当使用集合执行magento sql时

Question

I am using Magento collection. I have a question about a filter. If I execute following PHP code, when does SQL get executed?

$xxx_collection = Mage::getModel('modulename/xxx')->getCollection();
$xxx_collection->getSelect()->limit($limit, $offset);
$xxx_collection->addFieldToFilter('user', $customerData->getId())->addFieldToFilter('xxx_id', 0);

The last line(filter code) will execute SQL? What about the second (limit code) line? If I don't use third line(addFieldToFilter), then the second line will execute SQL?

I am asking this question because I don't want my Magento to execute SQL twice. it will make overhead.

Answer 1

$xxx_collection->getSelect()->limit($limit, $offset);

The code in line 2 will not execute query. Collection object executes query only when its load() function is called. You can call load function just after preparing collection query or it will call internally load function when you use collection object in iterator function like in foreach loop.

Your code is fine, and not executing it twice.