>>This discusses how rather than why.
>>How does reindexing affect performance ?
>
>I've never really seen it improve performance to reindex as long as everything's working fine, but that's me. I'm sure there are folks who have.
>

Rebuilding indexes from scratch can have a major impact in overall throughput in situations where a significant part of the tag must be accessed to solve a query condition; defragmentation of the file, and removal of bloat do make significant performance improvements, especially in situations with large files and lots of tags. I strongly advise -never- reindexing; instead, completely rebuild the indexes from scratch using DELETE TAG ALL - INDEX...TAG so that everyting is rebult fromscratch in sequential fashion, minimizing the amount of interleaving of one tag's data structures with another's.