The Autonomous Data Warehouse Cloud (ADWC) is a self-configuring, fast, secure and scalable platform for data warehouses. Does this mean we don’t have to take care anymore about performance of our ETL processes? Which performance tips are still important for us, and where can we hand over the responsibility to ADWC? A revised version of an old blog post, with regard to Oracle’s Data Warehouse Cloud solution.
Optimizer statistics are essential for good execution plans and fast performance of the SQL queries. Of course, this is also the case in the Autonomous Data Warehouse Cloud. But the handling of gathering statistics is slightly different from what we know from other Oracle databases.
In Oracle Autonomous Data Warehouse Cloud, External Tables can be used to read files from the cloud-based Object Storage. But take care to do it the official way, otherwise you will see a surprise, but no data.
Since Oracle 12c, the query optimizer is able to change execution plans at runtime. This feature is called “Adaptive Plans”. Something similar happened on the ODTUG Community Service Day at the Kscope conference in Orlando.
Global temporary tables (or private temporary tables, if you use Oracle 18c) are a practical feature to be used for SQL queries with multiple steps, for example complex reports in a data warehouse. If you want to use them, some details must be considered.
Complex SQL statements are hard to understand – not only for us, but for the query optimizer, too. Sometimes, it is a good idea to write a simpler SQL query to do the same work. Here a nice story about a performance improvement by rewriting the SQL statement.
I just wanted to write a small demo script for Auto-List Partitioning in Oracle 12.2. Instead, I spent an entire evening finding a bug in the Oracle data dictionary. Fortunately, it’s not a dramatic one.