in MariaDB 10.0, we introduced roles (four years ago). In MariaDB 10.1, we introduced encrypted redo/undo logs (three years ago). In MariaDB 10.2, we introduced window functions and CTEs (a year ago). However, some catch-up of MariaDB Server 10.2 features still remains for MySQL (such as check constraints, binlog compression, and log-based rollback).

MySQL 8.0 has a few new interesting features (mostly Atomic DDL and JSON TABLE functions), but at the same time MySQL has strayed away from some of the fundamental corner stone principles of MySQL:

From the start of the first version of MySQL in 1995, all development has been focused around 3 core principles:

  • Ease of use
  • Performance
  • Stability

With MySQL 8.0, Oracle has sacrifices 2 of 3 of these.

In addition (as part of ease of use), while I was working on MySQL, we did our best to ensure that the following should hold:

  • Upgrades should be trivial
  • Things should be kept compatible, if possible (don’t remove features/options/functions that are used)
  • Minimize reserved words, don’t remove server variables
  • One should be able to use normal OS commands to create and drop databases, copy and move tables around within the same system or between different systems. With 8.0 and data dictionary taking backups of specific tables will be hard, even if the server is not running.
  • mysqldump should always be usable backups and to move to new releases
  • Old clients and application should be able to use ‘any’ MySQL server version unchanged. (Some Oracle client libraries, like C++, by default only supports the new X protocol and can thus not be used with older MySQL or any MariaDB version)

We plan to add a data dictionary to MariaDB 10.4 or MariaDB 10.5, but in a way to not sacrifice any of the above principles!

The competition between MySQL and MariaDB is not just about a tactical arms race on features. It’s about design philosophy, or strategic vision, if you will.

This shows in two main ways: our respective view of the Storage Engine structure, and of the top-level direction of the roadmap.

On the Storage Engine side, MySQL is converging on InnoDB, even for clustering and partitioning. In doing so, they are abandoning the advantages of multiple ways of storing data. By contrast, MariaDB sees lots of value in the Storage Engine architecture: MariaDB Server 10.3 will see the general availability of MyRocks (for write-intensive workloads) and Spider (for scalable workloads). On top of that, we have ColumnStore for analytical workloads. One can use the CONNECT engine to join with other databases. The use of different storage engines for different workloads and different hardware is a competitive differentiator, now more than ever.

On the roadmap side, MySQL is carefully steering clear of features that close the gap between MySQL and Oracle. MariaDB has no such constraints. With MariaDB 10.3, we are introducing PL/SQL compatibility (Oracle’s stored procedures) and AS OF (built-in system versioned tables with point-in-time querying). For both of those features, MariaDB is the first Open Source database doing so. I don’t except Oracle to provide any of the above features in MySQL!

Also on the roadmap side, MySQL is not working with the ecosystem in extending the functionality. In 2017, MariaDB accepted more code contributions in one year, than MySQL has done during its entire lifetime, and the rate is increasing!

I am sure that the experience I had with testing MySQL 8.0 would have been significantly better if MySQL would have an open development model where the community could easily participate in developing and testing MySQL continuously. Most of the confusing error messages and strange behavior would have been found and fixed long before the GA release.

Before upgrading to MySQL 8.0 please read https://dev.mysql.com/doc/refman/8.0/en/upgrading-from-previous-series.html to see what problems you can run into! Don’t expect that old installations or applications will work out of the box without testing as a lot of features and options has been removed (query cache, partition of myisam tables etc)! You probably also have to revise your backup methods, especially if you want to ever restore just a few tables. (With 8.0, I don’t know how this can be easily done).

According to the MySQL 8.0 release notes, one can’t use mysqldump to copy a database to MySQL 8.0. One has to first to move to a MySQL 5.7 GA version (with mysqldump, as recommended by Oracle) and then to MySQL 8.0 with in-place update. I assume this means that all old mysqldump backups are useless for MySQL 8.0?

MySQL 8.0 seams to be a one way street to an unknown future. Up to MySQL 5.7 it has been trivial to move to MariaDB and one could always move back to MySQL with mysqldump. All MySQL client libraries has worked with MariaDB and all MariaDB client libraries has worked with MySQL. With MySQL 8.0 this has changed in the wrong direction.

As long as you are using MySQL 5.7 and below you have choices for your future, after MySQL 8.0 you have very little choice. But don’t despair, as MariaDB will always be able to load a mysqldump file and it’s very easy to upgrade your old MySQL installation to MariaDB 🙂

I wish you good luck to try MySQL 8.0 (and also the upcoming MariaDB 10.3)!