path: root/sql/item_sum.h

/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


/* classes for sum functions */

#ifdef __GNUC__
#pragma interface			/* gcc class implementation */
#endif

#include <my_tree.h>

class Item_sum :public Item_result_field
{
public:
  enum Sumfunctype
  { COUNT_FUNC,COUNT_DISTINCT_FUNC,SUM_FUNC,AVG_FUNC,MIN_FUNC,
    MAX_FUNC, UNIQUE_USERS_FUNC,STD_FUNC,VARIANCE_FUNC,SUM_BIT_FUNC,
    UDF_SUM_FUNC, GROUP_CONCAT_FUNC
  };

  Item **args, *tmp_args[2];
  Item **args_copy;			/* copy of arguments for PS */
  uint arg_count;
  bool quick_group;			/* If incremental update of fields */

  void mark_as_sum_func();
  Item_sum() :args_copy(0), arg_count(0), quick_group(1) 
  {
    mark_as_sum_func();
  }
  Item_sum(Item *a)
    :args(tmp_args), args_copy(0), arg_count(1), quick_group(1)
  {
    args[0]=a;
    mark_as_sum_func();
  }
  Item_sum( Item *a, Item *b )
    :args(tmp_args), args_copy(0),  arg_count(2), quick_group(1)
  {
    args[0]=a; args[1]=b;
    mark_as_sum_func();
  }
  Item_sum(List<Item> &list);
  //Copy constructor, need to perform subselects with temporary tables
  Item_sum(THD *thd, Item_sum *item);
  void cleanup();
  enum Type type() const { return SUM_FUNC_ITEM; }
  virtual enum Sumfunctype sum_func () const=0;
  inline bool reset() { clear(); return add(); };
  virtual void clear()= 0;
  virtual bool add()=0;
  /*
    Called when new group is started and results are being saved in
    a temporary table. Similar to reset(), but must also store value in
    result_field. Like reset() it is supposed to reset start value to
    default.
  */
  virtual void reset_field()=0;
  /*
    Called for each new value in the group, when temporary table is in use.
    Similar to add(), but uses temporary table field to obtain current value,
    Updated value is then saved in the field.
  */
  virtual void update_field()=0;
  virtual bool keep_field_type(void) const { return 0; }
  virtual void fix_length_and_dec() { maybe_null=1; null_value=1; }
  virtual const char *func_name() const { return "?"; }
  virtual Item *result_item(Field *field)
    { return new Item_field(field);}
  table_map used_tables() const { return ~(table_map) 0; } /* Not used */
  bool const_item() const { return 0; }
  bool is_null() { return null_value; }
  void update_used_tables() { }
  void make_field(Send_field *field);
  void print(String *str);
  void fix_num_length_and_dec();
  void no_rows_in_result() { reset(); }
  virtual bool setup(THD *thd) {return 0;}
  virtual void make_unique() {}
  Item *get_tmp_table_item(THD *thd);
  bool save_args_for_prepared_statements(THD *);
  bool save_args(Statement* stmt);

  bool walk (Item_processor processor, byte *argument);
};


class Item_sum_num :public Item_sum
{
public:
  Item_sum_num() :Item_sum() {}
  Item_sum_num(Item *item_par) :Item_sum(item_par) {}
  Item_sum_num(Item *a, Item* b) :Item_sum(a,b) {}
  Item_sum_num(List<Item> &list) :Item_sum(list) {}
  Item_sum_num(THD *thd, Item_sum_num *item) :Item_sum(thd, item) {}
  bool fix_fields(THD *, TABLE_LIST *, Item **);
  longlong val_int()
    { DBUG_ASSERT(fixed == 1); return (longlong) val(); } /* Real as default */
  String *val_str(String*str);
  void reset_field();
};


class Item_sum_int :public Item_sum_num
{
public:
  Item_sum_int(Item *item_par) :Item_sum_num(item_par) {}
  Item_sum_int(List<Item> &list) :Item_sum_num(list) {}
  Item_sum_int(THD *thd, Item_sum_int *item) :Item_sum_num(thd, item) {}
  double val() { DBUG_ASSERT(fixed == 1); return (double) val_int(); }
  String *val_str(String*str);
  enum Item_result result_type () const { return INT_RESULT; }
  void fix_length_and_dec()
  { decimals=0; max_length=21; maybe_null=null_value=0; }
};


class Item_sum_sum :public Item_sum_num
{
  double sum;
  void fix_length_and_dec() { maybe_null=null_value=1; }

  public:
  Item_sum_sum(Item *item_par) :Item_sum_num(item_par),sum(0.0) {}
  Item_sum_sum(THD *thd, Item_sum_sum *item) 
    :Item_sum_num(thd, item), sum(item->sum) {}
  enum Sumfunctype sum_func () const {return SUM_FUNC;}
  void clear();
  bool add();
  double val();
  void reset_field();
  void update_field();
  void no_rows_in_result() {}
  const char *func_name() const { return "sum"; }
  Item *copy_or_same(THD* thd);
};


class Item_sum_count :public Item_sum_int
{
  longlong count;
  table_map used_table_cache;

  public:
  Item_sum_count(Item *item_par)
    :Item_sum_int(item_par),count(0),used_table_cache(~(table_map) 0)
  {}
  Item_sum_count(THD *thd, Item_sum_count *item)
    :Item_sum_int(thd, item), count(item->count),
     used_table_cache(item->used_table_cache)
  {}
  table_map used_tables() const { return used_table_cache; }
  bool const_item() const { return !used_table_cache; }
  enum Sumfunctype sum_func () const { return COUNT_FUNC; }
  void clear();
  void no_rows_in_result() { count=0; }
  bool add();
  void make_const(longlong count_arg) { count=count_arg; used_table_cache=0; }
  longlong val_int();
  void reset_field();
  void update_field();
  const char *func_name() const { return "count"; }
  Item *copy_or_same(THD* thd);
};


class TMP_TABLE_PARAM;

class Item_sum_count_distinct :public Item_sum_int
{
  TABLE *table;
  table_map used_table_cache;
  uint32 *field_lengths;
  TMP_TABLE_PARAM *tmp_table_param;
  TREE tree_base;
  TREE *tree;
  /*
    Following is 0 normal object and pointer to original one for copy 
    (to correctly free resources)
  */
  Item_sum_count_distinct *original;

  uint key_length;
  CHARSET_INFO *key_charset;
  
  /*
    Calculated based on max_heap_table_size. If reached,
    walk the tree and dump it into MyISAM table
  */
  uint max_elements_in_tree;

  /*
    The first few bytes of record ( at least one)
    are just markers for deleted and NULLs. We want to skip them since
    they will just bloat the tree without providing any valuable info
  */
  int rec_offset;

  /*
    If there are no blobs, we can use a tree, which
    is faster than heap table. In that case, we still use the table
    to help get things set up, but we insert nothing in it
  */
  bool use_tree;
  bool always_null;		// Set to 1 if the result is always NULL

  int tree_to_myisam();

  friend int composite_key_cmp(void* arg, byte* key1, byte* key2);
  friend int simple_str_key_cmp(void* arg, byte* key1, byte* key2);
  friend int simple_raw_key_cmp(void* arg, byte* key1, byte* key2);
  friend int dump_leaf(byte* key, uint32 count __attribute__((unused)),
		       Item_sum_count_distinct* item);

  public:
  Item_sum_count_distinct(List<Item> &list)
    :Item_sum_int(list), table(0), used_table_cache(~(table_map) 0),
     tmp_table_param(0), tree(&tree_base), original(0), use_tree(0),
     always_null(0)
  { quick_group= 0; }
  Item_sum_count_distinct(THD *thd, Item_sum_count_distinct *item)
    :Item_sum_int(thd, item), table(item->table),
     used_table_cache(item->used_table_cache),
     field_lengths(item->field_lengths),
     tmp_table_param(item->tmp_table_param),
     tree(item->tree), original(item), key_length(item->key_length),
     max_elements_in_tree(item->max_elements_in_tree),
     rec_offset(item->rec_offset), use_tree(item->use_tree),
     always_null(item->always_null)
  {}
  void cleanup();

  table_map used_tables() const { return used_table_cache; }
  enum Sumfunctype sum_func () const { return COUNT_DISTINCT_FUNC; }
  void clear();
  bool add();
  longlong val_int();
  void reset_field() { return ;}		// Never called
  void update_field() { return ; }		// Never called
  const char *func_name() const { return "count_distinct"; }
  bool setup(THD *thd);
  void make_unique();
  Item *copy_or_same(THD* thd);
  void no_rows_in_result() {}
  void print(String *str);
};


/* Item to get the value of a stored sum function */

class Item_sum_avg;

class Item_avg_field :public Item_result_field
{
public:
  Field *field;
  Item_avg_field(Item_sum_avg *item);
  enum Type type() const { return FIELD_AVG_ITEM; }
  double val();
  longlong val_int() { /* can't be fix_fields()ed */ return (longlong) val(); }
  bool is_null() { (void) val_int(); return null_value; }
  String *val_str(String*);
  enum_field_types field_type() const { return MYSQL_TYPE_DOUBLE; }
  void fix_length_and_dec() {}
};


class Item_sum_avg :public Item_sum_num
{
  void fix_length_and_dec() { decimals+=4; maybe_null=1; }

  double sum;
  ulonglong count;

  public:
  Item_sum_avg(Item *item_par) :Item_sum_num(item_par), sum(0.0), count(0) {}
  Item_sum_avg(THD *thd, Item_sum_avg *item)
    :Item_sum_num(thd, item), sum(item->sum), count(item->count) {}
  enum Sumfunctype sum_func () const {return AVG_FUNC;}
  void clear();
  bool add();
  double val();
  void reset_field();
  void update_field();
  Item *result_item(Field *field)
  { return new Item_avg_field(this); }
  void no_rows_in_result() {}
  const char *func_name() const { return "avg"; }
  Item *copy_or_same(THD* thd);
};

class Item_sum_variance;

class Item_variance_field :public Item_result_field
{
public:
  Field *field;
  Item_variance_field(Item_sum_variance *item);
  enum Type type() const {return FIELD_VARIANCE_ITEM; }
  double val();
  longlong val_int() { /* can't be fix_fields()ed */ return (longlong) val(); }
  String *val_str(String*);
  bool is_null() { (void) val_int(); return null_value; }
  enum_field_types field_type() const { return MYSQL_TYPE_DOUBLE; }
  void fix_length_and_dec() {}
};


/*
  variance(a) =

  =  sum (ai - avg(a))^2 / count(a) )
  =  sum (ai^2 - 2*ai*avg(a) + avg(a)^2) / count(a)
  =  (sum(ai^2) - sum(2*ai*avg(a)) + sum(avg(a)^2))/count(a) = 
  =  (sum(ai^2) - 2*avg(a)*sum(a) + count(a)*avg(a)^2)/count(a) = 
  =  (sum(ai^2) - 2*sum(a)*sum(a)/count(a) + count(a)*sum(a)^2/count(a)^2 )/count(a) = 
  =  (sum(ai^2) - 2*sum(a)^2/count(a) + sum(a)^2/count(a) )/count(a) = 
  =  (sum(ai^2) - sum(a)^2/count(a))/count(a)
*/

class Item_sum_variance : public Item_sum_num
{
  double sum, sum_sqr;
  ulonglong count;
  void fix_length_and_dec() { decimals+=4; maybe_null=1; }

  public:
  Item_sum_variance(Item *item_par) :Item_sum_num(item_par),count(0) {}
  Item_sum_variance(THD *thd, Item_sum_variance *item):
    Item_sum_num(thd, item), sum(item->sum), sum_sqr(item->sum_sqr),
    count(item->count) {}
  enum Sumfunctype sum_func () const { return VARIANCE_FUNC; }
  void clear();
  bool add();
  double val();
  void reset_field();
  void update_field();
  Item *result_item(Field *field)
  { return new Item_variance_field(this); }
  const char *func_name() const { return "variance"; }
  Item *copy_or_same(THD* thd);
};

class Item_sum_std;

class Item_std_field :public Item_variance_field
{
public:
  Item_std_field(Item_sum_std *item);
  enum Type type() const { return FIELD_STD_ITEM; }
  double val();
};

/*
   standard_deviation(a) = sqrt(variance(a))
*/

class Item_sum_std :public Item_sum_variance
{
  public:
  Item_sum_std(Item *item_par) :Item_sum_variance(item_par) {}
  Item_sum_std(THD *thd, Item_sum_std *item)
    :Item_sum_variance(thd, item)
    {}
  enum Sumfunctype sum_func () const { return STD_FUNC; }
  double val();
  Item *result_item(Field *field)
    { return new Item_std_field(this); }
  const char *func_name() const { return "std"; }
  Item *copy_or_same(THD* thd);
};

// This class is a string or number function depending on num_func

class Item_sum_hybrid :public Item_sum
{
 protected:
  String value,tmp_value;
  double sum;
  longlong sum_int;
  Item_result hybrid_type;
  enum_field_types hybrid_field_type;
  int cmp_sign;
  table_map used_table_cache;
  CHARSET_INFO *cmp_charset;

  public:
  Item_sum_hybrid(Item *item_par,int sign)
    :Item_sum(item_par), sum(0.0), sum_int(0),
    hybrid_type(INT_RESULT), hybrid_field_type(FIELD_TYPE_LONGLONG),
    cmp_sign(sign), used_table_cache(~(table_map) 0),
    cmp_charset(&my_charset_bin)
  {}
  Item_sum_hybrid(THD *thd, Item_sum_hybrid *item):
    Item_sum(thd, item), value(item->value),
    sum(item->sum), sum_int(item->sum_int), hybrid_type(item->hybrid_type),
    hybrid_field_type(item->hybrid_field_type),cmp_sign(item->cmp_sign), 
    used_table_cache(item->used_table_cache), cmp_charset(item->cmp_charset) {}
  bool fix_fields(THD *, TABLE_LIST *, Item **);
  table_map used_tables() const { return used_table_cache; }
  bool const_item() const { return !used_table_cache; }

  void clear()
  {
    sum=0.0;
    sum_int=0;
    value.length(0);
    null_value=1;
  }
  double val();
  longlong val_int();
  void reset_field();
  String *val_str(String *);
  void make_const() { used_table_cache=0; }
  bool keep_field_type(void) const { return 1; }
  enum Item_result result_type () const { return hybrid_type; }
  enum enum_field_types field_type() const { return hybrid_field_type; }
  void update_field();
  void min_max_update_str_field();
  void min_max_update_real_field();
  void min_max_update_int_field();
};


class Item_sum_min :public Item_sum_hybrid
{
public:
  Item_sum_min(Item *item_par) :Item_sum_hybrid(item_par,1) {}
  Item_sum_min(THD *thd, Item_sum_min *item) :Item_sum_hybrid(thd, item) {}
  enum Sumfunctype sum_func () const {return MIN_FUNC;}

  bool add();
  const char *func_name() const { return "min"; }
  Item *copy_or_same(THD* thd);
};


class Item_sum_max :public Item_sum_hybrid
{
public:
  Item_sum_max(Item *item_par) :Item_sum_hybrid(item_par,-1) {}
  Item_sum_max(THD *thd, Item_sum_max *item) :Item_sum_hybrid(thd, item) {}
  enum Sumfunctype sum_func () const {return MAX_FUNC;}

  bool add();
  const char *func_name() const { return "max"; }
  Item *copy_or_same(THD* thd);
};


class Item_sum_bit :public Item_sum_int
{
protected:
  ulonglong reset_bits,bits;

public:
  Item_sum_bit(Item *item_par,ulonglong reset_arg)
    :Item_sum_int(item_par),reset_bits(reset_arg),bits(reset_arg) {}
  Item_sum_bit(THD *thd, Item_sum_bit *item):
    Item_sum_int(thd, item), reset_bits(item->reset_bits), bits(item->bits) {}
  enum Sumfunctype sum_func () const {return SUM_BIT_FUNC;}
  void clear();
  longlong val_int();
  void reset_field();
  void update_field();
  void fix_length_and_dec()
  { decimals=0; max_length=21; unsigned_flag=1; maybe_null=null_value=0; }
};


class Item_sum_or :public Item_sum_bit
{
public:
  Item_sum_or(Item *item_par) :Item_sum_bit(item_par,LL(0)) {}
  Item_sum_or(THD *thd, Item_sum_or *item) :Item_sum_bit(thd, item) {}
  bool add();
  const char *func_name() const { return "bit_or"; }
  Item *copy_or_same(THD* thd);
};


class Item_sum_and :public Item_sum_bit
{
  public:
  Item_sum_and(Item *item_par) :Item_sum_bit(item_par, ULONGLONG_MAX) {}
  Item_sum_and(THD *thd, Item_sum_and *item) :Item_sum_bit(thd, item) {}
  bool add();
  const char *func_name() const { return "bit_and"; }
  Item *copy_or_same(THD* thd);
};

class Item_sum_xor :public Item_sum_bit
{
  public:
  Item_sum_xor(Item *item_par) :Item_sum_bit(item_par,LL(0)) {}
  Item_sum_xor(THD *thd, Item_sum_xor *item) :Item_sum_bit(thd, item) {}
  bool add();
  const char *func_name() const { return "bit_xor"; }
  Item *copy_or_same(THD* thd);
};


/*
  User defined aggregates
*/

#ifdef HAVE_DLOPEN

class Item_udf_sum : public Item_sum
{
protected:
  udf_handler udf;

public:
  Item_udf_sum(udf_func *udf_arg) :Item_sum(), udf(udf_arg) { quick_group=0;}
  Item_udf_sum( udf_func *udf_arg, List<Item> &list )
    :Item_sum( list ), udf(udf_arg)
  { quick_group=0;}
  Item_udf_sum(THD *thd, Item_udf_sum *item)
    :Item_sum(thd, item), udf(item->udf) {}
  const char *func_name() const { return udf.name(); }
  bool fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
  {
    DBUG_ASSERT(fixed == 0);
    fixed= 1;
    return udf.fix_fields(thd,tables,this,this->arg_count,this->args);
  }
  enum Sumfunctype sum_func () const { return UDF_SUM_FUNC; }
  virtual bool have_field_update(void) const { return 0; }

  void clear();
  bool add();
  void reset_field() {};
  void update_field() {};
};


class Item_sum_udf_float :public Item_udf_sum
{
 public:
  Item_sum_udf_float(udf_func *udf_arg) :Item_udf_sum(udf_arg) {}
  Item_sum_udf_float(udf_func *udf_arg, List<Item> &list)
    :Item_udf_sum(udf_arg,list) {}
  Item_sum_udf_float(THD *thd, Item_sum_udf_float *item)
    :Item_udf_sum(thd, item) {}
  longlong val_int()
    { DBUG_ASSERT(fixed == 1); return (longlong) Item_sum_udf_float::val(); }
  double val();
  String *val_str(String*str);
  void fix_length_and_dec() { fix_num_length_and_dec(); }
  Item *copy_or_same(THD* thd);
};


class Item_sum_udf_int :public Item_udf_sum
{
public:
  Item_sum_udf_int(udf_func *udf_arg) :Item_udf_sum(udf_arg) {}
  Item_sum_udf_int(udf_func *udf_arg, List<Item> &list)
    :Item_udf_sum(udf_arg,list) {}
  Item_sum_udf_int(THD *thd, Item_sum_udf_int *item)
    :Item_udf_sum(thd, item) {}
  longlong val_int();
  double val()
    { DBUG_ASSERT(fixed == 1); return (double) Item_sum_udf_int::val_int(); }
  String *val_str(String*str);
  enum Item_result result_type () const { return INT_RESULT; }
  void fix_length_and_dec() { decimals=0; max_length=21; }
  Item *copy_or_same(THD* thd);
};


class Item_sum_udf_str :public Item_udf_sum
{
public:
  Item_sum_udf_str(udf_func *udf_arg) :Item_udf_sum(udf_arg) {}
  Item_sum_udf_str(udf_func *udf_arg, List<Item> &list)
    :Item_udf_sum(udf_arg,list) {}
  Item_sum_udf_str(THD *thd, Item_sum_udf_str *item)
    :Item_udf_sum(thd, item) {}
  String *val_str(String *);
  double val()
  {
    int err;
    String *res;  res=val_str(&str_value);
    return res ? my_strntod(res->charset(),(char*) res->ptr(),res->length(),
			    (char**) 0, &err) : 0.0;
  }
  longlong val_int()
  {
    int err;
    String *res;  res=val_str(&str_value);
    return res ? my_strntoll(res->charset(),res->ptr(),res->length(),10, (char**) 0, &err) : (longlong) 0;
  }
  enum Item_result result_type () const { return STRING_RESULT; }
  void fix_length_and_dec();
  Item *copy_or_same(THD* thd);
};

#else /* Dummy functions to get sql_yacc.cc compiled */

class Item_sum_udf_float :public Item_sum_num
{
 public:
  Item_sum_udf_float(udf_func *udf_arg) :Item_sum_num() {}
  Item_sum_udf_float(udf_func *udf_arg, List<Item> &list) :Item_sum_num() {}
  Item_sum_udf_float(THD *thd, Item_sum_udf_float *item)
    :Item_sum_num(thd, item) {}
  enum Sumfunctype sum_func () const { return UDF_SUM_FUNC; }
  double val() { DBUG_ASSERT(fixed == 1); return 0.0; }
  void clear() {}
  bool add() { return 0; }  
  void update_field() {}
};


class Item_sum_udf_int :public Item_sum_num
{
public:
  Item_sum_udf_int(udf_func *udf_arg) :Item_sum_num() {}
  Item_sum_udf_int(udf_func *udf_arg, List<Item> &list) :Item_sum_num() {}
  Item_sum_udf_int(THD *thd, Item_sum_udf_int *item)
    :Item_sum_num(thd, item) {}
  enum Sumfunctype sum_func () const { return UDF_SUM_FUNC; }
  longlong val_int() { DBUG_ASSERT(fixed == 1); return 0; }
  double val() { DBUG_ASSERT(fixed == 1); return 0; }
  void clear() {}
  bool add() { return 0; }  
  void update_field() {}
};


class Item_sum_udf_str :public Item_sum_num
{
public:
  Item_sum_udf_str(udf_func *udf_arg) :Item_sum_num() {}
  Item_sum_udf_str(udf_func *udf_arg, List<Item> &list)  :Item_sum_num() {}
  Item_sum_udf_str(THD *thd, Item_sum_udf_str *item)
    :Item_sum_num(thd, item) {}
  String *val_str(String *)
    { DBUG_ASSERT(fixed == 1); null_value=1; return 0; }
  double val() { DBUG_ASSERT(fixed == 1); null_value=1; return 0.0; }
  longlong val_int() { DBUG_ASSERT(fixed == 1); null_value=1; return 0; }
  enum Item_result result_type () const { return STRING_RESULT; }
  void fix_length_and_dec() { maybe_null=1; max_length=0; }
  enum Sumfunctype sum_func () const { return UDF_SUM_FUNC; }
  void clear() {}
  bool add() { return 0; }  
  void update_field() {}
};

#endif /* HAVE_DLOPEN */

class MYSQL_ERROR;

class Item_func_group_concat : public Item_sum
{
  THD *item_thd;
  TMP_TABLE_PARAM *tmp_table_param;
  uint max_elements_in_tree;
  MYSQL_ERROR *warning;
  bool warning_available;
  uint key_length;
  bool tree_mode;
  bool distinct;
  bool warning_for_row;
  bool always_null;

  friend int group_concat_key_cmp_with_distinct(void* arg, byte* key1,
					      byte* key2);
  friend int group_concat_key_cmp_with_order(void* arg, byte* key1,
					     byte* key2);
  friend int group_concat_key_cmp_with_distinct_and_order(void* arg,
							byte* key1,
							byte* key2);
  friend int dump_leaf_key(byte* key, uint32 count __attribute__((unused)),
			   Item_func_group_concat *group_concat_item);

 public:
  String result;
  String *separator;
  TREE tree_base;
  TREE *tree;
  TABLE *table;
  ORDER **order;
  TABLE_LIST *tables_list;
  ulong group_concat_max_len;
  uint show_elements;
  uint arg_count_order;
  uint arg_count_field;
  uint field_list_offset;
  uint count_cut_values;
  /*
    Following is 0 normal object and pointer to original one for copy 
    (to correctly free resources)
  */
  Item_func_group_concat *original;
  
  Item_func_group_concat(bool is_distinct,List<Item> *is_select,
                         SQL_LIST *is_order,String *is_separator);
			 
  Item_func_group_concat(THD *thd, Item_func_group_concat *item);
  ~Item_func_group_concat();
  void cleanup();

  enum Sumfunctype sum_func () const {return GROUP_CONCAT_FUNC;}
  const char *func_name() const { return "group_concat"; }
  virtual Item_result result_type () const { return STRING_RESULT; }
  void clear();
  bool add();
  void reset_field();
  bool fix_fields(THD *, TABLE_LIST *, Item **);
  bool setup(THD *thd);
  void make_unique();
  virtual void update_field() {}
  double val()
  {
    String *res;  res=val_str(&str_value);
    return res ? my_atof(res->c_ptr()) : 0.0;
  }
  longlong val_int()
  {
    String *res;  res=val_str(&str_value);
    return res ? strtoll(res->c_ptr(),(char**) 0,10) : (longlong) 0;
  }
  String* val_str(String* str);
  Item *copy_or_same(THD* thd);
  void no_rows_in_result() {}
  void print(String *str);
};