Add WP-Cron cleanup for wp_sync_updates table

Schedule a daily cron job to delete sync update rows older than
1 day, preventing unbounded table growth from abandoned
collaborative editing sessions. The expiration is filterable
via the wp_sync_updates_expiration hook.

Author: josephfusco

src/wp-admin/admin.php

@@ -113,6 +113,11 @@
 	wp_schedule_event( time(), 'daily', 'delete_expired_transients' );
 }
 
+// Schedule sync updates cleanup.
+if ( ! wp_next_scheduled( 'wp_delete_old_sync_updates' ) && ! wp_installing() ) {
+	wp_schedule_event( time(), 'daily', 'wp_delete_old_sync_updates' );
+}
+
 set_screen_options();
 
 $date_format = __( 'F j, Y' );

src/wp-includes/collaboration.php

@@ -22,3 +22,34 @@ function wp_collaboration_inject_setting() {
 		);
 	}
 }
+
+/**
+ * Deletes sync updates older than 1 day from the wp_sync_updates table.
+ *
+ * Rows left behind by abandoned collaborative editing sessions are cleaned up
+ * to prevent unbounded table growth.
+ *
+ * @since 7.0.0
+ */
+function wp_delete_old_sync_updates() {
+	global $wpdb;
+
+	/**
+	 * Filters the lifetime, in seconds, of a sync update row.
+	 *
+	 * By default, the lifetime is 1 day. Once a row reaches that age, it will
+	 * automatically be deleted by a cron job.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param int $expiration The expiration age of a sync update row, in seconds.
+	 */
+	$expiration = apply_filters( 'wp_sync_updates_expiration', DAY_IN_SECONDS );
+
+	$wpdb->query(
+		$wpdb->prepare(
+			"DELETE FROM {$wpdb->sync_updates} WHERE created_at < %s",
+			gmdate( 'Y-m-d H:i:s', time() - $expiration )
+		)
+	);
+}

src/wp-includes/default-filters.php

@@ -454,6 +454,7 @@
 add_action( 'importer_scheduled_cleanup', 'wp_delete_attachment' );
 add_action( 'upgrader_scheduled_cleanup', 'wp_delete_attachment' );
 add_action( 'delete_expired_transients', 'delete_expired_transients' );
+add_action( 'wp_delete_old_sync_updates', 'wp_delete_old_sync_updates' );
 
 // Navigation menu actions.
 add_action( 'delete_post', '_wp_delete_post_menu_item' );