From b98b347504a572a7685ad627f79df4e8e8903578 Mon Sep 17 00:00:00 2001
From: Peter Wilson <peterwilsoncc@git.wordpress.org>
Date: Sun, 16 Mar 2025 22:55:11 +0000
Subject: Query: Fix performance regression starting the loop for `all` fields.

Fixes a performance regression starting the loop after calling `WP_Query( [ 'fields' => 'all' ] )`. This changes how `WP_Query::the_post()` determines whether there is a need to traverse the posts for cache warming.

If IDs are queried, `WP_Query::$posts` is assumed to be an array of post IDs. If all fields are queried, `WP_Query::$posts` is assumed to be an array of fully populated post objects.

Follow up to [59919], [59937].

Props joemcgill, peterwilsoncc, SirLouen.
Fixes #56992.



git-svn-id: https://develop.svn.wordpress.org/trunk@59993 602fd350-edb4-49c9-b593-d223f7449a82
---
 tests/phpunit/tests/query/thePost.php | 84 ++++++++++++++++++++++++++++++++++-
 1 file changed, 82 insertions(+), 2 deletions(-)

(limited to 'tests')

diff --git a/tests/phpunit/tests/query/thePost.php b/tests/phpunit/tests/query/thePost.php
index e99a517872..6032a01dbe 100644
--- a/tests/phpunit/tests/query/thePost.php
+++ b/tests/phpunit/tests/query/thePost.php
@@ -48,6 +48,86 @@ class Tests_Query_ThePost extends WP_UnitTestCase {
 		}
 	}
 
+	/**
+	 * Ensure custom 'fields' values are respected.
+	 *
+	 * @ticket 56992
+	 */
+	public function test_wp_query_respects_custom_fields_values() {
+		global $wpdb;
+		add_filter(
+			'posts_fields',
+			function ( $fields, $query ) {
+				global $wpdb;
+
+				if ( $query->get( 'fields' ) === 'custom' ) {
+					$fields = "$wpdb->posts.ID,$wpdb->posts.post_author";
+				}
+
+				return $fields;
+			},
+			10,
+			2
+		);
+
+		$query = new WP_Query(
+			array(
+				'fields'    => 'custom',
+				'post_type' => 'page',
+				'post__in'  => self::$page_child_ids,
+			)
+		);
+
+		$this->assertNotEmpty( $query->posts, 'The query is expected to return results' );
+		$this->assertSame( $query->get( 'fields' ), 'custom', 'The WP_Query class is expected to use the custom fields value' );
+		$this->assertStringContainsString( "$wpdb->posts.ID,$wpdb->posts.post_author", $query->request, 'The database query is expected to use the custom fields value' );
+	}
+
+	/**
+	 * Ensure custom 'fields' populates the global post in the loop.
+	 *
+	 * @ticket 56992
+	 */
+	public function test_wp_query_with_custom_fields_value_populates_the_global_post() {
+		global $wpdb;
+		add_filter(
+			'posts_fields',
+			function ( $fields, $query ) {
+				global $wpdb;
+
+				if ( $query->get( 'fields' ) === 'custom' ) {
+					$fields = "$wpdb->posts.ID,$wpdb->posts.post_author";
+				}
+
+				return $fields;
+			},
+			10,
+			2
+		);
+
+		$query = new WP_Query(
+			array(
+				'fields'    => 'custom',
+				'post_type' => 'page',
+				'post__in'  => self::$page_child_ids,
+				'orderby'   => 'id',
+				'order'     => 'ASC',
+			)
+		);
+
+		$query->the_post();
+
+		// Get the global post and specific post.
+		$global_post   = get_post();
+		$specific_post = get_post( self::$page_child_ids[0], ARRAY_A );
+
+		$this->assertSameSetsWithIndex( $specific_post, $global_post->to_array(), 'The global post is expected to be fully populated.' );
+
+		$this->assertNotEmpty( get_the_title(), 'The title is expected to be populated.' );
+		$this->assertNotEmpty( get_the_content(), 'The content is expected to be populated.' );
+		$this->assertNotEmpty( get_the_excerpt(), 'The excerpt is expected to be populated.' );
+	}
+
 	/**
 	 * Ensure that a secondary loop populates the global post completely regardless of the fields parameter.
 	 *
@@ -75,11 +155,11 @@ class Tests_Query_ThePost extends WP_UnitTestCase {
 		$global_post   = get_post();
 		$specific_post = get_post( self::$page_child_ids[0], ARRAY_A );
 
+		$this->assertSameSetsWithIndex( $specific_post, $global_post->to_array(), 'The global post is expected to be fully populated.' );
+
 		$this->assertNotEmpty( get_the_title(), 'The title is expected to be populated.' );
 		$this->assertNotEmpty( get_the_content(), 'The content is expected to be populated.' );
 		$this->assertNotEmpty( get_the_excerpt(), 'The excerpt is expected to be populated.' );
-
-		$this->assertSameSetsWithIndex( $specific_post, $global_post->to_array(), 'The global post is expected to be fully populated.' );
 	}
 
 	/**
-- 
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