Port of code for: (part of testcase is in mysql-test/t/subquery*.test and will be ported separately)

Bug#11766642: crash in Item_field::register_field_in_read_map 
              with view

(Former 59793)

Prior to the refactoring in this patch, Item_cond_xor behaved 
partially as an Item_cond and partially as an Item_func. The
reasoning behind this was that XOR is currently not optimized
(thus should be Item_func instead of Item_cond), but it was 
planned optimize it in the future (thus, made Item_cond anyway 
to ease optimization later). 

Even though Item_cond inherits from Item_func, there are 
differences between these two. One difference is that the 
arguments are stored differently. Item_cond stores them in a 
list while Item_func store them in an args[]. 

BUG no 45221 was caused by Item_cond_xor storing arguments in 
the list while users of the objects would look for them in 
args[]. The fix back then was to store the arguments in both 
locations.

In this bug, Item_cond_xor initially gets two Item_field 
arguments. These are stored in the list inherited from 
Item_cond and in args[] inherited from Item_func. During
resolution, find_field_in_view() replaces the Item_fields 
stored in the list with Item_direct_view_refs, but args[] 
still points to the unresolved Item_fields. This shows that 
the fix for 45221 was incorrect.

The refactoring performed in this patch removes the confusion
by making the XOR item an Item_func period. A neg_transformer() 
is also implemented for Item_func_xor to improve performance 
when negating XOR expressions. An XOR is negated by negating 
one of the operands.

6 files changed, 197 insertions, 51 deletions

diff --git a/mysql-test/r/negation_elimination.result b/mysql-test/r/negation_elimination.result
index dea0d865d87..acb0fd18214 100644
--- a/mysql-test/r/negation_elimination.result
+++ b/mysql-test/r/negation_elimination.result
@@ -375,6 +375,121 @@ a
 13
 14
 15
+# XOR (Note: XOR is negated by negating one of the operands)
+# Should return 6,7
+SELECT * FROM t1 WHERE ((a > 5) XOR (a > 7));
+a
+6
+7
+# Should return 0..5,8..19
+SELECT * FROM t1 WHERE ((NOT (a > 5)) XOR (a > 7));
+a
+0
+1
+2
+3
+4
+5
+8
+9
+10
+11
+12
+13
+14
+15
+16
+17
+18
+19
+SELECT * FROM t1 WHERE ((a > 5) XOR (NOT (a > 7)));
+a
+0
+1
+2
+3
+4
+5
+8
+9
+10
+11
+12
+13
+14
+15
+16
+17
+18
+19
+SELECT * FROM t1 WHERE NOT ((a > 5) XOR (a > 7));
+a
+0
+1
+2
+3
+4
+5
+8
+9
+10
+11
+12
+13
+14
+15
+16
+17
+18
+19
+# Should return 6,7
+SELECT * FROM t1 WHERE NOT ((NOT (a > 5)) XOR (a > 7));
+a
+6
+7
+SELECT * FROM t1 WHERE NOT ((a > 5) XOR (NOT (a > 7)));
+a
+6
+7
+# Should return 0..5,8..19
+SELECT * FROM t1 WHERE NOT ((NOT (a > 5)) XOR (NOT (a > 7)));
+a
+0
+1
+2
+3
+4
+5
+8
+9
+10
+11
+12
+13
+14
+15
+16
+17
+18
+19
+# Should have empty result
+SELECT * FROM t1 WHERE (NULL XOR (a > 7));
+a
+SELECT * FROM t1 WHERE NOT (NULL XOR (a > 7));
+a
+# Should be simplified to "...WHERE (a XOR a)
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE NOT ((NOT a) XOR (a));
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	index	NULL	a	5	NULL	21	100.00	Using where; Using index
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` xor `test`.`t1`.`a`)
+# Should be simplified to "...WHERE (a XOR a)
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE NOT (a XOR (NOT a));
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	index	NULL	a	5	NULL	21	100.00	Using where; Using index
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` xor `test`.`t1`.`a`)
+# End XOR
 delete from t1 where a > 3;
 select a, not(not(a)) from t1;
 a	not(not(a))
diff --git a/mysql-test/t/negation_elimination.test b/mysql-test/t/negation_elimination.test
index 0e0d8891e1f..312be8ccdb4 100644
--- a/mysql-test/t/negation_elimination.test
+++ b/mysql-test/t/negation_elimination.test
@@ -65,6 +65,35 @@ select * from t1 where not((a < 5 and a < 10) and (not(a > 16) or a > 17));
 explain select * from t1 where ((a between 5 and 15) and (not(a like 10)));
 select * from t1 where ((a between 5 and 15) and (not(a like 10)));
 
+--echo # XOR (Note: XOR is negated by negating one of the operands)
+
+--echo # Should return 6,7
+SELECT * FROM t1 WHERE ((a > 5) XOR (a > 7));
+
+--echo # Should return 0..5,8..19
+SELECT * FROM t1 WHERE ((NOT (a > 5)) XOR (a > 7));
+SELECT * FROM t1 WHERE ((a > 5) XOR (NOT (a > 7)));
+SELECT * FROM t1 WHERE NOT ((a > 5) XOR (a > 7));
+
+--echo # Should return 6,7
+SELECT * FROM t1 WHERE NOT ((NOT (a > 5)) XOR (a > 7));
+SELECT * FROM t1 WHERE NOT ((a > 5) XOR (NOT (a > 7)));
+
+--echo # Should return 0..5,8..19
+SELECT * FROM t1 WHERE NOT ((NOT (a > 5)) XOR (NOT (a > 7)));
+
+--echo # Should have empty result
+SELECT * FROM t1 WHERE (NULL XOR (a > 7));
+SELECT * FROM t1 WHERE NOT (NULL XOR (a > 7));
+
+--echo # Should be simplified to "...WHERE (a XOR a)
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE NOT ((NOT a) XOR (a));
+
+--echo # Should be simplified to "...WHERE (a XOR a)
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE NOT (a XOR (NOT a));
+
+--echo # End XOR
+
 delete from t1 where a > 3;
 select a, not(not(a)) from t1;
 explain extended select a, not(not(a)), not(a <= 2 and not(a)), not(a not like "1"), not (a not in (1,2)), not(a != 2) from t1 where not(not(a)) having not(not(a));
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 346ae243196..74a63337e49 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -5065,23 +5065,21 @@ bool Item_func_like::turboBM_matches(const char* text, int text_len) const
     very fast to use.
 */
 
-longlong Item_cond_xor::val_int()
+longlong Item_func_xor::val_int()
 {
   DBUG_ASSERT(fixed == 1);
-  List_iterator<Item> li(list);
-  Item *item;
-  int result=0;	
-  null_value=0;
-  while ((item=li++))
+  int result= 0;
+  null_value= false;
+  for (uint i= 0; i < arg_count; i++)
   {
-    result^= (item->val_int() != 0);
-    if (item->null_value)
+    result^= (args[i]->val_int() != 0);
+    if (args[i]->null_value)
     {
-      null_value=1;
+      null_value= true;
       return 0;
     }
   }
-  return (longlong) result;
+  return result;
 }
 
 /**
@@ -5122,6 +5120,33 @@ Item *Item_bool_rowready_func2::neg_transformer(THD *thd)
   return item;
 }
 
+/**
+  XOR can be negated by negating one of the operands:
+
+  NOT (a XOR b)  => (NOT a) XOR b
+                 => a       XOR (NOT b)
+
+  @param thd     Thread handle
+  @return        New negated item
+*/
+Item *Item_func_xor::neg_transformer(THD *thd)
+{
+  Item *neg_operand;
+  Item_func_xor *new_item;
+  if ((neg_operand= args[0]->neg_transformer(thd)))
+    // args[0] has neg_tranformer
+    new_item= new(thd->mem_root) Item_func_xor(neg_operand, args[1]);
+  else if ((neg_operand= args[1]->neg_transformer(thd)))
+    // args[1] has neg_tranformer
+    new_item= new(thd->mem_root) Item_func_xor(args[0], neg_operand);
+  else
+  {
+    neg_operand= new(thd->mem_root) Item_func_not(args[0]);
+    new_item= new(thd->mem_root) Item_func_xor(neg_operand, args[1]);
+  }
+  return new_item;
+}
+
 
 /**
   a IS NULL  ->  a IS NOT NULL.
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index e587ffd0771..29107e944f5 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -391,6 +391,22 @@ public:
   }
 };
 
+/**
+  XOR inherits from Item_bool_func2 because it is not optimized yet.
+  Later, when XOR is optimized, it needs to inherit from
+  Item_cond instead. See WL#5800. 
+*/
+class Item_func_xor :public Item_bool_func2
+{
+public:
+  Item_func_xor(Item *i1, Item *i2) :Item_bool_func2(i1, i2) {}
+  enum Functype functype() const { return XOR_FUNC; }
+  const char *func_name() const { return "xor"; }
+  longlong val_int();
+  void top_level_item() {}
+  Item *neg_transformer(THD *thd);
+};
+
 class Item_func_not :public Item_bool_func
 {
 public:
@@ -1817,45 +1833,6 @@ inline bool is_cond_or(Item *item)
   return (cond_item->functype() == Item_func::COND_OR_FUNC);
 }
 
-/*
-  XOR is Item_cond, not an Item_int_func because 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 *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); }
-};
-
-
 /* Some useful inline functions */
 
 inline Item *and_conds(Item *a, Item *b)
diff --git a/sql/item_func.h b/sql/item_func.h
index 63056f9079e..4ff7492bd89 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -44,7 +44,7 @@ public:
   enum Functype { UNKNOWN_FUNC,EQ_FUNC,EQUAL_FUNC,NE_FUNC,LT_FUNC,LE_FUNC,
 		  GE_FUNC,GT_FUNC,FT_FUNC,
 		  LIKE_FUNC,ISNULL_FUNC,ISNOTNULL_FUNC,
-		  COND_AND_FUNC, COND_OR_FUNC, COND_XOR_FUNC,
+		  COND_AND_FUNC, COND_OR_FUNC, XOR_FUNC,
                   BETWEEN, IN_FUNC, MULT_EQUAL_FUNC,
 		  INTERVAL_FUNC, ISNOTNULLTEST_FUNC,
 		  SP_EQUALS_FUNC, SP_DISJOINT_FUNC,SP_INTERSECTS_FUNC,
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 3337b1b487e..d2cef29cb08 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -7172,7 +7172,7 @@ expr:
         | expr XOR expr %prec XOR
           {
             /* XOR is a proprietary extension */
-            $$ = new (YYTHD->mem_root) Item_cond_xor($1, $3);
+            $$ = new (YYTHD->mem_root) Item_func_xor($1, $3);
             if ($$ == NULL)
               MYSQL_YYABORT;
           }