Fix for bug#49199: Optimizer handles incorrectly:

field='const1' AND field='const2' in some cases

Building multiple equality predicates containing
a constant which is compared as a datetime (with a field)
we should take this fact into account and compare the 
constant with another possible constatns as datetimes 
as well.

E.g. for the
SELECT ... WHERE a='2001-01-01' AND a='2001-01-01 00:00:00'
we should compare '2001-01-01' with '2001-01-01 00:00:00' as
datetimes but not as strings.


mysql-test/r/select.result:
  Fix for bug#49199: Optimizer handles incorrectly: 
  field='const1' AND field='const2' in some cases
    - test result.
mysql-test/t/select.test:
  Fix for bug#49199: Optimizer handles incorrectly: 
  field='const1' AND field='const2' in some cases
    - test case.
sql/item_cmpfunc.cc:
  Fix for bug#49199: Optimizer handles incorrectly: 
  field='const1' AND field='const2' in some cases
    - adding a constant to Item_equal compare it as
  a datetime value with stored one if there's a 
  date[time] field in a equality predicate.
sql/item_cmpfunc.h:
  Fix for bug#49199: Optimizer handles incorrectly: 
  field='const1' AND field='const2' in some cases
    - adding a constant to Item_equal compare it as
  a datetime value with stored one if there's a 
  date[time] field in a equality predicate.
sql/sql_select.cc:
  Fix for bug#49199: Optimizer handles incorrectly: 
  field='const1' AND field='const2' in some cases
    - adding a constant to Item_equal compare it as
  a datetime value with stored one if there's a 
  date[time] field in a equality predicate.

1 files changed, 40 insertions, 6 deletions

diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index d03c68b3560..5c2fb9857d5 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -4903,7 +4903,8 @@ Item *Item_bool_rowready_func2::negated_item()
 }
 
 Item_equal::Item_equal(Item_field *f1, Item_field *f2)
-  : Item_bool_func(), const_item(0), eval_item(0), cond_false(0)
+  : Item_bool_func(), const_item(0), eval_item(0), cond_false(0),
+    compare_as_dates(FALSE)
 {
   const_item_cache= 0;
   fields.push_back(f1);
@@ -4916,6 +4917,7 @@ Item_equal::Item_equal(Item *c, Item_field *f)
   const_item_cache= 0;
   fields.push_back(f);
   const_item= c;
+  compare_as_dates= f->is_datetime();
 }
 
 
@@ -4930,9 +4932,45 @@ Item_equal::Item_equal(Item_equal *item_equal)
     fields.push_back(item);
   }
   const_item= item_equal->const_item;
+  compare_as_dates= item_equal->compare_as_dates;
   cond_false= item_equal->cond_false;
 }
 
+
+void Item_equal::compare_const(Item *c)
+{
+  if (compare_as_dates)
+  {
+    cmp.set_datetime_cmp_func(&c, &const_item);
+    cond_false= cmp.compare();
+  }
+  else
+  {
+    Item_func_eq *func= new Item_func_eq(c, const_item);
+    func->set_cmp_func();
+    func->quick_fix_field();
+    cond_false= !func->val_int();
+  }
+  if (cond_false)
+    const_item_cache= 1;
+}
+
+
+void Item_equal::add(Item *c, Item_field *f)
+{
+  if (cond_false)
+    return;
+  if (!const_item)
+  {
+    DBUG_ASSERT(f);
+    const_item= c;
+    compare_as_dates= f->is_datetime();
+    return;
+  }
+  compare_const(c);
+}
+
+
 void Item_equal::add(Item *c)
 {
   if (cond_false)
@@ -4942,11 +4980,7 @@ void Item_equal::add(Item *c)
     const_item= c;
     return;
   }
-  Item_func_eq *func= new Item_func_eq(c, const_item);
-  func->set_cmp_func();
-  func->quick_fix_field();
-  if ((cond_false= !func->val_int()))
-    const_item_cache= 1;
+  compare_const(c);
 }
 
 void Item_equal::add(Item_field *f)