Filter collection value from another value from another index

Question

I create a custom attribute last_sync for customer custom attribute, i need to filter it if this attribute is null OR greater than created_at, right now i'm using code like this:

$collections = Mage::getModel('customer/customer')->getCollection()
        ->addAttributeToSelect('*');

foreach ($collections as $collection)
{
  $result = array();
  $result = $collection->getData();
  if(is_null($result['last_sync']) || ($result['last_sync'] < $result['updated_at']))
  {  
     $results[] = $result;
  }
}
return $results;

the problem for the above code is the speed time, because i have to loop through each customer data than filter it

Answer 1

You can try

$collections = Mage::getModel('customer/customer')->getCollection()
    ->addAttributeToSelect('*')
    ->addFieldToFilter('last_sync', array(
        array('null' => true),
        array('lt' => new Zend_Db_Expr('updated_at'))
    ));

or

$collections = Mage::getModel('customer/customer')->getCollection()
    ->addAttributeToSelect('*');

$collections->getSelect()->where(
    "(last_sync IS NULL) OR (last_sync < updated_at)"
);

It will also be faster if you only selected the attributes that you actually want to use.