item_cmpfunc.cc File Reference

This file defines all Items that compare values (e.g. More...

#include "sql/item_cmpfunc.h"
#include <algorithm>
#include <array>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdint>
#include <cstring>
#include <type_traits>
#include <utility>
#include "decimal.h"
#include "m_ctype.h"
#include "m_string.h"
#include "mf_wcomp.h"
#include "my_alloc.h"
#include "my_bit.h"
#include "my_bitmap.h"
#include "my_dbug.h"
#include "my_sqlcommand.h"
#include "my_sys.h"
#include "mysql/udf_registration_types.h"
#include "mysql_com.h"
#include "mysql_time.h"
#include "mysqld_error.h"
#include "sql-common/json_dom.h"
#include "sql/aggregate_check.h"
#include "sql/check_stack.h"
#include "sql/current_thd.h"
#include "sql/derror.h"
#include "sql/error_handler.h"
#include "sql/field.h"
#include "sql/histograms/histogram.h"
#include "sql/item_func.h"
#include "sql/item_json_func.h"
#include "sql/item_subselect.h"
#include "sql/item_sum.h"
#include "sql/item_timefunc.h"
#include "sql/join_optimizer/bit_utils.h"
#include "sql/key.h"
#include "sql/mysqld.h"
#include "sql/nested_join.h"
#include "sql/opt_trace.h"
#include "sql/opt_trace_context.h"
#include "sql/parse_tree_helpers.h"
#include "sql/parse_tree_node_base.h"
#include "sql/query_options.h"
#include "sql/sql_array.h"
#include "sql/sql_base.h"
#include "sql/sql_bitmap.h"
#include "sql/sql_class.h"
#include "sql/sql_const.h"
#include "sql/sql_error.h"
#include "sql/sql_executor.h"
#include "sql/sql_lex.h"
#include "sql/sql_opt_exec_shared.h"
#include "sql/sql_optimizer.h"
#include "sql/sql_select.h"
#include "sql/sql_time.h"
#include "sql/system_variables.h"
#include "sql/thd_raii.h"

Classes
class	Cmp_longlong
class	Cmp_row
class	anonymous_namespace{item_cmpfunc.cc}::Cmp_string

Namespaces
namespace	anonymous_namespace{item_cmpfunc.cc}

Macros
#define	OLD_CMP

Functions
static bool	convert_constant_item (THD *thd, Item_field *field_item, Item **item, bool *converted)
	Convert a constant item to an int and replace the original item. More...
static longlong	get_year_value (THD *thd, Item ***item_arg, Item **cache_arg, const Item *warn_item, bool *is_null)
static Item **	cache_converted_constant (THD *thd, Item **value, Item **cache_item, Item_result type)
	Convert and cache a constant. More...
static bool	row_types_are_compatible (Item *item1, Item *item2)
	Compare row signature of two expressions. More...
static Item_result	agg_cmp_type (Item **items, uint nitems)
	Aggregates result types from the array of items. More...
static void	write_histogram_to_trace (THD *thd, Item_func *item, const double selectivity)
enum_field_types	agg_field_type (Item **items, uint nitems)
	Aggregates field types from the array of items. More...
static uint	collect_cmp_types (Item **items, uint nitems, bool skip_nulls=false)
	Collects different types for comparison of first item with each other items. More...
static void	my_coll_agg_error (DTCollation &c1, DTCollation &c2, const char *fname)
static bool	get_histogram_selectivity (THD *thd, const Field *field, Item **args, size_t arg_count, histograms::enum_operator op, Item_func *item_func, const TABLE_SHARE *table_share, double *selectivity)
static Item *	make_year_constant (Field *field)
	Return an an unsigned Item_int containing the value of the year as stored in field. More...
bool	get_mysql_time_from_str_no_warn (THD *thd, String *str, MYSQL_TIME *l_time, MYSQL_TIME_STATUS *status)
	A minion of get_mysql_time_from_str, see its description. More...
bool	get_mysql_time_from_str (THD *thd, String *str, enum_mysql_timestamp_type warn_type, const char *warn_name, MYSQL_TIME *l_time)
	Parse date provided in a string to a MYSQL_TIME. More...
static ulonglong	get_date_from_str (THD *thd, String *str, enum_mysql_timestamp_type warn_type, const char *warn_name, bool *error_arg)
	Convert date provided in a string to its packed temporal int representation. More...
static longlong	get_time_value (THD *, Item ***item_arg, Item **, const Item *, bool *is_null)
	Retrieves correct TIME value from the given item. More...
bool	wrap_in_cast (Item **item, enum_field_types type)
	Wraps the item into a CAST function to the type provided as argument. More...
bool	is_non_const_field_or_function (const Item &item)
	Checks that the argument is an aggregation function, window function, a built-in non-constant function or a non-constant field. More...
longlong	get_datetime_value (THD *thd, Item ***item_arg, Item **, const Item *warn_item, bool *is_null)
	Retrieve correct DATETIME value from given item. More...
static bool	get_json_arg (Item *arg, String *value, String *tmp, Json_wrapper *result, Json_scalar_holder **scalar)
	Get one of the arguments to the comparator as a JSON value. More...
static bool	compare_pair_for_nulls (Item *a, Item *b, bool *result)
	Compare two argument items, or a pair of elements from two argument rows, for NULL values. More...
template<typename LLorULL >
static longlong	compare_between_int_result (bool compare_as_temporal_dates, bool compare_as_temporal_times, bool negated, Item **args, bool *null_value)
	A helper function for Item_func_between::val_int() to avoid over/underflow when comparing large values. More...
static void	change_item_tree_if_needed (Item **place, Item *new_value)
	Check if (*place) and new_value points to different Items and call THD::change_item_tree() if needed. More...
static int	cmp_longs (longlong a_val, longlong b_val)
static int	cmp_ulongs (ulonglong a_val, ulonglong b_val)
static int	cmp_longlong (const in_longlong::packed_longlong *a, const in_longlong::packed_longlong *b)
static int	srtcmp_in (const CHARSET_INFO *cs, const String *x, const String *y)
static cmp_item_json *	make_cmp_item_json (MEM_ROOT *mem_root)
	Create a cmp_item_json object on a MEM_ROOT. More...
Item *	make_condition (Parse_context *pc, Item *item)
	Ensure that all expressions involved in conditions are boolean functions. More...
static bool	append_string_value (Item *comparand, const CHARSET_INFO *character_set, size_t max_char_length, bool pad_char_to_full_length, bool is_multi_column_key, String *join_key_buffer)
static bool	append_double_value (double value, bool is_null, String *join_key_buffer)
static bool	append_int_value (longlong value, bool is_null, bool unsigned_flag, String *join_key_buffer)
static bool	append_hash_for_string_value (Item *comparand, const CHARSET_INFO *character_set, String *join_key_buffer)
static bool	append_hash_for_json_value (Item *comparand, String *join_key_buffer)
static bool	append_decimal_value (Item *comparand, bool is_multi_column_key, String *join_key_buffer)
static bool	extract_value_for_hash_join (THD *thd, const HashJoinCondition &join_condition, const Arg_comparator *comparator, bool is_left_argument, bool is_multi_column_key, String *join_key_buffer)
	Extract the value from the item and append it to the output buffer "join_key_buffer" in a memcmp-able format. More...
void	find_and_adjust_equal_fields (Item *item, table_map available_tables, bool replace, bool *found)
static void	ensure_multi_equality_fields_are_available (Item **args, int arg_idx, table_map available_tables, bool replace, bool *found)

Variables
static const enum_walk	walk_options

Detailed Description

This file defines all Items that compare values (e.g.

>=, ==, LIKE, etc.)

Macro Definition Documentation

OLD_CMP

#define OLD_CMP

Function Documentation

agg_cmp_type()

static Item_result agg_cmp_type ( Item **  items, uint  nitems  )

static

Aggregates result types from the array of items.

This function aggregates result types from the array of items. Found type supposed to be used later for comparison of values of these items. Aggregation itself is performed by the item_cmp_type() function.

Parameters

items	array of items to aggregate the type from
nitems	number of items in the array

Returns

the aggregated type

agg_field_type()

enum_field_types agg_field_type	(	Item **	items,
		uint	nitems
	)

Aggregates field types from the array of items.

Parameters

[in]	items	array of items to aggregate the type from
[in]	nitems	number of items in the array

This function aggregates field types from the array of items. Found type is supposed to be used later as the result field type of a multi-argument function. Aggregation itself is performed by the Field::field_type_merge() function.

Note

The term "aggregation" is used here in the sense of inferring the result type of a function from its argument types.

Returns

aggregated field type.

append_decimal_value()

static bool append_decimal_value ( Item *  comparand, bool  is_multi_column_key, String *  join_key_buffer  )

static

append_double_value()

static bool append_double_value ( double  value, bool  is_null, String *  join_key_buffer  )

static

append_hash_for_json_value()

static bool append_hash_for_json_value ( Item *  comparand, String *  join_key_buffer  )

static

append_hash_for_string_value()

static bool append_hash_for_string_value ( Item *  comparand, const CHARSET_INFO *  character_set, String *  join_key_buffer  )

static

append_int_value()

static bool append_int_value ( longlong  value, bool  is_null, bool  unsigned_flag, String *  join_key_buffer  )

static

append_string_value()

static bool append_string_value ( Item *  comparand, const CHARSET_INFO *  character_set, size_t  max_char_length, bool  pad_char_to_full_length, bool  is_multi_column_key, String *  join_key_buffer  )

static

cache_converted_constant()

static Item ** cache_converted_constant ( THD *  thd, Item **  value, Item **  cache_item, Item_result  type  )

static

Convert and cache a constant.

Parameters

	thd	The current session.
	value	An item to cache
[out]	cache_item	Placeholder for the cache item
	type	Comparison type

When given item is a constant and its type differs from comparison type then cache its value to avoid type conversion of this constant on each evaluation. In this case the value is cached and the reference to the cache is returned. Original value is returned otherwise.

Returns

cache item or original value.

change_item_tree_if_needed()

static void change_item_tree_if_needed ( Item **  place, Item *  new_value  )

static

Check if (*place) and new_value points to different Items and call THD::change_item_tree() if needed.

This function is a workaround for implementation deficiency in Item_func_case. The problem there is that the 'args' attribute contains Items from different expressions.

The function must not be used elsewhere and will be remove eventually.

cmp_longlong()

static int cmp_longlong ( const in_longlong::packed_longlong *  a, const in_longlong::packed_longlong *  b  )

static

cmp_longs()

static int cmp_longs ( longlong  a_val, longlong  b_val  )

inlinestatic

cmp_ulongs()

static int cmp_ulongs ( ulonglong  a_val, ulonglong  b_val  )

inlinestatic

collect_cmp_types()

static uint collect_cmp_types ( Item **  items, uint  nitems, bool  skip_nulls = false  )

static

Collects different types for comparison of first item with each other items.

Parameters

items	Array of items to collect types from
nitems	Number of items in the array
skip_nulls	Don't collect types of NULL items if true

Note

This function collects different result types for comparison of the first item in the list with each of the remaining items in the 'items' array.

Return values

0	Error, row type incompatibility has been detected
<>	0 Bitmap of collected types - otherwise

compare_between_int_result()

template<typename LLorULL >

static longlong compare_between_int_result ( bool  compare_as_temporal_dates, bool  compare_as_temporal_times, bool  negated, Item **  args, bool *  null_value  )

inlinestatic

A helper function for Item_func_between::val_int() to avoid over/underflow when comparing large values.

Template Parameters

LLorULL

ulonglong or longlong

Parameters

	compare_as_temporal_dates	copy of Item_func_between member variable
	compare_as_temporal_times	copy of Item_func_between member variable
	negated	copy of Item_func_between member variable
	args	copy of Item_func_between member variable
[out]	null_value	set to true if result is not true/false

Return values

true	if: args[1] <= args[0] <= args[2]

compare_pair_for_nulls()

static bool compare_pair_for_nulls ( Item *  a, Item *  b, bool *  result  )

static

Compare two argument items, or a pair of elements from two argument rows, for NULL values.

Parameters

	a	First item
	b	Second item
[out]	result	True if both items are NULL, false otherwise, when return value is true.

Returns

true if at least one of the items is NULL

convert_constant_item()

static bool convert_constant_item ( THD *  thd, Item_field *  field_item, Item **  item, bool *  converted  )

static

Convert a constant item to an int and replace the original item.

The function converts a constant expression or string to an integer. On successful conversion the original item is substituted for the result of the item evaluation. This is done when comparing DATE/TIME of different formats and also when comparing bigint to strings (in which case strings are converted to bigints).

Parameters

	thd	thread handle
	field_item	item will be converted using the type of this field
[in,out]	item	reference to the item to convert
[out]	converted	True if a replacement was done.

Note

This function may be called both at prepare and optimize stages. When called at optimize stage, ensure that we record transient changes.

Returns

false if success, true if error

ensure_multi_equality_fields_are_available()

static void ensure_multi_equality_fields_are_available ( Item **  args, int  arg_idx, table_map  available_tables, bool  replace, bool *  found  )

static

extract_value_for_hash_join()

static bool extract_value_for_hash_join ( THD *  thd, const HashJoinCondition &  join_condition, const Arg_comparator *  comparator, bool  is_left_argument, bool  is_multi_column_key, String *  join_key_buffer  )

static

Extract the value from the item and append it to the output buffer "join_key_buffer" in a memcmp-able format.

The value extracted here will be used as the key in the hash table structure, where comparisons between keys are based on memcmp. Thus, it is important that the values extracted are memcmp-able, so for string values, we are basically creating a sort key. Other types (DECIMAL and FLOAT(M,N) and DOUBLE(M, N)) may be wrapped in a typecast in order to get a memcmp-able format from both sides of the condition. See Item_eq_base::create_cast_if_needed for more details.

Parameters

	thd	the thread handler
	join_condition	The hash join condition from which to get the value to write into the buffer.
	comparator	the comparator set up by Item_cmpfunc. This gives us the context in which the comparison is done. It is also needed for extracting the value in case of DATE/TIME/DATETIME/YEAR values in some cases
	is_left_argument	whether or not the provided item is the left argument of the condition. This is needed in case the comparator has set up a custom function for extracting the value from the item, as there are two separate functions for each side of the condition
	is_multi_column_key	true if the hash join key has multiple columns (that is, the hash join condition is a conjunction)
[out]	join_key_buffer	the output buffer where the extracted value is appended

Returns

true if a SQL NULL value was found

find_and_adjust_equal_fields()

void find_and_adjust_equal_fields	(	Item *	item,
		table_map	available_tables,
		bool	replace,
		bool *	found
	)

get_date_from_str()

static ulonglong get_date_from_str ( THD *  thd, String *  str, enum_mysql_timestamp_type  warn_type, const char *  warn_name, bool *  error_arg  )

static

Convert date provided in a string to its packed temporal int representation.

Parameters

[in]	thd	thread handle
[in]	str	a string to convert
[in]	warn_type	type of the timestamp for issuing the warning
[in]	warn_name	field name for issuing the warning
[out]	error_arg	could not extract a DATE or DATETIME

Convert date provided in the string str to the int representation. If the string contains wrong date or doesn't contain it at all then a warning is issued. The warn_type and the warn_name arguments are used as the name and the type of the field when issuing the warning.

Returns

converted value. 0 on error and on zero-dates – check 'failure'

get_datetime_value()

longlong get_datetime_value	(	THD *	thd,
		Item ***	item_arg,
		Item **	,
		const Item *	warn_item,
		bool *	is_null
	)

Retrieve correct DATETIME value from given item.

Parameters

	thd	thread handle
	item_arg	item to retrieve DATETIME value from
	warn_item	item for issuing the conversion warning
[out]	is_null	true <=> the item_arg is null

Retrieves the correct DATETIME value from given item for comparison by the compare_datetime() function. If item's result can be compared as longlong then its int value is used and its string value is used otherwise. Strings are always parsed and converted to int values by the get_date_from_str() function. This allows us to compare correctly string dates with missed insignificant zeros. In order to compare correctly DATE and DATETIME items the result of the former are treated as a DATETIME with zero time (00:00:00).

Returns

the DATETIME value, all ones if Item is NULL

get_histogram_selectivity()

static bool get_histogram_selectivity ( THD *  thd, const Field *  field, Item **  args, size_t  arg_count, histograms::enum_operator  op, Item_func *  item_func, const TABLE_SHARE *  table_share, double *  selectivity  )

static

get_json_arg()

static bool get_json_arg ( Item *  arg, String *  value, String *  tmp, Json_wrapper *  result, Json_scalar_holder **  scalar  )

static

Get one of the arguments to the comparator as a JSON value.

Parameters

[in]	arg	pointer to the argument
[in,out]	value	buffer used for reading the JSON value
[in,out]	tmp	buffer used for converting string values to the correct charset, if necessary
[out]	result	where to store the result
[in,out]	scalar	pointer to a location with pre-allocated memory used for JSON scalars that are converted from SQL scalars

Return values

false	on success
true	on failure

get_mysql_time_from_str()

bool get_mysql_time_from_str	(	THD *	thd,
		String *	str,
		enum_mysql_timestamp_type	warn_type,
		const char *	warn_name,
		MYSQL_TIME *	l_time
	)

Parse date provided in a string to a MYSQL_TIME.

Parameters

[in]	thd	Thread handle
[in]	str	A string to convert
[in]	warn_type	Type of the timestamp for issuing the warning
[in]	warn_name	Field name for issuing the warning
[out]	l_time	The MYSQL_TIME objects is initialized.

Parses a date provided in the string str into a MYSQL_TIME object. If the string contains an incorrect date or doesn't correspond to a date at all then a warning is issued. The warn_type and the warn_name arguments are used as the name and the type of the field when issuing the warning. If any input was discarded (trailing or non-timestamp-y characters), return value will be true.

Returns

Status flag

Return values

false	Success.
True	Indicates failure.

get_mysql_time_from_str_no_warn()

bool get_mysql_time_from_str_no_warn	(	THD *	thd,
		String *	str,
		MYSQL_TIME *	l_time,
		MYSQL_TIME_STATUS *	status
	)

A minion of get_mysql_time_from_str, see its description.

This version doesn't issue any warnings, leaving that to its parent. This method has one extra argument which return warnings.

Parameters

[in]	thd	Thread handle
[in]	str	A string to convert
[out]	l_time	The MYSQL_TIME objects is initialized.
[in,out]	status	Any warnings given are returned here

Returns

true if error

get_time_value()

static longlong get_time_value ( THD *  , Item ***  item_arg, Item **  , const Item *  , bool *  is_null  )

static

Retrieves correct TIME value from the given item.

Parameters

[in,out]	item_arg	item to retrieve TIME value from
[out]	is_null	true <=> the item_arg is null

Returns

obtained value

Retrieves the correct TIME value from given item for comparison by the compare_datetime() function. If item's result can be compared as longlong then its int value is used and a value returned by get_time function is used otherwise.

get_year_value()

static longlong get_year_value ( THD *  thd, Item ***  item_arg, Item **  cache_arg, const Item *  warn_item, bool *  is_null  )

static

is_non_const_field_or_function()

bool is_non_const_field_or_function ( const Item &  item )

inline

Checks that the argument is an aggregation function, window function, a built-in non-constant function or a non-constant field.

WL#12108: it excludes stored procedures and functions, user defined functions and also does not update the content of expressions inside Value_generator since Optimize is not called after the expression is unpacked.

Parameters

item	to be checked

Returns

true for non-const field or functions, false otherwise

make_cmp_item_json()

static cmp_item_json * make_cmp_item_json ( MEM_ROOT *  mem_root )

static

Create a cmp_item_json object on a MEM_ROOT.

make_condition()

Item * make_condition	(	Parse_context *	pc,
		Item *	item
	)

Ensure that all expressions involved in conditions are boolean functions.

Specifically, change <non-bool-expr> to (0 <> <non-bool-expr>)

Parameters

pc	Parse context, including memroot for Item construction
item	Any expression, if not a boolean expression, convert it

Returns

= NULL Error <> NULL A boolean expression, possibly constructed as described above

Note

Due to the special conditions of a MATCH expression (it is both a function returning a floating point value and it may be used standalone in the WHERE clause), it is wrapped inside a special Item_func_match_predicate, instead of forming a non-equality.

make_year_constant()

static Item * make_year_constant ( Field *  field )

static

Return an an unsigned Item_int containing the value of the year as stored in field.

The item is typed as a YEAR.

Parameters

field

the field containign the year value

Returns

the year wrapped in an Item in as described above, or nullptr on error.

my_coll_agg_error()

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

static

row_types_are_compatible()

static bool row_types_are_compatible ( Item *  item1, Item *  item2  )

static

Compare row signature of two expressions.

Parameters

item1	first expression
item2	second expression

Returns

true if row types are compatible, false otherwise.

The function checks that two expressions have compatible row signatures i.e. that the number of columns they return are the same and that if they are both row expressions then each component from the first expression has a row signature compatible with the signature of the corresponding component of the second expression.

srtcmp_in()

static int srtcmp_in ( const CHARSET_INFO *  cs, const String *  x, const String *  y  )

static

wrap_in_cast()

bool wrap_in_cast ( Item **  item, enum_field_types  type  )

inline

Wraps the item into a CAST function to the type provided as argument.

Parameters

item	- the item to be wrapped
type	- the type to wrap the item to

Returns

true if error (OOM), false otherwise.

write_histogram_to_trace()

static void write_histogram_to_trace ( THD *  thd, Item_func *  item, const double  selectivity  )

static

Variable Documentation

walk_options

const enum_walk walk_options

static

Initial value:

=
    enum_walk::PREFIX | enum_walk::POSTFIX | enum_walk::SUBQUERY