What are the different types of indexes in Oracle?

When it comes to Oracle databases, there are several types of indexes that can be used to improve query performance. Some of the key types of indexes in Oracle include:

1. B-tree Indexes: B-tree indexes are the most common type of index in Oracle and are well-suited for querying single columns efficiently.
2. Bitmap Indexes: Bitmap indexes are ideal for columns with low cardinality and are particularly useful for data warehousing applications.
3. Reverse Key Indexes: Reverse key indexes can be helpful in reducing index contention and hotspots in high-concurrency systems.
4. Function-Based Indexes: Function-based indexes allow indexing on the result of a function or expression, providing additional flexibility in query optimization.

Overall, understanding the different types of indexes available in Oracle and selecting the appropriate index type based on the specific requirements of the database and queries can significantly enhance performance.