From 090fb72df03b8154ff0cb3fe430d0fd3f38c14b2 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov.ru@gmail.com>
Date: Wed, 13 Aug 2025 16:28:31 +0000
Subject: [PATCH] Export: Split the query for post authors in
 `wxr_authors_list()` into smaller chunks.

This aims to avoid a fatal error when attempting to export content on larger WP instances with a lot of data.

Follow-up to [15961], [28731].

Props bor0, SirLouen, SergeyBiryukov.
Fixes #63503.
Built from https://develop.svn.wordpress.org/trunk@60632


git-svn-id: http://core.svn.wordpress.org/trunk@59968 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-admin/includes/export.php | 19 +++++++++++++------
 wp-includes/version.php      |  2 +-
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/wp-admin/includes/export.php b/wp-admin/includes/export.php
index 566c9d802b..9d5903a98c 100644
--- a/wp-admin/includes/export.php
+++ b/wp-admin/includes/export.php
@@ -405,19 +405,26 @@ function export_wp( $args = array() ) {
 		global $wpdb;
 
 		if ( ! empty( $post_ids ) ) {
-			$post_ids = array_map( 'absint', $post_ids );
-			$and      = 'AND ID IN ( ' . implode( ', ', $post_ids ) . ')';
+			$post_ids       = array_map( 'absint', $post_ids );
+			$post_id_chunks = array_chunk( $post_ids, 20 );
 		} else {
-			$and = '';
+			$post_id_chunks = array( array() );
 		}
 
 		$authors = array();
-		$results = $wpdb->get_results( "SELECT DISTINCT post_author FROM $wpdb->posts WHERE post_status != 'auto-draft' $and" );
-		foreach ( (array) $results as $result ) {
-			$authors[] = get_userdata( $result->post_author );
+
+		foreach ( $post_id_chunks as $next_posts ) {
+			$and = ! empty( $next_posts ) ? 'AND ID IN (' . implode( ', ', $next_posts ) . ')' : '';
+
+			$results = $wpdb->get_results( "SELECT DISTINCT post_author FROM $wpdb->posts WHERE post_status != 'auto-draft' $and" );
+
+			foreach ( (array) $results as $result ) {
+				$authors[] = get_userdata( $result->post_author );
+			}
 		}
 
 		$authors = array_filter( $authors );
+		$authors = array_unique( $authors, SORT_REGULAR ); // Remove duplicate authors.
 
 		foreach ( $authors as $author ) {
 			echo "\t<wp:author>";
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 2da1dbadd0..6f1582113c 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.9-alpha-60631';
+$wp_version = '6.9-alpha-60632';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.