Get custom attributes to work with magento flat product catalog enabled

I need to get my custom attribute to work with Magento flat product 开发者_如何学Ccatalog.

• Attribute code: free_shipping
• Attribute type: Yes / No
• Used in Product Listing: Yes
• Use in Promo Conditions: Yes

I've refreshed the flat product catalog and all the indexes. Caching is disabled. My attribute fails to work in Shopping Cart Promotion Rules, whilst flat catalog is enabled. Any ideas?

You need to create a method that tells magento how to add your attribute to the flat tables in case it has a custom source model.

This article explains it in further detail: http://www.dconstructing.com/2012/03/14/custom-product-attributes-and-flat-database-tables-in-magento