Bug #18895: BIT values cause joins to fail

The Field::eq() considered instances of Field_bit that differ only in 
bit_ptr/bit_ofs equal. This caused equality conditions optimization 
(build_equal_items_for_cond()) to make bad field substitutions that result
in wrong predicates. 
Field_bit requires an overloaded eq() function that checks the bit_ptr/bit_ofs
in addition to Field::eq().


mysql-test/r/select.result:
  Bug #18895: BIT values cause joins to fail
  
  - test case
mysql-test/t/select.test:
  Bug #18895: BIT values cause joins to fail
  
  - test case
sql/field.h:
  Bug #18895: BIT values cause joins to fail
  
  - eq() method overloaded for Field_bit

1 files changed, 8 insertions, 1 deletions

diff --git a/sql/field.h b/sql/field.h
index f4d27e46877..e7b7aa45c27 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -124,7 +124,7 @@ public:
   static bool type_can_have_key_part(enum_field_types);
   static enum_field_types field_type_merge(enum_field_types, enum_field_types);
   static Item_result result_merge_type(enum_field_types);
-  bool eq(Field *field)
+  virtual bool eq(Field *field)
   {
     return (ptr == field->ptr && null_ptr == field->null_ptr &&
             null_bit == field->null_bit);
@@ -1358,6 +1358,13 @@ public:
     bit_ptr= bit_ptr_arg;
     bit_ofs= bit_ofs_arg;
   }
+  bool eq(Field *field)
+  {
+    return (Field::eq(field) &&
+            field->type() == type() &&
+            bit_ptr == ((Field_bit *)field)->bit_ptr &&
+            bit_ofs == ((Field_bit *)field)->bit_ofs);
+  }
 };