Indexes are a powerful tool and technique in database querying and operations. They serve as a roadmap to quickly locate and retrieve data, improving the overall performance of database operations. In this Blog, we will explore some tips and tricks for effectively utilizing indexes in Oracle databases.

1.  One of the greatest advantages of indexes is their ability to enhance the performance of various types of database queries. Not only do they optimize select queries, but they also speed up updates and deletes. By indexing the appropriate columns, you can minimize the time required for data retrieval and manipulation.
2. Indexes also play a crucial role in enforcing referential integrity in database systems. When a child row is inserted or updated, the parent key must be verified. By placing an index on the column of the key in the parent table, the database can utilize the index to validate the child. Without an index, a full table scan of the parent table is necessary, resulting in slower performance.
3. While indexes offer significant benefits, finding the most efficient index can be a challenging task. Most indexes in Oracle databases are of the B-Tree type, which is the default. However, if our query involves a function in the WHERE clause, the database will not use a B-Tree index. For such scenarios, a Function-Based Index (FBI) is required. An FBI creates an index by applying the function to each value, allowing for direct comparisons with the function in the WHERE clause.
4. Bit map indexes are another type of index that utilizes the fast comparison capabilities of computer CPUs. By representing each value in the index as a bit, Oracle can quickly match values based on a mask. Bit map indexes are particularly effective in read-only environments and data warehouse implementations. However, they are not suitable for columns with high cardinality, as the width of the index increases with the number of distinct values.
5. Every index added to a database has a performance impact on INSERTs, UPDATEs, and DELETEs. When a table has multiple indexes, any changes to the table's data require updating all the associated indexes. Therefore, the decision to add indexes is a trade-off between SELECT performance and DML (Data Manipulation Language) operations. Having too many indexes can also slow down the performance of updates and inserts. On the other hand, too few indexes may lead to slower query execution. To optimize the use of indexes, it is essential to determine which indexes are not being used and to identify duplicate indexes that can be removed or modified.
6. Database administrators (DBAs) can employ various strategies to determine index usage and optimize the indexes in their systems. One approach is to locate all unused indexes and remove them, reducing the maintenance overhead. Additionally, identifying tables and indexes that can benefit from Function-Based Indexes (FBIs) can further enhance database performance. To find unused indexes, Oracle 8i users can examine the caches (Buffer Cache or Library Cache) to determine index usage. However, in Oracle 9i and 10g, it becomes easier to track unused indexes using the v$object_usage view, which updates the USED column when an index is first used.
 

Indexes are invaluable tools for optimizing the performance of database operations. They improve query execution, enforce referential integrity, and enhance overall system efficiency. However, finding the most efficient indexes and striking the right balance between SELECT performance and DML operations can be a complex task. By following the tips and tricks mentioned in this article, database administrators can unlock the full potential of indexes and maximize the performance of their Oracle databases.