During the MySQL 5.8 Dreaming and brainstorming session at PerconaLive, someone voiced a wish for an “option to make temporary tables created by the optimizer always go to disk”. By default, MySQL creates in-memory temporary tables in the MEMORY engine. The maximum size for in-memory temporary tables is the minimum of the tmp_table_size and max_heap_table_size.…

Investigation run by Marco Tusa

CONCLUSIONS

MySQL/Galera was able to outperform Aurora in all tests — by execution time, number of transactions, and volumes of rows managed. Also, scaling up the Aurora instance did not have the impact I was expecting. Actually it was still not able to match the EC2 MySQL/Galera performance, with less memory and CPUs.

In light of the tests, the recommendations consider different factors to answer the question, “Which is the best tool for the job?” If HA and very low failover time are the major factors, MySQL with Galera is the right choice”.

READ THE FULL STORY AND INVESTIGATION

In a previous post, we discussed the error log as a source of diagnostic information for MySQL. We’ve shown examples of problems where the error log can help you diagnose issues with MySQL. This post focuses on the Galera Cluster error logs, so if you are currently using Galera, read on.

In a Galera cluster, whether you use MariaDB Cluster, Percona XtraDB Cluster or the Codership build, the MySQL error log is even more important. It gives you the same information as MySQL would, but you’ll also find in it information about Galera internals and replication. This data is crucial to understand the state of your cluster and to identify any issues which may impact the cluster’s ability to operate. In this post, we’ll try to make the Galera error log easier to understand.

This is the sixteenth installment in …

In a previous post, we discussed the error log as a source of diagnostic information for MySQL. We’ve shown examples of problems where the error log can help you diagnose issues with MySQL. This post focuses on the Galera Cluster error logs, so if you are currently using Galera, read on.

In a Galera cluster, whether you use MariaDB Cluster, Percona XtraDB Cluster or the Codership build, the MySQL error log is even more important. It gives you the same information as MySQL would, but you’ll also find in it information about Galera internals and replication. This data is crucial to understand the state of your cluster and to identify any issues which may impact the cluster’s ability to operate. In this post, we’ll try to make the Galera error log easier to understand.

This is the sixteenth installment in …

How to interpret Raw data from Windows performance counters.
Tip: An alias for Get-CimInstance is GCim and alias for Get-WmiObject is GWmi.

In the first blog post, I covered what WMI/CIM is and how to get info from there. Last I talked about was RawData counters:
Get-CimInstance -Class Win32_PerfRawData_PerfOS_Processor

Name : _Total
...
PercentIdleTime : 78061457390


Understanding RawData:By itself, a RawData value is a sample but important thing is to determine what concrete sample value actually is and how to convert it to a form we understand. In this example, MSDN tells us PercentIdleTime is a counter of type 542180608:
…

Edit1: With updates in SQLyog 12.1.9 and 12.2.0, SQLyog is now fully safe with Virtual Columns of both MariaDB and MySQL 5.7 (all SQLyog backup-, copy- and sync-tools).

Edit2: There are still problems with mysqldump as of 5.7.11 – refer http://bugs.mysql.com/bug.php?id=80790. I do think it was OK in 5.7.9 so this looks like a regression introduced in 5.7.10 or 5.7.11. But  I may be wrong here. 

Virtual columns have existed in MariaDB since version 5.2 and were recently introduced in MySQL 5.7. The recent MySQL 5.7.9 GA release includes this feature.

At first look the implementations in MariaDB and Oracle/MySQL do not seem much different. If you compare documentation …

Edit1: With updates in SQLyog 12.1.9 and 12.2.0, SQLyog is now fully safe with Virtual Columns of both MariaDB and MySQL 5.7 (all SQLyog backup-, copy- and sync-tools).

Edit2: There are still problems with mysqldump as of 5.7.11 – refer http://bugs.mysql.com/bug.php?id=80790. I do think it was OK in 5.7.9 so this looks like a regression introduced in 5.7.10 or 5.7.11. But  I may be wrong here. 

Virtual columns have existed in MariaDB since version 5.2 and were recently introduced in MySQL 5.7. The recent MySQL 5.7.9 GA release includes this feature.

At first look the implementations in MariaDB and Oracle/MySQL do not seem much different. If you compare documentation …

The "innodb_read_only" parameter is perhaps not among the most commonly used MySQL parameters. It may however influence server behaviour in a way that you may not expect. This post is a record of an investigation that revealed one of MySQL quirks caused by said parameter.
Background The MySQL 5.6 server topology I was looking at during this investigation consisted of a single main server (R/W) and multiple replicas serving read-only statements.
This is relatively simple and you wouldn't expect to run into issues on the replicas as long as you stick to statements that do not modify data, right?
Not quite. Issue I was asked to investigate can be described as follows:
The DBA created two tables connected using a foreign key relationship:

CREATE TABLE `employee` (
  `e_id` int(11) NOT …

Slides from my talk during MySQL Central @OpenWorld 2015 are available from here now :
- http://dimitrik.free.fr/Presentations/MySQL_Perf-Tuning-OOW2015-dim.pdf 

they should be soon available from the OpenWorld site as well.

Rgds,
-Dimitri

This Log Buffer is dedicated to the top quality news from the arena of Oracle, SQL Server and MySQL.

Oracle:

• We had a question on AskTom the other day, asking us to explain what a “latch” was.
• Jonathan Lewis thinks column groups can be amazingly useful in helping the optimizer to generate good execution plans because of the way they supply better details about cardinality.
• Today it’s all about developing software that makes access to your product easier.
• …