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Index Column Order

Oracle Database 19c Automatic Indexing: Default Index Column Order Part II (Future Legend)

In Part I, we explored some options that Oracle might adopt when ordering the columns within an Automatic Index by default, in the absence of other factors where there is only the one SQL statement to be concerned with. A point worth making is that if all columns of an index are specified within SQL […]

Oracle Database 19c Automatic Indexing: Default Index Column Order Part I (Anyway Anyhow Anywhere)

The next thing I was curious about regarding Automatic Indexing was in which order would Oracle by default order the columns within an index. This can be a crucial decision with respect to the effectiveness of the index (but then again, may not be so crucial as well). Certainly one would expect the index column […]

Index Column Order – Impact On Index Branch Blocks Part II (The Weeping Song)

In Part I, I discussed how the order of columns in an index makes no real difference to the effectiveness of the index if all columns are referenced via equality predicates. If the leading column has a high number of distinct columns, it might result in less necessary data within index branches as less data […]

Index Column Order – Impact On Index Branch Blocks Part I (Day-In Day-Out)

I recently replied on Twitter to some comments regarding an excellent blog post by Franck Pachot – Covering indexes in Oracle, and branch size, where I disagreed somewhat with one of the conclusions stated in the post: “ensure that selective columns appear as early as possible (without compromising the index access efficiency of course) in order to […]

Index Advanced Compression: Multi-Column Index Part II (Blow Out)

I previously discussed how Index Advanced Compression can automatically determine not only the correct number of columns to compress, but also the correct number of columns to compress within specific leaf blocks of the index. However, this doesn’t mean we can just order the columns within the index without due consideration from a “compression” perspective. As […]