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/* Copyright (C) 2000 MySQL 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 */
/* subselect Item */
#ifdef __GNUC__
#pragma interface /* gcc class implementation */
#endif
class st_select_lex;
class st_select_lex_unit;
class JOIN;
class select_subselect;
class subselect_engine;
/* base class for subselects */
class Item_subselect :public Item_result_field
{
my_bool engine_owner; /* Is this item owner of engine */
my_bool value_assigned; /* value already assigned to subselect */
protected:
/* engine that perform execution of subselect (single select or union) */
subselect_engine *engine;
/* allowed number of columns (1 for single value subqueries) */
uint max_columns;
public:
Item_subselect();
Item_subselect(Item_subselect *item)
{
null_value= item->null_value;
decimals= item->decimals;
max_columns= item->max_columns;
engine= item->engine;
engine_owner= 0;
name= item->name;
}
/*
We need this method, because some compilers do not allow 'this'
pointer in constructor initialization list, but we need pass pointer
to subselect Item class to select_subselect classes constructor.
*/
void init (THD *thd, st_select_lex *select_lex, select_subselect *result);
~Item_subselect();
virtual void assign_null()
{
null_value= 1;
}
bool assigned() { return value_assigned; }
void assigned(bool a) { value_assigned= a; }
enum Type type() const;
bool is_null() { return null_value; }
void make_field (Send_field *);
bool fix_fields(THD *thd, TABLE_LIST *tables, Item **ref);
virtual void fix_length_and_dec();
table_map used_tables() const;
bool check_loop(uint id);
friend class select_subselect;
};
/* single value subselect */
class Item_singleval_subselect :public Item_subselect
{
protected:
longlong int_value; /* Here stored integer value of this item */
double real_value; /* Here stored real value of this item */
/*
Here stored string value of this item.
(str_value used only as temporary buffer, because it can be changed
by Item::save_field)
*/
String string_value;
enum Item_result res_type; /* type of results */
public:
Item_singleval_subselect(THD *thd, st_select_lex *select_lex);
Item_singleval_subselect(Item_singleval_subselect *item):
Item_subselect(item)
{
int_value= item->int_value;
real_value= item->real_value;
string_value.set(item->string_value, 0, item->string_value.length());
max_length= item->max_length;
decimals= item->decimals;
res_type= item->res_type;
}
virtual void assign_null()
{
null_value= 1;
int_value= 0;
real_value= 0;
max_length= 4;
res_type= STRING_RESULT;
}
double val ();
longlong val_int ();
String *val_str (String *);
Item *new_item() { return new Item_singleval_subselect(this); }
enum Item_result result_type() const { return res_type; }
void fix_length_and_dec();
friend class select_singleval_subselect;
};
/* exists subselect */
class Item_exists_subselect :public Item_subselect
{
protected:
longlong value; /* value of this item (boolean: exists/not-exists) */
public:
Item_exists_subselect(THD *thd, st_select_lex *select_lex);
Item_exists_subselect(Item_exists_subselect *item):
Item_subselect(item)
{
value= item->value;
}
virtual void assign_null()
{
value= 0;
}
Item *new_item() { return new Item_exists_subselect(this); }
enum Item_result result_type() const { return INT_RESULT;}
longlong val_int();
double val();
String *val_str(String*);
void fix_length_and_dec();
friend class select_exists_subselect;
};
class subselect_engine
{
protected:
select_subselect *result; /* results storage class */
THD *thd; /* pointer to current THD */
Item_subselect *item; /* item, that use this engine */
enum Item_result res_type; /* type of results */
public:
static void *operator new(size_t size)
{
return (void*) sql_alloc((uint) size);
}
static void operator delete(void *ptr, size_t size) {}
subselect_engine(THD *thd, Item_subselect *si, select_subselect *res)
{
result= res;
item= si;
this->thd= thd;
res_type= STRING_RESULT;
}
virtual int prepare()= 0;
virtual void fix_length_and_dec()= 0;
virtual int exec()= 0;
virtual uint cols()= 0; /* return number of columnss in select */
virtual bool depended()= 0; /* depended from outer select */
enum Item_result type() { return res_type; }
virtual bool check_loop(uint id)= 0;
};
class subselect_single_select_engine: public subselect_engine
{
my_bool prepared; /* simple subselect is prepared */
my_bool optimized; /* simple subselect is optimized */
my_bool executed; /* simple subselect is executed */
st_select_lex *select_lex; /* corresponding select_lex */
JOIN * join; /* corresponding JOIN structure */
public:
subselect_single_select_engine(THD *thd, st_select_lex *select,
select_subselect *result,
Item_subselect *item);
int prepare();
void fix_length_and_dec();
int exec();
uint cols();
bool depended();
bool check_loop(uint id);
};
class subselect_union_engine: public subselect_engine
{
st_select_lex_unit *unit; /* corresponding unit structure */
public:
subselect_union_engine(THD *thd,
st_select_lex_unit *u,
select_subselect *result,
Item_subselect *item);
int prepare();
void fix_length_and_dec();
int exec();
uint cols();
bool depended();
bool check_loop(uint id);
};
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