Scanning an Index

The internet is full of information about indexes, and for a reason. Indexes in a database is probably the most important performance related topic. There are so many cases, properties, and different ways to use indexes that there is simply a lot to write about. In this post I’d like to talk about a specific use case that I’ve seen a few times, and is related to index scans and performance.

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The Problem with autotrace

There are few ways to see the execution plan of a SQL statement. One of these ways is the autotrace option in sqlplus. It is a very easy-to-use feature and people use it quite often. But there is a risk here. The autotrace option doesn’t always show you the correct execution plan.

Lately I prepared a demo and had a simple case that showed the incorrect info from autotrace, so here it is.

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Optimizer Changes After Upgrades

When Oracle releases a new version or even a petchset, sometimes they change the default value of initialization parameters or add new features and introducing new parameters with them. These changes affect the behavior of many components. In this post I’d like to address how I deal with parameter of features changing optimizer behavior. Continue reading