RSVPMaker Excerpt Shortcode

function rsvpmaker_excerpt ($atts)
{

$no_events = (isset($atts["no_events"]) && $atts["no_events"]) ? $atts["no_events"] : 'No events currently listed.';

global $post;
global $wp_query;
global $wpdb;

$backup = $wp_query;

add_filter('posts_join', 'rsvpmaker_join' );
add_filter('posts_where', 'rsvpmaker_where' );
add_filter('posts_groupby', 'rsvpmaker_groupby' );
add_filter('posts_orderby', 'rsvpmaker_orderby' );
add_filter('posts_distinct', 'rsvpmaker_distinct' );
remove_filter('the_content','event_content',5);

$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;

$querystring = "post_type=rsvpmaker&post_status=publish&paged=$paged";
if(isset($atts["type"]))
    $querystring .= "&rsvpmaker-type=".$atts["type"];
if(isset($atts["limit"]))
    $querystring .= "&posts_per_page=".$atts["limit"];
if(isset($atts["add_to_query"]))
    {
        if(!strpos($atts["add_to_query"],'&'))
            $atts["add_to_query"] = '&'.$atts["add_to_query"];
        $querystring .= $atts["add_to_query"];
    }

$wp_query = new WP_Query($querystring);

// clean up so this doesn't interfere with other operations
remove_filter('posts_join', 'rsvpmaker_join' );
remove_filter('posts_where', 'rsvpmaker_where' );
remove_filter('posts_groupby', 'rsvpmaker_groupby' );
remove_filter('posts_orderby', 'rsvpmaker_orderby' );
remove_filter('posts_distinct', 'rsvpmaker_distinct' );

ob_start();

if ( have_posts() ) {
while ( have_posts() ) : the_post();

$sql = "SELECT * FROM ".$wpdb->prefix."rsvp_dates WHERE postID=".$post->ID.' ORDER BY datetime';
$results = $wpdb->get_results($sql,ARRAY_A);
if($results)
{
$dateblock = '';
foreach($results as $row)
    {
    $t = strtotime($row["datetime"]);
    if(!empty($dateblock))
        $dateblock .= ', ';
    $dateblock .= date('F jS',$t);
    }
}
?>

<div id="post-<?php the_ID();?>" <?php post_class();?> >
<h3 class="entry-title"><a href="<?php the_permalink(); ?>" ><?php the_title(); echo ' - '.$dateblock; ?></span></a></h3>
<div class="entry-content">
<?php the_excerpt(); ?>
</div><!-- .entry-content -->
</div>
<?php
endwhile;
}
else
    echo "<p>$no_events</p>\n";
$wp_query = $backup;

add_filter('the_content','event_content',5);

wp_reset_postdata();

return ob_get_clean();

}

add_shortcode("rsvpmaker_excerpt","rsvpmaker_excerpt");