Order by meta_key in custom post type doesn’t affect the query

I’m trying to query custom posts ordering by a meta_key. But after WP_Query running, there isn’t any change in sql query inside the order clause.

    $args = array(
    'post_type'   => 'event',
    'post_status' => 'publish',

    'meta_key' => '_start_eventtimestamp',
    'orderby' => 'meta_value_datetime',
    'order' => 'ASC',

    'meta_query' => array(
        array(
            'key' => '_start_eventtimestamp',
            'value' => date('Ymd'),
            'compare' => '>='
        )
    ),

    'posts_per_page' => '7',
    );

    $event_query = new WP_Query( $args );

And when I get the generated query I got this:

    SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts
     INNER JOIN wp_postmeta ON ( wp_posts.ID = wp_postmeta.post_id )
     INNER JOIN wp_postmeta AS mt1 ON ( wp_posts.ID = mt1.post_id )
     WHERE 1=1 AND ( wp_postmeta.meta_key = '_start_eventtimestamp'
     AND ( ( mt1.meta_key = '_start_eventtimestamp' AND mt1.meta_value >= '20160930' ) ) )
     AND wp_posts.post_type = 'event' AND ((wp_posts.post_status = 'publish'))
     GROUP BY wp_posts.ID ORDER BY wp_posts.menu_order ASC LIMIT 0, 7

The order clause suffered no change.
Is there wrong in my script of order by meta_key?

• This topic was modified 8 years, 5 months ago by rafael.