none
// Place this in function.php
function search_by_title( $search, $wp_query ) {
if ( ! empty( $search ) && ! empty( $wp_query->query_vars['search_terms'] ) ) {
global $wpdb;
$q = $wp_query->query_vars;
$n = ! empty( $q['exact'] ) ? '' : '%';
$search = array();
foreach ( ( array ) $q['search_terms'] as $term )
$search