Reindexing

Reindexing is the process of rebuilding one or more indexes to reflect updates to the underlying data and to improve retrieval performance. An index is a data structure that supports fast lookup and retrieval. Over time, as data changes, indexes can become fragmented, contain dead entries, or lose selectivity, reducing query efficiency. Reindexing updates or reconstructs the index to restore optimal performance and can also reclaim space.

Reindexing can be full or incremental. A full reindex rebuilds the index from scratch, potentially locking the table during the operation and consuming significant resources. Incremental or online approaches rebuild or refresh only parts of an index or do so without blocking read/write access, depending on the database system. Reindexing is common after bulk data loads, large deletions, schema changes, or index corruption.

In relational databases, common options include commands or operations that rebuild indexes; some systems offer online or concurrent reindexing to minimize downtime. In information retrieval and search systems, reindexing means reprocessing the entire corpus to construct or update the inverted index that supports query operations, often performed periodically or in response to substantial corpus changes.

Considerations when planning reindexing include potential impact on performance and availability, required disk space, and the risk of interruption. Best practices include testing in a staging environment, performing maintenance during low-traffic periods, and monitoring system load and index health. Alternatives include index maintenance operations such as reorganizing or defragmenting, updating statistics, or refreshing materialized views.