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Adjacency list vs. nested sets: MySQL

Continuing the series:

What is better to store hierarchical data: nested sets model or adjacency list (parent-child) model?

For detailed explanations of the terms, see the first article in the series:

This is the last article of the series which covers MySQL.

MySQL differs from the other systems, since it is the only system of the big four that does not support recursion natively. It has neither recursive CTE’s nor CONNECT BY clause, not even rowset returning functions that help to emulate recursion in PostgreSQL 8.3.

MySQL supports a thing that all other systems …

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Open Source load testing tool

See http://perfwork.wordpress.com/2009/09/29/oss-load-testing-tool/

SSD Vendors: Please let developers obtain extended health and # of erase cycle stats on your SSDs.

Here’s the problem I currently have.

We’re looking at deploying the Intel X-25M MLC SSD in production.

The problem being that this drive has a lower number of erase cycles but is much cheaper. Than the Intel X-25E SLC drive.

However, in our situation we’re write once, read many. I’m 99% certain that we will not burn out these drives. We write data to disk once and it is never written again.

The problem is that I can’t be 100% sure that this is the case. There is btree flushing, and binary log issues that I’m worried about…

What would be really nice is an API (SMART?) that I can enumerate the erase blocks on the drive, determine the max erase cycles, and read the current number of erase cycles.

This way, I can put an SSD into production, then determine the ETA to failure.

I …

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Cycle of Acquiring Knowledge

I have been doing some reading into data mining recently. It's really interesting stuff. To explain it, lets take an example:Lets say you work in a business that has been working for some years. They have their own way of running themselves and their processes. One day someone comes along and suggests that the business should automate some of their procedures by developing a website that would interact with customers and process their orders. Some nice PHP/MySQL guy or girl is hired and develops the website and the cycle of acquiring knowledge has unwittingly started.
The diagram below describes how management starts to process its own business knowledge and passes them down the chain so they can be implemented into the application.Eventually, every transaction is saved in the database. Over time, the database has more and more data and then the management of the company asks to get reports from this data.
Why would they ask that? …

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Open Source load testing tool

See http://perfwork.wordpress.com/2009/09/29/oss-load-testing-tool/

Open Source load testing tool

See http://perfwork.wordpress.com/2009/09/29/oss-load-testing-tool/

Free MySQL webinar today – High Availability Architectures for Online Applications

Update: You can now download a recording of the webinar and the slides from http://www.mysql.com/news-and-events/on-demand-webinars/display-od-403.html

I’ll be presenting the fourth (and final) session of the MySQL for Online Applications webinar series today (29 September). Today’s High Availability Architectures for Online Applications webinar covers:

  • MySQL Replication
  • MySQL Cluster
  • Distributed Replicated Block Device (DRBD)
  • Other high-availability technologies

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MySQL University: InnoDB File Formats and Source Code Structure

This Thursday (October 1st, 14:00 UTC), Calvin Sun will give a session on InnoDB Internals: InnoDB File Formats and Source Code Structure. The InnoDB storage engine provides transactions, row-level locking, and automatic crash recovery. Its on-disk files play a pivotal role for those key features. This presentation describes how on-disk files are structured, how compressed tables are organized, and how long variable-length columns are stored. As we develop new features, it is inevitable for file format changes. We will explain how the new file format management works in the InnoDB Plugin.This talk also covers InnoDB source code structure.

For MySQL University sessions, point your browser …

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Backup MySQL in a Second with ZFS

MySQL backup soon becomes an important matter when the database is used in production. The pain-point comes from the fact that while backuping the database is not available to respond to client requests anymore. With mysqldump - the standard tool for performing MySQL backups - and a large database the operation can go over many tenth of minutes if not hours. If I am running my business on line this is simply not acceptable.

The classical approach to workaround this problem is to take advantage of MySQL replication. I set up a master/slave configuration where the slave acts as copy of the master. Then, when needed, I run mysqldump on the slave without any service interruption on the master.

But ZFS snapshosts bring a new straightforward approach that avoids the pain and the complexity of a master/slave replication.

Snapshots are a key feature of ZFS that allows me to save a copy of …

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What data types does your innovative storage engine NOT support?

I’ve been investigating a few different storage engines for MySQL lately, and something I’ve noticed is that they all list what they support, but they generally don’t say what they don’t support. For example, Infobright’s documentation shows a list of every data type supported. What’s missing? Hmm, I don’t see BLOB, BIT, ENUM, SET… it’s kind of hard to tell. The same thing is true of the list of functions that are optimized inside Infobright’s own code instead of at the server layer. I can see what’s optimized, but I can’t see whether FUNC_WHATEVER() is optimized without scanning the page — and there’s no list of un-optimized functions.

I don’t mean to pick on Infobright. I’ve recently looked at another third-party storage engine and they did exactly the same thing. It’s just that the docs I saw weren’t public as …

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