Articles tagged Optimization

26 October 2022
26 October 2022

Oracle optimizer Or Expansion Transformations

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The previous installment of this series examined aggregate subquery removal and subquery coalescing, describing the latter as similar in some ways to an inverse for “Or Expansion” and “Join Factorization”. In this instalment, it’s time to take a closer look at Or Expansion and we’ll move on to Join Factorization in the next instalment.… Read more
03 October 2016
03 October 2016

Hacking Indexes

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Indexes are expensive to maintain so we want to get the greatest benefit we can from them and make sure that Oracle uses them whenever it’s appropriate. Sometimes, though, the optimizer seems to ignore indexes that we think would be very effective and when this happens it’s often because the statistics that Oracle has gathered do not reflect the quality… Read more
30 January 2012
30 January 2012

How to Document and Configure SQL Server Instance Settings

Occasionally, when you install identical databases on two different SQL Server instances, they will behave in surprisingly different ways. Why? Most likely, it is down to different configuration settings. There are around seventy of these settings and the DBA needs to be aware of the effect that many of them have. Brad McGehee explains them all in enough detail to help with most common configuration problems, and suggests some best practices.… Read more