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Index Fast Full Scan…
Reads entire index
Uses multi-block reads
Useful when all data needed for query contained in index
- But column(s) cannot contain null
Consider index overloading
Does not return data in index sorted order
If CBO doesn’t choose, and you want to try
Notes:
Index fast full scans are a multi-block read on the index, and do not access the table. This access path is available when all data needed to satisfy the query is contained within the index. Hence, you might consider index overloading, i.e. adding a column or two to the index that is not logically required.
An important point to remember about index fast full scans is that the data is not returned in the order contained within the index. Add an ORDER BY clause to guarantee sort order if necessary – though you will see an extra sort step in the execution plan if you do.