Query block level hints. More...

#include <opt_hints.h>

Inheritance diagram for Opt_hints_qb:

Public Member Functions
	Opt_hints_qb (Opt_hints opt_hints_arg, MEM_ROOT mem_root_arg, uint select_number_arg)

const LEX_CSTRING *	get_print_name () override

void	append_qb_hint (const THD thd, String str)
	Append query block hint. More...

void	append_name (const THD thd, String str) override
	Append query block name. More...

PT_hint *	get_complex_hints (opt_hints_enum type) override
	Returns pointer to complex hint for a given type. More...

Opt_hints_table *	adjust_table_hints (Table_ref *table)
	Function finds Opt_hints_table object corresponding to table alias in the query block and attaches corresponding key hint objects to appropriate KEY structures. More...

bool	semijoin_enabled (const THD *thd) const
	Returns whether semi-join is enabled for this query block. More...

uint	sj_enabled_strategies (uint opt_switches) const
	Returns bit mask of which semi-join strategies are enabled for this query block. More...

Subquery_strategy	subquery_strategy () const
	Returns which subquery execution strategy has been specified by hints for this query block. More...

void	print_irregular_hints (const THD thd, String str) override
	Function prints hints which are non-standard and don't fit into existing hint infrastructure. More...

const mem_root_deque< Table_ref * > *	sort_tables_in_join_order (THD thd, const mem_root_deque< Table_ref > &join_list, bool toplevel=false)
	Sorts tables from the join list to create a new join list which contains the tables in an order which complies with join order hints. More...

bool	check_join_order_hints (RelationalExpression left, RelationalExpression right, const mem_root_deque< Table_ref * > *join_list)
	Checks if a combination of left and right RelationalExpressions satisfy one or more join order hints. More...

bool	hinted_join_order (PT_qb_level_hint hint, RelationalExpression left, RelationalExpression right, const mem_root_deque< Table_ref > *join_list)
	Checks if a combination of left and right RelationalExpressions satisfy a hint. More...

bool	has_join_order_hints () const
	Checks if any join order hints have been specified in query. More...

void	clear_join_order_hints ()
	Deletes all the join order hints. More...

void	apply_join_order_hints (JOIN *join)
	Checks if join order hints are applicable and applies table dependencies if possible. More...

Public Member Functions inherited from Opt_hints
	Opt_hints (const LEX_CSTRING name_arg, Opt_hints parent_arg, MEM_ROOT *mem_root_arg)

virtual	~Opt_hints ()=default

bool	is_specified (opt_hints_enum type_arg) const

bool	set_switch (bool switch_state_arg, opt_hints_enum type_arg, bool check_parent)
	Function sets switch hint state. More...

bool	get_switch (opt_hints_enum type_arg) const
	Function returns switch hint state. More...

virtual const LEX_CSTRING *	get_name () const

void	set_name (const LEX_CSTRING *name_arg)

Opt_hints *	get_parent () const

virtual void	set_resolved ()

virtual bool	is_resolved (opt_hints_enum type_arg)
	Returns 'resolved' flag value for depending on hint type. More...

virtual void	set_unresolved (opt_hints_enum type_arg)
	Set hint to unresolved state. More...

virtual bool	ignore_print (opt_hints_enum type_arg) const
	If ignore_print() returns true, hint is not printed in Opt_hints::print() function. More...

void	incr_resolved_children ()

Mem_root_array< Opt_hints * > *	child_array_ptr ()

bool	is_all_resolved () const

void	register_child (Opt_hints *hint_arg)

Opt_hints *	find_by_name (const LEX_CSTRING name_arg, const CHARSET_INFO cs) const
	Find hint among lower-level hint objects. More...

void	print (const THD thd, String str, enum_query_type query_type)
	Print all hints except of QB_NAME hint. More...

void	check_unresolved (THD *thd)
	Check if there are any unresolved hint objects and print warnings for them. More...

Private Member Functions
void	register_join_order_hint (PT_qb_level_hint *hint_arg)

Private Attributes
uint	select_number

LEX_CSTRING	sys_name

char	buff [32]

PT_qb_level_hint *	subquery_hint

PT_qb_level_hint *	semijoin_hint

Mem_root_array< PT_qb_level_hint * >	join_order_hints
	Array of join order hints. More...

ulonglong	join_order_hints_ignored
	Bit map of which hints are ignored. More...

Friends
class	PT_qb_level_hint

Detailed Description

Query block level hints.

Constructor & Destructor Documentation

◆ Opt_hints_qb()

Opt_hints_qb::Opt_hints_qb	(	Opt_hints *	opt_hints_arg,
		MEM_ROOT *	mem_root_arg,
		uint	select_number_arg
	)

Member Function Documentation

◆ adjust_table_hints()

Opt_hints_table * Opt_hints_qb::adjust_table_hints ( Table_ref * table )

Function finds Opt_hints_table object corresponding to table alias in the query block and attaches corresponding key hint objects to appropriate KEY structures.

Parameters

table Table reference

Returns: pointer Opt_hints_table object if this object is found, NULL otherwise.

◆ append_name()

void Opt_hints_qb::append_name	(	const THD *	thd,
		String *	str
	)

inlineoverridevirtual

Append query block name.

Parameters

thd	pointer to THD object
str	pointer to String object

Implements Opt_hints.

◆ append_qb_hint()

void Opt_hints_qb::append_qb_hint	(	const THD *	thd,
		String *	str
	)

inline

Append query block hint.

Parameters

thd	pointer to THD object
str	pointer to String object

◆ apply_join_order_hints()

void Opt_hints_qb::apply_join_order_hints ( JOIN * join )

Checks if join order hints are applicable and applies table dependencies if possible.

Parameters

join	JOIN object

◆ check_join_order_hints()

bool Opt_hints_qb::check_join_order_hints	(	RelationalExpression *	left,
		RelationalExpression *	right,
		const mem_root_deque< Table_ref * > *	join_list
	)

Checks if a combination of left and right RelationalExpressions satisfy one or more join order hints.

If the proposed join does not satisfy a hint, the remaining hints are ignored.

Parameters

left	Left side of proposed join
right	Right side of proposed join
join_list	Deque of tables in join

Returns: true if at least one hint matches, false otherwise

◆ clear_join_order_hints()

void Opt_hints_qb::clear_join_order_hints ( )

Deletes all the join order hints.

◆ get_complex_hints()

PT_hint * Opt_hints_qb::get_complex_hints ( opt_hints_enum type )

overridevirtual

Returns pointer to complex hint for a given type.

A complex hint is a hint that has arguments. (It is not just an on/off switch.)

Parameters

type hint type

Returns: pointer to complex hint for a given type.

Reimplemented from Opt_hints.

◆ get_print_name()

const LEX_CSTRING * Opt_hints_qb::get_print_name ( )

inlineoverridevirtual

Reimplemented from Opt_hints.

◆ has_join_order_hints()

bool Opt_hints_qb::has_join_order_hints ( ) const

Checks if any join order hints have been specified in query.

Returns: true if join order hints present, false otherwise.

◆ hinted_join_order()

bool Opt_hints_qb::hinted_join_order	(	PT_qb_level_hint *	hint,
		RelationalExpression *	left,
		RelationalExpression *	right,
		const mem_root_deque< Table_ref * > *	join_list
	)

Checks if a combination of left and right RelationalExpressions satisfy a hint.

Parameters

hint	Hint info
left	Left side of proposed join
right	Right side of proposed join
join_list	Deque of tables in join

Returns: true if at least one hint matches, false otherwise

◆ print_irregular_hints()

void Opt_hints_qb::print_irregular_hints	(	const THD *	thd,
		String *	str
	)

overridevirtual

Function prints hints which are non-standard and don't fit into existing hint infrastructure.

Parameters

thd	pointer to THD object
str	pointer to String object

Reimplemented from Opt_hints.

◆ register_join_order_hint()

void Opt_hints_qb::register_join_order_hint ( PT_qb_level_hint * hint_arg )

inlineprivate

◆ semijoin_enabled()

bool Opt_hints_qb::semijoin_enabled ( const THD * thd ) const

Returns whether semi-join is enabled for this query block.

A SEMIJOIN hint will force semi-join regardless of optimizer_switch settings. A NO_SEMIJOIN hint will only turn off semi-join if the variant with no strategies is used. A SUBQUERY hint will turn off semi-join. If there is no SEMIJOIN/SUBQUERY hint, optimizer_switch setting determines whether SEMIJOIN is used.

Parameters

thd	Pointer to THD object for session. Used to access optimizer_switch

Returns: true if semijoin is enabled

◆ sj_enabled_strategies()

uint Opt_hints_qb::sj_enabled_strategies ( uint opt_switches ) const

Returns bit mask of which semi-join strategies are enabled for this query block.

Parameters

opt_switches Bit map of strategies enabled by optimizer_switch

Returns: Bit mask of strategies that are enabled

◆ sort_tables_in_join_order()

const mem_root_deque< Table_ref * > * Opt_hints_qb::sort_tables_in_join_order	(	THD *	thd,
		const mem_root_deque< Table_ref * > &	join_list,
		bool	toplevel = `false`
	)

Sorts tables from the join list to create a new join list which contains the tables in an order which complies with join order hints.

Parameters

thd	Thread handle.
join_list	Deque of tables in join
toplevel	False for subqueries, true otherwise

Returns: Deque of tables sorted in reverse hinted order.

◆ subquery_strategy()

Subquery_strategy Opt_hints_qb::subquery_strategy ( ) const

Returns which subquery execution strategy has been specified by hints for this query block.

Return values

SUBQ_MATERIALIZATION	Subquery Materialization should be used
SUBQ_EXISTS	In-to-exists execution should be used
UNSPECIFIED	No SUBQUERY hint for this query block

Friends And Related Function Documentation

◆ PT_qb_level_hint

friend class PT_qb_level_hint

friend

Member Data Documentation

◆ buff

char Opt_hints_qb::buff[32]

private

◆ join_order_hints

Mem_root_array<PT_qb_level_hint *> Opt_hints_qb::join_order_hints

private

Array of join order hints.

◆ join_order_hints_ignored

ulonglong Opt_hints_qb::join_order_hints_ignored

private

Bit map of which hints are ignored.

◆ select_number

uint Opt_hints_qb::select_number

private

◆ semijoin_hint

PT_qb_level_hint * Opt_hints_qb::semijoin_hint

private

◆ subquery_hint

PT_qb_level_hint* Opt_hints_qb::subquery_hint

private

◆ sys_name

LEX_CSTRING Opt_hints_qb::sys_name

private

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

sql/opt_hints.h
sql/opt_hints.cc

Public Member Functions

Private Member Functions

Private Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

◆ Opt_hints_qb()

Member Function Documentation

◆ adjust_table_hints()

◆ append_name()

◆ append_qb_hint()

◆ apply_join_order_hints()

◆ check_join_order_hints()

◆ clear_join_order_hints()

◆ get_complex_hints()

◆ get_print_name()

◆ has_join_order_hints()

◆ hinted_join_order()

◆ print_irregular_hints()

◆ register_join_order_hint()

◆ semijoin_enabled()

◆ sj_enabled_strategies()

◆ sort_tables_in_join_order()

◆ subquery_strategy()

Friends And Related Function Documentation

◆ PT_qb_level_hint

Member Data Documentation

◆ buff

◆ join_order_hints

◆ join_order_hints_ignored

◆ select_number

◆ semijoin_hint

◆ subquery_hint

◆ sys_name