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direct mode

Statistics on Load

One of the talks I gave recently on the Groundbreaker Yatra tour was on the changes that arrive with the optimizer when you move to 12c and above. We talked about changes to histograms, all of the adaptive features etc, but also, one of the simplest but coolest optimizer improvements when it comes to loading data. When you perform a direct-path insert into an empty table, or a create-table-as-select (CTAS) operation, there is no need to perform an additional DBMS_STATS call to gather statistics at the conclusion of the load. The load process itself handles that for you. Here’s a simple example of that in action

Partition loading in direct mode

Direct mode insert using the APPEND hint is a cool piece of technology that lets you load bulk data into a table very quickly and efficiently. Obviously there are a number of implications of doing so which you can read about here, but the one that catches most people out is the that you are locking the table during the load and once the load is completed, the table is “disabled” until the transaction ends. Here’s a quick example of that in action: