BigSmoke

Smokes your problems, coughs fresh air.

Day: February 2, 2007

Using the standard HTML link colors

February 2, 2007 /

Occasionally, I have to foray into web design. From the look of this blog you can deduce that I’m not really into the design part of web design. First and foremostly this is because I suck at graphics and colors. But another reason is that I assume that people visit my blog to read some text and not to look at the fancy graphical borders and background of that text.

Recently I’ve gotten into the habit of simply using the default HTML link colors instead of trying to come up with a comprehensible color scheme for each design. This means that my links are blue, my visited links are purple and my active links are red as in the example CSS snippet below.

a:link {
 :;     /* #00f */
}
a:visited {
 :;   /* #800080 */
}
a:active {
 :;      /* #f00 */
}

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Unique constraints and indexes in PostgreSQL

February 2, 2007 /

This afternoon, I had to add a unique index for some table in the Sicirec PostgreSQL database. I had already assumed that I needed to use CREATE UNIQUE INDEX to create my new unique index until I noticed, thanks to pgAdmin‘s clear GUI, that some tables clearly had unique constraints and unique indexes while one table lacked a unique constraint and only had an unique index defined.

This motivated me to take a closer look at PostgreSQL’s documentation on unique indexes:

Note: The preferred way to add a unique constraint to a table is ALTER TABLE ... ADD CONSTRAINT. The use of indexes to enforce unique constraints could be considered an implementation detail that should not be accessed directly. One should, however, be aware that there’s no need to manually create indexes on unique columns; doing so would just duplicate the automatically-created index.

Grepping for CREATE UNIQUE INDEX in our migration history quickly revealed that the index which lacked an accompanying constraint was indeed created by CREATE UNIQUE INDEX instead of by ALTER TABLE ... ADD CONSTRAINT. So, now I know that, indeed, I have to use ALTER TABLE ... ADD CONSTRAINT instead of CREATE UNIQUE INDEX to add unique constraints with accompanying indexes to existing tables.

Copyleft: These days everything you can think of is copyrighted, patented, protected or otherwise made into someone's imaginary intellectual property. I have a lot of imagination but not enough to pretend that I have some divine right to share things with you without giving you the right to share it further. That would be childish. So, everything here is licensed under a Creative Commons Attribution-Noncommercial-Share Alike license. That means that you can bloody well do anything you like with my content as long as you tell that it's from me (or the respective author). Only if you want to make money from my content do you have to ask me permission first. (As if I could be bothered to sue.) Oh, and you can't redistribute your derivative content under more restrictive terms. Share the love.

Colophon: This weblog is powered by a WordPress installation running on PHP5 and MySQL, hosted by NearlyFreeSpeech.Net's outstanding FreeBSD hosting platform. The markup for this WP theme is my own and should usually validate as some sort of XHTML concoction. So should the CSS. I've actually blogged about this theme.

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