Tag: tag

Oracle Index Fast Full Scan — multiblock I/O across all leaf blocks, no table access

Oracle Index Fast Full Scan: When the Optimizer Reads the Entire Index

Posted on by Sanjeeva Kumar

Last Updated: June 2026Tested On: Oracle 19c Your AWR shows INDEX FAST FULL SCAN on a query that runs every 5 minutes. The index exists. The query looks fine. But something feels off — why is Oracle reading the entire index instead of doing a range scan? Sound familiar? This post explains exactly what Oracle Read more about Oracle Index Fast Full Scan: When the Optimizer Reads the Entire Index[…]

Oracle DISTINCT query execution path comparison showing full table scan versus index fast full scan optimization

Optimizer Access Paths: How Index FFS works with Distinct

Posted on by Sanjeeva Kumar

Distinct is the keyword that oracle used to filter out unique values from a column. However, it is very interesting to see the behavior followed by the optimizer for its access path. How Oracle Index Fast Full Scan Handles DISTINCT Queries? In this “Optimizer Access Paths” blog, we will see how we can make optimizer Read more about Optimizer Access Paths: How Index FFS works with Distinct[…]