I had a fun case today.

There is set of cache tables which cache certain content in MyISAM tables and queries for these tables such as:

PLAIN TEXT SQL:

1. SELECT DATA FROM cache0003 WHERE `key`=2342526263 AND real_key='cp_140797_6460aad5d2e50d3e859e8649007686ac';

The "key" is CRC32 of the real key which is used to keep index size as small as possible so if we have a cache miss we can in most case learn it without going to the disk.

So far so good.

The problem I discovered however is some of these queries would take enormous amount of time while CRC32 conflicts are really rare.

Looking deep into the problem I found out PHP and MySQL are both to blame. PHP is to blame because in 32bit PHP version result of crc32() function was returned as signed integer, in 64bit build of same PHP version it became signed.

The system worked on 32bit platform initially …

One of the features not yet mentioned that is in 5.1 is Federated's new "CREATE SERVER" command.

The synopsis?

Tired of typing URL's for Federated tables? AKA:

CREATE TABLE A (
`a_id` int(20) NOT NULL,
`some_string` varchar(128) NOT NULL default ''
)
ENGINE="FEDERATED" CONNECTION='mysql://joe@foo.example.com:3306/ schema_a/A';

With 5.1 you have a new option, the "CREATE SERVER" command.

CREATE SERVER 'master_database' foreign data wrapper 'mysql' options
(HOST '10.0.2.128',
DATABASE 'schema_a',
USER 'joe',
PASSWORD '',
PORT 3306,
SOCKET '',
OWNER 'root');

For the create table all you then need to do is:
CREATE TABLE A (
`a_id` int(20) NOT NULL,
`some_string` varchar(128) NOT NULL default ''
)
ENGINE="FEDERATED" CONNECTION='master_database'; …

Today is the first time I had to look at MySQL performance. Tiny database as web application back-end was having significant performance issues with spikes of CPU workload. After identifying problematic queries, I found a pile of statements using IN subqueries. Typical example is: SELECT * FROM t1 WHERE c1 IN (SELECT c1 [...]

...is by going to work for an open source company. I get people asking me all the time for career advice (Not sure why they ask me - it's not like I have a "career." I think that's what older folks have... :-). My advice is always the same:

"Work for an open source company."

The reason is simple economics. The market will basically pay you what it thinks you're worth, and your worth goes up exponentially when you have open source expertise. Open source, according to Gartner and nearly every sane person on the planet, continues to be one of the top three trends in technology. Consequently, if you're an enterprise (i.e., IT person) or an ISV, you want open source people.

And thus, if you're a would-be employee, you want to be wanted. You want open source experience.

It's an fact that every person I hire has their salary rate go up …

Being quite tied up in my daily job, I totally missed the that Oracle has been developing a database application development tool, SQL Developer. In fact, this tool was previously known as "project Raptor" and has now matured to version 1.1. The -to me- interesting news is that:

• 
  
• It's free of charge.
  
• It runs on Linux, Mac OS/X and Windows
  
• Besides the Oracle database, it also supports other databases, including MySQL
  

Ok - I know all free software adepts will probably have left by now for three reasons, being that the title of this blog entry contains "Oracle", the tool is "free as in beer" and of course because the tool runs on Microsoft Windows. But let's not be distracted. Let's …

I just want to write few tips how to get MySQL from development BitKeeper tree, as there are several tricks.
First of all you need a fresh free client - bk-client2.0 http://www.bitkeeper.com/Hosted.Downloading.html .
Once you get it, you can clone latest tree:
bkf clone bk://mysql.bkbits.net/mysql-5.0 mysql-5.0

New client supports "changes" command, so you can look latest changes
bkf changes in mysql-5.0 directory.
It may be useful to get sources related to specific release. MySQL build team marks tree by TAG
with each new release. What I have looking by existing TAGS:

bkf changes | grep TAG
TAG: clone-5.0.32-build
TAG: mysql-5.0.30
TAG: clone-5.0.30-build
TAG: mysql-4.1.22
TAG: clone-4.1.22-build
TAG: mysql-5.0.28
TAG: mysql-5.0.27
TAG: …

For those that attended the MySQL Camp at Google HQ late last year you may have seen me with my own T-Shirt designs. A number of people inquired about getting them. I’ve finally got around to make them available online, so anybody that would like one can order online.

There are two different shirts. If you want your name on the shirt, you need to make sure you choose the correct one.

• Early Adopters - For those that were the first 48 that signed up, your name as well as position and company are on the shirt.
• The Herd - For everybody that registered on the website, your name is on the shirt.

Ok. I’ve …

As has been pointed out, there is a new version (2.0) of the free BitKeeper client, and furthermore the old one (version 1.1) appears not to work anymore. At first I suspected my daughter's hogging of available bandwidth as the culprit when all of my daily pulls of MySQL source trees failed, but that soon proved not to be the case. I am once again pulling source code successfully.

ZRM for MySQL users manual has been rewritten based on user feedback. It is available at ZRM for MySQL wiki

Thanks to everyone who provided feedback. User contributions to the manual are welcome.

In both Sql Server and Oracle, permission changes to a user take into effect right away, even when said user is connected at the time you made the change.

In MySql, it is a little different, depending on how the permissions are given. If you use the GRANT statement, then it takes into effect right away. However, if you create user and give it permissions by manipulating the user table in the mysql system database directly, that is, using Sql statements, then you need to issue:

flush privileges

for those changes to be picked up.