-"""
-Models and managers for generic tagging.
-"""
-# Python 2.3 compatibility
-if not hasattr(__builtins__, 'set'):
- from sets import Set as set
-
-from django.contrib.contenttypes import generic
-from django.contrib.contenttypes.models import ContentType
-from django.db import connection, models
-from django.utils.translation import ugettext_lazy as _
-from django.db.models.base import ModelBase
-
-qn = connection.ops.quote_name
-
-try:
- from django.db.models.query import parse_lookup
-except ImportError:
- parse_lookup = None
-
-
-def get_queryset_and_model(queryset_or_model):
- """
- Given a ``QuerySet`` or a ``Model``, returns a two-tuple of
- (queryset, model).
-
- If a ``Model`` is given, the ``QuerySet`` returned will be created
- using its default manager.
- """
- try:
- return queryset_or_model, queryset_or_model.model
- except AttributeError:
- return queryset_or_model._default_manager.all(), queryset_or_model
-
-
-############
-# Managers #
-############
-class TagManager(models.Manager):
- def __init__(self, intermediary_table_model):
- super(TagManager, self).__init__()
- self.intermediary_table_model = intermediary_table_model
-
- def update_tags(self, obj, tags):
- """
- Update tags associated with an object.
- """
- content_type = ContentType.objects.get_for_model(obj)
- current_tags = list(self.filter(items__content_type__pk=content_type.pk,
- items__object_id=obj.pk))
- updated_tags = self.model.get_tag_list(tags)
-
- # Remove tags which no longer apply
- tags_for_removal = [tag for tag in current_tags \
- if tag not in updated_tags]
- if len(tags_for_removal):
- self.intermediary_table_model._default_manager.filter(content_type__pk=content_type.pk,
- object_id=obj.pk,
- tag__in=tags_for_removal).delete()
- # Add new tags
- for tag in updated_tags:
- if tag not in current_tags:
- self.intermediary_table_model._default_manager.create(tag=tag, content_object=obj)
-
- def get_for_object(self, obj):
- """
- Create a queryset matching all tags associated with the given
- object.
- """
- ctype = ContentType.objects.get_for_model(obj)
- return self.filter(items__content_type__pk=ctype.pk,
- items__object_id=obj.pk)
-
- def _get_usage(self, model, counts=False, min_count=None, extra_joins=None, extra_criteria=None, params=None, extra=None):
- """
- Perform the custom SQL query for ``usage_for_model`` and
- ``usage_for_queryset``.
- """
- if min_count is not None: counts = True
-
- model_table = qn(model._meta.db_table)
- model_pk = '%s.%s' % (model_table, qn(model._meta.pk.column))
- tag_columns = self._get_tag_columns()
-
- if extra is None: extra = {}
- extra_where = ''
- if 'where' in extra:
- extra_where = 'AND ' + ' AND '.join(extra['where'])
-
- query = """
- SELECT DISTINCT %(tag_columns)s%(count_sql)s
- FROM
- %(tag)s
- INNER JOIN %(tagged_item)s
- ON %(tag)s.id = %(tagged_item)s.tag_id
- INNER JOIN %(model)s
- ON %(tagged_item)s.object_id = %(model_pk)s
- %%s
- WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
- %%s
- %(extra_where)s
- GROUP BY %(tag)s.id, %(tag)s.name
- %%s
- ORDER BY %(tag)s.%(ordering)s ASC""" % {
- 'tag': qn(self.model._meta.db_table),
- 'ordering': ', '.join(qn(field) for field in self.model._meta.ordering),
- 'tag_columns': tag_columns,
- 'count_sql': counts and (', COUNT(%s)' % model_pk) or '',
- 'tagged_item': qn(self.intermediary_table_model._meta.db_table),
- 'model': model_table,
- 'model_pk': model_pk,
- 'extra_where': extra_where,
- 'content_type_id': ContentType.objects.get_for_model(model).pk,
- }
-
- min_count_sql = ''
- if min_count is not None:
- min_count_sql = 'HAVING COUNT(%s) >= %%s' % model_pk
- params.append(min_count)
-
- cursor = connection.cursor()
- cursor.execute(query % (extra_joins, extra_criteria, min_count_sql), params)
- tags = []
- for row in cursor.fetchall():
- t = self.model(*row[:len(self.model._meta.fields)])
- if counts:
- t.count = row[len(self.model._meta.fields)]
- tags.append(t)
- return tags
-
- def usage_for_model(self, model, counts=False, min_count=None, filters=None, extra=None):
- """
- Obtain a list of tags associated with instances of the given
- Model class.
-
- If ``counts`` is True, a ``count`` attribute will be added to
- each tag, indicating how many times it has been used against
- the Model class in question.
-
- If ``min_count`` is given, only tags which have a ``count``
- greater than or equal to ``min_count`` will be returned.
- Passing a value for ``min_count`` implies ``counts=True``.
-
- To limit the tags (and counts, if specified) returned to those
- used by a subset of the Model's instances, pass a dictionary
- of field lookups to be applied to the given Model as the
- ``filters`` argument.
- """
- if extra is None: extra = {}
- if filters is None: filters = {}
-
- if not parse_lookup:
- # post-queryset-refactor (hand off to usage_for_queryset)
- queryset = model._default_manager.filter()
- for f in filters.items():
- queryset.query.add_filter(f)
- usage = self.usage_for_queryset(queryset, counts, min_count, extra)
- else:
- # pre-queryset-refactor
- extra_joins = ''
- extra_criteria = ''
- params = []
- if len(filters) > 0:
- joins, where, params = parse_lookup(filters.items(), model._meta)
- extra_joins = ' '.join(['%s %s AS %s ON %s' % (join_type, table, alias, condition)
- for (alias, (table, join_type, condition)) in joins.items()])
- extra_criteria = 'AND %s' % (' AND '.join(where))
- usage = self._get_usage(model, counts, min_count, extra_joins, extra_criteria, params, extra)
-
- return usage
-
- def usage_for_queryset(self, queryset, counts=False, min_count=None, extra=None):
- """
- Obtain a list of tags associated with instances of a model
- contained in the given queryset.
-
- If ``counts`` is True, a ``count`` attribute will be added to
- each tag, indicating how many times it has been used against
- the Model class in question.
-
- If ``min_count`` is given, only tags which have a ``count``
- greater than or equal to ``min_count`` will be returned.
- Passing a value for ``min_count`` implies ``counts=True``.
- """
- if parse_lookup:
- raise AttributeError("'TagManager.usage_for_queryset' is not compatible with pre-queryset-refactor versions of Django.")
-
- extra_joins = ' '.join(queryset.query.get_from_clause()[0][1:])
- where, params = queryset.query.where.as_sql()
- if where:
- extra_criteria = 'AND %s' % where
- else:
- extra_criteria = ''
- return self._get_usage(queryset.model, counts, min_count, extra_joins, extra_criteria, params, extra)
-
- def related_for_model(self, tags, model, counts=False, min_count=None, extra=None):
- """
- Obtain a list of tags related to a given list of tags - that
- is, other tags used by items which have all the given tags.
-
- If ``counts`` is True, a ``count`` attribute will be added to
- each tag, indicating the number of items which have it in
- addition to the given list of tags.
-
- If ``min_count`` is given, only tags which have a ``count``
- greater than or equal to ``min_count`` will be returned.
- Passing a value for ``min_count`` implies ``counts=True``.
- """
- if min_count is not None: counts = True
- tags = self.model.get_tag_list(tags)
- tag_count = len(tags)
- tagged_item_table = qn(self.intermediary_table_model._meta.db_table)
- tag_columns = self._get_tag_columns()
-
- if extra is None: extra = {}
- extra_where = ''
- if 'where' in extra:
- extra_where = 'AND ' + ' AND '.join(extra['where'])
-
- query = """
- SELECT %(tag_columns)s%(count_sql)s
- FROM %(tagged_item)s INNER JOIN %(tag)s ON %(tagged_item)s.tag_id = %(tag)s.id
- WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
- AND %(tagged_item)s.object_id IN
- (
- SELECT %(tagged_item)s.object_id
- FROM %(tagged_item)s, %(tag)s
- WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
- AND %(tag)s.id = %(tagged_item)s.tag_id
- AND %(tag)s.id IN (%(tag_id_placeholders)s)
- GROUP BY %(tagged_item)s.object_id
- HAVING COUNT(%(tagged_item)s.object_id) = %(tag_count)s
- )
- AND %(tag)s.id NOT IN (%(tag_id_placeholders)s)
- %(extra_where)s
- GROUP BY %(tag)s.id, %(tag)s.name
- %(min_count_sql)s
- ORDER BY %(tag)s.%(ordering)s ASC""" % {
- 'tag': qn(self.model._meta.db_table),
- 'ordering': ', '.join(qn(field) for field in self.model._meta.ordering),
- 'tag_columns': tag_columns,
- 'count_sql': counts and ', COUNT(%s.object_id)' % tagged_item_table or '',
- 'tagged_item': tagged_item_table,
- 'content_type_id': ContentType.objects.get_for_model(model).pk,
- 'tag_id_placeholders': ','.join(['%s'] * tag_count),
- 'extra_where': extra_where,
- 'tag_count': tag_count,
- 'min_count_sql': min_count is not None and ('HAVING COUNT(%s.object_id) >= %%s' % tagged_item_table) or '',
- }
-
- params = [tag.pk for tag in tags] * 2
- if min_count is not None:
- params.append(min_count)
-
- cursor = connection.cursor()
- cursor.execute(query, params)
- related = []
- for row in cursor.fetchall():
- tag = self.model(*row[:len(self.model._meta.fields)])
- if counts is True:
- tag.count = row[len(self.model._meta.fields)]
- related.append(tag)
- return related
-
- def _get_tag_columns(self):
- tag_table = qn(self.model._meta.db_table)
- return ', '.join('%s.%s' % (tag_table, qn(field.column)) for field in self.model._meta.fields)
-
-
-class TaggedItemManager(models.Manager):
- """
- FIXME There's currently no way to get the ``GROUP BY`` and ``HAVING``
- SQL clauses required by many of this manager's methods into
- Django's ORM.
-
- For now, we manually execute a query to retrieve the PKs of
- objects we're interested in, then use the ORM's ``__in``
- lookup to return a ``QuerySet``.
-
- Once the queryset-refactor branch lands in trunk, this can be
- tidied up significantly.
- """
- def __init__(self, tag_model):
- super(TaggedItemManager, self).__init__()
- self.tag_model = tag_model
-
- def get_by_model(self, queryset_or_model, tags):
- """
- Create a ``QuerySet`` containing instances of the specified
- model associated with a given tag or list of tags.
- """
- tags = self.tag_model.get_tag_list(tags)
- tag_count = len(tags)
- if tag_count == 0:
- # No existing tags were given
- queryset, model = get_queryset_and_model(queryset_or_model)
- return model._default_manager.none()
- elif tag_count == 1:
- # Optimisation for single tag - fall through to the simpler
- # query below.
- tag = tags[0]
- else:
- return self.get_intersection_by_model(queryset_or_model, tags)
-
- queryset, model = get_queryset_and_model(queryset_or_model)
- content_type = ContentType.objects.get_for_model(model)
- opts = self.model._meta
- tagged_item_table = qn(opts.db_table)
- return queryset.extra(
- tables=[opts.db_table],
- where=[
- '%s.content_type_id = %%s' % tagged_item_table,
- '%s.tag_id = %%s' % tagged_item_table,
- '%s.%s = %s.object_id' % (qn(model._meta.db_table),
- qn(model._meta.pk.column),
- tagged_item_table)
- ],
- params=[content_type.pk, tag.pk],
- )
-
- def get_intersection_by_model(self, queryset_or_model, tags):
- """
- Create a ``QuerySet`` containing instances of the specified
- model associated with *all* of the given list of tags.
- """
- tags = self.tag_model.get_tag_list(tags)
- tag_count = len(tags)
- queryset, model = get_queryset_and_model(queryset_or_model)
-
- if not tag_count:
- return model._default_manager.none()
-
- model_table = qn(model._meta.db_table)
- # This query selects the ids of all objects which have all the
- # given tags.
- query = """
- SELECT %(model_pk)s
- FROM %(model)s, %(tagged_item)s
- WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
- AND %(tagged_item)s.tag_id IN (%(tag_id_placeholders)s)
- AND %(model_pk)s = %(tagged_item)s.object_id
- GROUP BY %(model_pk)s
- HAVING COUNT(%(model_pk)s) = %(tag_count)s""" % {
- 'model_pk': '%s.%s' % (model_table, qn(model._meta.pk.column)),
- 'model': model_table,
- 'tagged_item': qn(self.model._meta.db_table),
- 'content_type_id': ContentType.objects.get_for_model(model).pk,
- 'tag_id_placeholders': ','.join(['%s'] * tag_count),
- 'tag_count': tag_count,
- }
-
- cursor = connection.cursor()
- cursor.execute(query, [tag.pk for tag in tags])
- object_ids = [row[0] for row in cursor.fetchall()]
- if len(object_ids) > 0:
- return queryset.filter(pk__in=object_ids)
- else:
- return model._default_manager.none()
-
- def get_union_by_model(self, queryset_or_model, tags):
- """
- Create a ``QuerySet`` containing instances of the specified
- model associated with *any* of the given list of tags.
- """
- tags = self.tag_model.get_tag_list(tags)
- tag_count = len(tags)
- queryset, model = get_queryset_and_model(queryset_or_model)
-
- if not tag_count:
- return model._default_manager.none()
-
- model_table = qn(model._meta.db_table)
- # This query selects the ids of all objects which have any of
- # the given tags.
- query = """
- SELECT %(model_pk)s
- FROM %(model)s, %(tagged_item)s
- WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
- AND %(tagged_item)s.tag_id IN (%(tag_id_placeholders)s)
- AND %(model_pk)s = %(tagged_item)s.object_id
- GROUP BY %(model_pk)s""" % {
- 'model_pk': '%s.%s' % (model_table, qn(model._meta.pk.column)),
- 'model': model_table,
- 'tagged_item': qn(self.model._meta.db_table),
- 'content_type_id': ContentType.objects.get_for_model(model).pk,
- 'tag_id_placeholders': ','.join(['%s'] * tag_count),
- }
-
- cursor = connection.cursor()
- cursor.execute(query, [tag.pk for tag in tags])
- object_ids = [row[0] for row in cursor.fetchall()]
- if len(object_ids) > 0:
- return queryset.filter(pk__in=object_ids)
- else:
- return model._default_manager.none()
-
- def get_related(self, obj, queryset_or_model, num=None):
- """
- Retrieve a list of instances of the specified model which share
- tags with the model instance ``obj``, ordered by the number of
- shared tags in descending order.
-
- If ``num`` is given, a maximum of ``num`` instances will be
- returned.
- """
- queryset, model = get_queryset_and_model(queryset_or_model)
- model_table = qn(model._meta.db_table)
- content_type = ContentType.objects.get_for_model(obj)
- related_content_type = ContentType.objects.get_for_model(model)
- query = """
- SELECT %(model_pk)s, COUNT(related_tagged_item.object_id) AS %(count)s
- FROM %(model)s, %(tagged_item)s, %(tag)s, %(tagged_item)s related_tagged_item
- WHERE %(tagged_item)s.object_id = %%s
- AND %(tagged_item)s.content_type_id = %(content_type_id)s
- AND %(tag)s.id = %(tagged_item)s.tag_id
- AND related_tagged_item.content_type_id = %(related_content_type_id)s
- AND related_tagged_item.tag_id = %(tagged_item)s.tag_id
- AND %(model_pk)s = related_tagged_item.object_id"""
- if content_type.pk == related_content_type.pk:
- # Exclude the given instance itself if determining related
- # instances for the same model.
- query += """
- AND related_tagged_item.object_id != %(tagged_item)s.object_id"""
- query += """
- GROUP BY %(model_pk)s
- ORDER BY %(count)s DESC
- %(limit_offset)s"""
- query = query % {
- 'model_pk': '%s.%s' % (model_table, qn(model._meta.pk.column)),
- 'count': qn('count'),
- 'model': model_table,
- 'tagged_item': qn(self.model._meta.db_table),
- 'tag': qn(self.model._meta.get_field('tag').rel.to._meta.db_table),
- 'content_type_id': content_type.pk,
- 'related_content_type_id': related_content_type.pk,
- 'limit_offset': num is not None and connection.ops.limit_offset_sql(num) or '',
- }
-
- cursor = connection.cursor()
- cursor.execute(query, [obj.pk])
- object_ids = [row[0] for row in cursor.fetchall()]
- if len(object_ids) > 0:
- # Use in_bulk here instead of an id__in lookup, because id__in would
- # clobber the ordering.
- object_dict = queryset.in_bulk(object_ids)
- return [object_dict[object_id] for object_id in object_ids \
- if object_id in object_dict]
- else:
- return []
-
-
-##########
-# Models #
-##########
-def create_intermediary_table_model(model):
- """Create an intermediary table model for the specific tag model"""
- name = model.__name__ + 'Relation'
-
- class Meta:
- db_table = '%s_relation' % model._meta.db_table
- unique_together = (('tag', 'content_type', 'object_id'),)
-
- def obj_unicode(self):
- return u'%s [%s]' % (self.content_type.get_object_for_this_type(pk=self.object_id), self.tag)
-
- # Set up a dictionary to simulate declarations within a class
- attrs = {
- '__module__': model.__module__,
- 'Meta': Meta,
- 'tag': models.ForeignKey(model, verbose_name=_('tag'), related_name='items'),
- 'content_type': models.ForeignKey(ContentType, verbose_name=_('content type')),
- 'object_id': models.PositiveIntegerField(_('object id'), db_index=True),
- 'content_object': generic.GenericForeignKey('content_type', 'object_id'),
- '__unicode__': obj_unicode,
- }
-
- return type(name, (models.Model,), attrs)
-
-
-class TagMeta(ModelBase):
- "Metaclass for tag models (models inheriting from TagBase)."
- def __new__(cls, name, bases, attrs):
- model = super(TagMeta, cls).__new__(cls, name, bases, attrs)
- if not model._meta.abstract:
- # Create an intermediary table and register custom managers for concrete models
- model.intermediary_table_model = create_intermediary_table_model(model)
- TagManager(model.intermediary_table_model).contribute_to_class(model, 'objects')
- TaggedItemManager(model).contribute_to_class(model.intermediary_table_model, 'objects')
- return model
-
-
-class TagBase(models.Model):
- """Abstract class to be inherited by model classes."""
- __metaclass__ = TagMeta
-
- class Meta:
- abstract = True
-
- @staticmethod
- def get_tag_list(tag_list):
- """
- Utility function for accepting tag input in a flexible manner.
-
- You should probably override this method in your subclass.
- """
- if isinstance(tag_list, TagBase):
- return [tag_list]
- else:
- return tag_list
-
fnp / wolnelektury.git / blobdiff