~drizzle-trunk/drizzle/development

/* 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_result_interceptor;

class subselect_engine;

class subselect_hash_sj_engine;

class Item_bool_func2;

class Cached_item;

/* base class for subselects */

class Item_subselect :public Item_result_field

{

  my_bool value_assigned; /* value already assigned to subselect */

public:

  /* thread handler, will be assigned in fix_fields only */

  THD *thd;

  /* substitution instead of subselect in case of optimization */

  Item *substitution;

  /* unit of subquery */

public:

  st_select_lex_unit *unit;

protected:

  /* 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 to pass a pointer

    to subselect Item class to select_result_interceptor's constructor.

  */

  virtual void init (st_select_lex *select_lex,

		     select_result_interceptor *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();

  virtual void print(String *str, enum_query_type query_type);

  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; }

  bool walk(Item_processor processor, bool walk_subquery, uchar *arg);

  /**

    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_result_interceptor;

  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();

  int64_t 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);

  virtual void print(String *str, enum_query_type query_type);

  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;}

  int64_t val_int();

  double val_real();

  String *val_str(String*);

  my_decimal *val_decimal(my_decimal *);

  bool val_bool();

  void fix_length_and_dec();

  virtual void print(String *str, enum_query_type query_type);

  friend class select_exists_subselect;

  friend class subselect_uniquesubquery_engine;

  friend class subselect_indexsubquery_engine;

};

/**

  Representation of IN subquery predicates of the form

  "left_expr IN (SELECT ...)".

  @detail

  This class has: 

   - A "subquery execution engine" (as a subclass of Item_subselect) that 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

{

public:

  Item *left_expr;

protected:

  /*

    Cache of the left operand of the subquery predicate. Allocated in the

    runtime memory root, for each execution, thus need not be freed.

  */

  List<Cached_item> *left_expr_cache;

  bool first_execution;

  /*

    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;

public:

  /* Used to trigger on/off conditions that were pushed down to subselect */

  bool *pushed_cond_guards;

  /* Priority of this predicate in the convert-to-semi-join-nest process. */

  int sj_convert_priority;

  /* 

    Location of the subquery predicate. It is either

     - pointer to join nest if the subquery predicate is in the ON expression

     - (TABLE_LIST*)1 if the predicate is in the WHERE.

  */

  TABLE_LIST *expr_join_nest;

  /* The method chosen to execute the IN predicate.  */

  enum enum_exec_method {

    NOT_TRANSFORMED, /* No execution method was chosen for this IN. */

    SEMI_JOIN,   /* IN was converted to semi-join nest and should be removed. */

    IN_TO_EXISTS, /* IN was converted to correlated EXISTS. */

    MATERIALIZATION /* IN will be executed via subquery materialization. */

  };

  enum_exec_method exec_method;

  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(), left_expr_cache(0), first_execution(true),

    optimizer(0), abort_on_null(0), pushed_cond_guards(NULL),

    exec_method(NOT_TRANSFORMED), upper_item(0)

  {}

  void cleanup();

  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);

  trans_res single_value_in_to_exists_transformer(JOIN * join,

                                                  Comp_creator *func);

  trans_res row_value_in_to_exists_transformer(JOIN * join);

  virtual bool exec();

  int64_t val_int();

  double val_real();

  String *val_str(String*);

  my_decimal *val_decimal(my_decimal *);

  void update_null_value () { (void) val_bool(); }

  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);

  virtual void print(String *str, enum_query_type query_type);

  bool fix_fields(THD *thd, Item **ref);

  bool setup_engine();

  bool init_left_expr_cache();

  bool is_expensive_processor(uchar *arg);

  friend class Item_ref_null_helper;

  friend class Item_is_not_null_test;

  friend class Item_in_optimizer;

  friend class subselect_indexsubquery_engine;

  friend class subselect_hash_sj_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);

  virtual void print(String *str, enum_query_type query_type);

};

class subselect_engine: public Sql_alloc

{

protected:

  select_result_interceptor *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:

  enum enum_engine_type {ABSTRACT_ENGINE, SINGLE_SELECT_ENGINE,

                         UNION_ENGINE, UNIQUESUBQUERY_ENGINE,

                         INDEXSUBQUERY_ENGINE, HASH_SJ_ENGINE};

  subselect_engine(Item_subselect *si, select_result_interceptor *res)

    :thd(0)

  {

    result= res;

    item= si;

    res_type= STRING_RESULT;

    res_field_type= MYSQL_TYPE_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, enum_query_type query_type)= 0;

  virtual bool change_result(Item_subselect *si,

                             select_result_interceptor *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;

  virtual enum_engine_type engine_type() { return ABSTRACT_ENGINE; }

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_result_interceptor *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();

  virtual void print (String *str, enum_query_type query_type);

  bool change_result(Item_subselect *si, select_result_interceptor *result);

  bool no_tables();

  bool may_be_null();

  bool is_executed() const { return executed; }

  bool no_rows();

  virtual enum_engine_type engine_type() { return SINGLE_SELECT_ENGINE; }

  friend class subselect_hash_sj_engine;

  friend class Item_in_subselect;

};

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_result_interceptor *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();

  virtual void print (String *str, enum_query_type query_type);

  bool change_result(Item_subselect *si, select_result_interceptor *result);

  bool no_tables();

  bool is_executed() const;

  bool no_rows();

  virtual enum_engine_type engine_type() { return UNION_ENGINE; }

};

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);

  }

  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; }

  virtual void print (String *str, enum_query_type query_type);

  bool change_result(Item_subselect *si, select_result_interceptor *result);

  bool no_tables();

  int scan_table();

  bool copy_ref_key();

  bool no_rows() { return empty_result_set; }

  virtual enum_engine_type engine_type() { return UNIQUESUBQUERY_ENGINE; }

};

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();

  virtual void print (String *str, enum_query_type query_type);

  virtual enum_engine_type engine_type() { return INDEXSUBQUERY_ENGINE; }

};

inline bool Item_subselect::is_evaluated() const

{

  return engine->is_executed();

}

inline bool Item_subselect::is_uncacheable() const

{

  return engine->uncacheable();

}

/**

  Compute an IN predicate via a hash semi-join. The subquery is materialized

  during the first evaluation of the IN predicate. The IN predicate is executed

  via the functionality inherited from subselect_uniquesubquery_engine.

*/

class subselect_hash_sj_engine: public subselect_uniquesubquery_engine

{

protected:

  /* TRUE if the subquery was materialized into a temp table. */

  bool is_materialized;

  /*

    The old engine already chosen at parse time and stored in permanent memory.

    Through this member we can re-create and re-prepare materialize_join for

    each execution of a prepared statement. We akso resuse the functionality

    of subselect_single_select_engine::[prepare | cols].

  */

  subselect_single_select_engine *materialize_engine;

  /*

    QEP to execute the subquery and materialize its result into a

    temporary table. Created during the first call to exec().

  */

  JOIN *materialize_join;

  /* Temp table context of the outer select's JOIN. */

  TMP_TABLE_PARAM *tmp_param;

public:

  subselect_hash_sj_engine(THD *thd, Item_subselect *in_predicate,

                               subselect_single_select_engine *old_engine)

    :subselect_uniquesubquery_engine(thd, NULL, in_predicate, NULL),

    is_materialized(false), materialize_engine(old_engine),

    materialize_join(NULL), tmp_param(NULL)

  {}

  ~subselect_hash_sj_engine();

  bool init_permanent(List<Item> *tmp_columns);

  bool init_runtime();

  void cleanup();

  int prepare() { return 0; }

  int exec();

  virtual void print (String *str, enum_query_type query_type);

  uint cols()

  {

    return materialize_engine->cols();

  }

  virtual enum_engine_type engine_type() { return HASH_SJ_ENGINE; }

};