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.

1 files changed, 29 insertions, 0 deletions

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));