How to handle a failed Oracle index

When an Oracle index becomes ineffective, several approaches can be taken.

1. Rebuilding indexes: Use the ALTER INDEX… REBUILD command to rebuild any faulty indexes. This will delete the existing index and recreate a new one.
2. Recalculate the statistical information of the table by using the GATHER_TABLE_STATS procedure from the DBMS_STATS package. This will allow the optimizer to better choose indexes for query execution.
3. Adjust the query statement to fully utilize the index by optimizing it. Improving query performance can be achieved through methods such as adding query hints or rewriting the query.
4. Change the type of index: Depending on the specific situation, it may be possible to consider changing the type of index. For example, changing a B-tree index to a bitmap index, or using a function index.
5. Adding a new index: If there is no appropriate index available in the table, adding a new index can be considered to improve query performance. But be careful to avoid excessive indexing that may cause index invalidation.
6. If the issue of index failure is severe and cannot be resolved through other methods, it may be necessary to redesign the data model, including redesigning table structures, partitioned tables, and sharding.

It is important to note that index inefficiency may be caused by reasons such as uneven data distribution, unreasonable query statements, inaccurate statistics, etc. Therefore, when dealing with index inefficiency issues, it is necessary to comprehensively consider various factors and take corresponding measures based on specific circumstances.