This ChangeSet Introdices Item_equal.

The objects of this class represent multiple conjunctive equalities
in where conditions: =(f1,f2,...fn) <=> f1=f2 and f2= ... and =fn.
The objects are used to generate new possibale paths to access
the tables when executing a query.
They are also used to optimize the execution plan 
chosen by the optimizer for the query.  


sql/item.cc:
  Introduced Item_equal
sql/item.h:
  Introduced Item_equal.
  Added traverse method.
sql/item_cmpfunc.cc:
  Introduced Item_equal.
  Added traverse mehtod.
sql/item_cmpfunc.h:
  Itroduced Item_equal and Item_equal_iterator.
sql/item_func.cc:
  Added traverse method.
  Introduced Item_equal.
sql/item_func.h:
  Introduced Item_equal.
  Added traverse method.
sql/item_row.cc:
  Added traverse method.
sql/item_row.h:
  Added traverse method.
sql/item_strfunc.h:
  Added traverse method.
sql/opt_range.cc:
  Used Item_equal in range analysis.
sql/opt_sum.cc:
  Introduced Item_equal.
sql/sql_list.h:
  Added concat and disjoin methods to lists.
  Fixed remove method for lists.
sql/sql_select.cc:
  Introdiced Item_equal:
    created Item_equal;
    used Item_equal objects to generate new paths to access tables.
    used Item_equal objects to optimize the execution plan chosen by optimizer.
sql/sql_select.h:
  Introduced Item_equal.

1 files changed, 12 insertions, 0 deletions

diff --git a/sql/item_row.cc b/sql/item_row.cc
index 89b38c8a753..d7afe9ad5f0 100644
--- a/sql/item_row.cc
+++ b/sql/item_row.cc
@@ -140,6 +140,18 @@ bool Item_row::walk(Item_processor processor, byte *arg)
   return (this->*processor)(arg);
 }
 
+Item *Item_row::traverse(Item_calculator calculator, byte *arg)
+{
+  for (uint i= 0; i < arg_count; i++)
+  {
+    Item *new_item= items[i]->traverse(calculator, arg);
+    if (!new_item)
+      return 0;
+    items[i]= new_item;
+  }
+  return (this->*calculator)(arg);
+}
+
 void Item_row::bring_value()
 {
   for (uint i= 0; i < arg_count; i++)