What are the principles of Oracle index optimization?

Principles for optimizing Oracle indexes include the following:

1. Choose the appropriate index type: Oracle supports various index types, such as B-tree index, bitmap index, function index, etc. Select the suitable index type based on specific query requirements and data characteristics.
2. Choose appropriate index columns: selecting columns that are frequently used in the query conditions as index columns can improve query efficiency. Avoid selecting columns with a large number of duplicate values as index columns, as this will result in poor indexing performance.
3. The order of indexed columns in a composite index is crucial. Place the columns that are frequently used together in query conditions at the beginning to better utilize the ordered nature of the index.
4. The size of the index can also affect query performance. If the index is too large, it will increase disk IO overhead. If the index is too small, it may not cover the query conditions. The size of the index should be determined based on the specific situation and storage limitations of the database.
5. Avoid excessive indexing: Having too many indexes will increase maintenance costs and decrease update performance. It is important to carefully select indexes based on query requirements and data characteristics to avoid excessive indexing.
6. Regular maintenance and rebuilding of indexes is important to improve query performance as indexes can become fragmented over time.
7. Monitor the usage of indexes: Use performance monitoring tools provided by Oracle to monitor how indexes are being used, and adjust index strategies promptly to improve query performance.