Articles tagged Indexes

Problems with Indexes

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In my book “Cost Based Oracle – Fundamentals” (Apress 2005) I described a problem with the cost calculation for the index fast full scan: When you generate statistics for a table, one of the results is the number of blocks below the high water mark. When you generate the statistics for an index, you get the number of leaf blocks… Continue Reading →Read more

Investigating Indexes – 2

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In an earlier article on investigating indexes I described some methods for looking at the internal structure of an index to get an idea of its current state of health. Although this type of knowledge helps you to make informed decisions about which indexes might need special treatment (like being permanently dropped, perhaps) it doesn’t immediately answer questions like: “what’s… Continue Reading →Read more

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… Continue Reading →Read more

Introduction to SQL Server Filtered Indexes

SQL Server filtered indexes can save space and improve performance if they are used properly. Under what circumstances can they be used? When are they most effective, and what sort of performance gain or space-saving is likely? How does a filtered index affect the choice of execution plan? Seth explores these questions with practical experiments… Read more

Exceptional PowerShell DBA Pt 3 – Collation and Fragmentation

In this final look into his everyday essentials, Laerte Junior provides some useful scripts for the DBA that use an alternative way of error-logging. He shows how to use a PowerShell script to check and, if necessary, to defragment your indexes, write data to a SQL Server table, and change the collation for a table. Being an exceptional DBA just got a little easier.… Read more