Models and managers for generic tagging.
"""
-# Python 2.3 compatibility
-try:
- set
-except NameError:
- from sets import Set as set
-
-from django.contrib.contenttypes import generic
+from django.contrib.contenttypes.fields import GenericForeignKey
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
from django.core.exceptions import ObjectDoesNotExist
+from django.dispatch import Signal
qn = connection.ops.quote_name
-try:
- from django.db.models.query import parse_lookup
-except ImportError:
- parse_lookup = None
+tags_updated = Signal(providing_args=["affected_tags"])
def get_queryset_and_model(queryset_or_model):
"""
def __init__(self, intermediary_table_model):
super(TagManager, self).__init__()
self.intermediary_table_model = intermediary_table_model
+ models.signals.pre_delete.connect(self.target_deleted)
+
+ def target_deleted(self, instance, **kwargs):
+ """ clear tag relations before deleting an object """
+ try:
+ int(instance.pk)
+ except ValueError:
+ return
+
+ self.update_tags(instance, [])
def update_tags(self, obj, tags):
"""
object_id=obj.pk,
tag__in=tags_for_removal).delete()
# Add new tags
- for tag in updated_tags:
+ tags_to_add = [tag for tag in updated_tags
+ if tag not in current_tags]
+ for tag in tags_to_add:
if tag not in current_tags:
self.intermediary_table_model._default_manager.create(tag=tag, content_object=obj)
+ tags_updated.send(sender=type(obj), instance=obj, affected_tags=tags_to_add + tags_for_removal)
+
def remove_tag(self, obj, tag):
"""
Remove tag from an object.
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_columns)s, %(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):
+ def usage_for_model(self, model, counts=False, filters=None):
"""
Obtain a list of tags associated with instances of the given
Model class.
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 = {}
+ # TODO: Do we really need this filters stuff?
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)
-
+ queryset = model._default_manager.filter()
+ for f in filters.items():
+ queryset.query.add_filter(f)
+ usage = self.usage_for_queryset(queryset, counts)
return usage
- def usage_for_queryset(self, queryset, counts=False, min_count=None, extra=None):
+ def usage_for_queryset(self, queryset, counts=False):
"""
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
+ usage = self.model._default_manager.filter(
+ items__content_type=ContentType.objects.get_for_model(queryset.model),
+ items__object_id__in=queryset
+ )
+ if counts:
+ usage = usage.annotate(count=models.Count('id'))
else:
- extra_criteria = ''
- return self._get_usage(queryset.model, counts, min_count, extra_joins, extra_criteria, params, extra)
+ usage = usage.distinct()
+ return usage
- def related_for_model(self, tags, model, counts=False, min_count=None, extra=None):
+ def related_for_model(self, tags, model, counts=False):
"""
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'])
-
- # Temporary table in this query is a hack to prevent MySQL from executing
- # inner query as dependant query (which could result in severe performance loss)
- 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 *
- FROM (
- 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
- ) AS temporary
- )
- AND %(tag)s.id NOT IN (%(tag_id_placeholders)s)
- %(extra_where)s
- GROUP BY %(tag_columns)s
- %(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)
+ objs = self.model.intermediary_table_model.objects.get_by_model(model, tags)
+ qs = self.usage_for_queryset(objs, counts)
+ qs = qs.exclude(pk__in=[tag.pk for tag in tags])
+ return qs
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
Create a ``QuerySet`` containing instances of the specified
model associated with a given tag or list of tags.
"""
+ queryset, model = get_queryset_and_model(queryset_or_model)
tags = self.tag_model.get_tag_list(tags)
- tag_count = len(tags)
- if tag_count == 0:
+ if not tags:
# 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)
+ return queryset.none()
- 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()
+ # TODO: presumes reverse generic relation
+ # Multiple joins are WAY faster than having-count, at least on Postgres 9.1.
+ for tag in tags:
+ queryset = queryset.filter(tag_relations__tag=tag)
+ return queryset
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)
+ tags = self.tag_model.get_tag_list(tags)
+ if not tags:
+ return queryset.none()
+ # TODO: presumes reverse generic relation
+ return queryset.filter(tag_relations__tag__in=tags).distinct()
- 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):
+ def get_related(self, obj, queryset_or_model):
"""
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 []
+ # TODO: presumes reverse generic relation.
+ # Do we know it's 'tags'?
+ return queryset.filter(tag_relations__tag__in=obj.tags).annotate(
+ count=models.Count('pk')).order_by('-count').exclude(pk=obj.pk)
##########
class Meta:
db_table = '%s_relation' % model._meta.db_table
unique_together = (('tag', 'content_type', 'object_id'),)
+ app_label = model._meta.app_label
def obj_unicode(self):
try:
'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'),
+ 'content_object': GenericForeignKey('content_type', 'object_id'),
'__unicode__': obj_unicode,
}
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)
+ def __new__(mcs, name, bases, attrs):
+ model = super(TagMeta, mcs).__new__(mcs, 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)
fnp / wolnelektury.git / blobdiff