What does backend Type Static mean in magento?

What does backend Type Static mean in magento? Posted on
January 28,201 1

By
Fangcaoyuan owner

About
A year ago, I noticed some category or product attributes, for example,
SKU, path, Etc., were given backend type "static" in class
Mage_catalog_model_resource_eav_mysql4_setup. But I failed to find out
What static meant here, or I did not know what the difference was
Between static and datetime/decimal/INT/text/varchar. All I knew
That time was if I gave my user defined attribute a "static" type,
Attribute values were stored in _ varchar table.

Recently, I dived deeper into magento EAV module. Now I can answer my question.

An entity can have some "static" attributes, whose values are stored
In Entity main table. Take SKU for example, SKU values are stored in
Catalog_product_entity table. Although SKU is varchar type, its values
Are not stored in catalog_product_entity_varchar. magento does not
Lookup catalog_product_entity_varchar for SKU values because in
Eav_attribute table, SKU backend type is defined as "static ".

It also explains why I can get SKU values without add it to select, but I can not do the same with non static attributes.

View Source
Print
?

1	$collection = Mage::getModel( 'catalog/product' )->getCollection();

2	echo $collection ->getFirstItem()->getSku();

It will output the SKU.

View Source
Print
?

1	$collection = Mage::getModel( 'catalog/product' )->getCollection();

2	echo $collection ->getFirstItem()->getName();

It will not output the name.

View Source
Print
?

1	$collection = Mage::getModel( 'catalog/product' )->getCollection()->addAttributeToSelect( 'name' );

2	echo $collection ->getFirstItem()->getName();

Calling addattributetoselect is a must to retrieve non static attribute values.

For user defined attributes of existing entity, if I do not change
The structure of main entity table, even I specify backend as "static"
In Entity setup class, magento has nowhere to store their values to
Fallback to _ varchar table.