#include <item.h>

Inheritance diagram for Item_field:

Public Member Functions
void	set_item_equal (Item_equal *item_equal_arg)

void	set_item_equal_all_join_nests (Item_equal *item_equal)

	Item_field (Name_resolution_context context_arg, const char db_arg, const char table_name_arg, const char field_name_arg)
	Constructor used for internal information queries. More...

	Item_field (const POS &pos, const char db_arg, const char table_name_arg, const char *field_name_arg)
	Used from parser to construct column references. More...

	Item_field (THD thd, Item_field item)
	Used to create a copy (clone) of another Item_field. More...

	Item_field (THD thd, Name_resolution_context context_arg, Table_ref tr, Field field)
	Constructor used inside setup_wild(). More...

	Item_field (Field *field)
	Create column reference based on a table field. More...

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

enum Type	type () const override

bool	eq (const Item *item, bool binary_cmp) const override

double	val_real () override

longlong	val_int () override

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

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

longlong	val_time_temporal_at_utc () override

longlong	val_date_temporal_at_utc () override

my_decimal *	val_decimal (my_decimal *) override

String *	val_str (String *) override

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

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

void	reset_field (Field *f)
	Reset this item to point to a field from the new temporary table. More...

bool	fix_fields (THD , Item *) override
	Resolve the name of a column reference. More...

void	make_field (Send_field *tmp_field) override

void	save_org_in_field (Field *field) override
	Set a field's value from a item. More...

table_map	used_tables () const override

Item_result	result_type () const override

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

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

Item_result	cast_to_int_type () const override

enum_monotonicity_info	get_monotonicity_info () const override

longlong	val_int_endpoint (bool left_endp, bool *incl_endp) override

void	set_result_field (Field *field_arg) override

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...

Field *	tmp_table_field (TABLE *) override

void	set_base_item_field (const Item_field *item)

const Item_field *	base_item_field () const

bool	get_date (MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override

bool	get_time (MYSQL_TIME *ltime) override

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

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...

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...

bool	collect_item_field_processor (uchar *arg) override
	Store the pointer to this item field into a list if not already there. More...

bool	collect_item_field_or_ref_processor (uchar *arg) override
	When collecting information about columns when transforming correlated scalar subqueries using derived tables, we need to decide which duplicates, if any, to retain: More...

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

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

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

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

bool	find_item_in_field_list_processor (uchar *arg) override
	Check if an Item_field references some field from a list of fields. More...

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

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

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

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

bool	check_column_privileges (uchar *arg) override
	Check privileges of base table column. More...

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

void	bind_fields () override
	Bind objects from the current execution context to field objects in item trees. 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 this column is found in PARTITION clause of all the window functions. More...

bool	check_column_in_group_by (uchar *arg) override
	Check if this column is found in GROUP BY. More...

Item *	replace_with_derived_expr (uchar *arg) override
	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...

Item *	replace_with_derived_expr_ref (uchar *arg) override
	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...

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

void	reset_field ()
	Reset all aspect of a field object, so that it can be re-resolved. More...

Item_equal *	find_item_equal (COND_EQUAL *cond_equal) const
	Find a field among specified multiple equalities. More...

bool	subst_argument_checker (uchar **arg) override
	Check whether a field can be substituted by an equal item. More...

Item *	equal_fields_propagator (uchar *arg) override
	If field matches a multiple equality, set a pointer to that object in the field. More...

Item *	replace_item_field (uchar *) override
	If this field is the target is the target of replacement, replace it with the info object's item or, if the item is found inside a subquery, the target is an outer reference, so we create a new Item_field, mark it accordingly and replace with that instead. More...

bool	disable_constant_propagation (uchar *) override

Item *	replace_equal_field (uchar *) override
	Replace an Item_field for an equal Item_field that evaluated earlier (if any). More...

uint32	max_disp_length ()

Item_field *	field_for_view_update () override

Item *	safe_charset_converter (THD thd, const CHARSET_INFO tocs) override

int	fix_outer_field (THD thd, Field field, Item *reference)
	Resolve the name of an outer select column reference. More...

Item *	update_value_transformer (uchar *select_arg) override
	Add the field to the select list and substitute it for the reference to the field. More...

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

bool	is_outer_field () const override

Field::geometry_type	get_geometry_type () const override

const CHARSET_INFO *	charset_for_protocol (void) override

void	dbug_print () const

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
	Calculate condition filtering effect for "WHERE field", which implicitly means "WHERE field <> 0". More...

float	get_cond_filter_default_probability (double max_distinct_values, float default_filter) const
	Returns the probability for the predicate "col OP <val>" to be true for a row in the case where no index statistics or range estimates are available for 'col'. More...

bool	alias_name_used () const override

bool	repoint_const_outer_ref (uchar *arg) override
	If this object is the real_item of an Item_ref, repoint the result_field to field. More...

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

void	set_can_use_prefix_key () override

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

bool	strip_db_table_name_processor (uchar *) override
	Generated fields don't need db/table names. More...

virtual bool	is_asterisk () const
	Checks if the current object represents an asterisk select list item. More...

Public Member Functions inherited from Item_ident
	Item_ident (Name_resolution_context context_arg, const char db_name_arg, const char table_name_arg, const char field_name_arg)

	Item_ident (const POS &pos, const char db_name_arg, const char table_name_arg, const char *field_name_arg)

	Item_ident (THD thd, Item_ident item)
	Constructor used by Item_field & Item_*_ref (see Item comment) More...

const char *	full_name () const override

void	set_orignal_db_name (const char *name_arg)

void	set_original_table_name (const char *name_arg)

void	set_original_field_name (const char *name_arg)

const char *	original_db_name () const

const char *	original_table_name () const

const char *	original_field_name () const

bool	aggregate_check_distinct (uchar *arg) override

bool	aggregate_check_group (uchar *arg) override

Bool3	local_column (const Query_block *sl) const override
	Tells if this is a column of a table whose qualifying query block is 'sl'. More...

bool	change_context_processor (uchar *arg) override

bool	is_alias_of_expr () const

void	set_alias_of_expr ()
	Marks that this Item's name is alias of SELECT expression. More...

bool	update_depended_from (uchar *) override

bool	is_strong_side_column_not_in_fd (uchar *arg) override

bool	is_column_not_in_fd (uchar *arg) override

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

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

void	quick_fix_field ()

virtual bool	propagate_type (THD *thd, const Type_properties &type)
	Propagate data type specifications into parameters and user variables. More...

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...

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

void	aggregate_type (Bounds_checked_array< Item * > items)
	Aggregates data types from array of items into current item. 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 ()

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 table_map	not_null_tables () const
	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...

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

virtual uint	decimal_precision () 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, bool used_alias) const
	Prints the item when it's part of ORDER BY and GROUP BY. More...

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

virtual void	split_sum_func (THD , Ref_item_array, mem_root_deque< Item > *)

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

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 bool	is_result_field () const

virtual Field *	get_result_field () const

virtual bool	is_bool_func () const

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 *	compare_collation () const

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

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

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

virtual Item *	transform (Item_transformer transformer, uchar *arg)
	Perform a generic transformation of the Item tree, by adding zero or more additional Item objects to it. More...

virtual Item *	compile (Item_analyzer analyzer, uchar *arg_p, Item_transformer transformer, uchar arg_t)
	Perform a generic "compilation" of the Item tree, ie transform the Item tree by adding zero or more Item objects to it. More...

virtual void	traverse_cond (Cond_traverser traverser, void *arg, traverse_order)

virtual bool	intro_version (uchar *)

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

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

virtual bool	find_item_processor (uchar *arg)

virtual bool	is_non_const_over_literals (uchar *)

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

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

virtual bool	inform_item_in_cond_of_tab (uchar *)

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

virtual bool	collect_scalar_subqueries (uchar *)

virtual bool	collect_grouped_aggregates (uchar *)

virtual bool	collect_subqueries (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	equality_substitution_analyzer (uchar **)

virtual Item *	equality_substitution_transformer (uchar *)

virtual bool	explain_subquery_checker (uchar **)

virtual Item *	explain_subquery_propagator (uchar *)

virtual bool	check_valid_arguments_processor (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_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 *	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 *	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_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...

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...

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, bool binary_cmp, const CHARSET_INFO cs)

virtual bool	is_expensive ()

uint32	max_char_length () const

uint32	max_char_length (const CHARSET_INFO *cs) const

void	fix_char_length (uint32 max_char_length_arg)

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_rollup_expr () const

void	set_rollup_expr ()
	Set the property: this item (tree) contains a reference to a ROLLUP expr. More...

bool	has_grouping_func () const

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

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

void	mark_subqueries_optimized_away ()

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

virtual Item *	gc_subst_transformer (uchar *)
	Transformer function for GC substitution. 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_decimal_properties (Item **item, uint nitems)
	Set precision and decimals of function when this depends on arguments' values for these quantities. More...

void	aggregate_float_properties (Item **item, 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_char_length (Item **args, uint nitems)
	Set the maximum number of characters required by any of the items in args. More...

void	aggregate_temporal_properties (Item **item, uint nitems)
	Set fractional seconds precision for temporal functions. More...

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

void	aggregate_num_type (Item_result result_type, Item **item, uint nitems)
	This function is used to resolve type for numeric result type of CASE, COALESCE, IF and LEAD/LAG. 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 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)
	Do all context-sensitive things and mark the node as contextualized. More...

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
Table_ref *	table_ref
	Table containing this resolved field. More...

Field *	field
	Source field. More...

Item_equal *	item_equal {nullptr}
	Used during optimization to perform multiple equality analysis, this analysis should be performed during preparation instead, so that Item_field can be const after preparation. More...

uint16	field_index
	Index for this field in table->field array. More...

Item_equal *	item_equal_all_join_nests {nullptr}

bool	no_constant_propagation {false}
	If true, the optimizer's constant propagation will not replace this item with an equal constant. More...

Access_bitmask	have_privileges {0}

bool	any_privileges

bool	can_use_prefix_key {false}

Public Attributes inherited from Item_ident
Name_resolution_context *	context
	For regularly resolved column references, 'context' points to a name resolution context object belonging to the query block which simply contains the reference. More...

const char *	db_name
	Schema name of the base table or view the column is part of. More...

const char *	table_name
	If column is from a non-aliased base table or view, name of base table or view. More...

const char *	field_name
	If column is aliased, the column alias name. More...

Table_ref *	cached_table

Query_block *	depended_from

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...

Protected Member Functions
void	set_field (Field *field)

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...

type_conversion_status	save_in_field_inner (Field *field, bool no_conversions) override
	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...

Protected Member Functions inherited from Item_ident
void	print (const THD thd, String str, enum_query_type query_type, const char db_name_arg, const char table_name_arg) const
	Function to print column name for a table. More...

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...

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...

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 ()

Private Types
typedef Item_ident	super

Private Attributes
Field *	result_field {nullptr}
	Result field. More...

Field *	last_org_destination_field {nullptr}

Field *	last_destination_field {nullptr}

uint32_t	last_org_destination_field_memcpyable = ~0U

uint32_t	last_destination_field_memcpyable = ~0U

const Item_field *	m_base_item_field {nullptr}
	If this field is derived from another field, e.g. More...

Additional Inherited Members
Public Types inherited from Item
enum	Type { INVALID_ITEM = 0 , FIELD_ITEM , FUNC_ITEM , SUM_FUNC_ITEM , STRING_ITEM , INT_ITEM , REAL_ITEM , NULL_ITEM , VARBIN_ITEM , METADATA_COPY_ITEM , FIELD_AVG_ITEM , DEFAULT_VALUE_ITEM , PROC_ITEM , COND_ITEM , REF_ITEM , FIELD_STD_ITEM , FIELD_VARIANCE_ITEM , INSERT_VALUE_ITEM , SUBSELECT_ITEM , ROW_ITEM , CACHE_ITEM , TYPE_HOLDER , PARAM_ITEM , TRIGGER_FIELD_ITEM , DECIMAL_ITEM , XPATH_NODESET , XPATH_NODESET_CMP , VIEW_FIXER_ITEM , FIELD_BIT_ITEM , VALUES_COLUMN_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 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_ident
const char *	m_orig_db_name
	The fields m_orig_db_name, m_orig_table_name and m_orig_field_name are maintained so that we can provide information about the origin of a column that may have been renamed within the query, e.g. More...

const char *	m_orig_table_name
	Names the original table that is the source of the field. More...

const char *	m_orig_field_name
	Names the field in the source base table. More...

bool	m_alias_of_expr
	if this Item's name is alias of SELECT expression More...

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_ROLLUP_EXPR = 0x10
	Set if the item or one or more of the underlying items contains a ROLLUP expression. 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...

Member Typedef Documentation

◆ super

typedef Item_ident Item_field::super

private

Constructor & Destructor Documentation

◆ Item_field() [1/5]

Item_field::Item_field	(	Name_resolution_context *	context_arg,
		const char *	db_arg,
		const char *	table_name_arg,
		const char *	field_name_arg
	)

Constructor used for internal information queries.

Parameters

context_arg	Name resolution context
db_arg	Schema name, may be NULL
table_name_arg	Table name, may be NULL if schema name is NULL
field_name_arg	Field name

◆ Item_field() [2/5]

Item_field::Item_field	(	const POS &	pos,
		const char *	db_arg,
		const char *	table_name_arg,
		const char *	field_name_arg
	)

Used from parser to construct column references.

Parameters

pos	Parse context
db_arg	Schema name for column, may be NULL
table_name_arg	Table name for column, may be NULL if db_arg is NULL
field_name_arg	Column name, always given.

◆ Item_field() [3/5]

Item_field::Item_field	(	THD *	thd,
		Item_field *	item
	)

Used to create a copy (clone) of another Item_field.

Item has same lifetime as the copied item.

Parameters

thd	thread handler
item	Column reference to make a copy from.

◆ Item_field() [4/5]

Item_field::Item_field	(	THD *	thd,
		Name_resolution_context *	context_arg,
		Table_ref *	tr,
		Field *	f
	)

Constructor used inside setup_wild().

Item is resolved after construction. Item is supposed to have lifetime same as statement it is created within.

Parameters

thd	thread context
context_arg	Name resolution context for this field
tr	Table reference, provides table and schema name
f	Field reference, provides field name and original table name

◆ Item_field() [5/5]

Item_field::Item_field ( Field * f )

Create column reference based on a table field.

Parameters

f	Pointer to field in a TABLE object

Item is resolved after construction. Notice that lifetime of object is limited to the lifetime of the supplied field.

Member Function Documentation

◆ add_field_to_cond_set_processor()

bool Item_field::add_field_to_cond_set_processor ( uchar * )

overridevirtual

Item::walk function.

Set bit in table->cond_set for all fields of all tables that are referred to by the Item.

Reimplemented from Item.

◆ add_field_to_set_processor()

bool Item_field::add_field_to_set_processor ( uchar * )

overridevirtual

Item::walk function.

Set bit in table->tmp_set for all fields in table 'arg' that are referred to by the Item.

Reimplemented from Item.

◆ alias_name_used()

bool Item_field::alias_name_used ( ) const

inlineoverridevirtual

Note: that field->table->alias_name_used is reliable only if thd->lex->need_correct_ident() is true.

Reimplemented from Item_ident.

◆ base_item_field()

const Item_field * Item_field::base_item_field ( ) const

inline

◆ bind_fields()

void Item_field::bind_fields ( )

overridevirtual

Bind objects from the current execution context to field objects in item trees.

Typically used to bind Field objects from TABLEs to Item_field objects.

Reimplemented from Item.

Reimplemented in Item_default_value, Item_insert_value, and Item_trigger_field.

◆ cast_to_int_type()

Item_result Item_field::cast_to_int_type ( ) const

inlineoverridevirtual

Reimplemented from Item.

◆ charset_for_protocol()

const CHARSET_INFO * Item_field::charset_for_protocol ( void )

inlineoverridevirtual

Reimplemented from Item.

◆ check_column_in_group_by()

bool Item_field::check_column_in_group_by ( uchar * arg )

overridevirtual

Check if this column is found in GROUP BY.

Called when checking to see if a condition can be pushed past GROUP BY while pushing conditions down to materialized derived tables.

Parameters

arg	derived table

Return values

false	if this field is not part of GROUP BY.
true	otherwise.

Reimplemented from Item.

◆ check_column_in_window_functions()

bool Item_field::check_column_in_window_functions ( uchar * arg )

overridevirtual

Check if this column is found in PARTITION clause of all the window functions.

Called when checking to see if a condition can be pushed past window functions while pushing conditions down to materialized derived tables.

Parameters

arg	derived table

Return values

false	if this field is part of PARTITION clause of all window functions present in the derived table.
true	otherwise

Reimplemented from Item.

◆ check_column_privileges()

bool Item_field::check_column_privileges ( uchar * arg )

overridevirtual

Check privileges of base table column.

Reimplemented from Item.

Reimplemented in Item_default_value, and Item_trigger_field.

◆ check_function_as_value_generator()

bool Item_field::check_function_as_value_generator ( uchar * args )

overridevirtual

Check if this item is allowed for a virtual column or inside a default expression.

Should be overridden in child classes.

Parameters

[in,out] args Due to the limitation of Item::walk() it is declared as a pointer to uchar, underneath there's a actually a structure of type Check_function_as_value_generator_parameters. It is used mainly in Item_field.

Returns: true if function is not accepted

Reimplemented from Item.

Reimplemented in Item_insert_value, and Item_trigger_field.

◆ check_partition_func_processor()

bool Item_field::check_partition_func_processor ( uchar * )

inlineoverridevirtual

Check if a partition function is allowed.

Returns: whether a partition function is not accepted

check_partition_func_processor is used to check if a partition function uses an allowed function. An allowed function will always ensure that X=Y guarantees that also part_function(X)=part_function(Y) where X is a set of partition fields and so is Y. The problems comes mainly from character sets where two equal strings can be quite unequal. E.g. the german character for double s is equal to 2 s.

The default is that an item is not allowed in a partition function. Allowed functions can never depend on server version, they cannot depend on anything related to the environment. They can also only depend on a set of fields in the table itself. They cannot depend on other tables and cannot contain any queries and cannot contain udf's or similar. If a new Item class is defined and it inherits from a class that is allowed in a partition function then it is very important to consider whether this should be inherited to the new class. If not the function below should be defined in the new Item class.

The general behaviour is that most integer functions are allowed. If the partition function contains any multi-byte collations then the function check_part_func_fields will report an error on the partition function independent of what functions are used. So the only character sets allowed are single character collation and even for those only a limited set of functions are allowed. The problem with multi-byte collations is that almost every string function has the ability to change things such that two strings that are equal will not be equal after manipulated by a string function. E.g. two strings one contains a double s, there is a special german character that is equal to two s. Now assume a string function removes one character at this place, then in one the double s will be removed and in the other there will still be one s remaining and the strings are no longer equal and thus the partition function will not sort equal strings into the same partitions.

So the check if a partition function is valid is two steps. First check that the field types are valid, next check that the partition function is valid. The current set of partition functions valid assumes that there are no multi-byte collations amongst the partition fields.

Reimplemented from Item.

◆ cleanup()

void Item_field::cleanup ( )

overridevirtual

Called for every Item after use (preparation and execution).

Release all allocated resources, such as dynamic memory. Prepare for new execution by clearing cached values. Do not remove values allocated during preparation, destructor handles this.

Reimplemented from Item.

Reimplemented in Item_default_value, Item_insert_value, and Item_trigger_field.

◆ collect_item_field_or_ref_processor()

bool Item_field::collect_item_field_or_ref_processor ( uchar * arg )

overridevirtual

When collecting information about columns when transforming correlated scalar subqueries using derived tables, we need to decide which duplicates, if any, to retain:

Local columns are collected once, duplicates are ignored.
All columns that are outer references are included, regardless of being duplicates. This is so we can properly reset outer status for all occurences, cf. Query_block::decorrelate_derived_scalar_subquery_post where we reset Item::depended_from.

Parameters

arg	A pointer to an object of type Collect_item_fields_or_refs, a subclass of Item_tree_walker, which holds the already collected columns.

Returns: true on error

Reimplemented from Item.

◆ collect_item_field_or_view_ref_processor()

bool Item_field::collect_item_field_or_view_ref_processor ( uchar * )

overridevirtual

Collects fields and view references that have the qualifying table in the specified query block.

Reimplemented from Item.

Reimplemented in Item_default_value.

◆ collect_item_field_processor()

bool Item_field::collect_item_field_processor ( uchar * arg )

overridevirtual

Store the pointer to this item field into a list if not already there.

The method is used by Item::walk to collect all unique Item_field objects from a tree of Items into a set of items represented as a list.

Item_cond::walk() and Item_func::walk() stop the evaluation of the processor function for its arguments once the processor returns true.Therefore in order to force this method being called for all item arguments in a condition the method must return false.

Parameters

arg	pointer to a mem_root_deque<Item_field *>

Returns: false to force the evaluation of collect_item_field_processor for the subsequent items.

Reimplemented from Item.

◆ dbug_print()

void Item_field::dbug_print ( ) const

inline

◆ disable_constant_propagation()

bool Item_field::disable_constant_propagation ( uchar * )

inlineoverridevirtual

Reimplemented from Item.

◆ eq()

bool Item_field::eq	(	const Item *	item,
		bool	binary_cmp
	)		const

overridevirtual

This function is called when:

Comparing items in the WHERE clause (when doing where optimization)
When trying to find an ORDER BY/GROUP BY item in the SELECT part
When matching fields in multiple equality objects (Item_equal)

Reimplemented from Item.

Reimplemented in Item_default_value, Item_insert_value, and Item_trigger_field.

◆ equal_fields_propagator()

Item * Item_field::equal_fields_propagator ( uchar * arg )

overridevirtual

If field matches a multiple equality, set a pointer to that object in the field.

Also return a pointer to a constant value that can be substituted for a field (if any).

A constant value is returned only if certain conditions are met (see implementation).

In addition, a numeric field with a zerofill attribute can be substituted with a zerofilled value if it is to be used in a character string context.

Parameters

arg	reference to list of multiple equalities where the field (this object) is to be looked for

Note: This function is supposed to be called as a callback parameter in calls of the compile method.

Returns

pointer to the replacing constant item, if the field item was substituted
pointer to the field item, otherwise.

Reimplemented from Item.

◆ field_for_view_update()

Item_field * Item_field::field_for_view_update ( )

inlineoverridevirtual

Reimplemented from Item.

◆ find_field_processor()

bool Item_field::find_field_processor ( uchar * )

inlineoverridevirtual

Is this an Item_field which references the given Field argument?

Reimplemented from Item.

◆ find_item_equal()

Item_equal * Item_field::find_item_equal ( COND_EQUAL * cond_equal ) const

Find a field among specified multiple equalities.

The function first searches the field among multiple equalities of the current level (in the cond_equal->current_level list). If it fails, it continues searching in upper levels accessed through a pointer cond_equal->upper_levels. The search terminates as soon as a multiple equality containing the field is found.

Parameters

cond_equal reference to list of multiple equalities where the field (this object) is to be looked for

Returns

First Item_equal containing the field, if success
nullptr, otherwise

◆ find_item_in_field_list_processor()

bool Item_field::find_item_in_field_list_processor ( uchar * arg )

overridevirtual

Check if an Item_field references some field from a list of fields.

Check whether the Item_field represented by 'this' references any of the fields in the keyparts passed via 'arg'. Used with the method Item::walk() to test whether any keypart in a sequence of keyparts is referenced in an expression.

Parameters

arg	Field being compared, arg must be of type Field

Return values

true	if 'this' references the field 'arg'
false	otherwise

Reimplemented from Item.

◆ fix_after_pullout()

void Item_field::fix_after_pullout	(	Query_block *	parent_query_block,
		Query_block *	removed_query_block
	)

inlineoverrideprotectedvirtual

Fix after tables have been moved from one query_block level to the parent level, e.g by semijoin conversion.

Basically re-calculate all attributes dependent on the tables.

Parameters

parent_query_block	query_block that tables are moved to.
removed_query_block	query_block that tables are moved away from, child of parent_query_block.

Reimplemented from Item_ident.

◆ fix_fields()

bool Item_field::fix_fields	(	THD *	thd,
		Item **	reference
	)

overridevirtual

Resolve the name of a column reference.

The method resolves the column reference represented by 'this' as a column present in one of: FROM clause, SELECT clause, GROUP BY clause of a query Q, or in outer queries that contain Q.

The name resolution algorithm used is (where [T_j] is an optional table name that qualifies the column name):

resolve_column_reference([T_j].col_ref_i)
{
  search for a column or derived column named col_ref_i
  [in table T_j] in the FROM clause of Q;
 
  if such a column is NOT found AND    // Lookup in outer queries.
     there are outer queries
  {
    for each outer query Q_k beginning from the inner-most one
    {
      search for a column or derived column named col_ref_i
      [in table T_j] in the FROM clause of Q_k;
 
      if such a column is not found
        Search for a column or derived column named col_ref_i
        [in table T_j] in the SELECT and GROUP clauses of Q_k.
    }
  }
}

Notice that compared to Item_ref::fix_fields, here we first search the FROM clause, and then we search the SELECT and GROUP BY clauses.

For the case where a table reference is already set for the field, we just need to make a call to set_field(). This is true for a cloned field used during condition pushdown to derived tables. A cloned field inherits table reference, depended_from, cached_table, context and field from the original field. set_field() ensures all other members are set correctly.

Parameters

[in]	thd	current thread
[in,out]	reference	view column if this item was resolved to a view column

Returns: false on success, true on error

Reimplemented from Item.

Reimplemented in Item_asterisk, Item_default_value, Item_insert_value, and Item_trigger_field.

◆ fix_outer_field()

int Item_field::fix_outer_field	(	THD *	thd,
		Field **	from_field,
		Item **	reference
	)

Resolve the name of an outer select column reference.

The method resolves the column reference represented by 'this' as a column present in outer selects that contain current select.

In prepared statements, because of cache, find_field_in_tables() can resolve fields even if they don't belong to current context. In this case this method only finds appropriate context and marks current select as dependent. The found reference of field should be provided in 'from_field'.

Parameters

[in]	thd	current thread
[in,out]	from_field	found field reference or (Field*)not_found_field
[in,out]	reference	view column if this item was resolved to a view column

Note: This is the inner loop of Item_field::fix_fields:
for each outer query Q_k beginning from the inner-most one

{

search for a column or derived column named col_ref_i

[in table T_j] in the FROM clause of Q_k;

if such a column is not found

Search for a column or derived column named col_ref_i

[in table T_j] in the SELECT and GROUP clauses of Q_k.

}

Return values

1	column succefully resolved and fix_fields() should continue.
0	column fully fixed and fix_fields() should return false
-1	error occurred

◆ get_cond_filter_default_probability()

float Item_field::get_cond_filter_default_probability	(	double	max_distinct_values,
		float	default_filter
	)		const

Returns the probability for the predicate "col OP <val>" to be true for a row in the case where no index statistics or range estimates are available for 'col'.

The probability depends on the number of rows in the table: it is by default 'default_filter', but never lower than 1/max_distinct_values (e.g. number of rows in the table, or the number of distinct values possible for the datatype if the field provides that kind of information).

Parameters

max_distinct_values	The maximum number of distinct values, typically the number of rows in the table
default_filter	The default filter for the predicate

Returns: the estimated filtering effect for this predicate

◆ get_date()

bool Item_field::get_date	(	MYSQL_TIME *	ltime,
		my_time_flags_t	fuzzydate
	)

overridevirtual

Implements Item.

◆ get_filtering_effect()

float Item_field::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

Calculate condition filtering effect for "WHERE field", which implicitly means "WHERE field <> 0".

The filtering effect is therefore identical to that of Item_func_ne.

Reimplemented from Item.

◆ get_geometry_type()

Field::geometry_type Item_field::get_geometry_type ( ) const

inlineoverridevirtual

Reimplemented from Item.

◆ get_monotonicity_info()

enum_monotonicity_info Item_field::get_monotonicity_info ( ) const

inlineoverridevirtual

Reimplemented from Item.

◆ get_time()

bool Item_field::get_time ( MYSQL_TIME * ltime )

overridevirtual

Implements Item.

◆ get_timeval()

bool Item_field::get_timeval	(	my_timeval *	tm,
		int *	warnings
	)

overridevirtual

Get timestamp in "struct timeval" format.

If argument is NULL, sets null_value.

Return values

false	on success
true	on error

Otherwise: if invalid DATETIME value, or a valid DATETIME value but which is out of the supported Unix timestamp range, sets 'tm' to 0.

Reimplemented from Item.

◆ get_tmp_table_field()

Field * Item_field::get_tmp_table_field ( )

inlineoverridevirtual

If this Item is being materialized into a temporary table, returns the field that is being materialized into.

(Typically, this is the “result_field” members for items that have one.)

Reimplemented from Item.

Reimplemented in Item_trigger_field.

◆ get_tmp_table_item()

Item * Item_field::get_tmp_table_item ( THD * thd )

overridevirtual

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.

For instance, if the Item was an Item_field, the new Item_field needs to point into the temporary table instead of the original one, but if, on the other hand, the Item was a literal constant, it can be reused as-is. This function encapsulates these policies for the different kinds of Items. See also get_tmp_table_field().

TODO: Document how aggregate functions (Item_sum) are handled.

Reimplemented from Item.

Reimplemented in Item_default_value, and Item_trigger_field.

◆ get_typelib()

TYPELIB * Item_field::get_typelib ( ) const

overridevirtual

Get the typelib information for an item of type set or enum.

Reimplemented from Item.

◆ is_asterisk()

virtual bool Item_field::is_asterisk ( ) const

inlinevirtual

Checks if the current object represents an asterisk select list item.

Returns: false if a regular column reference, true if an asterisk select list item.

Reimplemented in Item_asterisk.

◆ is_null()

bool Item_field::is_null ( )

inlineoverridevirtual

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

Used in Item_func_isnull/Item_func_isnotnull and Item_sum_count/Item_sum_count_distinct. Any item which can be NULL must implement this method.

Return values

false	if the expression is not NULL.
true	if the expression is NULL, or evaluation caused an error. The null_value member is set according to the return value.

Reimplemented from Item.

◆ is_outer_field()

bool Item_field::is_outer_field ( ) const

inlineoverridevirtual

Reimplemented from Item.

◆ is_valid_for_pushdown()

bool Item_field::is_valid_for_pushdown ( uchar * arg )

overridevirtual

Check if all the columns present in this expression are from the derived table.

Used in determining if a condition can be pushed down to derived table.

Reimplemented from Item.

Reimplemented in Item_trigger_field.

◆ itemize()

bool Item_field::itemize	(	Parse_context *	pc,
		Item **	res
	)

overridevirtual

The same as contextualize() but with additional parameter.

This function finalize the construction of Item objects (see the Item(POS) constructor): we can access/change parser contexts from the itemize() function.

Parameters

	pc	current parse context
[out]	res	pointer to "this" or to a newly allocated replacement object to use in the Item tree instead

Return values

false	success
true	syntax/OOM/etc error

Reimplemented from Item_ident.

Reimplemented in Item_asterisk, Item_default_value, and Item_insert_value.

◆ make_field()

void Item_field::make_field ( Send_field * tmp_field )

overridevirtual

Reimplemented from Item.

◆ mark_field_in_map()

bool Item_field::mark_field_in_map ( uchar * arg )

inlineoverridevirtual

Mark underlying field in read or write map of a table.

Parameters

arg	Mark_field object

Reimplemented from Item.

◆ max_disp_length()

uint32 Item_field::max_disp_length ( )

inline

◆ numeric_context_result_type()

Item_result Item_field::numeric_context_result_type ( ) const

inlineoverridevirtual

Result type when an item appear in a numeric context.

See Field::numeric_context_result_type() for more comments.

Reimplemented from Item.

◆ print()

void Item_field::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_ident.

Reimplemented in Item_default_value, Item_insert_value, and Item_trigger_field.

◆ remove_column_from_bitmap()

bool Item_field::remove_column_from_bitmap ( uchar * arg )

overridevirtual

Visitor interface for removing all column expressions (Item_field) in this expression tree from a bitmap.

See also: walk()

Parameters

arg	A MY_BITMAP* cast to unsigned char*, where the bits represent Field::field_index values.

Reimplemented from Item.

◆ replace_equal_field()

Item * Item_field::replace_equal_field ( uchar * )

overridevirtual

Replace an Item_field for an equal Item_field that evaluated earlier (if any).

The function returns a pointer to an item that is taken from the very beginning of the item_equal list which the Item_field object refers to (belongs to) unless item_equal contains a constant item. In this case the function returns this constant item, (if the substitution does not require conversion). If the Item_field object does not refer any Item_equal object 'this' is returned .

Note: This function is supposed to be called as a callback parameter in calls of the thransformer method.

Returns

pointer to a replacement Item_field if there is a better equal item or a pointer to a constant equal item;
this - otherwise.

Reimplemented from Item.

◆ replace_field_processor()

bool Item_field::replace_field_processor ( uchar * )

overridevirtual

A processor that replaces any Fields with a Create_field_wrapper.

This will allow us to resolve functions during CREATE TABLE, where we only have Create_field available and not Field. Used for functional index implementation.

Reimplemented from Item.

◆ replace_item_field()

Item * Item_field::replace_item_field ( uchar * arg )

overridevirtual

If this field is the target is the target of replacement, replace it with the info object's item or, if the item is found inside a subquery, the target is an outer reference, so we create a new Item_field, mark it accordingly and replace with that instead.

Parameters

arg	An info object of type Item::Item_field_replacement.

Returns: the resulting item, replaced or not, or nullptr if error

Reimplemented from Item.

Reimplemented in Item_default_value.

◆ replace_with_derived_expr()

Item * Item_field::replace_with_derived_expr ( uchar * arg )

overridevirtual

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.

We replace with a clone, because the condition can be pushed further down in case of nested derived tables.

Reimplemented from Item.

◆ replace_with_derived_expr_ref()

Item * Item_field::replace_with_derived_expr_ref ( uchar * arg )

overridevirtual

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.

Unlike replace_with_derived_expr, a clone is not used because HAVING condition will not be pushed further down in case of nested derived tables.

Reimplemented from Item.

◆ repoint_const_outer_ref()

bool Item_field::repoint_const_outer_ref ( uchar * arg )

overridevirtual

If this object is the real_item of an Item_ref, repoint the result_field to field.

Reimplemented from Item.

◆ reset_field() [1/2]

void Item_field::reset_field ( )

Reset all aspect of a field object, so that it can be re-resolved.

This is only for use in prepared CREATE TABLE statements.

◆ reset_field() [2/2]

void Item_field::reset_field ( Field * f )

Reset this item to point to a field from the new temporary table.

This is used when we create a new temporary table for each execution of prepared statement.

◆ result_type()

Item_result Item_field::result_type ( ) const

inlineoverridevirtual

Reimplemented from Item.

◆ returns_array()

bool Item_field::returns_array ( ) const

inlineoverridevirtual

Whether the item returns array of its data type.

Reimplemented from Item.

◆ safe_charset_converter()

Item * Item_field::safe_charset_converter	(	THD *	thd,
		const CHARSET_INFO *	tocs
	)

overridevirtual

Reimplemented from Item.

◆ save_in_field_inner()

type_conversion_status Item_field::save_in_field_inner	(	Field *	field,
		bool	no_conversions
	)

overrideprotectedvirtual

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.

Subclasses that need to specialize the behaviour of save_in_field(), should override this function instead of save_in_field().

Parameters

[in,out]	field	the field to save the item into
	no_conversions	whether or not to allow conversions of the value

Returns: the status from saving into the field

Return values

TYPE_OK	item saved without any errors or warnings
!=	TYPE_OK there were errors or warnings when saving the item

Reimplemented from Item.

Reimplemented in Item_default_value, and Item_insert_value.

◆ save_org_in_field()

void Item_field::save_org_in_field ( Field * field )

overridevirtual

Set a field's value from a item.

Reimplemented from Item.

◆ send()

bool Item_field::send	(	Protocol *	protocol,
		String *	str
	)

overridevirtual

This is only called from items that is not of type item_field.

Reimplemented from Item.

◆ set_base_item_field()

void Item_field::set_base_item_field ( const Item_field * item )

inline

◆ set_can_use_prefix_key()

void Item_field::set_can_use_prefix_key ( )

inlineoverridevirtual

Reimplemented from Item.

◆ set_field()

void Item_field::set_field ( Field * field )

protected

◆ set_item_equal()

void Item_field::set_item_equal ( Item_equal * item_equal_arg )

inline

◆ set_item_equal_all_join_nests()

void Item_field::set_item_equal_all_join_nests ( Item_equal * item_equal )

inline

◆ set_result_field()

void Item_field::set_result_field ( Field * field_arg )

inlineoverridevirtual

Reimplemented from Item.

◆ strip_db_table_name_processor()

bool Item_field::strip_db_table_name_processor ( uchar * )

overridevirtual

Generated fields don't need db/table names.

Strip them off as inplace ALTER can reallocate them, making pointers invalid.

Reimplemented from Item.

◆ subst_argument_checker()

bool Item_field::subst_argument_checker ( uchar ** arg )

overridevirtual

Check whether a field can be substituted by an equal item.

The function checks whether a substitution of the field occurrence for an equal item is valid.

Parameters

arg	*arg != NULL <-> the field is in the context where substitution for an equal item is valid

Note: The following statement is not always true:
x=y => F(x)=F(x/y).
This means substitution of an item for an equal item not always yields an equavalent condition. Here's an example:
'a'='a '

(LENGTH('a')=1) != (LENGTH('a ')=2)

Such a substitution is surely valid if either the substituted field is not of a STRING type or if it is an argument of a comparison predicate.

Return values

true	substitution is valid
false	otherwise

Reimplemented from Item.

◆ tmp_table_field()

Field * Item_field::tmp_table_field ( TABLE * )

inlineoverridevirtual

Reimplemented from Item.

◆ type()

enum Type Item_field::type ( ) const

inlineoverridevirtual

Implements Item.

Reimplemented in Item_default_value, Item_insert_value, and Item_trigger_field.

◆ update_value_transformer()

Item * Item_field::update_value_transformer ( uchar * select_arg )

overridevirtual

Add the field to the select list and substitute it for the reference to the field.

If the field doesn't belong to the table being inserted into then it is added to the select list, pointer to it is stored in the ref_item_array of the select and the field itself is substituted for the Item_ref object. This is done in order to get correct values from update fields that belongs to the SELECT part in the INSERT .. SELECT .. ON DUPLICATE KEY UPDATE statement.

Return values

nullptr	if an error occurred
ref	if all conditions are met
this	field otherwise

Reimplemented from Item.

◆ used_tables()

table_map Item_field::used_tables ( ) const

overridevirtual

Reimplemented from Item.

Reimplemented in Item_default_value, Item_insert_value, and Item_trigger_field.

◆ used_tables_for_level()

bool Item_field::used_tables_for_level ( uchar * arg )

overridevirtual

Return used table information for the specified query block (level).

For a field that is resolved from this query block, return the table number. For a field that is resolved from a query block outer to the specified one, return OUTER_REF_TABLE_BIT

Parameters

[in,out] arg pointer to an instance of class Used_tables, which is constructed with the query block as argument. The used tables information is accumulated in the field used_tables in this class.

Note: This function is used to update used tables information after merging a query block (a subquery) with its parent.

Reimplemented from Item.

◆ val_date_temporal()

longlong Item_field::val_date_temporal ( )

overridevirtual

Return date value of item in packed longlong format.

Reimplemented from Item.

◆ val_date_temporal_at_utc()

longlong Item_field::val_date_temporal_at_utc ( )

overridevirtual

Reimplemented from Item.

◆ val_decimal()

my_decimal * Item_field::val_decimal ( my_decimal * decimal_value )

overridevirtual

Implements Item.

◆ val_int()

longlong Item_field::val_int ( void )

overridevirtual

Implements Item.

◆ val_int_endpoint()

longlong Item_field::val_int_endpoint	(	bool	left_endp,
		bool *	incl_endp
	)

overridevirtual

Reimplemented from Item.

◆ val_json()

bool Item_field::val_json ( Json_wrapper * result )

overridevirtual

Get a JSON value from an Item.

All subclasses that can return a JSON value, should override this function. The function in the base class is not expected to be called. If it is called, it most likely means that some subclass is missing an override of val_json().

Parameters

[in,out] result The resulting Json_wrapper.

Returns: false if successful, true on failure

Reimplemented from Item.

◆ val_real()

double Item_field::val_real ( void )

overridevirtual

Implements Item.

◆ val_str()

String * Item_field::val_str ( String * str )

overridevirtual

Implements Item.

◆ val_time_temporal()

longlong Item_field::val_time_temporal ( )

overridevirtual

Return time value of item in packed longlong format.

Reimplemented from Item.

◆ val_time_temporal_at_utc()

longlong Item_field::val_time_temporal_at_utc ( )

overridevirtual

Reimplemented from Item.

Member Data Documentation

◆ any_privileges

bool Item_field::any_privileges

◆ can_use_prefix_key

bool Item_field::can_use_prefix_key {false}

◆ field

Field* Item_field::field

Source field.

◆ field_index

uint16 Item_field::field_index

Index for this field in table->field array.

Holds NO_FIELD_INDEX if index value is not known.

◆ have_privileges

Access_bitmask Item_field::have_privileges {0}

◆ item_equal

Item_equal* Item_field::item_equal {nullptr}

Used during optimization to perform multiple equality analysis, this analysis should be performed during preparation instead, so that Item_field can be const after preparation.

◆ item_equal_all_join_nests

Item_equal* Item_field::item_equal_all_join_nests {nullptr}

◆ last_destination_field

Field* Item_field::last_destination_field {nullptr}

private

◆ last_destination_field_memcpyable

uint32_t Item_field::last_destination_field_memcpyable = ~0U

private

◆ last_org_destination_field

Field* Item_field::last_org_destination_field {nullptr}

private

◆ last_org_destination_field_memcpyable

uint32_t Item_field::last_org_destination_field_memcpyable = ~0U

private

◆ m_base_item_field

const Item_field* Item_field::m_base_item_field {nullptr}

private

If this field is derived from another field, e.g.

it is reading a column from a temporary table which is populated from a base table, this member points to the field used to populate the temporary table column.

◆ no_constant_propagation

bool Item_field::no_constant_propagation {false}

If true, the optimizer's constant propagation will not replace this item with an equal constant.

◆ result_field

Field* Item_field::result_field {nullptr}

private

Result field.

◆ table_ref

Table_ref* Item_field::table_ref

Table containing this resolved field.

This is required e.g for calculation of table map. Notice that for the following types of "tables", no Table_ref object is assigned and hence table_ref is NULL:

Temporary tables assigned by join optimizer for sorting and aggregation.
Stored procedure dummy tables. For fields referencing such tables, table number is always 0, and other uses of table_ref is not needed.

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

Public Member Functions

Public Attributes

Protected Member Functions

Private Types

Private Attributes

Additional Inherited Members

Member Typedef Documentation

◆ super

Constructor & Destructor Documentation

◆ Item_field() [1/5]

◆ Item_field() [2/5]

◆ Item_field() [3/5]

◆ Item_field() [4/5]

◆ Item_field() [5/5]

Member Function Documentation

◆ add_field_to_cond_set_processor()

◆ add_field_to_set_processor()

◆ alias_name_used()

◆ base_item_field()

◆ bind_fields()

◆ cast_to_int_type()

◆ charset_for_protocol()

◆ check_column_in_group_by()

◆ check_column_in_window_functions()

◆ check_column_privileges()

◆ check_function_as_value_generator()

◆ check_partition_func_processor()

◆ cleanup()

◆ collect_item_field_or_ref_processor()

◆ collect_item_field_or_view_ref_processor()

◆ collect_item_field_processor()

◆ dbug_print()

◆ disable_constant_propagation()

◆ eq()

◆ equal_fields_propagator()

◆ field_for_view_update()

◆ find_field_processor()

◆ find_item_equal()

◆ find_item_in_field_list_processor()

◆ fix_after_pullout()

◆ fix_fields()

◆ fix_outer_field()

◆ get_cond_filter_default_probability()

◆ get_date()

◆ get_filtering_effect()

◆ get_geometry_type()

◆ get_monotonicity_info()

◆ get_time()

◆ get_timeval()

◆ get_tmp_table_field()

◆ get_tmp_table_item()

◆ get_typelib()

◆ is_asterisk()

◆ is_null()

◆ is_outer_field()

◆ is_valid_for_pushdown()

◆ itemize()

◆ make_field()

◆ mark_field_in_map()

◆ max_disp_length()

◆ numeric_context_result_type()

◆ print()

◆ remove_column_from_bitmap()

◆ replace_equal_field()

◆ replace_field_processor()

◆ replace_item_field()

◆ replace_with_derived_expr()

◆ replace_with_derived_expr_ref()

◆ repoint_const_outer_ref()

◆ reset_field() [1/2]

◆ reset_field() [2/2]

◆ result_type()

◆ returns_array()

◆ safe_charset_converter()

◆ save_in_field_inner()

◆ save_org_in_field()

◆ send()

◆ set_base_item_field()

◆ set_can_use_prefix_key()

◆ set_field()