An index fast full scan reads the entire index as it is i.e. as it exists on the disk. This index read is unsorted. This access path usage multiblock IO to perform the index scan. Index fast full scan simply reads all of the leaf, branch and root block of index quickly using multiblock IO Read more about Optimizer Access Paths : Fast Full Scan[…]
A production AWR report flagged a query with an INDEX FULL SCAN operation consuming significant I/O. The developer assumed it was an index range scan gone wrong. It was not. The optimizer had a reason — and understanding that reason is what separates reactive troubleshooting from deliberate tuning. This post breaks down what Oracle index Read more about Oracle Index Full Scan: How It Works and When the Optimizer Uses It[…]
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[…]
In this blog, we will explore what is the access path in the Oracle database. However, before moving to the access path, let’s first understand what is a row source. It is a set of rows that are returned in a step by execution plan. It can be a table or a result of join operations Read more about Optimizer Access Paths: How oracle database works[…]