MySQL 8.0.31
Source Code Documentation
sql_optimizer.h
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1#ifndef SQL_OPTIMIZER_INCLUDED
2#define SQL_OPTIMIZER_INCLUDED
3
4/* Copyright (c) 2000, 2022, 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 also distributed 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 included with MySQL.
16
17 This program is distributed in the hope that it will be useful,
18 but WITHOUT ANY WARRANTY; without even the implied warranty of
19 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 GNU General Public License, version 2.0, for more details.
21
22 You should have received a copy of the GNU General Public License
23 along with this program; if not, write to the Free Software
24 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
25
26/**
27 @file sql/sql_optimizer.h
28 Classes used for query optimizations.
29*/
30
31#include <sys/types.h>
32
33#include <cstring>
34#include <memory>
35#include <utility>
36
37#include "field_types.h"
38#include "my_alloc.h"
39#include "my_base.h"
40#include "my_dbug.h"
41#include "my_table_map.h"
42#include "sql/field.h"
43#include "sql/item.h"
45#include "sql/mem_root_array.h"
46#include "sql/opt_explain_format.h" // Explain_sort_clause
47#include "sql/sql_executor.h"
48#include "sql/sql_lex.h"
49#include "sql/sql_list.h"
51#include "sql/sql_select.h" // Key_use
52#include "sql/table.h"
54
55enum class Subquery_strategy : int;
56class COND_EQUAL;
57class Item_subselect;
58class Item_sum;
60class THD;
61class Window;
62struct AccessPath;
63struct MYSQL_LOCK;
64
65class Item_equal;
66template <class T>
67class mem_root_deque;
68
69// Key_use has a trivial destructor, no need to run it from Mem_root_array.
71
73
74/*
75 This structure is used to collect info on potentially sargable
76 predicates in order to check whether they become sargable after
77 reading const tables.
78 We form a bitmap of indexes that can be used for sargable predicates.
79 Only such indexes are involved in range analysis.
80*/
81
83 Field *field; /* field against which to check sargability */
84 Item **arg_value; /* values of potential keys for lookups */
85 uint num_values; /* number of values in the above array */
86};
87
88/**
89 Wrapper for ORDER* pointer to trace origins of ORDER list
90
91 As far as ORDER is just a head object of ORDER expression
92 chain, we need some wrapper object to associate flags with
93 the whole ORDER list.
94*/
96 public:
97 ORDER *order; ///< ORDER expression that we are wrapping with this class
98 Explain_sort_clause src; ///< origin of order list
99
100 private:
101 int flags; ///< bitmap of Explain_sort_property
102
103 public:
105
107 : order(order_arg),
108 src(src_arg),
109 flags(order_arg ? ESP_EXISTS : ESP_none) {}
110
111 bool empty() const { return order == nullptr; }
112
113 void clean() {
114 order = nullptr;
115 src = ESC_none;
116 flags = ESP_none;
117 }
118
119 int get_flags() const {
120 assert(order);
121 return flags;
122 }
123};
124
125class JOIN {
126 public:
127 JOIN(THD *thd_arg, Query_block *select);
128 JOIN(const JOIN &rhs) = delete;
129 JOIN &operator=(const JOIN &rhs) = delete;
130
131 /// Query expression referring this query block
134 }
135
136 /// Query block that is optimized and executed using this JOIN
138 /// Thread handler
139 THD *const thd;
140
141 /**
142 Optimal query execution plan. Initialized with a tentative plan in
143 JOIN::make_join_plan() and later replaced with the optimal plan in
144 get_best_combination().
145 */
147 /// Array of QEP_TABs
148 QEP_TAB *qep_tab{nullptr};
149
150 /**
151 Array of plan operators representing the current (partial) best
152 plan. The array is allocated in JOIN::make_join_plan() and is valid only
153 inside this function. Initially (*best_ref[i]) == join_tab[i].
154 The optimizer reorders best_ref.
155 */
156 JOIN_TAB **best_ref{nullptr};
157 /// mapping between table indexes and JOIN_TABs
158 JOIN_TAB **map2table{nullptr};
159 /*
160 The table which has an index that allows to produce the required ordering.
161 A special value of 0x1 means that the ordering will be produced by
162 passing 1st non-const table to filesort(). NULL means no such table exists.
163 */
165
166 // Temporary tables that need to be cleaned up after the query.
167 // Only used for the hypergraph optimizer; the non-hypergraph optimizer
168 // uses QEP_TABs to hold the list of tables (including temporary tables).
171
172 // Allocated on the MEM_ROOT, but can hold some objects
173 // that allocate on the heap and thus need destruction.
175 };
178
179 // Similarly, filesorts that need to be cleaned up after the query.
180 // Only used for the hypergraph optimizer, for the same reason as above.
182
183 /**
184 Before plan has been created, "tables" denote number of input tables in the
185 query block and "primary_tables" is equal to "tables".
186 After plan has been created (after JOIN::get_best_combination()),
187 the JOIN_TAB objects are enumerated as follows:
188 - "tables" gives the total number of allocated JOIN_TAB objects
189 - "primary_tables" gives the number of input tables, including
190 materialized temporary tables from semi-join operation.
191 - "const_tables" are those tables among primary_tables that are detected
192 to be constant.
193 - "tmp_tables" is 0, 1 or 2 (more if windows) and counts the maximum
194 possible number of intermediate tables in post-processing (ie sorting and
195 duplicate removal).
196 Later, tmp_tables will be adjusted to the correct number of
197 intermediate tables, @see JOIN::make_tmp_tables_info.
198 - The remaining tables (ie. tables - primary_tables - tmp_tables) are
199 input tables to materialized semi-join operations.
200 The tables are ordered as follows in the join_tab array:
201 1. const primary table
202 2. non-const primary tables
203 3. intermediate sort/group tables
204 4. possible holes in array
205 5. semi-joined tables used with materialization strategy
206 */
207 uint tables{0}; ///< Total number of tables in query block
208 uint primary_tables{0}; ///< Number of primary input tables in query block
209 uint const_tables{0}; ///< Number of primary tables deemed constant
210 uint tmp_tables{0}; ///< Number of temporary tables used by query
212 /**
213 Indicates that the data will be aggregated (typically GROUP BY),
214 _and_ that it is already processed in an order that is compatible with
215 the grouping in use (e.g. because we are scanning along an index,
216 or because an earlier step sorted the data in a group-compatible order).
217
218 Note that this flag changes value at multiple points during optimization;
219 if it's set when a temporary table is created, this means we aggregate
220 into said temporary table (end_write_group is chosen instead of end_write),
221 but if it's set later, it means that we can aggregate as we go,
222 just before sending the data to the client (end_send_group is chosen
223 instead of end_send).
224
225 @see make_group_fields, alloc_group_fields, JOIN::exec
226 */
228 /// If query contains GROUP BY clause
230 /// If true, send produced rows using query_result
231 bool do_send_rows{true};
232 /// Set of tables contained in query
234 table_map const_table_map; ///< Set of tables found to be const
235 /**
236 Const tables which are either:
237 - not empty
238 - empty but inner to a LEFT JOIN, thus "considered" not empty for the
239 rest of execution (a NULL-complemented row will be used).
240 */
242 /**
243 This is the bitmap of all tables which are dependencies of
244 lateral derived tables which are not (yet) part of the partial
245 plan. (The value is a logical 'or' of zero or more
246 TABLE_LIST.map() values.)
247
248 When we are building the join order, there is a partial plan (an
249 ordered sequence of JOIN_TABs), and an unordered set of JOIN_TABs
250 not yet added to the plan. Due to backtracking, the partial plan
251 may both grow and shrink. When we add a new table to the plan, we
252 may wish to set up join buffering, so that rows from the preceding
253 table are buffered. If any of the remaining tables are derived
254 tables that depends on any of the predecessors of the table we
255 are adding (i.e. a lateral dependency), join buffering would be
256 inefficient. (@see setup_join_buffering() for a detailed
257 explanation of why this is so.)
258
259 For this reason we need to maintain this table_map of lateral
260 dependencies of tables not yet in the plan. Whenever we add a new
261 table to the plan, we update the map by calling
262 Optimize_table_order::recalculate_lateral_deps_incrementally().
263 And when we remove a table, we restore the previous map value
264 using a Tabel_map_restorer object.
265
266 As an example, assume that we join four tables, t1, t2, t3 and
267 d1, where d1 is a derived table that depends on t1:
268
269 SELECT * FROM t1 JOIN t2 ON t1.a=t2.b JOIN t3 ON t2.c=t3.d
270 JOIN LATERAL (SELECT DISTINCT e AS x FROM t4 WHERE t4.f=t1.c)
271 AS d1 ON t3.e=d1.x;
272
273 Now, if our partial plan is t1->t2, the map (of lateral
274 dependencies of the remaining tables) will contain t1.
275 This tells us that we should not use join buffering when joining t1
276 with t2. But if the partial plan is t1->d2->t2, the map will be
277 empty. We may thus use join buffering when joining d2 with t2.
278 */
280
281 /* Number of records produced after join + group operation */
286 // m_select_limit is used to decide if we are likely to scan the whole table.
288 /**
289 Used to fetch no more than given amount of rows per one
290 fetch operation of server side cursor.
291 The value is checked in end_send and end_send_group in fashion, similar
292 to offset_limit_cnt:
293 - fetch_limit= HA_POS_ERROR if there is no cursor.
294 - when we open a cursor, we set fetch_limit to 0,
295 - on each fetch iteration we add num_rows to fetch to fetch_limit
296 */
298
299 /**
300 This is the result of join optimization.
301
302 @note This is a scratch array, not used after get_best_combination().
303 */
305
306 /******* Join optimization state members start *******/
307
308 /* Current join optimization state */
310
311 /* We also maintain a stack of join optimization states in * join->positions[]
312 */
313 /******* Join optimization state members end *******/
314
315 /// A hook that secondary storage engines can use to override the executor
316 /// completely.
319
320 /**
321 The cost of best complete join plan found so far during optimization,
322 after optimization phase - cost of picked join order (not taking into
323 account the changes made by test_if_skip_sort_order()).
324 */
325 double best_read{0.0};
326 /**
327 The estimated row count of the plan with best read time (see above).
328 */
330 /// Expected cost of filesort.
331 double sort_cost{0.0};
332 /// Expected cost of windowing;
333 double windowing_cost{0.0};
337
338 // For destroying fields otherwise owned by RemoveDuplicatesIterator.
340
341 Item_sum **sum_funcs{nullptr};
342 /**
343 Describes a temporary table.
344 Each tmp table has its own tmp_table_param.
345 The one here is transiently used as a model by create_intermediate_table(),
346 to build the tmp table's own tmp_table_param.
347 */
350
351 enum class RollupState { NONE, INITED, READY };
353 bool implicit_grouping; ///< True if aggregated but no GROUP BY
354
355 /**
356 At construction time, set if SELECT DISTINCT. May be reset to false
357 later, when we set up a temporary table operation that deduplicates for us.
358 */
360
361 /**
362 If we have the GROUP BY statement in the query,
363 but the group_list was emptied by optimizer, this
364 flag is true.
365 It happens when fields in the GROUP BY are from
366 constant table
367 */
369
370 /*
371 simple_xxxxx is set if ORDER/GROUP BY doesn't include any references
372 to other tables than the first non-constant table in the JOIN.
373 It's also set if ORDER/GROUP BY is empty.
374 Used for deciding for or against using a temporary table to compute
375 GROUP/ORDER BY.
376 */
377 bool simple_order{false};
378 bool simple_group{false};
379
380 /*
381 m_ordered_index_usage is set if an ordered index access
382 should be used instead of a filesort when computing
383 ORDER/GROUP BY.
384 */
385 enum {
386 ORDERED_INDEX_VOID, // No ordered index avail.
387 ORDERED_INDEX_GROUP_BY, // Use index for GROUP BY
388 ORDERED_INDEX_ORDER_BY // Use index for ORDER BY
389 } m_ordered_index_usage{ORDERED_INDEX_VOID};
390
391 /**
392 Is set if we have a GROUP BY and we have ORDER BY on a constant or when
393 sorting isn't required.
394 */
395 bool skip_sort_order{false};
396
397 /**
398 If true we need a temporary table on the result set before any
399 windowing steps, e.g. for DISTINCT or we have a query ORDER BY.
400 See details in JOIN::optimize
401 */
403
404 /// If JOIN has lateral derived tables (is set at start of planning)
405 bool has_lateral{false};
406
407 /// Used and updated by JOIN::make_join_plan() and optimize_keyuse()
409
410 /**
411 Array of pointers to lists of expressions.
412 Each list represents the SELECT list at a certain stage of execution,
413 and also contains necessary extras: expressions added for ORDER BY,
414 GROUP BY, window clauses, underlying items of split items.
415 This array is only used when the query makes use of tmp tables: after
416 writing to tmp table (e.g. for GROUP BY), if this write also does a
417 function's calculation (e.g. of SUM), after the write the function's value
418 is in a column of the tmp table. If a SELECT list expression is the SUM,
419 and we now want to read that materialized SUM and send it forward, a new
420 expression (Item_field type instead of Item_sum), is needed. The new
421 expressions are listed in JOIN::tmp_fields_list[x]; 'x' is a number
422 (REF_SLICE_).
423 @see JOIN::make_tmp_tables_info()
424 */
426
427 int error{0}; ///< set in optimize(), exec(), prepare_result()
428
429 /**
430 Incremented each time clear_hash_tables() is run, signaling to
431 HashJoinIterators that they cannot keep their hash tables anymore
432 (since outer references may have changed).
433 */
435
436 /**
437 ORDER BY and GROUP BY lists, to transform with prepare,optimize and exec
438 */
440
441 // Used so that AggregateIterator knows which items to signal when the rollup
442 // level changes. Obviously only used in the presence of rollup.
447
448 /**
449 Any window definitions
450 */
452
453 /**
454 True if a window requires a certain order of rows, which implies that any
455 order of rows coming out of the pre-window join will be disturbed.
456 */
457 bool m_windows_sort{false};
458
459 /// If we have set up tmp tables for windowing, @see make_tmp_tables_info
460 bool m_windowing_steps{false};
461
462 /**
463 Buffer to gather GROUP BY, ORDER BY and DISTINCT QEP details for EXPLAIN
464 */
466
467 /**
468 JOIN::having_cond is initially equal to query_block->having_cond, but may
469 later be changed by optimizations performed by JOIN.
470 The relationship between the JOIN::having_cond condition and the
471 associated variable query_block->having_value is so that
472 having_value can be:
473 - COND_UNDEF if a having clause was not specified in the query or
474 if it has not been optimized yet
475 - COND_TRUE if the having clause is always true, in which case
476 JOIN::having_cond is set to NULL.
477 - COND_FALSE if the having clause is impossible, in which case
478 JOIN::having_cond is set to NULL
479 - COND_OK otherwise, meaning that the having clause needs to be
480 further evaluated
481 All of the above also applies to the where_cond/query_block->cond_value
482 pair.
483 */
484 /**
485 Optimized WHERE clause item tree (valid for one single execution).
486 Used in JOIN execution if no tables. Otherwise, attached in pieces to
487 JOIN_TABs and then not used in JOIN execution.
488 Printed by EXPLAIN EXTENDED.
489 Initialized by Query_block::get_optimizable_conditions().
490 */
492 /**
493 Optimized HAVING clause item tree (valid for one single execution).
494 Used in JOIN execution, as last "row filtering" step. With one exception:
495 may be pushed to the JOIN_TABs of temporary tables used in DISTINCT /
496 GROUP BY (see JOIN::make_tmp_tables_info()); in that case having_cond is
497 set to NULL, but is first saved to having_for_explain so that EXPLAIN
498 EXTENDED can still print it.
499 Initialized by Query_block::get_optimizable_conditions().
500 */
502 Item *having_for_explain; ///< Saved optimized HAVING for EXPLAIN
503 /**
504 Pointer set to query_block->get_table_list() at the start of
505 optimization. May be changed (to NULL) only if optimize_aggregated_query()
506 optimizes tables away.
507 */
510 /*
511 Join tab to return to. Points to an element of join->join_tab array, or to
512 join->join_tab[-1].
513 This is used at execution stage to shortcut join enumeration. Currently
514 shortcutting is done to handle outer joins or handle semi-joins with
515 FirstMatch strategy.
516 */
518
519 /**
520 ref_items is an array of 4+ slices, each containing an array of Item
521 pointers. ref_items is used in different phases of query execution.
522 - slice 0 is initially the same as Query_block::base_ref_items, ie it is
523 the set of items referencing fields from base tables. During optimization
524 and execution it may be temporarily overwritten by slice 1-3.
525 - slice 1 is a representation of the used items when being read from
526 the first temporary table.
527 - slice 2 is a representation of the used items when being read from
528 the second temporary table.
529 - slice 3 is a copy of the original slice 0. It is created if
530 slice overwriting is necessary, and it is used to restore
531 original values in slice 0 after having been overwritten.
532 - slices 4 -> N are used by windowing: all the window's out tmp tables,
533
534 Two windows: 4: window 1's out table
535 5: window 2's out table
536
537 and so on.
538
539 Slice 0 is allocated for the lifetime of a statement, whereas slices 1-3
540 are associated with a single optimization. The size of slice 0 determines
541 the slice size used when allocating the other slices.
542 */
544 nullptr}; // cardinality: REF_SLICE_SAVED_BASE + 1 + #windows*2
545
546 /**
547 The slice currently stored in ref_items[0].
548 Used to restore the base ref_items slice from the "save" slice after it
549 has been overwritten by another slice (1-3).
550 */
552
553 /**
554 Used only if this query block is recursive. Contains count of
555 all executions of this recursive query block, since the last
556 this->reset().
557 */
559
560 /**
561 <> NULL if optimization has determined that execution will produce an
562 empty result before aggregation, contains a textual explanation on why
563 result is empty. Implicitly grouped queries may still produce an
564 aggregation row.
565 @todo - suggest to set to "Preparation determined that query is empty"
566 when Query_block::is_empty_query() is true.
567 */
568 const char *zero_result_cause{nullptr};
569
570 /**
571 True if, at this stage of processing, subquery materialization is allowed
572 for children subqueries of this JOIN (those in the SELECT list, in WHERE,
573 etc). If false, and we have to evaluate a subquery at this stage, then we
574 must choose EXISTS.
575 */
577 /**
578 True if plan search is allowed to use references to expressions outer to
579 this JOIN (for example may set up a 'ref' access looking up an outer
580 expression in the index, etc).
581 */
582 bool allow_outer_refs{false};
583
584 /* Temporary tables used to weed-out semi-join duplicates */
587 /* end of allocation caching storage */
588
589 /** Exec time only: true <=> current group has been sent */
590 bool group_sent{false};
591 /// If true, calculate found rows for this query block
592 bool calc_found_rows{false};
593
594 /**
595 This will force tmp table to NOT use index + update for group
596 operation as it'll cause [de]serialization for each json aggregated
597 value and is very ineffective (times worse).
598 Server should use filesort, or tmp table + filesort to resolve GROUP BY
599 with JSON aggregate functions.
600 */
602
603 /// True if plan is const, ie it will return zero or one rows.
604 bool plan_is_const() const { return const_tables == primary_tables; }
605
606 /**
607 True if plan contains one non-const primary table (ie not including
608 tables taking part in semi-join materialization).
609 */
611
612 bool optimize(bool finalize_access_paths);
613 void reset();
614 bool prepare_result();
615 void destroy();
616 bool alloc_func_list();
618 bool before_group_by, bool recompute = false);
619
620 /**
621 Overwrites one slice of ref_items with the contents of another slice.
622 In the normal case, dst and src have the same size().
623 However: the rollup slices may have smaller size than slice_sz.
624 */
625 void copy_ref_item_slice(uint dst_slice, uint src_slice) {
626 copy_ref_item_slice(ref_items[dst_slice], ref_items[src_slice]);
627 }
629 assert(dst_arr.size() >= src_arr.size());
630 void *dest = dst_arr.array();
631 const void *src = src_arr.array();
632 if (!src_arr.is_null())
633 memcpy(dest, src, src_arr.size() * src_arr.element_size());
634 }
635
636 /**
637 Allocate a ref_item slice, assume that slice size is in ref_items[0]
638
639 @param thd_arg thread handler
640 @param sliceno The slice number to allocate in JOIN::ref_items
641
642 @returns false if success, true if error
643 */
644 bool alloc_ref_item_slice(THD *thd_arg, int sliceno);
645
646 /**
647 Overwrite the base slice of ref_items with the slice supplied as argument.
648
649 @param sliceno number to overwrite the base slice with, must be 1-4 or
650 4 + windowno.
651 */
652 void set_ref_item_slice(uint sliceno) {
653 assert((int)sliceno >= 1);
654 if (current_ref_item_slice != sliceno) {
656 DBUG_PRINT("info", ("JOIN %p ref slice %u -> %u", this,
657 current_ref_item_slice, sliceno));
658 current_ref_item_slice = sliceno;
659 }
660 }
661
662 /// @note do also consider Switch_ref_item_slice
664
665 /**
666 Returns the clone of fields_list which is appropriate for evaluating
667 expressions at the current stage of execution; which stage is denoted by
668 the value of current_ref_item_slice.
669 */
671
672 bool optimize_rollup();
674 /**
675 Release memory and, if possible, the open tables held by this execution
676 plan (and nested plans). It's used to release some tables before
677 the end of execution in order to increase concurrency and reduce
678 memory consumption.
679 */
680 void join_free();
681 /** Cleanup this JOIN. Not a full cleanup. reusable? */
682 void cleanup();
683
684 bool clear_fields(table_map *save_nullinfo);
685 void restore_fields(table_map save_nullinfo);
686
687 private:
688 /**
689 Return whether the caller should send a row even if the join
690 produced no rows if:
691 - there is an aggregate function (sum_func_count!=0), and
692 - the query is not grouped, and
693 - a possible HAVING clause evaluates to TRUE.
694
695 @note: if there is a having clause, it must be evaluated before
696 returning the row.
697 */
702 }
703
704 public:
708 bool attach_join_conditions(plan_idx last_tab);
709
710 private:
711 bool attach_join_condition_to_nest(plan_idx first_inner, plan_idx last_tab,
712 Item *join_cond, bool is_sj_mat_cond);
713
714 public:
717 bool sort_before_group);
721 table_map plan_tables, uint idx) const;
722 bool clear_sj_tmp_tables();
725
726 void mark_const_table(JOIN_TAB *table, Key_use *key);
727 /// State of execution plan. Currently used only for EXPLAIN
729 NO_PLAN, ///< No plan is ready yet
730 ZERO_RESULT, ///< Zero result cause is set
731 NO_TABLES, ///< Plan has no tables
732 PLAN_READY ///< Plan is ready
733 };
734 /// See enum_plan_state
736 bool is_optimized() const { return optimized; }
737 void set_optimized() { optimized = true; }
738 bool is_executed() const { return executed; }
739 void set_executed() { executed = true; }
740
741 /**
742 Retrieve the cost model object to be used for this join.
743
744 @return Cost model object for the join
745 */
746
747 const Cost_model_server *cost_model() const;
748
749 /**
750 Check if FTS index only access is possible
751 */
752 bool fts_index_access(JOIN_TAB *tab);
753
755 /**
756 Propagate dependencies between tables due to outer join relations.
757
758 @returns false if success, true if error
759 */
761
762 /**
763 Handle offloading of query parts to the underlying engines, when
764 such is supported by their implementation.
765
766 @returns false if success, true if error
767 */
768 bool push_to_engines();
769
772
773 /**
774 If this query block was planned twice, once with and once without conditions
775 added by in2exists, changes the root access path to the one without
776 in2exists. If not (ie., there were never any such conditions in the first
777 place), does nothing.
778 */
780
781 /**
782 In the case of rollup (only): After the base slice list was made, we may
783 have modified the field list to add rollup group items and sum switchers,
784 but there may be Items with refs that refer to the base slice. This function
785 refreshes the base slice (and its copy, REF_SLICE_SAVED_BASE) with a fresh
786 copy of the list from “fields”.
787
788 When we get rid of slices entirely, we can get rid of this, too.
789 */
790 void refresh_base_slice();
791
792 /**
793 Whether this query block needs finalization (see
794 FinalizePlanForQueryBlock()) before it can be actually used.
795 This only happens when using the hypergraph join optimizer.
796 */
797 bool needs_finalize{false};
798
799 private:
800 bool optimized{false}; ///< flag to avoid double optimization in EXPLAIN
801
802 /**
803 Set by exec(), reset by reset(). Note that this needs to be set
804 _during_ the query (not only when it's done executing), or the
805 dynamic range optimizer will not understand which tables have been
806 read.
807 */
808 bool executed{false};
809
810 /// Final execution plan state. Currently used only for EXPLAIN
812
813 public:
814 /*
815 When join->select_count is set, tables will not be optimized away.
816 The call to records() will be delayed until the execution phase and
817 the counting will be done on an index of Optimizer's choice.
818 The index will be decided in find_shortest_key(), called from
819 optimize_aggregated_query().
820 */
821 bool select_count{false};
822
823 private:
824 /**
825 Create a temporary table to be used for processing DISTINCT/ORDER
826 BY/GROUP BY.
827
828 @note Will modify JOIN object wrt sort/group attributes
829
830 @param tab the JOIN_TAB object to attach created table to
831 @param tmp_table_fields List of items that will be used to define
832 column types of the table.
833 @param tmp_table_group Group key to use for temporary table, empty if none.
834 @param save_sum_fields If true, do not replace Item_sum items in
835 @c tmp_fields list with Item_field items referring
836 to fields in temporary table.
837
838 @returns false on success, true on failure
839 */
841 const mem_root_deque<Item *> &tmp_table_fields,
842 ORDER_with_src &tmp_table_group,
843 bool save_sum_fields);
844
845 /**
846 Optimize distinct when used on a subset of the tables.
847
848 E.g.,: SELECT DISTINCT t1.a FROM t1,t2 WHERE t1.b=t2.b
849 In this case we can stop scanning t2 when we have found one t1.a
850 */
851 void optimize_distinct();
852
853 /**
854 Function sets FT hints, initializes FT handlers and
855 checks if FT index can be used as covered.
856 */
857 bool optimize_fts_query();
858
860 /**
861 Initialize key dependencies for join tables.
862
863 TODO figure out necessity of this method. Current test
864 suite passed without this initialization.
865 */
867 JOIN_TAB *const tab_end = join_tab + tables;
868 for (JOIN_TAB *tab = join_tab; tab < tab_end; tab++)
869 tab->key_dependent = tab->dependent;
870 }
871
872 private:
873 void set_prefix_tables();
874 void cleanup_item_list(const mem_root_deque<Item *> &items) const;
876 bool make_join_plan();
877 bool init_planner_arrays();
881 bool estimate_rowcount();
882 void optimize_keyuse();
883 void set_semijoin_info();
884 /**
885 An utility function - apply heuristics and optimize access methods to tables.
886 @note Side effect - this function could set 'Impossible WHERE' zero
887 result.
888 */
890 void update_depend_map();
892 /**
893 Fill in outer join related info for the execution plan structure.
894
895 For each outer join operation left after simplification of the
896 original query the function set up the following pointers in the linear
897 structure join->join_tab representing the selected execution plan.
898 The first inner table t0 for the operation is set to refer to the last
899 inner table tk through the field t0->last_inner.
900 Any inner table ti for the operation are set to refer to the first
901 inner table ti->first_inner.
902 The first inner table t0 for the operation is set to refer to the
903 first inner table of the embedding outer join operation, if there is any,
904 through the field t0->first_upper.
905 The on expression for the outer join operation is attached to the
906 corresponding first inner table through the field t0->on_expr_ref.
907 Here ti are structures of the JOIN_TAB type.
908
909 EXAMPLE. For the query:
910 @code
911 SELECT * FROM t1
912 LEFT JOIN
913 (t2, t3 LEFT JOIN t4 ON t3.a=t4.a)
914 ON (t1.a=t2.a AND t1.b=t3.b)
915 WHERE t1.c > 5,
916 @endcode
917
918 given the execution plan with the table order t1,t2,t3,t4
919 is selected, the following references will be set;
920 t4->last_inner=[t4], t4->first_inner=[t4], t4->first_upper=[t2]
921 t2->last_inner=[t4], t2->first_inner=t3->first_inner=[t2],
922 on expression (t1.a=t2.a AND t1.b=t3.b) will be attached to
923 *t2->on_expr_ref, while t3.a=t4.a will be attached to *t4->on_expr_ref.
924
925 @note
926 The function assumes that the simplification procedure has been
927 already applied to the join query (see simplify_joins).
928 This function can be called only after the execution plan
929 has been chosen.
930 */
931 void make_outerjoin_info();
932
933 /**
934 Initialize ref access for all tables that use it.
935
936 @return False if success, True if error
937
938 @note We cannot setup fields used for ref access before we have sorted
939 the items within multiple equalities according to the final order of
940 the tables involved in the join operation. Currently, this occurs in
941 @see substitute_for_best_equal_field().
942 */
943 bool init_ref_access();
944 bool alloc_qep(uint n);
945 void unplug_join_tabs();
947 POSITION *inner_pos,
948 POSITION *sjm_pos);
949
950 bool add_having_as_tmp_table_cond(uint curr_tmp_table);
952 void set_plan_state(enum_plan_state plan_state_arg);
954 ORDER *remove_const(ORDER *first_order, Item *cond, bool change_list,
955 bool *simple_order, bool group_by);
956
957 /**
958 Check whether this is a subquery that can be evaluated by index look-ups.
959 If so, change subquery engine to subselect_indexsubquery_engine.
960
961 @retval 1 engine was changed
962 @retval 0 engine wasn't changed
963 @retval -1 OOM or other error
964 */
966
967 /**
968 Optimize DISTINCT, GROUP BY, ORDER BY clauses
969
970 @retval false ok
971 @retval true an error occurred
972 */
974
975 /**
976 Test if an index could be used to replace filesort for ORDER BY/GROUP BY
977
978 @details
979 Investigate whether we may use an ordered index as part of either
980 DISTINCT, GROUP BY or ORDER BY execution. An ordered index may be
981 used for only the first of any of these terms to be executed. This
982 is reflected in the order which we check for test_if_skip_sort_order()
983 below. However we do not check for DISTINCT here, as it would have
984 been transformed to a GROUP BY at this stage if it is a candidate for
985 ordered index optimization.
986 If a decision was made to use an ordered index, the availability
987 if such an access path is stored in 'm_ordered_index_usage' for later
988 use by 'execute' or 'explain'
989 */
990 void test_skip_sort();
991
993
994 /**
995 Convert the executor structures to a set of access paths, storing
996 the result in m_root_access_path.
997 */
998 void create_access_paths();
999
1000 public:
1001 /**
1002 Create access paths with the knowledge that there are going to be zero rows
1003 coming from tables (before aggregation); typically because we know that
1004 all of them would be filtered away by WHERE (e.g. SELECT * FROM t1
1005 WHERE 1=2). This will normally yield no output rows, but if we have implicit
1006 aggregation, it might yield a single one.
1007 */
1009
1010 private:
1012
1013 /** @{ Helpers for create_access_paths. */
1017 /** @} */
1018
1019 /**
1020 An access path you can read from to get all records for this query
1021 (after you create an iterator from it).
1022 */
1024
1025 /**
1026 If this query block contains conditions synthesized during IN-to-EXISTS
1027 conversion: A second query plan with all such conditions removed.
1028 See comments in JOIN::optimize().
1029 */
1031};
1032
1033/**
1034 Use this in a function which depends on best_ref listing tables in the
1035 final join order. If 'tables==0', one is not expected to consult best_ref
1036 cells, and best_ref may not even have been allocated.
1037*/
1038#define ASSERT_BEST_REF_IN_JOIN_ORDER(join) \
1039 do { \
1040 assert((join)->tables == 0 || ((join)->best_ref && !(join)->join_tab)); \
1041 } while (0)
1042
1043/**
1044 RAII class to ease the temporary switching to a different slice of
1045 the ref item array.
1046*/
1050
1051 public:
1053 : join(join_arg), saved(join->get_ref_item_slice()) {
1054 if (!join->ref_items[new_v].is_null()) join->set_ref_item_slice(new_v);
1055 }
1057};
1058
1059bool uses_index_fields_only(Item *item, TABLE *tbl, uint keyno,
1060 bool other_tbls_ok);
1061bool remove_eq_conds(THD *thd, Item *cond, Item **retcond,
1062 Item::cond_result *cond_value);
1063bool optimize_cond(THD *thd, Item **conds, COND_EQUAL **cond_equal,
1065 Item::cond_result *cond_value);
1067 COND_EQUAL *cond_equal,
1068 JOIN_TAB **table_join_idx);
1069bool build_equal_items(THD *thd, Item *cond, Item **retcond,
1070 COND_EQUAL *inherited, bool do_inherit,
1072 COND_EQUAL **cond_equal_ref);
1076 THD *thd, uint keyparts, Item_field **fields,
1077 const mem_root_deque<Item *> &outer_exprs);
1078Item_field *get_best_field(Item_field *item_field, COND_EQUAL *cond_equal);
1079Item *make_cond_for_table(THD *thd, Item *cond, table_map tables,
1080 table_map used_table, bool exclude_expensive_cond);
1082 uint first_unused);
1083
1084/**
1085 Create an order list that consists of all non-const fields and items.
1086 This is usable for e.g. converting DISTINCT into GROUP or ORDER BY.
1087 Is ref_item_array is non-null (is_null() returns false), the items
1088 will point into the slice given by it. Otherwise, it points directly
1089 into *fields (this is the only reason why fields is not const).
1090
1091 Try to put the items in "order_list" first, to allow one to optimize away
1092 a later ORDER BY.
1093 */
1095 ORDER *order_list,
1096 mem_root_deque<Item *> *fields,
1097 bool skip_aggregates,
1098 bool convert_bit_fields_to_long,
1099 bool *all_order_by_fields_used);
1100
1101/**
1102 Returns true if arguments are a temporal Field having no date,
1103 part and a temporal expression having a date part.
1104 @param f Field
1105 @param v Expression
1106 */
1107inline bool field_time_cmp_date(const Field *f, const Item *v) {
1108 const enum_field_types ft = f->type();
1109 return is_temporal_type(ft) && !is_temporal_type_with_date(ft) &&
1111}
1112
1113bool substitute_gc(THD *thd, Query_block *query_block, Item *where_cond,
1114 ORDER *group_list, ORDER *order);
1115
1116/**
1117 This class restores a table_map object to its original value
1118 when '*this' is destroyed.
1119 */
1121 /** The location to be restored.*/
1123 /** The original value to restore.*/
1125
1126 public:
1127 /**
1128 Constructor.
1129 @param map The table map that we wish to restore.
1130 */
1133
1134 // This class is not intended to be copied.
1137
1140 void assert_unchanged() const { assert(*m_location == m_saved_value); }
1141};
1142
1143/**
1144 Estimates how many times a subquery will be executed as part of a
1145 query execution. If it is a cacheable subquery, the estimate tells
1146 how many times the subquery will be executed if it is not cached.
1147
1148 @param[in] subquery the Item that represents the subquery
1149 @param[in,out] trace optimizer trace context
1150
1151 @return the number of times the subquery is expected to be executed
1152*/
1153double calculate_subquery_executions(const Item_subselect *subquery,
1154 Opt_trace_context *trace);
1155
1156extern const char *antijoin_null_cond;
1157
1158/**
1159 Checks if an Item, which is constant for execution, can be evaluated during
1160 optimization. It cannot be evaluated if it contains a subquery and the
1161 OPTION_NO_SUBQUERY_DURING_OPTIMIZATION query option is active.
1162
1163 @param item the Item to check
1164 @param select the query block that contains the Item
1165 @return false if this Item contains a subquery and subqueries cannot be
1166 evaluated during optimization, or true otherwise
1167*/
1168bool evaluate_during_optimization(const Item *item, const Query_block *select);
1169
1170/**
1171 Find the multiple equality predicate containing a field.
1172
1173 The function retrieves the multiple equalities accessed through
1174 the cond_equal structure from current level and up looking for
1175 an equality containing a field. It stops retrieval as soon as the equality
1176 is found and set up inherited_fl to true if it's found on upper levels.
1177
1178 @param cond_equal multiple equalities to search in
1179 @param item_field field to look for
1180 @param[out] inherited_fl set up to true if multiple equality is found
1181 on upper levels (not on current level of
1182 cond_equal)
1183
1184 @return
1185 - Item_equal for the found multiple equality predicate if a success;
1186 - nullptr otherwise.
1187*/
1189 const Item_field *item_field, bool *inherited_fl);
1190
1191/**
1192 Find an artificial cap for ref access. This is mostly a crutch to mitigate
1193 that we don't estimate the cache effects of ref accesses properly
1194 (ie., normally, if we do many, they will hit cache instead of being
1195 separate seeks). Given to find_cost_for_ref().
1196 */
1197double find_worst_seeks(const TABLE *table, double num_rows,
1198 double table_scan_cost);
1199
1200/**
1201 Whether a ref lookup of “right_item” on “field” will give an exact
1202 comparison in all cases, ie., one can remove any further checks on
1203 field = right_item. If not, there may be false positives, and one
1204 needs to keep the comparison after the ref lookup.
1205 */
1206bool ref_lookup_subsumes_comparison(Field *field, Item *right_item);
1207
1208/**
1209 Checks if we need to create iterators for this query. We usually have to. The
1210 exception is if a secondary engine is used, and that engine will offload the
1211 query execution to an external executor using #JOIN::override_executor_func.
1212 In this case, the external executor will use its own execution structures and
1213 we don't need to bother with creating the iterators needed by the MySQL
1214 executor.
1215 */
1216bool IteratorsAreNeeded(const THD *thd, AccessPath *root_path);
1217
1218#endif /* SQL_OPTIMIZER_INCLUDED */
bool is_null() const
Definition: sql_array.h:134
Element_type * array() const
Definition: sql_array.h:142
size_t size() const
Definition: sql_array.h:131
size_t element_size() const
Definition: sql_array.h:130
Definition: item_cmpfunc.h:2699
API for getting cost estimates for server operations that are not directly related to a table object.
Definition: opt_costmodel.h:51
Definition: opt_explain_format.h:448
Definition: field.h:574
virtual enum_field_types type() const =0
Definition: item_cmpfunc.h:2562
Definition: item.h:4033
Definition: item_subselect.h:79
Class Item_sum is the base class used for special expressions that SQL calls 'set functions'.
Definition: item_sum.h:398
Base class that is used to represent any kind of expression in a relational query.
Definition: item.h:802
bool is_temporal_with_date() const
Definition: item.h:3008
cond_result
Definition: item.h:871
@ COND_FALSE
Definition: item.h:871
Query optimization plan node.
Definition: sql_select.h:598
Definition: sql_optimizer.h:125
const Cost_model_server * cost_model() const
Retrieve the cost model object to be used for this join.
Definition: sql_optimizer.cc:11154
bool skip_sort_order
Is set if we have a GROUP BY and we have ORDER BY on a constant or when sorting isn't required.
Definition: sql_optimizer.h:395
bool attach_join_condition_to_nest(plan_idx first_inner, plan_idx last_tab, Item *join_cond, bool is_sj_mat_cond)
Helper for JOIN::attach_join_conditions().
Definition: sql_optimizer.cc:8502
void set_root_access_path(AccessPath *path)
Definition: sql_optimizer.h:771
bool calc_found_rows
If true, calculate found rows for this query block.
Definition: sql_optimizer.h:592
bool plan_is_single_table()
True if plan contains one non-const primary table (ie not including tables taking part in semi-join m...
Definition: sql_optimizer.h:610
void mark_const_table(JOIN_TAB *table, Key_use *key)
Move const tables first in the position array.
Definition: sql_optimizer.cc:8333
JOIN_TAB * join_tab
Optimal query execution plan.
Definition: sql_optimizer.h:146
ha_rows fetch_limit
Used to fetch no more than given amount of rows per one fetch operation of server side cursor.
Definition: sql_optimizer.h:297
Item_sum ** sum_funcs
Definition: sql_optimizer.h:341
List< Cached_item > group_fields
Definition: sql_optimizer.h:335
bool m_windows_sort
True if a window requires a certain order of rows, which implies that any order of rows coming out of...
Definition: sql_optimizer.h:457
MYSQL_LOCK * lock
Definition: sql_optimizer.h:349
bool executed
Set by exec(), reset by reset().
Definition: sql_optimizer.h:808
QEP_TAB * qep_tab
Array of QEP_TABs.
Definition: sql_optimizer.h:148
bool send_row_on_empty_set() const
Return whether the caller should send a row even if the join produced no rows if:
Definition: sql_optimizer.h:698
ha_rows found_records
Definition: sql_optimizer.h:283
uint recursive_iteration_count
Used only if this query block is recursive.
Definition: sql_optimizer.h:558
void copy_ref_item_slice(Ref_item_array dst_arr, Ref_item_array src_arr)
Definition: sql_optimizer.h:628
@ ORDERED_INDEX_GROUP_BY
Definition: sql_optimizer.h:387
@ ORDERED_INDEX_VOID
Definition: sql_optimizer.h:386
@ ORDERED_INDEX_ORDER_BY
Definition: sql_optimizer.h:388
bool child_subquery_can_materialize
True if, at this stage of processing, subquery materialization is allowed for children subqueries of ...
Definition: sql_optimizer.h:576
Prealloced_array< Item_rollup_group_item *, 4 > rollup_group_items
Definition: sql_optimizer.h:443
COND_EQUAL * cond_equal
Definition: sql_optimizer.h:509
JOIN_TAB ** map2table
mapping between table indexes and JOIN_TABs
Definition: sql_optimizer.h:158
ha_rows m_select_limit
Definition: sql_optimizer.h:287
POSITION * positions
Definition: sql_optimizer.h:309
uint current_ref_item_slice
The slice currently stored in ref_items[0].
Definition: sql_optimizer.h:551
bool is_executed() const
Definition: sql_optimizer.h:738
uint tables
Before plan has been created, "tables" denote number of input tables in the query block and "primary_...
Definition: sql_optimizer.h:207
bool has_lateral
If JOIN has lateral derived tables (is set at start of planning)
Definition: sql_optimizer.h:405
bool need_tmp_before_win
If true we need a temporary table on the result set before any windowing steps, e....
Definition: sql_optimizer.h:402
Prealloced_array< Item_rollup_sum_switcher *, 4 > rollup_sums
Definition: sql_optimizer.h:445
uint tmp_tables
Number of temporary tables used by query.
Definition: sql_optimizer.h:210
int error
set in optimize(), exec(), prepare_result()
Definition: sql_optimizer.h:427
bool plan_is_const() const
True if plan is const, ie it will return zero or one rows.
Definition: sql_optimizer.h:604
table_map const_table_map
Set of tables found to be const.
Definition: sql_optimizer.h:234
Prealloced_array< TemporaryTableToCleanup, 1 > temp_tables
Definition: sql_optimizer.h:176
Query_block *const query_block
Query block that is optimized and executed using this JOIN.
Definition: sql_optimizer.h:137
bool select_distinct
At construction time, set if SELECT DISTINCT.
Definition: sql_optimizer.h:359
RollupState
Definition: sql_optimizer.h:351
List< TABLE > sj_tmp_tables
Definition: sql_optimizer.h:585
enum JOIN::@174 ORDERED_INDEX_VOID
table_map found_const_table_map
Const tables which are either:
Definition: sql_optimizer.h:241
bool simple_order
Definition: sql_optimizer.h:377
void set_executed()
Definition: sql_optimizer.h:739
List< Window > m_windows
Any window definitions.
Definition: sql_optimizer.h:451
Explain_format_flags explain_flags
Buffer to gather GROUP BY, ORDER BY and DISTINCT QEP details for EXPLAIN.
Definition: sql_optimizer.h:465
mem_root_deque< Item * > * tmp_fields
Array of pointers to lists of expressions.
Definition: sql_optimizer.h:425
uint const_tables
Number of primary tables deemed constant.
Definition: sql_optimizer.h:209
Prealloced_array< Filesort *, 1 > filesorts_to_cleanup
Definition: sql_optimizer.h:181
ha_rows examined_rows
Definition: sql_optimizer.h:284
ha_rows row_limit
Definition: sql_optimizer.h:285
bool allow_outer_refs
True if plan search is allowed to use references to expressions outer to this JOIN (for example may s...
Definition: sql_optimizer.h:582
JOIN_TAB ** best_ref
Array of plan operators representing the current (partial) best plan.
Definition: sql_optimizer.h:156
Item * having_for_explain
Saved optimized HAVING for EXPLAIN.
Definition: sql_optimizer.h:502
RollupState rollup_state
Definition: sql_optimizer.h:352
AccessPath * root_access_path() const
Definition: sql_optimizer.h:770
ha_rows send_records
Definition: sql_optimizer.h:282
Override_executor_func override_executor_func
Definition: sql_optimizer.h:318
plan_idx return_tab
Definition: sql_optimizer.h:517
enum_plan_state plan_state
Final execution plan state. Currently used only for EXPLAIN.
Definition: sql_optimizer.h:811
Item * having_cond
Optimized HAVING clause item tree (valid for one single execution).
Definition: sql_optimizer.h:501
void make_outerjoin_info()
Fill in outer join related info for the execution plan structure.
Definition: sql_optimizer.cc:8362
TABLE_LIST * tables_list
Pointer set to query_block->get_table_list() at the start of optimization.
Definition: sql_optimizer.h:508
mem_root_deque< Item * > * fields
Definition: sql_optimizer.h:334
Temp_table_param tmp_table_param
Describes a temporary table.
Definition: sql_optimizer.h:348
bool select_count
Definition: sql_optimizer.h:821
bool m_windowing_steps
If we have set up tmp tables for windowing,.
Definition: sql_optimizer.h:460
bool fts_index_access(JOIN_TAB *tab)
Check if FTS index only access is possible.
Definition: sql_optimizer.cc:10671
void optimize_keyuse()
Update some values in keyuse for faster choose_table_order() loop.
Definition: sql_optimizer.cc:10573
bool with_json_agg
This will force tmp table to NOT use index + update for group operation as it'll cause [de]serializat...
Definition: sql_optimizer.h:601
uint send_group_parts
Definition: sql_optimizer.h:211
bool finalize_table_conditions()
Remove redundant predicates and cache constant expressions.
Definition: sql_optimizer.cc:8964
AccessPath * m_root_access_path_no_in2exists
If this query block contains conditions synthesized during IN-to-EXISTS conversion: A second query pl...
Definition: sql_optimizer.h:1030
ORDER_with_src group_list
Definition: sql_optimizer.h:439
double sort_cost
Expected cost of filesort.
Definition: sql_optimizer.h:331
bool generate_derived_keys()
Add keys to derived tables'/views' result tables in a list.
Definition: sql_optimizer.cc:9041
bool optimize_fts_query()
Function sets FT hints, initializes FT handlers and checks if FT index can be used as covered.
Definition: sql_optimizer.cc:10612
enum_plan_state
State of execution plan. Currently used only for EXPLAIN.
Definition: sql_optimizer.h:728
@ NO_TABLES
Plan has no tables.
Definition: sql_optimizer.h:731
@ NO_PLAN
No plan is ready yet.
Definition: sql_optimizer.h:729
@ ZERO_RESULT
Zero result cause is set.
Definition: sql_optimizer.h:730
@ PLAN_READY
Plan is ready.
Definition: sql_optimizer.h:732
Key_use_array keyuse_array
Used and updated by JOIN::make_join_plan() and optimize_keyuse()
Definition: sql_optimizer.h:408
bool group_sent
Exec time only: true <=> current group has been sent.
Definition: sql_optimizer.h:590
bool needs_finalize
Whether this query block needs finalization (see FinalizePlanForQueryBlock()) before it can be actual...
Definition: sql_optimizer.h:797
void init_key_dependencies()
Initialize key dependencies for join tables.
Definition: sql_optimizer.h:866
void set_ref_item_slice(uint sliceno)
Overwrite the base slice of ref_items with the slice supplied as argument.
Definition: sql_optimizer.h:652
List< Cached_item > group_fields_cache
Definition: sql_optimizer.h:336
bool streaming_aggregation
Indicates that the data will be aggregated (typically GROUP BY), and that it is already processed in ...
Definition: sql_optimizer.h:227
void set_optimized()
Definition: sql_optimizer.h:737
uint primary_tables
Number of primary input tables in query block.
Definition: sql_optimizer.h:208
bool optimize_rollup()
Optimize rollup specification.
Definition: sql_optimizer.cc:11111
THD *const thd
Thread handler.
Definition: sql_optimizer.h:139
table_map all_table_map
Set of tables contained in query.
Definition: sql_optimizer.h:233
bool attach_join_conditions(plan_idx last_tab)
Attach outer join conditions to generated table conditions in an optimal way.
Definition: sql_optimizer.cc:8613
bool decide_subquery_strategy()
Decides between EXISTS and materialization; performs last steps to set up the chosen strategy.
Definition: sql_optimizer.cc:10825
List< Semijoin_mat_exec > sjm_exec_list
Definition: sql_optimizer.h:586
JOIN(const JOIN &rhs)=delete
TABLE * sort_by_table
Definition: sql_optimizer.h:164
Ref_item_array * ref_items
ref_items is an array of 4+ slices, each containing an array of Item pointers.
Definition: sql_optimizer.h:543
bool do_send_rows
If true, send produced rows using query_result.
Definition: sql_optimizer.h:231
double windowing_cost
Expected cost of windowing;.
Definition: sql_optimizer.h:333
enum_plan_state get_plan_state() const
See enum_plan_state.
Definition: sql_optimizer.h:735
JOIN & operator=(const JOIN &rhs)=delete
ORDER_with_src order
ORDER BY and GROUP BY lists, to transform with prepare,optimize and exec.
Definition: sql_optimizer.h:439
bool group_optimized_away
If we have the GROUP BY statement in the query, but the group_list was emptied by optimizer,...
Definition: sql_optimizer.h:368
double best_read
The cost of best complete join plan found so far during optimization, after optimization phase - cost...
Definition: sql_optimizer.h:325
ORDER * remove_const(ORDER *first_order, Item *cond, bool change_list, bool *simple_order, bool group_by)
Remove all constants and check if ORDER only contains simple expressions.
Definition: sql_optimizer.cc:9948
bool implicit_grouping
True if aggregated but no GROUP BY.
Definition: sql_optimizer.h:353
POSITION * best_positions
This is the result of join optimization.
Definition: sql_optimizer.h:304
void finalize_derived_keys()
For each materialized derived table/view, informs every TABLE of the key it will (not) use,...
Definition: sql_optimizer.cc:9061
bool optimized
flag to avoid double optimization in EXPLAIN
Definition: sql_optimizer.h:800
bool compare_costs_of_subquery_strategies(Subquery_strategy *method)
Tells what is the cheapest between IN->EXISTS and subquery materialization, in terms of cost,...
Definition: sql_optimizer.cc:10886
bool is_optimized() const
Definition: sql_optimizer.h:736
const char * zero_result_cause
<> NULL if optimization has determined that execution will produce an empty result before aggregation...
Definition: sql_optimizer.h:568
Query_expression * query_expression() const
Query expression referring this query block.
Definition: sql_optimizer.h:132
mem_root_deque< Item * > * get_current_fields()
Returns the clone of fields_list which is appropriate for evaluating expressions at the current stage...
Definition: sql_optimizer.cc:11148
bool(*)(JOIN *, Query_result *) Override_executor_func
A hook that secondary storage engines can use to override the executor completely.
Definition: sql_optimizer.h:317
void clear_hash_tables()
Definition: sql_optimizer.h:724
uint get_ref_item_slice() const
Definition: sql_optimizer.h:663
List< Cached_item > semijoin_deduplication_fields
Definition: sql_optimizer.h:339
bool grouped
If query contains GROUP BY clause.
Definition: sql_optimizer.h:229
void refine_best_rowcount()
Refine the best_rowcount estimation based on what happens after tables have been joined: LIMIT and ty...
Definition: sql_optimizer.cc:11122
AccessPath * m_root_access_path
An access path you can read from to get all records for this query (after you create an iterator from...
Definition: sql_optimizer.h:1023
ha_rows best_rowcount
The estimated row count of the plan with best read time (see above).
Definition: sql_optimizer.h:329
Item * where_cond
JOIN::having_cond is initially equal to query_block->having_cond, but may later be changed by optimiz...
Definition: sql_optimizer.h:491
bool simple_group
Definition: sql_optimizer.h:378
uint64_t hash_table_generation
Incremented each time clear_hash_tables() is run, signaling to HashJoinIterators that they cannot kee...
Definition: sql_optimizer.h:434
table_map deps_of_remaining_lateral_derived_tables
This is the bitmap of all tables which are dependencies of lateral derived tables which are not (yet)...
Definition: sql_optimizer.h:279
void copy_ref_item_slice(uint dst_slice, uint src_slice)
Overwrites one slice of ref_items with the contents of another slice.
Definition: sql_optimizer.h:625
A Key_use represents an equality predicate of the form (table.column = val), where the column is inde...
Definition: sql_select.h:173
Definition: sql_list.h:433
A typesafe replacement for DYNAMIC_ARRAY.
Definition: mem_root_array.h:425
Wrapper for ORDER* pointer to trace origins of ORDER list.
Definition: sql_optimizer.h:95
bool empty() const
Definition: sql_optimizer.h:111
int get_flags() const
Definition: sql_optimizer.h:119
void clean()
Definition: sql_optimizer.h:113
ORDER * order
ORDER expression that we are wrapping with this class.
Definition: sql_optimizer.h:97
ORDER_with_src()
Definition: sql_optimizer.h:104
Explain_sort_clause src
origin of order list
Definition: sql_optimizer.h:98
int flags
bitmap of Explain_sort_property
Definition: sql_optimizer.h:101
ORDER_with_src(ORDER *order_arg, Explain_sort_clause src_arg)
Definition: sql_optimizer.h:106
A per-session context which is always available at any point of execution, because in practice it's a...
Definition: opt_trace_context.h:89
A typesafe replacement for DYNAMIC_ARRAY.
Definition: prealloced_array.h:70
Definition: sql_executor.h:259
enum_op_type
Definition: sql_executor.h:406
This class represents a query block, aka a query specification, which is a query consisting of a SELE...
Definition: sql_lex.h:1159
Item::cond_result having_value
Definition: sql_lex.h:2055
Query_expression * master_query_expression() const
Definition: sql_lex.h:1250
This class represents a query expression (one query block or several query blocks combined with UNION...
Definition: sql_lex.h:622
Definition: query_result.h:53
RAII class to ease the temporary switching to a different slice of the ref item array.
Definition: sql_optimizer.h:1047
Switch_ref_item_slice(JOIN *join_arg, uint new_v)
Definition: sql_optimizer.h:1052
uint saved
Definition: sql_optimizer.h:1049
JOIN * join
Definition: sql_optimizer.h:1048
~Switch_ref_item_slice()
Definition: sql_optimizer.h:1056
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_class.h:922
This class restores a table_map object to its original value when '*this' is destroyed.
Definition: sql_optimizer.h:1120
Table_map_restorer(table_map *map)
Constructor.
Definition: sql_optimizer.h:1131
Table_map_restorer & operator=(const Table_map_restorer &)=delete
table_map *const m_location
The location to be restored.
Definition: sql_optimizer.h:1122
~Table_map_restorer()
Definition: sql_optimizer.h:1138
const table_map m_saved_value
The original value to restore.
Definition: sql_optimizer.h:1124
void restore()
Definition: sql_optimizer.h:1139
void assert_unchanged() const
Definition: sql_optimizer.h:1140
Table_map_restorer(const Table_map_restorer &)=delete
Object containing parameters used when creating and using temporary tables.
Definition: temp_table_param.h:94
uint sum_func_count
Number of fields in the query that have aggregate functions.
Definition: temp_table_param.h:131
Represents the (explicit) window of a SQL 2003 section 7.11 <window clause>, or the implicit (inlined...
Definition: window.h:104
A (partial) implementation of std::deque allocating its blocks on a MEM_ROOT.
Definition: mem_root_deque.h:109
bool is_temporal_type(enum_field_types type)
Tests if field type is temporal, i.e.
Definition: field_common_properties.h:114
bool is_temporal_type_with_date(enum_field_types type)
Tests if field type is temporal and has date part, i.e.
Definition: field_common_properties.h:155
This file contains the field type.
enum_field_types
Column types for MySQL.
Definition: field_types.h:52
void optimize_distinct()
Optimize distinct when used on a subset of the tables.
Definition: sql_executor.cc:346
AccessPath * create_root_access_path_for_join()
Definition: sql_executor.cc:3021
void restore_fields(table_map save_nullinfo)
Restore all result fields for all tables specified in save_nullinfo.
Definition: sql_executor.cc:4637
bool create_intermediate_table(QEP_TAB *tab, const mem_root_deque< Item * > &tmp_table_fields, ORDER_with_src &tmp_table_group, bool save_sum_fields)
Create a temporary table to be used for processing DISTINCT/ORDER BY/GROUP BY.
Definition: sql_executor.cc:177
AccessPath * attach_access_paths_for_having_and_limit(AccessPath *path)
Definition: sql_executor.cc:3360
QEP_TAB::enum_op_type get_end_select_func()
Definition: sql_executor.cc:574
void create_access_paths()
Convert the executor structures to a set of access paths, storing the result in m_root_access_path.
Definition: sql_executor.cc:2991
void create_access_paths_for_index_subquery()
Definition: sql_executor.cc:3393
AccessPath * attach_access_path_for_update_or_delete(AccessPath *path)
Definition: sql_executor.cc:2955
bool clear_fields(table_map *save_nullinfo)
Set all column values from all input tables to NULL.
Definition: sql_executor.cc:4616
bool clear_corr_derived_tmp_tables()
Empties all correlated materialized derived tables.
Definition: sql_select.cc:1585
Item_equal * find_item_equal(COND_EQUAL *cond_equal, const Item_field *item_field, bool *inherited_fl)
Find the multiple equality predicate containing a field.
Definition: sql_optimizer.cc:3622
uint build_bitmap_for_nested_joins(mem_root_deque< TABLE_LIST * > *join_list, uint first_unused)
Assign each nested join structure a bit in nested_join_map.
Definition: sql_optimizer.cc:4902
bool alloc_func_list()
Make an array of pointers to sum_functions to speed up sum_func calculation.
Definition: sql_select.cc:3868
Item_field * get_best_field(Item_field *item_field, COND_EQUAL *cond_equal)
Get the best field substitution for a given field.
Definition: sql_optimizer.cc:3655
void update_sargable_from_const(SARGABLE_PARAM *sargables)
Update info on indexes that can be used for search lookups as reading const tables may has added new ...
Definition: sql_optimizer.cc:5751
bool add_sorting_to_table(uint idx, ORDER_with_src *order, bool sort_before_group)
Add Filesort object to the given table to sort if with filesort.
Definition: sql_select.cc:4781
bool clear_sj_tmp_tables()
Remove all rows from all temp tables used by NL-semijoin runtime.
Definition: sql_select.cc:1575
bool alloc_qep(uint n)
Definition: sql_optimizer.cc:1264
void change_to_access_path_without_in2exists()
If this query block was planned twice, once with and once without conditions added by in2exists,...
Definition: sql_optimizer.cc:1063
void unplug_join_tabs()
Definition: sql_select.cc:4753
bool push_to_engines()
Handle offloading of query parts to the underlying engines, when such is supported by their implement...
Definition: sql_optimizer.cc:1099
bool make_tmp_tables_info()
Init tmp tables usage info.
Definition: sql_select.cc:4151
bool make_join_plan()
Calculate best possible join order and initialize the join structure.
Definition: sql_optimizer.cc:5184
void set_semijoin_embedding()
Set semi-join embedding join nest pointers.
Definition: sql_optimizer.cc:5899
bool build_equal_items(THD *thd, Item *cond, Item **retcond, COND_EQUAL *inherited, bool do_inherit, mem_root_deque< TABLE_LIST * > *join_list, COND_EQUAL **cond_equal_ref)
Build multiple equalities for a WHERE condition and all join conditions that inherit these multiple e...
Definition: sql_optimizer.cc:4344
bool optimize_distinct_group_order()
Optimize DISTINCT, GROUP BY, ORDER BY clauses.
Definition: sql_optimizer.cc:1412
JOIN(THD *thd_arg, Query_block *select)
Definition: sql_optimizer.cc:158
table_map calculate_deps_of_remaining_lateral_derived_tables(table_map plan_tables, uint idx) const
Finds the dependencies of the remaining lateral derived tables.
Definition: sql_optimizer.cc:3207
void set_prefix_tables()
Assign set of available (prefix) tables to all tables in query block.
Definition: sql_optimizer.cc:5077
void cleanup()
Cleanup this JOIN.
Definition: sql_select.cc:3509
bool uses_index_fields_only(Item *item, TABLE *tbl, uint keyno, bool other_tbls_ok)
Check if given expression only uses fields covered by index keyno in the table tbl.
Definition: sql_optimizer.cc:6352
void test_skip_sort()
Test if an index could be used to replace filesort for ORDER BY/GROUP BY.
Definition: sql_optimizer.cc:1605
void create_access_paths_for_zero_rows()
Create access paths with the knowledge that there are going to be zero rows coming from tables (befor...
Definition: sql_optimizer.cc:1069
bool propagate_dependencies()
Propagate dependencies between tables due to outer join relations.
Definition: sql_optimizer.cc:5449
void adjust_access_methods()
An utility function - apply heuristics and optimize access methods to tables.
Definition: sql_optimizer.cc:2865
bool estimate_rowcount()
Estimate the number of matched rows for each joined table.
Definition: sql_optimizer.cc:5787
bool prune_table_partitions()
Prune partitions for all tables of a join (query block).
Definition: sql_optimizer.cc:2714
void refresh_base_slice()
In the case of rollup (only): After the base slice list was made, we may have modified the field list...
Definition: sql_select.cc:4728
bool alloc_ref_item_slice(THD *thd_arg, int sliceno)
Allocate a ref_item slice, assume that slice size is in ref_items[0].
Definition: sql_optimizer.cc:198
bool setup_semijoin_materialized_table(JOIN_TAB *tab, uint tableno, POSITION *inner_pos, POSITION *sjm_pos)
Setup the materialized table for a semi-join nest.
Definition: sql_select.cc:2899
void join_free()
Release memory and, if possible, the open tables held by this execution plan (and nested plans).
Definition: sql_select.cc:3441
bool make_sum_func_list(const mem_root_deque< Item * > &fields, bool before_group_by, bool recompute=false)
Initialize 'sum_funcs' array with all Item_sum objects.
Definition: sql_select.cc:3916
bool extract_func_dependent_tables()
Extract const tables based on functional dependencies.
Definition: sql_optimizer.cc:5594
bool init_planner_arrays()
Initialize scratch arrays for the join order optimization.
Definition: sql_optimizer.cc:5322
bool substitute_gc(THD *thd, Query_block *query_block, Item *where_cond, ORDER *group_list, ORDER *order)
Substitute all expressions in the WHERE condition and ORDER/GROUP lists that match generated columns ...
Definition: sql_optimizer.cc:1145
void set_semijoin_info()
Set the first_sj_inner_tab and last_sj_inner_tab fields for all tables inside the semijoin nests of t...
Definition: sql_select.cc:2032
bool prepare_result()
Prepare join result.
Definition: sql_select.cc:1669
void destroy()
Clean up and destroy join object.
Definition: sql_select.cc:1687
bool add_having_as_tmp_table_cond(uint curr_tmp_table)
Add having condition as a filter condition, which is applied when reading from the temp table.
Definition: sql_select.cc:3995
Item * substitute_for_best_equal_field(THD *thd, Item *cond, COND_EQUAL *cond_equal, JOIN_TAB **table_join_idx)
Substitute every field reference in a condition by the best equal field and eliminate all multiple eq...
Definition: sql_optimizer.cc:4650
double find_worst_seeks(const TABLE *table, double num_rows, double table_scan_cost)
Find an artificial cap for ref access.
Definition: sql_optimizer.cc:5767
const char * antijoin_null_cond
Definition: sql_optimizer.cc:116
bool alloc_indirection_slices()
Definition: sql_optimizer.cc:208
void reset()
Reset the state of this join object so that it is ready for a new execution.
Definition: sql_select.cc:1606
bool optimize(bool finalize_access_paths)
Optimizes one query block into a query execution plan (QEP.)
Definition: sql_optimizer.cc:282
bool init_ref_access()
Initialize ref access for all tables that use it.
Definition: sql_select.cc:2009
bool get_best_combination()
Set up JOIN_TAB structs according to the picked join order in best_positions.
Definition: sql_optimizer.cc:2983
bool extract_const_tables()
Extract const tables based on row counts.
Definition: sql_optimizer.cc:5500
bool update_equalities_for_sjm()
Update equalities and keyuse references after semi-join materialization strategy is chosen.
Definition: sql_optimizer.cc:5013
void set_plan_state(enum_plan_state plan_state_arg)
Sets the plan's state of the JOIN.
Definition: sql_optimizer.cc:1236
void cleanup_item_list(const mem_root_deque< Item * > &items) const
Definition: sql_select.cc:1792
int replace_index_subquery()
Check whether this is a subquery that can be evaluated by index look-ups.
Definition: sql_optimizer.cc:1344
void update_depend_map()
Update the dependency map for the tables.
Definition: sql_optimizer.cc:4944
Subquery_strategy
Strategy which will be used to handle this subquery: flattening to a semi-join, conversion to a deriv...
Definition: item_subselect.h:390
This file follows Google coding style, except for the name MEM_ROOT (which is kept for historical rea...
This file includes constants used by all storage engines.
my_off_t ha_rows
Definition: my_base.h:1139
#define HA_POS_ERROR
Definition: my_base.h:1141
#define DBUG_PRINT(keyword, arglist)
Definition: my_dbug.h:180
uint64_t table_map
Definition: my_table_map.h:29
static char * path
Definition: mysqldump.cc:133
std::string join(Container cont, const std::string &delim)
join elements of an container into a string separated by a delimiter.
Definition: string.h:150
std::map< Key, Value, Compare, ut::allocator< std::pair< const Key, Value > > > map
Specialization of map which uses ut_allocator.
Definition: ut0new.h:2873
EXPLAIN FORMAT=<format> <command>.
Explain_sort_clause
Enumeration of ORDER BY, GROUP BY and DISTINCT clauses for array indexing.
Definition: opt_explain_format.h:425
@ ESC_none
Definition: opt_explain_format.h:426
@ ESP_EXISTS
Original query has this clause.
Definition: opt_explain_format.h:441
@ ESP_none
Definition: opt_explain_format.h:440
required string key
Definition: replication_asynchronous_connection_failover.proto:59
Classes for query execution.
Common types of the Optimizer, used by optimization and execution.
int plan_idx
This represents the index of a JOIN_TAB/QEP_TAB in an array.
Definition: sql_opt_exec_shared.h:53
@ REF_SLICE_ACTIVE
The slice which is used during evaluation of expressions; Item_ref::ref points there.
Definition: sql_opt_exec_shared.h:612
bool evaluate_during_optimization(const Item *item, const Query_block *select)
Checks if an Item, which is constant for execution, can be evaluated during optimization.
Definition: sql_optimizer.cc:11193
Item * make_cond_for_table(THD *thd, Item *cond, table_map tables, table_map used_table, bool exclude_expensive_cond)
Extract a condition that can be checked after reading given table.
Definition: sql_optimizer.cc:9267
double calculate_subquery_executions(const Item_subselect *subquery, Opt_trace_context *trace)
Estimates how many times a subquery will be executed as part of a query execution.
Definition: sql_optimizer.cc:10996
Key_use_array * create_keyuse_for_table(THD *thd, uint keyparts, Item_field **fields, const mem_root_deque< Item * > &outer_exprs)
Create a keyuse array for a table with a primary key.
Definition: sql_optimizer.cc:8296
ORDER * create_order_from_distinct(THD *thd, Ref_item_array ref_item_array, ORDER *order_list, mem_root_deque< Item * > *fields, bool skip_aggregates, bool convert_bit_fields_to_long, bool *all_order_by_fields_used)
Create an order list that consists of all non-const fields and items.
Definition: sql_optimizer.cc:10460
bool field_time_cmp_date(const Field *f, const Item *v)
Returns true if arguments are a temporal Field having no date, part and a temporal expression having ...
Definition: sql_optimizer.h:1107
bool optimize_cond(THD *thd, Item **conds, COND_EQUAL **cond_equal, mem_root_deque< TABLE_LIST * > *join_list, Item::cond_result *cond_value)
Optimize conditions by.
Definition: sql_optimizer.cc:10097
bool ref_lookup_subsumes_comparison(Field *field, Item *right_item)
Whether a ref lookup of “right_item” on “field” will give an exact comparison in all cases,...
Definition: sql_optimizer.cc:8739
bool is_indexed_agg_distinct(JOIN *join, mem_root_deque< Item_field * > *out_args)
Check for the presence of AGGFN(DISTINCT a) queries that may be subject to loose index scan.
Definition: sql_optimizer.cc:7880
bool IteratorsAreNeeded(const THD *thd, AccessPath *root_path)
Checks if we need to create iterators for this query.
Definition: sql_optimizer.cc:11227
bool remove_eq_conds(THD *thd, Item *cond, Item **retcond, Item::cond_result *cond_value)
Removes const and eq items.
Definition: sql_optimizer.cc:10213
Access paths are a query planning structure that correspond 1:1 to iterators, in that an access path ...
Definition: access_path.h:189
Definition: sql_optimizer.h:169
Temp_table_param * temp_table_param
Definition: sql_optimizer.h:174
TABLE * table
Definition: sql_optimizer.h:170
Definition: lock.h:38
Definition: table.h:280
A position of table within a join order.
Definition: sql_select.h:351
Definition: sql_optimizer.h:82
Item ** arg_value
Definition: sql_optimizer.h:84
Field * field
Definition: sql_optimizer.h:83
uint num_values
Definition: sql_optimizer.h:85
Definition: table.h:2756
Definition: table.h:1396
unsigned int uint
Definition: uca-dump.cc:29
#define PSI_NOT_INSTRUMENTED
Definition: validate_password_imp.cc:39
int n
Definition: xcom_base.cc:505