What is the difference of addAttributeToFilter() Vs addFieldToFilter()?

Question

I'm bit of confused what is the difference of addAttributeToFilter() and addFieldToFilter() functions. I checked the core files in magento. But I could not figured out a clear idea. Because for some of the collections in magento has used addAttributeToFilter() and some have used addFieldToFilter(). Please any clarification on this would be a great help. Thanks in advance.

Answer 1

addAttributeToFilter() is used to filter EAV collections.

addFieldToFilter() is used to filter Non-EAV collections.

EAV-models are for example product, customer, sales, etc so you can use use addAttributeToFilter() for those entities.

addFieldToFilter() is mapped to addAttributeToFilter() for EAV entities. So you can just use addFieldToFiler().

Edit:

You can have a look in app/code/core/Mage/Eav/Model/Entity/Collection/Abstract.php where the Mapping is done:

public function addFieldToFilter($attribute, $condition = null) {
    return $this->addAttributeToFilter($attribute, $condition);
}

Answer 2

With regards to EAV there is no difference.

/app/code/core/Mage/Eav/Model/Entity/Collection/Abstract.php
public function addFieldToFilter($attribute, $condition = null)
{
    return $this->addAttributeToFilter($attribute, $condition);
}

My assumption, though I could be wrong, is that for EAV they use the attribute naming as each attribute to filter on is in itself a stand alone item that has its own settings etc. Where as when not using EAV it is just another column on a database table and so the name Field works well.