Merge pull request #276 from laws-africa/filter-facets

Add FacetedFilterSearchFilterBackend

Author: barseghyanartur

docs/advanced_usage_examples.rst

@@ -754,6 +754,68 @@ In the example below, we show results with faceted ``state`` and
 
     http://127.0.0.1:8000/search/books/?facet=state&facet=pages_count
 
+Faceted and filtered search
+---------------------------
+
+It is sometimes useful to be able to facet and filter on the same field. For example, this would allow the user
+to apply a filter such as `size=medium` and a `size` facet, and get back a `size` facet that has all sizes, not
+just `medium`. This is similar to
+`elasticsearch-dsl's FacetedSearch class<https://elasticsearch-dsl.readthedocs.io/en/latest/faceted_search.html>`_.
+
+To do this, use `FacetedFilterSearchFilterBackend` instead of both `FacetedSearchFilterBackend` and
+`FilteringFilterBackend`. It will apply both the filters and the facets. It uses exactly the same configuration
+as the two backends it replaces.
+
+*search_indexes/viewsets/book.py*
+
+.. code-block:: python
+
+    # ...
+
+    from django_elasticsearch_dsl_drf.filter_backends import (
+        # ...
+        FacetedFilterSearchFilterBackend,
+    )
+
+    # ...
+
+    from elasticsearch_dsl import (
+        DateHistogramFacet,
+        RangeFacet,
+        TermsFacet,
+    )
+
+    # ...
+
+    class BookDocumentView(DocumentViewSet):
+        """The BookDocument view."""
+
+        # ...
+
+        filter_backends = [
+            # ...
+            FacetedFilterSearchFilterBackend,
+        ]
+
+        # ...
+
+        filter_fields = {
+            'state': 'state.raw',  # The filter and facet fields MUST both use the same elasticsearch field
+        }
+
+        faceted_search_fields = {
+            'state': 'state.raw',  # The filter and facet fields MUST both use the same elasticsearch field
+        }
+
+        # ...
+
+In the example below, we show results with faceted `state` and the
+filter `state=published`.
+
+.. code-block:: text
+
+    http://127.0.0.1:8000/search/books/?facet=state&state=published
+
 Post-filter
 -----------
 The `post_filter` is very similar to the common filter. The only difference

docs/changelog.rst

@@ -15,6 +15,13 @@ are used for versioning (schema follows below):
   0.3.4 to 0.4).
 - All backwards incompatible changes are mentioned in this document.
 
+0.23
+----
+?
+
+- Add `FacetedFilterSearchFilterBackend` that performs faceting and filtering
+  together.
+
 0.22.2
 ----
 2021-08-29

examples/simple/search_indexes/urls.py

@@ -24,6 +24,7 @@
     BookSimpleQueryStringBoostSearchFilterBackendDocumentViewSet,
     BookSimpleQueryStringSearchFilterBackendDocumentViewSet,
     BookSourceSearchBackendDocumentViewSet,
+    FacetedFilteredBookDocumentViewSet,
     JournalDocumentViewSet,
     CityCompoundSearchBackendDocumentViewSet,
     CityDocumentViewSet,
@@ -206,6 +207,12 @@
     basename='bookdocument_simple_query_string_boost_search_backend'
 )
 
+router.register(
+    r'books-faceted-filtered',
+    FacetedFilteredBookDocumentViewSet,
+    basename='bookdocument_faceted_filtered'
+)
+
 # **********************************************************
 # ************************* Cities *************************
 # **********************************************************

examples/simple/search_indexes/viewsets/__init__.py

@@ -35,6 +35,7 @@
     'CityDocumentViewSet',
     'JournalDocumentViewSet',
     'FrontAddressDocumentViewSet',
+    'FacetedFilteredBookDocumentViewSet',
     'LocationDocumentViewSet',
     'PublisherDocumentViewSet',
     'QueryFriendlyPaginationBookDocumentViewSet',

examples/simple/search_indexes/viewsets/book/__init__.py

@@ -3,6 +3,7 @@
 from .compound_search_boost import *
 from .default import *
 from .default_filter_lookup import *
+from .faceted_filtered import *
 from .functional_suggester import *
 from .ignore_index_errors import *
 from .frontend import *

examples/simple/search_indexes/viewsets/book/faceted_filtered.py

@@ -0,0 +1,29 @@
+from django_elasticsearch_dsl_drf.filter_backends import (
+    DefaultOrderingFilterBackend,
+    FacetedFilterSearchFilterBackend,
+)
+
+from .base import BaseBookDocumentViewSet
+
+
+__all__ = (
+    'FacetedFilteredBookDocumentViewSet',
+)
+
+
+class FacetedFilteredBookDocumentViewSet(BaseBookDocumentViewSet):
+    """The BookDocument view with faceted filtering."""
+
+    filter_backends = [
+        FacetedFilterSearchFilterBackend,
+        DefaultOrderingFilterBackend,
+    ]
+
+    filter_fields = {
+        'title': 'title.raw',
+        'state': 'state.raw',
+    }
+
+    faceted_search_fields = {
+        'state': 'state.raw',
+    }

src/django_elasticsearch_dsl_drf/filter_backends/__init__.py

@@ -2,7 +2,10 @@
 All filter backends.
 """
 
-from .faceted_search import FacetedSearchFilterBackend
+from .faceted_search import (
+    FacetedSearchFilterBackend,
+    FacetedFilterSearchFilterBackend
+)
 from .filtering import (
     FilteringFilterBackend,
     GeoSpatialFilteringFilterBackend,

src/django_elasticsearch_dsl_drf/filter_backends/faceted_search.py

@@ -2,6 +2,8 @@
 Faceted search backend.
 """
 import copy
+from collections import defaultdict
+
 from elasticsearch_dsl import TermsFacet
 from elasticsearch_dsl.query import Q
 
@@ -13,7 +15,9 @@
 __author__ = 'Artur Barseghyan <[email protected]>'
 __copyright__ = '2017-2020 Artur Barseghyan'
 __license__ = 'GPL 2.0/LGPL 2.1'
-__all__ = ('FacetedSearchFilterBackend',)
+__all__ = ('FacetedSearchFilterBackend', 'FacetedFilterSearchFilterBackend')
+
+from django_elasticsearch_dsl_drf.filter_backends.filtering import FilteringFilterBackend
 
 
 class FacetedSearchFilterBackend(BaseFilterBackend):
@@ -229,3 +233,91 @@ def filter_queryset(self, request, queryset, view):
         :rtype: elasticsearch_dsl.search.Search
         """
         return self.aggregate(request, queryset, view)
+
+
+class FacetedFilterSearchFilterBackend(FilteringFilterBackend, FacetedSearchFilterBackend):
+    """ Combined faceting and filtering backend similar to elasticsearch-dsl's FacetedSearch class.
+    It combines the functionality of FilteringFilterBackend and FacetedSearchFilterBackend to take filters into
+    account when creating facets.
+
+    This backend uses the same configuration fields as FilteringFilterBackend and FacetedSearchFilterBackend.
+    This backend replaces their functionality and should not be used together with either of those backends.
+
+    Note that to work correctly, the actual elasticsearch field must be the same for a facet and its matching filter.
+    For example, if a facet will aggregate on field `state.raw`, then the filter must also filter on `state.raw`,
+    and not just `state`.
+
+    When creating a facet, filters for faceted fields other than for the current facet are applied. Filters
+    for faceted fields are then applied as post_filters. Filters on non-faceted fields are applied as normal filters.
+    """
+    def filter_queryset(self, request, queryset, view):
+        # the fact that apply_filter is a classmethod means we can't store state on self,
+        # so we hitch it onto queryset
+        queryset._facets = self.construct_facets(request, view)
+        queryset._faceted_fields = set(f['facet']._params['field'] for f in queryset._facets.values())
+        queryset._filters = defaultdict(list)
+
+        # apply filters
+        queryset = FilteringFilterBackend.filter_queryset(self, request, queryset, view)
+
+        # apply aggregations
+        return self.aggregate(request, queryset, view)
+
+    @classmethod
+    def apply_filter(cls, queryset, options=None, args=None, kwargs=None):
+        if args is None:
+            args = []
+        if kwargs is None:
+            kwargs = {}
+
+        facets = queryset._facets
+        faceted_fields = queryset._faceted_fields
+        filters = queryset._filters
+
+        # if this field is faceted, then apply it as a post-filter
+        if options['field'] in faceted_fields:
+            queryset = queryset.post_filter(*args, **kwargs)
+        else:
+            queryset = queryset.filter(*args, **kwargs)
+
+        filters[options['field']].append(Q(*args, **kwargs))
+
+        # ensure the new queryset object retains the helper variables
+        queryset._facets = facets
+        queryset._faceted_fields = faceted_fields
+        queryset._filters = filters
+        return queryset
+
+    def aggregate(self, request, queryset, view):
+        facets = queryset._facets
+        faceted_fields = queryset._faceted_fields
+        filters = queryset._filters
+
+        for field, facet in facets.items():
+            agg = facet['facet'].get_aggregation()
+
+            if facet['global']:
+                queryset.aggs.bucket(
+                    '_filter_' + field,
+                    'global'
+                ).bucket(field, agg)
+                continue
+
+            agg_filter = Q('match_all')
+            for f, _filter in filters.items():
+                # apply filters for that are applicable for facets other than this one
+                if agg.field == f or f not in faceted_fields:
+                    continue
+                # combine with or
+                q = _filter[0]
+                for x in _filter[1:]:
+                    q = q | x
+                agg_filter &= q
+
+            queryset.aggs.bucket(
+                '_filter_' + field,
+                'filter',
+                filter=agg_filter
+            ).bucket(field, agg)
+
+        return queryset