CLONE - LP #1285365: Bug query optimizer when multiple conditions are included in ON section

**Reported in Launchpad by Jared Kipe last update 25-08-2014 09:25:32

Basically a query with a left join, and conditions keep any index from being used, thus resulting in terrible performance.

https://gist.github.com/jaredkipe/4b752bd4ceca710e5839

Rewriting the query (from Magento in /app/code/core/Mage/Catalog/Model/Resource/Category/Flat.php ) resulted in a 710ms -> 10ms response reduction on that query.