mariadb/sql/item.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 */


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

class Protocol;
struct st_table_list;
void item_init(void);			/* Init item functions */

class Item {
  uint loop_id;                         /* Used to find selfrefering loops */
  Item(const Item &);			/* Prevent use of these */
  void operator=(Item &);
public:
  static void *operator new(size_t size) {return (void*) sql_alloc((uint) size); }
  static void operator delete(void *ptr,size_t size) {} /*lint -e715 */

  enum Type {FIELD_ITEM, FUNC_ITEM, SUM_FUNC_ITEM, STRING_ITEM,
	     INT_ITEM, REAL_ITEM, NULL_ITEM, VARBIN_ITEM,
	     COPY_STR_ITEM, FIELD_AVG_ITEM, DEFAULT_VALUE_ITEM,
	     PROC_ITEM,COND_ITEM, REF_ITEM, FIELD_STD_ITEM, 
	     FIELD_VARIANCE_ITEM, CONST_ITEM,
             SUBSELECT_ITEM, ROW_ITEM, CACHE_ITEM};

  enum cond_result { COND_UNDEF,COND_OK,COND_TRUE,COND_FALSE };

  String str_value;			/* used to store value */
  my_string name;			/* Name from select */
  Item *next;
  uint32 max_length;
  uint8 marker,decimals;
  my_bool maybe_null;			/* If item may be null */
  my_bool null_value;			/* if item is null */
  my_bool unsigned_flag;
  my_bool with_sum_func;
  my_bool fixed;                        /* If item fixed with fix_fields */

  // alloc & destruct is done as start of select using sql_alloc
  Item();
  // copy constructor used by Item_field, Item_ref & agregate (sum) functions
  Item(Item &item);
  virtual ~Item() { name=0; }		/*lint -e1509 */
  void set_name(const char *str,uint length=0);
  void init_make_field(Send_field *tmp_field,enum enum_field_types type);
  virtual void make_field(Send_field *field);
  virtual bool fix_fields(THD *, struct st_table_list *, Item **);
  virtual int save_in_field(Field *field, bool no_conversions);
  virtual void save_org_in_field(Field *field)
  { (void) save_in_field(field, 1); }
  virtual int save_safe_in_field(Field *field)
  { return save_in_field(field, 1); }
  virtual bool send(Protocol *protocol, String *str);
  virtual bool eq(const Item *, bool binary_cmp) const;
  virtual Item_result result_type () const { return REAL_RESULT; }
  virtual enum_field_types field_type() const;
  virtual enum Type type() const =0;
  virtual double val()=0;
  virtual longlong val_int()=0;
  virtual String *val_str(String*)=0;
  virtual Field *tmp_table_field() { return 0; }
  virtual Field *tmp_table_field(TABLE *t_arg) { return 0; }
  virtual const char *full_name() const { return name ? name : "???"; }
  virtual double  val_result() { return val(); }
  virtual longlong val_int_result() { return val_int(); }
  virtual String *str_result(String* tmp) { return val_str(tmp); }
  virtual table_map used_tables() const { return (table_map) 0L; }
  virtual bool basic_const_item() const { return 0; }
  virtual Item *new_item() { return 0; }	/* Only for const items */
  virtual cond_result eq_cmp_result() const { return COND_OK; }
  inline uint float_length(uint decimals_par) const
  { return decimals != NOT_FIXED_DEC ? (DBL_DIG+2+decimals_par) : DBL_DIG+8;}
  virtual bool const_item() const { return used_tables() == 0; }
  virtual void print(String *str_arg) { str_arg->append(full_name()); }
  virtual void update_used_tables() {}
  virtual void split_sum_func(Item **ref_pointer_array, List<Item> &fields) {}
  virtual bool get_date(TIME *ltime,bool fuzzydate);
  virtual bool get_time(TIME *ltime);
  virtual bool is_null() { return 0; };
  virtual void top_level_item() {}
  virtual Item * get_same() { return this; }
  virtual Item * get_tmp_table_item() { return get_same(); }

  virtual bool binary() const
  { return str_value.charset()->state & MY_CS_BINSORT ? 1 : 0 ; }
  CHARSET_INFO *thd_charset() const;
  CHARSET_INFO *charset() const { return str_value.charset(); };
  void set_charset(CHARSET_INFO *cs) { str_value.set_charset(cs); }
  virtual void set_outer_resolving() {}

  // Row emulation
  virtual uint cols() { return 1; }
  virtual Item* el(uint i) { return this; }
  virtual Item** addr(uint i) { return 0; }
  virtual bool check_cols(uint c);
  // It is not row => null inside is impossible
  virtual bool null_inside() { return 0; }
  // used in row subselects to get value of elements
  virtual void bring_value() {}
};


class st_select_lex;
class Item_ident :public Item
{
public:
  const char *db_name;
  const char *table_name;
  const char *field_name;
  st_select_lex *depended_from;
  bool outer_resolving; /* used for items from reduced subselect */
  Item_ident(const char *db_name_par,const char *table_name_par,
	     const char *field_name_par)
    :db_name(db_name_par), table_name(table_name_par),
     field_name(field_name_par), depended_from(0), outer_resolving(0)
    { name = (char*) field_name_par; }
  // copy constructor used by Item_field & Item_ref
  Item_ident(Item_ident &item);
  const char *full_name() const;
  void set_outer_resolving() { outer_resolving= 1; }
};


class Item_field :public Item_ident
{
  void set_field(Field *field);
public:
  Field *field,*result_field;
  // Item_field() {}

  Item_field(const char *db_par,const char *table_name_par,
	     const char *field_name_par)
    :Item_ident(db_par,table_name_par,field_name_par),field(0),result_field(0)
  {}
  // copy constructor need to process subselect with temporary tables
  Item_field(Item_field &item);
  Item_field(Field *field);
  enum Type type() const { return FIELD_ITEM; }
  bool eq(const Item *item, bool binary_cmp) const;
  double val();
  longlong val_int();
  String *val_str(String*);
  double val_result();
  longlong val_int_result();
  String *str_result(String* tmp);
  bool send(Protocol *protocol, String *str_arg);
  bool fix_fields(THD *, struct st_table_list *, Item **);
  void make_field(Send_field *tmp_field);
  int save_in_field(Field *field,bool no_conversions);
  void save_org_in_field(Field *field);
  table_map used_tables() const;
  enum Item_result result_type () const
  {
    return field->result_type();
  }
  enum_field_types field_type() const
  {
    return field->type();
  }
  Field *tmp_table_field() { return result_field; }
  Field *tmp_table_field(TABLE *t_arg) { return result_field; }
  bool get_date(TIME *ltime,bool fuzzydate);  
  bool get_time(TIME *ltime);  
  bool is_null() { return field->is_null(); }
  Item * get_tmp_table_item();
  friend class Item_default_value;
};

class Item_null :public Item
{
public:
  Item_null(char *name_par=0)
    { maybe_null=null_value=TRUE; name= name_par ? name_par : (char*) "NULL";}
  enum Type type() const { return NULL_ITEM; }
  bool eq(const Item *item, bool binary_cmp) const;
  double val();
  longlong val_int();
  String *val_str(String *str);
  int save_in_field(Field *field, bool no_conversions);
  int save_safe_in_field(Field *field);
  bool send(Protocol *protocol, String *str);
  enum Item_result result_type () const { return STRING_RESULT; }
  enum_field_types field_type() const   { return MYSQL_TYPE_NULL; }
  bool fix_fields(THD *thd, struct st_table_list *list, Item **item)
  {
    bool res= Item::fix_fields(thd, list, item);
    max_length=0;
    return res;
  }
  bool basic_const_item() const { return 1; }
  Item *new_item() { return new Item_null(name); }
  bool is_null() { return 1; }
};

class Item_param :public Item
{
public:    
  longlong int_value;
  double   real_value;
  TIME     ltime;
  enum Item_result item_result_type;
  enum Type item_type;
  enum enum_field_types buffer_type;
  bool item_is_time;
  my_bool long_data_supplied;

  Item_param(char *name_par=0)
  { 
    name= name_par ? name_par : (char*) "?";
    long_data_supplied= false;
    item_type= STRING_ITEM;
    item_result_type = STRING_RESULT;
    item_is_time= false;
  }
  enum Type type() const { return item_type; }
  double val();
  longlong val_int();
  String *val_str(String*);
  int  save_in_field(Field *field, bool no_conversions);
  void set_null();
  void set_int(longlong i);
  void set_double(double i);
  void set_value(const char *str, uint length);
  void set_long_str(const char *str, ulong length);
  void set_long_binary(const char *str, ulong length);
  void set_longdata(const char *str, ulong length);
  void set_long_end();
  void set_time(TIME *tm, timestamp_type type);
  bool get_time(TIME *tm);
  void reset() {}
  void (*setup_param_func)(Item_param *param, uchar **pos);
  enum Item_result result_type () const
  { return item_result_type; }
  enum_field_types field_type() const { return MYSQL_TYPE_STRING; }
  Item *new_item() { return new Item_param(name); }
};

class Item_int :public Item
{
public:
  const longlong value;
  Item_int(int32 i,uint length=11) :value((longlong) i)
    { max_length=length;}
#ifdef HAVE_LONG_LONG
  Item_int(longlong i,uint length=21) :value(i)
    { max_length=length;}
#endif
  Item_int(const char *str_arg,longlong i,uint length) :value(i)
    { max_length=length; name=(char*) str_arg;}
  Item_int(const char *str_arg) :
    value(str_arg[0] == '-' ? strtoll(str_arg,(char**) 0,10) :
	  (longlong) strtoull(str_arg,(char**) 0,10))
    { max_length= (uint) strlen(str_arg); name=(char*) str_arg;}
  enum Type type() const { return INT_ITEM; }
  enum Item_result result_type () const { return INT_RESULT; }
  enum_field_types field_type() const { return MYSQL_TYPE_LONGLONG; }
  longlong val_int() { return value; }
  double val() { return (double) value; }
  String *val_str(String*);
  int save_in_field(Field *field, bool no_conversions);
  bool basic_const_item() const { return 1; }
  Item *new_item() { return new Item_int(name,value,max_length); }
  void print(String *str);
};


class Item_uint :public Item_int
{
public:
  Item_uint(const char *str_arg, uint length) :
    Item_int(str_arg, (longlong) strtoull(str_arg,(char**) 0,10), length) {}
  Item_uint(uint32 i) :Item_int((longlong) i, 10) {}
  double val() { return ulonglong2double(value); }
  String *val_str(String*);
  Item *new_item() { return new Item_uint(name,max_length); }
  bool fix_fields(THD *thd, struct st_table_list *list, Item **item)
  {
    bool res= Item::fix_fields(thd, list, item);
    unsigned_flag= 1;
    return res;
  }
  void print(String *str);
};


class Item_real :public Item
{
public:
  const double value;
  // Item_real() :value(0) {}
  Item_real(const char *str_arg,uint length) :value(atof(str_arg))
  {
    name=(char*) str_arg;
    decimals=(uint8) nr_of_decimals(str_arg);
    max_length=length;
  }
  Item_real(const char *str,double val_arg,uint decimal_par,uint length)
    :value(val_arg)
  {
    name=(char*) str;
    decimals=(uint8) decimal_par;
    max_length=length;
  }
  Item_real(double value_par) :value(value_par) {}
  int save_in_field(Field *field, bool no_conversions);
  enum Type type() const { return REAL_ITEM; }
  enum_field_types field_type() const { return MYSQL_TYPE_DOUBLE; }
  double val() { return value; }
  longlong val_int() { return (longlong) (value+(value > 0 ? 0.5 : -0.5));}
  String *val_str(String*);
  bool basic_const_item() const { return 1; }
  Item *new_item() { return new Item_real(name,value,decimals,max_length); }
};


class Item_float :public Item_real
{
public:
  Item_float(const char *str,uint length) :Item_real(str,length)
  {
    decimals=NOT_FIXED_DEC;
    max_length=DBL_DIG+8;
  }
};

class Item_string :public Item
{
public:
  Item_string(const char *str,uint length,CHARSET_INFO *cs)
  {
    str_value.set(str,length,cs);
    max_length=length;
    name=(char*) str_value.ptr();
    decimals=NOT_FIXED_DEC;
  }
  Item_string(const char *name_par, const char *str, uint length,
	      CHARSET_INFO *cs)
  {
    str_value.set(str,length,cs);
    max_length=length;
    name=(char*) name_par;
    decimals=NOT_FIXED_DEC;
  }
  ~Item_string() {}
  enum Type type() const { return STRING_ITEM; }
  double val()
  { 
    int err;
    return my_strntod(str_value.charset(), (char*) str_value.ptr(),
		      str_value.length(), (char**) 0, &err);
  }
  longlong val_int()
  {
    int err;
    return my_strntoll(str_value.charset(), str_value.ptr(),
		       str_value.length(), 10, (char**) 0, &err);
  }
  String *val_str(String*) { return (String*) &str_value; }
  int save_in_field(Field *field, bool no_conversions);
  enum Item_result result_type () const { return STRING_RESULT; }
  enum_field_types field_type() const { return MYSQL_TYPE_STRING; }
  bool basic_const_item() const { return 1; }
  bool eq(const Item *item, bool binary_cmp) const;
  Item *new_item() 
  {
    return new Item_string(name, str_value.ptr(), max_length,
			   default_charset_info);
  }
  String *const_string() { return &str_value; }
  inline void append(char *str, uint length) { str_value.append(str, length); }
  void print(String *str);
};

/* for show tables */

class Item_datetime :public Item_string
{
public:
  Item_datetime(const char *item_name): Item_string(item_name,"",0,default_charset_info)
  { max_length=19;}
  enum_field_types field_type() const { return MYSQL_TYPE_DATETIME; }
};

class Item_empty_string :public Item_string
{
public:
  Item_empty_string(const char *header,uint length) :Item_string("",0,default_charset_info)
    { name=(char*) header; max_length=length;}
};

class Item_return_int :public Item_int
{
  enum_field_types int_field_type;
public:
  Item_return_int(const char *name, uint length,
		  enum_field_types field_type_arg)
    :Item_int(name, 0, length), int_field_type(field_type_arg)
  {
    unsigned_flag=1;
  }
  enum_field_types field_type() const { return int_field_type; }
};


class Item_varbinary :public Item
{
public:
  Item_varbinary(const char *str,uint str_length);
  ~Item_varbinary() {}
  enum Type type() const { return VARBIN_ITEM; }
  double val() { return (double) Item_varbinary::val_int(); }
  longlong val_int();
  String *val_str(String*) { return &str_value; }
  int save_in_field(Field *field, bool no_conversions);
  enum Item_result result_type () const { return INT_RESULT; }
  enum_field_types field_type() const { return MYSQL_TYPE_STRING; }
};


class Item_result_field :public Item	/* Item with result field */
{
public:
  Field *result_field;				/* Save result here */
  Item_result_field() :result_field(0) {}
  Item_result_field(Item_result_field &item): Item(item)
  {
    result_field= item.result_field;
  }
  ~Item_result_field() {}			/* Required with gcc 2.95 */
  Field *tmp_table_field() { return result_field; }
  Field *tmp_table_field(TABLE *t_arg) { return result_field; }
  table_map used_tables() const { return 1; }
  virtual void fix_length_and_dec()=0;
};


class Item_ref :public Item_ident
{
public:
  Item **ref;
  Item_ref(char *db_par,char *table_name_par,char *field_name_par)
    :Item_ident(db_par,table_name_par,field_name_par),ref(0) {}
  Item_ref(Item **item, char *table_name_par,char *field_name_par)
    :Item_ident(NullS,table_name_par,field_name_par),ref(item) {}
  // copy constructor need to process subselect with temporary tables
  Item_ref(Item_ref &item): Item_ident(item), ref(item.ref) {}
  enum Type type() const		{ return REF_ITEM; }
  bool eq(const Item *item, bool binary_cmp) const
  { return ref && (*ref)->eq(item, binary_cmp); }
  ~Item_ref() { if (ref && (*ref) != this) delete *ref; }
  double val()
  {
    double tmp=(*ref)->val_result();
    null_value=(*ref)->null_value;
    return tmp;
  }
  longlong val_int()
  {
    longlong tmp=(*ref)->val_int_result();
    null_value=(*ref)->null_value;
    return tmp;
  }
  String *val_str(String* tmp)
  {
    tmp=(*ref)->str_result(tmp);
    null_value=(*ref)->null_value;
    return tmp;
  }
  bool is_null()
  {
    (void) (*ref)->val_int_result();
    return (*ref)->null_value;
  }
  bool get_date(TIME *ltime,bool fuzzydate)
  {  
    return (null_value=(*ref)->get_date(ltime,fuzzydate));
  }
  bool send(Protocol *prot, String *tmp){ return (*ref)->send(prot, tmp); }
  void make_field(Send_field *field)	{ (*ref)->make_field(field); }
  bool fix_fields(THD *, struct st_table_list *, Item **);
  int save_in_field(Field *field, bool no_conversions)
  { return (*ref)->save_in_field(field, no_conversions); }
  void save_org_in_field(Field *field)	{ (*ref)->save_org_in_field(field); }
  enum Item_result result_type () const { return (*ref)->result_type(); }
  enum_field_types field_type() const   { return (*ref)->field_type(); }
  table_map used_tables() const		{ return (*ref)->used_tables(); }
};

class Item_in_subselect;
class Item_ref_null_helper: public Item_ref
{
protected:
  Item_in_subselect* owner;
public:
  Item_ref_null_helper(Item_in_subselect* master, Item **item,
		       char *table_name_par, char *field_name_par):
    Item_ref(item, table_name_par, field_name_par), owner(master) {}
  double val();
  longlong val_int();
  String* val_str(String* s);
  bool get_date(TIME *ltime, bool fuzzydate);
};


/*
  Used to find item in list of select items after '*' items processing.

  Because item '*' can be used in item list. when we create
  Item_ref_on_list_position we do not know how item list will be changed, but
  we know number of item position (I mean queries like "select * from t").
*/
class Item_ref_on_list_position: public Item_ref_null_helper
{
protected:
  st_select_lex *select_lex;
  uint pos;
public:
  Item_ref_on_list_position(Item_in_subselect* master,
			    st_select_lex *sl, uint num,
			    char *table_name, char *field_name):
    Item_ref_null_helper(master, 0, table_name, field_name),
    select_lex(sl), pos(num) {}
  bool fix_fields(THD *, struct st_table_list *, Item ** ref);
};

/*
  To resolve '*' field moved to condition
  and register NULL values
*/
class Item_asterisk_remover :public Item_ref_null_helper
{
  Item *item;
public:
  Item_asterisk_remover(Item_in_subselect *master, Item *it,
			char *table, char *field):
    Item_ref_null_helper(master, &item, table, field),
    item(it) 
  {}
  bool fix_fields(THD *, struct st_table_list *, Item ** ref);
};

/*
  The following class is used to optimize comparing of date columns
  We need to save the original item, to be able to set the field to the
  original value in 'opt_range'.
*/

class Item_int_with_ref :public Item_int
{
  Item *ref;
public:
  Item_int_with_ref(longlong i, Item *ref_arg) :Item_int(i), ref(ref_arg)
  {}
  int save_in_field(Field *field, bool no_conversions)
  {
    return ref->save_in_field(field, no_conversions);
  }
};


#include "gstream.h"
#include "spatial.h"
#include "item_sum.h"
#include "item_func.h"
#include "item_row.h"
#include "item_cmpfunc.h"
#include "item_strfunc.h"
#include "item_timefunc.h"
#include "item_uniq.h"
#include "item_subselect.h"

class Item_copy_string :public Item
{
  enum enum_field_types cached_field_type;
public:
  Item *item;
  Item_copy_string(Item *i) :item(i)
  {
    null_value=maybe_null=item->maybe_null;
    decimals=item->decimals;
    max_length=item->max_length;
    name=item->name;
    cached_field_type= item->field_type();
  }
  ~Item_copy_string() { delete item; }
  enum Type type() const { return COPY_STR_ITEM; }
  enum Item_result result_type () const { return STRING_RESULT; }
  enum_field_types field_type() const { return cached_field_type; }
  double val()
  {
    int err;
    return (null_value ? 0.0 :
	    my_strntod(str_value.charset(), (char*) str_value.ptr(),
		       str_value.length(),NULL,&err));
  }
  longlong val_int()
  { 
    int err;
    return null_value ? LL(0) : my_strntoll(str_value.charset(),str_value.ptr(),str_value.length(),10, (char**) 0,&err); 
  }
  String *val_str(String*);
  void make_field(Send_field *field) { item->make_field(field); }
  void copy();
  table_map used_tables() const { return (table_map) 1L; }
  bool const_item() const { return 0; }
  bool is_null() { return null_value; }
};


class Item_buff :public Sql_alloc
{
public:
  my_bool null_value;
  Item_buff() :null_value(0) {}
  virtual bool cmp(void)=0;
  virtual ~Item_buff(); /*line -e1509 */
};

class Item_str_buff :public Item_buff
{
  Item *item;
  String value,tmp_value;
public:
  Item_str_buff(Item *arg) :item(arg),value(arg->max_length) {}
  bool cmp(void);
  ~Item_str_buff();				// Deallocate String:s
};


class Item_real_buff :public Item_buff
{
  Item *item;
  double value;
public:
  Item_real_buff(Item *item_par) :item(item_par),value(0.0) {}
  bool cmp(void);
};

class Item_int_buff :public Item_buff
{
  Item *item;
  longlong value;
public:
  Item_int_buff(Item *item_par) :item(item_par),value(0) {}
  bool cmp(void);
};


class Item_field_buff :public Item_buff
{
  char *buff;
  Field *field;
  uint length;

public:
  Item_field_buff(Item_field *item)
  {
    field=item->field;
    buff= (char*) sql_calloc(length=field->pack_length());
  }
  bool cmp(void);
};

class Item_default_value : public Item_field
{
public:
  Item *arg;
  Item_default_value() :
    Item_field((const char *)NULL, (const char *)NULL, (const char *)NULL), arg(NULL) {}
  Item_default_value(Item *a) : 
    Item_field((const char *)NULL, (const char *)NULL, (const char *)NULL), arg(a) {}
  enum Type type() const { return DEFAULT_VALUE_ITEM; }
  bool eq(const Item *item, bool binary_cmp) const;
  bool fix_fields(THD *, struct st_table_list *, Item **);
  void set_outer_resolving() { arg->set_outer_resolving(); }
  void print(String *str);
  virtual bool basic_const_item() const { return true; }
  int save_in_field(Field *field, bool no_conversions)
  {
    if (!arg)
    {
      field->set_default();
      return 0;
    }
    return Item_field::save_in_field(field, no_conversions);
  }
  table_map used_tables() const { return (table_map)0L; }
};

class Item_cache: public Item
{
  table_map used_table_map;
public:
  Item_cache(): used_table_map(0) {fixed= 1; null_value= 1;}

  void set_used_tables(table_map map) { used_table_map= map; }

  virtual bool allocate(uint i) { return 0; };
  virtual bool setup(Item *) { return 0; };
  virtual void store(Item *)= 0;
  void set_len_n_dec(uint32 max_len, uint8 dec)
  {
    max_length= max_len;
    decimals= dec;
  }
  enum Type type() const { return CACHE_ITEM; }
  static Item_cache* get_cache(Item_result type);
  table_map used_tables() const { return used_table_map; }
};

class Item_cache_int: public Item_cache
{
  longlong value;
public:
  Item_cache_int(): Item_cache() {}
  
  void store(Item *item)
  {
    value= item->val_int_result();
    null_value= item->null_value;
  }
  double val() { return (double) value; }
  longlong val_int() { return value; }
  String* val_str(String *str) { str->set(value, thd_charset()); return str; }
  enum Item_result result_type() const { return INT_RESULT; }
};

class Item_cache_real: public Item_cache
{
  double value;
public:
  Item_cache_real(): Item_cache() {}
  
  void store(Item *item)
  {
    value= item->val_result();
    null_value= item->null_value;
  }
  double val() { return value; }
  longlong val_int() { return (longlong) (value+(value > 0 ? 0.5 : -0.5)); }
  String* val_str(String *str)
  {
    str->set(value, decimals, thd_charset());
    return str;
  }
  enum Item_result result_type() const { return REAL_RESULT; }
};

class Item_cache_str: public Item_cache
{
  char buffer[80];
  String *value;
public:
  Item_cache_str(): Item_cache() { }
  
  void store(Item *item);
  double val();
  longlong val_int();
  String* val_str(String *) { return value; }
  enum Item_result result_type() const { return STRING_RESULT; }
  CHARSET_INFO *charset() const { return value->charset(); };
};

class Item_cache_row: public Item_cache
{
  Item_cache  **values;
  uint item_count;
public:
  Item_cache_row(): Item_cache(), values(0), item_count(2) {}
  
  /*
    'allocate' used only in row transformer, to preallocate space for row 
    cache.
  */
  bool allocate(uint num);
  /*
    'setup' is needed only by row => it not called by simple row subselect
    (only by IN subselect (in subselect optimizer))
  */
  bool setup(Item *item);
  void store(Item *item);
  void illegal_method_call(const char *);
  void make_field(Send_field *)
  {
    illegal_method_call((const char*)"make_field");
  };
  double val()
  {
    illegal_method_call((const char*)"val");
    return 0;
  };
  longlong val_int()
  {
    illegal_method_call((const char*)"val_int");
    return 0;
  };
  String *val_str(String *)
  {
    illegal_method_call((const char*)"val_str");
    return 0;
  };
  enum Item_result result_type() const { return ROW_RESULT; }
  
  uint cols() { return item_count; }
  Item* el(uint i) { return values[i]; }
  Item** addr(uint i) { return (Item **) (values + i); }
  bool check_cols(uint c);
  bool null_inside();
  void bring_value();
};

extern Item_buff *new_Item_buff(Item *item);
extern Item_result item_cmp_type(Item_result a,Item_result b);
extern Item *resolve_const_item(Item *item,Item *cmp_item);
extern bool field_is_equal_to_item(Field *field,Item *item);