Preparing my session on Online Statistics Gathering for ETL for the DOAG conference, I noticed some points that I didn’t covered in the previous two blog posts. The first point is showing the problem that may arise if indexes are involved. The second one is about partition exchange load and it completes the topic of partitioned tables started in part 2. No blog posting on Oracle products is nowadays complete without mentioning the cloud. The third point is about Autonomous Data Warehouse Cloud Service and Online Statistics Gathering improvements. Continue reading
Online Statistics Gathering has been introduced in 12c and is a very handy feature for ETL and batch jobs developers. However the devil is in the detail. There are some points to remember. Let’s take a closer look. Continue reading
One of the new query optimizations in 12c are the null-accepting semi-joins. They make subquery unnesting and a semi-join possible in a situation which led to FILTER operation in older versions. Continue reading
Actually, the CBO usually does a good job optimizing “NOT IN” subqueries. Unless something goes wrong. Recently it took a long time on a 10.2.0.5 database to search for the reason. At last looking in the CBO trace files (event 10053) has given the right hint.