Apply Jorgen Loland's fix: Bug#45221: Query "SELECT pk FROM C WHERE pk IN (SELECT int_key)" failing

XOR conditions are not optimized, and Item_cond_xor therefore
acts like type Func_item even though it inherits from Item_cond.
A subtle difference between Item_func and Item_cond is that
you can get the children Items from the former by calling
arguments(), and from the latter by calling argument_list().
However, since Item_cond_xor inherits from Item_cond,
arguments() did not return any Items.

The fact that Item_cond_xor::arguments() did not return it's
children items lead to a problem for make_cond_for_index();
the method accepted that XOR items on unindexed columns were
pushed using ICP. ICP evaluation of non-indexed columns
does not (and should not) work.

The fix for this bug is to make Item_cond_xor return it's
children items when the arguments() method is used. This makes
Item_cond_xor behave more like Item_func and in turn allows
make_cond_for_index() to discover any conflicting children
Items.

This is a temporary fix and should be removed when Item_cond_xor
 is optimized.

1 files changed, 22 insertions, 2 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index d093cf613f8..f01b4d6cab1 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -1715,14 +1715,34 @@ inline bool is_cond_or(Item *item)
 class Item_cond_xor :public Item_cond
 {
 public:
-  Item_cond_xor() :Item_cond() {}
-  Item_cond_xor(Item *i1,Item *i2) :Item_cond(i1,i2) {}
+  Item_cond_xor(Item *i1,Item *i2) :Item_cond(i1,i2) 
+  {
+    /* 
+      Items must be stored in args[] as well because this Item_cond is
+      treated as a FUNC_ITEM (see type()). I.e., users of it will get
+      it's children by calling arguments(), not argument_list(). This
+      is a temporary solution until XOR is optimized and treated like
+      a full Item_cond citizen.
+     */
+    arg_count= 2;
+    args= tmp_arg;
+    args[0]= i1; 
+    args[1]= i2;
+  }
   enum Functype functype() const { return COND_XOR_FUNC; }
   /* TODO: remove the next line when implementing XOR optimization */
   enum Type type() const { return FUNC_ITEM; }
   longlong val_int();
   const char *func_name() const { return "xor"; }
   void top_level_item() {}
+  /* Since child Items are stored in args[], Items cannot be added.
+     However, since Item_cond_xor is treated as a FUNC_ITEM (see
+     type()), the methods below should never be called. 
+  */
+  bool add(Item *item) { DBUG_ASSERT(FALSE); return FALSE; }
+  bool add_at_head(Item *item) { DBUG_ASSERT(FALSE); return FALSE; }
+  bool add_at_head(List<Item> *nlist) { DBUG_ASSERT(FALSE); return FALSE; }
+  void copy_andor_arguments(THD *thd, Item_cond *item) { DBUG_ASSERT(FALSE); }
 };