WP_Query and pre_get_posts WordPress

dimadin answers:

I wasn't aware of this before, but you can't use tax query where you want to search for posts that don't have any term from some taxonomy (your second limitation) with any other tax query. Reason for this are some complicated SQL queries that are made with this.

That mean that the only other way is to have two separate queries and to merge results of them when you modify main query so that you are searching only from selected post IDs.

Problem with this is that you don't want to filter 'pre_get_posts' in those two new queries because you'll end with infinity loops.

This is the reason why I used class object to limit use of 'pre_get_posts' filter only for those queries that need it.

That is how I ended up with this solution which was tested and worked for me. Yes, it creates more database requests but it is the only solution I am aware of right now that uses your approach with modifying main query. Maybe some caching can improve it, which I could show example if you want.


class MD_Custom_Home_Loop {
/**
* Should 'pre_get_posts' filter be used.
*
* @access protected
*
* @var bool
*/
protected $no_pre_get_posts = false;

/**
* Add hooks.
*
* @access public
*/
public function __construct() {
add_action( 'pre_get_posts', array( $this, 'pre_get_posts' ) );
}

/**
* Modify query on home page.
*
* @access public
*
* @param WP_Query $query The WP_Query instance (passed by reference).
*/
public function pre_get_posts( &$query ) {
if ( ! is_admin() && !$query->is_singular() /* && $query->is_main_query() */ && ! $this->no_pre_get_posts ) {
if ( is_home() && $query->is_main_query() ) {
// Only query againt this post types
$query->set( 'post_type', array( 'post', 'wpgdacces_acces', 'page' ) );
}

// Only query againt post IDs from custom loop
$query->set( 'post__in', $this->get_ids() );

// Use 'pre_get_posts' filter in the future again
$this->no_pre_get_posts = false;
}
}

/**
* Get IDs of posts in custom home page loop.
*
* @access protected
*
* @return array $ids An array of post IDs for custom loop.
*/
protected function get_ids() {
// Don't use 'pre_get_posts' filter
$this->no_pre_get_posts = true;

// Create basic parameters
$query_one_args = $query_two_args = array(
'post_type' => array( 'post', 'page', 'wpgdacces_acces' ),
'fields' => 'ids',
);

// Add tax query for the first parameter
$query_one_args['tax_query'] = array(
'relation' => 'AND',
array(
'taxonomy' => 'category',
'field' => 'slug',
'terms' => array( 'private' ),
'operator' => 'IN'
),
array(
'taxonomy' => 'post_tag',
'field' => 'slug',
'terms' => array( 'private' ),
'operator' => 'IN'
),
);

// Get first query post IDs
$query_one = get_posts( $query_one_args );

// Add tax query for the second parameter
$query_two_args['tax_query'] = array(
'relation' => 'AND',
array(
'taxonomy' => 'category',
'field' => 'slug',
'operator' => 'NOT EXISTS'
),
array(
'taxonomy' => 'post_tag',
'field' => 'slug',
'operator' => 'NOT EXISTS'
),
);

// Get second query post IDs
$query_two = get_posts( $query_two_args );

// Merge those IDs and get only unique from them
$ids = array_unique( array_merge( $query_one, $query_two ) );

return $ids;
}
}
new MD_Custom_Home_Loop;


---

---

---