summaryrefslogtreecommitdiff
path: root/sql/sql_help.cc
blob: 78349a6ef0db59bf473fc9ee8eecaed0fc4c8ebc (plain)
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
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
/* Copyright (C) 2000 MySQL AB

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

#include "mysql_priv.h"

struct st_find_field
{
  const char *table_name, *field_name;
  Field *field;
};

/* Used fields */

static struct st_find_field init_used_fields[]=
{
  { "help_topic",    "help_topic_id",      0},
  { "help_topic",    "name",               0},
  { "help_topic",    "help_category_id",   0},
  { "help_topic",    "description",        0},
  { "help_topic",    "example",            0},

  { "help_category", "help_category_id",   0},
  { "help_category", "parent_category_id", 0},
  { "help_category", "name",               0},

  { "help_keyword",  "help_keyword_id",    0},
  { "help_keyword",  "name",               0},

  { "help_relation", "help_topic_id",      0},
  { "help_relation", "help_keyword_id",    0}
};

enum enum_used_fields
{
  help_topic_help_topic_id= 0,
  help_topic_name,
  help_topic_help_category_id,
  help_topic_description,
  help_topic_example,

  help_category_help_category_id,
  help_category_parent_category_id,
  help_category_name,

  help_keyword_help_keyword_id,
  help_keyword_name,

  help_relation_help_topic_id,
  help_relation_help_keyword_id
};


/*
  Fill st_find_field structure with pointers to fields

  SYNOPSIS
    init_fields()
    thd          Thread handler
    tables       list of all tables for fields
    find_fields  array of structures
    count        size of previous array

  RETURN VALUES
    0           all ok
    1           one of the fileds was not found
*/

static bool init_fields(THD *thd, TABLE_LIST *tables,
			struct st_find_field *find_fields, uint count)
{
  Name_resolution_context *context= &thd->lex->select_lex.context;
  DBUG_ENTER("init_fields");
  context->resolve_in_table_list_only(tables);
  for (; count-- ; find_fields++)
  {
    /* We have to use 'new' here as field will be re_linked on free */
    Item_field *field= new Item_field(context,
                                      "mysql", find_fields->table_name,
                                      find_fields->field_name);
    if (!(find_fields->field= find_field_in_tables(thd, field, tables, NULL,
						   0, REPORT_ALL_ERRORS, 1,
                                                   TRUE)))
      DBUG_RETURN(1);
  }
  DBUG_RETURN(0);
}


/*
  Returns variants of found topic for help (if it is just single topic,
    returns description and example, or else returns only names..)

  SYNOPSIS
    memorize_variant_topic()

    thd           Thread handler
    topics        Table of topics
    count         number of alredy found topics
    find_fields   Filled array of information for work with fields

  RETURN VALUES
    names         array of names of found topics (out)

    name          name of found topic (out)
    description   description of found topic (out)
    example       example for found topic (out)

  NOTE
    Field 'names' is set only if more than one topic is found.
    Fields 'name', 'description', 'example' are set only if
    found exactly one topic.
*/

void memorize_variant_topic(THD *thd, TABLE *topics, int count,
			    struct st_find_field *find_fields,
			    List<String> *names,
			    String *name, String *description, String *example)
{
  DBUG_ENTER("memorize_variant_topic");
  MEM_ROOT *mem_root= thd->mem_root;
  if (count==0)
  {
    get_field(mem_root,find_fields[help_topic_name].field,        name);
    get_field(mem_root,find_fields[help_topic_description].field, description);
    get_field(mem_root,find_fields[help_topic_example].field,     example);
  }
  else
  {
    if (count == 1)
      names->push_back(name);
    String *new_name= new (thd->mem_root) String;
    get_field(mem_root,find_fields[help_topic_name].field,new_name);
    names->push_back(new_name);
  }
  DBUG_VOID_RETURN;
}

/*
  Look for topics by mask

  SYNOPSIS
    search_topics()
    thd 	 Thread handler
    topics	 Table of topics
    find_fields  Filled array of info for fields
    select	 Function to test for matching help topic.
		 Normally 'help_topic.name like 'bit%'

  RETURN VALUES
    #   number of topics found

    names        array of names of found topics (out)
    name         name of found topic (out)
    description  description of found topic (out)
    example      example for found topic (out)

  NOTE
    Field 'names' is set only if more than one topic was found.
    Fields 'name', 'description', 'example' are set only if
    exactly one topic was found.

*/

int search_topics(THD *thd, TABLE *topics, struct st_find_field *find_fields,
		  SQL_SELECT *select, List<String> *names,
		  String *name, String *description, String *example)
{
  DBUG_ENTER("search_topics");
  int count= 0;

  READ_RECORD read_record_info;
  init_read_record(&read_record_info, thd, topics, select,1,0);
  while (!read_record_info.read_record(&read_record_info))
  {
    if (!select->cond->val_int())		// Doesn't match like
      continue;
    memorize_variant_topic(thd,topics,count,find_fields,
			   names,name,description,example);
    count++;
  }
  end_read_record(&read_record_info);

  DBUG_RETURN(count);
}

/*
  Look for keyword by mask

  SYNOPSIS
    search_keyword()
    thd          Thread handler
    keywords     Table of keywords
    find_fields  Filled array of info for fields
    select       Function to test for matching keyword.
	         Normally 'help_keyword.name like 'bit%'

    key_id       help_keyword_if of found topics (out)

  RETURN VALUES
    0   didn't find any topics matching the mask
    1   found exactly one topic matching the mask
    2   found more then one topic matching the mask
*/

int search_keyword(THD *thd, TABLE *keywords, struct st_find_field *find_fields,
                   SQL_SELECT *select, int *key_id)
{
  DBUG_ENTER("search_keyword");
  int count= 0;

  READ_RECORD read_record_info;
  init_read_record(&read_record_info, thd, keywords, select,1,0);
  while (!read_record_info.read_record(&read_record_info) && count<2)
  {
    if (!select->cond->val_int())		// Dosn't match like
      continue;

    *key_id= (int)find_fields[help_keyword_help_keyword_id].field->val_int();

    count++;
  }
  end_read_record(&read_record_info);

  DBUG_RETURN(count);
}

/*
  Look for all topics with keyword

  SYNOPSIS
    get_topics_for_keyword()
    thd		 Thread handler
    topics	 Table of topics
    relations	 Table of m:m relation "topic/keyword"
    find_fields  Filled array of info for fields
    key_id	 Primary index to use to find for keyword

  RETURN VALUES
    #   number of topics found

    names        array of name of found topics (out)

    name         name of found topic (out)
    description  description of found topic (out)
    example      example for found topic (out)

  NOTE
    Field 'names' is set only if more than one topic was found.
    Fields 'name', 'description', 'example' are set only if
    exactly one topic was found.
*/

int get_topics_for_keyword(THD *thd, TABLE *topics, TABLE *relations,
			   struct st_find_field *find_fields, int16 key_id,
			   List<String> *names,
			   String *name, String *description, String *example)
{
  char buff[8];	// Max int length
  int count= 0;
  int iindex_topic, iindex_relations;
  Field *rtopic_id, *rkey_id;

  DBUG_ENTER("get_topics_for_keyword");

  if ((iindex_topic= find_type((char*) primary_key_name,
			       &topics->s->keynames, 1+2)-1)<0 ||
      (iindex_relations= find_type((char*) primary_key_name,
				   &relations->s->keynames, 1+2)-1)<0)
  {
    my_message(ER_CORRUPT_HELP_DB, ER(ER_CORRUPT_HELP_DB), MYF(0));
    DBUG_RETURN(-1);
  }
  rtopic_id= find_fields[help_relation_help_topic_id].field;
  rkey_id=   find_fields[help_relation_help_keyword_id].field;

  topics->file->ha_index_init(iindex_topic);
  relations->file->ha_index_init(iindex_relations);

  rkey_id->store((longlong) key_id, TRUE);
  rkey_id->get_key_image(buff, rkey_id->pack_length(), Field::itRAW);
  int key_res= relations->file->index_read(relations->record[0],
					   (byte *)buff, rkey_id->pack_length(),
					   HA_READ_KEY_EXACT);

  for ( ;
        !key_res && key_id == (int16) rkey_id->val_int() ;
	key_res= relations->file->index_next(relations->record[0]))
  {
    char topic_id_buff[8];
    longlong topic_id= rtopic_id->val_int();
    Field *field= find_fields[help_topic_help_topic_id].field;
    field->store((longlong) topic_id, TRUE);
    field->get_key_image(topic_id_buff, field->pack_length(), Field::itRAW);

    if (!topics->file->index_read(topics->record[0], (byte *)topic_id_buff,
				  field->pack_length(), HA_READ_KEY_EXACT))
    {
      memorize_variant_topic(thd,topics,count,find_fields,
			     names,name,description,example);
      count++;
    }
  }
  topics->file->ha_index_end();
  relations->file->ha_index_end();
  DBUG_RETURN(count);
}

/*
  Look for categories by mask

  SYNOPSIS
    search_categories()
    thd			THD for init_read_record
    categories		Table of categories
    find_fields         Filled array of info for fields
    select		Function to test for if matching help topic.
			Normally 'help_vategory.name like 'bit%'
    names		List of found categories names (out)
    res_id		Primary index of found category (only if
			found exactly one category)

  RETURN VALUES
    #			Number of categories found
*/

int search_categories(THD *thd, TABLE *categories,
		      struct st_find_field *find_fields,
		      SQL_SELECT *select, List<String> *names, int16 *res_id)
{
  Field *pfname= find_fields[help_category_name].field;
  Field *pcat_id= find_fields[help_category_help_category_id].field;
  int count= 0;
  READ_RECORD read_record_info;

  DBUG_ENTER("search_categories");

  init_read_record(&read_record_info, thd, categories, select,1,0);
  while (!read_record_info.read_record(&read_record_info))
  {
    if (select && !select->cond->val_int())
      continue;
    String *lname= new (thd->mem_root) String;
    get_field(thd->mem_root,pfname,lname);
    if (++count == 1 && res_id)
      *res_id= (int16) pcat_id->val_int();
    names->push_back(lname);
  }
  end_read_record(&read_record_info);

  DBUG_RETURN(count);
}

/*
  Look for all topics or subcategories of category

  SYNOPSIS
    get_all_items_for_category()
    thd	    Thread handler
    items   Table of items
    pfname  Field "name" in items
    select  "where" part of query..
    res     list of finded names
*/

void get_all_items_for_category(THD *thd, TABLE *items, Field *pfname,
				SQL_SELECT *select, List<String> *res)
{
  DBUG_ENTER("get_all_items_for_category");

  READ_RECORD read_record_info;
  init_read_record(&read_record_info, thd, items, select,1,0);
  while (!read_record_info.read_record(&read_record_info))
  {
    if (!select->cond->val_int())
      continue;
    String *name= new (thd->mem_root) String();
    get_field(thd->mem_root,pfname,name);
    res->push_back(name);
  }
  end_read_record(&read_record_info);

  DBUG_VOID_RETURN;
}

/*
  Send to client answer for help request

  SYNOPSIS
    send_answer_1()
    protocol - protocol for sending
    s1 - value of column "Name"
    s2 - value of column "Description"
    s3 - value of column "Example"

  IMPLEMENTATION
   Format used:
   +----------+------------+------------+
   |name      |description |example     |
   +----------+------------+------------+
   |String(64)|String(1000)|String(1000)|
   +----------+------------+------------+
   with exactly one row!

  RETURN VALUES
    1		Writing of head failed
    -1		Writing of row failed
    0		Successeful send
*/

int send_answer_1(Protocol *protocol, String *s1, String *s2, String *s3)
{
  DBUG_ENTER("send_answer_1");
  List<Item> field_list;
  field_list.push_back(new Item_empty_string("name",64));
  field_list.push_back(new Item_empty_string("description",1000));
  field_list.push_back(new Item_empty_string("example",1000));

  if (protocol->send_fields(&field_list,
                            Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
    DBUG_RETURN(1);

  protocol->prepare_for_resend();
  protocol->store(s1);
  protocol->store(s2);
  protocol->store(s3);
  if (protocol->write())
    DBUG_RETURN(-1);
  DBUG_RETURN(0);
}


/*
  Send to client help header

  SYNOPSIS
   send_header_2()
    protocol       - protocol for sending
    is_it_category - need column 'source_category_name'

  IMPLEMENTATION
   +-                    -+
   |+-------------------- | +----------+--------------+
   ||source_category_name | |name      |is_it_category|
   |+-------------------- | +----------+--------------+
   ||String(64)           | |String(64)|String(1)     |
   |+-------------------- | +----------+--------------+
   +-                    -+

  RETURN VALUES
    result of protocol->send_fields
*/

int send_header_2(Protocol *protocol, bool for_category)
{
  DBUG_ENTER("send_header_2");
  List<Item> field_list;
  if (for_category)
    field_list.push_back(new Item_empty_string("source_category_name",64));
  field_list.push_back(new Item_empty_string("name",64));
  field_list.push_back(new Item_empty_string("is_it_category",1));
  DBUG_RETURN(protocol->send_fields(&field_list, Protocol::SEND_NUM_ROWS |
                                                 Protocol::SEND_EOF));
}

/*
  strcmp for using in qsort

  SYNOPSIS
    strptrcmp()
    ptr1   (const void*)&str1
    ptr2   (const void*)&str2

  RETURN VALUES
    same as strcmp
*/

extern "C" int string_ptr_cmp(const void* ptr1, const void* ptr2)
{
  String *str1= *(String**)ptr1;
  String *str2= *(String**)ptr2;
  return strcmp(str1->c_ptr(),str2->c_ptr());
}

/*
  Send to client rows in format:
   column1 : <name>
   column2 : <is_it_category>

  SYNOPSIS
    send_variant_2_list()
    protocol     Protocol for sending
    names        List of names
    cat	         Value of the column <is_it_category>
    source_name  name of category for all items..

  RETURN VALUES
    -1 	Writing fail
    0	Data was successefully send
*/

int send_variant_2_list(MEM_ROOT *mem_root, Protocol *protocol,
			List<String> *names,
			const char *cat, String *source_name)
{
  DBUG_ENTER("send_variant_2_list");

  String **pointers= (String**)alloc_root(mem_root,
					  sizeof(String*)*names->elements);
  String **pos;
  String **end= pointers + names->elements;

  List_iterator<String> it(*names);
  for (pos= pointers; pos!=end; (*pos++= it++));

  qsort(pointers,names->elements,sizeof(String*),string_ptr_cmp);

  for (pos= pointers; pos!=end; pos++)
  {
    protocol->prepare_for_resend();
    if (source_name)
      protocol->store(source_name);
    protocol->store(*pos);
    protocol->store(cat,1,&my_charset_latin1);
    if (protocol->write())
      DBUG_RETURN(-1);
  }

  DBUG_RETURN(0);
}

/*
  Prepare simple SQL_SELECT table.* WHERE <Item>

  SYNOPSIS
    prepare_simple_select()
    thd      Thread handler
    cond     WHERE part of select
    table    goal table

    error    code of error (out)

  RETURN VALUES
    #  created SQL_SELECT
*/

SQL_SELECT *prepare_simple_select(THD *thd, Item *cond,
				  TABLE *table, int *error)
{
  if (!cond->fixed)
    cond->fix_fields(thd, &cond);	// can never fail

  /* Assume that no indexes cover all required fields */
  table->used_keys.clear_all();

  SQL_SELECT *res= make_select(table, 0, 0, cond, 0, error);
  if (*error || (res && res->check_quick(thd, 0, HA_POS_ERROR)) ||
      (res && res->quick && res->quick->reset()))
  {
    delete res;
    res=0;
  }
  return res;
}

/*
  Prepare simple SQL_SELECT table.* WHERE table.name LIKE mask

  SYNOPSIS
    prepare_select_for_name()
    thd      Thread handler
    mask     mask for compare with name
    mlen     length of mask
    tables   list of tables, used in WHERE
    table    goal table
    pfname   field "name" in table

    error    code of error (out)

  RETURN VALUES
    #  created SQL_SELECT
*/

SQL_SELECT *prepare_select_for_name(THD *thd, const char *mask, uint mlen,
				    TABLE_LIST *tables, TABLE *table,
				    Field *pfname, int *error)
{
  Item *cond= new Item_func_like(new Item_field(pfname),
				 new Item_string(mask,mlen,pfname->charset()),
				 new Item_string("\\",1,&my_charset_latin1),
                                 FALSE);
  if (thd->is_fatal_error)
    return 0;					// OOM
  return prepare_simple_select(thd, cond, table, error);
}


/*
  Server-side function 'help'

  SYNOPSIS
    mysqld_help()
    thd			Thread handler

  RETURN VALUES
    FALSE Success
    TRUE  Error and send_error already commited
*/

bool mysqld_help(THD *thd, const char *mask)
{
  Protocol *protocol= thd->protocol;
  SQL_SELECT *select;
  st_find_field used_fields[array_elements(init_used_fields)];
  TABLE_LIST *leaves= 0;
  TABLE_LIST tables[4];
  List<String> topics_list, categories_list, subcategories_list;
  String name, description, example;
  int count_topics, count_categories, error;
  uint mlen= strlen(mask);
  size_t i;
  MEM_ROOT *mem_root= thd->mem_root;
  DBUG_ENTER("mysqld_help");

  bzero((gptr)tables,sizeof(tables));
  tables[0].alias= tables[0].table_name= (char*) "help_topic";
  tables[0].lock_type= TL_READ;
  tables[0].next_global= tables[0].next_local= 
    tables[0].next_name_resolution_table= &tables[1];
  tables[1].alias= tables[1].table_name= (char*) "help_category";
  tables[1].lock_type= TL_READ;
  tables[1].next_global= tables[1].next_local= 
    tables[1].next_name_resolution_table= &tables[2];
  tables[2].alias= tables[2].table_name= (char*) "help_relation";
  tables[2].lock_type= TL_READ;
  tables[2].next_global= tables[2].next_local= 
    tables[2].next_name_resolution_table= &tables[3];
  tables[3].alias= tables[3].table_name= (char*) "help_keyword";
  tables[3].lock_type= TL_READ;
  tables[0].db= tables[1].db= tables[2].db= tables[3].db= (char*) "mysql";

  if (open_and_lock_tables(thd, tables))
    goto error;
  /*
    Init tables and fields to be usable from items
    tables do not contain VIEWs => we can pass 0 as conds
  */
  setup_tables(thd, &thd->lex->select_lex.context,
               &thd->lex->select_lex.top_join_list,
               tables, 0, &leaves, FALSE);
  memcpy((char*) used_fields, (char*) init_used_fields, sizeof(used_fields));
  if (init_fields(thd, tables, used_fields, array_elements(used_fields)))
    goto error;
  for (i=0; i<sizeof(tables)/sizeof(TABLE_LIST); i++)
    tables[i].table->file->init_table_handle_for_HANDLER();

  if (!(select=
	prepare_select_for_name(thd,mask,mlen,tables,tables[0].table,
				used_fields[help_topic_name].field,&error)))
    goto error;

  count_topics= search_topics(thd,tables[0].table,used_fields,
			      select,&topics_list,
			      &name, &description, &example);
  delete select;

  if (count_topics == 0)
  {
    int key_id;
    if (!(select=
          prepare_select_for_name(thd,mask,mlen,tables,tables[3].table,
                                  used_fields[help_keyword_name].field,&error)))
      goto error;

    count_topics=search_keyword(thd,tables[3].table,used_fields,select,&key_id);
    delete select;
    count_topics= (count_topics != 1) ? 0 :
                  get_topics_for_keyword(thd,tables[0].table,tables[2].table,
                                         used_fields,key_id,&topics_list,&name,
                                         &description,&example);
  }

  if (count_topics == 0)
  {
    int16 category_id;
    Field *cat_cat_id= used_fields[help_category_parent_category_id].field;
    if (!(select=
          prepare_select_for_name(thd,mask,mlen,tables,tables[1].table,
                                  used_fields[help_category_name].field,&error)))
      goto error;

    count_categories= search_categories(thd, tables[1].table, used_fields,
					select,
					&categories_list,&category_id);
    delete select;
    if (!count_categories)
    {
      if (send_header_2(protocol,FALSE))
	goto error;
    }
    else if (count_categories > 1)
    {
      if (send_header_2(protocol,FALSE) ||
	  send_variant_2_list(mem_root,protocol,&categories_list,"Y",0))
	goto error;
    }
    else
    {
      Field *topic_cat_id= used_fields[help_topic_help_category_id].field;
      Item *cond_topic_by_cat=
	new Item_func_equal(new Item_field(topic_cat_id),
			    new Item_int((int32)category_id));
      Item *cond_cat_by_cat=
	new Item_func_equal(new Item_field(cat_cat_id),
			    new Item_int((int32)category_id));
      if (!(select= prepare_simple_select(thd, cond_topic_by_cat,
                                          tables[0].table, &error)))
        goto error;
      get_all_items_for_category(thd,tables[0].table,
				 used_fields[help_topic_name].field,
				 select,&topics_list);
      delete select;
      if (!(select= prepare_simple_select(thd, cond_cat_by_cat,
                                          tables[1].table, &error)))
        goto error;
      get_all_items_for_category(thd,tables[1].table,
				 used_fields[help_category_name].field,
				 select,&subcategories_list);
      delete select;
      String *cat= categories_list.head();
      if (send_header_2(protocol, TRUE) ||
	  send_variant_2_list(mem_root,protocol,&topics_list,       "N",cat) ||
	  send_variant_2_list(mem_root,protocol,&subcategories_list,"Y",cat))
	goto error;
    }
  }
  else if (count_topics == 1)
  {
    if (send_answer_1(protocol,&name,&description,&example))
      goto error;
  }
  else
  {
    /* First send header and functions */
    if (send_header_2(protocol, FALSE) ||
	send_variant_2_list(mem_root,protocol, &topics_list, "N", 0))
      goto error;
    if (!(select=
          prepare_select_for_name(thd,mask,mlen,tables,tables[1].table,
                                  used_fields[help_category_name].field,&error)))
      goto error;
    search_categories(thd, tables[1].table, used_fields,
		      select,&categories_list, 0);
    delete select;
    /* Then send categories */
    if (send_variant_2_list(mem_root,protocol, &categories_list, "Y", 0))
      goto error;
  }
  send_eof(thd);

  DBUG_RETURN(FALSE);
error:
  DBUG_RETURN(TRUE);
}