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Monthly Archives: January 2015

How to Replace a Bitmap Index

Posted on 25. January 2015 by Dani Schnider
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Bitmap indexes are typically used for columns with low cardinality, i.e. with a small number of distinct values. This is not always the best solution. The following use case describes a situation from a real-life project and explains why and how we replaced a bitmap index with a combination of virtual column and b-tree index.

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Posted in Oracle, Performance, SQL | Leave a reply

Avoid dbms_stats.auto_invalidate in ETL jobs

Posted on 6. January 2015 by Dani Schnider
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Recently I realized that the dbms_stats parameter no_invalidate is important for statistics gathering in ETL jobs. I never considered this parameter because “the default value will be good enough” – as for most other parameters of the statistics gathering procedures. But in this case, this is obviously not true.

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Posted in ETL, Oracle, Performance | 1 Reply

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