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/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
*
* Copyright (C) 2008 Sun Microsystems, Inc.
*
* 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#pragma once
#include <drizzled/comp_creator.h>
#include <drizzled/item/ref.h>
#include <drizzled/item/field.h>
#include <drizzled/item/bin_string.h>
#include <drizzled/util/test.h>
namespace drizzled {
class Item_subselect :public Item_result_field
{
bool value_assigned; /* value already assigned to subselect */
public:
/* thread handler, will be assigned in fix_fields only */
Session *session;
/* substitution instead of subselect in case of optimization */
Item *substitution;
/* unit of subquery */
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) */
uint32_t 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 (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(Session *session, 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(Session *session);
void update_used_tables();
virtual 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; }
bool walk(Item_processor processor, bool walk_subquery, unsigned char *arg);
/**
Get the Select_Lex structure associated with this Item.
@return the Select_Lex structure associated with this Item
*/
Select_Lex* get_select_lex();
friend class select_result_interceptor;
friend class Item_in_optimizer;
friend bool Item_field::fix_fields(Session *, Item **);
friend int Item_field::fix_outer_field(Session *, Field **, Item **);
friend bool Item_ref::fix_fields(Session *, Item **);
friend void mark_select_range_as_dependent(Session*,
Select_Lex*, Select_Lex*,
Field*, Item*, Item_ident*);
};
/* single value subselect */
class Item_singlerow_subselect :public Item_subselect
{
protected:
Item_cache *value, **row;
public:
Item_singlerow_subselect(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(uint32_t i, Item* item);
double val_real();
int64_t val_int ();
String *val_str (String *);
type::Decimal *val_decimal(type::Decimal *);
bool val_bool();
enum Item_result result_type() const;
enum_field_types field_type() const;
void fix_length_and_dec();
uint32_t cols();
Item* element_index(uint32_t i) { return reinterpret_cast<Item*>(row[i]); }
Item** addr(uint32_t i) { return (Item**)row + i; }
bool check_cols(uint32_t 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.
*/
Select_Lex* invalidate_and_restore_select_lex();
friend class select_singlerow_subselect;
};
/* used in static ALL/ANY optimization */
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(Session *session, Item_subselect *parent,
Select_Lex *select_lex, bool max);
virtual 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(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*);
type::Decimal *val_decimal(type::Decimal *);
bool val_bool();
void fix_length_and_dec();
virtual void print(String *str);
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
- (TableList*)1 if the predicate is in the WHERE.
*/
TableList *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, Select_Lex *select_lex);
Item_in_subselect()
:
Item_exists_subselect(),
left_expr(NULL),
left_expr_cache(NULL),
first_execution(true),
optimizer(NULL),
abort_on_null(false),
pushed_cond_guards(NULL),
sj_convert_priority(0),
expr_join_nest(NULL),
exec_method(NOT_TRANSFORMED),
upper_item(NULL)
{}
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, const Comp_creator *func);
trans_res single_value_transformer(Join *join, const Comp_creator *func);
trans_res row_value_transformer(Join * join);
trans_res single_value_in_to_exists_transformer(Join * join,
const 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*);
type::Decimal *val_decimal(type::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(Select_Lex_Unit *unit);
virtual void print(String *str);
bool fix_fields(Session *session, Item **ref);
bool setup_engine();
bool init_left_expr_cache();
bool is_expensive_processor(unsigned char *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,
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);
};
class subselect_engine: public memory::SqlAlloc
{
protected:
select_result_interceptor *result; /* results storage class */
Session *session; /* pointer to current Session */
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)
:session(NULL)
{
result= res;
item= si;
res_type= STRING_RESULT;
res_field_type= DRIZZLE_TYPE_VARCHAR;
maybe_null= 0;
}
virtual ~subselect_engine() {} // to satisfy compiler
virtual void cleanup()= 0;
/*
Also sets "session" for subselect_engine::result.
Should be called before prepare().
*/
void set_session(Session *session_arg);
Session * get_session() { return session; }
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 uint32_t cols()= 0; /* return number of columns in select */
virtual bool uncacheable()= 0; /* query is uncacheable */
virtual bool uncacheable(uint32_t bit_pos)= 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(TableList *);
virtual void print(String *str)= 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
{
bool prepared; /* simple subselect is prepared */
bool optimized; /* simple subselect is optimized */
bool executed; /* simple subselect is executed */
Select_Lex *select_lex; /* corresponding select_lex */
Join * join; /* corresponding JOIN structure */
public:
subselect_single_select_engine(Select_Lex *select,
select_result_interceptor *result,
Item_subselect *item);
void cleanup();
int prepare();
void fix_length_and_dec(Item_cache** row);
int exec();
uint32_t cols();
bool uncacheable();
bool uncacheable(uint32_t bit_pos);
void exclude();
table_map upper_select_const_tables();
virtual void print (String *str);
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; }
bool save_join_if_explain();
friend class subselect_hash_sj_engine;
friend class Item_in_subselect;
};
class subselect_union_engine: public subselect_engine
{
Select_Lex_Unit *unit; /* corresponding unit structure */
public:
subselect_union_engine(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();
uint32_t cols();
bool uncacheable();
bool uncacheable(uint32_t bit_pos);
void exclude();
table_map upper_select_const_tables();
virtual void print (String *str);
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; }
};
/*
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:
JoinTable *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 Session because it will be called after Join::prepare
subselect_uniquesubquery_engine(Session *session_arg, JoinTable *tab_arg,
Item_subselect *subs, Item *where)
:subselect_engine(subs, 0), tab(tab_arg), cond(where)
{
set_session(session_arg);
}
void cleanup();
int prepare();
void fix_length_and_dec(Item_cache** row);
int exec();
uint32_t cols() { return 1; }
bool uncacheable() { return true; }
bool uncacheable(uint32_t) { return true; }
void exclude();
table_map upper_select_const_tables() { return 0; }
virtual void print (String *str);
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 Session because it will be called after Join::prepare
subselect_indexsubquery_engine(Session *session_arg, JoinTable *tab_arg,
Item_subselect *subs, Item *where,
Item *having_arg, bool chk_null)
:subselect_uniquesubquery_engine(session_arg, tab_arg, subs, where),
check_null(chk_null),
having(having_arg)
{}
int exec();
virtual void print (String *str);
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(Session *session_in, Item_subselect *in_predicate,
subselect_single_select_engine *old_engine)
:subselect_uniquesubquery_engine(session_in, 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);
uint32_t cols()
{
return materialize_engine->cols();
}
virtual enum_engine_type engine_type() { return HASH_SJ_ENGINE; }
};
} /* namespace drizzled */
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