Fix for the bug #2198: SELECT INTO OUTFILE (with Sub-Select) Problem.

Proper Item_cache::setup() method.
Code cleanup.
(discussed with sanja)

sql/item.cc

@@ -1867,7 +1867,6 @@ void Item_cache_int::store(Item *item)
 {
   value= item->val_int_result();
   null_value= item->null_value;
-  collation.set(item->collation);
 }
 
 
@@ -1875,7 +1874,6 @@ void Item_cache_real::store(Item *item)
 {
   value= item->val_result();
   null_value= item->null_value;
-  collation.set(item->collation);
 }
 
 
@@ -1898,7 +1896,6 @@ void Item_cache_str::store(Item *item)
     value_buff.copy(*value);
     value= &value_buff;
   }
-  collation.set(item->collation);
 }
 
 

sql/item.h

@@ -878,13 +878,15 @@ class Item_cache: public Item
   void set_used_tables(table_map map) { used_table_map= map; }
 
   virtual bool allocate(uint i) { return 0; };
-  virtual bool setup(Item *item) { example= item;  return 0; };
-  virtual void store(Item *)= 0;
-  void set_len_n_dec(uint32 max_len, uint8 dec)
+  virtual bool setup(Item *item)
   {
-    max_length= max_len;
-    decimals= dec;
-  }
+    example= item;
+    max_length= item->max_length;
+    decimals= item->decimals;
+    collation.set(item->collation);
+    return 0;
+  };
+  virtual void store(Item *)= 0;
   enum Type type() const { return CACHE_ITEM; }
   static Item_cache* get_cache(Item_result type);
   table_map used_tables() const { return used_table_map; }

sql/item_subselect.cc

@@ -301,8 +301,6 @@ void Item_singlerow_subselect::fix_length_and_dec()
   if ((max_columns= engine->cols()) == 1)
   {
     engine->fix_length_and_dec(row= &value);
-    if (!(value= Item_cache::get_cache(engine->type())))
-      return;
   }
   else
   {
@@ -955,13 +953,9 @@ static Item_result set_row(List<Item> &item_list, Item *item,
     res_type= sel_item->result_type();
     item->decimals= sel_item->decimals;
     *maybe_null= sel_item->maybe_null;
-    if (row)
-    {
     if (!(row[i]= Item_cache::get_cache(res_type)))
       return STRING_RESULT; // we should return something
-      row[i]->set_len_n_dec(sel_item->max_length, sel_item->decimals);
-      row[i]->collation.set(sel_item->collation);
-    }
+    row[i]->setup(sel_item);
   }
   if (item_list.elements > 1)
     res_type= ROW_RESULT;
@@ -982,7 +976,10 @@ void subselect_union_engine::fix_length_and_dec(Item_cache **row)
   DBUG_ASSERT(row || unit->first_select()->item_list.elements==1);
 
   if (unit->first_select()->item_list.elements == 1)
+  {
     res_type= set_row(unit->types, item, row, &maybe_null);
+    item->collation.set(row[0]->collation);
+  }
   else
   {
     bool fake= 0;