Streetread Launches Full Drupal-powered Mobile Version

Glad to help..I'll explain: (sorry for the delay - didn't see your comment up here)

To have cron update feeds based on a percentage you have to alter aggregator.module's aggregator_cron(). I organized to code as follows:

if(module_exists('your module')) {
  //special code
}
else {
 //what was originally inside aggregator_cron()
}

Inside the 'special code' you want to first gather all of the available feeds from the DB, determine the amount that need to be updated, then simply update them

//Gather feeds - least updated first
$result = db_query('SELECT * FROM {aggregator_feed} ORDER BY checked');
//Determine the update amount - divides the total amount of feeds by a certain number that you can have configurable via the admin settings. The 4 represents 1/4, or 25%.
$update_amt = ceil(db_num_rows($result)/variable_get('your-modules-update-amount-setting', 4));
//Then simple iterate the feeds $update_amt times, updating the feeds via aggregator_refresh()

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To delete any items exceeding a certain number, can be done a number of ways. Basically after each feed is refreshed (the end of aggregator_refresh()), you should gather all of that feeds items from the DB ( {aggregator_item} ). You could gather them in order from oldest to youngest - check how many items there are - and if they exceed how many you want, gather all of the iid's into an array and use one DB call to remove all of them. Like I said, it can be done a number of ways depending on any other needs you have. I hope that explained it well. Let me know if you need any help with it, other options, more explaining, etc...

Does that help??