+/**
+ * Update cache for thumbnails in the current loop
+ *
+ * @since 3.2
+ *
+ * @param object $wp_query Optional. A WP_Query instance. Defaults to the $wp_query global.
+ */
+function update_post_thumbnail_cache( $wp_query = null ) {
+ if ( ! $wp_query )
+ $wp_query = $GLOBALS['wp_query'];
+
+ if ( $wp_query->thumbnails_cached )
+ return;
+
+ $thumb_ids = array();
+ foreach ( $wp_query->posts as $post ) {
+ if ( $id = get_post_thumbnail_id( $post->ID ) )
+ $thumb_ids[] = $id;
+ }
+
+ if ( ! empty ( $thumb_ids ) ) {
+ _prime_post_caches( $thumb_ids, false, true );
+ }
+
+ $wp_query->thumbnails_cached = true;
+}
+