The most computationally expensive part of searching is score calculation. It may take several seconds for large result sets (tens of thousands of hits).
Zend_Search_Lucene gives the possibility to limit result set size
with getResultSetLimit() and
setResultSetLimit() methods:
<?php
$currentResultSetLimit = Zend_Search_Lucene::getResultSetLimit();
Zend_Search_Lucene::setResultSetLimit($newLimit);
The default value of 0 means 'no limit'.
It doesn't give the 'best N' results, but only the 'first N' [11].