LEFT JOIN optimization: Change LEFT JOIN to normal join if possible

mysql-test/r/select.result:
  Added test for LEFT JOIN optimization
mysql-test/t/select.test:
  Added test for LEFT JOIN optimization
sql/item.h:
  LEFT JOIN optimization
sql/item_cmpfunc.cc:
  LEFT JOIN optimization
sql/item_cmpfunc.h:
  LEFT JOIN optimization
sql/item_func.cc:
  LEFT JOIN optimization
sql/item_func.h:
  LEFT JOIN optimization
sql/item_strfunc.cc:
  LEFT JOIN optimization
sql/sql_base.cc:
  Heart of LEFT JOIN optimization

1 files changed, 10 insertions, 7 deletions

diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index 208be1ecd7f..20496a47671 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -606,9 +606,10 @@ void Item_func_concat_ws::fix_length_and_dec()
     max_length=MAX_BLOB_WIDTH;
     maybe_null=1;
   }
-  used_tables_cache|=separator->used_tables();
-  const_item_cache&=separator->const_item();
-  with_sum_func= with_sum_func || separator->with_sum_func;
+  used_tables_cache|=     separator->used_tables();
+  not_null_tables_cache&= separator->not_null_tables();
+  const_item_cache&=	  separator->const_item();
+  with_sum_func=	  with_sum_func || separator->with_sum_func;
 }
 
 void Item_func_concat_ws::update_used_tables()
@@ -1509,8 +1510,9 @@ void Item_func_elt::fix_length_and_dec()
   }
   maybe_null=1;					// NULL if wrong first arg
   with_sum_func= with_sum_func || item->with_sum_func;
-  used_tables_cache|=item->used_tables();
-  const_item_cache&=item->const_item();
+  used_tables_cache|=	  item->used_tables();
+  not_null_tables_cache&= item->not_null_tables();
+  const_item_cache&=	  item->const_item();
 }
 
 
@@ -1591,8 +1593,9 @@ void Item_func_make_set::fix_length_and_dec()
   max_length=arg_count-1;
   for (uint i=1 ; i < arg_count ; i++)
     max_length+=args[i]->max_length;
-  used_tables_cache|=item->used_tables();
-  const_item_cache&=item->const_item();
+  used_tables_cache|=	  item->used_tables();
+  not_null_tables_cache&= item->not_null_tables();
+  const_item_cache&=	  item->const_item();
   with_sum_func= with_sum_func || item->with_sum_func;
 }