Comments on: Deleting records with a limited life time

By: cakebaker

cakebaker — Thu, 09 Oct 2008 18:08:01 +0000

@Brett: Yes, that’s a feasible way, too. Thanks for sharing!

By: Brett ODonnell

Brett ODonnell — Thu, 09 Oct 2008 10:20:47 +0000

I prefer to use strtotime() like this:


// in the RequestToken model
public function deleteExpired() {
    $this->deleteAll(array('RequestToken.modified <=' => date('Y-m-d H:i:s',strtotime('-24 hours'))));
}

By: cakebaker

cakebaker — Tue, 07 Oct 2008 09:29:22 +0000

@Pixelastic: Yes, as soon as your server is in a different timezone than your visitors and you want to show them date-related things it becomes tricky.

One approach is, as you did, to deal with all date-related stuff directly in PHP. A different approach could be to work with the difference between the timezone of the server and the timezone of the visitors. Everytime you read dates from the database you add/subtract the difference.

But I have to admit that I don’t have any real experience with such scenarios…

By: Pixelastic

Pixelastic — Mon, 06 Oct 2008 17:17:10 +0000

As I’ve just realized, uploading my app from prod to dev, this approach seems to have its limits when your mysql server is in another timezone than your visitors.

I have a site where items are displayed based on the time they where modified (auto-populated field modified of cakePHP).

First problem, dates were stored in the database according to the server where PHP were running.
I had to change the timezone used by php by putting a SetEnv TZ Europe/Paris in my .htaccess and a date_default_timezone_set(‘Europe/Paris’); in my bootstrap.php to correct that.

But as my app is running on a shared server, I can’t change the mysql timezone (only root can do that), thus can’t use mysql built-in NOW(), INTERVAL() and such functions.
So I had to re-re-write back all my SELECT queries, using php generated dates instead of mysql built-in ones.

Or maybe did I overlooked something ?

By: cakebaker

cakebaker — Tue, 16 Sep 2008 15:57:08 +0000

@Rafael, Pixelastic: Thanks for your comments!

@Rafael: Yes, the date and time functions are very powerful.

I don’t know the official name of that pattern, but I think it is a kind of a facade. And yes, it is a possible way for the implementation. Personally, I’m not a big fan of using this approach to reduce the number of public methods of a class, as it makes your API implicit, i.e. you have to look in the source or the documentation to figure out what the method does…

By: Pixelastic

Pixelastic — Mon, 15 Sep 2008 19:42:57 +0000

Nice one, I was trying to do the same thing by using the array(‘conditions’ => array()) syntax but it didn’t work because fields were treated as string (and escaped with ‘)

I had to make my calculation directly in php with mktime() and date() before putting it in the query, but your approach is nice

By: rafaelbandeira3

rafaelbandeira3 — Mon, 15 Sep 2008 18:44:24 +0000

good one Daniel, docs on MySQL Date and Time functions are a must-read for every dev. In my current – and endless – project I moved lots of time and date handling from the app layer – good & old php – to db queries, and I must say, the gain is not only on performance but in readability and api size for models.

Now just a buggy thought: Why not follow the pattern jQuery follows – I don’t know if it has a name – and that we already do with Model::find(), letting all related operations in just one method, then your method would be more like:

function deleteAll($conditions, $cascade = true, $callbacks = false) {
     if($conditions === 'expired') {
          $conditions = array('RequestToken.modified <= DATE_SUB(NOW(), INTERVAL 24 HOUR)');
     } elseif($conditions === 'invalid') {
          $conditions = array('CheeseCake.flavor != "cheese"');
     }
     return parent::deleteAll($conditions, $cascade, $callbacks);
}

What do you think? I think it’s nice