Merge mysql.com:/home/svoj/devel/mysql/BUG30590/mysql-4.1-engines

into  mysql.com:/home/svoj/devel/mysql/BUG30590/mysql-5.0-engines

3 files changed, 40 insertions, 3 deletions

diff --git a/heap/hp_delete.c b/heap/hp_delete.c
index 637e5f1a497..e5c8dfcef01 100644
--- a/heap/hp_delete.c
+++ b/heap/hp_delete.c
@@ -72,10 +72,7 @@ int hp_rb_delete_key(HP_INFO *info, register HP_KEYDEF *keyinfo,
   int res;
 
   if (flag) 
-  {
     info->last_pos= NULL; /* For heap_rnext/heap_rprev */
-    info->lastkey_len= 0;
-  }
 
   custom_arg.keyseg= keyinfo->seg;
   custom_arg.key_length= hp_rb_make_key(keyinfo, info->recbuf, record, recpos);
diff --git a/heap/hp_rfirst.c b/heap/hp_rfirst.c
index d1842949421..6acfe8e0ed6 100644
--- a/heap/hp_rfirst.c
+++ b/heap/hp_rfirst.c
@@ -35,6 +35,17 @@ int heap_rfirst(HP_INFO *info, byte *record, int inx)
 	     sizeof(byte*));
       info->current_ptr = pos;
       memcpy(record, pos, (size_t)share->reclength);
+      /*
+        If we're performing index_first on a table that was taken from
+        table cache, info->lastkey_len is initialized to previous query.
+        Thus we set info->lastkey_len to proper value for subsequent
+        heap_rnext() calls.
+        This is needed for DELETE queries only, otherwise this variable is
+        not used.
+        Note that the same workaround may be needed for heap_rlast(), but
+        for now heap_rlast() is never used for DELETE queries.
+      */
+      info->lastkey_len= 0;
       info->update = HA_STATE_AKTIV;
     }
     else
diff --git a/heap/hp_rnext.c b/heap/hp_rnext.c
index 3b436fe87aa..4ecbe779107 100644
--- a/heap/hp_rnext.c
+++ b/heap/hp_rnext.c
@@ -33,11 +33,40 @@ int heap_rnext(HP_INFO *info, byte *record)
     heap_rb_param custom_arg;
 
     if (info->last_pos)
+    {
+      /*
+        We enter this branch for non-DELETE queries after heap_rkey()
+        or heap_rfirst(). As last key position (info->last_pos) is available,
+        we only need to climb the tree using tree_search_next().
+      */
       pos = tree_search_next(&keyinfo->rb_tree, &info->last_pos,
                              offsetof(TREE_ELEMENT, left),
                              offsetof(TREE_ELEMENT, right));
+    }
+    else if (!info->lastkey_len)
+    {
+      /*
+        We enter this branch only for DELETE queries after heap_rfirst(). E.g.
+        DELETE FROM t1 WHERE a<10. As last key position is not available
+        (last key is removed by heap_delete()), we must restart search as it
+        is done in heap_rfirst().
+
+        It should be safe to handle this situation without this branch. That is
+        branch below should find smallest element in a tree as lastkey_len is
+        zero. tree_search_edge() is a kind of optimisation here as it should be
+        faster than tree_search_key().
+      */
+      pos= tree_search_edge(&keyinfo->rb_tree, info->parents,
+                            &info->last_pos, offsetof(TREE_ELEMENT, left));
+    }
     else
     {
+      /*
+        We enter this branch only for DELETE queries after heap_rkey(). E.g.
+        DELETE FROM t1 WHERE a=10. As last key position is not available
+        (last key is removed by heap_delete()), we must restart search as it
+        is done in heap_rkey().
+      */
       custom_arg.keyseg = keyinfo->seg;
       custom_arg.key_length = info->lastkey_len;
       custom_arg.search_flag = SEARCH_SAME | SEARCH_FIND;