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#!/usr/bin/env python
# Copyright 2007 Google Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.

"""Full text indexing and search, implemented in pure python.

Defines a SearchableModel subclass of db.Model that supports full text
indexing and search, based on the datastore's existing indexes.

Don't expect too much. First, there's no ranking, which is a killer drawback.
There's also no exact phrase match, substring match, boolean operators,
stemming, or other common full text search features. Finally, support for stop
words (common words that are not indexed) is currently limited to English.

To be indexed, entities must be created and saved as SearchableModel
instances, e.g.:

  class Article(search.SearchableModel):
    text = db.TextProperty()

  article = Article(text=...)

To search the full text index, use the SearchableModel.all() method to get an
instance of SearchableModel.Query, which subclasses db.Query. Use its search()
method to provide a search query, in addition to any other filters or sort
orders, e.g.:

  query = article.all().search('a search query').filter(...).order(...)
  for result in query:

The full text index is stored in a property named __searchable_text_index.

Specifying multiple indexes and properties to index

By default, one index is created with all string properties. You can define
multiple indexes and specify which properties should be indexed for each by
overriding SearchableProperties() method of model.SearchableModel, for example:

  class Article(search.SearchableModel):
    def SearchableProperties(cls):
      return [['book', 'author'], ['book']]

In this example, two indexes will be maintained - one that includes 'book' and
'author' properties, and another one for 'book' property only. They will be
stored in properties named __searchable_text_index_book_author and
__searchable_text_index_book respectively. Note that the index that includes
all properties will not be created unless added explicitly like this:

  def SearchableProperties(cls):
    return [['book', 'author'], ['book'], search.ALL_PROPERTIES]

The default return value of SearchableProperties() is [search.ALL_PROPERTIES]
(one index, all properties).

To search using a custom-defined index, pass its definition
in 'properties' parameter of 'search':

  Article.all().search('Lem', properties=['book', 'author'])

Note that the order of properties in the list matters.

Adding indexes to  index.yaml

In general, if you just want to provide full text search, you *don't* need to
add any extra indexes to your index.yaml. However, if you want to use search()
in a query *in addition to* an ancestor, filter, or sort order, you'll need to
create an index in index.yaml with the __searchable_text_index property. For

  - kind: Article
    - name: __searchable_text_index
    - name: date
      direction: desc

Similarly, if you created a custom index (see above), use the name of the
property it's stored in, e.g. __searchable_text_index_book_author.

Note that using SearchableModel will noticeable increase the latency of save()
operations, since it writes an index row for each indexable word. This also
means that the latency of save() will increase roughly with the size of the
properties in a given entity. Caveat hacker!

import re
import string
import sys

from google.appengine.api import datastore
from google.appengine.api import datastore_errors
from google.appengine.api import datastore_types
from google.appengine.ext import db
from google.appengine.datastore import datastore_query


[docs]class SearchableEntity(datastore.Entity): """A subclass of datastore.Entity that supports full text indexing. Automatically indexes all string and Text properties, using the datastore's built-in per-property indices. To search, use the SearchableQuery class and its Search() method. """ _FULL_TEXT_INDEX_PROPERTY = '__searchable_text_index' _FULL_TEXT_MIN_LENGTH = 3 _FULL_TEXT_STOP_WORDS = frozenset([ 'a', 'about', 'according', 'accordingly', 'affected', 'affecting', 'after', 'again', 'against', 'all', 'almost', 'already', 'also', 'although', 'always', 'am', 'among', 'an', 'and', 'any', 'anyone', 'apparently', 'are', 'arise', 'as', 'aside', 'at', 'away', 'be', 'became', 'because', 'become', 'becomes', 'been', 'before', 'being', 'between', 'both', 'briefly', 'but', 'by', 'came', 'can', 'cannot', 'certain', 'certainly', 'could', 'did', 'do', 'does', 'done', 'during', 'each', 'either', 'else', 'etc', 'ever', 'every', 'following', 'for', 'found', 'from', 'further', 'gave', 'gets', 'give', 'given', 'giving', 'gone', 'got', 'had', 'hardly', 'has', 'have', 'having', 'here', 'how', 'however', 'i', 'if', 'in', 'into', 'is', 'it', 'itself', 'just', 'keep', 'kept', 'knowledge', 'largely', 'like', 'made', 'mainly', 'make', 'many', 'might', 'more', 'most', 'mostly', 'much', 'must', 'nearly', 'necessarily', 'neither', 'next', 'no', 'none', 'nor', 'normally', 'not', 'noted', 'now', 'obtain', 'obtained', 'of', 'often', 'on', 'only', 'or', 'other', 'our', 'out', 'owing', 'particularly', 'past', 'perhaps', 'please', 'poorly', 'possible', 'possibly', 'potentially', 'predominantly', 'present', 'previously', 'primarily', 'probably', 'prompt', 'promptly', 'put', 'quickly', 'quite', 'rather', 'readily', 'really', 'recently', 'regarding', 'regardless', 'relatively', 'respectively', 'resulted', 'resulting', 'results', 'said', 'same', 'seem', 'seen', 'several', 'shall', 'should', 'show', 'showed', 'shown', 'shows', 'significantly', 'similar', 'similarly', 'since', 'slightly', 'so', 'some', 'sometime', 'somewhat', 'soon', 'specifically', 'state', 'states', 'strongly', 'substantially', 'successfully', 'such', 'sufficiently', 'than', 'that', 'the', 'their', 'theirs', 'them', 'then', 'there', 'therefore', 'these', 'they', 'this', 'those', 'though', 'through', 'throughout', 'to', 'too', 'toward', 'under', 'unless', 'until', 'up', 'upon', 'use', 'used', 'usefully', 'usefulness', 'using', 'usually', 'various', 'very', 'was', 'we', 'were', 'what', 'when', 'where', 'whether', 'which', 'while', 'who', 'whose', 'why', 'widely', 'will', 'with', 'within', 'without', 'would', 'yet', 'you']) _word_delimiter_regex = re.compile('[' + re.escape(string.punctuation) + ']') _searchable_properties = [ALL_PROPERTIES] def __init__(self, kind_or_entity, word_delimiter_regex=None, *args, **kwargs): """Constructor. May be called as a copy constructor. If kind_or_entity is a datastore.Entity, copies it into this Entity. datastore.Get() and Query() returns instances of datastore.Entity, so this is useful for converting them back to SearchableEntity so that they'll be indexed when they're stored back in the datastore. Otherwise, passes through the positional and keyword args to the datastore.Entity constructor. Args: kind_or_entity: string or datastore.Entity word_delimiter_regex: a regex matching characters that delimit words """ self._word_delimiter_regex = word_delimiter_regex if isinstance(kind_or_entity, datastore.Entity): self._Entity__key = kind_or_entity._Entity__key self._Entity__unindexed_properties = frozenset(kind_or_entity.unindexed_properties()) if isinstance(kind_or_entity, SearchableEntity): if getattr(kind_or_entity, '_searchable_properties', None) is not None: self._searchable_properties = kind_or_entity._searchable_properties self.update(kind_or_entity) else: super(SearchableEntity, self).__init__(kind_or_entity, *args, **kwargs) def _ToPb(self, *args, **kwargs): """Rebuilds the full text index, then delegates to the superclass. Returns: entity_pb.Entity """ for properties_to_index in self._searchable_properties: index_property_name = SearchableEntity.IndexPropertyName(properties_to_index) if index_property_name in self: del self[index_property_name] if not properties_to_index: properties_to_index = self.keys() index = set() for name in properties_to_index: if not self.has_key(name): continue values = self[name] if not isinstance(values, list): values = [values] if (isinstance(values[0], basestring) and not isinstance(values[0], datastore_types.Blob)): for value in values: index.update(SearchableEntity._FullTextIndex( value, self._word_delimiter_regex)) index_list = list(index) if index_list: self[index_property_name] = index_list return super(SearchableEntity, self)._ToPb(*args, **kwargs) @classmethod def _FullTextIndex(cls, text, word_delimiter_regex=None): """Returns a set of keywords appropriate for full text indexing. See SearchableQuery.Search() for details. Args: text: string Returns: set of strings """ if word_delimiter_regex is None: word_delimiter_regex = cls._word_delimiter_regex if text: datastore_types.ValidateString(text, 'text', max_len=sys.maxint) text = word_delimiter_regex.sub(' ', text) words = text.lower().split() words = set(unicode(w) for w in words) words -= cls._FULL_TEXT_STOP_WORDS for word in list(words): if len(word) < cls._FULL_TEXT_MIN_LENGTH: words.remove(word) else: words = set() return words @classmethod
[docs] def IndexPropertyName(cls, properties): """Given index definition, returns the name of the property to put it in.""" name = SearchableEntity._FULL_TEXT_INDEX_PROPERTY if properties: name += '_' + '_'.join(properties) return name
[docs]class SearchableQuery(datastore.Query): """A subclass of datastore.Query that supports full text search. Only searches over entities that were created and stored using the SearchableEntity or SearchableModel classes. """
[docs] def Search(self, search_query, word_delimiter_regex=None, properties=ALL_PROPERTIES): """Add a search query. This may be combined with filters. Note that keywords in the search query will be silently dropped if they are stop words or too short, ie if they wouldn't be indexed. Args: search_query: string Returns: # this query SearchableQuery """ datastore_types.ValidateString(search_query, 'search query') self._search_query = search_query self._word_delimiter_regex = word_delimiter_regex self._properties = properties return self
[docs] def GetFilterPredicate(self, *args, **kwds): """Adds filters for the search query, then delegates to the superclass. Mimics Query.GetFilterPredicate()'s signature. Raises BadFilterError if a filter on the index property already exists. Returns: datastore_query.FilterPredicate """ properties = getattr(self, "_properties", ALL_PROPERTIES) index_property_name = SearchableEntity.IndexPropertyName(properties) if index_property_name in self: raise datastore_errors.BadFilterError( '%s is a reserved name.' % index_property_name) filter = super(SearchableQuery, self).GetFilterPredicate(*args, **kwds) if hasattr(self, '_search_query'): keywords = SearchableEntity._FullTextIndex( self._search_query, self._word_delimiter_regex) if keywords: search_filter = datastore_query.make_filter( index_property_name, '=', list(keywords)) if filter: filter = datastore_query.CompositeFilter( datastore_query.CompositeFilter.AND, [filter, search_filter]) else: filter = search_filter return filter
[docs]class SearchableMultiQuery(datastore.MultiQuery): """A multiquery that supports Search() by searching subqueries."""
[docs] def Search(self, *args, **kwargs): """Add a search query, by trying to add it to all subqueries. Args: args: Passed to Search on each subquery. kwargs: Passed to Search on each subquery. Returns: self for consistency with SearchableQuery. """ for q in self: q.Search(*args, **kwargs) return self
[docs]class SearchableModel(db.Model): """A subclass of db.Model that supports full text search and indexing. Automatically indexes all string-based properties. To search, use the all() method to get a SearchableModel.Query, then use its search() method. Override SearchableProperties() to define properties to index and/or multiple indexes (see the file's comment). """ @classmethod
[docs] def SearchableProperties(cls): return [ALL_PROPERTIES]
[docs] class Query(db.Query): """A subclass of db.Query that supports full text search.""" _search_query = None _properties = None
[docs] def search(self, search_query, properties=ALL_PROPERTIES): """Adds a full text search to this query. Args: search_query, a string containing the full text search query. Returns: self """ self._search_query = search_query self._properties = properties if self._properties not in getattr(self, '_searchable_properties', [ALL_PROPERTIES]): raise datastore_errors.BadFilterError( '%s does not have a corresponding index. Please add it to' 'the SEARCHABLE_PROPERTIES list' % self._properties) return self
def _get_query(self): """Wraps db.Query._get_query() and injects SearchableQuery.""" query = db.Query._get_query(self, _query_class=SearchableQuery, _multi_query_class=SearchableMultiQuery) if self._search_query: query.Search(self._search_query, properties=self._properties) return query
def _populate_internal_entity(self): """Wraps db.Model._populate_internal_entity() and injects SearchableEntity.""" entity = db.Model._populate_internal_entity(self, _entity_class=SearchableEntity) entity._searchable_properties = self.SearchableProperties() return entity @classmethod
[docs] def from_entity(cls, entity): """Wraps db.Model.from_entity() and injects SearchableEntity.""" if not isinstance(entity, SearchableEntity): entity = SearchableEntity(entity) return super(SearchableModel, cls).from_entity(entity)
[docs] def all(cls): """Returns a SearchableModel.Query for this kind.""" query = SearchableModel.Query(cls) query._searchable_properties = cls.SearchableProperties() return query

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