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MySQL 8.0 Data Dictionary Tables… and why they should stay protected

With MySQL 8.0, one key feature is the new Data Dictionary. The system tables that were previously in MyISAM are now replaced by new protected ones in the DD. My friend Giuseppe already explained how you could see those tables using sandbox  and he also warned you that you should not mess up with them in this post too. I’ll … Read More


Where does my MySQL configuration variable value come from ?

As you may already know, there are many different places where a MySQL configuration variables can be initialized. In MySQL 8.0, we added in performance_schema a table allowing you to easily find where a variable was defined. Let’s check this in action with max_connections for example. I started mysqld and now I check the value of max_connections: mysql> show global … Read More


MySQL Clients and emojis !

As you probably already know, MySQL 8.0 supports Unicode 9.0 and our default charset moved from latin1 to utf8mb4. Recently, Gabi (certainly working on an amazing presentation for PHPWorld) asked me something about how the client deals with the emojis while checking Morgo’s post about 8.0 RC1. I didn’t know the answer and had to play with it, here is … Read More


MySQL InnoDB Cluster: how to handle performance issue on one member ?

  Sometimes when you are using a MySQL InnoDB Cluster, you might encounter some performance issue because one node becomes dramatically slow. Why ? First of all, why ? A node can apply the transactions slower than the other nodes for many different reasons. The most frequents are for example, slower disks (remember, it’s advised to have nodes with the … Read More


MySQL 8.0 Atomic DDL – behavior change

In MySQL 8.0, we have now a new way of storing tables definitions: the Data Dictionary  ! Thanks to the Data Dictionary, DDLs in MySQL 8.0 are now Atomic. This means tat we have some changes in the behavior of the following DDLs for engines supporting  atomic DDL: DROP TABLES <tables> – All tables will be dropped, or none are … Read More


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