make it clear for optimizer that XOR's are not optimizable at the moment (BUG#992)

mysql-test/r/func_test.result

@@ -46,6 +46,11 @@ select 3 ^ 11, 1 ^ 1, 1 ^ 0, 1 ^ NULL, NULL ^ 1;
 select 1 XOR 1, 1 XOR 0, 0 XOR 1, 0 XOR 0, NULL XOR 1, 1 XOR NULL, 0 XOR NULL;
 1 XOR 1	1 XOR 0	0 XOR 1	0 XOR 0	NULL XOR 1	1 XOR NULL	0 XOR NULL
 0	1	1	0	NULL	NULL	NULL
+create table t1 (a int);
+insert t1 values (1);
+select * from t1 where 1 xor 1;
+a
+drop table t1;
 select 5 between 0 and 10 between 0 and 1,(5 between 0 and 10) between 0 and 1;
 5 between 0 and 10 between 0 and 1	(5 between 0 and 10) between 0 and 1
 0	1

mysql-test/t/func_test.test

@@ -18,6 +18,11 @@ select -1.49 or -1.49,0.6 or 0.6;
 select 3 ^ 11, 1 ^ 1, 1 ^ 0, 1 ^ NULL, NULL ^ 1;
 select 1 XOR 1, 1 XOR 0, 0 XOR 1, 0 XOR 0, NULL XOR 1, 1 XOR NULL, 0 XOR NULL;
 
+create table t1 (a int);
+insert t1 values (1);
+select * from t1 where 1 xor 1;
+drop table t1;
+
 #
 # Wrong usage of functions
 #

sql/item_cmpfunc.h

@@ -634,12 +634,18 @@ inline Item *and_conds(Item *a,Item *b)
   return cond;
 }
 
+/*
+  XOR is Item_cond, not an Item_int_func bevause we could like to
+  optimize (a XOR b) later on. It's low prio, though
+*/
 class Item_cond_xor :public Item_cond
 {
 public:
   Item_cond_xor() :Item_cond() {}
   Item_cond_xor(Item *i1,Item *i2) :Item_cond(i1,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"; }
 };