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Displaying posts with tag: performance_schema (reset)
Generating Slow Query Log with MySQL Shell

Recently, I wrote three articles on how to analyze queries and generate a slow query log for MySQL Database Service on OCI:

In these post, we were generating a slow query log in text or JSON directly in Object Storage.

Today, we will see how we can generate …

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Analyzing queries in MySQL Database Service – Slow Query Log (part 2)

In the previous part, we created our application and our 2 functions.

Now we need to create an API Gateway to be able to call these functions from outside OCI. Using a third party scheduler, our laptop, etc…

Before creating the gateway, we need to create some policy to allow the API Gateway to call our functions. I’ve tried to create the policy after, it seems to not work as expected.

Security

Dynamic Group

We need to create a Dynamic Group that will match our gateway:

The matching rule is checking the type of resource that should be ApiGateway and my compartment’s id:

All {resource.type='ApiGateway', resource.compartment.id = 'ocid1.compartment.oc1..xxxxxxxxx'}

Policy …

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Analyzing queries in MySQL Database Service – Slow Query Log (part 1)

In my previous post, I explained how to deal with Performance_Schema and Sys to identify the candidates for Query Optimization but also to understand the workload on the database.

In this article, we will see how we can create an OCI Fn Application that will generate a slow query log from our MySQL Database Service instance and store it to Object Storage.

The creation of the function and its use is similar to the one explained in the …

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Analyzing queries in MySQL Database Service

If like me you are an old experienced MySQL DBA, to analyze your MySQL workload, you certainly have used the slow query log with long_query_time set to 0.

The slow query log is a file that contains all the queries whose execution time is greater than the value of long_query_time. This file can be huge and uses up all available disk space on busy systems.

Constantly writing to that file can also add an overhead to the server.

For those reasons, the slow query log is not available in MySQL Database Service (HeatWave) in OCI.

Plan B ?

As a DBA, what are my options for finding the queries that need to be optimized? As usual, the queries that consume the most time are the ones that need some attention

It can be a very long query or a short query executed too many times.

Currently the MySQL DBAs use …

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MySQL 8.0: How to display long transactions

Recently, somebody asked me how he can find the long running transactions in MySQL.

I already have one MySQL Shell plugin that allows you to find the current transactions sorted by time. The plugin allows you to also get the details about the desired transaction. See check.getRunningStatements().

Let’s see how we can easily find those long transaction that can be a nightmare for the DBAs (see MySQL History List Length post).

SELECT thr.processlist_id AS mysql_thread_id,
       concat(PROCESSLIST_USER,'@',PROCESSLIST_HOST) User,
       Command,
       FORMAT_PICO_TIME(trx.timer_wait) AS trx_duration,
       current_statement as `latest_statement`
  FROM …
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A graph a day, keeps the doctor away ! – Full Table Scans

Full table scans can be problematic for performance. Certainly if the scanned tables are large. The worst case is when full table scans are involved in joins and particularly when the scanned table is not the first one (this was dramatic before MySQL 8.0 as Block Nested Loop was used) !

A full table scans means that MySQL was not able to use an index (no index or no filters using it).

Effects

When Full Table Scans happen (depending of the size of course), a lot of data gets pulled into the Buffer Pool and maybe other important data from the working set is pulled out. Most of the time that new data in the Buffer Pool might even not be required by the application, what a waste of resources !

You then understand that another side effect of Full Table Scans is the increase of I/O operations.

The most noticeable symptoms of Full Table Scans are:

  • increase of CPU usage
  • increase of …
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MySQL Books: Efficient MySQL Performance

Today, the book I would like to recommend is Efficient MySQL Performance – Best Practices and Techniques, Daniel Nichter, O’Reilly, 2021.

I participated (just a bit) in the writing of this book as technical reviewer with Vadim and Fipar. I really enjoyed that role of carefully reading the early drafts of the chapters Daniel was writing.

Although Daniel says the book is not for the experts, I think even experts will enjoy it because several key InnoDB concepts are also covered. You can see that I refer to the book often in my A graph a day, keeps the doctor away ! series on monitoring and trending.

If you’re looking for information on transaction isolation and undo logs, fuzzy checkpointing, etc… you’ll find …

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A graph a day, keeps the doctor away ! – MySQL Checkpoint Age

In a previous post, I explained how you can collect and plot metrics using MySQL Shell.

This is a new series of article where I will explain how to read and understand some of the generated graphs.

Understanding your workload and seeing the evolution of it over time can help anticipating problems and work on solutions before the breakdown.

Let’s start the series with a concept that is not always well understood or at least not always considered at its true value: MySQL Checkpoint Age.

example of checkpoint age graphInnoDB Checkpointing

Before analyzing the graph, we need to understand what is MySQL InnoDB Checkpointing.

Each change to a data page in the InnoDB Buffer Pool are also written into the Write Ahead Logs.

In the literature they are sometimes called Transaction …

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Extending MySQL using the Component Infrastructure – part 12: instrument your code

This post is the twelfth one of a series of articles on extending MySQL with the Component Infrastructure:

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Using MySQL Database Service in OCI – Part 2: importing Data to MySQL DB System

This post is the second of a series of articles dedicated to MySQL Database Service (MDS):

The goal of this series if to get familiar with MDS, HeatWave and useful MySQL Shell utilities.

Before we start, I would like to highlight that the fastest and recommended way to import data to a MySQL DB System in OCI is to use a parallel dump created using MySQL to Object Storage and load it …

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