The search index manager is a supported plugin that will recreate the search_index
If you change a lot of page or after a release, the search index manager should be run to update/rebuild the index.
The search index is an index of your page that powers:
The index is updated 1) incrementally page by page when a visitor see a page.
The move plugin depends on it to retrieve the backlinks and make the corresponding rewrite
If you don't want to create broken links don't forget to rebuild your index if you have added pages externally (ie moved from an other installation via the file system, not via the web interface)
The combostrap index is a table in the SQLite database
On the Admin page, you can:
SELECT count(1) from pages;