/* 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; version 2 of the License. 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 USE_PRAGMA_INTERFACE #pragma interface /* gcc class implementation */ #endif class st_select_lex; class st_select_lex_unit; class JOIN; class select_subselect; class subselect_engine; class Item_bool_func2; /* base class for subselects */ class Item_subselect :public Item_result_field { my_bool value_assigned; /* value already assigned to subselect */ protected: /* thread handler, will be assigned in fix_fields only */ THD *thd; /* substitution instead of subselect in case of optimization */ Item *substitution; /* unit of subquery */ st_select_lex_unit *unit; /* engine that perform execution of subselect (single select or union) */ subselect_engine *engine; /* old engine if engine was changed */ subselect_engine *old_engine; /* cache of used external tables */ table_map used_tables_cache; /* allowed number of columns (1 for single value subqueries) */ uint max_columns; /* where subquery is placed */ enum_parsing_place parsing_place; /* work with 'substitution' */ bool have_to_be_excluded; /* cache of constant state */ bool const_item_cache; public: /* changed engine indicator */ bool engine_changed; /* subquery is transformed */ bool changed; /* TRUE <=> The underlying SELECT is correlated w.r.t some ancestor select */ bool is_correlated; enum trans_res {RES_OK, RES_REDUCE, RES_ERROR}; enum subs_type {UNKNOWN_SUBS, SINGLEROW_SUBS, EXISTS_SUBS, IN_SUBS, ALL_SUBS, ANY_SUBS}; Item_subselect(); virtual subs_type substype() { return UNKNOWN_SUBS; } /* 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. */ virtual void init (st_select_lex *select_lex, select_subselect *result); ~Item_subselect(); void cleanup(); virtual void reset() { null_value= 1; } virtual trans_res select_transformer(JOIN *join); bool assigned() { return value_assigned; } void assigned(bool a) { value_assigned= a; } enum Type type() const; bool is_null() { update_null_value(); return null_value; } bool fix_fields(THD *thd, Item **ref); virtual bool exec(); virtual void fix_length_and_dec(); table_map used_tables() const; table_map not_null_tables() const { return 0; } bool const_item() const; inline table_map get_used_tables_cache() { return used_tables_cache; } inline bool get_const_item_cache() { return const_item_cache; } Item *get_tmp_table_item(THD *thd); void update_used_tables(); void print(String *str); virtual bool have_guarded_conds() { return FALSE; } bool change_engine(subselect_engine *eng) { old_engine= engine; engine= eng; engine_changed= 1; return eng == 0; } /* True if this subquery has been already evaluated. Implemented only for single select and union subqueries only. */ bool is_evaluated() const; bool is_uncacheable() const; /* Used by max/min subquery to initialize value presence registration mechanism. Engine call this method before rexecution query. */ virtual void reset_value_registration() {} enum_parsing_place place() { return parsing_place; } /** Get the SELECT_LEX structure associated with this Item. @return the SELECT_LEX structure associated with this Item */ st_select_lex* get_select_lex(); friend class select_subselect; friend class Item_in_optimizer; friend bool Item_field::fix_fields(THD *, Item **); friend int Item_field::fix_outer_field(THD *, Field **, Item **); friend bool Item_ref::fix_fields(THD *, Item **); friend void mark_select_range_as_dependent(THD*, st_select_lex*, st_select_lex*, Field*, Item*, Item_ident*); }; /* single value subselect */ class Item_cache; class Item_singlerow_subselect :public Item_subselect { protected: Item_cache *value, **row; public: Item_singlerow_subselect(st_select_lex *select_lex); Item_singlerow_subselect() :Item_subselect(), value(0), row (0) {} void cleanup(); subs_type substype() { return SINGLEROW_SUBS; } void reset(); trans_res select_transformer(JOIN *join); void store(uint i, Item* item); double val_real(); longlong val_int (); String *val_str (String *); my_decimal *val_decimal(my_decimal *); bool val_bool(); enum Item_result result_type() const; enum_field_types field_type() const; void fix_length_and_dec(); uint cols(); Item* element_index(uint i) { return my_reinterpret_cast(Item*)(row[i]); } Item** addr(uint i) { return (Item**)row + i; } bool check_cols(uint c); bool null_inside(); void bring_value(); /** This method is used to implement a special case of semantic tree rewriting, mandated by a SQL:2003 exception in the specification. The only caller of this method is handle_sql2003_note184_exception(), see the code there for more details. Note that this method breaks the object internal integrity, by removing it's association with the corresponding SELECT_LEX, making this object orphan from the parse tree. No other method, beside the destructor, should be called on this object, as it is now invalid. @return the SELECT_LEX structure that was given in the constructor. */ st_select_lex* invalidate_and_restore_select_lex(); friend class select_singlerow_subselect; }; /* used in static ALL/ANY optimization */ class select_max_min_finder_subselect; class Item_maxmin_subselect :public Item_singlerow_subselect { protected: bool max; bool was_values; // Set if we have found at least one row public: Item_maxmin_subselect(THD *thd, Item_subselect *parent, st_select_lex *select_lex, bool max); void print(String *str); void cleanup(); bool any_value() { return was_values; } void register_value() { was_values= TRUE; } void reset_value_registration() { was_values= FALSE; } }; /* exists subselect */ class Item_exists_subselect :public Item_subselect { protected: bool value; /* value of this item (boolean: exists/not-exists) */ public: Item_exists_subselect(st_select_lex *select_lex); Item_exists_subselect(): Item_subselect() {} subs_type substype() { return EXISTS_SUBS; } void reset() { value= 0; } enum Item_result result_type() const { return INT_RESULT;} longlong val_int(); double val_real(); String *val_str(String*); my_decimal *val_decimal(my_decimal *); bool val_bool(); void fix_length_and_dec(); void print(String *str); friend class select_exists_subselect; friend class subselect_uniquesubquery_engine; friend class subselect_indexsubquery_engine; }; /* IN subselect: this represents "left_exr IN (SELECT ...)" This class has: - (as a descendant of Item_subselect) a "subquery execution engine" which allows it to evaluate subqueries. (and this class participates in execution by having was_null variable where part of execution result is stored. - Transformation methods (todo: more on this). This class is not used directly, it is "wrapped" into Item_in_optimizer which provides some small bits of subquery evaluation. */ class Item_in_subselect :public Item_exists_subselect { protected: Item *left_expr; /* expr & optimizer used in subselect rewriting to store Item for all JOIN in UNION */ Item *expr; Item_in_optimizer *optimizer; bool was_null; bool abort_on_null; bool transformed; public: /* Used to trigger on/off conditions that were pushed down to subselect */ bool *pushed_cond_guards; bool *get_cond_guard(int i) { return pushed_cond_guards ? pushed_cond_guards + i : NULL; } void set_cond_guard_var(int i, bool v) { if ( pushed_cond_guards) pushed_cond_guards[i]= v; } bool have_guarded_conds() { return test(pushed_cond_guards); } Item_func_not_all *upper_item; // point on NOT/NOP before ALL/SOME subquery Item_in_subselect(Item * left_expr, st_select_lex *select_lex); Item_in_subselect() :Item_exists_subselect(), optimizer(0), abort_on_null(0), transformed(0), pushed_cond_guards(NULL), upper_item(0) {} subs_type substype() { return IN_SUBS; } void reset() { value= 0; null_value= 0; was_null= 0; } trans_res select_transformer(JOIN *join); trans_res select_in_like_transformer(JOIN *join, Comp_creator *func); trans_res single_value_transformer(JOIN *join, Comp_creator *func); trans_res row_value_transformer(JOIN * join); longlong val_int(); double val_real(); String *val_str(String*); my_decimal *val_decimal(my_decimal *); bool val_bool(); void top_level_item() { abort_on_null=1; } inline bool is_top_level_item() { return abort_on_null; } bool test_limit(st_select_lex_unit *unit); void print(String *str); bool fix_fields(THD *thd, Item **ref); friend class Item_ref_null_helper; friend class Item_is_not_null_test; friend class subselect_indexsubquery_engine; }; /* ALL/ANY/SOME subselect */ class Item_allany_subselect :public Item_in_subselect { public: chooser_compare_func_creator func_creator; Comp_creator *func; bool all; Item_allany_subselect(Item * left_expr, chooser_compare_func_creator fc, st_select_lex *select_lex, bool all); // only ALL subquery has upper not subs_type substype() { return all?ALL_SUBS:ANY_SUBS; } trans_res select_transformer(JOIN *join); void print(String *str); }; class subselect_engine: public Sql_alloc { 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 */ enum_field_types res_field_type; /* column type of the results */ bool maybe_null; /* may be null (first item in select) */ public: subselect_engine(Item_subselect *si, select_subselect *res) :thd(0) { result= res; item= si; res_type= STRING_RESULT; res_field_type= FIELD_TYPE_VAR_STRING; maybe_null= 0; } virtual ~subselect_engine() {}; // to satisfy compiler virtual void cleanup()= 0; /* Also sets "thd" for subselect_engine::result. Should be called before prepare(). */ void set_thd(THD *thd_arg); THD * get_thd() { return thd; } virtual int prepare()= 0; virtual void fix_length_and_dec(Item_cache** row)= 0; /* Execute the engine SYNOPSIS exec() DESCRIPTION Execute the engine. The result of execution is subquery value that is either captured by previously set up select_result-based 'sink' or stored somewhere by the exec() method itself. A required side effect: If at least one pushed-down predicate is disabled, subselect_engine->no_rows() must return correct result after the exec() call. RETURN 0 - OK 1 - Either an execution error, or the engine was "changed", and the caller should call exec() again for the new engine. */ virtual int exec()= 0; virtual uint cols()= 0; /* return number of columns in select */ virtual uint8 uncacheable()= 0; /* query is uncacheable */ enum Item_result type() { return res_type; } enum_field_types field_type() { return res_field_type; } virtual void exclude()= 0; virtual bool may_be_null() { return maybe_null; }; virtual table_map upper_select_const_tables()= 0; static table_map calc_const_tables(TABLE_LIST *); virtual void print(String *str)= 0; virtual bool change_result(Item_subselect *si, select_subselect *result)= 0; virtual bool no_tables()= 0; virtual bool is_executed() const { return FALSE; } /* Check if subquery produced any rows during last query execution */ virtual bool no_rows() = 0; protected: void set_row(List<Item> &item_list, Item_cache **row); }; 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(st_select_lex *select, select_subselect *result, Item_subselect *item); void cleanup(); int prepare(); void fix_length_and_dec(Item_cache** row); int exec(); uint cols(); uint8 uncacheable(); void exclude(); table_map upper_select_const_tables(); void print (String *str); bool change_result(Item_subselect *si, select_subselect *result); bool no_tables(); bool may_be_null(); bool is_executed() const { return executed; } bool no_rows(); }; class subselect_union_engine: public subselect_engine { st_select_lex_unit *unit; /* corresponding unit structure */ public: subselect_union_engine(st_select_lex_unit *u, select_subselect *result, Item_subselect *item); void cleanup(); int prepare(); void fix_length_and_dec(Item_cache** row); int exec(); uint cols(); uint8 uncacheable(); void exclude(); table_map upper_select_const_tables(); void print (String *str); bool change_result(Item_subselect *si, select_subselect *result); bool no_tables(); bool is_executed() const; bool no_rows(); }; struct st_join_table; /* A subquery execution engine that evaluates the subquery by doing one index lookup in a unique index. This engine is used to resolve subqueries in forms outer_expr IN (SELECT tbl.unique_key FROM tbl WHERE subq_where) or, tuple-based: (oe1, .. oeN) IN (SELECT uniq_key_part1, ... uniq_key_partK FROM tbl WHERE subqwhere) i.e. the subquery is a single table SELECT without GROUP BY, aggregate functions, etc. */ class subselect_uniquesubquery_engine: public subselect_engine { protected: st_join_table *tab; Item *cond; /* The WHERE condition of subselect */ /* TRUE<=> last execution produced empty set. Valid only when left expression is NULL. */ bool empty_result_set; bool null_keypart; /* TRUE <=> constructed search tuple has a NULL */ public: // constructor can assign THD because it will be called after JOIN::prepare subselect_uniquesubquery_engine(THD *thd_arg, st_join_table *tab_arg, Item_subselect *subs, Item *where) :subselect_engine(subs, 0), tab(tab_arg), cond(where) { set_thd(thd_arg); } ~subselect_uniquesubquery_engine(); void cleanup(); int prepare(); void fix_length_and_dec(Item_cache** row); int exec(); uint cols() { return 1; } uint8 uncacheable() { return UNCACHEABLE_DEPENDENT; } void exclude(); table_map upper_select_const_tables() { return 0; } void print (String *str); bool change_result(Item_subselect *si, select_subselect *result); bool no_tables(); int scan_table(); bool copy_ref_key(); bool no_rows() { return empty_result_set; } }; class subselect_indexsubquery_engine: public subselect_uniquesubquery_engine { /* FALSE for 'ref', TRUE for 'ref-or-null'. */ bool check_null; /* The "having" clause. This clause (further reffered to as "artificial having") was inserted by subquery transformation code. It contains Item(s) that have a side-effect: they record whether the subquery has produced a row with NULL certain components. We need to use it for cases like (oe1, oe2) IN (SELECT t.key, t.no_key FROM t1) where we do index lookup on t.key=oe1 but need also to check if there was a row such that t.no_key IS NULL. NOTE: This is currently here and not in the uniquesubquery_engine. Ideally it should have been in uniquesubquery_engine in order to allow execution of subqueries like (oe1, oe2) IN (SELECT primary_key, non_key_maybe_null_field FROM tbl) We could use uniquesubquery_engine for the first component and let Item_is_not_null_test( non_key_maybe_null_field) to handle the second. However, subqueries like the above are currently not handled by index lookup-based subquery engines, the engine applicability check misses them: it doesn't switch the engine for case of artificial having and [eq_]ref access (only for artifical having + ref_or_null or no having). The above example subquery is handled as a full-blown SELECT with eq_ref access to one table. Due to this limitation, the "artificial having" currently needs to be checked by only in indexsubquery_engine. */ Item *having; public: // constructor can assign THD because it will be called after JOIN::prepare subselect_indexsubquery_engine(THD *thd_arg, st_join_table *tab_arg, Item_subselect *subs, Item *where, Item *having_arg, bool chk_null) :subselect_uniquesubquery_engine(thd_arg, tab_arg, subs, where), check_null(chk_null), having(having_arg) {} int exec(); void print (String *str); }; inline bool Item_subselect::is_evaluated() const { return engine->is_executed(); } inline bool Item_subselect::is_uncacheable() const { return engine->uncacheable(); }