In posts on June 30 and July 6, we explained how implementing the commands “replace into” and “insert ignore” with TokuDB’s fractal trees data structures can be two orders of magnitude faster than implementing them with B-trees. Towards the end of each post, we hinted at that there are some caveats that complicate the story a little. In this post, we explain one of the complications: the calculation of affected rows.

MySQL returns the number of rows affected by a “replace” or “insert” statement to the client. For the “replace” statement, the number of affected rows is defined to be the sum of the number of rows …

I was asked to write a blog post about MySQL High Availability at Yahoo, particularly for writes. Our standard practice is not particularly high-tech, but we've been using it for over 4 years now and it has become a company-wide standard with a few exceptions.   Let me start by saying that at Yahoo! we consider a datacenter as a Single Point of Failure (SPoF). We build and manage many of our own datacenters, and we still don't assume they are invulnerable. How many people can attest to the fact that however to configure your racks, how many redundant switches, power supplies, drives, etc. you buy, if your leased datacenter has power or network issues, you are at their mercy.  

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I have started seriously using PHP 5.3 recently due to it finally making it into Portage. (Gentoo really isn't full of bleeding edge packages people.) I have used mysqlnd a little here and there in the past, but until it was really coming to my servers I did not put too much time into it.

What is mysqlnd?

mysqlnd is short for MySQL Native Driver. In short, it is a driver for MySQL for PHP that uses internal functions of the PHP engine rather than using the externally linked libmysqlclient that has been used in the past. There are two reasons for this. The first reason is licensing. MySQL is a GPL project. The GPL and the PHP License don't play well together. The second is better memory management and hopefully more performance. Being a performance junky, this is what peaked my interests. Enabling mysqlnd means it is used by the older MySQL extension, the newer MySQLi extension and the MySQL PDO …

In this chapter we discuss timeouts which can lead to "MySQL server has gone away" and "Lost connection to MySQL server" errors.

 Extract here is short, because there are a lot of code quotes which I can not properly format here.

Chapter 9. Misterious vanishing of the server.

Often this looks like:


$php phpconf2009_3.php

string(26) "MySQL server has gone away"


Code:

...

Rest of the chapter is here

OUTER JOIN queries in SQL are susceptible to two very subtle bugs that I’ve observed a number of times in the real world. Daniel and I have been hammering out ways to automatically detect queries that suffer from these bugs, in a relatively new Maatkit tool called mk-query-advisor. It’s part of our series of advisor tools for MySQL. I wrote a blog post about it a while ago. Automated analysis of bad query patterns is a good thing to write tools to do, because catching buggy queries is hard work if you do it manually.

Let’s dive right in and analyze these subtle bugs. Warning: if you don’t understand how SQL handles NULL, you’re not going to understand the following. Many people have a hard time with NULL, which is why these bugs are so hard to …

In this chapter we discuss timeouts which can lead to "MySQL server has gone away" and "Lost connection to MySQL server" errors.

 Extract here is short, because there are a lot of code quotes which I can not properly format here.

Chapter 9. Misterious vanishing of the server.

Often this looks like:


$php phpconf2009_3.php

string(26) "MySQL server has gone away"


Code:

...

Rest of the chapter is here

As olap4j heads towards release 1.0, there are further signs that it is coming of age, in the form of drivers for the Palo MOLAP engine and SAP BW.

A few days ago Paul Stoellberger announced that olap4j's XMLA driver could connect to SAP BW, and posted pictures of PAT, PRD and PDI to prove it.

And just a week later, Jedox CEO Kristian Raue writes about how to connect to Palo. His post includes a blessedly short Java program …

(Reposted from the HailDB Blog. See also the announcement on the Drizzle Blog.)
We’ve made our first HailDB release! We’ve decided to make this a very conservative release. Fixing some minor bugs, getting a lot of compiler warnings fixed and start to make the name change in the source from Embedded InnoDB to HailDB.

Migrating your software to use HailDB is really simple. In fact, for this release, it shouldn’t take more than 5 minutes.

Highlights of this release:

• A lot of compiler warnings have been fixed.
• The build system is now pandora-build.
• some small bugs have been fixed
• Header file is now haildb.h instead of innodb.h
• We display “HailDB” instead of …

As described in the prior post, the shared-disk performance dilemma is simple:

1. If each node stores/processes data in memory, versus disk, it is much faster.
2. Each node must expose the most recent data to the other nodes, so those other nodes are not using old data.

In other words, #1 above says flush data to disk VERY INFREQUENTLY for better performance, while #2 says flush everything to disk IMMEDIATELY for data consistency.

Oracle recognized this dilemma when they built Oracle Parallel Server (OPS), the precursor to Oracle Real Application Cluster (RAC). In order to address the problem, Oracle developed Cache Fusion.

Cache fusion is a peer-based shared cache. Each node works with a certain set of data in its local cache, until another node needs that data. When one node …

So you thought that just because MySQL Cluster 7.1 is GA on Windows that NDB API was available and you could just download the MySQL Cluster 7.1 binary for Windows and start hacking the NDB API. Nope. But fear not, there is help!

And before I go on with that: For all you *ix users here, who claim that no one in their right mind would use MySQL Cluster on Windows, let me tell you that you may well be right! But, and this may be a not so PC statement: Although I like and use *ix (I've actually been using *ix for close to 30 years) as a server platform, when it comes to the desktop, I think Windows still has the edge. There is just too many options on, say Linux, too little coherence and too little commonality between applications. And it sure is getting better, very much so, but there is still some way to go.

So then, when we have my reasons for me doing what I am currently doing behind our backs, what I am trying to …