The class Item_multi_eq is used to represent conjunctions of equality predicates of the form field1 = field2, and field = const in where conditions and on join conditions. More...

#include <item_cmpfunc.h>

Inheritance diagram for Item_multi_eq:

[legend]

Classes
class	ConstFieldProxy

class	FieldProxy

Public Member Functions
	~Item_multi_eq () override

	Item_multi_eq (Item_field lhs_field, Item_field rhs_field)

	Item_multi_eq (Item const_item, Item_field field)

	Item_multi_eq (Item_multi_eq *item_multi_eq)

	Item_multi_eq (const Item_multi_eq &)=delete

Item_multi_eq	operator= (const Item_multi_eq &)=delete

	Item_multi_eq (const Item_multi_eq &&)=delete

Item_multi_eq	operator= (const Item_multi_eq &&)=delete

Item *	const_arg () const
	Returns the constant Item that this multi equality is equal to(if any). More...

void	set_const_arg (Item *const_item)

bool	add (THD thd, Item const_item, Item_field *field)

bool	add (THD thd, Item const_item)

void	add (Item_field *field)

uint	members ()

bool	contains (const Item_field *field) const
	Check whether a field is referred in the multiple equality. More...

Item_field *	get_first ()
	Get the first field of multiple equality, use for semantic checking. More...

Item_field *	get_subst_item (const Item_field *field)
	Get item that can be substituted for the supplied item. More...

bool	merge (THD thd, Item_multi_eq item)
	Add members of another Item_multi_eq object. More...

bool	update_const (THD *thd)
	Check appearance of new constant items in the multiple equality object. More...

enum Functype	functype () const override

longlong	val_int () override

const char *	func_name () const override

optimize_type	select_optimize (const THD *) override

bool	cast_incompatible_args (uchar *) override
	Wrap incompatible arguments in CAST nodes to the expected data types. More...

bool	contains_only_equi_join_condition () const override
	Whether this Item is an equi-join condition. More...

template<typename Node_cmp_func >
void	sort (Node_cmp_func compare)
	Order field items in multiple equality according to a sorting criteria. More...

FieldProxy	get_fields ()

ConstFieldProxy	get_fields () const

bool	resolve_type (THD *) override
	Resolve type-related information for this item, such as result field type, maximum size, precision, signedness, character set and collation. More...

bool	fix_fields (THD thd, Item *ref) override

void	update_used_tables () override
	Updates used tables, not null tables information and accumulates properties up the item tree, cf. More...

bool	walk (Item_processor processor, enum_walk walk, uchar *arg) override
	Traverses a tree of Items in prefix and/or postfix order. More...

void	print (const THD thd, String str, enum_query_type query_type) const override
	This method is used for to: More...

bool	eq_specific (const Item *item) const override
	Provide a more specific equality check for a function. More...

const CHARSET_INFO *	compare_collation () const override

bool	equality_substitution_analyzer (uchar **) override

Item *	equality_substitution_transformer (uchar *arg) override
	Transform an Item_multi_eq object after having added a table that represents a materialized semi-join. More...

float	get_filtering_effect (THD thd, table_map filter_for_table, table_map read_tables, const MY_BITMAP fields_to_ignore, double rows_in_table) override
	temporary area used for constant folding More...

Public Member Functions inherited from Item_bool_func
bool	is_bool_func () const override

uint	decimal_precision () const override

bool	created_by_in2exists () const override
	Whether this Item was created by the IN->EXISTS subquery transformation. More...

void	set_created_by_in2exists ()

Public Member Functions inherited from Item_int_func
	Item_int_func ()

	Item_int_func (const POS &pos)

	Item_int_func (Item *a)

	Item_int_func (const POS &pos, Item *a)

	Item_int_func (Item a, Item b)

	Item_int_func (const POS &pos, Item a, Item b)

	Item_int_func (Item a, Item b, Item *c)

	Item_int_func (const POS &pos, Item a, Item b, Item *c)

	Item_int_func (Item a, Item b, Item c, Item d)

	Item_int_func (const POS &pos, Item a, Item b, Item c, Item d)

	Item_int_func (mem_root_deque< Item * > *list)

	Item_int_func (const POS &pos, PT_item_list *opt_list)

	Item_int_func (THD thd, Item_int_func item)

double	val_real () override

String *	val_str (String *str) override

bool	get_date (MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override

bool	get_time (MYSQL_TIME *ltime) override

enum Item_result	result_type () const override

Public Member Functions inherited from Item_func
virtual uint	argument_count () const

Item **	arguments () const

bool	reject_vector_args ()

uint	num_vector_args ()

bool	reject_geometry_args ()

bool	is_null_on_null () const

enum Type	type () const override

	Item_func ()

	Item_func (const POS &pos)

	Item_func (Item *a)

	Item_func (const POS &pos, Item *a)

	Item_func (Item a, Item b)

	Item_func (const POS &pos, Item a, Item b)

	Item_func (Item a, Item b, Item *c)

	Item_func (const POS &pos, Item a, Item b, Item *c)

	Item_func (Item a, Item b, Item c, Item d)

	Item_func (const POS &pos, Item a, Item b, Item c, Item d)

	Item_func (Item a, Item b, Item c, Item d, Item *e)

	Item_func (const POS &pos, Item a, Item b, Item c, Item d, Item *e)

	Item_func (Item a, Item b, Item c, Item d, Item e, Item f)

	Item_func (const POS &pos, Item a, Item b, Item c, Item d, Item e, Item f)

	Item_func (mem_root_deque< Item * > *list)

	Item_func (const POS &pos, PT_item_list *opt_list)

	Item_func (THD thd, const Item_func item)

virtual Item *	get_arg (uint i)
	Get the i'th argument of the function that this object represents. More...

virtual const Item *	get_arg (uint i) const
	Get the i'th argument of the function that this object represents. More...

virtual Item *	set_arg (THD , uint, Item )

bool	do_itemize (Parse_context pc, Item *res) override
	The core function that does the actual itemization. More...

bool	fix_fields (THD , Item *ref) override

bool	fix_func_arg (THD , Item *arg)

void	fix_after_pullout (Query_block parent_query_block, Query_block removed_query_block) override
	Fix after tables have been moved from one query_block level to the parent level, e.g by semijoin conversion. More...

virtual bool	resolve_type_inner (THD *)
	Resolve type of function after all arguments have had their data types resolved. More...

bool	propagate_type (THD *thd, const Type_properties &type) override
	Default implementation for all functions: Propagate base_item's type into all arguments. More...

virtual table_map	get_initial_pseudo_tables () const
	Returns the pseudo tables depended upon in order to evaluate this function expression. More...

table_map	used_tables () const override

table_map	not_null_tables () const override
	Return table map of tables that can't be NULL tables (tables that are used in a context where if they would contain a NULL row generated by a LEFT or RIGHT join, the item would not be true). More...

void	update_used_tables () override
	Updates used tables, not null tables information and accumulates properties up the item tree, cf. More...

void	set_used_tables (table_map map)

bool	eq (const Item *item) const override
	Compare this item with another item for equality. More...

virtual bool	have_rev_func () const

virtual Item *	key_item () const

bool	set_arguments (mem_root_deque< Item * > *list, bool context_free)
	Copy arguments from list to args array. More...

bool	split_sum_func (THD thd, Ref_item_array ref_item_array, mem_root_deque< Item > *fields) override
	See comments in Item_cmp_func::split_sum_func() More...

void	print (const THD thd, String str, enum_query_type query_type) const override
	This method is used for to: More...

void	print_op (const THD thd, String str, enum_query_type query_type) const

void	print_args (const THD thd, String str, uint from, enum_query_type query_type) const

virtual void	fix_num_length_and_dec ()

virtual bool	is_deprecated () const

bool	get_arg0_date (MYSQL_TIME *ltime, my_time_flags_t fuzzy_date)

bool	get_arg0_time (MYSQL_TIME *ltime)

bool	is_null () override
	The method allows to determine nullness of a complex expression without fully evaluating it, instead of calling val*() then checking null_value. More...

void	signal_divide_by_null ()

void	signal_invalid_argument_for_log ()

Field *	tmp_table_field (TABLE *t_arg) override

Item *	get_tmp_table_item (THD *thd) override
	If an Item is materialized in a temporary table, a different Item may have to be used in the part of the query that runs after the materialization. More...

my_decimal *	val_decimal (my_decimal *) override

bool	agg_arg_charsets (DTCollation &c, Item **items, uint nitems, uint flags, int item_sep)

bool	agg_arg_charsets_for_string_result (DTCollation &c, Item **items, uint nitems, int item_sep=1)

bool	agg_arg_charsets_for_comparison (DTCollation &c, Item **items, uint nitems, int item_sep=1)

Item *	replace_func_call (uchar *) override

bool	walk (Item_processor processor, enum_walk walk, uchar *arg) override
	Traverses a tree of Items in prefix and/or postfix order. More...

Item *	transform (Item_transformer transformer, uchar *arg) override
	Transform an Item_func object with a transformer callback function. More...

Item *	compile (Item_analyzer analyzer, uchar *arg_p, Item_transformer transformer, uchar arg_t) override
	Compile Item_func object with a processor and a transformer callback functions. More...

void	traverse_cond (Cond_traverser traverser, void *arg, traverse_order order) override

bool	replace_equal_field_checker (uchar **arg) override

Item *	replace_equal_field (uchar *arg) override

virtual bool	allow_replacement (Item_field const original, Item const subst)
	Check whether a function allows replacement of a field with another item: In particular, a replacement that changes the metadata of some Item from non-nullable to nullable is not allowed. More...

double	check_float_overflow (double value)
	Throw an error if the input double number is not finite, i.e. More...

longlong	check_integer_overflow (longlong value, bool val_unsigned)
	Throw an error if the input BIGINT value represented by the (longlong value, bool unsigned flag) pair cannot be returned by the function, i.e. More...

int	check_decimal_overflow (int error)
	Throw an error if the error code of a DECIMAL operation is E_DEC_OVERFLOW. More...

bool	has_timestamp_args ()

bool	has_date_args ()

bool	has_time_args ()

bool	has_datetime_args ()

bool	check_valid_arguments_processor (uchar *) override

Item *	gc_subst_transformer (uchar *arg) override
	Transformer function for GC substitution. More...

bool	resolve_type (THD *thd) override
	Resolve type-related information for this item, such as result field type, maximum size, precision, signedness, character set and collation. More...

virtual enum_const_item_cache	can_cache_json_arg (Item *arg)
	Whether an arg of a JSON function can be cached to avoid repetitive string->JSON conversion. More...

Public Member Functions inherited from Item_result_field
	Item_result_field ()=default

	Item_result_field (const POS &pos)

	Item_result_field (THD thd, const Item_result_field item)

Field *	get_tmp_table_field () override
	If this Item is being materialized into a temporary table, returns the field that is being materialized into. More...

void	set_result_field (Field *field) override

bool	is_result_field () const override

Field *	get_result_field () const override

void	cleanup () override
	Called for every Item after use (preparation and execution). More...

bool	mark_field_in_map (uchar *arg) override
	Mark underlying field in read or write map of a table. More...

longlong	llrint_with_overflow_check (double realval)

void	raise_numeric_overflow (const char *type_name)

double	raise_float_overflow ()

longlong	raise_integer_overflow ()

int	raise_decimal_overflow ()

Public Member Functions inherited from Item
	Item (const Item &)=delete

void	operator= (Item &)=delete

	Item ()
	Item constructor for general use. More...

	Item (THD thd, const Item item)
	Constructor used by Item_field, Item_ref & aggregate functions. More...

	Item (const POS &)
	Parse-time context-independent constructor. More...

	~Item () override=default

virtual bool	itemize (Parse_context pc, Item *res) final
	The same as contextualize() but with additional parameter. More...

void	rename (char *new_name)
	rename item (used for views, cleanup() return original name). More...

void	init_make_field (Send_field *tmp_field, enum enum_field_types type)

virtual void	notify_removal ()
	Called when an item has been removed, can be used to notify external objects about the removal, e.g subquery predicates that are part of the sj_candidates container. More...

virtual void	make_field (Send_field *field)

virtual Field *	make_string_field (TABLE *table) const
	Create a field to hold a string value from an item. More...

void	quick_fix_field ()

virtual void	set_can_use_prefix_key ()

bool	propagate_type (THD *thd, enum_field_types def=MYSQL_TYPE_VARCHAR, bool pin=false, bool inherit=false)
	Wrapper for easier calling of propagate_type(const Type_properties &). More...

virtual void	mark_json_as_scalar ()
	For Items with data type JSON, mark that a string argument is treated as a scalar JSON value. More...

virtual std::optional< ContainedSubquery >	get_contained_subquery (const Query_block *outer_query_block)
	If this item represents a IN/ALL/ANY/comparison_operator subquery, return that (along with data on how it will be executed). More...

type_conversion_status	save_in_field_no_warnings (Field *field, bool no_conversions)
	Save the item into a field but do not emit any warnings. More...

type_conversion_status	save_in_field (Field *field, bool no_conversions)
	Save a temporal value in packed longlong format into a Field. More...

void	save_in_field_no_error_check (Field *field, bool no_conversions)
	A slightly faster value of save_in_field() that returns no error value (you will need to check thd->is_error() yourself), and does not support saving into hidden fields for functional indexes. More...

virtual void	save_org_in_field (Field *field)

virtual bool	send (Protocol protocol, String str)
	This is only called from items that is not of type item_field. More...

bool	evaluate (THD thd, String str)
	Evaluate scalar item, possibly using the supplied buffer. More...

const Item *	unwrap_for_eq () const
	Unwrap an Item argument so that Item::eq() can see the "real" item, and not just the wrapper. More...

virtual Item_result	numeric_context_result_type () const
	Result type when an item appear in a numeric context. More...

Item_result	temporal_with_date_as_number_result_type () const
	Similar to result_type() but makes DATE, DATETIME, TIMESTAMP pretend to be numbers rather than strings. More...

virtual void	set_data_type_inherited ()
	Set data type for item as inherited. More...

virtual void	pin_data_type ()
	Pin the data type for the item. More...

enum_field_types	data_type () const
	Retrieve the derived data type of the Item. More...

virtual enum_field_types	actual_data_type () const
	Retrieve actual data type for an item. More...

virtual enum_field_types	default_data_type () const
	Get the default data (output) type for the specific item. More...

void	set_data_type (enum_field_types data_type)
	Set the data type of the current Item. More...

void	set_data_type_null ()

void	set_data_type_bool ()

void	set_data_type_int (enum_field_types type, bool unsigned_prop, uint32 max_width)
	Set the data type of the Item to be a specific integer type. More...

void	set_data_type_longlong ()
	Set the data type of the Item to be longlong. More...

void	set_data_type_decimal (uint8 precision, uint8 scale)
	Set the data type of the Item to be decimal. More...

void	set_data_type_double ()
	Set the data type of the Item to be double precision floating point. More...

void	set_data_type_float ()
	Set the data type of the Item to be single precision floating point. More...

void	set_data_type_string (uint32 max_l)
	Set the Item to be variable length string. More...

void	set_data_type_string (ulonglong max_char_length_arg)
	Set the Item to be variable length string. More...

void	set_data_type_string (uint32 max_l, const CHARSET_INFO *cs)
	Set the Item to be variable length string. More...

void	set_data_type_string (uint32 max_l, const DTCollation &coll)
	Set the Item to be variable length string. More...

void	set_data_type_char (uint32 max_l)
	Set the Item to be fixed length string. More...

void	set_data_type_char (uint32 max_l, const CHARSET_INFO *cs)
	Set the Item to be fixed length string. More...

void	set_data_type_blob (enum_field_types type, uint32 max_l)
	Set the Item to be of BLOB type. More...

void	set_data_type_date ()
	Set all type properties for Item of DATE type. More...

void	set_data_type_time (uint8 fsp)
	Set all type properties for Item of TIME type. More...

void	set_data_type_datetime (uint8 fsp)
	Set all properties for Item of DATETIME type. More...

void	set_data_type_timestamp (uint8 fsp)
	Set all properties for Item of TIMESTAMP type. More...

void	set_data_type_vector (uint32 max_l)
	Set the data type of the Item to be VECTOR. More...

void	set_data_type_geometry ()
	Set the data type of the Item to be GEOMETRY. More...

void	set_data_type_json ()
	Set the data type of the Item to be JSON. More...

void	set_data_type_year ()
	Set the data type of the Item to be YEAR. More...

void	set_data_type_bit (uint32 max_bits)
	Set the data type of the Item to be bit. More...

void	set_data_type_from_item (const Item *item)
	Set data type properties of the item from the properties of another item. More...

virtual TYPELIB *	get_typelib () const
	Get the typelib information for an item of type set or enum. More...

virtual Item_result	cast_to_int_type () const

bool	aggregate_type (const char name, Item *items, uint count)
	Aggregates data types from array of items into current item. More...

virtual enum_monotonicity_info	get_monotonicity_info () const

virtual longlong	val_int_endpoint (bool left_endp, bool *incl_endp)

virtual longlong	val_date_temporal ()
	Return date value of item in packed longlong format. More...

virtual longlong	val_time_temporal ()
	Return time value of item in packed longlong format. More...

longlong	val_temporal_by_field_type ()
	Return date or time value of item in packed longlong format, depending on item field type. More...

longlong	int_sort_key ()
	Produces a key suitable for filesort. More...

longlong	val_temporal_with_round (enum_field_types type, uint8 dec)
	Get date or time value in packed longlong format. More...

ulonglong	val_uint ()

virtual String *	val_str_ascii (String *str)

virtual bool	val_bool ()

virtual bool	val_json (Json_wrapper *result)
	Get a JSON value from an Item. More...

bool	error_json ()
	Get the value to return from val_json() in case of errors. More...

bool	get_date_from_non_temporal (MYSQL_TIME *ltime, my_time_flags_t fuzzydate)
	Convert a non-temporal type to date. More...

bool	get_time_from_non_temporal (MYSQL_TIME *ltime)
	Convert a non-temporal type to time. More...

my_decimal *	error_decimal (my_decimal *decimal_value)
	Get the value to return from val_decimal() in case of errors. More...

String *	error_str ()
	Get the value to return from val_str() in case of errors. More...

type_conversion_status	save_time_in_field (Field *field)

type_conversion_status	save_date_in_field (Field *field)

type_conversion_status	save_str_value_in_field (Field field, String result)

virtual const char *	full_name () const

virtual bool	basic_const_item () const
	Returns true if this is a simple constant item like an integer, not a constant expression. More...

bool	may_eval_const_item (const THD *thd) const

virtual Item *	clone_item () const

virtual cond_result	eq_cmp_result () const

uint	float_length (uint decimals_par) const

int	decimal_int_part () const

virtual uint	time_precision ()
	TIME precision of the item: 0..6. More...

virtual uint	datetime_precision ()
	DATETIME precision of the item: 0..6. More...

bool	const_item () const
	Returns true if item is constant, regardless of query evaluation state. More...

bool	const_for_execution () const
	Returns true if item is constant during one query execution. More...

bool	may_evaluate_const (const THD *thd) const
	Return true if this is a const item that may be evaluated in the current phase of statement processing. More...

bool	is_non_deterministic () const

bool	is_outer_reference () const

void	print_item_w_name (const THD thd, String , enum_query_type query_type) const

void	print_for_order (const THD thd, String str, enum_query_type query_type, const char *used_alias) const
	Prints the item when it's part of ORDER BY and GROUP BY. More...

bool	split_sum_func2 (THD thd, Ref_item_array ref_item_array, mem_root_deque< Item > fields, Item *ref, bool skip_registered)

virtual bool	get_timeval (my_timeval tm, int warnings)
	Get timestamp in "struct timeval" format. More...

bool	update_null_value ()
	Make sure the null_value member has a correct value. More...

virtual void	apply_is_true ()
	Apply the IS TRUE truth property, meaning that an UNKNOWN result and a FALSE result are treated the same. More...

virtual void	no_rows_in_result ()

virtual Item *	copy_or_same (THD *)

virtual Item *	copy_andor_structure (THD *)

virtual Item *	real_item ()

virtual const Item *	real_item () const

virtual const CHARSET_INFO *	charset_for_protocol ()

template<class T >
auto	walk_helper_thunk (uchar *arg)

template<class T >
auto	analyze_helper_thunk (uchar **arg)
	See CompileItem. More...

virtual bool	intro_version (uchar *)

bool	cleanup_processor (uchar *)
	cleanup() item if it is resolved ('fixed'). More...

virtual bool	collect_item_field_processor (uchar *)

virtual bool	collect_item_field_or_ref_processor (uchar *)

virtual bool	collect_outer_field_processor (uchar *)

virtual bool	collect_item_field_or_view_ref_processor (uchar *)
	Collects fields and view references that have the qualifying table in the specified query block. More...

virtual bool	add_field_to_set_processor (uchar *)
	Item::walk function. More...

virtual bool	visitor_processor (uchar *arg)
	A processor to handle the select lex visitor framework. More...

virtual bool	add_field_to_cond_set_processor (uchar *)
	Item::walk function. More...

virtual bool	remove_column_from_bitmap (uchar *arg)
	Visitor interface for removing all column expressions (Item_field) in this expression tree from a bitmap. More...

virtual bool	find_item_in_field_list_processor (uchar *)

virtual bool	change_context_processor (uchar *)

virtual bool	find_item_processor (uchar *arg)

virtual bool	find_field_processor (uchar *)
	Is this an Item_field which references the given Field argument? More...

virtual bool	reset_wf_state (uchar *arg)
	Reset execution state for such window function types as determined by arg. More...

virtual bool	used_tables_for_level (uchar *arg)
	Return used table information for the specified query block (level). More...

virtual bool	check_column_privileges (uchar *thd)
	Check privileges. More...

virtual bool	inform_item_in_cond_of_tab (uchar *)

virtual void	bind_fields ()
	Bind objects from the current execution context to field objects in item trees. More...

virtual bool	clean_up_after_removal (uchar *arg)
	Clean up after removing the item from the item tree. More...

virtual bool	aggregate_check_distinct (uchar *)

virtual bool	aggregate_check_group (uchar *)

virtual bool	is_strong_side_column_not_in_fd (uchar *)

virtual bool	is_column_not_in_fd (uchar *)

virtual Bool3	local_column (const Query_block *) const

virtual bool	collect_scalar_subqueries (uchar *)

virtual bool	collect_grouped_aggregates (uchar *)

virtual bool	collect_subqueries (uchar *)

virtual bool	update_depended_from (uchar *)

virtual bool	has_aggregate_ref_in_group_by (uchar *)
	Check if an aggregate is referenced from within the GROUP BY clause of the query block in which it is aggregated. More...

bool	visit_all_analyzer (uchar **)

virtual bool	cache_const_expr_analyzer (uchar **cache_item)
	Check if an item is a constant one and can be cached. More...

Item *	cache_const_expr_transformer (uchar *item)
	Cache item if needed. More...

virtual bool	check_partition_func_processor (uchar *)
	Check if a partition function is allowed. More...

virtual bool	subst_argument_checker (uchar **arg)

virtual bool	explain_subquery_checker (uchar **)

virtual Item *	explain_subquery_propagator (uchar *)

virtual Item *	equal_fields_propagator (uchar *)

virtual bool	disable_constant_propagation (uchar *)

virtual bool	check_gcol_depend_default_processor (uchar *args)
	Check if a generated expression depends on DEFAULT function with specific column name as argument. More...

virtual Item *	replace_with_derived_expr (uchar *arg)
	Assuming this expression is part of a condition that would be pushed to the WHERE clause of a materialized derived table, replace, in this expression, each derived table's column with a clone of the expression lying under it in the derived table's definition. More...

virtual Item *	replace_with_derived_expr_ref (uchar *arg)
	Assuming this expression is part of a condition that would be pushed to the HAVING clause of a materialized derived table, replace, in this expression, each derived table's column with a reference to the expression lying under it in the derived table's definition. More...

virtual Item *	replace_view_refs_with_clone (uchar *arg)
	Assuming this expression is part of a condition that would be pushed to a materialized derived table, replace, in this expression, each view reference with a clone of the expression in merged derived table's definition. More...

virtual Item *	this_item ()

virtual const Item *	this_item () const

virtual Item **	this_item_addr (THD , Item *addr_arg)

virtual uint	cols () const

virtual Item *	element_index (uint)

virtual Item **	addr (uint)

virtual bool	check_cols (uint c)

virtual bool	null_inside ()

virtual void	bring_value ()

Field *	tmp_table_field_from_field_type (TABLE *table, bool fixed_length) const
	Create a field based on field_type of argument. More...

virtual Item_field *	field_for_view_update ()

virtual Item *	truth_transformer (THD *thd, Bool_test test)
	Informs an item that it is wrapped in a truth test, in case it wants to transforms itself to implement this test by itself. More...

virtual Item *	update_value_transformer (uchar *)

virtual Item *	replace_scalar_subquery (uchar *)
	When walking the item tree seeing an Item_singlerow_subselect matching a target, replace it with a substitute field used when transforming scalar subqueries into derived tables. More...

virtual Item *	replace_item_field (uchar *)
	Transform processor used by Query_block::transform_grouped_to_derived to replace fields which used to be at the transformed query block with corresponding fields in the new derived table containing the grouping operation of the original transformed query block. More...

virtual Item *	replace_item_view_ref (uchar *)

virtual Item *	replace_aggregate (uchar *)

virtual Item *	replace_outer_ref (uchar *)

virtual bool	update_aggr_refs (uchar *)
	A walker processor overridden by Item_aggregate_ref, q.v. More...

Item *	convert_charset (THD thd, const CHARSET_INFO tocs, bool ignore_errors=false)
	Convert constant string in this object into the specified character set. More...

void	delete_self ()
	Delete this item. More...

virtual bool	is_splocal () const

virtual Settable_routine_parameter *	get_settable_routine_parameter ()

bool	is_temporal_with_date () const

bool	is_temporal_with_date_and_time () const

bool	is_temporal_with_time () const

bool	is_temporal () const

bool	has_compatible_context (Item *item) const
	Check whether this and the given item has compatible comparison context. More...

virtual Field::geometry_type	get_geometry_type () const

String *	check_well_formed_result (String *str, bool send_error, bool truncate)
	Verifies that the input string is well-formed according to its character set. More...

bool	eq_by_collation (Item item, const CHARSET_INFO cs)
	Compare two items using a given collation. More...

CostOfItem	cost () const

uint32	max_char_length () const

uint32	max_char_length (const CHARSET_INFO *cs) const

void	fix_char_length (uint32 max_char_length_arg)

virtual bool	is_outer_field () const

bool	is_blob_field () const
	Check if an item either is a blob field, or will be represented as a BLOB field if a field is created based on this item. More...

uint	reference_count () const

void	increment_ref_count ()
	Increment reference count. More...

uint	decrement_ref_count ()
	Decrement reference count. More...

bool	has_subquery () const

bool	has_stored_program () const

bool	has_aggregation () const

void	set_aggregation ()
	Set the "has aggregation" property. More...

void	reset_aggregation ()
	Reset the "has aggregation" property. More...

bool	has_wf () const

void	set_wf ()
	Set the "has window function" property. More...

bool	has_grouping_set_dep () const

void	set_group_by_modifier ()
	Set the property: this item (tree) contains a reference to a GROUP BY modifier (such as ROLLUP) More...

bool	has_grouping_func () const

void	set_grouping_func ()
	Set the property: this item is a call to GROUPING. More...

void	mark_subqueries_optimized_away ()

virtual bool	gc_subst_analyzer (uchar **)
	Analyzer function for GC substitution. More...

virtual bool	replace_field_processor (uchar *)
	A processor that replaces any Fields with a Create_field_wrapper. More...

bool	can_be_substituted_for_gc (bool array=false) const
	Check if this item is of a type that is eligible for GC substitution. More...

void	aggregate_float_properties (enum_field_types type, Item **items, uint nitems)
	Set max_length and decimals of function if function is floating point and result length/precision depends on argument ones. More...

void	aggregate_decimal_properties (Item **items, uint nitems)
	Set data type, precision and scale of item of type decimal from list of items. More...

void	aggregate_temporal_properties (enum_field_types type, Item **items, uint nitems)
	Set data type and fractional seconds precision for temporal functions. More...

bool	aggregate_string_properties (enum_field_types type, const char name, Item *items, uint nitems)
	Aggregate string properties (character set, collation and maximum length) for string function. More...

void	aggregate_bit_properties (Item **items, uint nitems)
	Set data type and properties of a BIT column. More...

virtual bool	repoint_const_outer_ref (uchar *arg)
	This function applies only to Item_field objects referred to by an Item_ref object that has been marked as a const_item. More...

virtual bool	strip_db_table_name_processor (uchar *)

virtual void	compute_cost (CostOfItem *root_cost) const
	Compute the cost of evaluating this Item. More...

bool	is_abandoned () const

bool	is_nullable () const

void	set_nullable (bool nullable)

virtual bool	supports_partial_update (const Field_json *field) const
	Check if this expression can be used for partial update of a given JSON column. More...

virtual bool	returns_array () const
	Whether the item returns array of its data type. More...

virtual void	allow_array_cast ()
	A helper function to ensure proper usage of CAST(. More...

Public Member Functions inherited from Parse_tree_node_tmpl< Context >
virtual	~Parse_tree_node_tmpl ()=default

bool	is_contextualized () const

virtual bool	contextualize (Context *pc) final

void	error (Context *pc, const POS &pos) const
	syntax_error() function replacement for deferred reporting of syntax errors More...

void	error (Context pc, const POS &pos, const char msg) const
	syntax_error() function replacement for deferred reporting of syntax errors More...

void	errorf (Context pc, const POS &pos, const char format,...) const
	syntax_error() function replacement for deferred reporting of syntax errors More...

Public Attributes
Item *	m_const_folding [2] {nullptr, nullptr}

Public Attributes inherited from Item_func
uint	arg_count
	How many arguments in 'args'. More...

Public Attributes inherited from Item
Item *	next_free
	Intrusive list pointer for free list. More...

DTCollation	collation
	Character set and collation properties assigned for this Item. More...

Item_name_string	item_name
	Name from query. More...

Item_name_string	orig_name
	Original item name (if it was renamed) More...

uint32	max_length
	Maximum length of result of evaluating this item, in number of bytes. More...

item_marker	marker
	This member has several successive meanings, depending on the phase we're in (. More...

Item_result	cmp_context
	Comparison context. More...

bool	fixed
	True if item has been resolved. More...

uint8	decimals
	Number of decimals in result when evaluating this item. More...

bool	null_value
	True if item is null. More...

bool	unsigned_flag

bool	m_is_window_function
	True if item represents window func. More...

bool	hidden {false}
	If the item is in a SELECT list (Query_block::fields) and hidden is true, the item wasn't actually in the list as given by the user (it was added by the optimizer, to e.g. More...

bool	m_in_check_constraint_exec_ctx {false}
	True if item is a top most element in the expression being evaluated for a check constraint. More...

Public Attributes inherited from Parse_tree_node_tmpl< Context >
POS	m_pos

Private Member Functions
bool	compare_const (THD thd, Item const_item)
	Checks if the current constant value m_const_arg (that each field in fields needs to be equal to during execution) is the same as the provided constant item. More...

void	check_covering_prefix_keys ()

Private Attributes
List< Item_field >	fields
	List of equal field items. More...

Item *	m_const_arg {nullptr}
	Optional constant item equal to all the field items. More...

cmp_item *	eval_item {nullptr}
	Helper for comparing the fields. More...

Arg_comparator	cmp
	Helper for comparing constants. More...

bool	m_always_false {false}
	Flag set to true if the equality is known to be always false. More...

bool	compare_as_dates {false}
	Should constants be compared as datetimes? More...

Additional Inherited Members
Public Types inherited from Item_func
enum	Functype { UNKNOWN_FUNC , EQ_FUNC , EQUAL_FUNC , NE_FUNC , LT_FUNC , LE_FUNC , GE_FUNC , GT_FUNC , FT_FUNC , MATCH_FUNC , LIKE_FUNC , ISNULL_FUNC , ISNOTNULL_FUNC , ISTRUTH_FUNC , COND_AND_FUNC , COND_OR_FUNC , XOR_FUNC , BETWEEN , IN_FUNC , MULTI_EQ_FUNC , INTERVAL_FUNC , ISNOTNULLTEST_FUNC , SP_EQUALS_FUNC , SP_DISJOINT_FUNC , SP_DISTANCE_FUNC , SP_INTERSECTS_FUNC , SP_TOUCHES_FUNC , SP_CROSSES_FUNC , SP_WITHIN_FUNC , SP_CONTAINS_FUNC , SP_COVEREDBY_FUNC , SP_COVERS_FUNC , SP_OVERLAPS_FUNC , SP_STARTPOINT , SP_ENDPOINT , SP_EXTERIORRING , SP_POINTN , SP_GEOMETRYN , SP_INTERIORRINGN , NOT_FUNC , NOT_ALL_FUNC , NOW_FUNC , FROM_DAYS_FUNC , TRIG_COND_FUNC , SUSERVAR_FUNC , GUSERVAR_FUNC , COLLATE_FUNC , EXTRACT_FUNC , TYPECAST_FUNC , FUNC_SP , UDF_FUNC , NEG_FUNC , GSYSVAR_FUNC , GROUPING_FUNC , ROLLUP_GROUP_ITEM_FUNC , TABLE_FUNC , DD_INTERNAL_FUNC , PLUS_FUNC , MINUS_FUNC , MUL_FUNC , DIV_FUNC , CEILING_FUNC , ROUND_FUNC , TRUNCATE_FUNC , SQRT_FUNC , ABS_FUNC , POW_FUNC , SIGN_FUNC , FLOOR_FUNC , LOG_FUNC , LN_FUNC , LOG10_FUNC , SIN_FUNC , TAN_FUNC , COS_FUNC , COT_FUNC , DEGREES_FUNC , RADIANS_FUNC , EXP_FUNC , ASIN_FUNC , ATAN_FUNC , ACOS_FUNC , MOD_FUNC , IF_FUNC , NULLIF_FUNC , CASE_FUNC , YEAR_FUNC , YEARWEEK_FUNC , MAKEDATE_FUNC , MAKETIME_FUNC , MONTH_FUNC , MONTHNAME_FUNC , DAY_FUNC , DAYNAME_FUNC , TO_DAYS_FUNC , TO_SECONDS_FUNC , DATE_FUNC , HOUR_FUNC , MINUTE_FUNC , SECOND_FUNC , MICROSECOND_FUNC , DAYOFYEAR_FUNC , ADDTIME_FUNC , QUARTER_FUNC , WEEK_FUNC , WEEKDAY_FUNC , DATEADD_FUNC , FROM_UNIXTIME_FUNC , CONVERT_TZ_FUNC , LAST_DAY_FUNC , UNIX_TIMESTAMP_FUNC , TIME_TO_SEC_FUNC , TIMESTAMPDIFF_FUNC , DATETIME_LITERAL , GREATEST_FUNC , COALESCE_FUNC , LEAST_FUNC , JSON_CONTAINS , JSON_OVERLAPS , JSON_UNQUOTE_FUNC , MEMBER_OF_FUNC , STRCMP_FUNC , TRUE_FUNC , FALSE_FUNC , SYSDATE_FUNC , TIMEDIFF_FUNC , PERIODADD_FUNC , PERIODDIFF_FUNC , SEC_TO_TIME_FUNC , GET_FORMAT_FUNC , ANY_VALUE_FUNC , JSON_LENGTH_FUNC , JSON_DEPTH_FUNC , JSON_EXTRACT_FUNC , JSON_OBJECT_FUNC , JSON_ARRAY_FUNC , JSON_VALID_FUNC , JSON_TYPE_FUNC , JSON_PRETTY_FUNC , JSON_QUOTE_FUNC , JSON_CONTAINS_PATH_FUNC , JSON_STORAGE_SIZE_FUNC , JSON_STORAGE_FREE_FUNC , JSON_VALUE_FUNC , JSON_SEARCH_FUNC , JSON_SCHEMA_VALIDATION_REPORT_FUNC , JSON_SCHEMA_VALID_FUNC }

enum	optimize_type { OPTIMIZE_NONE , OPTIMIZE_KEY , OPTIMIZE_OP , OPTIMIZE_NULL , OPTIMIZE_EQUAL }

Public Types inherited from Item
enum	Type { INVALID_ITEM , FIELD_ITEM , FUNC_ITEM , SUM_FUNC_ITEM , AGGR_FIELD_ITEM , STRING_ITEM , INT_ITEM , DECIMAL_ITEM , REAL_ITEM , NULL_ITEM , HEX_BIN_ITEM , DEFAULT_VALUE_ITEM , COND_ITEM , REF_ITEM , INSERT_VALUE_ITEM , SUBQUERY_ITEM , ROW_ITEM , CACHE_ITEM , TYPE_HOLDER_ITEM , PARAM_ITEM , ROUTINE_FIELD_ITEM , TRIGGER_FIELD_ITEM , XPATH_NODESET_ITEM , VALUES_COLUMN_ITEM , NAME_CONST_ITEM }

enum	cond_result { COND_UNDEF , COND_OK , COND_TRUE , COND_FALSE }

enum	traverse_order { POSTFIX , PREFIX }

enum	enum_const_item_cache { CACHE_NONE = 0 , CACHE_JSON_VALUE , CACHE_JSON_ATOM }
	How to cache constant JSON data. More...

enum	Bool_test { BOOL_IS_TRUE = 0x00 , BOOL_IS_FALSE = 0x01 , BOOL_IS_UNKNOWN = 0x02 , BOOL_NOT_TRUE = 0x03 , BOOL_NOT_FALSE = 0x04 , BOOL_NOT_UNKNOWN = 0x05 , BOOL_IDENTITY = 0x06 , BOOL_NEGATED = 0x07 , BOOL_ALWAYS_TRUE = 0x08 , BOOL_ALWAYS_FALSE = 0x09 }
	< Modifier for result transformation More...

enum	item_marker { MARKER_NONE = 0 , MARKER_IMPLICIT_NE_ZERO = 1 , MARKER_CONST_PROPAG = 2 , MARKER_BIT = 4 , MARKER_FUNC_DEP_NOT_NULL = 5 , MARKER_DISTINCT_GROUP = 6 , MARKER_COND_DERIVED_TABLE = 7 , MARKER_TRAVERSAL = 8 , MARKER_ICP_COND_USES_INDEX_ONLY = 10 }
	< Values for member 'marker' More...

Public Types inherited from Parse_tree_node_tmpl< Context >
typedef Context	context_t

Static Public Member Functions inherited from Item
static void *	operator new (size_t size) noexcept

static void *	operator new (size_t size, MEM_ROOT *mem_root, const std::nothrow_t &arg=std::nothrow) noexcept

static void	operator delete (void *ptr, size_t size)

static void	operator delete (void , MEM_ROOT , const std::nothrow_t &) noexcept

static enum_field_types	result_to_type (Item_result result)

static Item_result	type_to_result (enum_field_types type)

static enum_field_types	type_for_variable (enum_field_types src_type)
	Provide data type for a user or system variable, based on the type of the item that is assigned to the variable. More...

static enum_field_types	string_field_type (uint32 max_bytes)
	Determine correct string field type, based on string length. More...

static const CHARSET_INFO *	default_charset ()

Static Public Member Functions inherited from Parse_tree_node_tmpl< Context >
static void *	operator new (size_t size, MEM_ROOT *mem_root, const std::nothrow_t &arg=std::nothrow) noexcept

static void	operator delete (void *ptr, size_t size)

static void	operator delete (void , MEM_ROOT , const std::nothrow_t &) noexcept

Static Public Attributes inherited from Item_bool_func
static const char *	bool_transform_names [10]

static const Bool_test	bool_transform [10][8]
	Array that transforms a boolean test according to another. More...

Protected Member Functions inherited from Item_bool_func
	Item_bool_func ()

	Item_bool_func (const POS &pos)

	Item_bool_func (Item *a)

	Item_bool_func (const POS &pos, Item *a)

	Item_bool_func (Item a, Item b, Item *c)

	Item_bool_func (Item a, Item b)

	Item_bool_func (const POS &pos, Item a, Item b)

	Item_bool_func (const POS &pos, Item a, Item b, Item *c)

	Item_bool_func (THD thd, Item_bool_func item)

Protected Member Functions inherited from Item_func
bool	param_type_uses_non_param (THD *thd, enum_field_types def=MYSQL_TYPE_VARCHAR)

bool	param_type_is_default (THD *thd, uint start, uint end, uint step, enum_field_types def)
	For arguments of this Item_func ("args" array), in range [start, start+step, start+2*step,...,end[ : if they're a PS parameter with invalid (not known) type, give them default type "def". More...

bool	param_type_is_default (THD *thd, uint start, uint end, enum_field_types def=MYSQL_TYPE_VARCHAR)

bool	param_type_is_rejected (uint start, uint end)
	For arguments of this Item_func ("args" array), in range [start,end[ : sends error if they're a dynamic parameter. More...

const Item_field *	contributes_to_filter (THD thd, table_map read_tables, table_map filter_for_table, const MY_BITMAP fields_to_ignore) const
	Whether or not an item should contribute to the filtering effect (. More...

virtual bool	may_have_named_parameters () const
	Named parameters are allowed in a parameter list. More...

bool	is_non_const_over_literals (uchar *) override

bool	check_function_as_value_generator (uchar *checker_args) override
	Check if this item is allowed for a virtual column or inside a default expression. More...

bool	is_valid_for_pushdown (uchar *arg) override
	Check if all the columns present in this expression are from the derived table. More...

bool	check_column_in_window_functions (uchar *arg) override
	Check if all the columns present in this expression are present in PARTITION clause of window functions of the derived table. More...

bool	check_column_in_group_by (uchar *arg) override
	Check if all the columns present in this expression are present in GROUP BY clause of the derived table. More...

longlong	val_int_from_real ()

Protected Member Functions inherited from Item
String *	make_empty_result ()
	Sets the result value of the function an empty string, using the current character set. More...

bool	skip_itemize (Item **res)
	Helper function to skip itemize() for grammar-allocated items. More...

virtual type_conversion_status	save_in_field_inner (Field *field, bool no_conversions)
	Helper function which does all of the work for save_in_field(Field*, bool), except some error checking common to all subclasses, which is performed by save_in_field() itself. More...

String *	val_string_from_real (String *str)

String *	val_string_from_int (String *str)

String *	val_string_from_decimal (String *str)

String *	val_string_from_date (String *str)

String *	val_string_from_datetime (String *str)

String *	val_string_from_time (String *str)

my_decimal *	val_decimal_from_real (my_decimal *decimal_value)

my_decimal *	val_decimal_from_int (my_decimal *decimal_value)

my_decimal *	val_decimal_from_string (my_decimal *decimal_value)

my_decimal *	val_decimal_from_date (my_decimal *decimal_value)

my_decimal *	val_decimal_from_time (my_decimal *decimal_value)

longlong	val_int_from_decimal ()

longlong	val_int_from_date ()

longlong	val_int_from_time ()

longlong	val_int_from_datetime ()

longlong	val_int_from_string ()

double	val_real_from_decimal ()

double	val_real_from_string ()

bool	error_bool ()
	Get the value to return from val_bool() in case of errors. More...

int	error_int ()
	Get the value to return from val_int() in case of errors. More...

double	error_real ()
	Get the value to return from val_real() in case of errors. More...

bool	error_date ()
	Get the value to return from get_date() in case of errors. More...

bool	error_time ()
	Get the value to return from get_time() in case of errors. More...

String *	null_return_str ()
	Gets the value to return from val_str() when returning a NULL value. More...

bool	get_date_from_string (MYSQL_TIME *ltime, my_time_flags_t flags)
	Convert val_str() to date in MYSQL_TIME. More...

bool	get_date_from_real (MYSQL_TIME *ltime, my_time_flags_t flags)
	Convert val_real() to date in MYSQL_TIME. More...

bool	get_date_from_decimal (MYSQL_TIME *ltime, my_time_flags_t flags)
	Convert val_decimal() to date in MYSQL_TIME. More...

bool	get_date_from_int (MYSQL_TIME *ltime, my_time_flags_t flags)
	Convert val_int() to date in MYSQL_TIME. More...

bool	get_date_from_time (MYSQL_TIME *ltime)
	Convert get_time() from time to date in MYSQL_TIME. More...

bool	get_date_from_numeric (MYSQL_TIME *ltime, my_time_flags_t fuzzydate)
	Convert a numeric type to date. More...

bool	get_time_from_string (MYSQL_TIME *ltime)
	Convert val_str() to time in MYSQL_TIME. More...

bool	get_time_from_real (MYSQL_TIME *ltime)
	Convert val_real() to time in MYSQL_TIME. More...

bool	get_time_from_decimal (MYSQL_TIME *ltime)
	Convert val_decimal() to time in MYSQL_TIME. More...

bool	get_time_from_int (MYSQL_TIME *ltime)
	Convert val_int() to time in MYSQL_TIME. More...

bool	get_time_from_date (MYSQL_TIME *ltime)
	Convert date to time. More...

bool	get_time_from_datetime (MYSQL_TIME *ltime)
	Convert datetime to time. More...

bool	get_time_from_numeric (MYSQL_TIME *ltime)
	Convert a numeric type to time. More...

virtual longlong	val_date_temporal_at_utc ()

virtual longlong	val_time_temporal_at_utc ()

void	set_accum_properties (const Item *item)
	Set accumulated properties for an Item. More...

void	add_accum_properties (const Item *item)
	Add more accumulated properties to an Item. More...

void	set_subquery ()
	Set the "has subquery" property. More...

void	set_stored_program ()
	Set the "has stored program" property. More...

Protected Member Functions inherited from Parse_tree_node_tmpl< Context >
	Parse_tree_node_tmpl ()=delete

	Parse_tree_node_tmpl (const POS &pos)

	Parse_tree_node_tmpl (const POS &start_pos, const POS &end_pos)

bool	begin_parse_tree (Show_parse_tree *tree)

bool	end_parse_tree (Show_parse_tree *tree)

virtual bool	do_contextualize (Context *pc)
	Do all context-sensitive things and mark the node as contextualized. More...

virtual void	add_json_info (Json_object *json_obj)
	Add all the node-specific json fields. More...

Static Protected Member Functions inherited from Item
static bool	bit_func_returns_binary (const Item a, const Item b)

static bool	mark_field_in_map (Mark_field mark_field, Field field)
	Helper function for mark_field_in_map(uchar *arg). More...

Protected Attributes inherited from Item_func
Item **	args
	Array of pointers to arguments. More...

bool	null_on_null {true}
	Affects how to determine that NULL argument implies a NULL function return. More...

uint	allowed_arg_cols {1}

table_map	used_tables_cache {0}
	Value used in calculation of result of used_tables() More...

table_map	not_null_tables_cache {0}
	Value used in calculation of result of not_null_tables() More...

Protected Attributes inherited from Item_result_field
Field *	result_field {nullptr}

Protected Attributes inherited from Item
String	str_value
	str_values's main purpose is to cache the value in save_in_field More...

uint8	m_accum_properties

Static Protected Attributes inherited from Item
static constexpr uint8	PROP_SUBQUERY = 0x01
	Set of properties that are calculated by accumulation from underlying items. More...

static constexpr uint8	PROP_STORED_PROGRAM = 0x02

static constexpr uint8	PROP_AGGREGATION = 0x04

static constexpr uint8	PROP_WINDOW_FUNCTION = 0x08

static constexpr uint8	PROP_HAS_GROUPING_SET_DEP = 0x10
	Set if the item or one or more of the underlying items contains a GROUP BY modifier (such as ROLLUP). More...

static constexpr uint8	PROP_GROUPING_FUNC = 0x20
	Set if the item or one or more of the underlying items is a GROUPING function. More...

Detailed Description

The class Item_multi_eq is used to represent conjunctions of equality predicates of the form field1 = field2, and field = const in where conditions and on join conditions.

All equality predicates of the form field1=field2 contained in a conjunction are substituted for a sequence of items of this class. An item of this class Item_multi_eq(f1,f2,...fk) represents a multiple equality f1=f2=...=fk.

If a conjunction contains predicates f1=f2 and f2=f3, a new item of this class is created Item_multi_eq(f1,f2,f3) representing the multiple equality f1=f2=f3 that substitutes the above equality predicates in the conjunction. A conjunction of the predicates f2=f1 and f3=f1 and f3=f2 will be substituted for the item representing the same multiple equality f1=f2=f3. An item Item_multi_eq(f1,f2) can appear instead of a conjunction of f2=f1 and f1=f2, or instead of just the predicate f1=f2.

An item of the class Item_multi_eq inherits equalities from outer conjunctive levels.

Suppose we have a where condition of the following form: WHERE f1=f2 AND f3=f4 AND f3=f5 AND ... AND (...OR (f1=f3 AND ...)). In this case: f1=f2 will be substituted for Item_multi_eq(f1,f2); f3=f4 and f3=f5 will be substituted for Item_multi_eq(f3,f4,f5); f1=f3 will be substituted for Item_multi_eq(f1,f2,f3,f4,f5);

An object of the class Item_multi_eq can contain an optional constant item c. Then it represents a multiple equality of the form c=f1=...=fk.

Objects of the class Item_multi_eq are used for the following:

An object Item_multi_eq(t1.f1,...,tk.fk) allows us to consider any pair of tables ti and tj as joined by an equi-condition. Thus it provide us with additional access paths from table to table.
An object Item_multi_eq(t1.f1,...,tk.fk) is applied to deduce new SARGable predicates: f1=...=fk AND P(fi) => f1=...=fk AND P(fi) AND P(fj). It also can give us additional index scans and can allow us to improve selectivity estimates.
An object Item_multi_eq(t1.f1,...,tk.fk) is used to optimize the selected execution plan for the query: if table ti is accessed before the table tj then in any predicate P in the where condition the occurrence of tj.fj is substituted for ti.fi. This can allow an evaluation of the predicate at an earlier step.

When feature 1 is supported they say that join transitive closure is employed. When feature 2 is supported they say that search argument transitive closure is employed. Both features are usually supported by preprocessing original query and adding additional predicates. We do not just add predicates, we rather dynamically replace some predicates that can not be used to access tables in the investigated plan for those, obtained by substitution of some fields for equal fields, that can be used.

Multiple equality objects are employed only at the optimize phase. Usually they are not supposed to be evaluated. Yet in some cases we call the method val_int() for them. We have to take care of restricting the predicate such an object represents f1=f2= ...=fn to the projection of known fields fi1=...=fik.

Constructor & Destructor Documentation

◆ ~Item_multi_eq()

Item_multi_eq::~Item_multi_eq ( )

override

◆ Item_multi_eq() [1/5]

Item_multi_eq::Item_multi_eq	(	Item_field *	lhs_field,
		Item_field *	rhs_field
	)

◆ Item_multi_eq() [2/5]

Item_multi_eq::Item_multi_eq	(	Item *	const_item,
		Item_field *	field
	)

◆ Item_multi_eq() [3/5]

Item_multi_eq::Item_multi_eq ( Item_multi_eq * item_multi_eq )

explicit

◆ Item_multi_eq() [4/5]

Item_multi_eq::Item_multi_eq ( const Item_multi_eq & )

delete

◆ Item_multi_eq() [5/5]

Item_multi_eq::Item_multi_eq ( const Item_multi_eq && )

delete

Member Function Documentation

◆ add() [1/3]

void Item_multi_eq::add ( Item_field * field )

◆ add() [2/3]

bool Item_multi_eq::add	(	THD *	thd,
		Item *	const_item
	)

◆ add() [3/3]

bool Item_multi_eq::add	(	THD *	thd,
		Item *	const_item,
		Item_field *	field
	)

◆ cast_incompatible_args()

bool Item_multi_eq::cast_incompatible_args ( uchar * )

inlineoverridevirtual

Wrap incompatible arguments in CAST nodes to the expected data types.

Reimplemented from Item.

◆ check_covering_prefix_keys()

void Item_multi_eq::check_covering_prefix_keys ( )

private

◆ compare_collation()

const CHARSET_INFO * Item_multi_eq::compare_collation ( ) const

inlineoverridevirtual

Reimplemented from Item.

◆ compare_const()

bool Item_multi_eq::compare_const	(	THD *	thd,
		Item *	const_item
	)

private

Checks if the current constant value m_const_arg (that each field in fields needs to be equal to during execution) is the same as the provided constant item.

If that's not the case, it sets m_always_false to true as a field cannot be equal to different constant values at the same time.

Returns: false on success, true on error.

◆ const_arg()

Item * Item_multi_eq::const_arg ( ) const

inline

Returns the constant Item that this multi equality is equal to(if any).

◆ contains()

bool Item_multi_eq::contains ( const Item_field * field ) const

Check whether a field is referred in the multiple equality.

The function checks whether field is occurred in the Item_multi_eq object .

Parameters

field Item field whose occurrence is to be checked

Returns: true if multiple equality contains a reference to field, false otherwise.

◆ contains_only_equi_join_condition()

bool Item_multi_eq::contains_only_equi_join_condition ( ) const

inlineoverridevirtual

Whether this Item is an equi-join condition.

If this Item is a compound item (i.e. multiple condition AND'ed together), it will only return true if the Item contains only equi-join conditions AND'ed together. This is used to determine whether the condition can be used as a join condition for hash join (join conditions in hash join must be equi-join conditions), or if it should be placed as a filter after the join.

Reimplemented from Item_func.

◆ eq_specific()

bool Item_multi_eq::eq_specific ( const Item * ) const

overridevirtual

Provide a more specific equality check for a function.

Combine with Item::eq() to implement a complete equality check.

Reimplemented from Item_func.

◆ equality_substitution_analyzer()

bool Item_multi_eq::equality_substitution_analyzer ( uchar ** )

inlineoverridevirtual

Reimplemented from Item.

◆ equality_substitution_transformer()

Item * Item_multi_eq::equality_substitution_transformer ( uchar * arg )

overridevirtual

Transform an Item_multi_eq object after having added a table that represents a materialized semi-join.

If the multiple equality represented by the Item_multi_eq object contains a field from the subquery that was used to create the materialized table, add the corresponding key field from the materialized table to the multiple equality.

See also: JOIN::update_equalities_for_sjm() for the reason.

Reimplemented from Item.

◆ fix_fields()

bool Item_multi_eq::fix_fields	(	THD *	thd,
		Item **	ref
	)

overridevirtual

Reimplemented from Item.

◆ func_name()

const char * Item_multi_eq::func_name ( ) const

inlineoverridevirtual

Implements Item_func.

◆ functype()

enum Functype Item_multi_eq::functype ( ) const

inlineoverridevirtual

Reimplemented from Item_func.

◆ get_fields() [1/2]

FieldProxy Item_multi_eq::get_fields ( )

inline

◆ get_fields() [2/2]

ConstFieldProxy Item_multi_eq::get_fields ( ) const

inline

◆ get_filtering_effect()

float Item_multi_eq::get_filtering_effect	(	THD *	thd,
		table_map	filter_for_table,
		table_map	read_tables,
		const MY_BITMAP *	fields_to_ignore,
		double	rows_in_table
	)

overridevirtual

temporary area used for constant folding

Get filtering effect for multiple equalities, i.e.

"tx.col = value_1 = ... = value_n" where value_i may be a constant, a column etc.

The multiple equality only contributes to the filtering effect for 'filter_for_table' if a) A column in 'filter_for_table' is referred to b) at least one value_i is a constant or a column in a table already read

If this multiple equality refers to more than one column in 'filter_for_table', the predicates on all these fields will contribute to the filtering effect.

Reimplemented from Item.

◆ get_first()

Item_field * Item_multi_eq::get_first ( )

inline

Get the first field of multiple equality, use for semantic checking.

Return values

First field in the multiple equality.

◆ get_subst_item()

Item_field * Item_multi_eq::get_subst_item ( const Item_field * field )

Get item that can be substituted for the supplied item.

Parameters

field field item to get substitution field for, which must be present within the multiple equality itself.

Return values

Found substitution item in the multiple equality.

Get the first item of multiple equality that can be substituted for the given field item. In order to make semijoin materialization strategy work correctly we can't propagate equal fields between a materialized semijoin and the outer query (or any other semijoin) unconditionally. Thus the field is returned according to the following rules:

1) If the given field belongs to a materialized semijoin then the first field in the multiple equality which belongs to the same semijoin is returned. 2) If the given field doesn't belong to a materialized semijoin then the first field in the multiple equality is returned.

◆ members()

uint Item_multi_eq::members ( )

◆ merge()

bool Item_multi_eq::merge	(	THD *	thd,
		Item_multi_eq *	item
	)

Add members of another Item_multi_eq object.

The function merges two multiple equalities. After this operation the Item_multi_eq object additionally contains the field items of another item of the type Item_multi_eq. If the optional constant items are not equal the m_always_false flag is set to true.

Parameters

thd	thread handler
item	multiple equality whose members are to be joined

Returns: false if success, true if error

◆ operator=() [1/2]

Item_multi_eq Item_multi_eq::operator= ( const Item_multi_eq && )

delete

◆ operator=() [2/2]

Item_multi_eq Item_multi_eq::operator= ( const Item_multi_eq & )

delete

◆ print()

void Item_multi_eq::print	(	const THD *	,
		String *	str,
		enum_query_type
	)		const

overridevirtual

This method is used for to:

to generate a view definition query (SELECT-statement);
to generate a SQL-query for EXPLAIN EXTENDED;
to generate a SQL-query to be shown in INFORMATION_SCHEMA;
to generate a SQL-query that looks like a prepared statement for query_rewrite
debug.

For more information about view definition query, INFORMATION_SCHEMA query and why they should be generated from the Item-tree,

See also: mysql_register_view().

Reimplemented from Item.

◆ resolve_type()

bool Item_multi_eq::resolve_type ( THD * thd )

overridevirtual

Resolve type-related information for this item, such as result field type, maximum size, precision, signedness, character set and collation.

Also check compatibility of argument types and return error when applicable. Also adjust nullability when applicable.

Parameters

thd	thread handler

Returns: false if success, true if error

Reimplemented from Item_bool_func.

◆ select_optimize()

optimize_type Item_multi_eq::select_optimize ( const THD * )

inlineoverridevirtual

Reimplemented from Item_func.

◆ set_const_arg()

void Item_multi_eq::set_const_arg ( Item * const_item )

inline

◆ sort()

template<typename Node_cmp_func >

void Item_multi_eq::sort ( Node_cmp_func compare )

inline

Order field items in multiple equality according to a sorting criteria.

The function perform ordering of the field items in the Item_multi_eq object according to the criteria determined by the cmp callback parameter. If cmp(item_field1,item_field2,arg)<0 than item_field1 must be placed after item_field2.

The function sorts field items by the exchange sort algorithm. The list of field items is looked through and whenever two neighboring members follow in a wrong order they are swapped. This is performed again and again until we get all members in a right order.

Parameters

compare function to compare field item

◆ update_const()

bool Item_multi_eq::update_const ( THD * thd )

Check appearance of new constant items in the multiple equality object.

The function checks appearance of new constant items among the members of multiple equalities. Each new constant item is compared with the designated constant item if there is any in the multiple equality. If there is none the first new constant item becomes designated.

Parameters

thd	thread handler

Returns: false if success, true if error

◆ update_used_tables()

void Item_multi_eq::update_used_tables ( )

overridevirtual

Updates used tables, not null tables information and accumulates properties up the item tree, cf.

used_tables_cache, not_null_tables_cache and m_accum_properties.

TODO(sgunders): Consider just removing these caches; it causes a lot of bugs (cache invalidation is known to be a complex problem), and the performance benefits are dubious.

Reimplemented from Item.

◆ val_int()

longlong Item_multi_eq::val_int ( void )

overridevirtual

Implements Item.

◆ walk()

bool Item_multi_eq::walk	(	Item_processor	processor,
		enum_walk	walk,
		uchar *	arg
	)

overridevirtual

Traverses a tree of Items in prefix and/or postfix order.

Optionally walks into subqueries.

Parameters

processor	processor function to be invoked per item returns true to abort traversal, false to continue
walk	controls how to traverse the item tree enum_walk::PREFIX: call processor before invoking children enum_walk::POSTFIX: call processor after invoking children enum_walk::SUBQUERY go down into subqueries walk values are bit-coded and may be combined. Omitting both enum_walk::PREFIX and enum_walk::POSTFIX is undefined behaviour.
arg	Optional pointer to a walk-specific object

Return values

false	walk succeeded
true	walk aborted by agreement, an error may have been reported

Reimplemented from Item.

Member Data Documentation

◆ cmp

Arg_comparator Item_multi_eq::cmp

private

Helper for comparing constants.

◆ compare_as_dates

bool Item_multi_eq::compare_as_dates {false}

private

Should constants be compared as datetimes?

◆ eval_item

cmp_item* Item_multi_eq::eval_item {nullptr}

private

Helper for comparing the fields.

◆ fields

List<Item_field> Item_multi_eq::fields

private

List of equal field items.

◆ m_always_false

bool Item_multi_eq::m_always_false {false}

private

Flag set to true if the equality is known to be always false.

◆ m_const_arg

Item* Item_multi_eq::m_const_arg {nullptr}

private

Optional constant item equal to all the field items.

◆ m_const_folding

Item* Item_multi_eq::m_const_folding[2] {nullptr, nullptr}

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

sql/item_cmpfunc.h
sql/item_cmpfunc.cc

Classes

Public Member Functions

Public Attributes

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ ~Item_multi_eq()

◆ Item_multi_eq() [1/5]

◆ Item_multi_eq() [2/5]

◆ Item_multi_eq() [3/5]

◆ Item_multi_eq() [4/5]

◆ Item_multi_eq() [5/5]

Member Function Documentation

◆ add() [1/3]

◆ add() [2/3]

◆ add() [3/3]

◆ cast_incompatible_args()

◆ check_covering_prefix_keys()

◆ compare_collation()

◆ compare_const()

◆ const_arg()

◆ contains()

◆ contains_only_equi_join_condition()

◆ eq_specific()

◆ equality_substitution_analyzer()

◆ equality_substitution_transformer()

◆ fix_fields()

◆ func_name()

◆ functype()

◆ get_fields() [1/2]

◆ get_fields() [2/2]

◆ get_filtering_effect()

◆ get_first()

◆ get_subst_item()

◆ members()

◆ merge()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ print()

◆ resolve_type()

◆ select_optimize()

◆ set_const_arg()

◆ sort()

◆ update_const()

◆ update_used_tables()

◆ val_int()

◆ walk()

Member Data Documentation

◆ cmp

◆ compare_as_dates

◆ eval_item

◆ fields

◆ m_always_false

◆ m_const_arg

◆ m_const_folding