I've often suspected that I'm not a SQL guru... little things like being self taught and having virtually no resources for learning it. This has been confirmed to a large degree at work, where our DBA has taught me many tricks about databases: indexing, when to use DISTINCT, how and when to do JOINs, and the magic of TEMPORARY TABLEs. I now feel fairly competent, though far from being an expert -- I certainly don't know much about how to tune a server for MySQL, or tuning MySQL for performance.
Last year around this time, we needed to replace our MySQL server, and I got handed the job of getting the data from the old one onto the new. At the time, I looked into replication, and from there discovered about binary copies of a data store. I started using this as a way to backup data, instead of periodic mysqldumps.
One thing I've often wondered since: would replication be a good way to do backups? It seems like it would, but I haven't investigated. One post on the aforementioned Slashdot article addressed this, with the following summary:
Concise and to the point. I only wish I had a spare server on which to implement it!
I've standardized my PHP programming to use the environment variable SCRIPT_NAME when I want my script to refer to itself in links and form actions. I've known that PHP_SELF has the same information, but I was more familiar with the name 'SCRIPT_NAME' from using it in perl, and liked the feel of it more as it seems to describe the resource better ('PHP_SELF' could stand for the path to the PHP executable if I were to go by the name only).
However, I just noticed a post on the php.general newsgroup where somebody asked what the difference was between them. Semantically, there isn't any; they should contain the same information. However, historically and technically speaking, there is. SCRIPT_NAME is defined in the CGI 1.1 specification, and is thus a standard. However, not all web servers actually implement it, and thus it isn't necessarily portable. PHP_SELF, on the other hand, is implemented directly by PHP, and as long as you're programming in PHP, will always be present.
Guess I have some grep and sed in my future as I change a bunch of scripts...
Occasionally, I've needed to process a lot of information from a script, but I don't want to worry about PHP timing out or the user aborting the script (by clicking on another link or closing the window). Initially, I investigated register_shutdown_function() for this; it will fire off a process once the page finishes loading. Unfortunately, the process is still a part of the current connection, so it can be aborted in the same way as any other script (i.e., by hitting stop, closing the browser, going to a new link, etc.).
However, there's another setting initialized via a function that can override this behaviour -- i.e., let the script continue running after the abort. This is ignore_user_abort(). By setting this to true, your script will continue running after the fact.
This sort of thing would be especially good for bulk uploads where the upload needs to be processed -- say, for instance, a group of images or email addresses.
In the past two days, I've seen two references to Practical PHP Programming, an online book that serves both as an introduction to programming with PHP5 and MySQL as well as a good advanced reference with many good tips.
This evening, I was browsing through the Performance chapter (chapter 18), and found a number of cool things, both for PHP and MySQL. Many were common sense things that I've been doing for awhile, but which I've also seen and shaken my head at in code I've seen from others (calculating loop invariables at every iteration, not using variables passed to a function, not returning a value from a function, not using a return value from a function). Others were new and gave me pause for thought (string concatenation with the '.' operator is expensive, especially when done more than once in an operation; echo can take a comma separated list).
Some PHP myths were also dispelled, some of which I've been wondering about for awhile. For instance, the amount of comments and whitespace in PHP are not a factor in performance (and PHP caching systems will often strip them out anyways); double quotes are not more expensive than single quotes unless variable interpolation occurs.
It also has some good advice for SQL optimization, and, more importantly, MySQL server optimization. For instance, the author suggests running 'OPTIMIZE TABLE table;' on any table that has been added/updated/deleted from to any large extent since creation; this will defrag the table and give it better performance. Use CHAR() versus VARCHAR(); VARCHAR() saves on space, but MySQL has to calculate how much space was used each time it queries in order to determine where the next field or record starts. However, if you have any variable length fields, you may as well use as many as you need -- or split off variable length fields (such as a TEXT() field) into a different table in order to speed up searching. When performing JOINs, compare on numeric fields instead of character fields, and always JOIN on rows that are indexed.
I haven't read the entire book, but glancing through the TOC, there are some potential downfalls to its content:
All told, there's plenty of meat in this book -- I wish it were in dead tree format already so I could browse through it at my leisure, instead of in front of the computer.
Those who know me know that I love linux and open source. One particular program that firmly committed me to open source software is the Mozilla project -- a project that took the Netscape browser's codebase and ran with it to places I know I never anticipated when I first heard of the project.
What do I like about Mozilla? Well, for starters, and most importantly, tabbed browsing changed the way I work. What is tabbed browsing? It's the ability to have multiple tabs in a browser window, allowing you to switch between web pages without needing to switch windows.
Mozilla came out with a standalone browser a number of months back called, first Phoenix, then Firebird, and now Firefox. This standalone browser has a conservative number of basic features, which allow for a lean download -- and yet, these basic features, which include tabbed browsing and disabling popups, far surpass Internet Explorer's features. And there are many extensions that you can download and integrate into the browser.
One such extension is a tabbed browsing extension that makes tabbed browsing even more useful. With it, I can choose to have any links leaving a site go to a new tab; or have bookmarks automatically load in a new tab; or group tabs and save them as bookmark folders; or drag a tab to a different location in the tabs (allowing easy grouping).
Frankly, there's few things I can find that Firefox can't do.
And, on top of that, it's not integrated into the operating system. So, if you're on Windows, that means if you use Firefox, you're less likely to end up with spyware and adware -- which often is downloaded and installed by special IE components just by visiting sites -- ruining your internet experience.
So, spread the word: Firefox is a speedy, featureful, SECURE alternative to Internet Explorer!
I've had a few people contact me indicating interest in Cgiapp, and I've noticed a number of subscribers to the freshmeat project I've setup. In addition, we're using the library extensively at the National Gardening Association in developing our new site (the current site is using a mixture of ASP and Tango, with several newer applications using PHP). I've also been monitoring the CGI::Application mailing list. As a result of all this activity, I've decided I need to develop a roadmap for Cgiapp.
Currently, planned changes include:
$this->tmpl_assign('var1', 'val1'); $body = $this->load_tmpl('template.html');Becomes this:
$tmpl = $this->load_tmpl(); $tmpl->assign('var1', 'val1'); $body = $tmpl->fetch('template.html');OR
$tmpl = $this->load_tmpl('template.html'); $tmpl->assign('var1', 'val1'); $body = $tmpl->fetch();(Both examples assume use of Smarty.) I want to revert to this behaviour for several reasons:
If you have any requests or comments on the roadmap, please feel free to contact me.
The new weierophinney.net/matthew/ site is now up and running!
The site has been many months in planning, and about a month or so in actual coding. I have written the site in, instead of flatfiles, PHP, so as to:
I've written it using a strict MVC model, which means that I have libraries for accessing and manipulating the database; all displays are template driven (meaning I can create them with plain-old HTML); and I can create customizable applications out of various controller libraries. I've called this concoction Dragonfly.
There will be more developments coming -- sitewide search comes to mind, as well as RSS feeds for the blog and downloads.
Ever wonder what's keeping that device in use so you can't unmount it? It's happened to me a few times. The tool to discover this information? lsof.
Basically, you type something like: lsof /mnt/cdrom and it gives you a ps-style output detailing the PID and process of the processes that are using the cdrom. You can then go and manually stop those programs, or kill them yourself.
Okay, so that's actually direct quotes from the article. I took issue with it, immediately -- I use Smarty for everything I do, and the decision to do so was not done lightly. I have in fact been advocating the use of template engines in one language or another for several years with the various positions in which I've been employed; I think they are an essential tool for projects larger than a few pages. Why?
So, reading the aforementioned article really got my hackles up. However, it got me thinking, as well. One issue raised is that PHP can be used as your templating language. While I can understand why this might be desirable -- everything from load issues to flexibility -- I also feel that this doesn't give enough abstraction.
Using PHP seems to me to be inefficient on two fundamental levels, based on my understanding of The Pragmatic Programmer:
The author of the article also makes a case for teaching web designers PHP -- that the language is sufficiently easy to pick up that they typically will be able to learn it as easily, if not more easily, than a template language. I agree to a degree... But my experience has shown that web designers typically struggle with HTML, let alone PHP. (Note: my experience in this regard is not huge, and I'm sure that this is an exaggeration.) I find that it's typically easiest for me to give an example template, explain what the funny, non-HTML stuff can do, and let them go from there. Using this approach, they do not need to learn anything new -- they simply work with placeholders.
Still, I think the author raises some fine points. I wish he'd bothered to do more research into why people choose template engines and the benefits that arise from using them before simply outright slamming them. Of course, the article is also a bit dated; it was written over two years ago, and much has changed in the world of PHP and many of its template engines. I'm curious as to whether they would feel the same way today.
Me? My mind is made up -- the benefits, in my circumstances, far outweigh any costs associated. I'll be using template engines, and Smarty in particular, for years to come.
I'd read that you could get binary packages for gentoo, thus alleviating the need to compile everything. (Of course, then you lose some of the benefits of compiling everything, but you gain in speed...) Unfortunately, I mistook this with ebuilds, and never quite figured it out.
The key is to throw the -g flag:
% emerge -g gnumeric # which is like 'emerge --getbinpkg gnumeric'
I also learned how to update packages tonight:
% emerge sync # to sync your mirror with the gentoo mirrors % emerge --update portage # if necessary % emerge --update system # updates core system files % emerge --update world # updates all packages