In Magento 1, Inventory information is stored in a Stock Item object. Each Stock Item object is associated with a product object. Magento persists Stock Item objects to the cataloginventory_stock_item table.
However, each Stock Item object has a related Stock Status object. Stock Status appears to be an (index|cache|de-normalized) table that stores a product's stock status as in integer constant, and allows you to associate multiple stock items and products with a different website_id. Magento persists stock status objects to the cataloginventory_stock_status. The class constants and table schema for this are below.
class Mage_CatalogInventory_Model_Stock_Status extends Mage_Core_Model_Abstract
{
const STATUS_OUT_OF_STOCK = 0;
const STATUS_IN_STOCK = 1;
}
mysql> describe cataloginventory_stock_status;
+--------------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+----------------------+------+-----+---------+-------+
| product_id | int(10) unsigned | NO | PRI | NULL | |
| website_id | smallint(5) unsigned | NO | PRI | NULL | |
| stock_id | smallint(5) unsigned | NO | PRI | NULL | |
| qty | decimal(12,4) | NO | | 0.0000 | |
| stock_status | smallint(5) unsigned | NO | | NULL | |
+--------------+----------------------+------+-----+---------+-------+
5 rows in set (0.01 sec)
However, for reasons that aren't entirely clear, there is also a qty column in this table.
What is the relationship between these two qty columns?
Which is the source of truth for qty and which is the indexed/cached value? Is the value in stock_status simply a cached version of what's in the stock item table? Or is there a way to configure Magento to manage stock on a website level? Or is the relationship something other than what I've described?
