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Displaying posts with tag: sys (reset)
pre-FOSDEM MySQL Day 2019

For the third year in a row, we will take advantage of the mass presence of our MySQL Engineers during FOSDEM to organize the pre-FOSDEM MySQL Day.

The program of this 3rd edition is already on track, thank you to all the speakers who already confirmed their participation.

Start End Event Speaker Company Topic
Friday 1st February
09:30 10:00 MySQL Community Team Welcome
10:00
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Fun with Bugs #74 - On MySQL Bug Reports I am Subscribed to, Part XI

For some reason the Committee of FOSDEM 2019 MySQL, MariaDB & Friends Devroom of all my talks submitted picked up the one on how to create a useful MySQL bug report, so I have no options but continue to write about MySQL bugs, as long and MySQL Community wants and even prefers to listen and read about them... That's what I do, with pleasure.

Today I'll continue my series of posts about community bug reports I am subscribed to with the review of bugs reported since October 1, 2018, starting from the oldest and skipping those MySQL 8 regression ones I've already commented on:

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MySQL Memory Consumption and Open Prepare Statements

Today I read the nice post of Bhuvanesh on the memory leak issue they experienced with MySQL. In fact when you read the post, you realize that MySQL was just following the parameters that were setup (the default of max_prepare_stmt_count is 16382 even on 5.6).

I’m still convinced that the problem should be resolved in the application even if the use of ProxySQL for multiplexing is great.

In MySQL 8.0, we have enabled the …

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MySQL and Memory: a love story (part 2)

We saw in the previous post that MySQL likes memory. We also saw how to perform operating system checks and some configuration changes for Swap and NUMA.

Today, we will check what MySQL server can tell us about its memory usage.

Introduced in MySQL 5.7 and enabled by default in MySQL 8.0, the Performance_Schema‘s Memory instrumentation allows us to have a better overview of what MySQL is allocating and why.

Let’s check on our MySQL server using SYS:

Pay attention that there is a bug related to how InnoDB Buffer Pool statistics are accounted in Performance_Schema. This is fixed in 8.0.13. …

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MySQL: size of your tables – tricks and tips

Many of you already know how to retrieve the size of your dataset, schemas and tables in MySQL.

To summarize, below are the different queries you can run:

Dataset Size

I the past I was using something like this :

But now with sys schema being installed by default, I encourage you to use some of the formatting functions provided with it. The query to calculate the dataset is now:

SELECT sys.format_bytes(sum(data_length)) DATA,
       sys.format_bytes(sum(index_length)) INDEXES,
       sys.format_bytes(sum(data_length + index_length)) 'TOTAL SIZE'
FROM information_schema.TABLES ORDER  BY data_length + index_length;

Let’s see an example:

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PS_history 2.0 was released last week with MySQL 8 support and bundled sys_history

PS_history is a tool which collects historical snapshots of the PERFORMANCE_SCHEMA (P_S). This allows you to trend P_S values over time, for example, it is possible to look at the 95 th percentile response time for a query over time.

PS_history is stored procedure and event based, and thus it resides entirely inside of the database with no external dependencies. It uses a clever technique to capture all of the P_S data in one consistent snapshot. This ensures that all of the sys_history views (bundled now with PS_history) have a consistent set of data.

By default, as long as the event_schedule is enabled, PS_history will collect data every 30 seconds. If a snapshot takes 30 seconds, there will be a 30 second delay before the next snapshot starts. This value can be changed by calling the `ps_history`.`set_collection_interval`(N) where N is the number of seconds between samples.

The `sys_history` schema is …

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PS_history 2.0 was released last week with MySQL 8 support and bundled sys_history

PS_history is a tool which collects historical snapshots of the PERFORMANCE_SCHEMA (P_S). This allows you to trend P_S values over time, for example, it is possible to look at the 95 th percentile response time for a query over time.

PS_history is stored procedure and event based, and thus it resides entirely inside of the database with no external dependencies. It uses a clever technique to capture all of the P_S data in one consistent snapshot. This ensures that all of the sys_history views (bundled now with PS_history) have a consistent set of data.

By default, as long as the event_schedule is enabled, PS_history will collect data every 30 seconds. If a snapshot takes 30 seconds, there will be a 30 second delay before the next snapshot starts. This value can be changed by calling the `ps_history`.`set_collection_interval`(N) where N is the number of seconds between samples.

The `sys_history` schema is …

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MySQL Support People - Those Who Joined Oracle to Work on MySQL

In this post I'd like to mention my colleagues from MySQL Support who had joined the team when Oracle already acquired Sun (and MySQL as a part of it), in 2010-2012. There were several really great engineers among them:

  • Jesper Krogh - with his 31 public bug reports, numerous blog posts (check also this one), ps_tools and presentations, Jesper is well known to MySQL community. He had joined Oracle as Senior MySQL Support Engineer in March, 2011 and is a Senior Principal Technical Support Engineer at Oracle now. Check one of his …
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My Guidebook for Percona Live Amsterdam, 2015 - Part I

Unfortunately I am not going to Percona Live Amsterdam 2015 that starts next week. Somebody has to work and keep those customers happy who prefer to work as usual even during such a festival.

I am still asking myself: if I'd be able to go there, what tutorials and sessions I'd like to attend (besides those I'd present)? "All of them" is not a correct answer, as often great and useful sessions happens at the same time in different places. So, I decided to create a list of sessions for myself (as a reminder to check slides at least after they are published), and I'd like to share it.

I tried to pick up one session …

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When your query is blocked, but there is no blocking query

When I queried information_schema.innodb_trx (introduced in 5.1 with the InnoDB Plugin) I noticed there were a few transactions in LOCK WAIT state.

Example:

mysql [information_schema] > select trx_id,trx_state 
    -> from information_schema.innodb_trx;
+--------+-----------+
| trx_id | trx_state |
+--------+-----------+
| 7974 | LOCK WAIT |
| 7962 | RUNNING |
+--------+-----------+
2 rows in set (0.00 sec)


Then I made a query to join a few information_schema and performance_schema tables to find out which query was blocking my transactions. It turned out that the blocking transaction had a trx_query=NONE. So my query was block by a transaction doing nothing. That's not really helpful.

Let's try to recreate the situation and see exactly what happened. I'll use two sessions for the transactions and a third to monitor the …

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