xapian-core/backends/database.cc

   1 /* database.cc: Database::Internal base class.
   2  *
   3  * Copyright 1999,2000,2001 BrightStation PLC
   4  * Copyright 2002 Ananova Ltd
   5  * Copyright 2002,2003,2004,2005,2006,2007,2008,2009,2011,2014,2016 Olly Betts
   6  * Copyright 2008 Lemur Consulting Ltd
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of the
  11  * License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  21  * USA
  22  */
  23
  24 #include <config.h>
  25
  26 #include "database.h"
  27
  28 #include "xapian/error.h"
  29
  30 #include "api/leafpostlist.h"
  31 #include "omassert.h"
  32 #include "slowvaluelist.h"
  33
  34 #include <algorithm>
  35 #include <string>
  36
  37 using namespace std;
  38 using Xapian::Internal::intrusive_ptr;
  39
  40 namespace Xapian {
  41
  42 Database::Internal::~Internal()
  43 {
  44 }
  45
  46 void
  47 Database::Internal::keep_alive()
  48 {
  49     // For the normal case of local databases, nothing needs to be done.
  50 }
  51
  52
  53 void
  54 Database::Internal::readahead_for_query(const Xapian::Query &)
  55 {
  56 }
  57
  58 Xapian::termcount
  59 Database::Internal::get_doclength_lower_bound() const
  60 {
  61     // A zero-length document can't contain any terms, so we ignore such
  62     // documents for the purposes of this lower bound.
  63     return 1;
  64 }
  65
  66 Xapian::termcount
  67 Database::Internal::get_doclength_upper_bound() const
  68 {
  69     // Not a very tight bound in general, but this is only a fall-back for
  70     // backends which don't store these stats.
  71     return min(get_total_length(), Xapian::totallength(Xapian::termcount(-1)));
  72 }
  73
  74 Xapian::termcount
  75 Database::Internal::get_wdf_upper_bound(const string & term) const
  76 {
  77     // Not a very tight bound in general, but this is only a fall-back for
  78     // backends which don't store these stats.
  79     Xapian::termcount cf;
  80     get_freqs(term, NULL, &cf);
  81     return cf;
  82 }
  83
  84 // Discard any exceptions - we're called from the destructors of derived
  85 // classes so we can't safely throw.
  86 void
  87 Database::Internal::dtor_called()
  88 {
  89     try {
  90         if (transaction_active()) {
  91             cancel_transaction();
  92         } else if (transaction_state == TRANSACTION_NONE) {
  93             commit();
  94         }
  95     } catch (...) {
  96         // We can't safely throw exceptions from a destructor in case an
  97         // exception is already active and causing us to be destroyed.
  98     }
  99 }
 100
 101 void
 102 Database::Internal::commit()
 103 {
 104     // Writable databases should override this method.
 105     Assert(false);
 106 }
 107
 108 void
 109 Database::Internal::cancel()
 110 {
 111     // Writable databases should override this method.
 112     Assert(false);
 113 }
 114
 115 void
 116 Database::Internal::begin_transaction(bool flushed)
 117 {
 118     if (transaction_state != TRANSACTION_NONE) {
 119         if (transaction_state == TRANSACTION_UNIMPLEMENTED)
 120             throw Xapian::UnimplementedError("This backend doesn't implement transactions");
 121         throw InvalidOperationError("Cannot begin transaction - transaction already in progress");
 122     }
 123     if (flushed) {
 124         // N.B. Call commit() before we set transaction_state since commit()
 125         // isn't allowing during a transaction.
 126         commit();
 127         transaction_state = TRANSACTION_FLUSHED;
 128     } else {
 129         transaction_state = TRANSACTION_UNFLUSHED;
 130     }
 131 }
 132
 133 void
 134 Database::Internal::commit_transaction()
 135 {
 136     if (!transaction_active()) {
 137         if (transaction_state == TRANSACTION_UNIMPLEMENTED)
 138             throw Xapian::UnimplementedError("This backend doesn't implement transactions");
 139         throw InvalidOperationError("Cannot commit transaction - no transaction currently in progress");
 140     }
 141     bool flushed = (transaction_state == TRANSACTION_FLUSHED);
 142     transaction_state = TRANSACTION_NONE;
 143     // N.B. Call commit() after we clear transaction_state since commit()
 144     // isn't allowing during a transaction.
 145     if (flushed) commit();
 146 }
 147
 148 void
 149 Database::Internal::cancel_transaction()
 150 {
 151     if (!transaction_active()) {
 152         if (transaction_state == TRANSACTION_UNIMPLEMENTED)
 153             throw Xapian::UnimplementedError("This backend doesn't implement transactions");
 154         throw InvalidOperationError("Cannot cancel transaction - no transaction currently in progress");
 155     }
 156     transaction_state = TRANSACTION_NONE;
 157     cancel();
 158 }
 159
 160 Xapian::docid
 161 Database::Internal::add_document(const Xapian::Document &)
 162 {
 163     // Writable databases should override this method.
 164     Assert(false);
 165     return 0;
 166 }
 167
 168 void
 169 Database::Internal::delete_document(Xapian::docid)
 170 {
 171     // Writable databases should override this method.
 172     Assert(false);
 173 }
 174
 175 void
 176 Database::Internal::delete_document(const string & unique_term)
 177 {
 178     // Default implementation - overridden for remote databases
 179     intrusive_ptr<LeafPostList> pl(open_post_list(unique_term));
 180     while (pl->next(), !pl->at_end()) {
 181         delete_document(pl->get_docid());
 182     }
 183 }
 184
 185 void
 186 Database::Internal::replace_document(Xapian::docid, const Xapian::Document &)
 187 {
 188     // Writable databases should override this method.
 189     Assert(false);
 190 }
 191
 192 Xapian::docid
 193 Database::Internal::replace_document(const string & unique_term,
 194                                      const Xapian::Document & document)
 195 {
 196     // Default implementation - overridden for remote databases
 197     intrusive_ptr<LeafPostList> pl(open_post_list(unique_term));
 198     pl->next();
 199     if (pl->at_end()) {
 200         return add_document(document);
 201     }
 202     Xapian::docid did = pl->get_docid();
 203     replace_document(did, document);
 204     while (pl->next(), !pl->at_end()) {
 205         delete_document(pl->get_docid());
 206     }
 207     return did;
 208 }
 209
 210 ValueList *
 211 Database::Internal::open_value_list(Xapian::valueno slot) const
 212 {
 213     return new SlowValueList(this, slot);
 214 }
 215
 216 TermList *
 217 Database::Internal::open_spelling_termlist(const string &) const
 218 {
 219     // Only implemented for some database backends - others will just not
 220     // suggest spelling corrections (or not contribute to them in a multiple
 221     // database situation).
 222     return NULL;
 223 }
 224
 225 TermList *
 226 Database::Internal::open_spelling_wordlist() const
 227 {
 228     // Only implemented for some database backends - others will just not
 229     // suggest spelling corrections (or not contribute to them in a multiple
 230     // database situation).
 231     return NULL;
 232 }
 233
 234 Xapian::doccount
 235 Database::Internal::get_spelling_frequency(const string &) const
 236 {
 237     // Only implemented for some database backends - others will just not
 238     // suggest spelling corrections (or not contribute to them in a multiple
 239     // database situation).
 240     return 0;
 241 }
 242
 243 void
 244 Database::Internal::add_spelling(const string &, Xapian::termcount) const
 245 {
 246     throw Xapian::UnimplementedError("This backend doesn't implement spelling correction");
 247 }
 248
 249 void
 250 Database::Internal::remove_spelling(const string &, Xapian::termcount) const
 251 {
 252     throw Xapian::UnimplementedError("This backend doesn't implement spelling correction");
 253 }
 254
 255 TermList *
 256 Database::Internal::open_synonym_termlist(const string &) const
 257 {
 258     // Only implemented for some database backends - others will just not
 259     // expand synonyms (or not contribute to them in a multiple database
 260     // situation).
 261     return NULL;
 262 }
 263
 264 TermList *
 265 Database::Internal::open_synonym_keylist(const string &) const
 266 {
 267     // Only implemented for some database backends - others will just not
 268     // expand synonyms (or not contribute to them in a multiple database
 269     // situation).
 270     return NULL;
 271 }
 272
 273 void
 274 Database::Internal::add_synonym(const string &, const string &) const
 275 {
 276     throw Xapian::UnimplementedError("This backend doesn't implement synonyms");
 277 }
 278
 279 void
 280 Database::Internal::remove_synonym(const string &, const string &) const
 281 {
 282     throw Xapian::UnimplementedError("This backend doesn't implement synonyms");
 283 }
 284
 285 void
 286 Database::Internal::clear_synonyms(const string &) const
 287 {
 288     throw Xapian::UnimplementedError("This backend doesn't implement synonyms");
 289 }
 290
 291 string
 292 Database::Internal::get_metadata(const string &) const
 293 {
 294     return string();
 295 }
 296
 297 TermList *
 298 Database::Internal::open_metadata_keylist(const string &) const
 299 {
 300     // Only implemented for some database backends - others will simply report
 301     // there being no metadata keys.
 302     return NULL;
 303 }
 304
 305 void
 306 Database::Internal::set_metadata(const string &, const string &)
 307 {
 308     throw Xapian::UnimplementedError("This backend doesn't implement metadata");
 309 }
 310
 311 bool
 312 Database::Internal::reopen()
 313 {
 314     // Database backends which don't support simultaneous update and reading
 315     // probably don't need to do anything here.  And since we didn't do
 316     // anything we should return false to indicate that nothing has changed.
 317     return false;
 318 }
 319
 320 void
 321 Database::Internal::request_document(Xapian::docid /*did*/) const
 322 {
 323 }
 324
 325 Xapian::Document::Internal *
 326 Database::Internal::collect_document(Xapian::docid did) const
 327 {
 328     // Open the document lazily - collect document is only called by
 329     // Enquire::Internal::read_doc() for a given MSetItem, so we know that the
 330     // document already exists.
 331     return open_document(did, true);
 332 }
 333
 334 void
 335 Database::Internal::write_changesets_to_fd(int, const string &, bool, ReplicationInfo *)
 336 {
 337     throw Xapian::UnimplementedError("This backend doesn't provide changesets");
 338 }
 339
 340 string
 341 Database::Internal::get_revision_info() const
 342 {
 343     throw Xapian::UnimplementedError("This backend doesn't provide access to revision information");
 344 }
 345
 346 string
 347 Database::Internal::get_uuid() const
 348 {
 349     return string();
 350 }
 351
 352 void
 353 Database::Internal::invalidate_doc_object(Xapian::Document::Internal *) const
 354 {
 355     // Do nothing, by default.
 356 }
 357
 358 void
 359 Database::Internal::get_used_docid_range(Xapian::docid &,
 360                                          Xapian::docid &) const
 361 {
 362     throw Xapian::UnimplementedError("This backend doesn't implement get_used_docid_range()");
 363 }
 364
 365 bool
 366 Database::Internal::locked() const
 367 {
 368     return false;
 369 }
 370
 371 }