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, 2 insertions, 0 deletions

diff --git a/sql/sql_select.h b/sql/sql_select.h
index 24854713a0e..ad2adc2ee0f 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -184,6 +184,7 @@ class JOIN :public Sql_alloc
   ORDER *order, *group_list, *proc_param; //hold parameters of mysql_select
   COND *conds;                            // ---"---
   Item *conds_history;                    // store WHERE for explain
+  COND_EQUAL *cond_equal;
   TABLE_LIST *tables_list;           //hold 'tables' parameter of mysql_selec
   SQL_SELECT *select;                //created in optimisation phase
   Item **ref_pointer_array; //used pointer reference for this select
@@ -243,6 +244,7 @@ class JOIN :public Sql_alloc
     ref_pointer_array_size= 0;
     zero_result_cause= 0;
     optimized= 0;
+    cond_equal= 0;
 
     fields_list= fields;
     bzero((char*) &keyuse,sizeof(keyuse));