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Displaying posts with tag: Performance (reset)
Fun with Bugs #66 - On MySQL Bug Reports I am Subscribed to, Part VI

I have some free time today, but I am still lazy enough to work on numerous planned and pending "ToDo" kind of posts, so why not to continue review of older MySQL bugs I am subscribed to. Today I am going to list 15 more bugs reported more than a year ago and still not fixed:

  • Bug #85805 - "Incorrect ER_BAD_NULL_ERROR after LOAD DATA LOCAL INFILE". This detailed bug report by Tsubasa Tanaka stays "Verified" for more than a year already. It's a great example of gdb use for MySQL troubleshooting. Setting a couple of breakpoints may really help to understand how MySQL works and why some …
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Fun with Bugs #65 - On MySQL Bug Reports I am Subscribed to, Part V

I think it's time to review some bugs I've subscribed to several months ago, those older than in the first post from this series. There are several really serious bugs in the list of 15 below:

  • Bug #87560 - "XA PREPARE log order error in replication and binlog recovery". This bug was reported by Wei Zhao, who also provided patches.
  • Bug #87526 - "The output of 'XA recover convert xid' is not useful". This bug reported by Sveta Smirnova is well known and is a real pain for DBAs who have to deal with incomplete XA transactions after some crash or unexpected restart. Check  …
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Concurrent sandbox deployment


Version 0.3.0 of dbdeployer has gained the ability of deploying multiple sandboxes concurrently. Whenever we deploy a group of sandboxes (replication, multiple) we can use the --concurrent flag, telling dbdeployer that it should run operations concurrently.

What happens when a single sandbox gets deployed? There are six sets of operations:

  1. Create the sandbox directory and write down its scripts;
  2. Run the initialisation script;
  3. Start the database server;
  4. Run the pre-grants SQL commands (if any;)
  5. Load the grants;
  6. Run the post-grants SQL commands (if any;)

When several …

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MyISAM and KPTI – Performance Implications From The Meltdown Fix

Recently we had a report from a user who had seen a stunning 90% performance regression after upgrading his server to a Linux kernel with KPTI (kernel page-table isolation – a remedy for the Meltdown vulnerability). A big deal of those 90% was caused by running in an old version of VMware which doesn’t pass […]

The post MyISAM and KPTI – Performance Implications From The Meltdown Fix appeared first on MariaDB.org.

Choosing the best indexes for MySQL query optimization

Many of our users, developers and database administrators, keep asking our team about EverSQL’s indexing recommendations algorithm.

So, we decided to write about it.

This tutorial won’t detail all the internals of the algorithm, but rather try to lay down the basic and important aspects of indexing, in simple terms.
Also, and most importantly, we’ll present practical examples for properly indexing your tables and queries by relying on a set of rules, rather than on guessing.

Our focus in this tutorial is on MySQL, MariaDB and PerconaDB databases. This information may be relevant for other database vendors as well, but in some cases may not.

Which indexes should I create for an SQL query?

As a general rule of thumb, MySQL can only use on index for each table in the query. Therefore, there is no point in creating more than one index for each query. Preferably, same indexes should match as …

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MySQL Query Performance: Not Just Indexes

In this blog post, I’ll look at whether optimizing indexing is always the key to improving MySQL query performance (spoiler, it isn’t).

As we look at MySQL query performance, our first concern is often whether a query is using the right indexes to retrieve the data. This is based on the assumption that finding the data is the most expensive operation – and the one you should focus on for MySQL query optimization. However, this is not always the case.

Let’s look at this query for illustration:

mysql> show create table tbl G
*************************** 1. row ***************************
      Table: tbl
Create Table: CREATE TABLE `tbl` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `k` int(11) NOT NULL DEFAULT '0',
 `g` int(10) unsigned NOT NULL,
 PRIMARY KEY (`id`),
 KEY `k_1` (`k`)
) ENGINE=InnoDB …
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Webinar Thursday, January 25, 2018: Troubleshooting MySQL Crashes

Please join Percona’s Principal Support Engineer, Sveta Smirnova, as she presents Troubleshooting MySQL Crashes on January 25, 2018, at 10:00 am PST (UTC -8) / 1:00 pm EST (UTC -5).

Register Now

 

This webinar is for every MySQL user! In this talk, I won’t focus on how to analyze core files, read the source code or set breakpoints. Instead, I will focus on techniques that are available to anyone, even a novice.

Many tutorials, including my own, written based on Roel Van de Paar’s video, suggest how to create and analyze core files created at the time of a crash. While this …

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Does the Meltdown Fix Affect Performance for MySQL on Bare Metal?

In this blog post, we’ll look at does the Meltdown fix affect performance for MySQL on bare metal servers.

Since the news about the Meltdown bug, there were a lot of reports on the performance hit from proposed fixes. We have looked at how the fix affects MySQL (Percona Server for MySQL) under a sysbench workload.

In this case, we used bare metal boxes with the following specifications:

  • Two-socket Intel(R) Xeon(R) CPU E5-2683 v3 @ 2.00GHz (in total 56 entries in /proc/cpuinfo)
  • Ubuntu 16.04
  • Memory: 256GB
  • Storage: Samsung SM863 1.9TB SATA SSD
  • Percona Server for MySQL 5.7.20
  • Kernel (vulnerable) 4.13.0-21
  • Kernel (with Meltdown fix) 4.13.0-25

Please note, the current kernel for Ubuntu 16.04 contains only a Meltdown fix, …

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Measuring the potential overhead of PMM Client on MySQL workloads

Having good historial metrics monitoring in place is critical for properly operating, maintaining and troubleshooting database systems, and Percona Monitoring and Management is one of the options we recommend to our clients for this.

One common concern among potential users is how using this may impact their database’s performance. As I could not find any conclusive information about this, I set out to do some basic tests and this post shows my results.

To begin, let me describe my setup. I used the following Google Cloud instances:

  • One 4 vCPU instance for the MySQL server
  • One 2 vCPU instance for the sysbench client
  • One 1 vCPU instance for the PMM server

I used Percona Server 5.7 and PMM 1.5.3 installed via Docker. Slow query log was enabled with long_query_time set to 0 …

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Top 10 things to know about Alibaba Cloud RDS

Cloud-based Relational Database Services (RDS) offer businesses a variety of traditional Relational Database Management Systems (RDBMS) with several management and configuration options. In the Top 10 Things to Know about Amazon RDS blog, we covered Amazon RDS. In today’s article, we’ll be presenting Alibaba Cloud RDS. If you’ve been considering moving some or all of your database infrastructure to Alibaba Cloud RDS, or any Cloud RDS for that matter, there are many things to consider. Here are the top 10 things you need to know before taking the plunge.

About Alibaba Cloud RDS

Alibaba Cloud RDS, whose full name is Alibaba Cloud ApsaraDB for RDS, is an on-demand database service that handles some of the administrative tasks associated with managing a database, thus leaving you with more time to focus on your core business. …

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