Fix sticky posts in WordPress. Deals with issues in trac #27282

fix-wp-stickies.php

/**
 * Provide a flag for whether or not the request really wanted ignore sticky
 * posts.
 */
add_filter( 'query_vars', function( $v ) {
	$v[] = 'really_ignore_sticky_posts';

	return $v;
} );

/**
 * Yes, always ignore sticky posts, but save the requested value in
 * really_ignore_sticky_posts query var
 */
add_filter( 'parse_query', function( $query ) {
	// But do you really mean it, paw?
	$query->query_vars['really_ignore_sticky_posts'] = isset( $query->query_vars['ignore_sticky_posts'] ) && $query->query_vars['ignore_sticky_posts'];
	$query->query_vars['ignore_sticky_posts'] = true;
} );

/**
 * Manipulate query to have sticky posts function correctly without adding to
 * the original post results.
 */
add_filter( 'posts_clauses', function( $clauses, $query ) {
	global $wpdb;

	if( !$query->query_vars['post__in'] && $query->is_home && !$query->query_vars['really_ignore_sticky_posts'] ) {
		$sticky_posts = get_option('sticky_posts');

		// Grab only published sticky posts of our desired post type(s)
		$stickies_query = new WP_Query( array(
			'post__in' => $sticky_posts,
			'post_type' => $query->query_vars['post_type'],
			'post_status' => 'publish',
			'fields' => 'ids',
			'posts_per_page' => count( $sticky_posts )
		) );

		$queried_stickies = $stickies_query->posts;

		if( !empty( $queried_stickies ) ) {
			$post__in_sticky = implode(',', array_map( 'absint', $queried_stickies ) );
			$clauses['where'] = "AND ((1=1 " . $clauses['where'] . ") OR {$wpdb->posts}.ID IN ($post__in_sticky))";
			$sticky_orderby = "FIELD( {$wpdb->posts}.ID, $post__in_sticky ) DESC";

			if( $clauses['orderby'] ) {
				$clauses['orderby'] = $sticky_orderby . ', ' . $clauses['orderby'];
			}
			else {
				$clauses['orderby'] = $sticky_orderby;
			}
		}
	}

	return $clauses;
}, 10, 2 );

Fixes issues with sticky posts as described in trac ticket https://core.trac.wordpress.org/ticket/27282

Hey Benjamin,

I think there might be a bug - if I don't have any sticky posts, I'll get an error (memory exhausted).
Any ideias?

So, not sure if this is the best/an actual fix, but I made sure there were sticky posts and the issue resolved:

if( !$query->query_vars['post__in'] && $query->is_home && get_option('sticky_posts' && !$query->query_vars['really_ignore_sticky_posts'] )

Thanks!