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Oracle 19c Automatic Indexing: Indexing With Stale Statistics Part III (Do Anything You Say)

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 statements effectively become blacklisted and when segment statistics are subsequently collected, Automatic Indexing will still not create viable […]

Oracle 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 being created in an UNUSABLE/INVISIBLE state. If we were to now to collect the missing statistics:   If we now repeatedly re-run the […]

Oracle 19c Automatic Indexing: Data Skew Fixed By Baselines Part II (Sound And Vision)

  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 determine the correct cardinality estimate and NOT use an index if it would cause performance to regress. However, if other database sessions DON’T use […]

Oracle 19c Automatic Indexing: Data Skew Fixed By Baselines Part I (The Prettiest Star))

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 which Automatic Indexing can potentially use Baselines to help address some of these issues. BUT, as we’ll see, I’m having to […]

Oracle 19c Automatic Indexing: Data Skew Part III (The Good Son)

  I’m going to expand just a tad on my previous posts on data skew and run a simple query that returns a few rows based on a column predicate AND another query on the same column that returns many rows. The following table has a CODE column as with previous posts with the data […]

Oracle 19c Automatic Indexing: Data Skew Part II (Everything’s Alright)

In my previous post, I discussed an example with data skew, in which the Automatic Indexing process created a new index, but somehow the CBO when using the index estimated the correct cardinality estimate even though no histograms were explicitly calculated. In this post I’ll answer HOW this achieved by the CBO. Get some idea […]

METHOD_OPT=> SIZE AUTO Quiz Solution (The Trickster)

I was going to leave it for a few days but there have already been so many comments and discussions on all this, I thought I better write something up. In case anyone was wondering, yes I probably am driving my colleagues at work mad with my “Question of the Day” !! Unfortunately, some might [...]

METHOD_OPT => SIZE AUTO Quiz (Automatic For The People)

OK, a nice, easy, simple one today. No tricks, honest You have a table with 3 columns and lets say 1M rows. Column 1 is effectively unique, so it has 1M distinct values. Let’s say 1 – 1000000, not that it really matters. Column 2 has 254 distinct values, all evenly distributed so it has [...]