我用下面的函数为每个作者显示一篇文章，效果很好，但是否可以按自定义字段排序？

<?php
add_filter(\'posts_groupby\', \'author_groupby\');
function author_groupby($groupby)
{
 global $wpdb;
 $author_groupby = "{$wpdb->posts}.post_author";
    if(preg_match("/$author_groupby/", $groupby)) {
    // grouping we need is already there
    return $groupby;
  }
  if(strlen(trim($groupby) == 0)) {
    // groupby was empty, use ours
    return $author_groupby;
  }
  return "$groupby, $author_groupby";
}

...
$author_groupby = "{$wpdb->posts}.post_author 
AND pm.meta_key = \'KEY\' 
ORDER BY pm.meta_value DESC Limit 0,1";
...