Oracle 19c Automatic Indexing: Data Skew Fixed By Baselines Part I (The...
In my previous few blog posts, I’ve been discussing some issues in relation to how Automatic Indexes handle SQL statements that accesses skewed data. In this post, I’m going to setup the scenario in...
View ArticleOracle 19c Automatic Indexing: Data Skew Fixed By Baselines Part II (Sound...
In my previous post, I discussed how the Automatic Indexing task by using Dynamic Sampling Level=11 can correctly determine the correct query cardinality estimates and assume the CBO will likewise...
View ArticleIndex FFS Cost
There are a number of unexpected issues with the optimizer’s treatment of the index fast full scan, the access path where Oracle ignores the structure of the B-tree and uses multiblock reads to do a...
View ArticleOracle 19c Automatic Indexing: Indexing With Stale Statistics Part I (Dead...
A “golden rule” when working with Automatic Indexing is that things don’t work properly if there are stale statistics on the dependant objects. Stale statistics can of course be problematic but they...
View ArticleIndex FFS Cost 2
Here’s a little puzzle, highlighting a “bug that’s not a bug” that was “fixed but not fixed” some time in the 10.2 timeline. (If you want specifics about exactly when the fix became available and what...
View ArticleOracle 19c Automatic Indexing: Indexing With Stale Statistics Part II (Survive)
In my previous post, I discussed how having stale statistics, usually a bad idea, is especially problematic with regard Automatic Indexes as it usually results in viable automatic indexes only...
View ArticleOracle 19c Automatic Indexing: Indexing With Stale Statistics Part III (Do...
In Part I of this series, we saw how Automatic Indexing will not create a viable Automatic Index if there are stale or missing statistics on the underlining segments. In Part II we saw how these SQL...
View ArticleInline Hint
If you’ve ever used subquery factoring (“with” subqueries or common table expressions (CTEs) as they are often called) then you’re probably aware of the (undocumented) hints /*+ materialize */ , which...
View ArticleInterval Oddity
Interval partitioning is a popular strategy for partitioning date-based data. It’s an enhanced variant of range partitioning that allows you to define a starting partition and an interval that should...
View ArticleOracle 19c Automatic Indexing: Indexing Partitioned Tables Part I...
In this little series, I’m going to discuss how Automatic Indexing works in relation to Partitioning. I’ve discussed Indexing and Partitioning many times previously and how Oracle has various options...
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