posts_orderby not displaying the posts - sql

Question

I would like to customize my wordpress search page
First, i used the "posts_where" to modify the clause
function search_posts_where ($where) {
global $wp_query, $wpdb;
// Searching and not in admin
if (!is_admin() && $wp_query->is_search && isset($wp_query->query_vars['s'])) {
// Tables names
$post_title = "{$wpdb->prefix}posts.post_title";
$post_excerpt = "{$wpdb->prefix}posts.post_excerpt";
$post_content = "{$wpdb->prefix}posts.post_content";
$post_type = "{$wpdb->prefix}posts.post_type";
$post_status = "{$wpdb->prefix}posts.post_status";
$post_author = "{$wpdb->prefix}posts.post_author";
$post_ID = "{$wpdb->prefix}posts.ID";
$post_date = "{$wpdb->prefix}posts.post_date";
// Get the 's' parameters
$wp_query->query_vars['s'] ? $search_text = $wp_query->query_vars['s'] : $search_text = 'IS NULL';
// Write the where clause
$where = " AND ((($post_title LIKE '%$search_text%')";
$where .= " OR ($post_excerpt LIKE '%$search_text%')";
$where .= " OR ($post_content LIKE '%$search_text%')))";
$where .= " AND $post_type IN ('parcours')";
$where .= " AND $post_status = 'publish'";
$where .= " GROUP BY $post_ID";
}
return $where;
}
add_filter('posts_where', 'search_posts_where', 10, 2);
It works fine. All posts belonging to my custom post type 'parcours' are shown, depending on what I entered for the 's' query.
Second, i used the "posts_join" to add the meta table (not used yet !)
function search_posts_join ($join) {
global $wp_query, $wpdb;
// Searching and not in admin
if (!is_admin() && $wp_query->is_search && isset($wp_query->query_vars['s'])) {
// Tables names
$post_meta = "{$wpdb->prefix}postmeta";
$post_ID = "{$wpdb->prefix}posts.ID";
$post_meta_ID = "{$wpdb->prefix}postmeta.post_id";
// Join clause
$join .= "LEFT JOIN $post_meta ON ($post_ID = $post_meta_ID)";
}
return $join;
}
add_filter('posts_join', 'search_posts_join', 10, 2);
Still works perfectly !
Now the problem, i would like to order my posts in ascending direction (default is descending). So, i added the "posts_orderby" hook.
function search_posts_orderby ($orderby) {
global $wp_query, $wpdb;
// Searching and not in admin
if (!is_admin() && $wp_query->is_search) {
// Tables names
$post_title = "{$wpdb->prefix}posts.post_title";
$post_date = "{$wpdb->prefix}posts.post_date";
$post_ID = "{$wpdb->prefix}posts.ID";
// Order by clause
$orderby .= " ORDER BY $post_title ASC,";
$orderby .= " $post_date DESC";
}
return $orderby;
}
add_filter('posts_orderby', 'search_posts_orderby', 10, 2);
And here is the problem. All posts disapeared. Removing the "orderby" and they come back.
Looking at the SQL query, i have
"SELECT SQL_CALC_FOUND_ROWS wp_128444_posts.* FROM wp_128444_posts LEFT JOIN wp_128444_postmeta ON (wp_128444_posts.ID = wp_128444_postmeta.post_id) WHERE 1=1 AND (((wp_128444_posts.post_title LIKE '%tour%') OR (wp_128444_posts.post_excerpt LIKE '%tour%') OR (wp_128444_posts.post_content LIKE '%tour%'))) AND wp_128444_posts.post_type IN ('parcours') AND wp_128444_posts.post_status = 'publish' GROUP BY wp_128444_posts.ID ORDER BY wp_128444_posts.post_title LIKE '{5a35f6e9144541f93e08829126b2cb633436cebf95d774062fff749a12e6a465}tour{5a35f6e9144541f93e08829126b2cb633436cebf95d774062fff749a12e6a465}' DESC, wp_128444_posts.post_date DESC ORDER BY wp_128444_posts.post_title ASC, wp_128444_posts.post_date DESC LIMIT 0, 6"
I don't know why WP is adding the default ORDER BY, that i don't want.
Is is possible to remove it ?
I tried to replace my hook with "pre_get_posts" hook
function order_posts_by_title( $query ) {
if ( $query->is_search() && $query->is_main_query() ) {
$query->set( 'orderby', 'title' );
$query->set( 'order', 'ASC' );
}
}
add_action( 'pre_get_posts', 'order_posts_by_title' );
With this hook, it works !! Sounds very strange to me
Any explanation ?
Thanks