item.cc File Reference

#include "sql/item.h"
#include "integer_digits.h"
#include "my_compiler.h"
#include "my_config.h"
#include <stdio.h>
#include <sys/time.h>
#include <stddef.h>
#include <algorithm>
#include <optional>
#include <utility>
#include "decimal.h"
#include "float.h"
#include "limits.h"
#include "my_alloc.h"
#include "my_dbug.h"
#include "my_inttypes.h"
#include "my_macros.h"
#include "myisampack.h"
#include "mysql.h"
#include "mysql_time.h"
#include "sql-common/json_dom.h"
#include "sql/aggregate_check.h"
#include "sql/auth/auth_acls.h"
#include "sql/auth/auth_common.h"
#include "sql/auth/sql_security_ctx.h"
#include "sql/current_thd.h"
#include "sql/derror.h"
#include "sql/error_handler.h"
#include "sql/gis/srid.h"
#include "sql/item_cmpfunc.h"
#include "sql/item_create.h"
#include "sql/item_func.h"
#include "sql/item_json_func.h"
#include "sql/item_row.h"
#include "sql/item_strfunc.h"
#include "sql/item_subselect.h"
#include "sql/item_sum.h"
#include "sql/key.h"
#include "sql/log_event.h"
#include "sql/mysqld.h"
#include "sql/protocol.h"
#include "sql/query_options.h"
#include "sql/select_lex_visitor.h"
#include "sql/sp.h"
#include "sql/sp_rcontext.h"
#include "sql/sql_base.h"
#include "sql/sql_bitmap.h"
#include "sql/sql_class.h"
#include "sql/sql_derived.h"
#include "sql/sql_error.h"
#include "sql/sql_executor.h"
#include "sql/sql_lex.h"
#include "sql/sql_list.h"
#include "sql/sql_show.h"
#include "sql/sql_time.h"
#include "sql/sql_view.h"
#include "sql/system_variables.h"
#include "sql/thd_raii.h"
#include "sql/tztime.h"
#include "template_utils.h"
#include "typelib.h"
#include "unsafe_string_append.h"

Classes
class	Item_aggregate_ref

Functions
static bool	select_alias_referencable (enum_parsing_context place)
	Alias from select list can be referenced only from ORDER BY (SQL Standard) or from HAVING, GROUP BY and a subquery in the select list (MySQL extension). More...
static enum_field_types	real_data_type (Item *item)
	Find real data type of item. More...
void	item_init (void)
	Init all special items. More...
static bool	left_is_superset (DTCollation *left, DTCollation *right)
static void	my_coll_agg_error (DTCollation &c1, DTCollation &c2, const char *fname)
static void	my_coll_agg_error (DTCollation &c1, DTCollation &c2, DTCollation &c3, const char *fname)
static void	my_coll_agg_error (Item **args, uint count, const char *fname, int item_sep)
static bool	agg_item_collations (DTCollation &c, const char *fname, Item **av, uint count, uint flags, int item_sep)
bool	agg_item_collations_for_comparison (DTCollation &c, const char *fname, Item **av, uint count, uint flags)
bool	agg_item_set_converter (DTCollation &coll, const char *fname, Item **args, uint nargs, uint, int item_sep, bool only_consts)
bool	agg_item_charsets (DTCollation &coll, const char *fname, Item **args, uint nargs, uint flags, int item_sep, bool only_consts)
static uint32	adjust_max_effective_column_length (Field *field_par, uint32 max_length)
	Calculate the max column length not taking into account the limitations over integer types. More...
double	double_from_string_with_check (const CHARSET_INFO *cs, const char *cptr, const char *end)
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...
static void	mark_as_dependent (THD *thd, Query_block *last, Query_block *current, Item_ident *resolved_item, Item_ident *mark_item)
	Mark item and Query_blocks as dependent if item was resolved in outer SELECT. More...
static Item **	find_field_in_group_list (Item *find_item, ORDER *group_list)
	Search a GROUP BY clause for a field with a certain name. More...
static bool	resolve_ref_in_select_and_group (THD *thd, Item_ident *ref, Query_block *select, Item ***found)
	Resolve a column reference in a query block. 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...
static void	convert_zerofill_number_to_string (Item **item, const Field_num *field)
	Convert a numeric value to a zero-filled string. More...
static type_conversion_status	field_conv_with_cache (Field *to, Field *from, Field **last_to, uint32_t *to_is_memcpyable)
	Copies/converts data from “from” to “to”, but is faster on repeated execution with the same “to” field, as it caches the fields_are_memcpyable() and pack_length() calls. More...
static type_conversion_status	save_int_value_in_field (Field *field, longlong nr, bool null_value, bool unsigned_flag)
	Store an int in a field. More...
static uint	nr_of_decimals (const char *str, const char *end)
uint	char_val (char X)
Item_result	item_cmp_type (Item_result a, Item_result b)
bool	resolve_const_item (THD *thd, Item **ref, Item *comp_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...
static const char *	whence (const Item_field *cached_field)
	Get the name of the cached field of an Item_cache_json instance. 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...
string	ItemToString (const Item *item)
Item_field *	FindEqualField (Item_field *item_field, table_map reachable_tables, bool replace, bool *found)
static const Item *	UnwrapArgForEq (const Item *item)
	Unwrap an Item argument so that Item::eq() can see the "real" item, and not just the wrapper. More...
bool	ItemsAreEqual (const Item *a, const Item *b, bool binary_cmp)
	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, bool binary_cmp)
	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
const String	my_null_string ("NULL", 4, default_charset_info)
const Name_string	null_name_string (nullptr, 0)

Function Documentation

adjust_max_effective_column_length()

static uint32 adjust_max_effective_column_length ( Field *  field_par, uint32  max_length  )

inlinestatic

Calculate the max column length not taking into account the limitations over integer types.

When storing data into fields the server currently just ignores the limits specified on integer types, e.g. 1234 can safely be stored in an int(2) and will not cause an error. Thus when creating temporary tables and doing transformations we must adjust the maximum field length to reflect this fact. We take the un-restricted maximum length and adjust it similarly to how the declared length is adjusted wrt unsignedness etc. TODO: this all needs to go when we disable storing 1234 in int(2).

Parameters

field_par	Original field the use to calculate the lengths
max_length	Item's calculated explicit max length

Returns

The adjusted max length

agg_item_charsets()

bool agg_item_charsets	(	DTCollation &	coll,
		const char *	fname,
		Item **	args,
		uint	nargs,
		uint	flags,
		int	item_sep,
		bool	only_consts
	)

agg_item_collations()

static bool agg_item_collations ( DTCollation &  c, const char *  fname, Item **  av, uint  count, uint  flags, int  item_sep  )

static

agg_item_collations_for_comparison()

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

agg_item_set_converter()

bool agg_item_set_converter	(	DTCollation &	coll,
		const char *	fname,
		Item **	args,
		uint	nargs,
		uint	flags,
		int	item_sep,
		bool	only_consts
	)

AllItemsAreEqual()

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

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_val()

uint char_val ( char  X )

inline

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_zerofill_number_to_string()

static void convert_zerofill_number_to_string ( Item **  item, const Field_num *  field  )

static

Convert a numeric value to a zero-filled string.

Parameters

[in,out]	item	the item to operate on
	field	The field that this value is equated to

This function converts a numeric value to a string. In this conversion the zero-fill flag of the field is taken into account. This is required so the resulting string value can be used instead of the field reference when propagating equalities.

double_from_string_with_check()

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

field_conv_with_cache()

static type_conversion_status field_conv_with_cache ( Field *  to, Field *  from, Field **  last_to, uint32_t *  to_is_memcpyable  )

inlinestatic

Copies/converts data from “from” to “to”, but is faster on repeated execution with the same “to” field, as it caches the fields_are_memcpyable() and pack_length() calls.

These are not terribly expensive in themselves, but it adds up to 5–10% in DBT-3 Q1 due to the repeated calls.

The “from” field must correspond to the same last_to / to_is_memcpyable pair as earlier calls, unless last_to is cleared to nullptr.

find_field_in_group_list()

static Item ** find_field_in_group_list ( Item *  find_item, ORDER *  group_list  )

static

Search a GROUP BY clause for a field with a certain name.

Search the GROUP BY list for a column named as find_item. When searching preference is given to columns that are qualified with the same table (and database) name as the one being searched for.

Parameters

find_item	the item being searched for
group_list	GROUP BY clause

Returns

• the found item on success
• NULL if find_item is not in group_list

FindEqualField()

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

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,
		bool	binary_cmp
	)

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

ItemToString()

string ItemToString

(

const Item *

item

)

left_is_superset()

static bool left_is_superset ( DTCollation *  left, DTCollation *  right  )

static

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.

mark_as_dependent()

static void mark_as_dependent ( THD *  thd, Query_block *  last, Query_block *  current, Item_ident *  resolved_item, Item_ident *  mark_item  )

static

Mark item and Query_blocks as dependent if item was resolved in outer SELECT.

Parameters

thd	Current session.
last	select from which current item depend
current	current select
resolved_item	item which was resolved in outer SELECT
mark_item	item which should be marked; resolved_item will be marked anyway.

my_coll_agg_error() [1/3]

static void my_coll_agg_error ( DTCollation &  c1, DTCollation &  c2, const char *  fname  )

static

my_coll_agg_error() [2/3]

static void my_coll_agg_error ( DTCollation &  c1, DTCollation &  c2, DTCollation &  c3, const char *  fname  )

static

my_coll_agg_error() [3/3]

static void my_coll_agg_error ( Item **  args, uint  count, const char *  fname, int  item_sep  )

static

nr_of_decimals()

static uint nr_of_decimals ( const char *  str, const char *  end  )

static

real_data_type()

static enum_field_types real_data_type ( Item *  item )

static

Find real data type of item.

Returns

data type which should be used to store item value

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

resolve_ref_in_select_and_group()

static bool resolve_ref_in_select_and_group ( THD *  thd, Item_ident *  ref, Query_block *  select, Item ***  found  )

static

Resolve a column reference in a query block.

Resolve a column reference (usually inside a HAVING clause) against the SELECT and GROUP BY clauses of the query described by 'select'. The name resolution algorithm searches both the SELECT and GROUP BY clauses, and in case of a name conflict prefers GROUP BY column names over SELECT names. If both clauses contain different fields with the same names, a warning is issued that name of 'ref' is ambiguous. We extend ANSI SQL in that when no GROUP BY column is found, then a HAVING name is resolved as a possibly derived SELECT column.

Parameters

	thd	current thread
	ref	column reference being resolved
	select	the select that ref is resolved against
[out]	found	pointer to the found item = nullptr: item was not found

Note

The resolution procedure is:

• Search for a column or derived column named col_ref_i [in table T_j] in the SELECT clause of Q.
• Search for a column named col_ref_i [in table T_j] in the GROUP BY clause of Q.
• If found different columns with the same name in GROUP BY and SELECT, issue a warning
• return the found GROUP BY column if any,
• else return the found SELECT column if any.

Returns

false if success, true if error In case of successful return, the value of "found" indicates whether the column was found or not.

save_int_value_in_field()

static type_conversion_status save_int_value_in_field ( Field *  field, longlong  nr, bool  null_value, bool  unsigned_flag  )

static

Store an int in a field.

Parameters

field	The field where the int value is to be stored
nr	The value to store in field
null_value	True if the value to store is NULL, false otherwise
unsigned_flag	Whether or not the int value is signed or unsigned

Return values

TYPE_OK	Storing of value went fine without warnings or errors
!TYPE_OK	Warning/error as indicated by type_conversion_status enum value

select_alias_referencable()

static bool select_alias_referencable ( enum_parsing_context  place )

inlinestatic

Alias from select list can be referenced only from ORDER BY (SQL Standard) or from HAVING, GROUP BY and a subquery in the select list (MySQL extension).

We don't allow it be referenced from the SELECT list, with one exception: it's accepted if nested in a subquery, which is inconsistent but necessary as our users have shown to rely on this workaround.

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).

UnwrapArgForEq()

static const Item * UnwrapArgForEq ( const Item *  item )

static

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

It unwraps Item_ref using real_item(), and also cache items and rollup group wrappers, since these may not have been added consistently to both sides compared by Item::eq().

whence()

static const char * whence ( const Item_field *  cached_field )

inlinestatic

Get the name of the cached field of an Item_cache_json instance.

Variable Documentation

my_null_string

const String my_null_string("NULL", 4, default_charset_info)	(	"NULL"	,
		4	,
		default_charset_info
	)

null_name_string

const Name_string null_name_string(nullptr, 0)	(	nullptr	,
		0
	)