The Data Warehouse Toolkit, 3rd Edition by Ralph Kimball & Margy Ross

Author:Ralph Kimball & Margy Ross
Language: eng
Format: epub
Publisher: John Wiley & Sons
Published: 2013-06-13T16:00:00+00:00

Controlling the performance of this query can be a challenge. A value band query is by definition very lightly constrained. The example report needed to scan the balances of more than 1 million accounts. Perhaps only the month dimension was constrained to the current month. Furthermore the funny joins to the value banding table are not the basis of a nice restricting constraint because they are grouping the 1 million balances. In this situation, you may need to place an index directly on the balance fact. The performance of a query that constrains or groups on the value of a fact-like balance will be improved enormously if the DBMS can efficiently sort and compress the individual fact. This approach was pioneered by the Sybase IQ columnar database product in the early 1990s and is now becoming a standard indexing option on several of the competing columnar DBMSs.

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