item.h File Reference

#include <sys/types.h>
#include <cfloat>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <memory>
#include <new>
#include <optional>
#include <string>
#include <type_traits>
#include <vector>
#include "decimal.h"
#include "field_types.h"
#include "lex_string.h"
#include "memory_debugging.h"
#include "my_alloc.h"
#include "my_bitmap.h"
#include "my_compiler.h"
#include "my_dbug.h"
#include "my_double2ulonglong.h"
#include "my_inttypes.h"
#include "my_sys.h"
#include "my_table_map.h"
#include "my_time.h"
#include "mysql/strings/dtoa.h"
#include "mysql/strings/m_ctype.h"
#include "mysql/strings/my_strtoll10.h"
#include "mysql/udf_registration_types.h"
#include "mysql_com.h"
#include "mysql_time.h"
#include "mysqld_error.h"
#include "nulls.h"
#include "sql-common/my_decimal.h"
#include "sql/auth/auth_acls.h"
#include "sql/enum_query_type.h"
#include "sql/field.h"
#include "sql/mem_root_array.h"
#include "sql/parse_location.h"
#include "sql/parse_tree_node_base.h"
#include "sql/sql_array.h"
#include "sql/sql_const.h"
#include "sql/sql_list.h"
#include "sql/table.h"
#include "sql/table_trigger_field_support.h"
#include "sql/thr_malloc.h"
#include "sql/trigger_def.h"
#include "sql_string.h"
#include "string_with_len.h"
#include "template_utils.h"

Go to the source code of this file.

Classes
class	DTCollation
class	Mark_field
	Class used as argument to Item::walk() together with mark_field_in_map() More...
class	Used_tables
	Class used as argument to Item::walk() together with used_tables_for_level() More...
class	Name_string
	Storage for name strings. More...
class	Item_name_string
	Storage for Item names. More...
struct	Name_resolution_context
	Instances of Name_resolution_context store the information necessary for name resolution of Items and other context analysis of a query made in fix_fields(). More...
struct	Check_function_as_value_generator_parameters
	Struct used to pass around arguments to/from check_function_as_value_generator. More...
class	Name_resolution_context_state
class	Bool3
	A type for SQL-like 3-valued Booleans: true/false/unknown. More...
class	Type_properties
	Type properties, used to collect type information for later assignment to an Item object. More...
class	Settable_routine_parameter
class	Item_tree_walker
	Utility mixin class to be able to walk() only parts of item trees. More...
class	CostOfItem
	This class represents the cost of evaluating an Item. More...
struct	ContainedSubquery
	This class represents a subquery contained in some subclass of Item_subselect,. More...
class	Item
	Base class that is used to represent any kind of expression in a relational query. More...
class	Item::Collect_item_fields_or_refs
class	Item::Collect_item_fields_or_view_refs
class	Item::Cleanup_after_removal_context
	Context object for (functions that override) Item::clean_up_after_removal(). More...
struct	Item::Css_info
	Minion class under Collect_scalar_subquery_info ("Css"). More...
struct	Item::Collect_scalar_subquery_info
	Context struct used by walk method collect_scalar_subqueries to accumulate information about scalar subqueries found. More...
struct	Item::Replace_equal
struct	Item::Item_replacement
struct	Item::Item_field_replacement
struct	Item::Item_func_call_replacement
struct	Item::Item_view_ref_replacement
struct	Item::Aggregate_replacement
struct	Item::Aggregate_ref_update
struct	cache_const_expr_arg
	Descriptor of what and how to cache for Item::cache_const_expr_transformer/analyzer. More...
class	Item_basic_constant
class	Item_sp_variable
class	Item_splocal
class	Item_case_expr
class	Item_name_const
class	Item_num
class	Item_ident
struct	Item_ident::Change_context
	< Argument object to change_context_processor More...
struct	Item_ident::Depended_change
	Argument structure for walk processor Item::update_depended_from. More...
class	Item_ident_for_show
class	Item_field
class	Item_asterisk
	Represents [schema. More...
class	Item_null
class	Item_param
	Dynamic parameters used as placeholders ('?') inside prepared statements. More...
class	Item_int
class	Item_int_0
	Item_int with value==0 and length==1. More...
class	Item_temporal
class	Item_uint
class	Item_decimal
class	Item_float
class	Item_func_pi
class	Item_string
class	Item_static_string_func
class	Item_partition_func_safe_string
class	Item_blob
class	Item_empty_string
	Item_empty_string – is a utility class to put an item into List<Item> which is then used in protocol.send_result_set_metadata() when sending SHOW output to the client. More...
class	Item_return_int
class	Item_hex_string
class	Item_bin_string
class	Item_result_field
	Item with result field. More...
class	Item_ref
class	Item_view_ref
	Class for fields from derived tables and views. More...
class	Item_outer_ref
class	Item_ref_null_helper
class	Item_int_with_ref
class	Item_temporal_with_ref
class	Item_datetime_with_ref
class	Item_time_with_ref
class	Cached_item
	This is used for segregating rows in groups (e.g. More...
class	Cached_item_str
class	Cached_item_json
	Cached_item subclass for JSON values. More...
class	Cached_item_real
class	Cached_item_int
class	Cached_item_temporal
class	Cached_item_decimal
class	Item_default_value
class	Item_insert_value
class	Item_trigger_field
	Represents NEW/OLD version of field of row which is changed/read in trigger. More...
class	Item_cache
class	Item_cache_int
class	Item_cache_bit
	Cache class for BIT type expressions. More...
class	Item_cache_real
class	Item_cache_decimal
class	Item_cache_str
class	Item_cache_row
class	Item_cache_datetime
class	Item_cache_json
	An item cache for values of type JSON. More...
class	Item_aggregate_type
	Interface for storing an aggregation of type and type specification of multiple Item objects. More...
class	Item_type_holder
	Item_type_holder stores an aggregation of name, type and type specification of UNIONS and derived tables. More...
class	Item_values_column
	Reference item that encapsulates both the type and the contained items of a single column of a VALUES ROW query expression. More...
class	Item_json
	A class that represents a constant JSON value. More...

Macros
#define	MY_COLL_ALLOW_SUPERSET_CONV   1
#define	MY_COLL_ALLOW_COERCIBLE_CONV   2
#define	MY_COLL_ALLOW_NONE   4
#define	MY_COLL_ALLOW_NUMERIC_CONV   8
#define	MY_COLL_CMP_CONV    (MY_COLL_ALLOW_SUPERSET_CONV | MY_COLL_ALLOW_COERCIBLE_CONV)
#define	NAME_STRING(x)   Name_string(STRING_WITH_LEN(x))
#define	ITEM_TO_QUERY_SUBSTRING_CHAR_LIMIT   (300)
	Max length of an Item string for its use in an error message. More...

Typedefs
typedef Bounds_checked_array< Item * >	Ref_item_array
typedef enum monotonicity_info	enum_monotonicity_info
typedef bool(Item::*	Item_analyzer) (uchar **argp)
typedef Item *(Item::*	Item_transformer) (uchar *arg)
	Type for transformers used by Item::transform and Item::compile. More...
typedef void(*	Cond_traverser) (const Item *item, void *arg)

Enumerations
enum	monotonicity_info {   NON_MONOTONIC , MONOTONIC_INCREASING , MONOTONIC_INCREASING_NOT_NULL , MONOTONIC_STRICT_INCREASING ,   MONOTONIC_STRICT_INCREASING_NOT_NULL }

Functions
void	item_init (void)
	Init all special items. More...
static uint32	char_to_byte_length_safe (uint32 char_length_arg, uint32 mbmaxlen_arg)
Item_result	numeric_context_result_type (enum_field_types data_type, Item_result result_type, uint8 decimals)
template<typename T >
void	SafeIncrement (T *num)
	Increment *num if it is less than its maximal value. More...
template<class T >
bool	WalkItem (Item *item, enum_walk walk, T &&functor)
	A helper class to give in a functor to Item::walk(). More...
template<class T >
bool	WalkItem (const Item *item, enum_walk walk, T &&functor)
	Overload for const 'item' and functor taking 'const Item*' argument. More...
template<class T , class U >
Item *	CompileItem (Item *item, T &&analyzer, U &&transformer)
	Same as WalkItem, but for Item::compile(). More...
template<class T >
Item *	TransformItem (Item *item, T &&transformer)
	Same as WalkItem, but for Item::transform(). More...
bool	convert_const_strings (DTCollation &coll, Item **args, uint nargs)
	Convert constant strings according to a specific character set/collation. More...
bool	agg_item_collations_for_comparison (DTCollation &c, const char *name, Item **items, uint nitems)
	Aggregate collations for items used in a comparison operations. More...
bool	agg_item_charsets (DTCollation &c, const char *name, Item **items, uint nitems, uint flags)
bool	agg_item_charsets_for_string_result (DTCollation &c, const char *name, Item **items, uint nitems)
bool	agg_item_charsets_for_comparison (DTCollation &c, const char *name, Item **items, uint nitems)
constexpr uint16	NO_FIELD_INDEX ((uint16)(-1))
Item_field *	FindEqualField (Item_field *item_field, table_map reachable_tables, bool replace, bool *found)
longlong	longlong_from_string_with_check (const CHARSET_INFO *cs, const char *cptr, const char *end, int unsigned_target)
	Converts a string to a longlong integer, with warnings. More...
double	double_from_string_with_check (const CHARSET_INFO *cs, const char *cptr, const char *end)
Cached_item *	new_Cached_item (THD *thd, Item *item)
	Create right type of Cached_item for an item. More...
Item_result	item_cmp_type (Item_result a, Item_result b)
bool	resolve_const_item (THD *thd, Item **ref, Item *cmp_item)
	Substitute a const item with a simpler const item, if possible. More...
int	stored_field_cmp_to_item (THD *thd, Field *field, Item *item)
	Compare the value stored in field with the expression from the query. More...
bool	is_null_on_empty_table (THD *thd, Item_field *i)
	Check if the column reference that is currently being resolved, will be set to NULL if its qualifying query returns zero rows. More...
void	convert_and_print (const String *from_str, String *to_str, const CHARSET_INFO *to_cs)
	Helper method: Convert string to the given charset, then print. More...
std::string	ItemToString (const Item *item, enum_query_type q_type)
std::string	ItemToString (const Item *item)
std::string	ItemToQuerySubstrNoCharLimit (const Item *item)
std::string	ItemToQuerySubstr (const Item *item, const LEX *lex=nullptr, uint32 char_limit=ITEM_TO_QUERY_SUBSTRING_CHAR_LIMIT)
size_t	CountVisibleFields (const mem_root_deque< Item * > &fields)
size_t	CountHiddenFields (const mem_root_deque< Item * > &fields)
Item *	GetNthVisibleField (const mem_root_deque< Item * > &fields, size_t index)
bool	ItemsAreEqual (const Item *a, const Item *b)
	Returns true iff the two items are equal, as in a->eq(b), after unwrapping refs and Item_cache objects. More...
bool	AllItemsAreEqual (const Item *const *a, const Item *const *b, int num_items)
	Returns true iff all items in the two arrays (which must be of the same size) are equal, as in a->eq(b), after unwrapping refs and Item_cache objects. More...

Variables
constexpr float	COND_FILTER_ALLPASS {1.0f}
	Default condition filtering (selectivity) values used by get_filtering_effect() and friends when better estimates (statistics) are not available for a predicate. More...
constexpr float	COND_FILTER_EQUALITY {0.1f}
	Filtering effect for equalities: col1 = col2. More...
constexpr float	COND_FILTER_INEQUALITY {0.3333f}
	Filtering effect for inequalities: col1 > col2. More...
constexpr float	COND_FILTER_BETWEEN {0.1111f}
	Filtering effect for between: col1 BETWEEN a AND b. More...
constexpr float	COND_FILTER_STALE {-1.0f}
	Value is out-of-date, will need recalculation. More...
constexpr float	COND_FILTER_STALE_NO_CONST {-2.0f}
	A special subcase of the above: More...
const Name_string	null_name_string
const String	my_null_string

Macro Definition Documentation

ITEM_TO_QUERY_SUBSTRING_CHAR_LIMIT

#define ITEM_TO_QUERY_SUBSTRING_CHAR_LIMIT   (300)

Max length of an Item string for its use in an error message.

This should be kept in sync with MYSQL_ERRMSG_SIZE (which should not be exceeded).

MY_COLL_ALLOW_COERCIBLE_CONV

#define MY_COLL_ALLOW_COERCIBLE_CONV   2

MY_COLL_ALLOW_NONE

#define MY_COLL_ALLOW_NONE   4

MY_COLL_ALLOW_NUMERIC_CONV

#define MY_COLL_ALLOW_NUMERIC_CONV   8

MY_COLL_ALLOW_SUPERSET_CONV

#define MY_COLL_ALLOW_SUPERSET_CONV   1

MY_COLL_CMP_CONV

#define MY_COLL_CMP_CONV    (MY_COLL_ALLOW_SUPERSET_CONV | MY_COLL_ALLOW_COERCIBLE_CONV)

NAME_STRING

#define NAME_STRING

(

x

)

Name_string(STRING_WITH_LEN(x))

Typedef Documentation

Cond_traverser

typedef void(* Cond_traverser) (const Item *item, void *arg)

enum_monotonicity_info

typedef enum monotonicity_info enum_monotonicity_info

Item_analyzer

typedef bool(Item::* Item_analyzer) (uchar **argp)

Item_transformer

typedef Item *(Item::* Item_transformer) (uchar *arg)

Type for transformers used by Item::transform and Item::compile.

Parameters

arg	Argument used by the transformer. Really a typeless pointer in spite of the uchar type (historical reasons). The transformer needs to cast this to the desired pointer type

Returns

The transformed item

Ref_item_array

typedef Bounds_checked_array<Item *> Ref_item_array

Enumeration Type Documentation

monotonicity_info

enum monotonicity_info

Enumerator
NON_MONOTONIC
MONOTONIC_INCREASING
MONOTONIC_INCREASING_NOT_NULL
MONOTONIC_STRICT_INCREASING
MONOTONIC_STRICT_INCREASING_NOT_NULL

Function Documentation

agg_item_charsets()

bool agg_item_charsets	(	DTCollation &	c,
		const char *	name,
		Item **	items,
		uint	nitems,
		uint	flags
	)

agg_item_charsets_for_comparison()

bool agg_item_charsets_for_comparison ( DTCollation &  c, const char *  name, Item **  items, uint  nitems  )

inline

agg_item_charsets_for_string_result()

bool agg_item_charsets_for_string_result ( DTCollation &  c, const char *  name, Item **  items, uint  nitems  )

inline

agg_item_collations_for_comparison()

bool agg_item_collations_for_comparison	(	DTCollation &	c,
		const char *	fname,
		Item **	av,
		uint	count
	)

Aggregate collations for items used in a comparison operations.

For argument descriptions, see agg_item_collations().

AllItemsAreEqual()

bool AllItemsAreEqual	(	const Item *const *	a,
		const Item *const *	b,
		int	num_items
	)

Returns true iff all items in the two arrays (which must be of the same size) are equal, as in a->eq(b), after unwrapping refs and Item_cache objects.

char_to_byte_length_safe()

static uint32 char_to_byte_length_safe ( uint32  char_length_arg, uint32  mbmaxlen_arg  )

inlinestatic

CompileItem()

template<class T , class U >

Item * CompileItem ( Item *  item, T &&  analyzer, U &&  transformer  )

inline

Same as WalkItem, but for Item::compile().

Use as e.g.:

Item *item = CompileItem(root_item, [](Item *item) { return true; }, // Analyzer. [](Item *item) { return item; }); // Transformer.

convert_and_print()

void convert_and_print	(	const String *	from_str,
		String *	to_str,
		const CHARSET_INFO *	to_cs
	)

Helper method: Convert string to the given charset, then print.

Parameters

from_str	String to be converted.
to_str	Query string.
to_cs	Character set to which the string is to be converted.

convert_const_strings()

bool convert_const_strings	(	DTCollation &	coll,
		Item **	args,
		uint	nargs
	)

Convert constant strings according to a specific character set/collation.

For a set of items representing string values, convert those that are constant into the desired character set and collation unless they are already on correct form. Function may report error if string cannot be converted, e.g. due to non-overlapping character repertoires.

Parameters

	coll	The desired collation
[in,out]	args	The set of items that may be converted
	nargs	Number of items

Returns

false if successful, true if error

CountHiddenFields()

size_t CountHiddenFields ( const mem_root_deque< Item * > &  fields )

inline

CountVisibleFields()

size_t CountVisibleFields ( const mem_root_deque< Item * > &  fields )

inline

double_from_string_with_check()

double double_from_string_with_check	(	const CHARSET_INFO *	cs,
		const char *	cptr,
		const char *	end
	)

FindEqualField()

Item_field * FindEqualField	(	Item_field *	item_field,
		table_map	reachable_tables,
		bool	replace,
		bool *	found
	)

GetNthVisibleField()

Item * GetNthVisibleField ( const mem_root_deque< Item * > &  fields, size_t  index  )

inline

is_null_on_empty_table()

bool is_null_on_empty_table	(	THD *	thd,
		Item_field *	i
	)

Check if the column reference that is currently being resolved, will be set to NULL if its qualifying query returns zero rows.

This is true for non-aggregated column references in the SELECT list, if the query block uses aggregation without grouping. For example:

SELECT COUNT(*), col FROM t WHERE some_condition

Here, if the table t is empty, or some_condition doesn't match any rows in t, the query returns one row where col is NULL, even if col is a not-nullable column.

Such column references are rejected if the ONLY_FULL_GROUP_BY SQL mode is enabled, in a later resolution phase.

item_cmp_type()

Item_result item_cmp_type	(	Item_result	a,
		Item_result	b
	)

item_init()

void item_init

(

void

)

Init all special items.

ItemsAreEqual()

bool ItemsAreEqual	(	const Item *	a,
		const Item *	b
	)

Returns true iff the two items are equal, as in a->eq(b), after unwrapping refs and Item_cache objects.

ItemToQuerySubstr()

std::string ItemToQuerySubstr	(	const Item *	item,
		const LEX *	lex = nullptr,
		uint32	char_limit = ITEM_TO_QUERY_SUBSTRING_CHAR_LIMIT
	)

ItemToQuerySubstrNoCharLimit()

std::string ItemToQuerySubstrNoCharLimit

(

const Item *

item

)

ItemToString() [1/2]

std::string ItemToString

(

const Item *

item

)

ItemToString() [2/2]

std::string ItemToString	(	const Item *	item,
		enum_query_type	q_type
	)

longlong_from_string_with_check()

longlong longlong_from_string_with_check	(	const CHARSET_INFO *	cs,
		const char *	cptr,
		const char *	end,
		int	unsigned_target
	)

Converts a string to a longlong integer, with warnings.

Parameters

cs	charset of string
cptr	beginning of string
end	end of string
unsigned_target	If 0, caller will use result as a signed integer; if 1: an unsigned integer; if -1: caller doesn't tell. This influences warnings.

new_Cached_item()

Cached_item * new_Cached_item	(	THD *	thd,
		Item *	item
	)

Create right type of Cached_item for an item.

NO_FIELD_INDEX()

constexpr uint16 NO_FIELD_INDEX ( (uint16)(-1)  )

inlineconstexpr

numeric_context_result_type()

Item_result numeric_context_result_type ( enum_field_types  data_type, Item_result  result_type, uint8  decimals  )

inline

resolve_const_item()

bool resolve_const_item	(	THD *	thd,
		Item **	ref,
		Item *	comp_item
	)

Substitute a const item with a simpler const item, if possible.

Parameters

	thd	Current session.
[in,out]	ref	Const item to be processed, contains simplest possible item on return.
	comp_item	Item that provides result type for generated const item

Returns

false if success, true if error

SafeIncrement()

template<typename T >

void SafeIncrement

(

T *

num

)

Increment *num if it is less than its maximal value.

stored_field_cmp_to_item()

int stored_field_cmp_to_item	(	THD *	thd,
		Field *	field,
		Item *	item
	)

Compare the value stored in field with the expression from the query.

Parameters

thd	Current session.
field	Field which the Item is stored in after conversion
item	Original expression from query

Returns

Returns an integer greater than, equal to, or less than 0 if the value stored in the field is greater than, equal to, or less than the original Item. A 0 may also be returned if out of memory.

Note

We use this in the range optimizer/partition pruning, because in some cases we can't store the value in the field without some precision/character loss.

We similarly use it to verify that expressions like BIGINT_FIELD <cmp> <literal value> is done correctly (as int/decimal/float according to literal type).

TransformItem()

template<class T >

Item * TransformItem	(	Item *	item,
		T &&	transformer
	)

Same as WalkItem, but for Item::transform().

Use as e.g.:

Item *item = TransformItem(root_item, [](Item *item) { return item; });

WalkItem() [1/2]

template<class T >

bool WalkItem ( const Item *  item, enum_walk  walk, T &&  functor  )

inline

Overload for const 'item' and functor taking 'const Item*' argument.

WalkItem() [2/2]

template<class T >

bool WalkItem ( Item *  item, enum_walk  walk, T &&  functor  )

inline

A helper class to give in a functor to Item::walk().

Use as e.g.:

bool result = WalkItem(root_item, enum_walk::POSTFIX, [](Item *item) { ... });

TODO: Make Item::walk() just take in a functor in the first place, instead of a pointer-to-member and an opaque argument.

Variable Documentation

COND_FILTER_ALLPASS

constexpr float COND_FILTER_ALLPASS {1.0f}

constexpr

Default condition filtering (selectivity) values used by get_filtering_effect() and friends when better estimates (statistics) are not available for a predicate.

For predicates that are always satisfied. Must be 1.0 or the filter calculation logic will break down.

COND_FILTER_BETWEEN

constexpr float COND_FILTER_BETWEEN {0.1111f}

constexpr

Filtering effect for between: col1 BETWEEN a AND b.

COND_FILTER_EQUALITY

constexpr float COND_FILTER_EQUALITY {0.1f}

constexpr

Filtering effect for equalities: col1 = col2.

COND_FILTER_INEQUALITY

constexpr float COND_FILTER_INEQUALITY {0.3333f}

constexpr

Filtering effect for inequalities: col1 > col2.

COND_FILTER_STALE

constexpr float COND_FILTER_STALE {-1.0f}

constexpr

Value is out-of-date, will need recalculation.

This is used by post-greedy-search logic which changes the access method and thus makes obsolete the filtering value calculated by best_access_path(). For example, test_if_skip_sort_order().

COND_FILTER_STALE_NO_CONST

constexpr float COND_FILTER_STALE_NO_CONST {-2.0f}

constexpr

A special subcase of the above:

• if this is table/index/range scan, and
• rows_fetched is how many rows we will examine, and
• rows_fetched is less than the number of rows in the table (as determined by test_if_cheaper_ordering() and test_if_skip_sort_order()). Unlike the ordinary case where rows_fetched:
• is set by calculate_scan_cost(), and
• is how many rows pass the constant condition (so, less than we will examine), and
• the actual rows_fetched to show in EXPLAIN is the number of rows in the table (== rows which we will examine), and
• the constant condition's effect has to be moved to filter_effect for EXPLAIN.

my_null_string

const String my_null_string

extern

null_name_string

const Name_string null_name_string

extern