MySQL 9.0.0
Source Code Documentation
item.h
Go to the documentation of this file.
1#ifndef ITEM_INCLUDED
2#define ITEM_INCLUDED
3
4/* Copyright (c) 2000, 2024, Oracle and/or its affiliates.
5
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License, version 2.0,
8 as published by the Free Software Foundation.
9
10 This program is designed to work with certain software (including
11 but not limited to OpenSSL) that is licensed under separate terms,
12 as designated in a particular file or component or in included license
13 documentation. The authors of MySQL hereby grant you an additional
14 permission to link the program and your derivative works with the
15 separately licensed software that they have either included with
16 the program or referenced in the documentation.
17
18 This program is distributed in the hope that it will be useful,
19 but WITHOUT ANY WARRANTY; without even the implied warranty of
20 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 GNU General Public License, version 2.0, for more details.
22
23 You should have received a copy of the GNU General Public License
24 along with this program; if not, write to the Free Software
25 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
26
27#include <sys/types.h>
28
29#include <cfloat>
30#include <climits>
31#include <cmath>
32#include <cstdio>
33#include <cstring>
34#include <memory>
35#include <new>
36#include <optional>
37#include <string>
38#include <type_traits>
39#include <vector>
40
41#include "decimal.h"
42#include "field_types.h" // enum_field_types
43#include "lex_string.h"
44#include "memory_debugging.h"
45#include "my_alloc.h"
46#include "my_bitmap.h"
47#include "my_compiler.h"
48#include "my_dbug.h"
49#include "my_double2ulonglong.h"
50#include "my_inttypes.h"
51#include "my_sys.h"
52#include "my_table_map.h"
53#include "my_time.h"
54#include "mysql/strings/dtoa.h"
58#include "mysql_com.h"
59#include "mysql_time.h"
60#include "mysqld_error.h"
61#include "nulls.h"
62#include "sql-common/my_decimal.h" // my_decimal
63#include "sql/auth/auth_acls.h" // Access_bitmask
64#include "sql/enum_query_type.h"
65#include "sql/field.h" // Derivation
66#include "sql/mem_root_array.h"
67#include "sql/parse_location.h" // POS
68#include "sql/parse_tree_node_base.h" // Parse_tree_node
69#include "sql/sql_array.h" // Bounds_checked_array
70#include "sql/sql_const.h"
71#include "sql/sql_list.h"
72#include "sql/table.h"
73#include "sql/table_trigger_field_support.h" // Table_trigger_field_support
74#include "sql/thr_malloc.h"
75#include "sql/trigger_def.h" // enum_trigger_variable_type
76#include "sql_string.h"
77#include "string_with_len.h"
78#include "template_utils.h"
79
80class Item;
81class Item_cache;
83class Item_field;
84class Item_func;
85class Item_multi_eq;
87class Item_sum;
88class Json_wrapper;
89class Protocol;
90class Query_block;
92class sp_head;
93class sp_rcontext;
94class THD;
95class user_var_entry;
96struct COND_EQUAL;
97struct TYPELIB;
98
100
101void item_init(void); /* Init item functions */
102
103/**
104 Default condition filtering (selectivity) values used by
105 get_filtering_effect() and friends when better estimates
106 (statistics) are not available for a predicate.
107*/
108/**
109 For predicates that are always satisfied. Must be 1.0 or the filter
110 calculation logic will break down.
111*/
112constexpr float COND_FILTER_ALLPASS{1.0f};
113/// Filtering effect for equalities: col1 = col2
114constexpr float COND_FILTER_EQUALITY{0.1f};
115/// Filtering effect for inequalities: col1 > col2
116constexpr float COND_FILTER_INEQUALITY{0.3333f};
117/// Filtering effect for between: col1 BETWEEN a AND b
118constexpr float COND_FILTER_BETWEEN{0.1111f};
119/**
120 Value is out-of-date, will need recalculation.
121 This is used by post-greedy-search logic which changes the access method and
122 thus makes obsolete the filtering value calculated by best_access_path(). For
123 example, test_if_skip_sort_order().
124*/
125constexpr float COND_FILTER_STALE{-1.0f};
126/**
127 A special subcase of the above:
128 - if this is table/index/range scan, and
129 - rows_fetched is how many rows we will examine, and
130 - rows_fetched is less than the number of rows in the table (as determined
131 by test_if_cheaper_ordering() and test_if_skip_sort_order()).
132 Unlike the ordinary case where rows_fetched:
133 - is set by calculate_scan_cost(), and
134 - is how many rows pass the constant condition (so, less than we will
135 examine), and
136 - the actual rows_fetched to show in EXPLAIN is the number of rows in the
137 table (== rows which we will examine), and
138 - the constant condition's effect has to be moved to filter_effect for
139 EXPLAIN.
140*/
141constexpr float COND_FILTER_STALE_NO_CONST{-2.0f};
142
143static inline uint32 char_to_byte_length_safe(uint32 char_length_arg,
144 uint32 mbmaxlen_arg) {
145 const ulonglong tmp = ((ulonglong)char_length_arg) * mbmaxlen_arg;
146 return (tmp > UINT_MAX32) ? (uint32)UINT_MAX32 : (uint32)tmp;
147}
148
150 Item_result result_type,
151 uint8 decimals) {
152 if (is_temporal_type(real_type_to_type(data_type)))
153 return decimals ? DECIMAL_RESULT : INT_RESULT;
154 if (result_type == STRING_RESULT) return REAL_RESULT;
155 return result_type;
156}
157
158/*
159 "Declared Type Collation"
160 A combination of collation and its derivation.
161
162 Flags for collation aggregation modes:
163 MY_COLL_ALLOW_SUPERSET_CONV - allow conversion to a superset
164 MY_COLL_ALLOW_COERCIBLE_CONV - allow conversion of a coercible value
165 (i.e. constant).
166 MY_COLL_ALLOW_CONV - allow any kind of conversion
167 (combination of the above two)
168 MY_COLL_ALLOW_NUMERIC_CONV - if all items were numbers, convert to
169 @@character_set_connection
170 MY_COLL_DISALLOW_NONE - don't allow return DERIVATION_NONE
171 (e.g. when aggregating for comparison)
172 MY_COLL_CMP_CONV - combination of MY_COLL_ALLOW_CONV
173 and MY_COLL_DISALLOW_NONE
174*/
175
176#define MY_COLL_ALLOW_SUPERSET_CONV 1
177#define MY_COLL_ALLOW_COERCIBLE_CONV 2
178#define MY_COLL_DISALLOW_NONE 4
179#define MY_COLL_ALLOW_NUMERIC_CONV 8
180
181#define MY_COLL_ALLOW_CONV \
182 (MY_COLL_ALLOW_SUPERSET_CONV | MY_COLL_ALLOW_COERCIBLE_CONV)
183#define MY_COLL_CMP_CONV (MY_COLL_ALLOW_CONV | MY_COLL_DISALLOW_NONE)
184
186 public:
190
194 }
199 }
200 DTCollation(const CHARSET_INFO *collation_arg, Derivation derivation_arg) {
201 collation = collation_arg;
202 derivation = derivation_arg;
203 set_repertoire_from_charset(collation_arg);
204 }
205 void set(const DTCollation &dt) {
206 collation = dt.collation;
209 }
210 void set(const CHARSET_INFO *collation_arg, Derivation derivation_arg) {
211 collation = collation_arg;
212 derivation = derivation_arg;
213 set_repertoire_from_charset(collation_arg);
214 }
215 void set(const CHARSET_INFO *collation_arg, Derivation derivation_arg,
216 uint repertoire_arg) {
217 collation = collation_arg;
218 derivation = derivation_arg;
219 repertoire = repertoire_arg;
220 }
221 void set_numeric() {
225 }
226 void set(const CHARSET_INFO *collation_arg) {
227 collation = collation_arg;
228 set_repertoire_from_charset(collation_arg);
229 }
230 void set(Derivation derivation_arg) { derivation = derivation_arg; }
231 void set_repertoire(uint repertoire_arg) { repertoire = repertoire_arg; }
232 bool aggregate(DTCollation &dt, uint flags = 0);
233 bool set(DTCollation &dt1, DTCollation &dt2, uint flags = 0) {
234 set(dt1);
235 return aggregate(dt2, flags);
236 }
237 const char *derivation_name() const {
238 switch (derivation) {
240 return "NUMERIC";
242 return "IGNORABLE";
244 return "COERCIBLE";
246 return "IMPLICIT";
248 return "SYSCONST";
250 return "EXPLICIT";
251 case DERIVATION_NONE:
252 return "NONE";
253 default:
254 return "UNKNOWN";
255 }
256 }
257};
258
259/**
260 Class used as argument to Item::walk() together with mark_field_in_map()
261*/
263 public:
266
267 /**
268 If == NULL, update map of any table.
269 If <> NULL, update map of only this table.
270 */
271 TABLE *const table;
272 /// How to mark the map.
274};
275
276/**
277 Class used as argument to Item::walk() together with used_tables_for_level()
278*/
280 public:
282
283 Query_block *const select; ///< Level for which data is accumulated
284 table_map used_tables; ///< Accumulated used tables data
285};
286
287/*************************************************************************/
288
289/**
290 Storage for name strings.
291 Enpowers Simple_cstring with allocation routines from the sql_strmake family.
292
293 This class must stay as small as possible as we often
294 pass it into functions using call-by-value evaluation.
295
296 Don't add new members or virtual methods into this class!
297*/
299 private:
300 void set_or_copy(const char *str, size_t length, bool is_null_terminated) {
301 if (is_null_terminated)
302 set(str, length);
303 else
304 copy(str, length);
305 }
306
307 public:
309 /*
310 Please do NOT add constructor Name_string(const char *str) !
311 It will involve hidden strlen() call, which can affect
312 performance negatively. Use Name_string(str, len) instead.
313 */
314 Name_string(const char *str, size_t length) : Simple_cstring(str, length) {}
317 Name_string(const char *str, size_t length, bool is_null_terminated)
318 : Simple_cstring() {
319 set_or_copy(str, length, is_null_terminated);
320 }
321 Name_string(const LEX_STRING str, bool is_null_terminated)
322 : Simple_cstring() {
323 set_or_copy(str.str, str.length, is_null_terminated);
324 }
325 /**
326 Allocate space using sql_strmake() or sql_strmake_with_convert().
327 */
328 void copy(const char *str, size_t length, const CHARSET_INFO *cs);
329 /**
330 Variants for copy(), for various argument combinations.
331 */
332 void copy(const char *str, size_t length) {
334 }
335 void copy(const char *str) {
336 copy(str, (str ? strlen(str) : 0), system_charset_info);
337 }
338 void copy(const LEX_STRING lex) { copy(lex.str, lex.length); }
339 void copy(const LEX_STRING *lex) { copy(lex->str, lex->length); }
340 void copy(const Name_string str) { copy(str.ptr(), str.length()); }
341 /**
342 Compare name to another name in C string, case insensitively.
343 */
344 bool eq(const char *str) const {
345 assert(str && ptr());
346 return my_strcasecmp(system_charset_info, ptr(), str) == 0;
347 }
348 bool eq_safe(const char *str) const { return is_set() && str && eq(str); }
349 /**
350 Compare name to another name in Name_string, case insensitively.
351 */
352 bool eq(const Name_string name) const { return eq(name.ptr()); }
353 bool eq_safe(const Name_string name) const {
354 return is_set() && name.is_set() && eq(name);
355 }
356};
357
358#define NAME_STRING(x) Name_string(STRING_WITH_LEN(x))
359
360/**
361 Max length of an Item string for its use in an error message.
362 This should be kept in sync with MYSQL_ERRMSG_SIZE (which should
363 not be exceeded).
364*/
365#define ITEM_TO_QUERY_SUBSTRING_CHAR_LIMIT (300)
366
367extern const Name_string null_name_string;
368
369/**
370 Storage for Item names.
371 Adds "autogenerated" flag and warning functionality to Name_string.
372*/
374 private:
375 bool m_is_autogenerated; /* indicates if name of this Item
376 was autogenerated or set by user */
377 public:
381 /**
382 Set m_is_autogenerated flag to the given value.
383 */
386 }
387 /**
388 Return the auto-generated flag.
389 */
390 bool is_autogenerated() const { return m_is_autogenerated; }
391 using Name_string::copy;
392 /**
393 Copy name together with autogenerated flag.
394 Produce a warning if name was cut.
395 */
396 void copy(const char *str_arg, size_t length_arg, const CHARSET_INFO *cs_arg,
397 bool is_autogenerated_arg);
398};
399
400/**
401 Instances of Name_resolution_context store the information necessary for
402 name resolution of Items and other context analysis of a query made in
403 fix_fields().
404
405 This structure is a part of Query_block, a pointer to this structure is
406 assigned when an item is created (which happens mostly during parsing
407 (sql_yacc.yy)), but the structure itself will be initialized after parsing
408 is complete
409
410 @todo move subquery of INSERT ... SELECT and CREATE ... SELECT to
411 separate Query_block which allow to remove tricks of changing this
412 structure before and after INSERT/CREATE and its SELECT to make correct
413 field name resolution.
414*/
416 /**
417 The name resolution context to search in when an Item cannot be
418 resolved in this context (the context of an outer select)
419 */
421 /// Link to next name res context with the same query block as the base
423
424 /**
425 List of tables used to resolve the items of this context. Usually these
426 are tables from the FROM clause of SELECT statement. The exceptions are
427 INSERT ... SELECT and CREATE ... SELECT statements, where SELECT
428 subquery is not moved to a separate Query_block. For these types of
429 statements we have to change this member dynamically to ensure correct
430 name resolution of different parts of the statement.
431 */
433 /**
434 In most cases the two table references below replace 'table_list' above
435 for the purpose of name resolution. The first and last name resolution
436 table references allow us to search only in a sub-tree of the nested
437 join tree in a FROM clause. This is needed for NATURAL JOIN, JOIN ... USING
438 and JOIN ... ON.
439 */
441 /**
442 Last table to search in the list of leaf table references that begins
443 with first_name_resolution_table.
444 */
446
447 /**
448 Query_block item belong to, in case of merged VIEW it can differ from
449 Query_block where item was created, so we can't use table_list/field_list
450 from there
451 */
453
454 /*
455 Processor of errors caused during Item name resolving, now used only to
456 hide underlying tables in errors about views (i.e. it substitute some
457 errors for views)
458 */
461
462 /**
463 When true, items are resolved in this context against
464 Query_block::item_list, SELECT_lex::group_list and
465 this->table_list. If false, items are resolved only against
466 this->table_list.
467
468 @see Query_block::item_list, Query_block::group_list
469 */
471
472 /**
473 Security context of this name resolution context. It's used for views
474 and is non-zero only if the view is defined with SQL SECURITY DEFINER.
475 */
477
481 }
482};
483
484/**
485 Struct used to pass around arguments to/from
486 check_function_as_value_generator
487*/
490 int default_error_code, Value_generator_source val_gen_src)
491 : err_code(default_error_code), source(val_gen_src) {}
492 /// the order of the column in table
493 int col_index{-1};
494 /// the error code found during check(if any)
496 /*
497 If it is a generated column, default expression or check constraint
498 expression value generator.
499 */
501 /// the name of the function which is not allowed
502 const char *banned_function_name{nullptr};
503
504 /// Return the correct error code, based on whether or not if we are checking
505 /// for disallowed functions in generated column expressions, in default
506 /// value expressions or in check constraint expression.
508 return ((source == VGS_GENERATED_COLUMN)
509 ? ER_GENERATED_COLUMN_FUNCTION_IS_NOT_ALLOWED
511 ? ER_DEFAULT_VAL_GENERATED_FUNCTION_IS_NOT_ALLOWED
512 : ER_CHECK_CONSTRAINT_FUNCTION_IS_NOT_ALLOWED);
513 }
514};
515/*
516 Store and restore the current state of a name resolution context.
517*/
518
520 private:
526
527 public:
528 /* Save the state of a name resolution context. */
529 void save_state(Name_resolution_context *context, Table_ref *table_list) {
530 save_table_list = context->table_list;
533 save_next_local = table_list->next_local;
535 }
536
537 /* Restore a name resolution context from saved state. */
538 void restore_state(Name_resolution_context *context, Table_ref *table_list) {
539 table_list->next_local = save_next_local;
541 context->table_list = save_table_list;
544 }
545
546 void update_next_local(Table_ref *table_list) {
547 save_next_local = table_list;
548 }
549
552 }
553};
554
555/*
556 This enum is used to report information about monotonicity of function
557 represented by Item* tree.
558 Monotonicity is defined only for Item* trees that represent table
559 partitioning expressions (i.e. have no subqueries/user vars/dynamic parameters
560 etc etc). An Item* tree is assumed to have the same monotonicity properties
561 as its corresponding function F:
562
563 [signed] longlong F(field1, field2, ...) {
564 put values of field_i into table record buffer;
565 return item->val_int();
566 }
567
568 NOTE
569 At the moment function monotonicity is not well defined (and so may be
570 incorrect) for Item trees with parameters/return types that are different
571 from INT_RESULT, may be NULL, or are unsigned.
572 It will be possible to address this issue once the related partitioning bugs
573 (BUG#16002, BUG#15447, BUG#13436) are fixed.
574
575 The NOT_NULL enums are used in TO_DAYS, since TO_DAYS('2001-00-00') returns
576 NULL which puts those rows into the NULL partition, but
577 '2000-12-31' < '2001-00-00' < '2001-01-01'. So special handling is needed
578 for this (see Bug#20577).
579*/
580
581typedef enum monotonicity_info {
582 NON_MONOTONIC, /* none of the below holds */
583 MONOTONIC_INCREASING, /* F() is unary and (x < y) => (F(x) <= F(y)) */
584 MONOTONIC_INCREASING_NOT_NULL, /* But only for valid/real x and y */
585 MONOTONIC_STRICT_INCREASING, /* F() is unary and (x < y) => (F(x) < F(y)) */
586 MONOTONIC_STRICT_INCREASING_NOT_NULL /* But only for valid/real x and y */
588
589/**
590 A type for SQL-like 3-valued Booleans: true/false/unknown.
591*/
592class Bool3 {
593 public:
594 /// @returns an instance set to "FALSE"
595 static const Bool3 false3() { return Bool3(v_FALSE); }
596 /// @returns an instance set to "UNKNOWN"
597 static const Bool3 unknown3() { return Bool3(v_UNKNOWN); }
598 /// @returns an instance set to "TRUE"
599 static const Bool3 true3() { return Bool3(v_TRUE); }
600
601 bool is_true() const { return m_val == v_TRUE; }
602 bool is_unknown() const { return m_val == v_UNKNOWN; }
603 bool is_false() const { return m_val == v_FALSE; }
604
605 private:
607 /// This is private; instead, use false3()/etc.
608 Bool3(value v) : m_val(v) {}
609
611 /*
612 No operator to convert Bool3 to bool (or int) - intentionally: how
613 would you map unknown3 to true/false?
614 It is because we want to block such conversions that Bool3 is a class
615 instead of a plain enum.
616 */
617};
618
619/**
620 Type properties, used to collect type information for later assignment
621 to an Item object. The object stores attributes signedness, max length
622 and collation. However, precision and scale (for decimal numbers) and
623 fractional second precision (for time and datetime) are not stored,
624 since any type derived from this object will have default values for these
625 attributes.
626*/
628 public:
629 /// Constructor for any signed numeric type or date type
630 /// Defaults are provided for attributes like signedness and max length
632 : m_type(type_arg),
633 m_unsigned_flag(false),
634 m_max_length(0),
636 assert(type_arg != MYSQL_TYPE_VARCHAR && type_arg != MYSQL_TYPE_JSON);
637 }
638 /// Constructor for any numeric type, with explicit signedness
639 Type_properties(enum_field_types type_arg, bool unsigned_arg)
640 : m_type(type_arg),
641 m_unsigned_flag(unsigned_arg),
642 m_max_length(0),
644 assert(is_numeric_type(type_arg) || type_arg == MYSQL_TYPE_BIT ||
645 type_arg == MYSQL_TYPE_YEAR);
646 }
647 /// Constructor for character type, with explicit character set.
648 /// Default length/max length is provided.
650 : m_type(type_arg),
651 m_unsigned_flag(false),
652 m_max_length(0),
654 /// Constructor for Item
655 Type_properties(Item &item);
657 const bool m_unsigned_flag;
660};
661
662/*************************************************************************/
663
665 public:
667 virtual ~Settable_routine_parameter() = default;
668 /**
669 Set required privileges for accessing the parameter.
670
671 @param privilege The required privileges for this field, with the
672 following alternatives:
673 MODE_IN - SELECT_ACL
674 MODE_OUT - UPDATE_ACL
675 MODE_INOUT - SELECT_ACL | UPDATE_ACL
676 */
678 [[maybe_unused]]) {}
679
680 /*
681 Set parameter value.
682
683 SYNOPSIS
684 set_value()
685 thd thread handle
686 ctx context to which parameter belongs (if it is local
687 variable).
688 it item which represents new value
689
690 RETURN
691 false if parameter value has been set,
692 true if error has occurred.
693 */
694 virtual bool set_value(THD *thd, sp_rcontext *ctx, Item **it) = 0;
695
696 virtual void set_out_param_info(Send_field *info [[maybe_unused]]) {}
697
698 virtual const Send_field *get_out_param_info() const { return nullptr; }
699};
700
701/*
702 Analyzer function
703 SYNOPSIS
704 argp in/out IN: Analysis parameter
705 OUT: Parameter to be passed to the transformer
706
707 RETURN
708 true Invoke the transformer
709 false Don't do it
710
711*/
712typedef bool (Item::*Item_analyzer)(uchar **argp);
713
714/**
715 Type for transformers used by Item::transform and Item::compile
716 @param arg Argument used by the transformer. Really a typeless pointer
717 in spite of the uchar type (historical reasons). The
718 transformer needs to cast this to the desired pointer type
719 @returns The transformed item
720*/
721typedef Item *(Item::*Item_transformer)(uchar *arg);
722typedef void (*Cond_traverser)(const Item *item, void *arg);
723
724/**
725 Utility mixin class to be able to walk() only parts of item trees.
726
727 Used with PREFIX+POSTFIX walk: in the prefix call of the Item
728 processor, we process the item X, may decide that its children should not
729 be processed (just like if they didn't exist): processor calls stop_at(X)
730 for that. Then walk() goes to a child Y; the processor tests is_stopped(Y)
731 which returns true, so processor sees that it must not do any processing
732 and returns immediately. Finally, the postfix call to the processor on X
733 tests is_stopped(X) which returns "true" and understands that the
734 not-to-be-processed children have been skipped so calls restart(). Thus,
735 any sibling of X, any part of the Item tree not under X, can then be
736 processed.
737*/
739 protected:
744
745 /// Stops walking children of this item
746 void stop_at(const Item *i) {
747 assert(stopped_at_item == nullptr);
748 stopped_at_item = i;
749 }
750
751 /**
752 @returns if we are stopped. If item 'i' is where we stopped, restarts the
753 walk for next items.
754 */
755 bool is_stopped(const Item *i) {
756 if (stopped_at_item != nullptr) {
757 /*
758 Walking was disabled for a tree part rooted a one ancestor of 'i' or
759 rooted at 'i'.
760 */
761 if (stopped_at_item == i) {
762 /*
763 Walking was disabled for the tree part rooted at 'i'; we have now just
764 returned back to this root (POSTFIX call), left the tree part:
765 enable the walk again, for other tree parts.
766 */
767 stopped_at_item = nullptr;
768 }
769 // No further processing to do for this item:
770 return true;
771 }
772 return false;
773 }
774
775 private:
776 const Item *stopped_at_item{nullptr};
777};
778
779/// Increment *num if it is less than its maximal value.
780template <typename T>
781void SafeIncrement(T *num) {
782 if (*num < std::numeric_limits<T>::max()) {
783 *num += 1;
784 }
785}
786
787/**
788 This class represents the cost of evaluating an Item. @see SortPredicates
789 to see how this is used.
790*/
791class CostOfItem final {
792 public:
793 /// Set '*this' to represent the cost of 'item'.
794 void Compute(const Item &item) {
795 if (!m_computed) {
796 ComputeInternal(item);
797 }
798 }
799
801 assert(!m_computed);
802 m_is_expensive = true;
803 }
804
805 /// Add the cost of accessing a Field_str.
807 assert(!m_computed);
809 }
810
811 /// Add the cost of accessing any other Field.
813 assert(!m_computed);
815 }
816
817 bool IsExpensive() const {
818 assert(m_computed);
819 return m_is_expensive;
820 }
821
822 /**
823 Get the cost of field access when evaluating the Item associated with this
824 object. The cost unit is arbitrary, but the relative cost of different
825 items reflect the fact that operating on Field_str is more expensive than
826 other Field subclasses.
827 */
828 double FieldCost() const {
829 assert(m_computed);
831 }
832
833 private:
834 /// The cost of accessing a Field_str, relative to other Field types.
835 /// (The value was determined using benchmarks.)
836 static constexpr double kStrFieldCost = 1.8;
837
838 /// The cost of accessing a Field other than Field_str. 1.0 by definition.
839 static constexpr double kOtherFieldCost = 1.0;
840
841 /// True if 'ComputeInternal()' has been called.
842 bool m_computed{false};
843
844 /// True if the associated Item calls user defined functions or stored
845 /// procedures.
846 bool m_is_expensive{false};
847
848 /// The number of Field_str objects accessed by the associated Item.
850
851 /// The number of other Field objects accessed by the associated Item.
853
854 /// Compute the cost of 'root' and its descendants.
855 void ComputeInternal(const Item &root);
856};
857
858/**
859 This class represents a subquery contained in some subclass of
860 Item_subselect, @see FindContainedSubqueries().
861*/
863 /// The strategy for executing the subquery.
864 enum class Strategy : char {
865 /**
866 An independent subquery that is materialized, e.g.:
867 "SELECT * FROM tab WHERE field IN <independent subquery>".
868 where 'independent subquery' does not depend on any fields in 'tab'.
869 (This corresponds to the Item_in_subselect class.)
870 */
872
873 /**
874 A subquery that is reevaluated for each row, e.g.:
875 "SELECT * FROM tab WHERE field IN <dependent subquery>" or
876 "SELECT * FROM tab WHERE field = <dependent subquery>".
877 where 'dependent subquery' depends on at least one field in 'tab'.
878 Alternatively, the subquery may be independent of 'tab', but contain
879 a non-deterministic function such as 'rand()'. Such subqueries are also
880 required to be reevaluated for each row.
881 */
883
884 /**
885 An independent single-row subquery that is evaluated once, e.g.:
886 "SELECT * FROM tab WHERE field = <independent single-row subquery>".
887 (This corresponds to the Item_singlerow_subselect class.)
888 */
890 };
891
892 /// The root path of the subquery.
894
895 /// The strategy for executing the subquery.
897
898 /// The width (in bytes) of the subquery's rows. For variable-sized values we
899 /// use Item.max_length (but cap it at kMaxItemLengthEstimate).
900 /// @see kMaxItemLengthEstimate and
901 /// @see Item_in_subselect::get_contained_subquery().
903};
904
905/**
906 Base class that is used to represent any kind of expression in a
907 relational query. The class provides subclasses for simple components, like
908 literal (constant) values, column references and variable references,
909 as well as more complex expressions like comparison predicates,
910 arithmetic and string functions, row objects, function references and
911 subqueries.
912
913 The lifetime of an Item class object is often the same as a relational
914 statement, which may be used for several executions, but in some cases
915 it may also be generated for an optimized statement and thus be valid
916 only for one execution.
917
918 For Item objects with longer lifespan than one execution, we must take
919 special precautions when referencing objects with shorter lifespan.
920 For example, TABLE and Field objects against most tables are valid only for
921 one execution. For such objects, Item classes should rather reference
922 Table_ref and Item_field objects instead of TABLE and Field, because
923 these classes support dynamic rebinding of objects before each execution.
924 See Item::bind_fields() which binds new objects per execution and
925 Item::cleanup() that deletes references to such objects.
926
927 These mechanisms can also be used to handle other objects with shorter
928 lifespan, such as function references and variable references.
929*/
930class Item : public Parse_tree_node {
932
933 friend class udf_handler;
934
935 protected:
936 /**
937 Sets the result value of the function an empty string, using the current
938 character set. No memory is allocated.
939 @retval A pointer to the str_value member.
940 */
943 return &str_value;
944 }
945
946 public:
947 Item(const Item &) = delete;
948 void operator=(Item &) = delete;
949 static void *operator new(size_t size) noexcept {
950 return (*THR_MALLOC)->Alloc(size);
951 }
952 static void *operator new(size_t size, MEM_ROOT *mem_root,
953 const std::nothrow_t &arg
954 [[maybe_unused]] = std::nothrow) noexcept {
955 return mem_root->Alloc(size);
956 }
957
958 static void operator delete(void *ptr [[maybe_unused]],
959 size_t size [[maybe_unused]]) {
960 TRASH(ptr, size);
961 }
962 static void operator delete(void *, MEM_ROOT *,
963 const std::nothrow_t &) noexcept {}
964
965 enum Type {
967 FIELD_ITEM, ///< A reference to a field (column) in a table.
968 FUNC_ITEM, ///< A function call reference.
969 SUM_FUNC_ITEM, ///< A grouped aggregate function, or window function.
970 AGGR_FIELD_ITEM, ///< A special field for certain aggregate operations.
971 STRING_ITEM, ///< A string literal value.
972 INT_ITEM, ///< An integer literal value.
973 DECIMAL_ITEM, ///< A decimal literal value.
974 REAL_ITEM, ///< A floating-point literal value.
975 NULL_ITEM, ///< A NULL value.
976 HEX_BIN_ITEM, ///< A hexadecimal or binary literal value.
977 DEFAULT_VALUE_ITEM, ///< A default value for a column.
978 COND_ITEM, ///< An AND or OR condition.
979 REF_ITEM, ///< An indirect reference to another item.
980 INSERT_VALUE_ITEM, ///< A value from a VALUES function (deprecated).
981 SUBQUERY_ITEM, ///< A subquery or predicate referencing a subquery.
982 ROW_ITEM, ///< A row of other items.
983 CACHE_ITEM, ///< An internal item used to cache values.
984 TYPE_HOLDER_ITEM, ///< An internal item used to help aggregate a type.
985 PARAM_ITEM, ///< A dynamic parameter used in a prepared statement.
986 ROUTINE_FIELD_ITEM, ///< A variable inside a routine (proc, func, trigger)
987 TRIGGER_FIELD_ITEM, ///< An OLD or NEW field, used in trigger definitions.
988 XPATH_NODESET_ITEM, ///< Used in XPATH expressions.
989 VALUES_COLUMN_ITEM, ///< A value from a VALUES clause.
990 NAME_CONST_ITEM ///< A NAME_CONST expression
991 };
992
994
996
997 /// How to cache constant JSON data
999 /// Don't cache
1001 /// Source data is a JSON string, parse and cache result
1003 /// Source data is SQL scalar, convert and cache result
1006
1007 enum Bool_test ///< Modifier for result transformation
1018 };
1019
1020 // Return the default data type for a given result type
1022 switch (result) {
1023 case INT_RESULT:
1024 return MYSQL_TYPE_LONGLONG;
1025 case DECIMAL_RESULT:
1026 return MYSQL_TYPE_NEWDECIMAL;
1027 case REAL_RESULT:
1028 return MYSQL_TYPE_DOUBLE;
1029 case STRING_RESULT:
1030 return MYSQL_TYPE_VARCHAR;
1031 case INVALID_RESULT:
1032 return MYSQL_TYPE_INVALID;
1033 case ROW_RESULT:
1034 default:
1035 assert(false);
1036 }
1037 return MYSQL_TYPE_INVALID;
1038 }
1039
1040 // Return the default result type for a given data type
1042 switch (type) {
1043 case MYSQL_TYPE_TINY:
1044 case MYSQL_TYPE_SHORT:
1045 case MYSQL_TYPE_INT24:
1046 case MYSQL_TYPE_LONG:
1048 case MYSQL_TYPE_BOOL:
1049 case MYSQL_TYPE_BIT:
1050 case MYSQL_TYPE_YEAR:
1051 return INT_RESULT;
1053 case MYSQL_TYPE_DECIMAL:
1054 return DECIMAL_RESULT;
1055 case MYSQL_TYPE_FLOAT:
1056 case MYSQL_TYPE_DOUBLE:
1057 return REAL_RESULT;
1058 case MYSQL_TYPE_VARCHAR:
1060 case MYSQL_TYPE_STRING:
1064 case MYSQL_TYPE_BLOB:
1065 case MYSQL_TYPE_VECTOR:
1067 case MYSQL_TYPE_JSON:
1068 case MYSQL_TYPE_ENUM:
1069 case MYSQL_TYPE_SET:
1070 return STRING_RESULT;
1072 case MYSQL_TYPE_DATE:
1073 case MYSQL_TYPE_TIME:
1075 case MYSQL_TYPE_NEWDATE:
1078 case MYSQL_TYPE_TIME2:
1079 return STRING_RESULT;
1080 case MYSQL_TYPE_INVALID:
1081 return INVALID_RESULT;
1082 case MYSQL_TYPE_NULL:
1083 return STRING_RESULT;
1085 break;
1086 }
1087 assert(false);
1088 return INVALID_RESULT;
1089 }
1090
1091 /**
1092 Provide data type for a user or system variable, based on the type of
1093 the item that is assigned to the variable.
1094
1095 @note MYSQL_TYPE_VARCHAR is returned for all string types, but must be
1096 further adjusted based on maximum string length by the caller.
1097
1098 @param src_type Source type that variable's type is derived from
1099 */
1101 switch (src_type) {
1102 case MYSQL_TYPE_BOOL:
1103 case MYSQL_TYPE_TINY:
1104 case MYSQL_TYPE_SHORT:
1105 case MYSQL_TYPE_INT24:
1106 case MYSQL_TYPE_LONG:
1108 case MYSQL_TYPE_BIT:
1109 return MYSQL_TYPE_LONGLONG;
1110 case MYSQL_TYPE_DECIMAL:
1112 return MYSQL_TYPE_NEWDECIMAL;
1113 case MYSQL_TYPE_FLOAT:
1114 case MYSQL_TYPE_DOUBLE:
1115 return MYSQL_TYPE_DOUBLE;
1116 case MYSQL_TYPE_VARCHAR:
1118 case MYSQL_TYPE_STRING:
1119 return MYSQL_TYPE_VARCHAR;
1120 case MYSQL_TYPE_YEAR:
1121 return MYSQL_TYPE_LONGLONG;
1123 case MYSQL_TYPE_DATE:
1124 case MYSQL_TYPE_TIME:
1126 case MYSQL_TYPE_NEWDATE:
1129 case MYSQL_TYPE_TIME2:
1130 case MYSQL_TYPE_JSON:
1131 case MYSQL_TYPE_ENUM:
1132 case MYSQL_TYPE_SET:
1134 case MYSQL_TYPE_NULL:
1136 case MYSQL_TYPE_BLOB:
1137 case MYSQL_TYPE_VECTOR:
1140 return MYSQL_TYPE_VARCHAR;
1141 case MYSQL_TYPE_INVALID:
1143 return MYSQL_TYPE_INVALID;
1144 }
1145 assert(false);
1146 return MYSQL_TYPE_NULL;
1147 }
1148
1149 /// Item constructor for general use.
1150 Item();
1151
1152 /**
1153 Constructor used by Item_field, Item_ref & aggregate functions.
1154 Used for duplicating lists in processing queries with temporary tables.
1155
1156 Also used for Item_cond_and/Item_cond_or for creating top AND/OR structure
1157 of WHERE clause to protect it of optimisation changes in prepared statements
1158 */
1159 Item(THD *thd, const Item *item);
1160
1161 /**
1162 Parse-time context-independent constructor.
1163
1164 This constructor and caller constructors of child classes must not
1165 access/change thd->lex (including thd->lex->current_query_block(),
1166 thd->m_parser_state etc structures).
1167
1168 If we need to finalize the construction of the object, then we move
1169 all context-sensitive code to the itemize() virtual function.
1170
1171 The POS parameter marks this constructor and other context-independent
1172 constructors of child classes for easy recognition/separation from other
1173 (context-dependent) constructors.
1174 */
1175 explicit Item(const POS &);
1176
1177#ifdef EXTRA_DEBUG
1178 ~Item() override { item_name.set(0); }
1179#else
1180 ~Item() override = default;
1181#endif
1182
1183 private:
1184 /*
1185 Hide the contextualize*() functions: call/override the itemize()
1186 in Item class tree instead.
1187 */
1189 assert(0);
1190 return true;
1191 }
1192
1193 protected:
1194 /**
1195 Helper function to skip itemize() for grammar-allocated items
1196
1197 @param [out] res pointer to "this"
1198
1199 @retval true can skip itemize()
1200 @retval false can't skip: the item is allocated directly by the parser
1201 */
1202 bool skip_itemize(Item **res) {
1203 *res = this;
1204 return !is_parser_item;
1205 }
1206
1207 /*
1208 Checks if the function should return binary result based on the items
1209 provided as parameter.
1210 Function should only be used by Item_bit_func*
1211
1212 @param a item to check
1213 @param b item to check, may be nullptr
1214
1215 @returns true if binary result.
1216 */
1217 static bool bit_func_returns_binary(const Item *a, const Item *b);
1218
1219 /**
1220 The core function that does the actual itemization. itemize() is just a
1221 wrapper over this.
1222 */
1223 virtual bool do_itemize(Parse_context *pc, Item **res);
1224
1225 public:
1226 /**
1227 The same as contextualize() but with additional parameter
1228
1229 This function finalize the construction of Item objects (see the Item(POS)
1230 constructor): we can access/change parser contexts from the itemize()
1231 function.
1232
1233 Derived classes should not override this. If needed, they should
1234 override do_itemize().
1235
1236 @param pc current parse context
1237 @param [out] res pointer to "this" or to a newly allocated
1238 replacement object to use in the Item tree instead
1239
1240 @retval false success
1241 @retval true syntax/OOM/etc error
1242 */
1243 // Visual Studio with MSVC_CPPCHECK=ON gives warning C26435:
1244 // Function <fun> should specify exactly one of
1245 // 'virtual', 'override', or 'final'
1248 virtual bool itemize(Parse_context *pc, Item **res) final {
1249 // For condition#2 below ... If position is empty, this item was not
1250 // created in the parser; so don't show it in the parse tree.
1251 if (pc->m_show_parse_tree == nullptr || this->m_pos.is_empty())
1252 return do_itemize(pc, res);
1253
1254 Show_parse_tree *tree = pc->m_show_parse_tree.get();
1255
1256 if (begin_parse_tree(tree)) return true;
1257
1258 if (do_itemize(pc, res)) return true;
1259
1260 if (end_parse_tree(tree)) return true;
1261
1262 return false;
1263 }
1265
1266 void rename(char *new_name);
1267 void init_make_field(Send_field *tmp_field, enum enum_field_types type);
1268 /**
1269 Called for every Item after use (preparation and execution).
1270 Release all allocated resources, such as dynamic memory.
1271 Prepare for new execution by clearing cached values.
1272 Do not remove values allocated during preparation, destructor handles this.
1273 */
1274 virtual void cleanup() { marker = MARKER_NONE; }
1275 /**
1276 Called when an item has been removed, can be used to notify external
1277 objects about the removal, e.g subquery predicates that are part of
1278 the sj_candidates container.
1279 */
1280 virtual void notify_removal() {}
1281 virtual void make_field(Send_field *field);
1282 virtual Field *make_string_field(TABLE *table) const;
1283 virtual bool fix_fields(THD *, Item **);
1284 /**
1285 Fix after tables have been moved from one query_block level to the parent
1286 level, e.g by semijoin conversion.
1287 Basically re-calculate all attributes dependent on the tables.
1288
1289 @param parent_query_block query_block that tables are moved to.
1290 @param removed_query_block query_block that tables are moved away from,
1291 child of parent_query_block.
1292 */
1293 virtual void fix_after_pullout(Query_block *parent_query_block
1294 [[maybe_unused]],
1295 Query_block *removed_query_block
1296 [[maybe_unused]]) {}
1297 /*
1298 should be used in case where we are sure that we do not need
1299 complete fix_fields() procedure.
1300 */
1301 inline void quick_fix_field() { fixed = true; }
1302 virtual void set_can_use_prefix_key() {}
1303
1304 /**
1305 Propagate data type specifications into parameters and user variables.
1306 If item has descendants, propagate type recursively into these.
1307
1308 @param thd thread handler
1309 @param type Data type properties that are propagated
1310
1311 @returns false if success, true if error
1312 */
1313 virtual bool propagate_type(THD *thd [[maybe_unused]],
1314 const Type_properties &type [[maybe_unused]]) {
1315 return false;
1316 }
1317
1318 /**
1319 Wrapper for easier calling of propagate_type(const Type_properties &).
1320 @param thd thread handler
1321 @param def type to make Type_properties object
1322 @param pin if true: also mark the type as pinned
1323 @param inherit if true: also mark the type as inherited
1324
1325 @returns false if success, true if error
1326 */
1328 bool pin = false, bool inherit = false) {
1329 /*
1330 Propagate supplied type if types have not yet been assigned to expression,
1331 or type is pinned, in which case the supplied type overrides the
1332 actual type of parameters. Note we do not support "pinning" of
1333 expressions containing parameters, only standalone parameters,
1334 but this is a very minor problem.
1335 */
1336 if (data_type() != MYSQL_TYPE_INVALID && !(pin && type() == PARAM_ITEM))
1337 return false;
1338 if (propagate_type(thd,
1339 (def == MYSQL_TYPE_VARCHAR)
1341 : (def == MYSQL_TYPE_JSON)
1343 : Type_properties(def)))
1344 return true;
1345 if (pin) pin_data_type();
1346 if (inherit) set_data_type_inherited();
1347
1348 return false;
1349 }
1350
1351 /**
1352 For Items with data type JSON, mark that a string argument is treated
1353 as a scalar JSON value. Only relevant for the Item_param class.
1354 */
1355 virtual void mark_json_as_scalar() {}
1356
1357 /**
1358 If this item represents a IN/ALL/ANY/comparison_operator
1359 subquery, return that (along with data on how it will be executed).
1360 (These subqueries correspond to
1361 @see Item_in_subselect and @see Item_singlerow_subselect .) Also,
1362 @see FindContainedSubqueries() for context.
1363 @param outer_query_block the Query_block to which 'this' belongs.
1364 @returns The subquery that 'this' represents, if there is one.
1365 */
1366 virtual std::optional<ContainedSubquery> get_contained_subquery(
1367 const Query_block *outer_query_block [[maybe_unused]]) {
1368 return std::nullopt;
1369 }
1370
1371 protected:
1372 /**
1373 Helper function which does all of the work for
1374 save_in_field(Field*, bool), except some error checking common to
1375 all subclasses, which is performed by save_in_field() itself.
1376
1377 Subclasses that need to specialize the behaviour of
1378 save_in_field(), should override this function instead of
1379 save_in_field().
1380
1381 @param[in,out] field the field to save the item into
1382 @param no_conversions whether or not to allow conversions of the value
1383
1384 @return the status from saving into the field
1385 @retval TYPE_OK item saved without any errors or warnings
1386 @retval != TYPE_OK there were errors or warnings when saving the item
1387 */
1389 bool no_conversions);
1390
1391 public:
1392 /**
1393 Save the item into a field but do not emit any warnings.
1394
1395 @param field field to save the item into
1396 @param no_conversions whether or not to allow conversions of the value
1397
1398 @return the status from saving into the field
1399 @retval TYPE_OK item saved without any issues
1400 @retval != TYPE_OK there were issues saving the item
1401 */
1403 bool no_conversions);
1404 /**
1405 Save a temporal value in packed longlong format into a Field.
1406 Used in optimizer.
1407
1408 Subclasses that need to specialize this function, should override
1409 save_in_field_inner().
1410
1411 @param[in,out] field the field to save the item into
1412 @param no_conversions whether or not to allow conversions of the value
1413
1414 @return the status from saving into the field
1415 @retval TYPE_OK item saved without any errors or warnings
1416 @retval != TYPE_OK there were errors or warnings when saving the item
1417 */
1418 type_conversion_status save_in_field(Field *field, bool no_conversions);
1419
1420 /**
1421 A slightly faster value of save_in_field() that returns no error value
1422 (you will need to check thd->is_error() yourself), and does not support
1423 saving into hidden fields for functional indexes. Used by copy_funcs(),
1424 to avoid the functional call overhead and RAII setup of save_in_field().
1425 */
1426 void save_in_field_no_error_check(Field *field, bool no_conversions) {
1427 assert(!field->is_field_for_functional_index());
1428 save_in_field_inner(field, no_conversions);
1429 }
1430
1431 virtual void save_org_in_field(Field *field) { save_in_field(field, true); }
1432
1433 virtual bool send(Protocol *protocol, String *str);
1434 bool evaluate(THD *thd, String *str);
1435 /**
1436 Compare this item with another item for equality.
1437 If both pointers are the same, the items are equal.
1438 Both items must be of same type.
1439 For literal values, metadata must be the same and the values must be equal.
1440 Strings are compared with the embedded collation.
1441 For column references, table references and column names must be the same.
1442 For functions, the function type, function properties and arguments must
1443 be equal. Otherwise, see specific implementations.
1444 @todo: Current implementation requires that cache objects, ref objects
1445 and rollup wrappers are stripped away. This should be eliminated.
1446 */
1447 virtual bool eq(const Item *) const;
1448
1449 const Item *unwrap_for_eq() const;
1450
1451 virtual Item_result result_type() const { return REAL_RESULT; }
1452 /**
1453 Result type when an item appear in a numeric context.
1454 See Field::numeric_context_result_type() for more comments.
1455 */
1458 }
1459 /**
1460 Similar to result_type() but makes DATE, DATETIME, TIMESTAMP
1461 pretend to be numbers rather than strings.
1462 */
1465 : result_type();
1466 }
1467
1468 /**
1469 Set data type for item as inherited.
1470 Non-empty implementation only for dynamic parameters.
1471 */
1472 virtual void set_data_type_inherited() {}
1473
1474 /**
1475 Pin the data type for the item.
1476 Non-empty implementation only for dynamic parameters.
1477 */
1478 virtual void pin_data_type() {}
1479
1480 /// Retrieve the derived data type of the Item.
1482 return static_cast<enum_field_types>(m_data_type);
1483 }
1484
1485 /**
1486 Retrieve actual data type for an item. Equal to data_type() for
1487 all items, except parameters.
1488 */
1489 virtual enum_field_types actual_data_type() const { return data_type(); }
1490
1491 /**
1492 Get the default data (output) type for the specific item.
1493 Important for some SQL functions that may deliver multiple result types,
1494 and is used to determine data type for function's parameters that cannot
1495 be type-resolved by looking at the context.
1496 An example of such function is '+', which may return INT, DECIMAL,
1497 DOUBLE, depending on arguments.
1498 On the contrary, many other functions have a fixed output type, usually
1499 set with set_data_type_XXX(), which overrides the value of
1500 default_data_type(). For example, COS always returns DOUBLE,
1501 */
1503 // If data type has been set, the information returned here is irrelevant:
1504 assert(data_type() == MYSQL_TYPE_INVALID);
1505 return MYSQL_TYPE_VARCHAR;
1506 }
1507 /**
1508 Set the data type of the current Item. It is however recommended to
1509 use one of the type-specific setters if possible.
1510
1511 @param data_type The data type of this Item.
1512 */
1514 m_data_type = static_cast<uint8>(data_type);
1515 }
1516
1517 inline void set_data_type_null() {
1520 max_length = 0;
1521 set_nullable(true);
1522 }
1523
1524 inline void set_data_type_bool() {
1527 decimals = 0;
1528 max_length = 1;
1529 }
1530
1531 /**
1532 Set the data type of the Item to be a specific integer type
1533
1534 @param type Integer type
1535 @param unsigned_prop Whether the integer is signed or not
1536 @param max_width Maximum width of field in number of digits
1537 */
1538 inline void set_data_type_int(enum_field_types type, bool unsigned_prop,
1539 uint32 max_width) {
1540 assert(type == MYSQL_TYPE_TINY || type == MYSQL_TYPE_SHORT ||
1545 unsigned_flag = unsigned_prop;
1546 decimals = 0;
1547 fix_char_length(max_width);
1548 }
1549
1550 /**
1551 Set the data type of the Item to be longlong.
1552 Maximum display width is set to be the maximum of a 64-bit integer,
1553 but it may be adjusted later. The unsigned property is not affected.
1554 */
1558 decimals = 0;
1559 fix_char_length(21);
1560 }
1561
1562 /**
1563 Set the data type of the Item to be decimal.
1564 The unsigned property must have been set before calling this function.
1565
1566 @param precision Number of digits of precision
1567 @param scale Number of digits after decimal point.
1568 */
1569 inline void set_data_type_decimal(uint8 precision, uint8 scale) {
1572 assert(precision <= DECIMAL_MAX_PRECISION);
1573 decimals = scale;
1575 precision, scale, unsigned_flag));
1576 }
1577
1578 /// Set the data type of the Item to be double precision floating point.
1579 inline void set_data_type_double() {
1584 }
1585
1586 /// Set the data type of the Item to be single precision floating point.
1587 inline void set_data_type_float() {
1592 }
1593
1594 /**
1595 Set the Item to be variable length string. Actual type is determined from
1596 maximum string size. Collation must have been set before calling function.
1597
1598 @param max_l Maximum number of characters in string
1599 */
1600 inline void set_data_type_string(uint32 max_l) {
1607 else
1609 }
1610
1611 /**
1612 Set the Item to be variable length string. Like function above, but with
1613 larger string length precision.
1614
1615 @param max_char_length_arg Maximum number of characters in string
1616 */
1617 inline void set_data_type_string(ulonglong max_char_length_arg) {
1618 ulonglong max_result_length =
1619 max_char_length_arg * collation.collation->mbmaxlen;
1620 if (max_result_length > MAX_BLOB_WIDTH) {
1621 max_result_length = MAX_BLOB_WIDTH;
1622 m_nullable = true;
1623 }
1625 uint32(max_result_length / collation.collation->mbmaxlen));
1626 }
1627
1628 /**
1629 Set the Item to be variable length string. Like function above, but will
1630 also set character set and collation.
1631
1632 @param max_l Maximum number of characters in string
1633 @param cs Pointer to character set and collation struct
1634 */
1635 inline void set_data_type_string(uint32 max_l, const CHARSET_INFO *cs) {
1637 set_data_type_string(max_l);
1638 }
1639
1640 /**
1641 Set the Item to be variable length string. Like function above, but will
1642 also set full collation information.
1643
1644 @param max_l Maximum number of characters in string
1645 @param coll Ref to collation data, including derivation and repertoire
1646 */
1647 inline void set_data_type_string(uint32 max_l, const DTCollation &coll) {
1648 collation.set(coll);
1649 set_data_type_string(max_l);
1650 }
1651
1652 /**
1653 Set the Item to be fixed length string. Collation must have been set
1654 before calling function.
1655
1656 @param max_l Number of characters in string
1657 */
1658 inline void set_data_type_char(uint32 max_l) {
1659 assert(max_l <= MAX_CHAR_WIDTH);
1663 }
1664
1665 /**
1666 Set the Item to be fixed length string. Like function above, but will
1667 also set character set and collation.
1668
1669 @param max_l Maximum number of characters in string
1670 @param cs Pointer to character set and collation struct
1671 */
1672 inline void set_data_type_char(uint32 max_l, const CHARSET_INFO *cs) {
1674 set_data_type_char(max_l);
1675 }
1676
1677 /**
1678 Set the Item to be of BLOB type.
1679
1680 @param type Actual blob data type
1681 @param max_l Maximum number of characters in data type
1682 */
1687 ulonglong max_width = max_l * collation.collation->mbmaxlen;
1688 if (max_width > Field::MAX_LONG_BLOB_WIDTH) {
1689 max_width = Field::MAX_LONG_BLOB_WIDTH;
1690 }
1691 max_length = max_width;
1693 }
1694
1695 /// Set all type properties for Item of DATE type.
1696 inline void set_data_type_date() {
1699 decimals = 0;
1701 }
1702
1703 /**
1704 Set all type properties for Item of TIME type.
1705
1706 @param fsp Fractional seconds precision
1707 */
1708 inline void set_data_type_time(uint8 fsp) {
1711 decimals = fsp;
1712 max_length = MAX_TIME_WIDTH + fsp + (fsp > 0 ? 1 : 0);
1713 }
1714
1715 /**
1716 Set all properties for Item of DATETIME type.
1717
1718 @param fsp Fractional seconds precision
1719 */
1723 decimals = fsp;
1724 max_length = MAX_DATETIME_WIDTH + fsp + (fsp > 0 ? 1 : 0);
1725 }
1726
1727 /**
1728 Set all properties for Item of TIMESTAMP type.
1729
1730 @param fsp Fractional seconds precision
1731 */
1735 decimals = fsp;
1736 max_length = MAX_DATETIME_WIDTH + fsp + (fsp > 0 ? 1 : 0);
1737 }
1738
1739 /**
1740 Set the data type of the Item to be VECTOR.
1741 */
1746 max_length = max_l;
1747 }
1748
1749 /**
1750 Set the data type of the Item to be GEOMETRY.
1751 */
1757 }
1758 /**
1759 Set the data type of the Item to be JSON.
1760 */
1766 }
1767
1768 /**
1769 Set the data type of the Item to be YEAR.
1770 */
1774 decimals = 0;
1775 fix_char_length(4); // YYYY
1776 unsigned_flag = true;
1777 }
1778
1779 /**
1780 Set the data type of the Item to be bit.
1781
1782 @param max_bits Maximum number of bits to store in this field.
1783 */
1784 void set_data_type_bit(uint32 max_bits) {
1787 max_length = max_bits;
1788 unsigned_flag = true;
1789 }
1790
1791 /**
1792 Set data type properties of the item from the properties of another item.
1793
1794 @param item Item to set data type properties from.
1795 */
1796 inline void set_data_type_from_item(const Item *item) {
1797 set_data_type(item->data_type());
1798 collation = item->collation;
1799 max_length = item->max_length;
1800 decimals = item->decimals;
1802 }
1803
1804 /**
1805 Determine correct string field type, based on string length
1806
1807 @param max_bytes Maximum string size, in number of bytes
1808 */
1810 if (max_bytes > Field::MAX_MEDIUM_BLOB_WIDTH)
1811 return MYSQL_TYPE_LONG_BLOB;
1812 else if (max_bytes > Field::MAX_VARCHAR_WIDTH)
1814 else
1815 return MYSQL_TYPE_VARCHAR;
1816 }
1817
1818 /// Get the typelib information for an item of type set or enum
1819 virtual TYPELIB *get_typelib() const { return nullptr; }
1820
1821 virtual Item_result cast_to_int_type() const { return result_type(); }
1822 virtual enum Type type() const = 0;
1823
1824 bool aggregate_type(const char *name, Item **items, uint count);
1825
1826 /*
1827 Return information about function monotonicity. See comment for
1828 enum_monotonicity_info for details. This function can only be called
1829 after fix_fields() call.
1830 */
1832 return NON_MONOTONIC;
1833 }
1834
1835 /*
1836 Convert "func_arg $CMP$ const" half-interval into "FUNC(func_arg) $CMP2$
1837 const2"
1838
1839 SYNOPSIS
1840 val_int_endpoint()
1841 left_endp false <=> The interval is "x < const" or "x <= const"
1842 true <=> The interval is "x > const" or "x >= const"
1843
1844 incl_endp IN false <=> the comparison is '<' or '>'
1845 true <=> the comparison is '<=' or '>='
1846 OUT The same but for the "F(x) $CMP$ F(const)" comparison
1847
1848 DESCRIPTION
1849 This function is defined only for unary monotonic functions. The caller
1850 supplies the source half-interval
1851
1852 x $CMP$ const
1853
1854 The value of const is supplied implicitly as the value of this item's
1855 argument, the form of $CMP$ comparison is specified through the
1856 function's arguments. The call returns the result interval
1857
1858 F(x) $CMP2$ F(const)
1859
1860 passing back F(const) as the return value, and the form of $CMP2$
1861 through the out parameter. NULL values are assumed to be comparable and
1862 be less than any non-NULL values.
1863
1864 RETURN
1865 The output range bound, which equal to the value of val_int()
1866 - If the value of the function is NULL then the bound is the
1867 smallest possible value of LLONG_MIN
1868 */
1869 virtual longlong val_int_endpoint(bool left_endp [[maybe_unused]],
1870 bool *incl_endp [[maybe_unused]]) {
1871 assert(0);
1872 return 0;
1873 }
1874
1875 /* valXXX methods must return NULL or 0 or 0.0 if null_value is set. */
1876 /*
1877 Return double precision floating point representation of item.
1878
1879 SYNOPSIS
1880 val_real()
1881
1882 RETURN
1883 In case of NULL value return 0.0 and set null_value flag to true.
1884 If value is not null null_value flag will be reset to false.
1885 */
1886 virtual double val_real() = 0;
1887 /*
1888 Return integer representation of item.
1889
1890 SYNOPSIS
1891 val_int()
1892
1893 RETURN
1894 In case of NULL value return 0 and set null_value flag to true.
1895 If value is not null null_value flag will be reset to false.
1896 */
1897 virtual longlong val_int() = 0;
1898 /**
1899 Return date value of item in packed longlong format.
1900 */
1901 virtual longlong val_date_temporal();
1902 /**
1903 Return time value of item in packed longlong format.
1904 */
1905 virtual longlong val_time_temporal();
1906
1907 /**
1908 Return date or time value of item in packed longlong format,
1909 depending on item field type.
1910 */
1912 if (data_type() == MYSQL_TYPE_TIME) return val_time_temporal();
1913 assert(is_temporal_with_date());
1914 return val_date_temporal();
1915 }
1916
1917 /**
1918 Produces a key suitable for filesort. Most of the time, val_int() would
1919 suffice, but for temporal values, the packed value (as sent to the handler)
1920 is called for. It is also necessary that the value is in UTC. This function
1921 supplies just that.
1922
1923 @return A sort key value.
1924 */
1928 return val_int();
1929 }
1930
1931 /**
1932 Get date or time value in packed longlong format.
1933 Before conversion from MYSQL_TIME to packed format,
1934 the MYSQL_TIME value is rounded to "dec" fractional digits.
1935 */
1937
1938 /*
1939 This is just a shortcut to avoid the cast. You should still use
1940 unsigned_flag to check the sign of the item.
1941 */
1942 inline ulonglong val_uint() { return (ulonglong)val_int(); }
1943 /*
1944 Return string representation of this item object.
1945
1946 SYNOPSIS
1947 val_str()
1948 str an allocated buffer this or any nested Item object can use to
1949 store return value of this method.
1950
1951 NOTE
1952 Buffer passed via argument should only be used if the item itself
1953 doesn't have an own String buffer. In case when the item maintains
1954 it's own string buffer, it's preferable to return it instead to
1955 minimize number of mallocs/memcpys.
1956 The caller of this method can modify returned string, but only in case
1957 when it was allocated on heap, (is_alloced() is true). This allows
1958 the caller to efficiently use a buffer allocated by a child without
1959 having to allocate a buffer of it's own. The buffer, given to
1960 val_str() as argument, belongs to the caller and is later used by the
1961 caller at it's own choosing.
1962 A few implications from the above:
1963 - unless you return a string object which only points to your buffer
1964 but doesn't manages it you should be ready that it will be
1965 modified.
1966 - even for not allocated strings (is_alloced() == false) the caller
1967 can change charset (see Item_func_{typecast/binary}. XXX: is this
1968 a bug?
1969 - still you should try to minimize data copying and return internal
1970 object whenever possible.
1971
1972 RETURN
1973 In case of NULL value or error, return error_str() as this function will
1974 check if the return value may be null, and it will either set null_value
1975 to true and return nullptr or to false and it will return empty string.
1976 If value is not null set null_value flag to false before returning it.
1977 */
1978 virtual String *val_str(String *str) = 0;
1979
1980 /*
1981 Returns string representation of this item in ASCII format.
1982
1983 SYNOPSIS
1984 val_str_ascii()
1985 str - similar to val_str();
1986
1987 NOTE
1988 This method is introduced for performance optimization purposes.
1989
1990 1. val_str() result of some Items in string context
1991 depends on @@character_set_results.
1992 @@character_set_results can be set to a "real multibyte" character
1993 set like UCS2, UTF16, UTF32. (We'll use only UTF32 in the examples
1994 below for convenience.)
1995
1996 So the default string result of such functions
1997 in these circumstances is real multi-byte character set, like UTF32.
1998
1999 For example, all numbers in string context
2000 return result in @@character_set_results:
2001
2002 SELECT CONCAT(20010101); -> UTF32
2003
2004 We do sprintf() first (to get ASCII representation)
2005 and then convert to UTF32;
2006
2007 So these kind "data sources" can use ASCII representation
2008 internally, but return multi-byte data only because
2009 @@character_set_results wants so.
2010 Therefore, conversion from ASCII to UTF32 is applied internally.
2011
2012
2013 2. Some other functions need in fact ASCII input.
2014
2015 For example,
2016 inet_aton(), GeometryFromText(), Convert_TZ(), GET_FORMAT().
2017
2018 Similar, fields of certain type, like DATE, TIME,
2019 when you insert string data into them, expect in fact ASCII input.
2020 If they get non-ASCII input, for example UTF32, they
2021 convert input from UTF32 to ASCII, and then use ASCII
2022 representation to do further processing.
2023
2024
2025 3. Now imagine we pass result of a data source of the first type
2026 to a data destination of the second type.
2027
2028 What happens:
2029 a. data source converts data from ASCII to UTF32, because
2030 @@character_set_results wants so and passes the result to
2031 data destination.
2032 b. data destination gets UTF32 string.
2033 c. data destination converts UTF32 string to ASCII,
2034 because it needs ASCII representation to be able to handle data
2035 correctly.
2036
2037 As a result we get two steps of unnecessary conversion:
2038 From ASCII to UTF32, then from UTF32 to ASCII.
2039
2040 A better way to handle these situations is to pass ASCII
2041 representation directly from the source to the destination.
2042
2043 This is why val_str_ascii() introduced.
2044
2045 RETURN
2046 Similar to val_str()
2047 */
2048 virtual String *val_str_ascii(String *str);
2049
2050 /*
2051 Return decimal representation of item with fixed point.
2052
2053 SYNOPSIS
2054 val_decimal()
2055 decimal_buffer buffer which can be used by Item for returning value
2056 (but can be not)
2057
2058 NOTE
2059 Returned value should not be changed if it is not the same which was
2060 passed via argument.
2061
2062 RETURN
2063 Return pointer on my_decimal (it can be other then passed via argument)
2064 if value is not NULL (null_value flag will be reset to false).
2065 In case of NULL value it return 0 pointer and set null_value flag
2066 to true.
2067 */
2068 virtual my_decimal *val_decimal(my_decimal *decimal_buffer) = 0;
2069 /*
2070 Return boolean value of item.
2071
2072 RETURN
2073 false value is false or NULL
2074 true value is true (not equal to 0)
2075 */
2076 virtual bool val_bool();
2077
2078 /**
2079 Get a JSON value from an Item.
2080
2081 All subclasses that can return a JSON value, should override this
2082 function. The function in the base class is not expected to be
2083 called. If it is called, it most likely means that some subclass
2084 is missing an override of val_json().
2085
2086 @param[in,out] result The resulting Json_wrapper.
2087
2088 @return false if successful, true on failure
2089 */
2090 /* purecov: begin deadcode */
2091 virtual bool val_json(Json_wrapper *result [[maybe_unused]]) {
2092 assert(false);
2093 my_error(ER_NOT_SUPPORTED_YET, MYF(0), "item type for JSON");
2094 return error_json();
2095 }
2096 /* purecov: end */
2097
2098 /**
2099 Calculate the filter contribution that is relevant for table
2100 'filter_for_table' for this item.
2101
2102 @param thd Thread handler
2103 @param filter_for_table The table we are calculating filter effect for
2104 @param read_tables Tables earlier in the join sequence.
2105 Predicates for table 'filter_for_table' that
2106 rely on values from these tables can be part of
2107 the filter effect.
2108 @param fields_to_ignore Fields in 'filter_for_table' that should not
2109 be part of the filter calculation. The filtering
2110 effect of these fields is already part of the
2111 calculation somehow (e.g. because there is a
2112 predicate "col = <const>", and the optimizer
2113 has decided to do ref access on 'col').
2114 @param rows_in_table The number of rows in table 'filter_for_table'
2115
2116 @return the filtering effect (between 0 and 1) this
2117 Item contributes with.
2118 */
2119 virtual float get_filtering_effect(THD *thd [[maybe_unused]],
2120 table_map filter_for_table
2121 [[maybe_unused]],
2122 table_map read_tables [[maybe_unused]],
2123 const MY_BITMAP *fields_to_ignore
2124 [[maybe_unused]],
2125 double rows_in_table [[maybe_unused]]) {
2126 // Filtering effect cannot be calculated for a table already read.
2127 assert((read_tables & filter_for_table) == 0);
2128 return COND_FILTER_ALLPASS;
2129 }
2130
2131 /**
2132 Get the value to return from val_json() in case of errors.
2133
2134 @see Item::error_bool
2135
2136 @return The value val_json() should return, which is true.
2137 */
2138 bool error_json() {
2140 return true;
2141 }
2142
2143 /**
2144 Convert a non-temporal type to date
2145 */
2147
2148 /**
2149 Convert a non-temporal type to time
2150 */
2152
2153 protected:
2154 /* Helper functions, see item_sum.cc */
2171 double val_real_from_decimal();
2172 double val_real_from_string();
2173
2174 /**
2175 Get the value to return from val_bool() in case of errors.
2176
2177 This function is called from val_bool() when an error has occurred
2178 and we need to return something to abort evaluation of the
2179 item. The expected pattern in val_bool() is
2180
2181 if (@<error condition@>)
2182 {
2183 my_error(...)
2184 return error_bool();
2185 }
2186
2187 @return The value val_bool() should return.
2188 */
2189 bool error_bool() {
2191 return false;
2192 }
2193
2194 /**
2195 Get the value to return from val_int() in case of errors.
2196
2197 @see Item::error_bool
2198
2199 @return The value val_int() should return.
2200 */
2203 return 0;
2204 }
2205
2206 /**
2207 Get the value to return from val_real() in case of errors.
2208
2209 @see Item::error_bool
2210
2211 @return The value val_real() should return.
2212 */
2213 double error_real() {
2215 return 0.0;
2216 }
2217
2218 /**
2219 Get the value to return from get_date() in case of errors.
2220
2221 @see Item::error_bool
2222
2223 @return The true: the function failed.
2224 */
2225 bool error_date() {
2227 return true;
2228 }
2229
2230 /**
2231 Get the value to return from get_time() in case of errors.
2232
2233 @see Item::error_bool
2234
2235 @return The true: the function failed.
2236 */
2237 bool error_time() {
2239 return true;
2240 }
2241
2242 public:
2243 /**
2244 Get the value to return from val_decimal() in case of errors.
2245
2246 @see Item::error_decimal
2247
2248 @return The value val_decimal() should return.
2249 */
2252 if (null_value) return nullptr;
2253 my_decimal_set_zero(decimal_value);
2254 return decimal_value;
2255 }
2256
2257 /**
2258 Get the value to return from val_str() in case of errors.
2259
2260 @see Item::error_bool
2261
2262 @return The value val_str() should return.
2263 */
2267 }
2268
2269 protected:
2270 /**
2271 Gets the value to return from val_str() when returning a NULL value.
2272 @return The value val_str() should return.
2273 */
2275 assert(m_nullable);
2276 null_value = true;
2277 return nullptr;
2278 }
2279
2280 /**
2281 Convert val_str() to date in MYSQL_TIME
2282 */
2284 /**
2285 Convert val_real() to date in MYSQL_TIME
2286 */
2288 /**
2289 Convert val_decimal() to date in MYSQL_TIME
2290 */
2292 /**
2293 Convert val_int() to date in MYSQL_TIME
2294 */
2296 /**
2297 Convert get_time() from time to date in MYSQL_TIME
2298 */
2299 bool get_date_from_time(MYSQL_TIME *ltime);
2300
2301 /**
2302 Convert a numeric type to date
2303 */
2304 bool get_date_from_numeric(MYSQL_TIME *ltime, my_time_flags_t fuzzydate);
2305
2306 /**
2307 Convert val_str() to time in MYSQL_TIME
2308 */
2309 bool get_time_from_string(MYSQL_TIME *ltime);
2310 /**
2311 Convert val_real() to time in MYSQL_TIME
2312 */
2313 bool get_time_from_real(MYSQL_TIME *ltime);
2314 /**
2315 Convert val_decimal() to time in MYSQL_TIME
2316 */
2317 bool get_time_from_decimal(MYSQL_TIME *ltime);
2318 /**
2319 Convert val_int() to time in MYSQL_TIME
2320 */
2321 bool get_time_from_int(MYSQL_TIME *ltime);
2322 /**
2323 Convert date to time
2324 */
2325 bool get_time_from_date(MYSQL_TIME *ltime);
2326 /**
2327 Convert datetime to time
2328 */
2330
2331 /**
2332 Convert a numeric type to time
2333 */
2334 bool get_time_from_numeric(MYSQL_TIME *ltime);
2335
2337
2339
2340 public:
2344
2345 /**
2346 If this Item is being materialized into a temporary table, returns the
2347 field that is being materialized into. (Typically, this is the
2348 “result_field” members for items that have one.)
2349 */
2351 DBUG_TRACE;
2352 return nullptr;
2353 }
2354 /* This is also used to create fields in CREATE ... SELECT: */
2355 virtual Field *tmp_table_field(TABLE *) { return nullptr; }
2356 virtual const char *full_name() const {
2357 return item_name.is_set() ? item_name.ptr() : "???";
2358 }
2359
2360 /* bit map of tables used by item */
2361 virtual table_map used_tables() const { return (table_map)0L; }
2362
2363 /**
2364 Return table map of tables that can't be NULL tables (tables that are
2365 used in a context where if they would contain a NULL row generated
2366 by a LEFT or RIGHT join, the item would not be true).
2367 This expression is used on WHERE item to determinate if a LEFT JOIN can be
2368 converted to a normal join.
2369 Generally this function should return used_tables() if the function
2370 would return null if any of the arguments are null
2371 As this is only used in the beginning of optimization, the value don't
2372 have to be updated in update_used_tables()
2373 */
2374 virtual table_map not_null_tables() const { return used_tables(); }
2375
2376 /**
2377 Returns true if this is a simple constant item like an integer, not
2378 a constant expression. Used in the optimizer to propagate basic constants.
2379 It is assumed that val_xxx() does not modify the item's state for
2380 such items. It is also assumed that val_str() can be called with nullptr
2381 as argument as val_str() will return an internally cached const string.
2382 */
2383 virtual bool basic_const_item() const { return false; }
2384 /**
2385 @returns true when a const item may be evaluated during resolving.
2386 Only const items that are basic const items are evaluated when
2387 resolving CREATE VIEW statements. For other statements, all
2388 const items may be evaluated during resolving.
2389 */
2390 bool may_eval_const_item(const THD *thd) const;
2391 /**
2392 @return cloned item if it is constant
2393 @retval nullptr if this is not const
2394 */
2395 virtual Item *clone_item() const { return nullptr; }
2396 virtual cond_result eq_cmp_result() const { return COND_OK; }
2397 inline uint float_length(uint decimals_par) const {
2398 return decimals != DECIMAL_NOT_SPECIFIED ? (DBL_DIG + 2 + decimals_par)
2399 : DBL_DIG + 8;
2400 }
2401 virtual uint decimal_precision() const;
2402 inline int decimal_int_part() const {
2404 }
2405 /**
2406 TIME precision of the item: 0..6
2407 */
2408 virtual uint time_precision();
2409 /**
2410 DATETIME precision of the item: 0..6
2411 */
2412 virtual uint datetime_precision();
2413 /**
2414 Returns true if item is constant, regardless of query evaluation state.
2415 An expression is constant if it:
2416 - refers no tables.
2417 - refers no subqueries that refers any tables.
2418 - refers no non-deterministic functions.
2419 - refers no statement parameters.
2420 - contains no group expression under rollup
2421 */
2422 bool const_item() const { return (used_tables() == 0); }
2423 /**
2424 Returns true if item is constant during one query execution.
2425 If const_for_execution() is true but const_item() is false, value is
2426 not available before tables have been locked and parameters have been
2427 assigned values. This applies to
2428 - statement parameters
2429 - non-dependent subqueries
2430 - deterministic stored functions that contain SQL code.
2431 For items where the default implementation of used_tables() and
2432 const_item() are effective, const_item() will always return true.
2433 */
2434 bool const_for_execution() const {
2435 return !(used_tables() & ~INNER_TABLE_BIT);
2436 }
2437
2438 /**
2439 Return true if this is a const item that may be evaluated in
2440 the current phase of statement processing.
2441 - No evaluation is performed when analyzing a view, otherwise:
2442 - Items that have the const_item() property can always be evaluated.
2443 - Items that have the const_for_execution() property can be evaluated when
2444 tables are locked (ie during optimization or execution).
2445
2446 This function should be used in the following circumstances:
2447 - during preparation to check whether an item can be permanently transformed
2448 - to check that an item is constant in functions that may be used in both
2449 the preparation and optimization phases.
2450
2451 This function should not be used by code that is called during optimization
2452 and/or execution only. Use const_for_execution() in this case.
2453 */
2454 bool may_evaluate_const(const THD *thd) const;
2455
2456 /**
2457 @returns true if this item is non-deterministic, which means that a
2458 has a component that must be evaluated once per row in
2459 execution of a JOIN query.
2460 */
2462
2463 /**
2464 @returns true if this item is an outer reference, usually this means that
2465 it references a column that contained in a table located in
2466 the FROM clause of an outer query block.
2467 */
2468 bool is_outer_reference() const {
2470 }
2471
2472 /**
2473 This method is used for to:
2474 - to generate a view definition query (SELECT-statement);
2475 - to generate a SQL-query for EXPLAIN EXTENDED;
2476 - to generate a SQL-query to be shown in INFORMATION_SCHEMA;
2477 - to generate a SQL-query that looks like a prepared statement for
2478 query_rewrite
2479 - debug.
2480
2481 For more information about view definition query, INFORMATION_SCHEMA
2482 query and why they should be generated from the Item-tree, @see
2483 mysql_register_view().
2484 */
2485 virtual void print(const THD *, String *str, enum_query_type) const {
2486 str->append(full_name());
2487 }
2488
2489 void print_item_w_name(const THD *thd, String *,
2490 enum_query_type query_type) const;
2491 /**
2492 Prints the item when it's part of ORDER BY and GROUP BY.
2493 @param thd Thread handle
2494 @param str String to print to
2495 @param query_type How to format the item
2496 @param used_alias The alias with which this item was referenced, or
2497 nullptr if it was not referenced with an alias.
2498 */
2499 void print_for_order(const THD *thd, String *str, enum_query_type query_type,
2500 const char *used_alias) const;
2501
2502 /**
2503 Updates used tables, not null tables information and accumulates
2504 properties up the item tree, cf. used_tables_cache, not_null_tables_cache
2505 and m_accum_properties.
2506
2507 TODO(sgunders): Consider just removing these caches; it causes a lot of bugs
2508 (cache invalidation is known to be a complex problem), and the performance
2509 benefits are dubious.
2510 */
2511 virtual void update_used_tables() {}
2512
2514 return false;
2515 }
2516 /* Called for items that really have to be split */
2517 bool split_sum_func2(THD *thd, Ref_item_array ref_item_array,
2518 mem_root_deque<Item *> *fields, Item **ref,
2519 bool skip_registered);
2520 virtual bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) = 0;
2521 virtual bool get_time(MYSQL_TIME *ltime) = 0;
2522 /**
2523 Get timestamp in "struct timeval" format.
2524 @retval false on success
2525 @retval true on error
2526 */
2527 virtual bool get_timeval(my_timeval *tm, int *warnings);
2528 /**
2529 The method allows to determine nullness of a complex expression
2530 without fully evaluating it, instead of calling val*() then
2531 checking null_value. Used in Item_func_isnull/Item_func_isnotnull
2532 and Item_sum_count/Item_sum_count_distinct.
2533 Any item which can be NULL must implement this method.
2534
2535 @retval false if the expression is not NULL.
2536 @retval true if the expression is NULL, or evaluation caused an error.
2537 The null_value member is set according to the return value.
2538 */
2539 virtual bool is_null() { return false; }
2540
2541 /**
2542 Make sure the null_value member has a correct value.
2543 null_value is set true also when evaluation causes error.
2544
2545 @returns false if success, true if error
2546 */
2547 bool update_null_value();
2548
2549 /**
2550 Apply the IS TRUE truth property, meaning that an UNKNOWN result and a
2551 FALSE result are treated the same.
2552
2553 This property is applied e.g to all conditions in WHERE, HAVING and ON
2554 clauses, and is recursively applied to operands of AND, OR
2555 operators. Some items (currently AND and subquery predicates) may enable
2556 special optimizations when they have this property.
2557 */
2558 virtual void apply_is_true() {}
2559 /*
2560 set field of temporary table for Item which can be switched on temporary
2561 table during query processing (grouping and so on). @see
2562 Item_result_field.
2563 */
2564 virtual void set_result_field(Field *) {}
2565 virtual bool is_result_field() const { return false; }
2566 virtual Field *get_result_field() const { return nullptr; }
2567 virtual bool is_bool_func() const { return false; }
2568 /*
2569 Set value of aggregate function in case of no rows for grouping were found.
2570 Also used for subqueries with outer references in SELECT list.
2571 */
2572 virtual void no_rows_in_result() {}
2573 virtual Item *copy_or_same(THD *) { return this; }
2574 virtual Item *copy_andor_structure(THD *) { return this; }
2575 /**
2576 @returns the "real item" underlying the owner object. Used to strip away
2577 Item_ref objects.
2578 @note remember to implement both real_item() functions in sub classes!
2579 */
2580 virtual Item *real_item() { return this; }
2581 virtual const Item *real_item() const { return this; }
2582 /**
2583 If an Item is materialized in a temporary table, a different Item may have
2584 to be used in the part of the query that runs after the materialization.
2585 For instance, if the Item was an Item_field, the new Item_field needs to
2586 point into the temporary table instead of the original one, but if, on the
2587 other hand, the Item was a literal constant, it can be reused as-is.
2588 This function encapsulates these policies for the different kinds of Items.
2589 See also get_tmp_table_field().
2590
2591 TODO: Document how aggregate functions (Item_sum) are handled.
2592 */
2593 virtual Item *get_tmp_table_item(THD *thd) { return copy_or_same(thd); }
2594
2595 static const CHARSET_INFO *default_charset();
2596 virtual const CHARSET_INFO *compare_collation() const { return nullptr; }
2597
2598 /*
2599 For backward compatibility, to make numeric
2600 data types return "binary" charset in client-side metadata.
2601 */
2604 : &my_charset_bin;
2605 }
2606
2607 /**
2608 Traverses a tree of Items in prefix and/or postfix order.
2609 Optionally walks into subqueries.
2610
2611 @param processor processor function to be invoked per item
2612 returns true to abort traversal, false to continue
2613 @param walk controls how to traverse the item tree
2614 enum_walk::PREFIX: call processor before invoking
2615 children enum_walk::POSTFIX: call processor after invoking children
2616 enum_walk::SUBQUERY go down into subqueries
2617 walk values are bit-coded and may be combined.
2618 Omitting both enum_walk::PREFIX and enum_walk::POSTFIX
2619 is undefined behaviour.
2620 @param arg Optional pointer to a walk-specific object
2621
2622 @retval false walk succeeded
2623 @retval true walk aborted
2624 by agreement, an error may have been reported
2625 */
2626
2627 virtual bool walk(Item_processor processor, enum_walk walk [[maybe_unused]],
2628 uchar *arg) {
2629 return ((walk & enum_walk::PREFIX) && (this->*processor)(arg)) ||
2630 ((walk & enum_walk::POSTFIX) && (this->*processor)(arg));
2631 }
2632
2633 /** @see WalkItem, CompileItem, TransformItem */
2634 template <class T>
2636 return (*reinterpret_cast<std::remove_reference_t<T> *>(arg))(this);
2637 }
2638
2639 /** See CompileItem */
2640 template <class T>
2642 return (*reinterpret_cast<std::remove_reference_t<T> *>(*arg))(this);
2643 }
2644
2645 /**
2646 Perform a generic transformation of the Item tree, by adding zero or
2647 more additional Item objects to it.
2648
2649 @param transformer Transformer function
2650 @param[in,out] arg Pointer to struct used by transformer function
2651
2652 @returns Returned item tree after transformation, NULL if error
2653
2654 Transformation is performed as follows:
2655
2656 @code
2657 transform()
2658 {
2659 transform children if any;
2660 return this->*some_transformer(...);
2661 }
2662 @endcode
2663
2664 Note that unlike Item::compile(), transform() does not support an analyzer
2665 function, ie. all children are unconditionally invoked.
2666
2667 Item::transform() should handle all transformations during preparation.
2668 Notice that all transformations are permanent; they are not rolled back.
2669
2670 Use Item::compile() to perform transformations during optimization.
2671 */
2672 virtual Item *transform(Item_transformer transformer, uchar *arg);
2673
2674 /**
2675 Perform a generic "compilation" of the Item tree, ie transform the Item tree
2676 by adding zero or more Item objects to it.
2677
2678 @param analyzer Analyzer function, see details section
2679 @param[in,out] arg_p Pointer to struct used by analyzer function
2680 @param transformer Transformer function, see details section
2681 @param[in,out] arg_t Pointer to struct used by transformer function
2682
2683 @returns Returned item tree after transformation, NULL if error
2684
2685 The process of this transformation is assumed to be as follows:
2686
2687 @code
2688 compile()
2689 {
2690 if (this->*some_analyzer(...))
2691 {
2692 compile children if any;
2693 return this->*some_transformer(...);
2694 }
2695 else
2696 return this;
2697 }
2698 @endcode
2699
2700 i.e. analysis is performed top-down while transformation is done
2701 bottom-up. If no transformation is applied, the item is returned unchanged.
2702 A transformation error is indicated by returning a NULL pointer. Notice
2703 that the analyzer function should never cause an error.
2704
2705 The function is supposed to be used during the optimization stage of
2706 query execution. All new allocations are recorded using
2707 THD::change_item_tree() so that they can be rolled back after execution.
2708
2709 @todo Pass THD to compile() function, thus no need to use current_thd.
2710 */
2711 virtual Item *compile(Item_analyzer analyzer, uchar **arg_p,
2712 Item_transformer transformer, uchar *arg_t) {
2713 if ((this->*analyzer)(arg_p)) return ((this->*transformer)(arg_t));
2714 return this;
2715 }
2716
2717 virtual void traverse_cond(Cond_traverser traverser, void *arg,
2719 (*traverser)(this, arg);
2720 }
2721
2722 /*
2723 This is used to get the most recent version of any function in
2724 an item tree. The version is the version where a MySQL function
2725 was introduced in. So any function which is added should use
2726 this function and set the int_arg to maximum of the input data
2727 and their own version info.
2728 */
2729 virtual bool intro_version(uchar *) { return false; }
2730
2731 /// cleanup() item if it is resolved ('fixed').
2733 if (fixed) cleanup();
2734 return false;
2735 }
2736
2737 virtual bool collect_item_field_processor(uchar *) { return false; }
2738 virtual bool collect_item_field_or_ref_processor(uchar *) { return false; }
2739
2741 public:
2744 : m_items(fields_or_refs) {}
2747 const Collect_item_fields_or_refs &) = delete;
2748
2749 friend class Item_sum;
2750 friend class Item_field;
2751 friend class Item_ref;
2752 };
2753
2755 public:
2758 /// Used to compute \c Item_field's \c m_protected_by_any_value. Pushed and
2759 /// popped when walking arguments of \c Item_func_any_value.a
2762 Query_block *transformed_block)
2763 : m_item_fields_or_view_refs(fields_or_vr),
2764 m_transformed_block(transformed_block) {}
2766 delete;
2768 const Collect_item_fields_or_view_refs &) = delete;
2769
2770 friend class Item_sum;
2771 friend class Item_field;
2773 friend class Item_view_ref;
2774 };
2775
2776 /**
2777 Collects fields and view references that have the qualifying table
2778 in the specified query block.
2779 */
2781 return false;
2782 }
2783
2784 /**
2785 Item::walk function. Set bit in table->tmp_set for all fields in
2786 table 'arg' that are referred to by the Item.
2787 */
2788 virtual bool add_field_to_set_processor(uchar *) { return false; }
2789
2790 /// A processor to handle the select lex visitor framework.
2791 virtual bool visitor_processor(uchar *arg);
2792
2793 /**
2794 Item::walk function. Set bit in table->cond_set for all fields of
2795 all tables that are referred to by the Item.
2796 */
2797 virtual bool add_field_to_cond_set_processor(uchar *) { return false; }
2798
2799 /**
2800 Visitor interface for removing all column expressions (Item_field) in
2801 this expression tree from a bitmap. @see walk()
2802
2803 @param arg A MY_BITMAP* cast to unsigned char*, where the bits represent
2804 Field::field_index values.
2805 */
2806 virtual bool remove_column_from_bitmap(uchar *arg [[maybe_unused]]) {
2807 return false;
2808 }
2809 virtual bool find_item_in_field_list_processor(uchar *) { return false; }
2810 virtual bool change_context_processor(uchar *) { return false; }
2811 virtual bool find_item_processor(uchar *arg) { return this == (void *)arg; }
2813 return !basic_const_item();
2814 }
2815 /// Is this an Item_field which references the given Field argument?
2816 virtual bool find_field_processor(uchar *) { return false; }
2817 /// Wrap incompatible arguments in CAST nodes to the expected data types
2818 virtual bool cast_incompatible_args(uchar *) { return false; }
2819 /**
2820 Mark underlying field in read or write map of a table.
2821
2822 @param arg Mark_field object
2823 */
2824 virtual bool mark_field_in_map(uchar *arg [[maybe_unused]]) { return false; }
2825
2826 protected:
2827 /**
2828 Helper function for mark_field_in_map(uchar *arg).
2829
2830 @param mark_field Mark_field object
2831 @param field Field to be marked for read/write
2832 */
2833 static inline bool mark_field_in_map(Mark_field *mark_field, Field *field) {
2834 TABLE *table = mark_field->table;
2835 if (table != nullptr && table != field->table) return false;
2836
2837 table = field->table;
2838 table->mark_column_used(field, mark_field->mark);
2839
2840 return false;
2841 }
2842
2843 public:
2844 /**
2845 Reset execution state for such window function types
2846 as determined by arg
2847
2848 @param arg pointing to a bool which, if true, says to reset state
2849 for framing window function, else for non-framing
2850 */
2851 virtual bool reset_wf_state(uchar *arg [[maybe_unused]]) { return false; }
2852
2853 /**
2854 Return used table information for the specified query block (level).
2855 For a field that is resolved from this query block, return the table number.
2856 For a field that is resolved from a query block outer to the specified one,
2857 return OUTER_REF_TABLE_BIT
2858
2859 @param[in,out] arg pointer to an instance of class Used_tables, which is
2860 constructed with the query block as argument.
2861 The used tables information is accumulated in the field
2862 used_tables in this class.
2863
2864 @note This function is used to update used tables information after
2865 merging a query block (a subquery) with its parent.
2866 */
2867 virtual bool used_tables_for_level(uchar *arg [[maybe_unused]]) {
2868 return false;
2869 }
2870 /**
2871 Check privileges.
2872
2873 @param thd thread handle
2874 */
2875 virtual bool check_column_privileges(uchar *thd [[maybe_unused]]) {
2876 return false;
2877 }
2878 virtual bool inform_item_in_cond_of_tab(uchar *) { return false; }
2879 /**
2880 Bind objects from the current execution context to field objects in
2881 item trees. Typically used to bind Field objects from TABLEs to
2882 Item_field objects.
2883 */
2884 virtual void bind_fields() {}
2885
2886 /**
2887 Context object for (functions that override)
2888 Item::clean_up_after_removal().
2889 */
2891 public:
2893 assert(root != nullptr);
2894 }
2895
2897
2898 private:
2899 /**
2900 Pointer to Cleanup_after_removal_context containing from which
2901 select the walk started, i.e., the Query_block that contained the clause
2902 that was removed.
2903 */
2905
2906 friend class Item;
2907 friend class Item_sum;
2908 friend class Item_subselect;
2909 friend class Item_ref;
2910 };
2911 /**
2912 Clean up after removing the item from the item tree.
2913
2914 param arg pointer to a Cleanup_after_removal_context object
2915 @todo: If class ORDER is refactored so that all indirect
2916 grouping/ordering expressions are represented with Item_ref
2917 objects, all implementations of cleanup_after_removal() except
2918 the one for Item_ref can be removed.
2919 */
2920 virtual bool clean_up_after_removal(uchar *arg);
2921
2922 /// @see Distinct_check::check_query()
2923 virtual bool aggregate_check_distinct(uchar *) { return false; }
2924 /// @see Group_check::check_query()
2925 virtual bool aggregate_check_group(uchar *) { return false; }
2926 /// @see Group_check::analyze_conjunct()
2927 virtual bool is_strong_side_column_not_in_fd(uchar *) { return false; }
2928 /// @see Group_check::is_in_fd_of_underlying()
2929 virtual bool is_column_not_in_fd(uchar *) { return false; }
2930 virtual Bool3 local_column(const Query_block *) const {
2931 return Bool3::false3();
2932 }
2933
2934 /**
2935 Minion class under \c Collect_scalar_subquery_info ("Css"). Information
2936 about one scalar subquery being considered for transformation
2937 */
2938 struct Css_info {
2939 /// set of locations
2941 /// the scalar subquery
2944 /// Where did we find item above? Used when \c m_location == \c L_JOIN_COND,
2945 /// nullptr for other locations.
2947 /// If true, we can forego cardinality checking of the derived table
2949 /// If true, add a COALESCE around replaced subquery: used for implicitly
2950 /// grouped COUNT() in subquery select list when subquery is correlated
2951 bool m_add_coalesce{false};
2952 /// Set iff \c m_add_coalesce is true: we may get a NULL anyway even for
2953 /// COUNT if a HAVING clause is false in the subquery.
2955 /// Index of the having expression copied to select list
2957 };
2958
2959 /**
2960 Context struct used by walk method collect_scalar_subqueries to
2961 accumulate information about scalar subqueries found.
2962
2963 In: m_location of expression walked, m_join_condition_context
2964 Out: m_list
2965 */
2967 enum Location { L_SELECT = 1, L_WHERE = 2, L_HAVING = 4, L_JOIN_COND = 8 };
2968 /// accumulated all scalar subqueries found
2969 std::vector<Css_info> m_list;
2970 /// we are currently looking at this kind of clause, cf. enum Location
2975 friend class Item_sum;
2977 };
2978
2979 virtual bool collect_scalar_subqueries(uchar *) { return false; }
2980 virtual bool collect_grouped_aggregates(uchar *) { return false; }
2981 virtual bool collect_subqueries(uchar *) { return false; }
2982 virtual bool update_depended_from(uchar *) { return false; }
2983 /**
2984 Check if an aggregate is referenced from within the GROUP BY
2985 clause of the query block in which it is aggregated. Such
2986 references will be rejected.
2987 @see Item_ref::fix_fields()
2988 @retval true if this is an aggregate which is referenced from
2989 the GROUP BY clause of the aggregating query block
2990 @retval false otherwise
2991 */
2992 virtual bool has_aggregate_ref_in_group_by(uchar *) { return false; }
2993
2994 bool visit_all_analyzer(uchar **) { return true; }
2995 virtual bool cache_const_expr_analyzer(uchar **cache_item);
2997
2998 virtual bool equality_substitution_analyzer(uchar **) { return false; }
2999
3000 virtual Item *equality_substitution_transformer(uchar *) { return this; }
3001
3002 /**
3003 Check if a partition function is allowed.
3004
3005 @return whether a partition function is not accepted
3006
3007 @details
3008 check_partition_func_processor is used to check if a partition function
3009 uses an allowed function. An allowed function will always ensure that
3010 X=Y guarantees that also part_function(X)=part_function(Y) where X is
3011 a set of partition fields and so is Y. The problems comes mainly from
3012 character sets where two equal strings can be quite unequal. E.g. the
3013 german character for double s is equal to 2 s.
3014
3015 The default is that an item is not allowed
3016 in a partition function. Allowed functions
3017 can never depend on server version, they cannot depend on anything
3018 related to the environment. They can also only depend on a set of
3019 fields in the table itself. They cannot depend on other tables and
3020 cannot contain any queries and cannot contain udf's or similar.
3021 If a new Item class is defined and it inherits from a class that is
3022 allowed in a partition function then it is very important to consider
3023 whether this should be inherited to the new class. If not the function
3024 below should be defined in the new Item class.
3025
3026 The general behaviour is that most integer functions are allowed.
3027 If the partition function contains any multi-byte collations then
3028 the function check_part_func_fields will report an error on the
3029 partition function independent of what functions are used. So the
3030 only character sets allowed are single character collation and
3031 even for those only a limited set of functions are allowed. The
3032 problem with multi-byte collations is that almost every string
3033 function has the ability to change things such that two strings
3034 that are equal will not be equal after manipulated by a string
3035 function. E.g. two strings one contains a double s, there is a
3036 special german character that is equal to two s. Now assume a
3037 string function removes one character at this place, then in
3038 one the double s will be removed and in the other there will
3039 still be one s remaining and the strings are no longer equal
3040 and thus the partition function will not sort equal strings into
3041 the same partitions.
3042
3043 So the check if a partition function is valid is two steps. First
3044 check that the field types are valid, next check that the partition
3045 function is valid. The current set of partition functions valid
3046 assumes that there are no multi-byte collations amongst the partition
3047 fields.
3048 */
3049 virtual bool check_partition_func_processor(uchar *) { return true; }
3050 virtual bool subst_argument_checker(uchar **arg) {
3051 if (*arg) *arg = nullptr;
3052 return true;
3053 }
3054 virtual bool explain_subquery_checker(uchar **) { return true; }
3055 virtual Item *explain_subquery_propagator(uchar *) { return this; }
3056
3057 virtual Item *equal_fields_propagator(uchar *) { return this; }
3058 // Mark the item to not be part of substitution.
3059 virtual bool disable_constant_propagation(uchar *) { return false; }
3060
3062 // Stack of pointers to enclosing functions
3064 };
3065 virtual Item *replace_equal_field(uchar *) { return this; }
3066 virtual bool replace_equal_field_checker(uchar **) { return true; }
3067 /*
3068 Check if an expression value has allowed arguments, like DATE/DATETIME
3069 for date functions. Also used by partitioning code to reject
3070 timezone-dependent expressions in a (sub)partitioning function.
3071 */
3072 virtual bool check_valid_arguments_processor(uchar *) { return false; }
3073
3074 /**
3075 Check if this item is allowed for a virtual column or inside a
3076 default expression. Should be overridden in child classes.
3077
3078 @param[in,out] args Due to the limitation of Item::walk()
3079 it is declared as a pointer to uchar, underneath there's a actually a
3080 structure of type Check_function_as_value_generator_parameters.
3081 It is used mainly in Item_field.
3082
3083 @returns true if function is not accepted
3084 */
3085 virtual bool check_function_as_value_generator(uchar *args);
3086
3087 /**
3088 Check if a generated expression depends on DEFAULT function with
3089 specific column name as argument.
3090
3091 @param[in] args Name of column used as DEFAULT function argument.
3092
3093 @returns false if the function is not DEFAULT(args), otherwise true.
3094 */
3096 [[maybe_unused]]) {
3097 return false;
3098 }
3099 /**
3100 Check if all the columns present in this expression are from the
3101 derived table. Used in determining if a condition can be pushed
3102 down to derived table.
3103 */
3104 virtual bool is_valid_for_pushdown(uchar *arg [[maybe_unused]]) {
3105 // A generic item cannot be pushed down unless it's a constant
3106 // which does not have a subquery.
3107 return !const_item() || has_subquery();
3108 }
3109
3110 /**
3111 Check if all the columns present in this expression are present
3112 in PARTITION clause of window functions of the derived table.
3113 Used in checking if a condition can be pushed down to derived table.
3114 */
3115 virtual bool check_column_in_window_functions(uchar *arg [[maybe_unused]]) {
3116 return false;
3117 }
3118 /**
3119 Check if all the columns present in this expression are present
3120 in GROUP BY clause of the derived table. Used in checking if
3121 a condition can be pushed down to derived table.
3122 */
3123 virtual bool check_column_in_group_by(uchar *arg [[maybe_unused]]) {
3124 return false;
3125 }
3126 /**
3127 Assuming this expression is part of a condition that would be pushed to the
3128 WHERE clause of a materialized derived table, replace, in this expression,
3129 each derived table's column with a clone of the expression lying under it
3130 in the derived table's definition. We replace with a clone, because the
3131 condition can be pushed further down in case of nested derived tables.
3132 */
3133 virtual Item *replace_with_derived_expr(uchar *arg [[maybe_unused]]) {
3134 return this;
3135 }
3136 /**
3137 Assuming this expression is part of a condition that would be pushed to the
3138 HAVING clause of a materialized derived table, replace, in this expression,
3139 each derived table's column with a reference to the expression lying under
3140 it in the derived table's definition. Unlike replace_with_derived_expr, a
3141 clone is not used because HAVING condition will not be pushed further
3142 down in case of nested derived tables.
3143 */
3144 virtual Item *replace_with_derived_expr_ref(uchar *arg [[maybe_unused]]) {
3145 return this;
3146 }
3147 /**
3148 Assuming this expression is part of a condition that would be pushed to a
3149 materialized derived table, replace, in this expression, each view reference
3150 with a clone of the expression in merged derived table's definition.
3151 We replace with a clone, because the referenced item in a view reference
3152 is shared by all the view references to that expression.
3153 */
3154 virtual Item *replace_view_refs_with_clone(uchar *arg [[maybe_unused]]) {
3155 return this;
3156 }
3157 /*
3158 For SP local variable returns pointer to Item representing its
3159 current value and pointer to current Item otherwise.
3160 */
3161 virtual Item *this_item() { return this; }
3162 virtual const Item *this_item() const { return this; }
3163
3164 /*
3165 For SP local variable returns address of pointer to Item representing its
3166 current value and pointer passed via parameter otherwise.
3167 */
3168 virtual Item **this_item_addr(THD *, Item **addr_arg) { return addr_arg; }
3169
3170 // Row emulation
3171 virtual uint cols() const { return 1; }
3172 virtual Item *element_index(uint) { return this; }
3173 virtual Item **addr(uint) { return nullptr; }
3174 virtual bool check_cols(uint c);
3175 // It is not row => null inside is impossible
3176 virtual bool null_inside() { return false; }
3177 // used in row subselects to get value of elements
3178 virtual void bring_value() {}
3179
3180 Field *tmp_table_field_from_field_type(TABLE *table, bool fixed_length) const;
3181 virtual Item_field *field_for_view_update() { return nullptr; }
3182 /**
3183 Informs an item that it is wrapped in a truth test, in case it wants to
3184 transforms itself to implement this test by itself.
3185 @param thd Thread handle
3186 @param test Truth test
3187 */
3188 virtual Item *truth_transformer(THD *thd [[maybe_unused]],
3189 Bool_test test [[maybe_unused]]) {
3190 return nullptr;
3191 }
3192 virtual Item *update_value_transformer(uchar *) { return this; }
3193
3195 Query_block *m_trans_block; ///< Transformed query block
3196 Query_block *m_curr_block; ///< Transformed query block or a contained
3197 ///< subquery. Pushed when diving into
3198 ///< subqueries.
3199 Item_replacement(Query_block *transformed_block, Query_block *current_block)
3200 : m_trans_block(transformed_block), m_curr_block(current_block) {}
3201 };
3203 Field *m_target; ///< The field to be replaced
3204 Item_field *m_item; ///< The replacement field
3205 ///< replacement field iff outer ref
3207 enum class Mode {
3208 CONFLATE, // include both Item_field and Item_default_value
3209 FIELD, // ignore Item_default_value
3210 DEFAULT_VALUE // ignore Item_field
3211 };
3214 Mode default_value = Mode::CONFLATE)
3215 : Item_replacement(select, select),
3216 m_target(target),
3217 m_item(item),
3218 m_default_value(default_value) {}
3219 };
3220
3222 Item_func *m_target; ///< The function call to be replaced
3223 Item_field *m_item; ///< The replacement field
3225 Query_block *select)
3226 : Item_replacement(select, select),
3227 m_target(func_target),
3228 m_item(item) {}
3229 };
3230
3232 Item *m_target; ///< The item identifying the view_ref to be replaced
3233 Field *m_field; ///< The replacement field
3234 ///< subquery. Pushed when diving into
3235 ///< subqueries.
3237 : Item_replacement(select, select), m_target(target), m_field(field) {}
3238 };
3239
3244 : m_target(target), m_replacement(replacement) {}
3245 };
3246
3247 /**
3248 When walking the item tree seeing an Item_singlerow_subselect matching
3249 a target, replace it with a substitute field used when transforming
3250 scalar subqueries into derived tables. Cf.
3251 Query_block::transform_scalar_subqueries_to_join_with_derived.
3252 */
3253 virtual Item *replace_scalar_subquery(uchar *) { return this; }
3254
3255 /**
3256 Transform processor used by Query_block::transform_grouped_to_derived
3257 to replace fields which used to be at the transformed query block
3258 with corresponding fields in the new derived table containing the grouping
3259 operation of the original transformed query block.
3260 */
3261 virtual Item *replace_item_field(uchar *) { return this; }
3262 virtual Item *replace_func_call(uchar *) { return this; }
3263 virtual Item *replace_item_view_ref(uchar *) { return this; }
3264 virtual Item *replace_aggregate(uchar *) { return this; }
3265 virtual Item *replace_outer_ref(uchar *) { return this; }
3266
3271 : m_target(target), m_owner(owner) {}
3272 };
3273
3274 /**
3275 A walker processor overridden by Item_aggregate_ref, q.v.
3276 */
3277 virtual bool update_aggr_refs(uchar *) { return false; }
3278
3279 virtual Item *safe_charset_converter(THD *thd, const CHARSET_INFO *tocs);
3280 /**
3281 Delete this item.
3282 Note that item must have been cleanup up by calling Item::cleanup().
3283 */
3284 void delete_self() { delete this; }
3285
3286 /** @return whether the item is local to a stored procedure */
3287 virtual bool is_splocal() const { return false; }
3288
3289 /*
3290 Return Settable_routine_parameter interface of the Item. Return 0
3291 if this Item is not Settable_routine_parameter.
3292 */
3294 return nullptr;
3295 }
3296 inline bool is_temporal_with_date() const {
3298 }
3301 }
3302 inline bool is_temporal_with_time() const {
3304 }
3305 inline bool is_temporal() const {
3307 }
3308 /**
3309 Check whether this and the given item has compatible comparison context.
3310 Used by the equality propagation. See Item_field::equal_fields_propagator.
3311
3312 @return
3313 true if the context is the same or if fields could be
3314 compared as DATETIME values by the Arg_comparator.
3315 false otherwise.
3316 */
3317 inline bool has_compatible_context(Item *item) const {
3318 // If no explicit context has been set, assume the same type as the item
3319 const Item_result this_context =
3321 const Item_result other_context = item->cmp_context == INVALID_RESULT
3322 ? item->result_type()
3323 : item->cmp_context;
3324
3325 // Check if both items have the same context
3326 if (this_context == other_context) {
3327 return true;
3328 }
3329 /* DATETIME comparison context. */
3331 return item->is_temporal_with_date() || other_context == STRING_RESULT;
3332 if (item->is_temporal_with_date())
3333 return is_temporal_with_date() || this_context == STRING_RESULT;
3334 return false;
3335 }
3337 return Field::GEOM_GEOMETRY;
3338 }
3339 String *check_well_formed_result(String *str, bool send_error, bool truncate);
3340 bool eq_by_collation(Item *item, const CHARSET_INFO *cs);
3341
3343 m_cost.Compute(*this);
3344 return m_cost;
3345 }
3346
3347 /**
3348 @return maximum number of characters that this Item can store
3349 If Item is of string or blob type, return max string length in bytes
3350 divided by bytes per character, otherwise return max_length.
3351 @todo - check if collation for other types should have mbmaxlen = 1
3352 */
3354 /*
3355 Length of e.g. 5.5e5 in an expression such as GREATEST(5.5e5, '5') is 5
3356 (length of that string) although length of the actual value is 6.
3357 Return MAX_DOUBLE_STR_LENGTH to prevent truncation of data without having
3358 to evaluate the value of the item.
3359 */
3360 const uint32 max_len =
3362 if (result_type() == STRING_RESULT)
3363 return max_len / collation.collation->mbmaxlen;
3364 return max_len;
3365 }
3366
3368 if (cs == &my_charset_bin && result_type() == STRING_RESULT) {
3369 return max_length;
3370 }
3371 return max_char_length();
3372 }
3373
3374 inline void fix_char_length(uint32 max_char_length_arg) {
3375 max_length = char_to_byte_length_safe(max_char_length_arg,
3377 }
3378
3379 /*
3380 Return true if the item points to a column of an outer-joined table.
3381 */
3382 virtual bool is_outer_field() const {
3383 assert(fixed);
3384 return false;
3385 }
3386
3387 /**
3388 Check if an item either is a blob field, or will be represented as a BLOB
3389 field if a field is created based on this item.
3390
3391 @retval true If a field based on this item will be a BLOB field,
3392 @retval false Otherwise.
3393 */
3394 bool is_blob_field() const;
3395
3396 /// @returns number of references to an item.
3397 uint reference_count() const { return m_ref_count; }
3398
3399 /// Increment reference count
3401 assert(!m_abandoned);
3402 ++m_ref_count;
3403 }
3404
3405 /// Decrement reference count
3407 assert(m_ref_count > 0);
3408 if (--m_ref_count == 0) m_abandoned = true;
3409 return m_ref_count;
3410 }
3411
3412 protected:
3413 /// Set accumulated properties for an Item
3414 void set_accum_properties(const Item *item) {
3416 }
3417
3418 /// Add more accumulated properties to an Item
3419 void add_accum_properties(const Item *item) {
3421 }
3422
3423 /// Set the "has subquery" property
3425
3426 /// Set the "has stored program" property
3428
3429 public:
3430 /// @return true if this item or any of its descendants contains a subquery.
3432
3433 /// @return true if this item or any of its descendants refers a stored func.
3434 bool has_stored_program() const {
3436 }
3437
3438 /// @return true if this item or any of its descendants is an aggregated func.
3440
3441 /// Set the "has aggregation" property
3443
3444 /// Reset the "has aggregation" property
3445 void reset_aggregation() { m_accum_properties &= ~PROP_AGGREGATION; }
3446
3447 /// @return true if this item or any of its descendants is a window func.
3449
3450 /// Set the "has window function" property
3452
3453 /**
3454 @return true if this item or any of its descendants within the same query
3455 has a reference to a GROUP BY modifier (such as ROLLUP)
3456 */
3459 }
3460
3461 /**
3462 Set the property: this item (tree) contains a reference to a GROUP BY
3463 modifier (such as ROLLUP)
3464 */
3467 }
3468
3469 /**
3470 @return true if this item or any of underlying items is a GROUPING function
3471 */
3472 bool has_grouping_func() const {
3474 }
3475
3476 /// Set the property: this item is a call to GROUPING
3478
3479 /// Whether this Item was created by the IN->EXISTS subquery transformation
3480 virtual bool created_by_in2exists() const { return false; }
3481
3483 if (has_subquery())
3485 }
3486
3487 /**
3488 Analyzer function for GC substitution. @see substitute_gc()
3489 */
3490 virtual bool gc_subst_analyzer(uchar **) { return false; }
3491 /**
3492 Transformer function for GC substitution. @see substitute_gc()
3493 */
3494 virtual Item *gc_subst_transformer(uchar *) { return this; }
3495
3496 /**
3497 A processor that replaces any Fields with a Create_field_wrapper. This
3498 will allow us to resolve functions during CREATE TABLE, where we only have
3499 Create_field available and not Field. Used for functional index
3500 implementation.
3501 */
3502 virtual bool replace_field_processor(uchar *) { return false; }
3503 /**
3504 Check if this item is of a type that is eligible for GC
3505 substitution. All items that belong to subclasses of Item_func are
3506 eligible for substitution. @see substitute_gc()
3507 Item_fields can also be eligible if they are given as an argument to
3508 a function that takes an array (the field can be substituted with a
3509 generated column that backs a multi-valued index on that field).
3510
3511 @param array true if the item is an argument to a function that takes an
3512 array, or false otherwise
3513 @return true if the expression is eligible for substitution, false otherwise
3514 */
3515 bool can_be_substituted_for_gc(bool array = false) const;
3516
3518 uint nitems);
3519 void aggregate_decimal_properties(Item **items, uint nitems);
3520 uint32 aggregate_char_width(Item **items, uint nitems);
3522 uint nitems);
3524 Item **items, uint nitems);
3525 void aggregate_bit_properties(Item **items, uint nitems);
3526
3527 /**
3528 This function applies only to Item_field objects referred to by an Item_ref
3529 object that has been marked as a const_item.
3530
3531 @param arg Keep track of whether an Item_ref refers to an Item_field.
3532 */
3533 virtual bool repoint_const_outer_ref(uchar *arg [[maybe_unused]]) {
3534 return false;
3535 }
3536 virtual bool strip_db_table_name_processor(uchar *) { return false; }
3537
3538 /**
3539 Compute the cost of evaluating this Item.
3540 @param root_cost The cost object to which the cost should be added.
3541 */
3542 virtual void compute_cost(CostOfItem *root_cost [[maybe_unused]]) const {}
3543
3544 bool is_abandoned() const { return m_abandoned; }
3545
3546 private:
3547 virtual bool subq_opt_away_processor(uchar *) { return false; }
3548
3549 public: // Start of data fields
3550 /**
3551 Intrusive list pointer for free list. If not null, points to the next
3552 Item on some Query_arena's free list. For instance, stored procedures
3553 have their own Query_arena's.
3554
3555 @see Query_arena::free_list
3556 */
3558
3559 protected:
3560 /// str_values's main purpose is to cache the value in save_in_field
3562
3563 public:
3564 /**
3565 Character set and collation properties assigned for this Item.
3566 Used if Item represents a character string expression.
3567 */
3569 Item_name_string item_name; ///< Name from query
3570 Item_name_string orig_name; ///< Original item name (if it was renamed)
3571 /**
3572 Maximum length of result of evaluating this item, in number of bytes.
3573 - For character or blob data types, max char length multiplied by max
3574 character size (collation.mbmaxlen).
3575 - For decimal type, it is the precision in digits plus sign (unless
3576 unsigned) plus decimal point (unless it has zero decimals).
3577 - For other numeric types, the default or specific display length.
3578 - For date/time types, the display length (10 for DATE, 10 + optional FSP
3579 for TIME, 19 + optional fsp for datetime/timestamp).
3580 - For bit, the number of bits.
3581 - For enum, the string length of the widest enum element.
3582 - For set, the sum of the string length of each set element plus separators.
3583 - For geometry, the maximum size of a BLOB (it's underlying storage type).
3584 - For json, the maximum size of a BLOB (it's underlying storage type).
3585 */
3586 uint32 max_length; ///< Maximum length, in bytes
3587 enum item_marker ///< Values for member 'marker'
3589 /// When contextualization or itemization adds an implicit comparison '0<>'
3590 /// (see make_condition()), to record that this Item_func_ne was created for
3591 /// this purpose; this value is tested during resolution.
3593 /// When doing constant propagation (e.g. change_cond_ref_to_const(), to
3594 /// remember that we have already processed the item.
3596 /// When creating an internal temporary table: says how to store BIT fields.
3598 /// When analyzing functional dependencies for only_full_group_by (says
3599 /// whether a nullable column can be treated at not nullable).
3601 /// When we change DISTINCT to GROUP BY: used for book-keeping of
3602 /// fields.
3604 /// When pushing conditions down to derived table: it says a condition
3605 /// contains only derived table's columns.
3607 /// Used during traversal to avoid deleting an item twice.
3609 /// When pushing index conditions: it says whether a condition uses only
3610 /// indexed columns.
3612 /**
3613 This member has several successive meanings, depending on the phase we're
3614 in (@see item_marker).
3615 The important property is that a phase must have a value (or few values)
3616 which is reserved for this phase. If it wants to set "marked", it assigns
3617 the value; it it wants to test if it is marked, it tests marker !=
3618 value. If the value has been assigned and the phase wants to cancel it can
3619 set marker to MARKER_NONE, which is a magic number which no phase
3620 reserves.
3621 A phase can expect 'marker' to be MARKER_NONE at the start of execution of
3622 a normal statement, at the start of preparation of a PS, and at the start
3623 of execution of a PS.
3624 A phase should not expect marker's value to survive after the phase's
3625 end - as a following phase may change it.
3626 */
3628 Item_result cmp_context; ///< Comparison context
3629 private:
3630 /**
3631 Number of references to this item. It is used for two purposes:
3632 1. When eliminating redundant expressions, the reference count is used
3633 to tell how many Item_ref objects that point to an item. When a
3634 sub-tree of items is eliminated, it is traversed and any item that
3635 is referenced from an Item_ref has its reference count decremented.
3636 Only when the reference count reaches zero is the item actually deleted.
3637 2. Keeping track of unused expressions selected from merged derived tables.
3638 An item that is added to the select list of a query block has its
3639 reference count set to 1. Any references from outer query blocks are
3640 through Item_ref objects, thus they will cause the reference count
3641 to be incremented. At end of resolving, the reference counts of all
3642 items in select list of merged derived tables are decremented, thus
3643 if the reference count becomes zero, the expression is known to
3644 be unused and can be removed.
3645 */
3647 bool m_abandoned{false}; ///< true if item has been fully de-referenced
3648 const bool is_parser_item; ///< true if allocated directly by parser
3649 uint8 m_data_type; ///< Data type assigned to Item
3650
3651 /**
3652 The cost of evaluating this item. This is only needed for predicates,
3653 therefore we use lazy evaluation.
3654 */
3656
3657 public:
3658 bool fixed; ///< True if item has been resolved
3659 /**
3660 Number of decimals in result when evaluating this item
3661 - For integer type, always zero.
3662 - For decimal type, number of decimals.
3663 - For float type, it may be DECIMAL_NOT_SPECIFIED
3664 - For time, datetime and timestamp, number of decimals in fractional second
3665 - For string types, may be decimals of cast source or DECIMAL_NOT_SPECIFIED
3666 */
3668
3669 bool is_nullable() const { return m_nullable; }
3670 void set_nullable(bool nullable) { m_nullable = nullable; }
3671
3672 private:
3673 /**
3674 True if this item may hold the NULL value(if null_value may be set to true).
3675
3676 For items that represent rows, it is true if one of the columns
3677 may be null.
3678
3679 For items that represent scalar or row subqueries, it is true if
3680 one of the returned columns could be null, or if the subquery
3681 could return zero rows.
3682
3683 It is worth noting that this information is correct only until
3684 equality propagation has been run by the optimization phase.
3685 Indeed, consider:
3686 select * from t1, t2,t3 where t1.pk=t2.a and t1.pk+1...
3687 the '+' is not nullable as t1.pk is not nullable;
3688 but if the optimizer chooses plan is t2-t3-t1, then, due to equality
3689 propagation it will replace t1.pk in '+' with t2.a (as t2 is before t1
3690 in plan), making the '+' capable of returning NULL when t2.a is NULL.
3691 */
3693
3694 public:
3695 bool null_value; ///< True if item is null
3697 bool m_is_window_function; ///< True if item represents window func
3698 /**
3699 If the item is in a SELECT list (Query_block::fields) and hidden is true,
3700 the item wasn't actually in the list as given by the user (it was added
3701 by the optimizer, to e.g. make sure it was part of a given
3702 materialization), and should not be returned in the actual result.
3703
3704 If the item is not in a SELECT list, the value is irrelevant.
3705 */
3706 bool hidden{false};
3707 /**
3708 True if item is a top most element in the expression being
3709 evaluated for a check constraint.
3710 */
3712
3713 protected:
3714 /**
3715 Set of properties that are calculated by accumulation from underlying items.
3716 Computed by constructors and fix_fields() and updated by
3717 update_used_tables(). The properties are accumulated up to the root of the
3718 current item tree, except they are not accumulated across subqueries and
3719 functions.
3720 */
3721 static constexpr uint8 PROP_SUBQUERY = 0x01;
3722 static constexpr uint8 PROP_STORED_PROGRAM = 0x02;
3723 static constexpr uint8 PROP_AGGREGATION = 0x04;
3724 static constexpr uint8 PROP_WINDOW_FUNCTION = 0x08;
3725 /**
3726 Set if the item or one or more of the underlying items contains a
3727 GROUP BY modifier (such as ROLLUP).
3728 */
3729 static constexpr uint8 PROP_HAS_GROUPING_SET_DEP = 0x10;
3730 /**
3731 Set if the item or one or more of the underlying items is a GROUPING
3732 function.
3733 */
3734 static constexpr uint8 PROP_GROUPING_FUNC = 0x20;
3735
3737
3738 public:
3739 /**
3740 Check if this expression can be used for partial update of a given
3741 JSON column.
3742
3743 For example, the expression `JSON_REPLACE(col, '$.foo', 'bar')`
3744 can be used to partially update the column `col`.
3745
3746 @param field the JSON column that is being updated
3747 @return true if this expression can be used for partial update,
3748 false otherwise
3749 */
3750 virtual bool supports_partial_update(const Field_json *field
3751 [[maybe_unused]]) const {
3752 return false;
3753 }
3754
3755 /**
3756 Whether the item returns array of its data type
3757 */
3758 virtual bool returns_array() const { return false; }
3759
3760 /**
3761 A helper function to ensure proper usage of CAST(.. AS .. ARRAY)
3762 */
3763 virtual void allow_array_cast() {}
3764};
3765
3766/**
3767 Descriptor of what and how to cache for
3768 Item::cache_const_expr_transformer/analyzer.
3769
3770*/
3771
3773 /// Path from the expression's top to the current item in item tree
3774 /// used to track parent of current item for caching JSON data
3776 /// Item to cache. Used as a binary flag, but kept as Item* for assertion
3777 Item *cache_item{nullptr};
3778 /// How to cache JSON data. @see Item::enum_const_item_cache
3780};
3781
3782/**
3783 A helper class to give in a functor to Item::walk(). Use as e.g.:
3784
3785 bool result = WalkItem(root_item, enum_walk::POSTFIX, [](Item *item) { ... });
3786
3787 TODO: Make Item::walk() just take in a functor in the first place, instead of
3788 a pointer-to-member and an opaque argument.
3789 */
3790template <class T>
3791inline bool WalkItem(Item *item, enum_walk walk, T &&functor) {
3792 return item->walk(&Item::walk_helper_thunk<T>, walk,
3793 reinterpret_cast<uchar *>(&functor));
3794}
3795
3796/**
3797 Overload for const 'item' and functor taking 'const Item*' argument.
3798*/
3799template <class T>
3800inline bool WalkItem(const Item *item, enum_walk walk, T &&functor) {
3801 auto to_const = [&](const Item *descendant) { return functor(descendant); };
3802 return WalkItem(const_cast<Item *>(item), walk, to_const);
3803}
3804
3805/**
3806 Same as WalkItem, but for Item::compile(). Use as e.g.:
3807
3808 Item *item = CompileItem(root_item,
3809 [](Item *item) { return true; }, // Analyzer.
3810 [](Item *item) { return item; }); // Transformer.
3811 */
3812template <class T, class U>
3813inline Item *CompileItem(Item *item, T &&analyzer, U &&transformer) {
3814 uchar *analyzer_ptr = reinterpret_cast<uchar *>(&analyzer);
3815 return item->compile(&Item::analyze_helper_thunk<T>, &analyzer_ptr,
3816 &Item::walk_helper_thunk<U>,
3817 reinterpret_cast<uchar *>(&transformer));
3818}
3819
3820/**
3821 Same as WalkItem, but for Item::transform(). Use as e.g.:
3822
3823 Item *item = TransformItem(root_item, [](Item *item) { return item; });
3824 */
3825template <class T>
3826Item *TransformItem(Item *item, T &&transformer) {
3827 return item->transform(&Item::walk_helper_thunk<T>,
3828 pointer_cast<uchar *>(&transformer));
3829}
3830
3833
3834 public:
3836 explicit Item_basic_constant(const POS &pos) : Item(pos), used_table_map(0) {}
3837
3838 /// @todo add implementation of basic_const_item
3839 /// and remove from subclasses as appropriate.
3840
3842 table_map used_tables() const override { return used_table_map; }
3843 bool check_function_as_value_generator(uchar *) override { return false; }
3844 /* to prevent drop fixed flag (no need parent cleanup call) */
3845 void cleanup() override {
3846 // @todo We should ensure we never change "basic constant" nodes.
3847 // We should then be able to add this assert:
3848 // assert(marker == MARKER_NONE);
3849 // and remove the call to Item::cleanup()
3850 Item::cleanup();
3851 }
3852 bool basic_const_item() const override { return true; }
3854};
3855
3856/*****************************************************************************
3857 The class is a base class for representation of stored routine variables in
3858 the Item-hierarchy. There are the following kinds of SP-vars:
3859 - local variables (Item_splocal);
3860 - CASE expression (Item_case_expr);
3861*****************************************************************************/
3862
3863class Item_sp_variable : public Item {
3864 public:
3866
3867 public:
3868#ifndef NDEBUG
3869 /*
3870 Routine to which this Item_splocal belongs. Used for checking if correct
3871 runtime context is used for variable handling.
3872 */
3873 sp_head *m_sp{nullptr};
3874#endif
3875
3876 public:
3877 Item_sp_variable(const Name_string sp_var_name);
3878
3879 table_map used_tables() const override { return INNER_TABLE_BIT; }
3880 bool fix_fields(THD *thd, Item **) override;
3881
3882 double val_real() override;
3883 longlong val_int() override;
3884 String *val_str(String *sp) override;
3885 my_decimal *val_decimal(my_decimal *decimal_value) override;
3886 bool val_json(Json_wrapper *result) override;
3887 bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override;
3888 bool get_time(MYSQL_TIME *ltime) override;
3889 bool is_null() override;
3890
3891 public:
3892 inline void make_field(Send_field *field) override;
3893 bool send(Protocol *protocol, String *str) override {
3894 // Need to override send() in case this_item() is an Item_field with a
3895 // ZEROFILL attribute.
3896 return this_item()->send(protocol, str);
3897 }
3898 bool is_valid_for_pushdown(uchar *arg [[maybe_unused]]) override {
3899 // It is ok to push down a condition like "column > SP_variable"
3900 return false;
3901 }
3902
3903 protected:
3905 Field *field, bool no_conversions) override;
3906};
3907
3908/*****************************************************************************
3909 Item_sp_variable inline implementation.
3910*****************************************************************************/
3911
3913 Item *it = this_item();
3915 it->make_field(field);
3916}
3917
3919 Field *field, bool no_conversions) {
3920 return this_item()->save_in_field(field, no_conversions);
3921}
3922
3923/*****************************************************************************
3924 A reference to local SP variable (incl. reference to SP parameter), used in
3925 runtime.
3926*****************************************************************************/
3927
3928class Item_splocal final : public Item_sp_variable,
3931
3932 public:
3933 /*
3934 If this variable is a parameter in LIMIT clause.
3935 Used only during NAME_CONST substitution, to not append
3936 NAME_CONST to the resulting query and thus not break
3937 the slave.
3938 */
3940 /*
3941 Position of this reference to SP variable in the statement (the
3942 statement itself is in sp_instr_stmt::m_query).
3943 This is valid only for references to SP variables in statements,
3944 excluding DECLARE CURSOR statement. It is used to replace references to SP
3945 variables with NAME_CONST calls when putting statements into the binary
3946 log.
3947 Value of 0 means that this object doesn't corresponding to reference to
3948 SP variable in query text.
3949 */
3951 /*
3952 Byte length of SP variable name in the statement (see pos_in_query).
3953 The value of this field may differ from the name_length value because
3954 name_length contains byte length of UTF8-encoded item name, but
3955 the query string (see sp_instr_stmt::m_query) is currently stored with
3956 a charset from the SET NAMES statement.
3957 */
3959
3960 Item_splocal(const Name_string sp_var_name, uint sp_var_idx,
3961 enum_field_types sp_var_type, uint pos_in_q = 0,
3962 uint len_in_q = 0);
3963
3964 bool is_splocal() const override { return true; }
3965
3966 Item *this_item() override;
3967 const Item *this_item() const override;
3968 Item **this_item_addr(THD *thd, Item **) override;
3969
3970 void print(const THD *thd, String *str,
3971 enum_query_type query_type) const override;
3972
3973 public:
3974 uint get_var_idx() const { return m_var_idx; }
3975
3976 Type type() const override { return ROUTINE_FIELD_ITEM; }
3977 Item_result result_type() const override {
3978 return type_to_result(data_type());
3979 }
3980 bool val_json(Json_wrapper *result) override;
3981
3982 private:
3983 bool set_value(THD *thd, sp_rcontext *ctx, Item **it) override;
3984
3985 public:
3987 return this;
3988 }
3989};
3990
3991/*****************************************************************************
3992 A reference to case expression in SP, used in runtime.
3993*****************************************************************************/
3994
3995class Item_case_expr final : public Item_sp_variable {
3996 public:
3997 Item_case_expr(uint case_expr_id);
3998
3999 public:
4000 Item *this_item() override;
4001 const Item *this_item() const override;
4002 Item **this_item_addr(THD *thd, Item **) override;
4003
4004 Type type() const override { return this_item()->type(); }
4005 Item_result result_type() const override {
4006 return this_item()->result_type();
4007 }
4008 /*
4009 NOTE: print() is intended to be used from views and for debug.
4010 Item_case_expr can not occur in views, so here it is only for debug
4011 purposes.
4012 */
4013 void print(const THD *thd, String *str,
4014 enum_query_type query_type) const override;
4015
4016 private:
4018};
4019
4020/*
4021 NAME_CONST(given_name, const_value).
4022 This 'function' has all properties of the supplied const_value (which is
4023 assumed to be a literal constant), and the name given_name.
4024
4025 This is used to replace references to SP variables when we write PROCEDURE
4026 statements into the binary log.
4027
4028 TODO
4029 Together with Item_splocal and Item::this_item() we can actually extract
4030 common a base of this class and Item_splocal. Maybe it is possible to
4031 extract a common base with class Item_ref, too.
4032*/
4033
4034class Item_name_const final : public Item {
4035 typedef Item super;
4036
4040
4041 public:
4042 Item_name_const(const POS &pos, Item *name_arg, Item *val);
4043
4044 bool do_itemize(Parse_context *pc, Item **res) override;
4045 bool fix_fields(THD *, Item **) override;
4046
4047 enum Type type() const override { return NAME_CONST_ITEM; }
4048 double val_real() override;
4049 longlong val_int() override;
4050 String *val_str(String *sp) override;
4051 my_decimal *val_decimal(my_decimal *) override;
4052 bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override;
4053 bool get_time(MYSQL_TIME *ltime) override;
4054 bool is_null() override;
4055 void print(const THD *thd, String *str,
4056 enum_query_type query_type) const override;
4057
4058 Item_result result_type() const override { return value_item->result_type(); }
4059
4061 // Item_name_const always wraps a literal, so there is no need to cache it.
4062 return false;
4063 }
4064
4065 protected:
4067 bool no_conversions) override {
4068 return value_item->save_in_field(field, no_conversions);
4069 }
4070};
4071
4073 Item **items, uint nitems, uint flags);
4074bool agg_item_set_converter(DTCollation &coll, const char *fname, Item **args,
4075 uint nargs, uint flags, int item_sep,
4076 bool only_consts);
4077bool agg_item_charsets(DTCollation &c, const char *name, Item **items,
4078 uint nitems, uint flags, int item_sep, bool only_consts);
4080 const char *name, Item **items,
4081 uint nitems, int item_sep = 1) {
4082 const uint flags = MY_COLL_ALLOW_SUPERSET_CONV |
4084 return agg_item_charsets(c, name, items, nitems, flags, item_sep, false);
4085}
4087 Item **items, uint nitems,
4088 int item_sep = 1) {
4089 const uint flags = MY_COLL_ALLOW_SUPERSET_CONV |
4091 return agg_item_charsets(c, name, items, nitems, flags, item_sep, true);
4092}
4093
4096
4097 public:
4099 explicit Item_num(const POS &pos) : super(pos) { collation.set_numeric(); }
4100
4101 virtual Item_num *neg() = 0;
4102 Item *safe_charset_converter(THD *thd, const CHARSET_INFO *tocs) override;
4103 bool check_partition_func_processor(uchar *) override { return false; }
4104};
4105
4106inline constexpr uint16 NO_FIELD_INDEX((uint16)(-1));
4107
4108class Item_ident : public Item {
4109 typedef Item super;
4110
4111 protected:
4112 /**
4113 The fields m_orig_db_name, m_orig_table_name and m_orig_field_name are
4114 maintained so that we can provide information about the origin of a
4115 column that may have been renamed within the query, e.g. as required by
4116 connectors.
4117
4118 Names the original schema of the table that is the source of the field.
4119 If field is from
4120 - a non-aliased base table, the same as db_name.
4121 - an aliased base table, the name of the schema of the base table.
4122 - an expression (including aggregation), a NULL pointer.
4123 - a derived table, the name of the schema of the underlying base table.
4124 - a view, the name of the schema of the underlying base table.
4125 - a temporary table (in optimization stage), the name of the schema of
4126 the source base table.
4127 */
4128 const char *m_orig_db_name;
4129 /**
4130 Names the original table that is the source of the field. If field is from
4131 - a non-aliased base table, the same as table_name.
4132 - an aliased base table, the name of the base table.
4133 - an expression (including aggregation), a NULL pointer.
4134 - a derived table, the name of the underlying base table.
4135 - a view, the name of the underlying base table.
4136 - a temporary table (in optimization stage), the name of the source base tbl
4137 */
4139 /**
4140 Names the field in the source base table. If field is from
4141 - an expression, a NULL pointer.
4142 - a view or base table and is not aliased, the same as field_name.
4143 - a view or base table and is aliased, the column name of the view or
4144 base table.
4145 - a derived table, the column name of the underlying base table.
4146 - a temporary table (in optimization stage), the name of the source column.
4147 */
4149 bool m_alias_of_expr; ///< if this Item's name is alias of SELECT expression
4150
4151 public:
4152 /**
4153 For regularly resolved column references, 'context' points to a name
4154 resolution context object belonging to the query block which simply
4155 contains the reference. To further clarify, in
4156 SELECT (SELECT t.a) FROM t;
4157 t.a is an Item_ident whose 'context' belongs to the subquery
4158 (context->query_block == that of the subquery).
4159 For column references that are part of a generated column expression,
4160 'context' points to a temporary name resolution context object during
4161 resolving, but is set to nullptr after resolving is done. Note that
4162 Item_ident::local_column() depends on that.
4163 */
4165 /**
4166 Schema name of the base table or view the column is part of.
4167 If an expression, a NULL pointer.
4168 If from a derived table, a NULL pointer.
4169 */
4170 const char *db_name;
4171 /**
4172 If column is from a non-aliased base table or view, name of base table or
4173 view.
4174 If column is from an aliased base table or view, the alias name.
4175 If column is from a derived table, the name of the derived table.
4176 If column is from an expression, a NULL pointer.
4177 */
4178 const char *table_name;
4179 /**
4180 If column is aliased, the column alias name.
4181 If column is from a non-aliased base table or view, the name of the
4182 column in that base table or view.
4183 If column is from an expression, a string generated from that expression.
4184
4185 Notice that a column can be aliased in two ways:
4186 1. With an explicit column alias, or @<as clause@>, or
4187 2. With only a column name specified, which differs from the table's
4188 column name due to case insensitivity.
4189 In both cases field_name will differ from m_orig_field_name.
4190 field_name is normally identical to Item::item_name.
4191 */
4192 const char *field_name;
4193 /**
4194 Points to the Table_ref object of the table or view that the column or
4195 reference is resolved against (only valid after resolving).
4196 Notice that for the following types of "tables", no Table_ref object is
4197 assigned and hence m_table_ref is NULL:
4198 - Temporary tables assigned by join optimizer for sorting and aggregation.
4199 - Stored procedure dummy tables.
4200 For fields referencing such tables, table number is always 0, and other
4201 uses of m_table_ref is not needed.
4202 */
4204 /**
4205 For a column or reference that is an outer reference, depended_from points
4206 to the qualifying query block, otherwise it is NULL
4207 (only valid after resolving).
4208 */
4210
4211 Item_ident(Name_resolution_context *context_arg, const char *db_name_arg,
4212 const char *table_name_arg, const char *field_name_arg)
4213 : m_orig_db_name(db_name_arg),
4214 m_orig_table_name(table_name_arg),
4215 m_orig_field_name(field_name_arg),
4216 m_alias_of_expr(false),
4217 context(context_arg),
4218 db_name(db_name_arg),
4219 table_name(table_name_arg),
4220 field_name(field_name_arg) {
4221 item_name.set(field_name_arg);
4222 }
4223
4224 Item_ident(const POS &pos, const char *db_name_arg,
4225 const char *table_name_arg, const char *field_name_arg)
4226 : super(pos),
4227 m_orig_db_name(db_name_arg),
4228 m_orig_table_name(table_name_arg),
4229 m_orig_field_name(field_name_arg),
4230 m_alias_of_expr(false),
4231 db_name(db_name_arg),
4232 table_name(table_name_arg),
4233 field_name(field_name_arg) {
4234 item_name.set(field_name_arg);
4235 }
4236
4237 /// Constructor used by Item_field & Item_*_ref (see Item comment)
4238
4240 : Item(thd, item),
4245 context(item->context),
4246 db_name(item->db_name),
4247 table_name(item->table_name),
4248 field_name(item->field_name),
4249 m_table_ref(item->m_table_ref),
4251
4252 bool do_itemize(Parse_context *pc, Item **res) override;
4253
4254 const char *full_name() const override;
4255 void set_orignal_db_name(const char *name_arg) { m_orig_db_name = name_arg; }
4256 void set_original_table_name(const char *name_arg) {
4257 m_orig_table_name = name_arg;
4258 }
4259 void set_original_field_name(const char *name_arg) {
4260 m_orig_field_name = name_arg;
4261 }
4262 const char *original_db_name() const { return m_orig_db_name; }
4263 const char *original_table_name() const { return m_orig_table_name; }
4264 const char *original_field_name() const { return m_orig_field_name; }
4265 void fix_after_pullout(Query_block *parent_query_block,
4266 Query_block *removed_query_block) override;
4267 bool aggregate_check_distinct(uchar *arg) override;
4268 bool aggregate_check_group(uchar *arg) override;
4269 Bool3 local_column(const Query_block *sl) const override;
4270
4271 void print(const THD *thd, String *str,
4272 enum_query_type query_type) const override {
4273 print(thd, str, query_type, db_name, table_name);
4274 }
4275
4276 protected:
4277 /**
4278 Function to print column name for a table
4279
4280 To print a column for a permanent table (picks up database and table from
4281 Item_ident object):
4282
4283 item->print(str, qt)
4284
4285 To print a column for a temporary table:
4286
4287 item->print(str, qt, specific_db, specific_table)
4288
4289 Items of temporary table fields have empty/NULL values of table_name and
4290 db_name. To print column names in a 3D form (`database`.`table`.`column`),
4291 this function prints db_name_arg and table_name_arg parameters instead of
4292 this->db_name and this->table_name respectively.
4293
4294 @param thd Thread handle.
4295 @param [out] str Output string buffer.
4296 @param query_type Bitmap to control printing details.
4297 @param db_name_arg String to output as a column database name.
4298 @param table_name_arg String to output as a column table name.
4299 */
4300 void print(const THD *thd, String *str, enum_query_type query_type,
4301 const char *db_name_arg, const char *table_name_arg) const;
4302
4303 public:
4304 ///< Argument object to change_context_processor
4308 };
4309 bool change_context_processor(uchar *arg) override {
4310 context = reinterpret_cast<Change_context *>(arg)->m_context;
4311 return false;
4312 }
4313
4314 /// @returns true if this Item's name is alias of SELECT expression
4315 bool is_alias_of_expr() const { return m_alias_of_expr; }
4316 /// Marks that this Item's name is alias of SELECT expression
4318
4319 /**
4320 Argument structure for walk processor Item::update_depended_from
4321 */
4323 Query_block *old_depended_from; // the transformed query block
4324 Query_block *new_depended_from; // the new derived table for grouping
4325 };
4326
4327 bool update_depended_from(uchar *) override;
4328
4329 /**
4330 @returns true if a part of this Item's full name (name or table name) is
4331 an alias.
4332 */
4333 virtual bool alias_name_used() const { return m_alias_of_expr; }
4335 const char *db_name, const char *table_name,
4337 bool any_privileges);
4338 bool is_strong_side_column_not_in_fd(uchar *arg) override;
4339 bool is_column_not_in_fd(uchar *arg) override;
4340};
4341
4342class Item_ident_for_show final : public Item {
4343 public:
4345 const char *db_name;
4346 const char *table_name;
4347
4348 Item_ident_for_show(Field *par_field, const char *db_arg,
4349 const char *table_name_arg)
4350 : field(par_field), db_name(db_arg), table_name(table_name_arg) {}
4351
4352 enum Type type() const override { return FIELD_ITEM; }
4353 bool fix_fields(THD *thd, Item **ref) override;
4354 double val_real() override { return field->val_real(); }
4355 longlong val_int() override { return field->val_int(); }
4356 String *val_str(String *str) override { return field->val_str(str); }
4358 return field->val_decimal(dec);
4359 }
4360 bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override {
4361 return field->get_date(ltime, fuzzydate);
4362 }
4363 bool get_time(MYSQL_TIME *ltime) override { return field->get_time(ltime); }
4364 void make_field(Send_field *tmp_field) override;
4366 return field->charset_for_protocol();
4367 }
4368};
4369
4370class Item_field : public Item_ident {
4372
4373 protected:
4374 void set_field(Field *field);
4375 void fix_after_pullout(Query_block *parent_query_block,
4376 Query_block *removed_query_block) override {
4377 super::fix_after_pullout(parent_query_block, removed_query_block);
4378
4379 // Update nullability information, as the table may have taken over
4380 // null_row status from the derived table it was part of.
4382 field->table->is_nullable());
4383 }
4385 bool no_conversions) override;
4386
4387 public:
4388 /// Source field
4389 Field *field{nullptr};
4390
4391 private:
4392 /// Result field
4394
4395 // save_in_field() and save_org_in_field() are often called repeatedly
4396 // with the same destination field (although the destination for the
4397 // two are distinct, thus two distinct caches). We detect this case by
4398 // storing the last destination, and whether it was of a compatible type
4399 // that we can memcpy into (see fields_are_memcpyable()). This saves time
4400 // doing the same type checking over and over again.
4401 //
4402 // The _memcpyable fields are uint32_t(-1) if the fields are not memcpyable,
4403 // and pack_length() (ie., the amount of bytes to copy) if they are.
4404 // See field_conv_with_cache(), where this logic is encapsulated.
4409
4410 /**
4411 If this field is derived from another field, e.g. it is reading a column
4412 from a temporary table which is populated from a base table, this member
4413 points to the field used to populate the temporary table column.
4414 */
4416
4417 /**
4418 State used for transforming scalar subqueries to JOINs with derived tables,
4419 cf. \c transform_grouped_to_derived. Has accessor.
4420 */
4422
4423 /**
4424 Holds a list of items whose values must be equal to the value of
4425 this field, during execution.
4426
4427 Used during optimization to perform multiple equality analysis,
4428 this analysis should be performed during preparation instead, so that
4429 Item_field can be const after preparation.
4430 */
4432
4433 public:
4434 /**
4435 Index for this field in table->field array. Holds NO_FIELD_INDEX
4436 if index value is not known.
4437 */
4440
4442 assert(item_equal != nullptr);
4443 item_equal_all_join_nests = item_equal;
4444 }
4445
4446 // A list of fields that are considered "equal" to this field. E.g., a query
4447 // on the form "a JOIN b ON a.i = b.i JOIN c ON b.i = c.i" would consider
4448 // a.i, b.i and c.i equal due to equality propagation. This is the same as
4449 // "item_equal" above, except that "item_equal" will only contain fields from
4450 // the same join nest. This is used by hash join and BKA when they need to
4451 // undo multi-equality propagation done by the optimizer. (The optimizer may
4452 // generate join conditions that references unreachable fields for said
4453 // iterators.) The split is done because NDB expects the list to only
4454 // contain fields from the same join nest.
4456 /// If true, the optimizer's constant propagation will not replace this item
4457 /// with an equal constant.
4459 /*
4460 if any_privileges set to true then here real effective privileges will
4461 be stored
4462 */
4464 /* field need any privileges (for VIEW creation) */
4465 bool any_privileges{false};
4466 /*
4467 if this field is used in a context where covering prefix keys
4468 are supported.
4469 */
4471 Item_field(Name_resolution_context *context_arg, const char *db_arg,
4472 const char *table_name_arg, const char *field_name_arg);
4473 Item_field(const POS &pos, const char *db_arg, const char *table_name_arg,
4474 const char *field_name_arg);
4475 Item_field(THD *thd, Item_field *item);
4476 Item_field(THD *thd, Name_resolution_context *context_arg, Field *field);
4478
4479 bool do_itemize(Parse_context *pc, Item **res) override;
4480
4481 enum Type type() const override { return FIELD_ITEM; }
4482 bool eq(const Item *item) const override;
4483 double val_real() override;
4484 longlong val_int() override;
4485 longlong val_time_temporal() override;
4486 longlong val_date_temporal() override;
4489 my_decimal *val_decimal(my_decimal *) override;
4490 String *val_str(String *) override;
4491 bool val_json(Json_wrapper *result) override;
4492 bool send(Protocol *protocol, String *str_arg) override;
4493 void reset_field(Field *f);
4494 bool fix_fields(THD *, Item **) override;
4495 void make_field(Send_field *tmp_field) override;
4496 void save_org_in_field(Field *field) override;
4497 table_map used_tables() const override;
4498 Item_result result_type() const override { return field->result_type(); }
4501 }
4502 TYPELIB *get_typelib() const override;
4504 return field->cast_to_int_type();
4505 }
4508 }
4509 longlong val_int_endpoint(bool left_endp, bool *incl_endp) override;
4510 void set_result_field(Field *field_arg) override { result_field = field_arg; }
4512 Field *tmp_table_field(TABLE *) override { return result_field; }
4515 item->base_item_field() != nullptr ? item->base_item_field() : item;
4516 }
4518 return m_base_item_field ? m_base_item_field : this;
4519 }
4520 bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override;
4521 bool get_time(MYSQL_TIME *ltime) override;
4522 bool get_timeval(my_timeval *tm, int *warnings) override;
4523 bool is_null() override {
4524 // NOTE: May return true even if maybe_null is not set!
4525 // This can happen if the underlying TABLE did not have a NULL row
4526 // at set_field() time (ie., table->is_null_row() was false),
4527 // but does now.
4528 return field->is_null();
4529 }
4530 Item *get_tmp_table_item(THD *thd) override;
4531 bool collect_item_field_processor(uchar *arg) override;
4532 bool collect_item_field_or_ref_processor(uchar *arg) override;
4534 bool add_field_to_set_processor(uchar *arg) override;
4535 bool add_field_to_cond_set_processor(uchar *) override;
4536 bool remove_column_from_bitmap(uchar *arg) override;
4537 bool find_item_in_field_list_processor(uchar *arg) override;
4538 bool find_field_processor(uchar *arg) override {
4539 return pointer_cast<Field *>(arg) == field;
4540 }
4541 bool check_function_as_value_generator(uchar *args) override;
4542 bool mark_field_in_map(uchar *arg) override {
4543 auto mark_field = pointer_cast<Mark_field *>(arg);
4544 bool rc = Item::mark_field_in_map(mark_field, field);
4546 rc |= Item::mark_field_in_map(mark_field, result_field);
4547 return rc;
4548 }
4549 bool used_tables_for_level(uchar *arg) override;
4550 bool check_column_privileges(uchar *arg) override;
4551 bool check_partition_func_processor(uchar *) override { return false; }
4552 void bind_fields() override;
4553 bool is_valid_for_pushdown(uchar *arg) override;
4554 bool check_column_in_window_functions(uchar *arg) override;
4555 bool check_column_in_group_by(uchar *arg) override;
4556 Item *replace_with_derived_expr(uchar *arg) override;
4558 void cleanup() override;
4559 void reset_field();
4560 Item_multi_eq *find_multi_equality(COND_EQUAL *cond_equal) const;
4561 bool subst_argument_checker(uchar **arg) override;
4562 Item *equal_fields_propagator(uchar *arg) override;
4563 Item *replace_item_field(uchar *) override;
4566 return false;
4567 }
4568 Item *replace_equal_field(uchar *) override;
4570 Item_field *field_for_view_update() override { return this; }