The latest from the MySQL community

In this blog post, I’ll discuss some of the MySQL and MariaDB default configuration differences, focusing on MySQL 5.7 and MariaDB 10.2. Percona Server for MySQL uses the same defaults as MySQL, so I will not list them separately.

MariaDB Server is a general purpose open source database, created by the founders of MySQL. MariaDB Server (referred to as MariaDB for brevity) has similar roots as Percona Server for MySQL, but is quickly diverging from MySQL compatibility and growing on its own. MariaDB has become the default installation for several operating systems (such as Red Hat Enterprise Linux/CentOS/Fedora). Changes in the default variables can make a large difference in the out-of-box …

In my previous blog post, I talked about new general tablespaces in MySQL 8.0. Recently MySQL 8.0.3-rc was released, which includes a new data dictionary. My goal is to create one million tables in MySQL and test the performance.

Background questions

Q: Why million tables in MySQL? Is it even realistic? How does this happen?

Usually, millions of tables in MySQL is a result of “a schema per customer” Software as a Service (SaaS) approach. For the purposes of customer data isolation (security) and logical data partitioning (performance), each “customer” has a dedicated schema. You can think of a WordPress hosting service (or any CMS based hosting) where each …

Notes/errata/updates for Chapter 5:
See the official book errata at http://tahaghoghi.com/LearningMySQL/errata.php – Chapter 5 is pages 135-177.

Notes:
If you did not load the sample databases in Chapter 3 as per page 102, you can download the file to import from http://tahaghoghi.com/LearningMySQL/Downloads/Files/Data/SQL_files_with_foreign_key_references/music.sql

On page 162, it says “In Chapter 6, we’ll discuss how to load data from existing tables or from external data sources.” but this content is in Chapter 8.

On page 169, it has an example of “DELETE FROM played;” which deletes all the rows of a table. This will not work if safe_updates are enabled. I always advise that if you …

Dear MySQL users,

MySQL Connector/J 8.0.8 Development Release is a development milestone
release for the 8.0.x series.

This release includes the following new features and changes, also
described in more detail on

https://dev.mysql.com/doc/relnotes/connector-j/8.0/en/news-8-0-8.html

MySQL Connectors and other MySQL client tools and applications now
synchronize the first digit of their version number with the (highest)
MySQL server version they support.
This change makes it easy and intuitive to decide which client version
to use for which server version.

As always, we recommend that you check the “CHANGES” file in the download
archive to be aware of changes in behavior that might affect your application.

To download MySQL Connector/J …

Dear MySQL users,

MySQL Connector/Net 8.0.9 is the sixth development release that expands
cross-platform support to Linux and macOS when using Microsoft’s .NET Core
framework. Now, .NET developers can use the X DevAPI with .NET Core and
Entity Framework Core (EF Core) 1.0 to create server applications that run
on Windows, Linux and macOS. We are very excited about this change and
really look forward to your feedback on it!

MySQL Connector/Net 8.0.9 is also the eighth development release of MySQL
Connector/Net to add support for the new X DevAPI.  The X DevAPI enables
application developers to write code that combines the strengths of the
relational and document models using a modern, NoSQL-like syntax that
does not assume previous experience writing traditional SQL.

To learn more about how to write applications using the X DevAPI, see
…

Continuation of my previous Blog Post for MYSQL CLOUD SERVICE 2018 [1Z0-320] exam preparation, In this blog will discuss Database Design part for MySQL. Rather than rewriting given topics I have provided already exists good reference links for few topics.

Database Design

• Describe Datatypes in a MySQL database
• Create databases and tables
• Create basic SQL queries
• Maintain Databases, Tables, and Columns
• Configure Indexes and Constraints
• Join Tables
• Partition MySQL Tables

Describe Datatypes in a MySQL database

Reference Link:

Link1: …

In this blog post, we’ll look at how to avoid shared locks from subqueries.

I’m pretty sure most of you have seen an UPDATE statement matching rows returned from a SELECT query:

update ibreg set k=1 where id in (select id from ibcmp where id > 90000);

This query, when executed with

autocommit=1

, is normally harmless. However, this can have bad effects when combined with other statements in the same transaction that result in holding the shared locks from the SELECT query. But first, let me explain why the SELECT query would hold locks in the first place.

Due to InnoDB’s ACID properties, to make sure that the outer UPDATE statement has a consistent view of the matching rows from the SELECT query the server has to acquire a shared lock on those rows. No other thread should modify …

In my previous article about roles I said that one of the problems with role usage is that roles need to be activated before they kick in. Let's recap briefly what the problem is:

## new session, as user `root`

mysql [localhost] {root} ((none)) > create role viewer;
Query OK, 0 rows affected (0.01 sec)

mysql [localhost] {root} ((none)) > grant select on *.* to viewer;
Query OK, 0 rows affected (0.01 sec)

mysql [localhost] {root} ((none)) > create user see_it_all identified by 'msandbox';
Query OK, 0 rows affected (0.01 sec)

mysql [localhost] {root} ((none)) > grant viewer to see_it_all;
Query OK, 0 rows affected (0.01 sec)

## NEW session, as user `see_it_all`

mysql [localhost] {see_it_all} ((none)) > use test
ERROR 1044 (42000): Access denied for user 'see_it_all'@'%' to database 'test'

mysql [localhost] {see_it_all} ((none)) > show grants\G …

Sync MySQL Servers with ProxySQL Cluster

In the two previous blog posts about ProxySQL Cluster we described how to setup a Cluster, how to add users/rules and propagate them across the Cluster, how to provision new nodes, how to re-sync nodes after they have been out of the Cluster, and some features in the roadmap, especially around the concept of core nodes vs satellite nodes.
We also mention that there are 4 modules/tables that currently ProxySQL Cluster is able to sync:

• mysql_query_rules
• mysql_servers
• mysql_users
• proxysql_servers

We covered 3 of these, and the last one missing is how to sync mysql_servers, related to MySQL …

In this post, we will discuss how to fix cardinality for InnoDB tables manually.

As a support engineer, I often see situations when the cardinality of a table is not correct. When InnoDB calculates the cardinality of an index, it does not scan the full table by default. Instead it looks at random pages, as determined by options innodb_stats_sample_pages, innodb_stats_transient_sample_pages and innodb_stats_persistent_sample_pages, or …