Manual:$wgDisableSearchUpdate/de-formal

Details
If you've disabled search semi-permanently, this also disables updates to the table. If you ever re-enable, be sure to rebuild the search table using.

The table gets populated when edits are saved. This may slow down your wiki if it gets a high rate of edits. You can disable search updates with this setting, and periodically run to update it during off-peak hours.