Agreggates iii

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Agreggates iii

  1. 1. Using AggregatesIng. Julio Ernesto Carreño Vargas
  2. 2. Using Aggregates the proper use of aggregates introduces a new set of requirements for the data warehouse architecture. Mechanisms must be in place to ensure that the most appropriate table is used to respond to every warehouse query. 2
  3. 3. Which Tables to Use?3
  4. 4. The Schema Design Dimensionally designed aggregates can answer a question if all facts and dimensions required by the question are present in the aggregate. “Order dollars by month for 2006” 4
  5. 5. Relative Size Use the relative number of rows in each aggregate fact table or pre-joined aggregate to estimate the performance ranking of each option. “Order dollars by month for 2006” 5
  6. 6. Aggregate Portfolio and Availability Aggregates should be chosen each time a query is run. This allows consideration of availability status and accommodates a changing portfolio of aggregates. 6
  7. 7. Requirements for the Aggregate Navigator7
  8. 8. aggregate navigator Evaluating schema design, table size, and availability can be confusing for an end user. And since these evaluations should be made each time a query is run, how is a query to be saved in a report? The aggregate navigator solves these problems. 8
  9. 9. REQUIREMENTS FOR THE AGGREGATENAVIGATOR The aggregate navigator should permit users and applications to deal with the base schema only. The aggregate navigator should support aggregate star schemas (including aggregate dimensions) and pre-joined aggregates. It should not require changes to the base schema design. The aggregate navigator should be able to identify all necessary information automatically, through examination of the database catalog. This includes aggregate families, conformance, and relative table size. 9
  10. 10. REQUIREMENTS FOR THE AGGREGATENAVIGATOR The aggregate navigator translates base-schema SQL into aggregate-aware SQL at runtime. This process is transparent to the applications that issue SQL queries. The aggregate navigator should respond to the dynamic availability of aggregates. The aggregate navigator should facilitate easy addition and removal of aggregates from the data warehouse. A single aggregate navigator should service all front-end applications. A single aggregate navigation system should service all back-end databases. 10
  11. 11. Bibliografía Mastering Data Warehouse Aggregates.Solutions for Star Schema Performance. Christopher Adamson. 11

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