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Displaying posts with tag: performance_schema (reset)
MySQL sys version 1.0.1 released

I’ve just released the 1.0.1 version of the MySQL sys schema. It contains a few bug fixes (including a contribution from Joe Grasse, thanks Joe!), and a number of new helper procedures around viewing and altering configuration for consumers and instruments, contributed by the MySQL QA team, as they’ve started to incorporate more Performance Schema trace data in to their automated testing.

Next up is the 1.1.0 release, that also includes a bunch of new host summary views that were contributed by Arnaud Adant (of the MySQL Support team). I have a number of new things in development to add as well before then though.

Let me know if there are things you’d like to see as well, maybe I can find time to work on those too.


Performance_schema success stories : host summary tables

This question was asked at support by a customer to solve a difficult issue.

How to identify a sporadic burst of queries coming from one of the hosts accessing the database ?

If there are hundreds of hosts, it can be challenging, especially if the queries are fast. No chance for them to get logged in the famous slow query log !

Here is the solution using the performance_schema in MySQL 5.6 :

SUM(essbben.count_star) AS total_statements,
format_time(SUM(essbben.sum_timer_wait)) AS total_latency,
format_time(SUM(essbben.sum_timer_wait) / SUM(count_star))
AS avg_latency
performance_schema.events_statements_summary_by_host_by_event_name essbben
SUM(sum_timer_wait) DESC;

Here is the result :

| host          | total_statements | total_latency | avg_latency | …
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Fun with Bugs #30 - quick review of my reports in February, 2014

I've got only one comment to my previous post about deadlock, and it was more like a hint based on a different use case, not a real explanation. So far there is nobody who wants to get free beer... Maybe this is even good, as I do not go to the conference and BOF I've submitted will be supervised by my colleague Przemysław Malkowski. But you still have entire month till the conference to get a chance for a beer from him (we'll arrange this somehow).

In the meantime I'd like to review bug reports for MySQL server (few) and fine manual (many) that I've submitted in February, 2014. 22 in total, one was just plain wrong and I closed it as "Not a bug" almost immediately. So, 21 to …

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A couple of weeks ago, shortly after Vadim wrote about Percona Cloud Tools and using Slow Query Log to capture the data, Mark Leith asked why don’t we just use Performance Schema instead? This is an interesting question and I think it deserves its own blog post to talk about.

First, I would say main reason for using Slow Query Log is compatibility. Basic Slow query log with microsecond query time precision is available starting in MySQL 5.1, while events_statements_summary_by_digest table was only added in MySQL 5.6 which was out for …

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MySQL 5.6 GA one year – What is next?

MySQL 5.6 has been GA for just over a year now. See MySQL 5.6.10 Release Notes.  Congratulations on your birthday! That is quite a long time. I was using it earlier in production because it worked and could do things that 5.5 could not do, but earlier versions were to use at your own risk, and indeed if prodded incorrectly would fall on the floor. That is fair enough because they were work in progress, yet if you poked them the right way they did a very good job.  Those dev versions have been long since upgraded which is good so they do not need quite as much care and attention.

So from where I see 5.6 it works very well. One big change that has made a large difference but which I think a lot of people may not really understand or use is the …

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Exploring MySQL Metadata Lock Instrumentation in Closer Detail

I recently wrote a post on tracking metadata locks (MDL) in MySQL 5.7, and I wanted to take a moment to expand on it by explaining a couple of the associated variables in more detail.

First off, once you have enabled the performance_schema *and* the metadata lock instrumentation, you can verify it with:

mysql> SELECT * FROM performance_schema.setup_instruments
    -> WHERE NAME = 'wait/lock/metadata/sql/mdl';
| NAME                       | ENABLED | TIMED |
| wait/lock/metadata/sql/mdl | YES     | YES   |

“ENABLED” will report “YES” if it is enabled properly, and “NO” if not.

“TIMED” (referring to event timing) reports “YES” if it was enabled via the my.cnf or my.ini file, and it …

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Tracking Metadata Locks (MDL) in MariaDB 10.0

I recently blogged about tracking metadata locks in the latest MySQL, and now I want to discuss how to track these metadata locks in MariaDB.

In MySQL 5.7, there is a table named `metadata_locks` added to the performance_schema (performance_schema must be enabled *and* the metadata_locks instrument must be specifically enabled as well.

In the MariaDB 10.0 implementation (as of 10.0.7), there is a table named METADATA_LOCK_INFO added to the *information_schema*. This is a new plugin, so the plugin must be installed, but that is very simple with:

INSTALL SONAME 'metadata_lock_info';

Then, you will have the table.

To see it in action:

Connection #1:

mysql> create table t (id int) engine=myisam;
mysql> begin;
mysql> select * from t;

Connection #2:

mysql> alter table t add …
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Tracking Metadata Locks (MDL) in MySQL 5.7

I’ve blogged about metadata locks (MDL) in the past (1 2 3) and in particular discussed how best to track them down and troubleshoot threads stuck waiting on metadata locks.

If you’ve had any experience with these, you’ll know finding them isn’t always the most straight-forward task.

So I was glad to see metadata lock instrumentation added to MySQL 5.7.3 as part of performance_schema, which makes tracking these down a breeze! (Note this is only in 5.7.3 currently, and therefore is some time from being GA as of today)!

To use these, performance_schema must be enabled (i.e., performance_schema=1 in your config file).

But, also, the metadata_locks instrument is disabled by default, so even if you enable the …

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SF MySQL Meetup Presentation: Changes in MySQL 5.7

Last Wednesday, I spoke at the San Francisco MySQL Meetup on the topic of changes coming in MySQL 5.7 (and later).  We actually went through two different slide decks; the first on features being considered for deprecation in MySQL 5.7 (or later), and the second set providing a brief overview of the new features and benefits already introduced in MySQL 5.7 via the development milestone releases (DMRs) published to date.  A big thanks to the entire SF Meetup group, and in particular the organizers (Erin, Mike and Darren), for having me.  The event was streamed and recorded, and you can view the full presentation on YouTube.  The slide deck can be found here.

The discussion around proposed deprecation was good, and this blog serves to document my own notes about what …

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Fun with Bugs #26 - MySQL bugs Oracle had not fixed for me (yet)

In the previous post in this series I've listed 15 MySQL bug reports, documentation and feature requests I've made in 2013 that got fixes or any other kind of solution. Now it's time to check what happened to the rest and try to think why.

First of all, no MySQL bug reporter is perfect (if only Domas), so some bug reports may be false alarms ("Not a bug"), to hard to fix at any foreseeable future ("To be fixed later") or asking for something that Oracle does not plan to provide …

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