Backport of patch for bug#40003 from 6.0 to 5.1,

related to the backport of the patch for bug#38719

sql/ha_partition.cc:
  bug#40003, archive does not handle dup_key.

mysql-test/t/innodb_bug42419.test

@@ -3,6 +3,7 @@
 # Bug#42419 Server crash with "Pure virtual method called" on two concurrent connections
 #
 
+--source include/not_embedded.inc
 --source include/have_innodb.inc
 
 let $innodb_lock_wait_timeout= query_get_value(SHOW VARIABLES LIKE 'innodb_lock_wait_timeout%', Value, 1);

sql/ha_partition.cc

@@ -4928,10 +4928,11 @@ int ha_partition::info(uint flag)
       This flag is used to get index number of the unique index that
       reported duplicate key
       We will report the errkey on the last handler used and ignore the rest
+      Note: all engines does not support HA_STATUS_ERRKEY, so set errkey.
     */
+    file->errkey= errkey;
     file->info(HA_STATUS_ERRKEY);
-    if (file->errkey != (uint) -1)
-      errkey= file->errkey;
+    errkey= file->errkey;
   }
   if (flag & HA_STATUS_TIME)
   {