subselect_single_select_engine Class Reference

Inheritance diagram for subselect_single_select_engine:

Collaboration diagram for subselect_single_select_engine:

Public Member Functions
	subselect_single_select_engine (st_select_lex *select, select_result_interceptor *result, Item_subselect *item)
virtual void	cleanup ()
virtual bool	prepare ()
virtual void	fix_length_and_dec (Item_cache **row)
virtual bool	exec ()
virtual uint	cols () const
virtual uint8	uncacheable () const
virtual void	exclude ()
virtual table_map	upper_select_const_tables () const
virtual void	print (String *str, enum_query_type query_type)
virtual bool	change_result (Item_subselect *si, select_result_interceptor *result)
virtual bool	no_tables () const
virtual bool	may_be_null () const
virtual bool	is_executed () const
virtual enum_engine_type	engine_type () const
Public Member Functions inherited from subselect_engine
	subselect_engine (Item_subselect *si, select_result_interceptor *res)
void	set_thd_for_result ()
	Sets "thd" for 'result'. Should be called before prepare()
virtual enum Item_result	type () const
virtual enum_field_types	field_type () const
const Item_subselect *	get_item () const

Friends
class	subselect_hash_sj_engine
class	Item_in_subselect

Additional Inherited Members
Public Types inherited from subselect_engine
enum	enum_engine_type {   ABSTRACT_ENGINE, SINGLE_SELECT_ENGINE, UNION_ENGINE, UNIQUESUBQUERY_ENGINE,   INDEXSUBQUERY_ENGINE, HASH_SJ_ENGINE }
Static Public Member Functions inherited from subselect_engine
static table_map	calc_const_tables (TABLE_LIST *)
Protected Member Functions inherited from subselect_engine
void	set_row (List< Item > &item_list, Item_cache **row)
Protected Attributes inherited from subselect_engine
select_result_interceptor *	result
Item_subselect *	item
enum Item_result	res_type
enum_field_types	res_field_type
bool	maybe_null

Detailed Description

Definition at line 586 of file item_subselect.h.

Member Function Documentation

bool subselect_single_select_engine::change_result ( Item_subselect *  si, select_result_interceptor *  res  )

virtual

change select_result object of engine.

Parameters

si	new subselect Item
res	new select_result object

Return values

FALSE	OK
TRUE	error

Implements subselect_engine.

Definition at line 3349 of file item_subselect.cc.

void subselect_single_select_engine::cleanup ( )

virtual

Cleanup engine after complete query execution, free all resources.

Implements subselect_engine.

Definition at line 2558 of file item_subselect.cc.

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bool subselect_single_select_engine::no_tables ( ) const

virtual

Report about presence of tables in subquery.

Return values

TRUE	there are not tables used in subquery
FALSE	there are some tables in subquery

Implements subselect_engine.

Definition at line 3408 of file item_subselect.cc.

bool subselect_single_select_engine::prepare ( )

virtual

Create and prepare the JOIN object that represents the query execution plan for the subquery.

This method is called from Item_subselect::fix_fields. For prepared statements it is called both during the PREPARE and EXECUTE phases in the following ways:

• During PREPARE the optimizer needs some properties (join->fields_list.elements) of the JOIN to proceed with preparation of the remaining query (namely to complete ::fix_fields for the subselect related classes. In the end of PREPARE the JOIN is deleted.
• When we EXECUTE the query, Item_subselect::fix_fields is called again, and the JOIN object is re-created again, prepared and executed. In the end of execution it is deleted. In all cases the JOIN is created in runtime memory (not in the permanent memory root).

Todo:

Re-check what properties of 'join' are needed during prepare, and see if we can avoid creating a JOIN during JOIN::prepare of the outer join.

Return values

0	if success
1	if error

Implements subselect_engine.

Definition at line 2618 of file item_subselect.cc.

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The documentation for this class was generated from the following files:

• sql/item_subselect.h
• sql/item_subselect.cc