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, 15 insertions, 0 deletions

diff --git a/sql/opt_sum.cc b/sql/opt_sum.cc
index 932aceebdbb..ce650701347 100644
--- a/sql/opt_sum.cc
+++ b/sql/opt_sum.cc
@@ -352,6 +352,18 @@ static bool simple_pred(Item_func *func_item, Item **args, bool *inv_order)
   Item *item;
   *inv_order= 0;
   switch (func_item->argument_count()) {
+  case 0:
+    /* MULT_EQUAL_FUNC */
+    {
+      Item_equal *item_equal= (Item_equal *) func_item;
+      Item_equal_iterator it(*item_equal);
+      args[0]= it++;
+      if (it++)
+        return 0;
+      if (!(args[1]= item_equal->get_const()))
+        return 0;
+    }
+    break;
   case 1:
     /* field IS NULL */
     item= func_item->arguments()[0];
@@ -492,6 +504,9 @@ static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo,
   case Item_func::BETWEEN:
     between= 1;
     break;
+  case Item_func::MULT_EQUAL_FUNC:
+    eq_type= 1;
+    break;
   default:
     return 0;                                        // Can't optimize function
   }