In this blog post, we’ll discuss how the Query Rewrite plugin can harm performance.

MySQL 5.7 comes with Query Rewrite plugin, which allows you to modify queries coming to the server. (You can view the details here: https://dev.mysql.com/doc/refman/5.7/en/rewriter-query-rewrite-plugin.html.)

It is based on the audit plugin API, and unfortunately it suffers from serious scalability issues (which seems to be the case for all API-based audit plugins).

I want to share the results for sysbench OLTP RO with and without the query rewrite plugin — but with one very simple rewrite rule, which doesn’t affect any queries. This is the rule from the documentation:

INSERT INTO query_rewrite.rewrite_rules (pattern, replacement)
    -> VALUES('SELECT ?', 'SELECT ? + 1');

There are results for both …

The MariaDB project is pleased to announce the immediate availability of MariaDB 10.1.14, and MariaDB Connector/J 1.4.4. See the release notes and changelogs for details on these releases. Download MariaDB 10.1.14 Release Notes Changelog What is MariaDB 10.1? MariaDB APT and YUM Repository Configuration Generator Download MariaDB Connector/J 1.4.4 Release Notes Changelog About MariaDB Connector/J […]

The post MariaDB 10.1.14 and Connector/J 1.4.4 now available appeared first on MariaDB.org.

In this blog post, we’ll discuss the ins and outs of Percona Server 5.7 parallel doublewrite.

After implementing parallel LRU flushing as described in the previous post, we went back to benchmarking. At first, we tested with the doublewrite buffer turned off. We wanted to isolate the effect of the parallel LRU flusher, and the results validated the design. Then we turned the doublewrite buffer back on and saw very little, if any, gain from the parallel LRU flusher. What happened? Let’s take a look at the data:

We see that the doublewrite buffer mutex is gone as expected and that the top waiters are the rseg mutexes and the index lock (shouldn’t this be fixed in 5.7?). Then we checked PMP:

2678 nanosleep(libpthread.so.0),...,buf_LRU_get_free_block(buf0lru.cc:1435),...
867 pthread_cond_wait,...,log_write_up_to(log0log.cc:1293),...
396 …

In this blog, we’ll examine how CPU governor performance affects MySQL.

It’s been a while since we looked into CPU governors and with the new Intel CPUs and new Linux distros, I wanted to check how CPU governors affect MySQL performance.

Before jumping to results, let’s review what drivers manage CPU frequency. Traditionally, the default driver was “acpi-cpufreq”, but for the recent Intel CPUs and new Linux kernel it was changed to “intel_pstate”.

To check what driver is being used, run the command

cpupower frequency-info

 .

cpupower frequency-info
analyzing CPU 0:
driver: acpi-cpufreq
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: 10.0 us.
hardware limits: 1.20 GHz - 2.00 GHz
available frequency steps: 2.00 GHz, 2.00 GHz, 1.90 GHz, 1.80 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.40 GHz, …

Lossless RBR TL/DR: There’s been talk of moving the next release of MySQL to minimal RBR: I’d like to suggest an alternative: lossless RBR For MySQL 5.8 there was talk / suggestions about moving to minimal RBR as the default configuration (http://mysqlserverteam.com/planning-the-defaults-for-mysql-5-8/).  I’m not comfortable with this because it means that by default you do not have … Continue reading Lossless RBR for MySQL 8.0?

The post Lossless RBR for MySQL 8.0? first appeared on Simon J Mudd's Blog.

I’m happy to be back in London in May 2016, to talk at two events:

1. The London MySQL Meetup Group – Monday May 9 – 6.30 PM – 9.00 PM – options for High Availability in the ecosystem that one would consider today. This is a cut down from my Percona Live tutorial, which had about 88 registered attendees and about that amount showed up and asked questions even through the break and after. I had a lot of fun, and I expect I will have similar fun in London talking about this area that has changed a lot in recent times.
2. Data for the Enterprise – MariaDB Roadshow in London – Wednesday, May 11, 2016 from 9:30 AM to 2:00 …

Who are the top individual authors of influential recent posts to planet MySQL?  The planet MySQL page includes a list of the top 20 authors as well as a list of the top 10 vendor blogs.  However, since posts to the vendor blogs make up at least 1/4 of all of the posts, and the authors of vendor blog posts are not included in the top author list, I decided to compute my own top author list.  I include the hidden authors from the vendor blogs when computing my top author list.

The first problem is to identify the hidden authors for posts from each vendor blog.  This requires that the author information be extracted from the individual posts, and this requires a specialized parser for each vendor blog to extract the author name from the document.
The second problem is to rank the authors using some criteria such as the number of posts in a given recent time range.   I could run a page rank algorithm if I …

Since documentation is not very clear to me on the topic of InnoDB flushing in combination with Linux IO (specifically the write system call), I decided to put together this article in hopes of shedding some light on the matter.

How Linux does I/O

By default, the write() system call returns after all data has been copied from the user space file descriptor into the kernel space buffers. There is no guarantee that data has actually reached the physical storage.

The fsync() call is our friend here. This will block and return only after the data and metadata (e.g. file size, last update time) is completely transferred to the actual physical storage.

There is also fdatasync() which only guarantees the data …

Recently the mysql community got an awesome monitoring solution for mysql

with Prometheus & Grafana. The graphs are simply beautiful and really lively.

I started off with this nice post on the mysql performance blog  by Roman Vynar and got the solution up and running very easily.

You can actually monitor Amazon RDS instance with the same steps mentioned in the above post but with a few changes:

The monitoring framework consists of 4 components:

1. Prometheus server on port 9090
2. Grafana server on port 3000
3. MySQL …

What is MetaData Lock?

MySQL uses metadata locking to manage concurrent access to database objects, and to ensure data consistency when performing modifications to the schema: DDL operations. Metadata locking applies not just to tables, but also to schemas and stored programs (procedures, functions, triggers, and scheduled events).

In this post I am going to cover metadata locks on tables and triggers, that are usually seen by DBAs during regular operations/maintenance.

Kindly refer to these 4 different connections to MySQL Instance:

The screenshot shows that the uncommitted transaction may cause metadata lock to ALTER operations. The ALTER will not proceed until the transaction is committed or rolled-back. What is worse, after the ALTER is issued, any queries to that table (even simple SELECT queries) will be blocked. If the ALTER operation is an …