Commit 03dfd986 authored by holyfoot/hf@mysql.com/hfmain.(none)'s avatar holyfoot/hf@mysql.com/hfmain.(none)
Browse files

Bug #29878 Garbage data generation when executing SESSION_USER() on a slave. 

Item_func_user doesn't calculate anything in it's val_str() method,
just returns saved str_value.
Though Item::save_in_field method can destroy str_value, relying on
val_str() return. As a result we get the garbage stored in field.

We cannot use Item::save_in_field implementation for Item_func_user,
reimplement it in simpler way.
parent 14cbdecf

mysql-test/r/rpl_session_var.result

+10 −0
Original line number Diff line number Diff line
@@ -41,3 +41,13 @@ select * from t2 order by b; 
b	a

1	1

drop table t1,t2;

CREATE TABLE t1 (

`id` int(11) NOT NULL auto_increment,

`data` varchar(100),

PRIMARY KEY  (`id`)

) ENGINE=MyISAM;

INSERT INTO t1(data) VALUES(SESSION_USER());

SELECT * FROM t1;

id	data

1	

drop table t1;

mysql-test/t/rpl_session_var.test

+22 −0
Original line number Diff line number Diff line
@@ -40,3 +40,25 @@ drop table t1,t2; 
save_master_pos;

connection slave;

sync_with_master;



#

# Bug #29878 Garbage data generation when executing SESSION_USER() on a slave. 

#



connection master;

CREATE TABLE t1 (

  `id` int(11) NOT NULL auto_increment,

  `data` varchar(100),

  PRIMARY KEY  (`id`)

 ) ENGINE=MyISAM;



INSERT INTO t1(data) VALUES(SESSION_USER());

save_master_pos;

connection slave;

sync_with_master;

SELECT * FROM t1;

connection master;

drop table t1;

save_master_pos;

connection slave;

sync_with_master;

sql/item.cc

+38 −14
Original line number Diff line number Diff line
@@ -336,6 +336,37 @@ int Item::save_date_in_field(Field *field) 
}





/*

  Store the string value in field directly



  SYNOPSIS

    Item::save_str_value_in_field()

    field   a pointer to field where to store

    result  the pointer to the string value to be stored



  DESCRIPTION

    The method is used by Item_*::save_in_field implementations

    when we don't need to calculate the value to store

    See Item_string::save_in_field() implementation for example



  IMPLEMENTATION

    Check if the Item is null and stores the NULL or the

    result value in the field accordingly.



  RETURN

    Nonzero value if error

*/



int Item::save_str_value_in_field(Field *field, String *result)

{

  if (null_value)

    return set_field_to_null(field);

  field->set_notnull();

  return field->store(result->ptr(), result->length(),

		      collation.collation);

}





Item::Item():

  rsize(0), name(0), orig_name(0), name_length(0), fixed(0),

  is_autogenerated_name(TRUE),
@@ -3009,16 +3040,6 @@ my_decimal *Item_copy_string::val_decimal(my_decimal *decimal_value) 
}







int Item_copy_string::save_in_field(Field *field, bool no_conversions)

{

  if (null_value)

    return set_field_to_null(field);

  field->set_notnull();

  return field->store(str_value.ptr(),str_value.length(),

		      collation.collation);

}



/*

  Functions to convert item to field (for send_fields)

*/
@@ -4417,6 +4438,12 @@ int Item_null::save_safe_in_field(Field *field) 
}





/*

  This implementation can lose str_value content, so if the

  Item uses str_value to store something, it should

  reimplement it's ::save_in_field() as Item_string, for example, does

*/



int Item::save_in_field(Field *field, bool no_conversions)

{

  int error;
@@ -4474,10 +4501,7 @@ int Item_string::save_in_field(Field *field, bool no_conversions) 
{

  String *result;

  result=val_str(&str_value);

  if (null_value)

    return set_field_to_null(field);

  field->set_notnull();

  return field->store(result->ptr(),result->length(),collation.collation);

  return save_str_value_in_field(field, result);

}

sql/item.h

+5 −1
Original line number Diff line number Diff line
@@ -612,6 +612,7 @@ class Item { 


  int save_time_in_field(Field *field);

  int save_date_in_field(Field *field);

  int save_str_value_in_field(Field *field, String *result);



  virtual Field *get_tmp_table_field() { return 0; }

  /* This is also used to create fields in CREATE ... SELECT: */
@@ -2166,7 +2167,10 @@ class Item_copy_string :public Item 
  my_decimal *val_decimal(my_decimal *);

  void make_field(Send_field *field) { item->make_field(field); }

  void copy();

  int save_in_field(Field *field, bool no_conversions);

  int save_in_field(Field *field, bool no_conversions)

  {

    return save_str_value_in_field(field, &str_value);

  }

  table_map used_tables() const { return (table_map) 1L; }

  bool const_item() const { return 0; }

  bool is_null() { return null_value; }

sql/item_strfunc.h

+4 −0
Original line number Diff line number Diff line
@@ -434,6 +434,10 @@ class Item_func_user :public Item_func_sysconst 
  }

  const char *func_name() const { return "user"; }

  const char *fully_qualified_func_name() const { return "user()"; }

  int save_in_field(Field *field, bool no_conversions)

  {

    return save_str_value_in_field(field, &str_value);

  }

};