merge of bug #37830 to 5.1

1 files changed, 24 insertions, 5 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 9b094474216..068c8c0e402 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -12508,6 +12508,9 @@ part_of_refkey(TABLE *table,Field *field)
   @note
     used_key_parts is set to correct key parts used if return value != 0
     (On other cases, used_key_part may be changed)
+    Note that the value may actually be greater than the number of index 
+    key parts. This can happen for storage engines that have the primary 
+    key parts as a suffix for every secondary key.
 
   @retval
     1   key is ok.
@@ -12580,11 +12583,27 @@ static int test_if_order_by_key(ORDER *order, TABLE *table, uint idx,
     reverse=flag;				// Remember if reverse
     key_part++;
   }
-  *used_key_parts= on_primary_key ? table->key_info[idx].key_parts :
-    (uint) (key_part - table->key_info[idx].key_part);
-  if (reverse == -1 && !(table->file->index_flags(idx, *used_key_parts-1, 1) &
-                         HA_READ_PREV))
-    reverse= 0;                                 // Index can't be used
+  if (on_primary_key)
+  {
+    uint used_key_parts_secondary= table->key_info[idx].key_parts;
+    uint used_key_parts_pk=
+      (uint) (key_part - table->key_info[table->s->primary_key].key_part);
+    *used_key_parts= used_key_parts_pk + used_key_parts_secondary;
+
+    if (reverse == -1 &&
+        (!(table->file->index_flags(idx, used_key_parts_secondary - 1, 1) &
+           HA_READ_PREV) ||
+         !(table->file->index_flags(table->s->primary_key,
+                                    used_key_parts_pk - 1, 1) & HA_READ_PREV)))
+      reverse= 0;                               // Index can't be used
+  }
+  else
+  {
+    *used_key_parts= (uint) (key_part - table->key_info[idx].key_part);
+    if (reverse == -1 && 
+        !(table->file->index_flags(idx, *used_key_parts-1, 1) & HA_READ_PREV))
+      reverse= 0;                               // Index can't be used
+  }
   DBUG_RETURN(reverse);
 }