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Why Thread May Hang in "Waiting for table level lock" State - Part I

Last time I had to use gdb to check what's going on in MySQL server and found something useful with it to share in the blog post it was April 2017, and I miss this kind of experience already. So, today I decided to try it again in a hope to get some insights in cases when other tools may not apply or may not be as helpful as one could expect. Here is the long enough story, based on recent customer issue I worked on this week.
* * * Had you seen anything like this output of SHOW PROCESSLIST statement:

Id User Host db Command Time State 
Info Progress
...
28 someuser01 xx.xx.xx.xx:39644 somedb001 Sleep 247
NULL 0.000
29 someuser01 xx.xx.xx.yy:44100 somedb001 Query 276
Waiting for table level lock DELETE FROM t1 WHERE (some_id = 'NNNNN') AND ...
0.000 …
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MySQL Connector/J 5.1.43 has been released

Dear MySQL Users,

MySQL Connector/J 5.1.43, a maintenance release of the production 5.1 branch has been released. Connector/J is the Type-IV pure-Java JDBC driver for MySQL.

MySQL Connector Java is available in source and binary form from the Connector/J download pages at http://dev.mysql.com/downloads/connector/j/5.1.html and mirror sit
repositories.

MySQL Connector Java (Commercial) is already available for download on the My Oracle Support (MOS) website. This release will be available on eDelivery
(OSDC) in next month’s upload cycle.

As always, we recommend that you check the “CHANGES” file in the download archive to be aware of changes in behavior that might affect your application.

MySQL Connector/J 5.1.43 includes the following general bug fixes and improvements, also available in more detail on http://dev.mysql.com/doc/relnotes/connector-j/en
nges in MySQL Connector/J …

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Log Buffer #517: A Carnival of the Vanities for DBAs

This Log Buffer Edition covers Oracle, SQL Server and MySQL.

Oracle:

Protecting Financial Data with Oracle WebCenter and Adobe LiveCycle

Oracle Forms 12c oracle.security.jps.JpsException Error after Database change

The Future of Content Management: Oracle Content & Experience Cloud

Today Oracle released a very large „monster“ Upgrade. This July 2017 Update includes the first time the new RU „Release …

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Faster Node Rejoins with Improved IST performance

In this blog, we’ll look at how improvements to Percona XtraDB Cluster improved IST performance.

Introduction

Starting in version 5.7.17-29.20 of Percona XtraDB Cluster significantly improved performance. Depending on the workload, the increase in throughput is in the range of 3-10x. (More details here). These optimization fixes also helped improve IST (Incremental State Transfer) performance. This blog is aimed at studying the IST impact.

IST

IST stands for incremental state transfer. When a node of the cluster leaves the cluster for a short period of time and then rejoins the cluster it needs to catch-up with cluster state. As part of this sync …

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Fun with Bugs #54 - On Some Bugs Fixed in MySQL 5.7.19

More than 3 months after 5.7.18 we' ve got MySQL 5.7.19 released recently. This is my quick review of the release notes with interesting fixed bug (reported in public) highlighted in the areas I am usually interested in.

Let's start with InnoDB. The following bug fixes attracted my attention:

  • Bug #85043 is still private. You know how much I hate those. At least we can see it was about the fact that "The server allocated memory unnecessarily for an operation that rebuilt the table." Let's hope this is no longer the case.
  • Bug …
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Group Replication – Extending Group Replication performance_schema tables

In MySQL 8.0.2, users will see the additional columns in the existing Group Replication Performance Schema tables which will provide extended information about Group Replication. Now user can view role and MySQL version of each member of the group, which earlier required a complex set of query.…

How to interview an amazon database expert

via GIPHY Amazon releases a new database offering every other day. It sure isn’t easy to keep up. Join 35,000 others and follow Sean Hull on twitter @hullsean. Let’s say you’re hiring a devops & you want to suss out their database knowledge? Or you’re hiring a professional services firm or freelance consultant. Whatever the … Continue reading How to interview an amazon database expert →

The Rig

Back in May I wrote about a web service I’m working on that uses local storage and replication with two-phase commit. I pulled out the core of it and created a package that I’m calling the Rig.

It’s up on GitHub already: https://github.com/Preetam/rig

The goal of the Rig is to take some web service and add a log and replication on top.

A service is simply something that accepts operations.

type Service interface {
    Validate(Operation) error
    Apply(uint64, Operation) error
    LockResources(Operation) bool
    UnlockResources(Operation)
}

Each operation is associated with an entry in a log.

type LogPayload struct {
    Version uint64    `json:"version"`
    Op      Operation `json:"op"`
}

And …

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Group-Replication, sweet & sour

A story around replication lag and Flow-Control.

Overview

In the last few months we had 2 main actors in the the MySQL ecosystem, ProxySQL and Group-Replication (with the evolution to InnoDB Cluster). 

While I had extensively covered the first, my last serious work on GR, goes back to some lab version in the past years. 
Given the decision Oracle made to declare it GA, and the Percona decision to provide some level of support to GR, I decide it was time for me to take a look at it again.
A lot of reviews were already done covering different topics. I saw articles about GR and performance, GR and basic functionalities (or lack of it like automatic node provisioning), GR and ProxySQL and so on.

But one question was coming up over and over in my mind. If GR and InnoDB cluster has to work as alternative to other (virtually) synchronous replication …

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Blog Poll: What Operating System Do You Run Your Development Database On?

In this post, we’ll use a blog poll to find out what operating system you use to run your development database servers.

In our last blog poll, we looked at what OS you use for your production database. Now we would like to see what you use for your development database.

As databases grow to meet more challenges and expanding application demands, they must try and get the maximum amount of performance out of available resources. How they work with an operating system can affect many variables, and help or hinder performance. The operating system you use for your database can impact consumable choices (such as hardware and memory). The operating system you use can also impact your choice of database engine as well (or vice versa).

When new projects, new applications or services or testing new architecture …

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