Agregados 3

1. Using Aggregates
Ing. Julio Ernesto Carreño Vargas

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.
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3. Which Tables to Use?
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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”
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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”
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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.
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7. Requirements for the Aggregate
Navigator
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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.
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9. REQUIREMENTS FOR THE AGGREGATE
NAVIGATOR
 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.
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10. REQUIREMENTS FOR THE AGGREGATE
NAVIGATOR
 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.
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11. Bibliografía
 Mastering Data Warehouse Aggregates.Solutions for Star
Schema Performance. Christopher Adamson.
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