Scrum Video

I found this video on Scrum very interesting. If you aren't experienced or only marginally experienced with Scrum you should invest the hour of time and watch it. It is a recording of a presentation at Google, hosted on YouTube and titled "Scrum et al."

Browsing MySQL from Command Line

To view a MySQL schema from the command line, use the commands show tables; and describe . See the following example:

mysql> show tables
    -> ;
+------------------+
| Tables_in_email  |
+------------------+
| access_sender    | 
| alias            | 
| transport        | 
| user2domains     | 
+------------------+
4 rows in set (0.00 sec)

mysql> describe alias 
    -> ;
+----------+------------------+------+-----+
| Field    | Type             | Null | Key | 
+----------+------------------+------+-----+
| id       | int(11) unsigned | NO   | PRI | 
| username | varchar(128)     | NO   |     |
| domain   | varchar(128)     | YES  |     | 
| enabled  | enum('Y','N')    | NO   |     |
| goto     | varchar(128)     | NO   |     |
| notes    | varchar(255)     | YES  |     |
| updated  | timestamp        | NO   |     |
+----------+------------------+------+-----+
7 rows in set (0.00 sec)

Google Solar?

Google is investing in solar energy. (Google actually invests in many things, they have to with as much cash as they are bringing in each year.) Google has some of its own engineers looking specifically at producing cheap mirrors for solar thermal power plants. A Reuters article covers the concept.

Weihl said Google is looking to cut the cost of making heliostats, the fields of mirrors that have to track the sun, by at least a factor of two, "ideally a factor of three or four."

"Typically what we're seeing is $2.50 to $4 a watt (for) capital cost," Weihl said. "So a 250 megawatt installation would be $600 million to a $1 billion. It's a lot of money."

Migrating Subversion Repositories

I needed to migrate a small subversion repository from one machine to one in a more reliable location (a data center). After reading a few pages I realized that in practice this is pretty easy and here is the basic to do steps for performing the migration on unix systems.

1. svnadmin dump repository | gzip > Repository.dump.gz
   
2. Transfer file to new location if needed.
   
3. Create the new repository:
   svnadmin create /path/to/repository
   
4. gunzip -c Repository.dump.gz | svnadmin load /path/to/repository

Of interest is this note from the svn documentation.

If the migration process made your repository accessible at a different URL (e.g. moved to a different computer, or is being accessed via a different schema), then you'll probably want to tell your users to run svn switch --relocate on their existing working copies. See svn switch.

However for me it was easier to have the small group of developers just checkout new working directories.

Creating MySQL users

Neither I or my MySQL using friends know of a nice easy way to create users in MySQL. But 3 commands are all that is needed in the basic case.
Log into mysql as administrator (mysql -u root -p) and enter the following:

CREATE USER 'userName'@'localhost' IDENTIFIED BY 'userPassword';
grant all on DBName.* to 'userName'@'localhost';
flush privileges;

There is a convention for web apps is that the database and user that accesses it have the same name. This is not required but is a general practice. In the above example userName would be the same as DBName.

Dropping a database: drop database DBName;
Notice that you do not put any type of quotes around the data base name DBName.

Fun Calc 1.1

The iPhone application mentioned in a previous post has been up dated to version 1.1. It now speaks the numbers and arithmetic operators. This expands its appeal past that of parents wanting to entertain toddlers, to include those whose children are learning basic addition, subtraction, multiplication, and division. More can be learned at the friedricehouse page, and at the app's page on the iPhone app store.

Strange Xcode Error

I was helping someone that was getting a bizarre error message from XCode. The message was Error: Cannot use object as a parameter to a method. The line with the error:

- (NSString)formatPrice:(NSNumber *)priceNumber

This was some what misleading since you first look at the parameter for the method "priceNumber", but the error really referred to what was being returned from the method. The problem was the leading (NSString), which was a typo that should have been (NSString *). Easy to over look that with attention directed to the "parameter." Once that change was made, the code compiled and ran correctly.