diff options
Diffstat (limited to 'sql/item_subselect.h')
| -rw-r--r-- | sql/item_subselect.h | 211 |
1 files changed, 211 insertions, 0 deletions
diff --git a/sql/item_subselect.h b/sql/item_subselect.h new file mode 100644 index 00000000000..33f82982708 --- /dev/null +++ b/sql/item_subselect.h @@ -0,0 +1,211 @@ +/* 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 +{ + 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; + + 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; } +}; + +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); + virtual int prepare(); + virtual void fix_length_and_dec(); + virtual int exec(); + virtual uint cols(); + virtual bool depended(); +}; + +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); + virtual int prepare(); + virtual void fix_length_and_dec(); + virtual int exec(); + virtual uint cols(); + virtual bool depended(); +}; |