WP archives order by custom meta key - php

Question

in Wordpress template's function.php following code is working well
// Function accepting current query
function my_change_order( $query ) {
// Check if the query is for an archive
if($query->is_archive())
// Query was for archive, then set order
$query->set( 'order' , 'asc' );
// Return the query (else there's no more query, oops!)
return $query;
}
// Runs before the posts are fetched
add_filter( 'pre_get_posts' , 'my_change_order' );
But i need to order articles by custom meta key like _my_meta_vip. Based on this answer i tried following lines, with half success, because only load articles with defined custom meta key, others are missing. How can i solve that?
function my_change_order( $query ) {
if($query->is_archive())
$query->set( 'orderby' , 'meta_value' );
$query->set( 'meta_key' , '_my_meta_vip' );
return $query;
}
add_filter( 'pre_get_posts' , 'my_change_order' );
How can i order my articles by custom meta key properly?

Answer 1

function my_change_order( $query ) {
// Check if the query is for an archive
if($query->is_archive())
// Query was for archive, then set order
$query->set( 'order' , 'asc' );
$query->set( 'meta_query', array(
array(
'key' => '_my_meta_vip'
)
));
// Return the query (else there's no more query, oops!)
return $query;
}
look at the following topic: https://wordpress.stackexchange.com/questions/20237/using-meta-query-how-can-i-filter-by-a-custom-field-and-order-by-another-one may give you a clear idea

Answer 2

Finally can't find any way to list all post with and without _my_meta_VIP defined.
In my solution all _my_meta_VIP was filled with enabled or disabled and the following code do the job:
// Function accepting current query
function my_change_order( $query ) {
// Check if the query is for an archive
if($query->is_archive()) {
// Query was for archive, then set order
$query->set( 'post_type', 'profile' );
$query->set( 'orderby' , 'meta_value' );
$query->set( 'meta_key' , '_my_meta_vip' );
$query->set( 'order', 'DESC' );
} else {
// Return the original query for non-archive pages
return $query;
}
// Return the query
return $query;
}
// Runs before the posts are fetched
add_filter( 'pre_get_posts' , 'my_change_order' );

Answer 3

It looks like the underlying issue here is that the query is doing an inner join on the posts and postmeta tables, which is why posts that don't have that particular post meta entry aren't being returned by the query. What you want is a left join. See this answer for an explanation of the difference.
You should be able to use the posts_join filter to replace the inner join with a left join:
add_filter('posts_join', function($join) {
global $wpdb;
// Replace inner join with left join
$search = 'INNER JOIN ' . $wpdb->postmeta;
$replace = 'LEFT JOIN ' . $wpdb->postmeta;
$join = str_ireplace($search, $replace, $join);
return $join;
});