BUG#20389: Crash when using index scan in reverse order

mysql-test/r/partition_order.result:
  Changed a test case to handle ordered index scan reverse order as well
mysql-test/t/partition_order.test:
  Changed a test case to handle ordered index scan reverse order as well
sql/ha_myisam.cc:
  More debug info
sql/ha_partition.cc:
  Introduced partition_index_read_last to ensure we use index_read_last in those
  cases towards underlying handler.
  Ensured that index_read with HA_READ_PREFIX_LAST, HA_READ_PREFIX_LAST_OR_PREV and
  HA_READ_BEFORE_KEY uses ordered index scan in reverse order.
sql/ha_partition.h:
  Introduced partition_index_read_last to ensure we use index_read_last in those
  cases towards underlying handler.
  Ensured that index_read with HA_READ_PREFIX_LAST, HA_READ_PREFIX_LAST_OR_PREV and
  HA_READ_BEFORE_KEY uses ordered index scan in reverse order.

1 files changed, 3 insertions, 2 deletions

diff --git a/sql/ha_partition.h b/sql/ha_partition.h
index 4c627cd50f8..b838bc599f0 100644
--- a/sql/ha_partition.h
+++ b/sql/ha_partition.h
@@ -46,7 +46,8 @@ private:
     partition_index_read= 0,
     partition_index_first= 1,
     partition_index_last= 2,
-    partition_no_index_scan= 3
+    partition_index_read_last= 3,
+    partition_no_index_scan= 4
   };
   /* Data for the partition handler */
   int  m_mode;                          // Open mode
@@ -429,7 +430,7 @@ private:
       return (queue_buf(part_id) +
               PARTITION_BYTES_IN_POS);
     }
-  int handle_ordered_index_scan(byte * buf);
+  int handle_ordered_index_scan(byte * buf, bool reverse_order);
   int handle_ordered_next(byte * buf, bool next_same);
   int handle_ordered_prev(byte * buf);
   void return_top_record(byte * buf);