wordpress.org/plugins/search-regex/

$posts   = $wpdb->get_results ( "SELECT ID, post_content, post_title FROM {$wpdb->posts} WHERE post_status != 'inherit' AND post_type IN ('post','page') ORDER BY ID $orderby" );

if ( $limit > 0 )
    $sql .= $wpdb->prepare( " LIMIT %d,%d", $offset, $limit );

if (count ($posts) > 0)
{
    foreach ($posts AS $post)
    {
        if (($matches = $this->matches ($pattern, $post->post_content, $post->ID)))
        {
            foreach ($matches AS $match)
                $match->title = $post->post_title;

            $results = array_merge ($results, $matches);
        }
    }
}

/*
from http://wordpress.org/support/topic/limit-to-doesnt-work http://daisukeblog.com/?p=2149 change to /path/to/wordpress/wp-conent/plugins/search-regex/searches/post_content.php
 */
$posts   = $wpdb->get_results ( $wpdb->prepare("SELECT ID, post_content, post_title FROM {$wpdb->posts} WHERE post_status != 'inherit' AND post_type IN ('post','page') ORDER BY ID $orderby") );

if (count ($posts) > 0)
{
    $hit = 0;

    foreach ($posts AS $post)
    {
        if (($matches = $this->matches ($pattern, $post->post_content, $post->ID)))
        {
        ++$hit;
            foreach ($matches AS $match)
                $match->title = $post->post_title;

                $results = array_merge ($results, $matches);
        }
        if($limit>0&&$hit>=$limit)
        {
            break;
        }
    }
}