PoStorm - programming category

Pebble Blog Configuration

Mon, 14 Dec 2009 16:32:00 GMT

When configuring Pebble for my blog, there were a couple of things I had to search quite hard to discover.

1. Enablng email notifications.
2. Long Post names (names that include the title of the post -- which is much better for search engines (ie Google).

See http://www.laliluna.de/blog/2007/02/01/blogs_pebble_tomcat_installation.html for help on #1.

For #2. Under Configurations ... plugins .... Permalink Provider ... change the default
net.sourceforge.pebble.permalink.DefaultPermalinkProvider
to
net.sourceforge.pebble.permalink.TitlePermalinkProvider

Like column

Mon, 23 Jun 2008 17:17:00 GMT

Like column

Create table t1 ( x int unsigned default 911, y like x )

Create table t2 (x like t1.x)

Tricky extension

Create table t2 (x always like t1.x)

Meaning that

alter table t1 modify x int signed

implies a corresponding alter on t2

The purpose of ‘LIKE’ is to avoid multiply specifying that which must always be the same. LIKE both documents the dependency, and eliminates the possibility of inconsistency. ALWAYS LIKE prevents the inconsistency developing in the future.

ALTER Initial

Sun, 15 Jun 2008 17:14:00 GMT

ALTER Initial

Alter table this,that (ie. ALTER with multiple changes) appears to be optimized perform a single pass thru a table (at least sometimes) to perform the multiple changes. Some changes require column expression evaluation. These could be done with the alter

E.g.

Alter table xxx, add column negative bit initial quantity<0, modify quantity int unsigned initial abs(quantity)

This changes the representation of a column (‘quantity’) from a signed integer to an unsigned integer with a flag (‘negative’) to indicate that quantity is negative.

Alter table sales add unitprice dec(6,2) initial totalprice/quantity , drop totalprice

This alters a table, in a single pass, from recording the quantity and total price of sales, to recording quantity and unit price of sales. Without this extension it requires three passes through the table (1. Alter Add unitprice, 2 update set unitprice, 3 alter drop totalprice).

The meaning of the ‘initial’ clause is an expression that is computed based on the values in the row at the time the ALTER is performed for each row to set (or update) the value of the column.

BitOf(column,string)

Sat, 14 Jun 2008 17:07:00 GMT

BitOf(column,string)

Manipulating Column Type SETs cannot be readily (or efficiently) manipulated

Eg. Suppage the column Flags is defined as set(‘a’,’b’,’c’)

Update flags = flags_with_b_flipped.

This can be written using string manipulation – although it is messy - or can be written as

Flags=flags^2 /* b=~b */

But this depends on ‘b’ being the second item in the set declaration.

Flags=flags^bitOf(flags,’b’)

BitOf(column,string) means the bit-mask that represents string in the column definition. (not the current value of).

Limit [while|until] expression

Fri, 13 Jun 2008 16:51:00 GMT

Limit [while|until] expression

Performing sequential operations on set is a bitch, but this might help.

The MySQL extension ‘limit’ …

Select * from budget_candidates order by priority limit while sum(cost)<1000.00

This website is based on Pebble

Mon, 02 Jun 2008 00:51:00 GMT

I've been thinking about creating a website like this for years, but I never go around to it.

I'm a programmer so if I want something done by a computer my natural reaction is to program it myself -- which is why I never got around to making this site. So I eventually decided to see what's out there is Open Source land. I specifically wanted something in Java technologies - because that's what I use most of the time, and I have Tomcat servers available to use.

I tried out JSPBLOG - particularly because it stores the blog data in MySQL, which is my prefered storage for pretty much all data. JSPBLOG didn't work out ofthe box -- how could it without the appropriate information for locating a MySQL database. There seemed to be no installation instructions and no indication of the problem. It just gave a blank page.

I tried Pebble. It didn't say where it kept the data, although by implication it isn't MySQL. But it was a dream to install - less than the 5 minutes claimed, and doing nothing complicated. (Assuming, that it is, you have a Tomcat server :-) and you know what you are doing with Tomcat.)

It came up straightaway and appeared to be fully functional. It has an impressive amount of function, and, when considered with all the related open source components is a wonderful example of open source at its best.