Bloat in indexes is a situation where space within the index pages is not used efficiently. This can happen due to frequent updates or deletes of rows in the associated table, which can lead to dead tuples in indexes, similar to table bloat. Bloat in indexes is undesirable for several reasons:

1. Wasted Disk Space: Unused space within the index represents wasted storage that could be used more efficiently.

2. Performance Degradation: With increased bloat, the index becomes larger and less dense. This can degrade the performance of index scans because more disk I/O may be required to traverse the index.

3. Memory Inefficiency: Larger indexes require more memory to cache effectively. If the index bloat is severe, it can lead to reduced cache efficiency and increased cache churn.

4. Longer Maintenance Tasks: Bigger indexes take more time to process during maintenance tasks such as vacuuming, backups, and restores.

To address index bloat, you may indeed need to periodically perform reindexing or use the VACUUM command:

• REINDEX: This command rebuilds an index to remove bloat. This is usually a heavy operation because it requires an exclusive lock on the index being rebuilt, which can interfere with the regular operation of a database. Reindexing can be done less frequently and usually during maintenance windows.

• VACUUM (FULL): This command can also reduce bloat, but it is a heavy operation that requires an exclusive lock on the table being vacuumed.

• VACUUM: The regular VACUUM command can help to prevent bloat, as it marks space that has been freed up by updates and deletes as reusable. However, VACUUM does not return space to the filesystem unless used with the FULL option.

Index bloat should be monitored, and whether or not to perform reindexing should depend on the level of bloat and its impact on performance. For large databases with serious performance requirements, there are tools available (like pg_repack) that can rebuild indexes with less impact on database availability.

As always, any maintenance operation, including reindexing, should be thoroughly tested on a non-production environment to assess its impact and ensure it operates as expected before being performed on a production system.

Would you like to perform an analysis to determine if reindexing is necessary for a specific Postgres database? If so, please provide details about the database and the observed index bloat issues.