 <p>The essential difference is that Special:SMWAdmin only ''queues'' the updates in the <a href="https://www.mediawiki.org/wiki/Manual:Job_queue" rel="nofollow">job queue</a>, while <code>rebuildData.php</code> actually <em>performs</em> the updates.</p> <p>If your job queue is correctly configured, the difference may be trivial; otherwise you'll run into <a href="https://www.mediawiki.org/wiki/Manual:Job_queue#Performance_issue" rel="nofollow">performance issues</a>. A common error is to <a href="https://phabricator.wikimedia.org/T60969" rel="nofollow">have insufficient memory</a> for the job runner. If all else fails, the last resort is <a href="https://github.com/SemanticMediaWiki/SemanticMediaWiki/issues/184#issuecomment-34790596" rel="nofollow">null-editing all the pages</a>.</p> <p>The difference was actually written in the help page, but in a weird English; <a href="https://semantic-mediawiki.org/w/index.php?title=Help%3ARebuildData.php&amp;diff=39897&amp;oldid=39582" rel="nofollow">fixed that too</a>.</p>