Exemple #1
0
    def setup(self):
        """
        Defers loading until needed.
        """
        from haystack import connections
        new_index = False

        if self.use_file_storage:
            self.storage = FileStorage(self.path)
        else:
            global LOCALS

            if LOCALS.RAM_STORE is None:
                LOCALS.RAM_STORE = RamStorage()

            self.storage = LOCALS.RAM_STORE

        self.content_field_name, self.schema = self.build_schema(connections[
            self.connection_alias].get_unified_index().all_searchfields())
        self.parser = QueryParser(self.content_field_name, schema=self.schema)

        if new_index is True:
            self.index = self.storage.create_index(self.schema)
        else:
            try:
                self.index = self.storage.open_index(schema=self.schema)
            except index.EmptyIndexError:
                self.index = self.storage.create_index(self.schema)

        self.setup_complete = True
    def setup(self):
        """
        Defers loading until needed.
        """
        from haystack import connections
        new_index = False

        if self.use_file_storage:
            self.storage = FileStorage(self.path)
        else:
            global LOCALS

            if LOCALS.RAM_STORE is None:
                LOCALS.RAM_STORE = RamStorage()

            self.storage = LOCALS.RAM_STORE

        self.content_field_name, self.schema = self.build_schema(connections[self.connection_alias].get_unified_index().all_searchfields())
        self.parser = QueryParser(self.content_field_name, schema=self.schema)

        if new_index is True:
            self.index = self.storage.create_index(self.schema)
        else:
            try:
                self.index = self.storage.open_index(schema=self.schema)
            except index.EmptyIndexError:
                self.index = self.storage.create_index(self.schema)

        self.setup_complete = True
Exemple #3
0
class WhooshSearchBackend(BaseSearchBackend):
    # Word reserved by Whoosh for special use.
    RESERVED_WORDS = (
        'AND',
        'NOT',
        'OR',
        'TO',
    )

    # Characters reserved by Whoosh for special use.
    # The '\\' must come first, so as not to overwrite the other slash replacements.
    RESERVED_CHARACTERS = (
        '\\',
        '+',
        '-',
        '&&',
        '||',
        '!',
        '(',
        ')',
        '{',
        '}',
        '[',
        ']',
        '^',
        '"',
        '~',
        '*',
        '?',
        ':',
        '.',
    )

    def __init__(self, connection_alias, **connection_options):
        super(WhooshSearchBackend, self).__init__(connection_alias,
                                                  **connection_options)
        self.setup_complete = False
        self.use_file_storage = True
        self.post_limit = getattr(connection_options, 'POST_LIMIT',
                                  128 * 1024 * 1024)
        self.path = connection_options.get('PATH')

        if connection_options.get('STORAGE', 'file') != 'file':
            self.use_file_storage = False

        if self.use_file_storage and not self.path:
            raise ImproperlyConfigured(
                "You must specify a 'PATH' in your settings for connection '%s'."
                % connection_alias)

        self.log = logging.getLogger('haystack')

    def setup(self):
        """
        Defers loading until needed.
        """
        from haystack import connections
        new_index = False

        if self.use_file_storage:
            self.storage = FileStorage(self.path)
        else:
            global LOCALS

            if LOCALS.RAM_STORE is None:
                LOCALS.RAM_STORE = RamStorage()

            self.storage = LOCALS.RAM_STORE

        self.content_field_name, self.schema = self.build_schema(connections[
            self.connection_alias].get_unified_index().all_searchfields())
        self.parser = QueryParser(self.content_field_name, schema=self.schema)

        if new_index is True:
            self.index = self.storage.create_index(self.schema)
        else:
            try:
                self.index = self.storage.open_index(schema=self.schema)
            except index.EmptyIndexError:
                self.index = self.storage.create_index(self.schema)

        self.setup_complete = True

    def build_schema(self, fields):
        schema_fields = {
            ID: WHOOSH_ID(stored=True, unique=True),
            DJANGO_CT: WHOOSH_ID(stored=True),
            DJANGO_ID: WHOOSH_ID(stored=True),
        }
        # Grab the number of keys that are hard-coded into Haystack.
        # We'll use this to (possibly) fail slightly more gracefully later.
        initial_key_count = len(schema_fields)
        content_field_name = ''

        for field_name, field_class in fields.items():
            if field_class.is_multivalued:
                if field_class.indexed is False:
                    schema_fields[field_class.index_fieldname] = IDLIST(
                        stored=True, field_boost=field_class.boost)
                else:
                    schema_fields[field_class.index_fieldname] = KEYWORD(
                        stored=True,
                        commas=True,
                        scorable=True,
                        field_boost=field_class.boost)
            elif field_class.field_type in ['date', 'datetime']:
                schema_fields[field_class.index_fieldname] = DATETIME(
                    stored=field_class.stored, sortable=True)
            elif field_class.field_type == 'integer':
                schema_fields[field_class.index_fieldname] = NUMERIC(
                    stored=field_class.stored,
                    numtype=int,
                    field_boost=field_class.boost)
            elif field_class.field_type == 'float':
                schema_fields[field_class.index_fieldname] = NUMERIC(
                    stored=field_class.stored,
                    numtype=float,
                    field_boost=field_class.boost)
            elif field_class.field_type == 'boolean':
                # Field boost isn't supported on BOOLEAN as of 1.8.2.
                schema_fields[field_class.index_fieldname] = BOOLEAN(
                    stored=field_class.stored)
            elif field_class.field_type == 'ngram':
                schema_fields[field_class.index_fieldname] = NGRAM(
                    minsize=3,
                    maxsize=15,
                    stored=field_class.stored,
                    field_boost=field_class.boost)
            elif field_class.field_type == 'edge_ngram':
                schema_fields[field_class.index_fieldname] = NGRAMWORDS(
                    minsize=2,
                    maxsize=15,
                    at='start',
                    stored=field_class.stored,
                    field_boost=field_class.boost)
            else:
                schema_fields[field_class.index_fieldname] = TEXT(
                    stored=True,
                    analyzer=ChineseAnalyzer(),
                    field_boost=field_class.boost,
                    sortable=True)

            if field_class.document is True:
                content_field_name = field_class.index_fieldname
                schema_fields[field_class.index_fieldname].spelling = True

        # Fail more gracefully than relying on the backend to die if no fields
        # are found.
        if len(schema_fields) <= initial_key_count:
            raise SearchBackendError(
                "No fields were found in any search_indexes. Please correct this before attempting to search."
            )

        return (content_field_name, Schema(**schema_fields))

    def update(self, index, iterable, commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        writer = AsyncWriter(self.index)

        for obj in iterable:
            doc = index.full_prepare(obj)

            # Really make sure it's unicode, because Whoosh won't have it any
            # other way.
            for key in doc:
                doc[key] = self._from_python(doc[key])

            # Document boosts aren't supported in Whoosh 2.5.0+.
            if 'boost' in doc:
                del doc['boost']

            try:
                writer.update_document(**doc)
            except Exception as e:
                if not self.silently_fail:
                    raise

                # We'll log the object identifier but won't include the actual object
                # to avoid the possibility of that generating encoding errors while
                # processing the log message:
                self.log.error(u"%s while preparing object for update" %
                               e.__class__.__name__,
                               exc_info=True,
                               extra={
                                   "data": {
                                       "index": index,
                                       "object": get_identifier(obj)
                                   }
                               })

        if len(iterable) > 0:
            # For now, commit no matter what, as we run into locking issues otherwise.
            writer.commit()

    def remove(self, obj_or_string, commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        whoosh_id = get_identifier(obj_or_string)

        try:
            self.index.delete_by_query(q=self.parser.parse(u'%s:"%s"' %
                                                           (ID, whoosh_id)))
        except Exception as e:
            if not self.silently_fail:
                raise

            self.log.error("Failed to remove document '%s' from Whoosh: %s",
                           whoosh_id, e)

    def clear(self, models=[], commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()

        try:
            if not models:
                self.delete_index()
            else:
                models_to_delete = []

                for model in models:
                    models_to_delete.append(u"%s:%s" %
                                            (DJANGO_CT, get_model_ct(model)))

                self.index.delete_by_query(
                    q=self.parser.parse(u" OR ".join(models_to_delete)))
        except Exception as e:
            if not self.silently_fail:
                raise

            self.log.error("Failed to clear documents from Whoosh: %s", e)

    def delete_index(self):
        # Per the Whoosh mailing list, if wiping out everything from the index,
        # it's much more efficient to simply delete the index files.
        if self.use_file_storage:
            self.storage.clean()

        # Recreate everything.
        self.setup()

    def optimize(self):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        self.index.optimize()

    def calculate_page(self, start_offset=0, end_offset=None):
        # Prevent against Whoosh throwing an error. Requires an end_offset
        # greater than 0.
        if not end_offset is None and end_offset <= 0:
            end_offset = 1

        # Determine the page.
        page_num = 0

        if end_offset is None:
            end_offset = 1000000

        if start_offset is None:
            start_offset = 0

        page_length = end_offset - start_offset

        if page_length and page_length > 0:
            page_num = int(start_offset / page_length)

        # Increment because Whoosh uses 1-based page numbers.
        page_num += 1
        return page_num, page_length

    @log_query
    def search(self,
               query_string,
               sort_by=None,
               start_offset=0,
               end_offset=None,
               fields='',
               highlight=False,
               facets=None,
               date_facets=None,
               query_facets=None,
               narrow_queries=None,
               spelling_query=None,
               within=None,
               dwithin=None,
               distance_point=None,
               models=None,
               limit_to_registered_models=None,
               result_class=None,
               **kwargs):
        if not self.setup_complete:
            self.setup()

        # A zero length query should return no results.
        if len(query_string) == 0:
            return {
                'results': [],
                'hits': 0,
            }

        query_string = force_text(query_string)

        # A one-character query (non-wildcard) gets nabbed by a stopwords
        # filter and should yield zero results.
        if len(query_string) <= 1 and query_string != u'*':
            return {
                'results': [],
                'hits': 0,
            }

        reverse = False

        if sort_by is not None:
            # Determine if we need to reverse the results and if Whoosh can
            # handle what it's being asked to sort by. Reversing is an
            # all-or-nothing action, unfortunately.
            sort_by_list = []
            reverse_counter = 0

            for order_by in sort_by:
                if order_by.startswith('-'):
                    reverse_counter += 1

            if reverse_counter and reverse_counter != len(sort_by):
                raise SearchBackendError("Whoosh requires all order_by fields"
                                         " to use the same sort direction")

            for order_by in sort_by:
                if order_by.startswith('-'):
                    sort_by_list.append(order_by[1:])

                    if len(sort_by_list) == 1:
                        reverse = True
                else:
                    sort_by_list.append(order_by)

                    if len(sort_by_list) == 1:
                        reverse = False

            sort_by = sort_by_list[0]

        if facets is not None:
            warnings.warn("Whoosh does not handle faceting.",
                          Warning,
                          stacklevel=2)

        if date_facets is not None:
            warnings.warn("Whoosh does not handle date faceting.",
                          Warning,
                          stacklevel=2)

        if query_facets is not None:
            warnings.warn("Whoosh does not handle query faceting.",
                          Warning,
                          stacklevel=2)

        narrowed_results = None
        self.index = self.index.refresh()

        if limit_to_registered_models is None:
            limit_to_registered_models = getattr(
                settings, 'HAYSTACK_LIMIT_TO_REGISTERED_MODELS', True)

        if models and len(models):
            model_choices = sorted(get_model_ct(model) for model in models)
        elif limit_to_registered_models:
            # Using narrow queries, limit the results to only models handled
            # with the current routers.
            model_choices = self.build_models_list()
        else:
            model_choices = []

        if len(model_choices) > 0:
            if narrow_queries is None:
                narrow_queries = set()

            narrow_queries.add(' OR '.join(
                ['%s:%s' % (DJANGO_CT, rm) for rm in model_choices]))

        narrow_searcher = None

        if narrow_queries is not None:
            # Potentially expensive? I don't see another way to do it in Whoosh...
            narrow_searcher = self.index.searcher()

            for nq in narrow_queries:
                recent_narrowed_results = narrow_searcher.search(
                    self.parser.parse(force_text(nq)), limit=None)

                if len(recent_narrowed_results) <= 0:
                    return {
                        'results': [],
                        'hits': 0,
                    }

                if narrowed_results:
                    narrowed_results.filter(recent_narrowed_results)
                else:
                    narrowed_results = recent_narrowed_results

        self.index = self.index.refresh()

        if self.index.doc_count():
            searcher = self.index.searcher()
            parsed_query = self.parser.parse(query_string)

            # In the event of an invalid/stopworded query, recover gracefully.
            if parsed_query is None:
                return {
                    'results': [],
                    'hits': 0,
                }

            page_num, page_length = self.calculate_page(
                start_offset, end_offset)

            search_kwargs = {
                'pagelen': page_length,
                'sortedby': sort_by,
                'reverse': reverse,
            }

            # Handle the case where the results have been narrowed.
            if narrowed_results is not None:
                search_kwargs['filter'] = narrowed_results

            try:
                raw_page = searcher.search_page(parsed_query, page_num,
                                                **search_kwargs)
            except ValueError:
                if not self.silently_fail:
                    raise

                return {
                    'results': [],
                    'hits': 0,
                    'spelling_suggestion': None,
                }

            # Because as of Whoosh 2.5.1, it will return the wrong page of
            # results if you request something too high. :(
            if raw_page.pagenum < page_num:
                return {
                    'results': [],
                    'hits': 0,
                    'spelling_suggestion': None,
                }

            results = self._process_results(raw_page,
                                            highlight=highlight,
                                            query_string=query_string,
                                            spelling_query=spelling_query,
                                            result_class=result_class)
            searcher.close()

            if hasattr(narrow_searcher, 'close'):
                narrow_searcher.close()

            return results
        else:
            if self.include_spelling:
                if spelling_query:
                    spelling_suggestion = self.create_spelling_suggestion(
                        spelling_query)
                else:
                    spelling_suggestion = self.create_spelling_suggestion(
                        query_string)
            else:
                spelling_suggestion = None

            return {
                'results': [],
                'hits': 0,
                'spelling_suggestion': spelling_suggestion,
            }

    def more_like_this(self,
                       model_instance,
                       additional_query_string=None,
                       start_offset=0,
                       end_offset=None,
                       models=None,
                       limit_to_registered_models=None,
                       result_class=None,
                       **kwargs):
        if not self.setup_complete:
            self.setup()

        # Deferred models will have a different class ("RealClass_Deferred_fieldname")
        # which won't be in our registry:
        model_klass = model_instance._meta.concrete_model

        field_name = self.content_field_name
        narrow_queries = set()
        narrowed_results = None
        self.index = self.index.refresh()

        if limit_to_registered_models is None:
            limit_to_registered_models = getattr(
                settings, 'HAYSTACK_LIMIT_TO_REGISTERED_MODELS', True)

        if models and len(models):
            model_choices = sorted(get_model_ct(model) for model in models)
        elif limit_to_registered_models:
            # Using narrow queries, limit the results to only models handled
            # with the current routers.
            model_choices = self.build_models_list()
        else:
            model_choices = []

        if len(model_choices) > 0:
            if narrow_queries is None:
                narrow_queries = set()

            narrow_queries.add(' OR '.join(
                ['%s:%s' % (DJANGO_CT, rm) for rm in model_choices]))

        if additional_query_string and additional_query_string != '*':
            narrow_queries.add(additional_query_string)

        narrow_searcher = None

        if narrow_queries is not None:
            # Potentially expensive? I don't see another way to do it in Whoosh...
            narrow_searcher = self.index.searcher()

            for nq in narrow_queries:
                recent_narrowed_results = narrow_searcher.search(
                    self.parser.parse(force_text(nq)), limit=None)

                if len(recent_narrowed_results) <= 0:
                    return {
                        'results': [],
                        'hits': 0,
                    }

                if narrowed_results:
                    narrowed_results.filter(recent_narrowed_results)
                else:
                    narrowed_results = recent_narrowed_results

        page_num, page_length = self.calculate_page(start_offset, end_offset)

        self.index = self.index.refresh()
        raw_results = EmptyResults()

        if self.index.doc_count():
            query = "%s:%s" % (ID, get_identifier(model_instance))
            searcher = self.index.searcher()
            parsed_query = self.parser.parse(query)
            results = searcher.search(parsed_query)

            if len(results):
                raw_results = results[0].more_like_this(field_name,
                                                        top=end_offset)

            # Handle the case where the results have been narrowed.
            if narrowed_results is not None and hasattr(raw_results, 'filter'):
                raw_results.filter(narrowed_results)

        try:
            raw_page = ResultsPage(raw_results, page_num, page_length)
        except ValueError:
            if not self.silently_fail:
                raise

            return {
                'results': [],
                'hits': 0,
                'spelling_suggestion': None,
            }

        # Because as of Whoosh 2.5.1, it will return the wrong page of
        # results if you request something too high. :(
        if raw_page.pagenum < page_num:
            return {
                'results': [],
                'hits': 0,
                'spelling_suggestion': None,
            }

        results = self._process_results(raw_page, result_class=result_class)
        searcher.close()

        if hasattr(narrow_searcher, 'close'):
            narrow_searcher.close()

        return results

    def _process_results(self,
                         raw_page,
                         highlight=False,
                         query_string='',
                         spelling_query=None,
                         result_class=None):
        from haystack import connections
        results = []

        # It's important to grab the hits first before slicing. Otherwise, this
        # can cause pagination failures.
        hits = len(raw_page)

        if result_class is None:
            result_class = SearchResult

        facets = {}
        spelling_suggestion = None
        unified_index = connections[self.connection_alias].get_unified_index()
        indexed_models = unified_index.get_indexed_models()

        for doc_offset, raw_result in enumerate(raw_page):
            score = raw_page.score(doc_offset) or 0
            app_label, model_name = raw_result[DJANGO_CT].split('.')
            additional_fields = {}
            model = get_model(app_label, model_name)

            if model and model in indexed_models:
                for key, value in raw_result.items():
                    index = unified_index.get_index(model)
                    string_key = str(key)

                    if string_key in index.fields and hasattr(
                            index.fields[string_key], 'convert'):
                        # Special-cased due to the nature of KEYWORD fields.
                        if index.fields[string_key].is_multivalued:
                            if value is None or len(value) is 0:
                                additional_fields[string_key] = []
                            else:
                                additional_fields[string_key] = value.split(
                                    ',')
                        else:
                            additional_fields[string_key] = index.fields[
                                string_key].convert(value)
                    else:
                        additional_fields[string_key] = self._to_python(value)

                del (additional_fields[DJANGO_CT])
                del (additional_fields[DJANGO_ID])

                if highlight:
                    sa = StemmingAnalyzer()
                    formatter = WhooshHtmlFormatter('em')
                    terms = [token.text for token in sa(query_string)]

                    whoosh_result = whoosh_highlight(
                        additional_fields.get(self.content_field_name), terms,
                        sa, ContextFragmenter(), formatter)
                    additional_fields['highlighted'] = {
                        self.content_field_name: [whoosh_result],
                    }

                result = result_class(app_label, model_name,
                                      raw_result[DJANGO_ID], score,
                                      **additional_fields)
                results.append(result)
            else:
                hits -= 1

        if self.include_spelling:
            if spelling_query:
                spelling_suggestion = self.create_spelling_suggestion(
                    spelling_query)
            else:
                spelling_suggestion = self.create_spelling_suggestion(
                    query_string)

        return {
            'results': results,
            'hits': hits,
            'facets': facets,
            'spelling_suggestion': spelling_suggestion,
        }

    def create_spelling_suggestion(self, query_string):
        spelling_suggestion = None
        reader = self.index.reader()
        corrector = reader.corrector(self.content_field_name)
        cleaned_query = force_text(query_string)

        if not query_string:
            return spelling_suggestion

        # Clean the string.
        for rev_word in self.RESERVED_WORDS:
            cleaned_query = cleaned_query.replace(rev_word, '')

        for rev_char in self.RESERVED_CHARACTERS:
            cleaned_query = cleaned_query.replace(rev_char, '')

        # Break it down.
        query_words = cleaned_query.split()
        suggested_words = []

        for word in query_words:
            suggestions = corrector.suggest(word, limit=1)

            if len(suggestions) > 0:
                suggested_words.append(suggestions[0])

        spelling_suggestion = ' '.join(suggested_words)
        return spelling_suggestion

    def _from_python(self, value):
        """
        Converts Python values to a string for Whoosh.

        Code courtesy of pysolr.
        """
        if hasattr(value, 'strftime'):
            if not hasattr(value, 'hour'):
                value = datetime(value.year, value.month, value.day, 0, 0, 0)
        elif isinstance(value, bool):
            if value:
                value = 'true'
            else:
                value = 'false'
        elif isinstance(value, (list, tuple)):
            value = u','.join([force_text(v) for v in value])
        elif isinstance(value, (six.integer_types, float)):
            # Leave it alone.
            pass
        else:
            value = force_text(value)
        return value

    def _to_python(self, value):
        """
        Converts values from Whoosh to native Python values.

        A port of the same method in pysolr, as they deal with data the same way.
        """
        if value == 'true':
            return True
        elif value == 'false':
            return False

        if value and isinstance(value, six.string_types):
            possible_datetime = DATETIME_REGEX.search(value)

            if possible_datetime:
                date_values = possible_datetime.groupdict()

                for dk, dv in date_values.items():
                    date_values[dk] = int(dv)

                return datetime(date_values['year'], date_values['month'],
                                date_values['day'], date_values['hour'],
                                date_values['minute'], date_values['second'])

        try:
            # Attempt to use json to load the values.
            converted_value = json.loads(value)

            # Try to handle most built-in types.
            if isinstance(
                    converted_value,
                (list, tuple, set, dict, six.integer_types, float, complex)):
                return converted_value
        except:
            # If it fails (SyntaxError or its ilk) or we don't trust it,
            # continue on.
            pass

        return value
class WhooshSearchBackend(BaseSearchBackend):
    # Word reserved by Whoosh for special use.
    RESERVED_WORDS = (
        'AND',
        'NOT',
        'OR',
        'TO',
    )

    # Characters reserved by Whoosh for special use.
    # The '\\' must come first, so as not to overwrite the other slash replacements.
    RESERVED_CHARACTERS = (
        '\\', '+', '-', '&&', '||', '!', '(', ')', '{', '}',
        '[', ']', '^', '"', '~', '*', '?', ':', '.',
    )

    def __init__(self, connection_alias, **connection_options):
        super(WhooshSearchBackend, self).__init__(connection_alias, **connection_options)
        self.setup_complete = False
        self.use_file_storage = True
        self.post_limit = getattr(connection_options, 'POST_LIMIT', 128 * 1024 * 1024)
        self.path = connection_options.get('PATH')

        if connection_options.get('STORAGE', 'file') != 'file':
            self.use_file_storage = False

        if self.use_file_storage and not self.path:
            raise ImproperlyConfigured("You must specify a 'PATH' in your settings for connection '%s'." % connection_alias)

        self.log = logging.getLogger('haystack')

    def setup(self):
        """
        Defers loading until needed.
        """
        from haystack import connections
        new_index = False

        if self.use_file_storage:
            self.storage = FileStorage(self.path)
        else:
            global LOCALS

            if LOCALS.RAM_STORE is None:
                LOCALS.RAM_STORE = RamStorage()

            self.storage = LOCALS.RAM_STORE

        self.content_field_name, self.schema = self.build_schema(connections[self.connection_alias].get_unified_index().all_searchfields())
        self.parser = QueryParser(self.content_field_name, schema=self.schema)

        if new_index is True:
            self.index = self.storage.create_index(self.schema)
        else:
            try:
                self.index = self.storage.open_index(schema=self.schema)
            except index.EmptyIndexError:
                self.index = self.storage.create_index(self.schema)

        self.setup_complete = True

    def build_schema(self, fields):
        schema_fields = {
            ID: WHOOSH_ID(stored=True, unique=True),
            DJANGO_CT: WHOOSH_ID(stored=True),
            DJANGO_ID: WHOOSH_ID(stored=True),
        }
        # Grab the number of keys that are hard-coded into Haystack.
        # We'll use this to (possibly) fail slightly more gracefully later.
        initial_key_count = len(schema_fields)
        content_field_name = ''

        for field_name, field_class in fields.items():
            if field_class.is_multivalued:
                if field_class.indexed is False:
                    schema_fields[field_class.index_fieldname] = IDLIST(stored=True, field_boost=field_class.boost)
                else:
                    schema_fields[field_class.index_fieldname] = KEYWORD(stored=True, commas=True, scorable=True, field_boost=field_class.boost)
            elif field_class.field_type in ['date', 'datetime']:
                schema_fields[field_class.index_fieldname] = DATETIME(stored=field_class.stored, sortable=True)
            elif field_class.field_type == 'integer':
                schema_fields[field_class.index_fieldname] = NUMERIC(stored=field_class.stored, numtype=int, field_boost=field_class.boost)
            elif field_class.field_type == 'float':
                schema_fields[field_class.index_fieldname] = NUMERIC(stored=field_class.stored, numtype=float, field_boost=field_class.boost)
            elif field_class.field_type == 'boolean':
                # Field boost isn't supported on BOOLEAN as of 1.8.2.
                schema_fields[field_class.index_fieldname] = BOOLEAN(stored=field_class.stored)
            elif field_class.field_type == 'ngram':
                schema_fields[field_class.index_fieldname] = NGRAM(minsize=3, maxsize=15, stored=field_class.stored, field_boost=field_class.boost)
            elif field_class.field_type == 'edge_ngram':
                schema_fields[field_class.index_fieldname] = NGRAMWORDS(minsize=2, maxsize=15, at='start', stored=field_class.stored, field_boost=field_class.boost)
            else:
                schema_fields[field_class.index_fieldname] = TEXT(stored=True, analyzer=ChineseAnalyzer(), field_boost=field_class.boost, sortable=True)

            if field_class.document is True:
                content_field_name = field_class.index_fieldname
                schema_fields[field_class.index_fieldname].spelling = True

        # Fail more gracefully than relying on the backend to die if no fields
        # are found.
        if len(schema_fields) <= initial_key_count:
            raise SearchBackendError("No fields were found in any search_indexes. Please correct this before attempting to search.")

        return (content_field_name, Schema(**schema_fields))

    def update(self, index, iterable, commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        writer = AsyncWriter(self.index)

        for obj in iterable:
            doc = index.full_prepare(obj)

            # Really make sure it's unicode, because Whoosh won't have it any
            # other way.
            for key in doc:
                doc[key] = self._from_python(doc[key])

            # Document boosts aren't supported in Whoosh 2.5.0+.
            if 'boost' in doc:
                del doc['boost']

            try:
                writer.update_document(**doc)
            except Exception as e:
                if not self.silently_fail:
                    raise

                # We'll log the object identifier but won't include the actual object
                # to avoid the possibility of that generating encoding errors while
                # processing the log message:
                self.log.error(u"%s while preparing object for update" % e.__class__.__name__, exc_info=True, extra={
                    "data": {
                        "index": index,
                        "object": get_identifier(obj)
                    }
                })

        if len(iterable) > 0:
            # For now, commit no matter what, as we run into locking issues otherwise.
            writer.commit()

    def remove(self, obj_or_string, commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        whoosh_id = get_identifier(obj_or_string)

        try:
            self.index.delete_by_query(q=self.parser.parse(u'%s:"%s"' % (ID, whoosh_id)))
        except Exception as e:
            if not self.silently_fail:
                raise

            self.log.error("Failed to remove document '%s' from Whoosh: %s", whoosh_id, e)

    def clear(self, models=[], commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()

        try:
            if not models:
                self.delete_index()
            else:
                models_to_delete = []

                for model in models:
                    models_to_delete.append(u"%s:%s" % (DJANGO_CT, get_model_ct(model)))

                self.index.delete_by_query(q=self.parser.parse(u" OR ".join(models_to_delete)))
        except Exception as e:
            if not self.silently_fail:
                raise

            self.log.error("Failed to clear documents from Whoosh: %s", e)

    def delete_index(self):
        # Per the Whoosh mailing list, if wiping out everything from the index,
        # it's much more efficient to simply delete the index files.
        if self.use_file_storage:
            self.storage.clean()

        # Recreate everything.
        self.setup()

    def optimize(self):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        self.index.optimize()

    def calculate_page(self, start_offset=0, end_offset=None):
        # Prevent against Whoosh throwing an error. Requires an end_offset
        # greater than 0.
        if not end_offset is None and end_offset <= 0:
            end_offset = 1

        # Determine the page.
        page_num = 0

        if end_offset is None:
            end_offset = 1000000

        if start_offset is None:
            start_offset = 0

        page_length = end_offset - start_offset

        if page_length and page_length > 0:
            page_num = int(start_offset / page_length)

        # Increment because Whoosh uses 1-based page numbers.
        page_num += 1
        return page_num, page_length

    @log_query
    def search(self, query_string, sort_by=None, start_offset=0, end_offset=None,
               fields='', highlight=False, facets=None, date_facets=None, query_facets=None,
               narrow_queries=None, spelling_query=None, within=None,
               dwithin=None, distance_point=None, models=None,
               limit_to_registered_models=None, result_class=None, **kwargs):
        if not self.setup_complete:
            self.setup()

        # A zero length query should return no results.
        if len(query_string) == 0:
            return {
                'results': [],
                'hits': 0,
            }

        query_string = force_text(query_string)

        # A one-character query (non-wildcard) gets nabbed by a stopwords
        # filter and should yield zero results.
        if len(query_string) <= 1 and query_string != u'*':
            return {
                'results': [],
                'hits': 0,
            }

        reverse = False

        if sort_by is not None:
            # Determine if we need to reverse the results and if Whoosh can
            # handle what it's being asked to sort by. Reversing is an
            # all-or-nothing action, unfortunately.
            sort_by_list = []
            reverse_counter = 0

            for order_by in sort_by:
                if order_by.startswith('-'):
                    reverse_counter += 1

            if reverse_counter and reverse_counter != len(sort_by):
                raise SearchBackendError("Whoosh requires all order_by fields"
                                         " to use the same sort direction")

            for order_by in sort_by:
                if order_by.startswith('-'):
                    sort_by_list.append(order_by[1:])

                    if len(sort_by_list) == 1:
                        reverse = True
                else:
                    sort_by_list.append(order_by)

                    if len(sort_by_list) == 1:
                        reverse = False

            sort_by = sort_by_list[0]

        if facets is not None:
            warnings.warn("Whoosh does not handle faceting.", Warning, stacklevel=2)

        if date_facets is not None:
            warnings.warn("Whoosh does not handle date faceting.", Warning, stacklevel=2)

        if query_facets is not None:
            warnings.warn("Whoosh does not handle query faceting.", Warning, stacklevel=2)

        narrowed_results = None
        self.index = self.index.refresh()

        if limit_to_registered_models is None:
            limit_to_registered_models = getattr(settings, 'HAYSTACK_LIMIT_TO_REGISTERED_MODELS', True)

        if models and len(models):
            model_choices = sorted(get_model_ct(model) for model in models)
        elif limit_to_registered_models:
            # Using narrow queries, limit the results to only models handled
            # with the current routers.
            model_choices = self.build_models_list()
        else:
            model_choices = []

        if len(model_choices) > 0:
            if narrow_queries is None:
                narrow_queries = set()

            narrow_queries.add(' OR '.join(['%s:%s' % (DJANGO_CT, rm) for rm in model_choices]))

        narrow_searcher = None

        if narrow_queries is not None:
            # Potentially expensive? I don't see another way to do it in Whoosh...
            narrow_searcher = self.index.searcher()

            for nq in narrow_queries:
                recent_narrowed_results = narrow_searcher.search(self.parser.parse(force_text(nq)),
                                                                 limit=None)

                if len(recent_narrowed_results) <= 0:
                    return {
                        'results': [],
                        'hits': 0,
                    }

                if narrowed_results:
                    narrowed_results.filter(recent_narrowed_results)
                else:
                   narrowed_results = recent_narrowed_results

        self.index = self.index.refresh()

        if self.index.doc_count():
            searcher = self.index.searcher()
            parsed_query = self.parser.parse(query_string)

            # In the event of an invalid/stopworded query, recover gracefully.
            if parsed_query is None:
                return {
                    'results': [],
                    'hits': 0,
                }

            page_num, page_length = self.calculate_page(start_offset, end_offset)

            search_kwargs = {
                'pagelen': page_length,
                'sortedby': sort_by,
                'reverse': reverse,
            }

            # Handle the case where the results have been narrowed.
            if narrowed_results is not None:
                search_kwargs['filter'] = narrowed_results

            try:
                raw_page = searcher.search_page(
                    parsed_query,
                    page_num,
                    **search_kwargs
                )
            except ValueError:
                if not self.silently_fail:
                    raise

                return {
                    'results': [],
                    'hits': 0,
                    'spelling_suggestion': None,
                }

            # Because as of Whoosh 2.5.1, it will return the wrong page of
            # results if you request something too high. :(
            if raw_page.pagenum < page_num:
                return {
                    'results': [],
                    'hits': 0,
                    'spelling_suggestion': None,
                }

            results = self._process_results(raw_page, highlight=highlight, query_string=query_string, spelling_query=spelling_query, result_class=result_class)
            searcher.close()

            if hasattr(narrow_searcher, 'close'):
                narrow_searcher.close()

            return results
        else:
            if self.include_spelling:
                if spelling_query:
                    spelling_suggestion = self.create_spelling_suggestion(spelling_query)
                else:
                    spelling_suggestion = self.create_spelling_suggestion(query_string)
            else:
                spelling_suggestion = None

            return {
                'results': [],
                'hits': 0,
                'spelling_suggestion': spelling_suggestion,
            }

    def more_like_this(self, model_instance, additional_query_string=None,
                       start_offset=0, end_offset=None, models=None,
                       limit_to_registered_models=None, result_class=None, **kwargs):
        if not self.setup_complete:
            self.setup()

        # Deferred models will have a different class ("RealClass_Deferred_fieldname")
        # which won't be in our registry:
        model_klass = model_instance._meta.concrete_model

        field_name = self.content_field_name
        narrow_queries = set()
        narrowed_results = None
        self.index = self.index.refresh()

        if limit_to_registered_models is None:
            limit_to_registered_models = getattr(settings, 'HAYSTACK_LIMIT_TO_REGISTERED_MODELS', True)

        if models and len(models):
            model_choices = sorted(get_model_ct(model) for model in models)
        elif limit_to_registered_models:
            # Using narrow queries, limit the results to only models handled
            # with the current routers.
            model_choices = self.build_models_list()
        else:
            model_choices = []

        if len(model_choices) > 0:
            if narrow_queries is None:
                narrow_queries = set()

            narrow_queries.add(' OR '.join(['%s:%s' % (DJANGO_CT, rm) for rm in model_choices]))

        if additional_query_string and additional_query_string != '*':
            narrow_queries.add(additional_query_string)

        narrow_searcher = None

        if narrow_queries is not None:
            # Potentially expensive? I don't see another way to do it in Whoosh...
            narrow_searcher = self.index.searcher()

            for nq in narrow_queries:
                recent_narrowed_results = narrow_searcher.search(self.parser.parse(force_text(nq)),
                                                                 limit=None)

                if len(recent_narrowed_results) <= 0:
                    return {
                        'results': [],
                        'hits': 0,
                    }

                if narrowed_results:
                    narrowed_results.filter(recent_narrowed_results)
                else:
                   narrowed_results = recent_narrowed_results

        page_num, page_length = self.calculate_page(start_offset, end_offset)

        self.index = self.index.refresh()
        raw_results = EmptyResults()

        if self.index.doc_count():
            query = "%s:%s" % (ID, get_identifier(model_instance))
            searcher = self.index.searcher()
            parsed_query = self.parser.parse(query)
            results = searcher.search(parsed_query)

            if len(results):
                raw_results = results[0].more_like_this(field_name, top=end_offset)

            # Handle the case where the results have been narrowed.
            if narrowed_results is not None and hasattr(raw_results, 'filter'):
                raw_results.filter(narrowed_results)

        try:
            raw_page = ResultsPage(raw_results, page_num, page_length)
        except ValueError:
            if not self.silently_fail:
                raise

            return {
                'results': [],
                'hits': 0,
                'spelling_suggestion': None,
            }

        # Because as of Whoosh 2.5.1, it will return the wrong page of
        # results if you request something too high. :(
        if raw_page.pagenum < page_num:
            return {
                'results': [],
                'hits': 0,
                'spelling_suggestion': None,
            }

        results = self._process_results(raw_page, result_class=result_class)
        searcher.close()

        if hasattr(narrow_searcher, 'close'):
            narrow_searcher.close()

        return results

    def _process_results(self, raw_page, highlight=False, query_string='', spelling_query=None, result_class=None):
        from haystack import connections
        results = []

        # It's important to grab the hits first before slicing. Otherwise, this
        # can cause pagination failures.
        hits = len(raw_page)

        if result_class is None:
            result_class = SearchResult

        facets = {}
        spelling_suggestion = None
        unified_index = connections[self.connection_alias].get_unified_index()
        indexed_models = unified_index.get_indexed_models()

        for doc_offset, raw_result in enumerate(raw_page):
            score = raw_page.score(doc_offset) or 0
            app_label, model_name = raw_result[DJANGO_CT].split('.')
            additional_fields = {}
            model = get_model(app_label, model_name)

            if model and model in indexed_models:
                for key, value in raw_result.items():
                    index = unified_index.get_index(model)
                    string_key = str(key)

                    if string_key in index.fields and hasattr(index.fields[string_key], 'convert'):
                        # Special-cased due to the nature of KEYWORD fields.
                        if index.fields[string_key].is_multivalued:
                            if value is None or len(value) is 0:
                                additional_fields[string_key] = []
                            else:
                                additional_fields[string_key] = value.split(',')
                        else:
                            additional_fields[string_key] = index.fields[string_key].convert(value)
                    else:
                        additional_fields[string_key] = self._to_python(value)

                del(additional_fields[DJANGO_CT])
                del(additional_fields[DJANGO_ID])

                if highlight:
                    sa = StemmingAnalyzer()
                    formatter = WhooshHtmlFormatter('em')
                    terms = [token.text for token in sa(query_string)]

                    whoosh_result = whoosh_highlight(
                        additional_fields.get(self.content_field_name),
                        terms,
                        sa,
                        ContextFragmenter(),
                        formatter
                    )
                    additional_fields['highlighted'] = {
                        self.content_field_name: [whoosh_result],
                    }

                result = result_class(app_label, model_name, raw_result[DJANGO_ID], score, **additional_fields)
                results.append(result)
            else:
                hits -= 1

        if self.include_spelling:
            if spelling_query:
                spelling_suggestion = self.create_spelling_suggestion(spelling_query)
            else:
                spelling_suggestion = self.create_spelling_suggestion(query_string)

        return {
            'results': results,
            'hits': hits,
            'facets': facets,
            'spelling_suggestion': spelling_suggestion,
        }

    def create_spelling_suggestion(self, query_string):
        spelling_suggestion = None
        reader = self.index.reader()
        corrector = reader.corrector(self.content_field_name)
        cleaned_query = force_text(query_string)

        if not query_string:
            return spelling_suggestion

        # Clean the string.
        for rev_word in self.RESERVED_WORDS:
            cleaned_query = cleaned_query.replace(rev_word, '')

        for rev_char in self.RESERVED_CHARACTERS:
            cleaned_query = cleaned_query.replace(rev_char, '')

        # Break it down.
        query_words = cleaned_query.split()
        suggested_words = []

        for word in query_words:
            suggestions = corrector.suggest(word, limit=1)

            if len(suggestions) > 0:
                suggested_words.append(suggestions[0])

        spelling_suggestion = ' '.join(suggested_words)
        return spelling_suggestion

    def _from_python(self, value):
        """
        Converts Python values to a string for Whoosh.

        Code courtesy of pysolr.
        """
        if hasattr(value, 'strftime'):
            if not hasattr(value, 'hour'):
                value = datetime(value.year, value.month, value.day, 0, 0, 0)
        elif isinstance(value, bool):
            if value:
                value = 'true'
            else:
                value = 'false'
        elif isinstance(value, (list, tuple)):
            value = u','.join([force_text(v) for v in value])
        elif isinstance(value, (six.integer_types, float)):
            # Leave it alone.
            pass
        else:
            value = force_text(value)
        return value

    def _to_python(self, value):
        """
        Converts values from Whoosh to native Python values.

        A port of the same method in pysolr, as they deal with data the same way.
        """
        if value == 'true':
            return True
        elif value == 'false':
            return False

        if value and isinstance(value, six.string_types):
            possible_datetime = DATETIME_REGEX.search(value)

            if possible_datetime:
                date_values = possible_datetime.groupdict()

                for dk, dv in date_values.items():
                    date_values[dk] = int(dv)

                return datetime(date_values['year'], date_values['month'], date_values['day'], date_values['hour'], date_values['minute'], date_values['second'])

        try:
            # Attempt to use json to load the values.
            converted_value = json.loads(value)

            # Try to handle most built-in types.
            if isinstance(converted_value, (list, tuple, set, dict, six.integer_types, float, complex)):
                return converted_value
        except:
            # If it fails (SyntaxError or its ilk) or we don't trust it,
            # continue on.
            pass

        return value