diff --git a/wp-includes/class-wp-query.php b/wp-includes/class-wp-query.php
index 3833a7a5a5..a52b5a484e 100644
--- a/wp-includes/class-wp-query.php
+++ b/wp-includes/class-wp-query.php
@@ -3179,36 +3179,36 @@ class WP_Query {
 				$cached_results = wp_cache_get( $cache_key, 'post-queries', false, $cache_found );
 
 				if ( $cached_results ) {
-					if ( 'ids' === $q['fields'] ) {
-						/** @var int[] */
-						$this->posts = array_map( 'intval', $cached_results['posts'] );
-					} else {
-						_prime_post_caches( $cached_results['posts'], $q['update_post_term_cache'], $q['update_post_meta_cache'] );
-						/** @var WP_Post[] */
-						$this->posts = array_map( 'get_post', $cached_results['posts'] );
-					}
+					/** @var int[] */
+					$post_ids = array_map( 'intval', $cached_results['posts'] );
 
-					$this->post_count    = count( $this->posts );
+					$this->post_count    = count( $post_ids );
 					$this->found_posts   = $cached_results['found_posts'];
 					$this->max_num_pages = $cached_results['max_num_pages'];
 
 					if ( 'ids' === $q['fields'] ) {
+						$this->posts = $post_ids;
+
 						return $this->posts;
 					} elseif ( 'id=>parent' === $q['fields'] ) {
+						_prime_post_parents_caches( $post_ids );
+
 						/** @var int[] */
-						$post_parents = array();
+						$post_parents = wp_cache_get_multiple( $post_ids, 'post_parent' );
 
-						foreach ( $this->posts as $key => $post ) {
+						foreach ( $post_parents as $id => $post_parent ) {
 							$obj              = new stdClass();
-							$obj->ID          = (int) $post->ID;
-							$obj->post_parent = (int) $post->post_parent;
+							$obj->ID          = (int) $id;
+							$obj->post_parent = (int) $post_parent;
 
-							$this->posts[ $key ] = $obj;
-
-							$post_parents[ $obj->ID ] = $obj->post_parent;
+							$this->posts[] = $obj;
 						}
 
 						return $post_parents;
+					} else {
+						_prime_post_caches( $post_ids, $q['update_post_term_cache'], $q['update_post_meta_cache'] );
+						/** @var WP_Post[] */
+						$this->posts = array_map( 'get_post', $post_ids );
 					}
 				}
 			}
@@ -3256,6 +3256,8 @@ class WP_Query {
 				$post_parents[ (int) $post->ID ] = (int) $post->post_parent;
 				$post_ids[]                      = (int) $post->ID;
 			}
+			// Prime post parent caches, so that on second run, there is not another database query.
+			wp_cache_add_multiple( $post_parents, 'post_parent' );
 
 			if ( $q['cache_results'] && $id_query_is_cacheable ) {
 				$cache_value = array(
diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 4b6bc14acf..bb799802ad 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -7169,7 +7169,7 @@ function _get_non_cached_ids( $object_ids, $cache_group ) {
 	$cache_values   = wp_cache_get_multiple( $object_ids, $cache_group );
 
 	foreach ( $cache_values as $id => $value ) {
-		if ( ! $value ) {
+		if ( false === $value ) {
 			$non_cached_ids[] = (int) $id;
 		}
 	}
diff --git a/wp-includes/post.php b/wp-includes/post.php
index 8a3bc56656..ea81bbd045 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -7262,6 +7262,7 @@ function clean_post_cache( $post ) {
 
 	wp_cache_delete( $post->ID, 'posts' );
 	wp_cache_delete( $post->ID, 'post_meta' );
+	wp_cache_delete( $post->ID, 'post_parent' );
 
 	clean_object_term_cache( $post->ID, $post->post_type );
 
@@ -7795,6 +7796,31 @@ function _prime_post_caches( $ids, $update_term_cache = true, $update_meta_cache
 	}
 }
 
+/**
+ * Prime post parent caches.
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param int[] $ids ID list.
+ */
+function _prime_post_parents_caches( array $ids ) {
+	global $wpdb;
+
+	$non_cached_ids = _get_non_cached_ids( $ids, 'post_parent' );
+	if ( ! empty( $non_cached_ids ) ) {
+		$fresh_posts = $wpdb->get_results( sprintf( "SELECT $wpdb->posts.ID, $wpdb->posts.post_parent FROM $wpdb->posts WHERE ID IN (%s)", implode( ',', $non_cached_ids ) ) );
+
+		if ( $fresh_posts ) {
+			$post_parent_data = array();
+			foreach ( $fresh_posts as $fresh_post ) {
+				$post_parent_data[ (int) $fresh_post->ID ] = (int) $fresh_post->post_parent;
+			}
+
+			wp_cache_add_multiple( $post_parent_data, 'post_parent' );
+		}
+	}
+}
+
 /**
  * Adds a suffix if any trashed posts have a given slug.
  *
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 4ad00b033e..57ce8593b6 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-beta1-56762';
+$wp_version = '6.4-beta1-56763';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.