~drizzle-trunk/drizzle/development

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
 *
 *  Copyright (C) 2008 Sun Microsystems, Inc.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; version 2 of the License.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#pragma once

#include <drizzled/comp_creator.h>
#include <drizzled/item/ref.h>
#include <drizzled/item/field.h>
#include <drizzled/item/bin_string.h>
#include <drizzled/util/test.h>

namespace drizzled {

class Item_subselect : public Item_result_field
{
  bool value_assigned; /* value already assigned to subselect */
public:
  /* thread handler, will be assigned in fix_fields only */
  Session *session;
  /* substitution instead of subselect in case of optimization */
  Item *substitution;
  /* unit of subquery */
  Select_Lex_Unit *unit;
protected:
  /* engine that perform execution of subselect (single select or union) */
  subselect_engine *engine;
  /* old engine if engine was changed */
  subselect_engine *old_engine;
  /* cache of used external tables */
  table_map used_tables_cache;
  /* allowed number of columns (1 for single value subqueries) */
  uint32_t max_columns;
  /* where subquery is placed */
  enum_parsing_place parsing_place;
  /* work with 'substitution' */
  bool have_to_be_excluded;
  /* cache of constant state */
  bool const_item_cache;

public:
  /* changed engine indicator */
  bool engine_changed;
  /* subquery is transformed */
  bool changed;

  /* TRUE <=> The underlying SELECT is correlated w.r.t some ancestor select */
  bool is_correlated;

  enum trans_res {RES_OK, RES_REDUCE, RES_ERROR};
  enum subs_type {UNKNOWN_SUBS, SINGLEROW_SUBS,
		  EXISTS_SUBS, IN_SUBS, ALL_SUBS, ANY_SUBS};

  Item_subselect();

  virtual subs_type substype() { return UNKNOWN_SUBS; }

  /*
    We need this method, because some compilers do not allow 'this'
    pointer in constructor initialization list, but we need to pass a pointer
    to subselect Item class to select_result_interceptor's constructor.
  */
  virtual void init (Select_Lex *select_lex,
		     select_result_interceptor *result);

  ~Item_subselect();
  void cleanup();
  virtual void reset()
  {
    null_value= 1;
  }
  virtual trans_res select_transformer(Join *join);
  bool assigned() { return value_assigned; }
  void assigned(bool a) { value_assigned= a; }
  enum Type type() const;
  bool is_null()
  {
    update_null_value();
    return null_value;
  }
  bool fix_fields(Session *session, Item **ref);
  virtual bool exec();
  virtual void fix_length_and_dec();
  table_map used_tables() const;
  table_map not_null_tables() const { return 0; }
  bool const_item() const;
  inline table_map get_used_tables_cache() { return used_tables_cache; }
  inline bool get_const_item_cache() { return const_item_cache; }
  Item *get_tmp_table_item(Session *session);
  void update_used_tables();
  virtual void print(String *str);
  virtual bool have_guarded_conds() { return false; }
  bool change_engine(subselect_engine *eng)
  {
    old_engine= engine;
    engine= eng;
    engine_changed= 1;
    return eng == 0;
  }
  /*
    True if this subquery has been already evaluated. Implemented only for
    single select and union subqueries only.
  */
  bool is_evaluated() const;
  bool is_uncacheable() const;

  /*
    Used by max/min subquery to initialize value presence registration
    mechanism. Engine call this method before rexecution query.
  */
  virtual void reset_value_registration() {}
  enum_parsing_place place() { return parsing_place; }
  bool walk(Item_processor processor, bool walk_subquery, unsigned char *arg);

  /**
    Get the Select_Lex structure associated with this Item.
    @return the Select_Lex structure associated with this Item
  */
  Select_Lex* get_select_lex();

  friend class select_result_interceptor;
  friend class Item_in_optimizer;
  friend bool Item_field::fix_fields(Session *, Item **);
  friend int  Item_field::fix_outer_field(Session *, Field **, Item **);
  friend bool Item_ref::fix_fields(Session *, Item **);
  friend void mark_select_range_as_dependent(Session*,
                                             Select_Lex*, Select_Lex*,
                                             Field*, Item*, Item_ident*);
};

/* single value subselect */

class Item_singlerow_subselect :public Item_subselect
{
protected:
  Item_cache *value, **row;
public:
  Item_singlerow_subselect(Select_Lex *select_lex);
  Item_singlerow_subselect() :Item_subselect(), value(0), row (0) {}

  void cleanup();
  subs_type substype() { return SINGLEROW_SUBS; }

  void reset();
  trans_res select_transformer(Join *join);
  void store(uint32_t i, Item* item);
  double val_real();
  int64_t val_int ();
  String *val_str (String *);
  type::Decimal *val_decimal(type::Decimal *);
  bool val_bool();
  enum Item_result result_type() const;
  enum_field_types field_type() const;
  void fix_length_and_dec();

  uint32_t cols();
  Item* element_index(uint32_t i) { return reinterpret_cast<Item*>(row[i]); }
  Item** addr(uint32_t i) { return (Item**)row + i; }
  bool check_cols(uint32_t c);
  bool null_inside();
  void bring_value();

  /**
    This method is used to implement a special case of semantic tree
    rewriting, mandated by a SQL:2003 exception in the specification.
    The only caller of this method is handle_sql2003_note184_exception(),
    see the code there for more details.
    Note that this method breaks the object internal integrity, by
    removing it's association with the corresponding Select_Lex,
    making this object orphan from the parse tree.
    No other method, beside the destructor, should be called on this
    object, as it is now invalid.
    @return the Select_Lex structure that was given in the constructor.
  */
  Select_Lex* invalidate_and_restore_select_lex();

  friend class select_singlerow_subselect;
};

/* used in static ALL/ANY optimization */
class Item_maxmin_subselect :public Item_singlerow_subselect
{
protected:
  bool max;
  bool was_values;  // Set if we have found at least one row
public:
  Item_maxmin_subselect(Session *session, Item_subselect *parent,
			Select_Lex *select_lex, bool max);
  virtual void print(String *str);
  void cleanup();
  bool any_value() { return was_values; }
  void register_value() { was_values= true; }
  void reset_value_registration() { was_values= false; }
};

/* exists subselect */

class Item_exists_subselect :public Item_subselect
{
protected:
  bool value; /* value of this item (boolean: exists/not-exists) */

public:
  Item_exists_subselect(Select_Lex *select_lex);
  Item_exists_subselect(): Item_subselect() {}

  subs_type substype() { return EXISTS_SUBS; }
  void reset()
  {
    value= 0;
  }

  enum Item_result result_type() const { return INT_RESULT;}
  int64_t val_int();
  double val_real();
  String *val_str(String*);
  type::Decimal *val_decimal(type::Decimal *);
  bool val_bool();
  void fix_length_and_dec();
  virtual void print(String *str);

  friend class select_exists_subselect;
  friend class subselect_uniquesubquery_engine;
  friend class subselect_indexsubquery_engine;
};


/**
  Representation of IN subquery predicates of the form
  "left_expr IN (SELECT ...)".

  @detail
  This class has:
   - A "subquery execution engine" (as a subclass of Item_subselect) that allows
     it to evaluate subqueries. (and this class participates in execution by
     having was_null variable where part of execution result is stored.
   - Transformation methods (todo: more on this).

  This class is not used directly, it is "wrapped" into Item_in_optimizer
  which provides some small bits of subquery evaluation.
*/

class Item_in_subselect :public Item_exists_subselect
{
public:
  Item *left_expr;
protected:
  /*
    Cache of the left operand of the subquery predicate. Allocated in the
    runtime memory root, for each execution, thus need not be freed.
  */
  List<Cached_item> *left_expr_cache;
  bool first_execution;

  /*
    expr & optimizer used in subselect rewriting to store Item for
    all JOIN in UNION
  */
  Item *expr;
  Item_in_optimizer *optimizer;
  bool was_null;
  bool abort_on_null;

public:
  /* Used to trigger on/off conditions that were pushed down to subselect */
  bool *pushed_cond_guards;

  /* Priority of this predicate in the convert-to-semi-join-nest process. */
  int sj_convert_priority;

  /*
    Location of the subquery predicate. It is either
     - pointer to join nest if the subquery predicate is in the ON expression
     - (TableList*)1 if the predicate is in the WHERE.
  */
  TableList *expr_join_nest;

  /* The method chosen to execute the IN predicate.  */
  enum enum_exec_method {
    NOT_TRANSFORMED, /* No execution method was chosen for this IN. */
    SEMI_JOIN,   /* IN was converted to semi-join nest and should be removed. */
    IN_TO_EXISTS, /* IN was converted to correlated EXISTS. */
    MATERIALIZATION /* IN will be executed via subquery materialization. */
  };
  enum_exec_method exec_method;

  bool *get_cond_guard(int i)
  {
    return pushed_cond_guards ? pushed_cond_guards + i : NULL;
  }
  void set_cond_guard_var(int i, bool v)
  {
    if ( pushed_cond_guards)
      pushed_cond_guards[i]= v;
  }
  bool have_guarded_conds() { return test(pushed_cond_guards); }

  Item_func_not_all *upper_item; // point on NOT/NOP before ALL/SOME subquery

  Item_in_subselect(Item * left_expr, Select_Lex *select_lex);
  Item_in_subselect()
    :
      Item_exists_subselect(),
      left_expr(NULL),
      left_expr_cache(NULL),
      first_execution(true),
      optimizer(NULL),
      abort_on_null(false),
      pushed_cond_guards(NULL),
      sj_convert_priority(0),
      expr_join_nest(NULL),
      exec_method(NOT_TRANSFORMED),
      upper_item(NULL)
  {}
  void cleanup();
  subs_type substype() { return IN_SUBS; }
  void reset()
  {
    value= 0;
    null_value= 0;
    was_null= 0;
  }
  trans_res select_transformer(Join *join);
  trans_res select_in_like_transformer(Join *join, const Comp_creator *func);
  trans_res single_value_transformer(Join *join, const Comp_creator *func);
  trans_res row_value_transformer(Join * join);
  trans_res single_value_in_to_exists_transformer(Join * join,
                                                  const Comp_creator *func);
  trans_res row_value_in_to_exists_transformer(Join * join);
  virtual bool exec();
  int64_t val_int();
  double val_real();
  String *val_str(String*);
  type::Decimal *val_decimal(type::Decimal *);
  void update_null_value () { (void) val_bool(); }
  bool val_bool();
  void top_level_item() { abort_on_null=1; }
  inline bool is_top_level_item() { return abort_on_null; }
  bool test_limit(Select_Lex_Unit *unit);
  virtual void print(String *str);
  bool fix_fields(Session *session, Item **ref);
  bool setup_engine();
  bool init_left_expr_cache();
  bool is_expensive_processor(unsigned char *arg);

  friend class Item_ref_null_helper;
  friend class Item_is_not_null_test;
  friend class Item_in_optimizer;
  friend class subselect_indexsubquery_engine;
  friend class subselect_hash_sj_engine;
};


/* ALL/ANY/SOME subselect */
class Item_allany_subselect :public Item_in_subselect
{
public:
  chooser_compare_func_creator func_creator;
  Comp_creator *func;
  bool all;

  Item_allany_subselect(Item * left_expr, chooser_compare_func_creator fc,
                        Select_Lex *select_lex, bool all);

  // only ALL subquery has upper not
  subs_type substype() { return all?ALL_SUBS:ANY_SUBS; }
  trans_res select_transformer(Join *join);
  virtual void print(String *str);
};


class subselect_engine: public memory::SqlAlloc
{
protected:
  select_result_interceptor *result; /* results storage class */
  Session *session; /* pointer to current Session */
  Item_subselect *item; /* item, that use this engine */
  enum Item_result res_type; /* type of results */
  enum_field_types res_field_type; /* column type of the results */
  bool maybe_null; /* may be null (first item in select) */
public:

  enum enum_engine_type {ABSTRACT_ENGINE, SINGLE_SELECT_ENGINE,
                         UNION_ENGINE, UNIQUESUBQUERY_ENGINE,
                         INDEXSUBQUERY_ENGINE, HASH_SJ_ENGINE};

  subselect_engine(Item_subselect *si, select_result_interceptor *res)
    :session(NULL)
  {
    result= res;
    item= si;
    res_type= STRING_RESULT;
    res_field_type= DRIZZLE_TYPE_VARCHAR;
    maybe_null= 0;
  }
  virtual ~subselect_engine() {} // to satisfy compiler
  virtual void cleanup()= 0;

  /*
    Also sets "session" for subselect_engine::result.
    Should be called before prepare().
  */
  void set_session(Session *session_arg);
  Session * get_session() { return session; }
  virtual int prepare()= 0;
  virtual void fix_length_and_dec(Item_cache** row)= 0;
  /*
    Execute the engine

    SYNOPSIS
      exec()

    DESCRIPTION
      Execute the engine. The result of execution is subquery value that is
      either captured by previously set up select_result-based 'sink' or
      stored somewhere by the exec() method itself.

      A required side effect: If at least one pushed-down predicate is
      disabled, subselect_engine->no_rows() must return correct result after
      the exec() call.

    RETURN
      0 - OK
      1 - Either an execution error, or the engine was "changed", and the
          caller should call exec() again for the new engine.
  */
  virtual int exec()= 0;
  virtual uint32_t cols()= 0; /* return number of columns in select */
  virtual bool uncacheable()= 0; /* query is uncacheable */
  virtual bool uncacheable(uint32_t bit_pos)= 0; /* query is uncacheable */
  enum Item_result type() { return res_type; }
  enum_field_types field_type() { return res_field_type; }
  virtual void exclude()= 0;
  virtual bool may_be_null() { return maybe_null; }
  virtual table_map upper_select_const_tables()= 0;
  static table_map calc_const_tables(TableList *);
  virtual void print(String *str)= 0;
  virtual bool change_result(Item_subselect *si,
                             select_result_interceptor *result)= 0;
  virtual bool no_tables()= 0;
  virtual bool is_executed() const { return false; }
  /* Check if subquery produced any rows during last query execution */
  virtual bool no_rows() = 0;
  virtual enum_engine_type engine_type() { return ABSTRACT_ENGINE; }

protected:
  void set_row(List<Item> &item_list, Item_cache **row);
};


class subselect_single_select_engine: public subselect_engine
{
  bool prepared; /* simple subselect is prepared */
  bool optimized; /* simple subselect is optimized */
  bool executed; /* simple subselect is executed */
  Select_Lex *select_lex; /* corresponding select_lex */
  Join * join; /* corresponding JOIN structure */
public:
  subselect_single_select_engine(Select_Lex *select,
				 select_result_interceptor *result,
				 Item_subselect *item);
  void cleanup();
  int prepare();
  void fix_length_and_dec(Item_cache** row);
  int exec();
  uint32_t cols();
  bool uncacheable();
  bool uncacheable(uint32_t bit_pos);
  void exclude();
  table_map upper_select_const_tables();
  virtual void print (String *str);
  bool change_result(Item_subselect *si, select_result_interceptor *result);
  bool no_tables();
  bool may_be_null();
  bool is_executed() const { return executed; }
  bool no_rows();
  virtual enum_engine_type engine_type() { return SINGLE_SELECT_ENGINE; }
  void save_join_if_explain();

  friend class subselect_hash_sj_engine;
  friend class Item_in_subselect;
};


class subselect_union_engine: public subselect_engine
{
  Select_Lex_Unit *unit;  /* corresponding unit structure */
public:
  subselect_union_engine(Select_Lex_Unit *u,
			 select_result_interceptor *result,
			 Item_subselect *item);
  void cleanup();
  int prepare();
  void fix_length_and_dec(Item_cache** row);
  int exec();
  uint32_t cols();
  bool uncacheable();
  bool uncacheable(uint32_t bit_pos);
  void exclude();
  table_map upper_select_const_tables();
  virtual void print (String *str);
  bool change_result(Item_subselect *si, select_result_interceptor *result);
  bool no_tables();
  bool is_executed() const;
  bool no_rows();
  virtual enum_engine_type engine_type() { return UNION_ENGINE; }
};


/*
  A subquery execution engine that evaluates the subquery by doing one index
  lookup in a unique index.

  This engine is used to resolve subqueries in forms

    outer_expr IN (SELECT tbl.unique_key FROM tbl WHERE subq_where)

  or, tuple-based:

    (oe1, .. oeN) IN (SELECT uniq_key_part1, ... uniq_key_partK
                      FROM tbl WHERE subqwhere)

  i.e. the subquery is a single table SELECT without GROUP BY, aggregate
  functions, etc.
*/

class subselect_uniquesubquery_engine: public subselect_engine
{
protected:
  JoinTable *tab;
  Item *cond; /* The WHERE condition of subselect */
  /*
    TRUE<=> last execution produced empty set. Valid only when left
    expression is NULL.
  */
  bool empty_result_set;
  bool null_keypart; /* TRUE <=> constructed search tuple has a NULL */
public:

  // constructor can assign Session because it will be called after Join::prepare
  subselect_uniquesubquery_engine(Session *session_arg, JoinTable *tab_arg,
				  Item_subselect *subs, Item *where)
    :subselect_engine(subs, 0), tab(tab_arg), cond(where)
  {
    set_session(session_arg);
  }
  void cleanup();
  int prepare();
  void fix_length_and_dec(Item_cache** row);
  int exec();
  uint32_t cols() { return 1; }
  bool uncacheable() { return true; }
  bool uncacheable(uint32_t) { return true; }
  void exclude();
  table_map upper_select_const_tables() { return 0; }
  virtual void print (String *str);
  bool change_result(Item_subselect *si, select_result_interceptor *result);
  bool no_tables();
  int scan_table();
  bool copy_ref_key();
  bool no_rows() { return empty_result_set; }
  virtual enum_engine_type engine_type() { return UNIQUESUBQUERY_ENGINE; }
};


class subselect_indexsubquery_engine: public subselect_uniquesubquery_engine
{
  /* FALSE for 'ref', TRUE for 'ref-or-null'. */
  bool check_null;
  /*
    The "having" clause. This clause (further reffered to as "artificial
    having") was inserted by subquery transformation code. It contains
    Item(s) that have a side-effect: they record whether the subquery has
    produced a row with NULL certain components. We need to use it for cases
    like
      (oe1, oe2) IN (SELECT t.key, t.no_key FROM t1)
    where we do index lookup on t.key=oe1 but need also to check if there
    was a row such that t.no_key IS NULL.

    NOTE: This is currently here and not in the uniquesubquery_engine. Ideally
    it should have been in uniquesubquery_engine in order to allow execution of
    subqueries like

      (oe1, oe2) IN (SELECT primary_key, non_key_maybe_null_field FROM tbl)

    We could use uniquesubquery_engine for the first component and let
    Item_is_not_null_test( non_key_maybe_null_field) to handle the second.

    However, subqueries like the above are currently not handled by index
    lookup-based subquery engines, the engine applicability check misses
    them: it doesn't switch the engine for case of artificial having and
    [eq_]ref access (only for artifical having + ref_or_null or no having).
    The above example subquery is handled as a full-blown SELECT with eq_ref
    access to one table.

    Due to this limitation, the "artificial having" currently needs to be
    checked by only in indexsubquery_engine.
  */
  Item *having;
public:

  // constructor can assign Session because it will be called after Join::prepare
  subselect_indexsubquery_engine(Session *session_arg, JoinTable *tab_arg,
				 Item_subselect *subs, Item *where,
                                 Item *having_arg, bool chk_null)
    :subselect_uniquesubquery_engine(session_arg, tab_arg, subs, where),
     check_null(chk_null),
     having(having_arg)
  {}
  int exec();
  virtual void print (String *str);
  virtual enum_engine_type engine_type() { return INDEXSUBQUERY_ENGINE; }
};


inline bool Item_subselect::is_evaluated() const
{
  return engine->is_executed();
}


inline bool Item_subselect::is_uncacheable() const
{
  return engine->uncacheable();
}


/**
  Compute an IN predicate via a hash semi-join. The subquery is materialized
  during the first evaluation of the IN predicate. The IN predicate is executed
  via the functionality inherited from subselect_uniquesubquery_engine.
*/

class subselect_hash_sj_engine: public subselect_uniquesubquery_engine
{
protected:
  /* TRUE if the subquery was materialized into a temp table. */
  bool is_materialized;
  /*
    The old engine already chosen at parse time and stored in permanent memory.
    Through this member we can re-create and re-prepare materialize_join for
    each execution of a prepared statement. We akso resuse the functionality
    of subselect_single_select_engine::[prepare | cols].
  */
  subselect_single_select_engine *materialize_engine;
  /*
    QEP to execute the subquery and materialize its result into a
    temporary table. Created during the first call to exec().
  */
  Join *materialize_join;
  /* Temp table context of the outer select's JOIN. */
  Tmp_Table_Param *tmp_param;

public:
  subselect_hash_sj_engine(Session *session_in, Item_subselect *in_predicate,
                               subselect_single_select_engine *old_engine)
    :subselect_uniquesubquery_engine(session_in, NULL, in_predicate, NULL),
    is_materialized(false), materialize_engine(old_engine),
    materialize_join(NULL), tmp_param(NULL)
  {}
  ~subselect_hash_sj_engine();

  bool init_permanent(List<Item> *tmp_columns);
  void init_runtime();
  void cleanup();
  int prepare() { return 0; }
  int exec();
  virtual void print (String *str);
  uint32_t cols()
  {
    return materialize_engine->cols();
  }
  virtual enum_engine_type engine_type() { return HASH_SJ_ENGINE; }
};

} /* namespace drizzled */