Which feature is enabled by default for all SQL statements in Autonomous Data Warehouse?

The feature that is enabled by default for all SQL statements in Autonomous Data Warehouse is the Result Cache. This feature is designed to improve the performance of SQL queries by storing the results of executed SQL statements in memory. When a query is executed, the result is cached, and if the same query is run again, the database can return the cached results instead of re-executing the query, which saves processing time and resources.

The use of the Result Cache contributes significantly to efficiency, especially in environments where queries are frequently repeated, as it reduces the amount of computation and input/output necessary to produce results. This default behavior enhances the overall performance of data retrieval operations in Autonomous Data Warehouse, making it a valuable feature for users looking for quick query responses.

In contrast, other options such as Optimizer Hints, Parallel DML, and Data Compression may provide performance enhancements but are not enabled by default for all SQL statements in the same manner as the Result Cache. Optimizer Hints require explicit specification by the user to influence the execution plan, Parallel DML involves user control over when to utilize parallel processing, and Data Compression may be applied based on specific storage settings, rather than being a universal default for all SQL operations.