In this module we covered some of the advanced Oracle execution plan techniques that rely on specialized indexing.
The main points of this module include:
- Bitmapped indexes provide very fast access to table rows when used with low cardinality columns.
- A STAR query requires a single concatenated index on the FACT table.
- STAR queries work similar to hash joins in Oracle, building a hash table in the shared pool.
- The STAR transformation method creates ROWID lists in temporary segments.
- The STAR transformation is faster than the STAR query in cases where there are few rows returned by the sub-queries.
- A concatenated index is used whenever the high-order keys are present in the queries.