Ticket #41281: 41281.diff

src/wp-admin/includes/upgrade.php

@@ -2856 +2856 @@
                         maybe_convert_table_to_utf8mb4( $wpdb->termmeta );
                 }
         }
+
+        // Upgrade version prior to 4.9.
+        if ( $wp_current_db_version < 38591 ) {
+                $wpdb->query( "ALTER TABLE $wpdb->postmeta ADD INDEX meta_key_meta_value(meta_key(191), meta_value(64))" );
+        }
 }
 
 if ( !function_exists( 'install_global_terms' ) ) :

src/wp-includes/version.php

@@ -11 +11 @@
  *
  * @global int $wp_db_version
  */
-$wp_db_version = 38590;
+$wp_db_version = 38591;
 
 /**
  * Holds the TinyMCE version