Inheritance 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
Friends
class	subselect_hash_sj_engine
class	Item_in_subselect

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.

void subselect_single_select_engine::cleanup ( ) [virtual]

Cleanup engine after complete query execution, free all resources.

Implements subselect_engine.

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.

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.

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

Public Member Functions

Friends

Member Function Documentation