New variable to turn off automatic charset conversion of query results

Some speed improvements

sql/mysqld.cc

@@ -4551,6 +4551,7 @@ static void set_options(void)
 		 sizeof(mysql_real_data_home)-1);
 
   /* Set default values for some variables */
+  global_system_variables.convert_result_charset= TRUE;
   global_system_variables.table_type=   DB_TYPE_MYISAM;
   global_system_variables.tx_isolation= ISO_REPEATABLE_READ;
   global_system_variables.select_limit= (ulonglong) HA_POS_ERROR;

sql/protocol.cc

@@ -703,11 +703,13 @@ bool Protocol_simple::store(const char *from, uint length, CHARSET_INFO *cs)
 	       field_types[field_pos] <= MYSQL_TYPE_GEOMETRY));
   field_pos++;
 #endif
-  if (cs != this->thd->charset())
+  if (!my_charset_same(cs, this->thd->charset()) &&
+      (cs != &my_charset_bin) &&
+      (this->thd->charset() != &my_charset_bin) &&
+      (this->thd->variables.convert_result_charset))
   {
-    String tmp;
-    tmp.copy(from, length, cs, this->thd->charset());
-    return net_store_data(tmp.ptr(), tmp.length());
+    convert.copy(from, length, cs, this->thd->charset());
+    return net_store_data(convert.ptr(), convert.length());
   }
   else
     return net_store_data(from, length);
@@ -800,16 +802,18 @@ bool Protocol_simple::store(Field *field)
   field_pos++;
 #endif
   char buff[MAX_FIELD_WIDTH];
-  String tmp1(buff,sizeof(buff), &my_charset_bin);
-  field->val_str(&tmp1,&tmp1);
-  if (field->charset() != this->thd->charset())
+  String str(buff,sizeof(buff), &my_charset_bin);
+  field->val_str(&str,&str);
+  if (!my_charset_same(field->charset(), this->thd->charset()) &&
+      (field->charset() != &my_charset_bin) &&
+      (this->thd->charset() != &my_charset_bin) &&
+      (this->thd->variables.convert_result_charset))
   {
-    String tmp;
-    tmp.copy(tmp1.ptr(), tmp1.length(), tmp1.charset(), this->thd->charset());
-    return net_store_data(tmp.ptr(), tmp.length());
+    convert.copy(str.ptr(), str.length(), str.charset(), this->thd->charset());
+    return net_store_data(convert.ptr(), convert.length());
   }
   else
-    return net_store_data(tmp1.ptr(), tmp1.length());
+    return net_store_data(str.ptr(), str.length());
 }
 
 

sql/protocol.h

@@ -30,6 +30,7 @@ class Protocol
 protected:
   THD	 *thd;
   String *packet;
+  String convert;
   uint field_pos;
 #ifndef DEBUG_OFF
   enum enum_field_types *field_types;
@@ -44,6 +45,7 @@ protected:
 public:
   Protocol() {}
   Protocol(THD *thd) { init(thd); }
+  virtual ~Protocol() {}
   void init(THD* thd);
   bool send_fields(List<Item> *list, uint flag);
   bool send_records_num(List<Item> *list, ulonglong records);

sql/set_var.cc

@@ -109,6 +109,8 @@ sys_var_bool_ptr	sys_concurrent_insert("concurrent_insert",
 					      &myisam_concurrent_insert);
 sys_var_long_ptr	sys_connect_timeout("connect_timeout",
 					    &connect_timeout);
+sys_var_thd_bool	sys_convert_result_charset("convert_result_charset",
+						   &SV::convert_result_charset);
 sys_var_enum		sys_delay_key_write("delay_key_write",
 					    &delay_key_write_options,
 					    &delay_key_write_typelib,
@@ -337,6 +339,7 @@ sys_var *sys_variables[]=
   &sys_client_collation,
   &sys_concurrent_insert,
   &sys_connect_timeout,
+  &sys_convert_result_charset,
   &sys_default_week_format,
   &sys_delay_key_write,
   &sys_delayed_insert_limit,
@@ -445,6 +448,7 @@ struct show_var_st init_vars[]= {
   {sys_client_collation.name, (char*) &sys_client_collation,	    SHOW_SYS},
   {sys_concurrent_insert.name,(char*) &sys_concurrent_insert,       SHOW_SYS},
   {sys_connect_timeout.name,  (char*) &sys_connect_timeout,         SHOW_SYS},
+  {sys_convert_result_charset.name, (char*) &sys_convert_result_charset, SHOW_SYS},
   {"datadir",                 mysql_real_data_home,                 SHOW_CHAR},
   {"default_week_format",     (char*) &sys_default_week_format,     SHOW_SYS},
   {sys_delay_key_write.name,  (char*) &sys_delay_key_write,         SHOW_SYS},
@@ -1455,7 +1459,6 @@ void set_var_init()
     (*var)->option_limits= find_option(my_long_options, (*var)->name);
     hash_insert(&system_variable_hash, (byte*) *var);
   }
-
   /*
     Special cases
     Needed because MySQL can't find the limits for a variable it it has

sql/sql_class.h

@@ -374,6 +374,7 @@ struct system_variables
   my_bool log_warnings;
   my_bool low_priority_updates;
   my_bool new_mode;
+  my_bool convert_result_charset;
 
   CHARSET_INFO 	*thd_charset;
 };