I know 8.1 brought some multipass aggregation functionality to the table (http://community.tableausoftware.com/ideas/1942), but I haven't seen anyone talk specifically about Multipass SQL. Is this because it would only apply to live connections? It could address some of the performance problems I've seen mentio@n of related to multipass workarounds.
Multipass SQL: Query capability supported by some data access tools in which the results of separate star-schema queries are combined column by column via the conformed dimensions. Not the same thing as a union, which is a row-by-row combination of separate queries. (definition from Our Own Knowledge Bank: Glossary of Datawarehousing Terms)
For example, take Day Sales Inventory (DSI):
The days' sales in inventory tells you the average number of days that it took to sell the average inventory held during the specified one-year period. You can also think of it as the number of days of sales that was held in inventory during the specified year. The calculation of the days' sales in inventory is: the number of days in a year (365 or 360 days) divided by the inventory turnover ratio.
For example, if a company had an inventory turnover ratio of 9, the company's inventory turned over 9 times during the year. If we use 360 as the number of days in the year, the company had (on average) 40 days of inventory on hand during the year (360 days divided by the inventory turnover ratio of 9).
To calculate this ratio, we would need to run a query against a Sales Fact table for the numerator and a separate query against an Inventory Fact table for the denominator.