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Oracle Data Warehouse Tuning for 10g
book

Oracle Data Warehouse Tuning for 10g

by Gavin JT Powell
April 2011
Intermediate to advanced content levelIntermediate to advanced
504 pages
16h 49m
English
Digital Press
Content preview from Oracle Data Warehouse Tuning for 10g
42 2.2 Methods for Tuning a Data Warehouse
There are a few more points to note about star transformation queries.
Even if you expect a star transformation to occur, even if you use the
STAR_TRANSFORMATION hint, the optimizer may not necessarily use
a star query. Why?
If a query accesses more than, say, 10% of a fact table’s rows, then the
optimizer automatically executes a full table scan of the fact table. A
query retrieving more than 10% of a table’s rows is automatically
faster reading the entire table, according to the optimizer.
In the past the use of a hint has only been a suggestion to the optimizer
and has not forced the optimizer to pick ...
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Publisher Resources

ISBN: 9781555583354