Less array walking required.

Author: peterwilsoncc

src/wp-includes/class-wp-query.php

@@ -3743,20 +3743,23 @@ public function the_post() {
 				// Full post objects queried.
 				$post_objects = $this->posts;
 			} else {
-				// Only partial objects queried, need to prime the cache for the loop.
-				$post_ids = array_reduce(
-					$this->posts,
-					function ( $carry, $post ) {
-						if ( 'ids' === $this->query_vars['fields'] ) {
-							$carry[] = $post;
-						} elseif ( isset( $post->ID ) ) {
-							$carry[] = $post->ID;
-						}
+				if ( 'ids' === $this->query_vars['fields'] ) {
+					// Post IDs queried.
+					$post_ids = $this->posts;
+				} else {
+					// Only partial objects queried, need to prime the cache for the loop.
+					$post_ids = array_reduce(
+						$this->posts,
+						function ( $carry, $post ) {
+							if ( isset( $post->ID ) ) {
+								$carry[] = $post->ID;
+							}
 
-						return $carry;
-					},
-					array()
-				);
+							return $carry;
+						},
+						array()
+					);
+				}
 				_prime_post_caches( $post_ids, $this->query_vars['update_post_term_cache'], $this->query_vars['update_post_meta_cache'] );
 				$post_objects = array_map( 'get_post', $post_ids );
 			}