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1 /* query.cc - Support for searching a notmuch database
2  *
3  * Copyright © 2009 Carl Worth
4  *
5  * This program is free software: you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation, either version 3 of the License, or
8  * (at your option) any later version.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program.  If not, see https://www.gnu.org/licenses/ .
17  *
18  * Author: Carl Worth <cworth@cworth.org>
19  */
20
21 #include "notmuch-private.h"
22 #include "database-private.h"
23
24 #include <glib.h> /* GHashTable, GPtrArray */
25
26 struct _notmuch_query {
27     notmuch_database_t *notmuch;
28     const char *query_string;
29     notmuch_sort_t sort;
30     notmuch_string_list_t *exclude_terms;
31     notmuch_exclude_t omit_excluded;
32     bool parsed;
33     notmuch_query_syntax_t syntax;
34     Xapian::Query xapian_query;
35     std::set<std::string> terms;
36 };
37
38 typedef struct _notmuch_mset_messages {
39     notmuch_messages_t base;
40     notmuch_database_t *notmuch;
41     Xapian::MSetIterator iterator;
42     Xapian::MSetIterator iterator_end;
43 } notmuch_mset_messages_t;
44
45 struct _notmuch_doc_id_set {
46     unsigned char *bitmap;
47     unsigned int bound;
48 };
49
50 #define DOCIDSET_WORD(bit) ((bit) / CHAR_BIT)
51 #define DOCIDSET_BIT(bit) ((bit) % CHAR_BIT)
52
53 struct _notmuch_threads {
54     notmuch_query_t *query;
55
56     /* The ordered list of doc ids matched by the query. */
57     GArray *doc_ids;
58     /* Our iterator's current position in doc_ids. */
59     unsigned int doc_id_pos;
60     /* The set of matched docid's that have not been assigned to a
61      * thread. Initially, this contains every docid in doc_ids. */
62     notmuch_doc_id_set_t match_set;
63 };
64
65 /* We need this in the message functions so forward declare. */
66 static bool
67 _notmuch_doc_id_set_init (void *ctx,
68                           notmuch_doc_id_set_t *doc_ids,
69                           GArray *arr);
70
71 static bool
72 _debug_query (void)
73 {
74     char *env = getenv ("NOTMUCH_DEBUG_QUERY");
75
76     return (env && strcmp (env, "") != 0);
77 }
78
79 /* Explicit destructor call for placement new */
80 static int
81 _notmuch_query_destructor (notmuch_query_t *query)
82 {
83     query->xapian_query.~Query();
84     query->terms.~set<std::string>();
85     return 0;
86 }
87
88 static notmuch_query_t *
89 _notmuch_query_constructor (notmuch_database_t *notmuch,
90                             const char *query_string)
91 {
92     notmuch_query_t *query;
93
94     if (_debug_query ())
95         fprintf (stderr, "Query string is:\n%s\n", query_string);
96
97     query = talloc (notmuch, notmuch_query_t);
98     if (unlikely (query == NULL))
99         return NULL;
100
101     new (&query->xapian_query) Xapian::Query ();
102     new (&query->terms) std::set<std::string> ();
103     query->parsed = false;
104
105     talloc_set_destructor (query, _notmuch_query_destructor);
106
107     query->notmuch = notmuch;
108
109     if (query_string)
110         query->query_string = talloc_strdup (query, query_string);
111     else
112         query->query_string = NULL;
113
114     query->sort = NOTMUCH_SORT_NEWEST_FIRST;
115
116     query->exclude_terms = _notmuch_string_list_create (query);
117
118     query->omit_excluded = NOTMUCH_EXCLUDE_TRUE;
119
120     return query;
121 }
122
123 notmuch_query_t *
124 notmuch_query_create (notmuch_database_t *notmuch,
125                       const char *query_string)
126 {
127
128     notmuch_query_t *query;
129     notmuch_status_t status;
130
131     status = notmuch_query_create_with_syntax (notmuch, query_string,
132                                                NOTMUCH_QUERY_SYNTAX_XAPIAN,
133                                                &query);
134     if (status)
135         return NULL;
136
137     return query;
138 }
139
140 notmuch_status_t
141 notmuch_query_create_with_syntax (notmuch_database_t *notmuch,
142                                   const char *query_string,
143                                   notmuch_query_syntax_t syntax,
144                                   notmuch_query_t **output)
145 {
146
147     notmuch_query_t *query;
148
149     if (! output)
150         return NOTMUCH_STATUS_NULL_POINTER;
151
152     query = _notmuch_query_constructor (notmuch, query_string);
153     if (! query)
154         return NOTMUCH_STATUS_OUT_OF_MEMORY;
155
156     if (syntax == NOTMUCH_QUERY_SYNTAX_SEXP && ! HAVE_SFSEXP) {
157         _notmuch_database_log (notmuch, "sexp query parser not available");
158         return NOTMUCH_STATUS_ILLEGAL_ARGUMENT;
159     }
160
161     query->syntax = syntax;
162
163     *output = query;
164
165     return NOTMUCH_STATUS_SUCCESS;
166 }
167
168 static void
169 _notmuch_query_cache_terms (notmuch_query_t *query)
170 {
171     /* Xapian doesn't support skip_to on terms from a query since
172      *  they are unordered, so cache a copy of all terms in
173      *  something searchable.
174      */
175
176     for (Xapian::TermIterator t = query->xapian_query.get_terms_begin ();
177          t != query->xapian_query.get_terms_end (); ++t)
178         query->terms.insert (*t);
179 }
180
181 notmuch_status_t
182 _notmuch_query_string_to_xapian_query (notmuch_database_t *notmuch,
183                                        std::string query_string,
184                                        Xapian::Query &output,
185                                        std::string &msg)
186 {
187     try {
188         if (query_string == "" || query_string == "*") {
189             output = Xapian::Query::MatchAll;
190         } else {
191             output =
192                 notmuch->query_parser->
193                 parse_query (query_string, NOTMUCH_QUERY_PARSER_FLAGS);
194         }
195     } catch (const Xapian::Error &error) {
196         if (! notmuch->exception_reported) {
197             _notmuch_database_log (notmuch,
198                                    "A Xapian exception occurred parsing query: %s\n",
199                                    error.get_msg ().c_str ());
200             _notmuch_database_log_append (notmuch,
201                                           "Query string was: %s\n",
202                                           query_string.c_str ());
203             notmuch->exception_reported = true;
204         }
205
206         msg = error.get_msg ();
207         return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
208     }
209     return NOTMUCH_STATUS_SUCCESS;
210 }
211
212 static notmuch_status_t
213 _notmuch_query_ensure_parsed_xapian (notmuch_query_t *query)
214 {
215     notmuch_status_t status;
216     std::string msg; /* ignored */
217
218     status =  _notmuch_query_string_to_xapian_query (query->notmuch, query->query_string,
219                                                      query->xapian_query, msg);
220     if (status)
221         return status;
222
223     query->parsed = true;
224
225     _notmuch_query_cache_terms (query);
226
227     return NOTMUCH_STATUS_SUCCESS;
228 }
229
230 static notmuch_status_t
231 _notmuch_query_ensure_parsed_sexpr (notmuch_query_t *query)
232 {
233     notmuch_status_t status;
234
235     if (query->parsed)
236         return NOTMUCH_STATUS_SUCCESS;
237
238     status = _notmuch_sexp_string_to_xapian_query (query->notmuch, query->query_string,
239                                                    query->xapian_query);
240     if (status)
241         return status;
242
243     _notmuch_query_cache_terms (query);
244     return NOTMUCH_STATUS_SUCCESS;
245 }
246
247 static notmuch_status_t
248 _notmuch_query_ensure_parsed (notmuch_query_t *query)
249 {
250     if (query->parsed)
251         return NOTMUCH_STATUS_SUCCESS;
252
253 #if HAVE_SFSEXP
254     if (query->syntax == NOTMUCH_QUERY_SYNTAX_SEXP)
255         return _notmuch_query_ensure_parsed_sexpr (query);
256 #endif
257
258     return _notmuch_query_ensure_parsed_xapian (query);
259 }
260
261 const char *
262 notmuch_query_get_query_string (const notmuch_query_t *query)
263 {
264     return query->query_string;
265 }
266
267 void
268 notmuch_query_set_omit_excluded (notmuch_query_t *query,
269                                  notmuch_exclude_t omit_excluded)
270 {
271     query->omit_excluded = omit_excluded;
272 }
273
274 void
275 notmuch_query_set_sort (notmuch_query_t *query, notmuch_sort_t sort)
276 {
277     query->sort = sort;
278 }
279
280 notmuch_sort_t
281 notmuch_query_get_sort (const notmuch_query_t *query)
282 {
283     return query->sort;
284 }
285
286 notmuch_status_t
287 notmuch_query_add_tag_exclude (notmuch_query_t *query, const char *tag)
288 {
289     notmuch_status_t status;
290     char *term;
291
292     status = _notmuch_query_ensure_parsed (query);
293     if (status)
294         return status;
295
296     term = talloc_asprintf (query, "%s%s", _find_prefix ("tag"), tag);
297     if (query->terms.count (term) != 0)
298         return NOTMUCH_STATUS_IGNORED;
299
300     _notmuch_string_list_append (query->exclude_terms, term);
301     return NOTMUCH_STATUS_SUCCESS;
302 }
303
304 /* We end up having to call the destructors explicitly because we had
305  * to use "placement new" in order to initialize C++ objects within a
306  * block that we allocated with talloc. So C++ is making talloc
307  * slightly less simple to use, (we wouldn't need
308  * talloc_set_destructor at all otherwise).
309  */
310 static int
311 _notmuch_messages_destructor (notmuch_mset_messages_t *messages)
312 {
313     messages->iterator.~MSetIterator ();
314     messages->iterator_end.~MSetIterator ();
315
316     return 0;
317 }
318
319 /* Return a query that matches messages with the excluded tags
320  * registered with query. The caller of this function has to combine the returned
321  * query appropriately.*/
322 static Xapian::Query
323 _notmuch_exclude_tags (notmuch_query_t *query)
324 {
325     Xapian::Query exclude_query = Xapian::Query::MatchNothing;
326
327     for (notmuch_string_node_t *term = query->exclude_terms->head; term;
328          term = term->next) {
329         exclude_query = Xapian::Query (Xapian::Query::OP_OR,
330                                        exclude_query, Xapian::Query (term->string));
331     }
332     return exclude_query;
333 }
334
335
336 notmuch_status_t
337 notmuch_query_search_messages_st (notmuch_query_t *query,
338                                   notmuch_messages_t **out)
339 {
340     return notmuch_query_search_messages (query, out);
341 }
342
343 notmuch_status_t
344 notmuch_query_search_messages (notmuch_query_t *query,
345                                notmuch_messages_t **out)
346 {
347     return _notmuch_query_search_documents (query, "mail", out);
348 }
349
350 notmuch_status_t
351 _notmuch_query_search_documents (notmuch_query_t *query,
352                                  const char *type,
353                                  notmuch_messages_t **out)
354 {
355     notmuch_database_t *notmuch = query->notmuch;
356     notmuch_mset_messages_t *messages;
357     notmuch_status_t status;
358
359     status = _notmuch_query_ensure_parsed (query);
360     if (status)
361         return status;
362
363     messages = talloc (query, notmuch_mset_messages_t);
364     if (unlikely (messages == NULL))
365         return NOTMUCH_STATUS_OUT_OF_MEMORY;
366
367     try {
368
369         messages->base.is_of_list_type = false;
370         messages->base.iterator = NULL;
371         messages->notmuch = notmuch;
372         new (&messages->iterator) Xapian::MSetIterator ();
373         new (&messages->iterator_end) Xapian::MSetIterator ();
374
375         talloc_set_destructor (messages, _notmuch_messages_destructor);
376
377         Xapian::Enquire enquire (*notmuch->xapian_db);
378         Xapian::Query mail_query (talloc_asprintf (query, "%s%s",
379                                                    _find_prefix ("type"),
380                                                    type));
381         Xapian::Query final_query, exclude_query;
382         Xapian::MSet mset;
383         Xapian::MSetIterator iterator;
384
385         final_query = Xapian::Query (Xapian::Query::OP_AND,
386                                      mail_query, query->xapian_query);
387
388         messages->base.excluded_doc_ids = NULL;
389
390         if ((query->omit_excluded != NOTMUCH_EXCLUDE_FALSE) && (query->exclude_terms)) {
391             exclude_query = _notmuch_exclude_tags (query);
392
393             if (query->omit_excluded == NOTMUCH_EXCLUDE_TRUE ||
394                 query->omit_excluded == NOTMUCH_EXCLUDE_ALL) {
395                 final_query = Xapian::Query (Xapian::Query::OP_AND_NOT,
396                                              final_query, exclude_query);
397             } else { /* NOTMUCH_EXCLUDE_FLAG */
398                 exclude_query = Xapian::Query (Xapian::Query::OP_AND,
399                                                exclude_query, final_query);
400
401                 enquire.set_weighting_scheme (Xapian::BoolWeight ());
402                 enquire.set_query (exclude_query);
403
404                 mset = enquire.get_mset (0, notmuch->xapian_db->get_doccount ());
405
406                 GArray *excluded_doc_ids = g_array_new (false, false, sizeof (unsigned int));
407
408                 for (iterator = mset.begin (); iterator != mset.end (); iterator++) {
409                     unsigned int doc_id = *iterator;
410                     g_array_append_val (excluded_doc_ids, doc_id);
411                 }
412                 messages->base.excluded_doc_ids = talloc (messages, _notmuch_doc_id_set);
413                 _notmuch_doc_id_set_init (query, messages->base.excluded_doc_ids,
414                                           excluded_doc_ids);
415                 g_array_unref (excluded_doc_ids);
416             }
417         }
418
419
420         enquire.set_weighting_scheme (Xapian::BoolWeight ());
421
422         switch (query->sort) {
423         case NOTMUCH_SORT_OLDEST_FIRST:
424             enquire.set_sort_by_value (NOTMUCH_VALUE_TIMESTAMP, false);
425             break;
426         case NOTMUCH_SORT_NEWEST_FIRST:
427             enquire.set_sort_by_value (NOTMUCH_VALUE_TIMESTAMP, true);
428             break;
429         case NOTMUCH_SORT_MESSAGE_ID:
430             enquire.set_sort_by_value (NOTMUCH_VALUE_MESSAGE_ID, false);
431             break;
432         case NOTMUCH_SORT_UNSORTED:
433             break;
434         }
435
436         if (_debug_query ()) {
437             fprintf (stderr, "Exclude query is:\n%s\n",
438                      exclude_query.get_description ().c_str ());
439             fprintf (stderr, "Final query is:\n%s\n",
440                      final_query.get_description ().c_str ());
441         }
442
443         enquire.set_query (final_query);
444
445         mset = enquire.get_mset (0, notmuch->xapian_db->get_doccount ());
446
447         messages->iterator = mset.begin ();
448         messages->iterator_end = mset.end ();
449
450         *out = &messages->base;
451         return NOTMUCH_STATUS_SUCCESS;
452
453     } catch (const Xapian::Error &error) {
454         _notmuch_database_log (notmuch,
455                                "A Xapian exception occurred performing query: %s\n",
456                                error.get_msg ().c_str ());
457         _notmuch_database_log_append (notmuch,
458                                       "Query string was: %s\n",
459                                       query->query_string);
460
461         notmuch->exception_reported = true;
462         talloc_free (messages);
463         return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
464     }
465 }
466
467 bool
468 _notmuch_mset_messages_valid (notmuch_messages_t *messages)
469 {
470     notmuch_mset_messages_t *mset_messages;
471
472     mset_messages = (notmuch_mset_messages_t *) messages;
473
474     return (mset_messages->iterator != mset_messages->iterator_end);
475 }
476
477 static Xapian::docid
478 _notmuch_mset_messages_get_doc_id (notmuch_messages_t *messages)
479 {
480     notmuch_mset_messages_t *mset_messages;
481
482     mset_messages = (notmuch_mset_messages_t *) messages;
483
484     if (! _notmuch_mset_messages_valid (&mset_messages->base))
485         return 0;
486
487     return *mset_messages->iterator;
488 }
489
490 notmuch_message_t *
491 _notmuch_mset_messages_get (notmuch_messages_t *messages)
492 {
493     notmuch_message_t *message;
494     Xapian::docid doc_id;
495     notmuch_private_status_t status;
496     notmuch_mset_messages_t *mset_messages;
497
498     mset_messages = (notmuch_mset_messages_t *) messages;
499
500     if (! _notmuch_mset_messages_valid (&mset_messages->base))
501         return NULL;
502
503     doc_id = *mset_messages->iterator;
504
505     message = _notmuch_message_create (mset_messages,
506                                        mset_messages->notmuch, doc_id,
507                                        &status);
508
509     if (message == NULL &&
510         status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND) {
511         INTERNAL_ERROR ("a messages iterator contains a non-existent document ID.\n");
512     }
513
514     if (messages->excluded_doc_ids &&
515         _notmuch_doc_id_set_contains (messages->excluded_doc_ids, doc_id))
516         notmuch_message_set_flag (message, NOTMUCH_MESSAGE_FLAG_EXCLUDED, true);
517
518     return message;
519 }
520
521 void
522 _notmuch_mset_messages_move_to_next (notmuch_messages_t *messages)
523 {
524     notmuch_mset_messages_t *mset_messages;
525
526     mset_messages = (notmuch_mset_messages_t *) messages;
527
528     mset_messages->iterator++;
529 }
530
531 static bool
532 _notmuch_doc_id_set_init (void *ctx,
533                           notmuch_doc_id_set_t *doc_ids,
534                           GArray *arr)
535 {
536     unsigned int max = 0;
537     unsigned char *bitmap;
538
539     for (unsigned int i = 0; i < arr->len; i++)
540         max = MAX (max, g_array_index (arr, unsigned int, i));
541     bitmap = talloc_zero_array (ctx, unsigned char, DOCIDSET_WORD (max) + 1);
542
543     if (bitmap == NULL)
544         return false;
545
546     doc_ids->bitmap = bitmap;
547     doc_ids->bound = max + 1;
548
549     for (unsigned int i = 0; i < arr->len; i++) {
550         unsigned int doc_id = g_array_index (arr, unsigned int, i);
551         bitmap[DOCIDSET_WORD (doc_id)] |= 1 << DOCIDSET_BIT (doc_id);
552     }
553
554     return true;
555 }
556
557 bool
558 _notmuch_doc_id_set_contains (notmuch_doc_id_set_t *doc_ids,
559                               unsigned int doc_id)
560 {
561     if (doc_id >= doc_ids->bound)
562         return false;
563     return doc_ids->bitmap[DOCIDSET_WORD (doc_id)] & (1 << DOCIDSET_BIT (doc_id));
564 }
565
566 void
567 _notmuch_doc_id_set_remove (notmuch_doc_id_set_t *doc_ids,
568                             unsigned int doc_id)
569 {
570     if (doc_id < doc_ids->bound)
571         doc_ids->bitmap[DOCIDSET_WORD (doc_id)] &= ~(1 << DOCIDSET_BIT (doc_id));
572 }
573
574 /* Glib objects force use to use a talloc destructor as well, (but not
575  * nearly as ugly as the for messages due to C++ objects). At
576  * this point, I'd really like to have some talloc-friendly
577  * equivalents for the few pieces of glib that I'm using. */
578 static int
579 _notmuch_threads_destructor (notmuch_threads_t *threads)
580 {
581     if (threads->doc_ids)
582         g_array_unref (threads->doc_ids);
583
584     return 0;
585 }
586
587 notmuch_status_t
588 notmuch_query_search_threads_st (notmuch_query_t *query, notmuch_threads_t **out)
589 {
590     return notmuch_query_search_threads (query, out);
591 }
592
593 notmuch_status_t
594 notmuch_query_search_threads (notmuch_query_t *query,
595                               notmuch_threads_t **out)
596 {
597     notmuch_threads_t *threads;
598     notmuch_messages_t *messages;
599     notmuch_status_t status;
600
601     threads = talloc (query, notmuch_threads_t);
602     if (threads == NULL)
603         return NOTMUCH_STATUS_OUT_OF_MEMORY;
604     threads->doc_ids = NULL;
605     talloc_set_destructor (threads, _notmuch_threads_destructor);
606
607     threads->query = query;
608
609     status = notmuch_query_search_messages (query, &messages);
610     if (status) {
611         talloc_free (threads);
612         return status;
613     }
614
615     threads->doc_ids = g_array_new (false, false, sizeof (unsigned int));
616     while (notmuch_messages_valid (messages)) {
617         unsigned int doc_id = _notmuch_mset_messages_get_doc_id (messages);
618         g_array_append_val (threads->doc_ids, doc_id);
619         notmuch_messages_move_to_next (messages);
620     }
621     threads->doc_id_pos = 0;
622
623     talloc_free (messages);
624
625     if (! _notmuch_doc_id_set_init (threads, &threads->match_set,
626                                     threads->doc_ids)) {
627         talloc_free (threads);
628         return NOTMUCH_STATUS_OUT_OF_MEMORY;
629     }
630
631     *out = threads;
632     return NOTMUCH_STATUS_SUCCESS;
633 }
634
635 void
636 notmuch_query_destroy (notmuch_query_t *query)
637 {
638     talloc_free (query);
639 }
640
641 notmuch_bool_t
642 notmuch_threads_valid (notmuch_threads_t *threads)
643 {
644     unsigned int doc_id;
645
646     if (! threads)
647         return false;
648
649     while (threads->doc_id_pos < threads->doc_ids->len) {
650         doc_id = g_array_index (threads->doc_ids, unsigned int,
651                                 threads->doc_id_pos);
652         if (_notmuch_doc_id_set_contains (&threads->match_set, doc_id))
653             break;
654
655         threads->doc_id_pos++;
656     }
657
658     return threads->doc_id_pos < threads->doc_ids->len;
659 }
660
661 notmuch_thread_t *
662 notmuch_threads_get (notmuch_threads_t *threads)
663 {
664     unsigned int doc_id;
665
666     if (! notmuch_threads_valid (threads))
667         return NULL;
668
669     doc_id = g_array_index (threads->doc_ids, unsigned int,
670                             threads->doc_id_pos);
671     return _notmuch_thread_create (threads->query,
672                                    threads->query->notmuch,
673                                    doc_id,
674                                    &threads->match_set,
675                                    threads->query->exclude_terms,
676                                    threads->query->omit_excluded,
677                                    threads->query->sort);
678 }
679
680 void
681 notmuch_threads_move_to_next (notmuch_threads_t *threads)
682 {
683     threads->doc_id_pos++;
684 }
685
686 void
687 notmuch_threads_destroy (notmuch_threads_t *threads)
688 {
689     talloc_free (threads);
690 }
691
692 notmuch_status_t
693 notmuch_query_count_messages_st (notmuch_query_t *query, unsigned *count_out)
694 {
695     return notmuch_query_count_messages (query, count_out);
696 }
697
698 notmuch_status_t
699 notmuch_query_count_messages (notmuch_query_t *query, unsigned *count_out)
700 {
701     return _notmuch_query_count_documents (query, "mail", count_out);
702 }
703
704 notmuch_status_t
705 _notmuch_query_count_documents (notmuch_query_t *query, const char *type, unsigned *count_out)
706 {
707     notmuch_database_t *notmuch = query->notmuch;
708     Xapian::doccount count = 0;
709     notmuch_status_t status;
710
711     status = _notmuch_query_ensure_parsed (query);
712     if (status)
713         return status;
714
715     try {
716         Xapian::Enquire enquire (*notmuch->xapian_db);
717         Xapian::Query mail_query (talloc_asprintf (query, "%s%s",
718                                                    _find_prefix ("type"),
719                                                    type));
720         Xapian::Query final_query, exclude_query;
721         Xapian::MSet mset;
722
723         final_query = Xapian::Query (Xapian::Query::OP_AND,
724                                      mail_query, query->xapian_query);
725
726         exclude_query = _notmuch_exclude_tags (query);
727
728         final_query = Xapian::Query (Xapian::Query::OP_AND_NOT,
729                                      final_query, exclude_query);
730
731         enquire.set_weighting_scheme (Xapian::BoolWeight ());
732         enquire.set_docid_order (Xapian::Enquire::ASCENDING);
733
734         if (_debug_query ()) {
735             fprintf (stderr, "Exclude query is:\n%s\n",
736                      exclude_query.get_description ().c_str ());
737             fprintf (stderr, "Final query is:\n%s\n",
738                      final_query.get_description ().c_str ());
739         }
740
741         enquire.set_query (final_query);
742
743         /*
744          * Set the checkatleast parameter to the number of documents
745          * in the database to make get_matches_estimated() exact.
746          * Set the max parameter to 1 to avoid fetching documents we will discard.
747          */
748         mset = enquire.get_mset (0, 1,
749                                  notmuch->xapian_db->get_doccount ());
750
751         count = mset.get_matches_estimated ();
752
753     } catch (const Xapian::Error &error) {
754         _notmuch_database_log (notmuch,
755                                "A Xapian exception occurred performing query: %s\n",
756                                error.get_msg ().c_str ());
757         _notmuch_database_log_append (notmuch,
758                                       "Query string was: %s\n",
759                                       query->query_string);
760         return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
761     }
762
763     *count_out = count;
764     return NOTMUCH_STATUS_SUCCESS;
765 }
766
767 notmuch_status_t
768 notmuch_query_count_threads_st (notmuch_query_t *query, unsigned *count)
769 {
770     return notmuch_query_count_threads (query, count);
771 }
772
773 notmuch_status_t
774 notmuch_query_count_threads (notmuch_query_t *query, unsigned *count)
775 {
776     notmuch_messages_t *messages;
777     GHashTable *hash;
778     notmuch_sort_t sort;
779     notmuch_status_t ret = NOTMUCH_STATUS_SUCCESS;
780
781     sort = query->sort;
782     query->sort = NOTMUCH_SORT_UNSORTED;
783     ret = notmuch_query_search_messages (query, &messages);
784     if (ret)
785         return ret;
786     query->sort = sort;
787     if (messages == NULL)
788         return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
789
790     hash = g_hash_table_new_full (g_str_hash, g_str_equal, NULL, NULL);
791     if (hash == NULL) {
792         talloc_free (messages);
793         return NOTMUCH_STATUS_OUT_OF_MEMORY;
794     }
795
796     while (notmuch_messages_valid (messages)) {
797         notmuch_message_t *message = notmuch_messages_get (messages);
798         const char *thread_id = notmuch_message_get_thread_id (message);
799         char *thread_id_copy = talloc_strdup (messages, thread_id);
800         if (unlikely (thread_id_copy == NULL)) {
801             notmuch_message_destroy (message);
802             ret = NOTMUCH_STATUS_OUT_OF_MEMORY;
803             goto DONE;
804         }
805         g_hash_table_insert (hash, thread_id_copy, NULL);
806         notmuch_message_destroy (message);
807         notmuch_messages_move_to_next (messages);
808     }
809
810     *count = g_hash_table_size (hash);
811
812   DONE:
813     g_hash_table_unref (hash);
814     talloc_free (messages);
815
816     return ret;
817 }
818
819 notmuch_database_t *
820 notmuch_query_get_database (const notmuch_query_t *query)
821 {
822     return query->notmuch;
823 }
824
825 notmuch_status_t
826 _notmuch_query_expand (notmuch_database_t *notmuch, const char *field, Xapian::Query subquery,
827                        Xapian::Query &output, std::string &msg)
828 {
829     std::set<std::string> terms;
830     const std::string term_prefix =  _find_prefix (field);
831
832     if (_debug_query ()) {
833         fprintf (stderr, "Expanding subquery:\n%s\n",
834                  subquery.get_description ().c_str ());
835     }
836
837     try {
838         Xapian::Enquire enquire (*notmuch->xapian_db);
839         Xapian::MSet mset;
840
841         enquire.set_weighting_scheme (Xapian::BoolWeight ());
842         enquire.set_query (subquery);
843
844         mset = enquire.get_mset (0, notmuch->xapian_db->get_doccount ());
845
846         for (Xapian::MSetIterator iterator = mset.begin (); iterator != mset.end (); iterator++) {
847             Xapian::docid doc_id = *iterator;
848             Xapian::Document doc = notmuch->xapian_db->get_document (doc_id);
849             Xapian::TermIterator i = doc.termlist_begin ();
850
851             for (i.skip_to (term_prefix);
852                  i != doc.termlist_end () && ((*i).rfind (term_prefix, 0) == 0); i++) {
853                 terms.insert (*i);
854             }
855         }
856         output = Xapian::Query (Xapian::Query::OP_OR, terms.begin (), terms.end ());
857         if (_debug_query ()) {
858             fprintf (stderr, "Expanded query:\n%s\n",
859                      subquery.get_description ().c_str ());
860         }
861
862     } catch (const Xapian::Error &error) {
863         _notmuch_database_log (notmuch,
864                                "A Xapian exception occurred expanding query: %s\n",
865                                error.get_msg ().c_str ());
866         msg = error.get_msg ();
867         return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
868     }
869
870     return NOTMUCH_STATUS_SUCCESS;
871 }