INDEX FAST FULL SCAN
Short Description
Retrieval of all rowids (and column values) using multiblock reads. No sorting order can be defined. Compares to a full table scan on only the indexed columns.
Detailed Description​
If all the columns you need to access are in the supporting index, Oracle can use an INDEX FAST FULL SCAN to retrieve the data. A fast full scan accesses the data in the index itself, without accessing the table. It cannot be used to eliminate a sort operation, because the data is not ordered by the index key. It reads the entire index using multiblock reads, unlike a full index scan, and can be parallelized.
Further Reading​
- Oracle Magazine - How to read an execution plan
- Oracle Tuning Guide - Explaining and Displaying Execution Plans
- Oracle Tuning Guide - Comparing Execution Plans Tutorial
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