Add moreLikeThis lookup.

Author: WaVEV

django_mongodb_backend/compiler.py

@@ -109,36 +109,35 @@ def _prepare_expressions_for_pipeline(self, expression, target, annotation_group
             replacements[sub_expr] = self._get_replace_expr(sub_expr, group, alias)
         return replacements, group
 
-    def _prepare_search_expressions_for_pipeline(self, expression, target, search_idx):
+    def _prepare_search_expressions_for_pipeline(
+        self, expression, target, search_idx, replacements
+    ):
         searches = {}
-        replacements = {}
         for sub_expr in self._get_search_expressions(expression):
-            alias = f"__search_expr.search{next(search_idx)}"
-            replacements[sub_expr] = self._get_replace_expr(sub_expr, searches, alias)
-        return replacements, list(searches.values())
+            if sub_expr not in replacements:
+                alias = f"__search_expr.search{next(search_idx)}"
+                replacements[sub_expr] = self._get_replace_expr(sub_expr, searches, alias)
+        return list(searches.values())
 
     def _prepare_search_query_for_aggregation_pipeline(self, order_by):
         replacements = {}
         searches = []
         annotation_group_idx = itertools.count(start=1)
         for target, expr in self.query.annotation_select.items():
-            new_replacements, expr_searches = self._prepare_search_expressions_for_pipeline(
-                expr, target, annotation_group_idx
+            expr_searches = self._prepare_search_expressions_for_pipeline(
+                expr, target, annotation_group_idx, replacements
             )
-            replacements.update(new_replacements)
             searches += expr_searches
 
         for expr, _ in order_by:
-            new_replacements, expr_searches = self._prepare_search_expressions_for_pipeline(
-                expr, None, annotation_group_idx
+            expr_searches = self._prepare_search_expressions_for_pipeline(
+                expr, None, annotation_group_idx, replacements
             )
-            replacements.update(new_replacements)
             searches += expr_searches
 
-        having_replacements, having_group = self._prepare_search_expressions_for_pipeline(
-            self.having, None, annotation_group_idx
+        having_group = self._prepare_search_expressions_for_pipeline(
+            self.having, None, annotation_group_idx, replacements
         )
-        replacements.update(having_replacements)
         searches += having_group
         return searches, replacements
 

django_mongodb_backend/expressions/builtins.py

@@ -490,6 +490,8 @@ def as_mql(self, compiler, connection):
 
 
 class SearchMoreLikeThis(SearchExpression):
+    search_type = "more_like_this"
+
     def __init__(self, documents, score=None):
         self.documents = documents
         self.score = score

tests/queries_/test_search.py

@@ -11,6 +11,7 @@
     SearchGeoShape,
     SearchGeoWithin,
     SearchIn,
+    SearchMoreLikeThis,
     SearchPhrase,
     SearchRange,
     SearchRegex,
@@ -27,7 +28,7 @@ def _get_collection(self, model):
 
     def create_search_index(self, model, index_name, definition):
         collection = self._get_collection(model)
-        idx = SearchIndexModel(definition=definition, name="test_index")
+        idx = SearchIndexModel(definition=definition, name=index_name)
         collection.create_search_index(idx)
 
 
@@ -254,3 +255,44 @@ def test_search_geo_within(self):
             )
         )
         self.assertEqual(qs.first().number, 2)
+
+
+class SearchMoreLikeThisTest(TestCase, CreateIndexMixin):
+    def setUp(self):
+        self.create_search_index(
+            Article,
+            "mlt_index",
+            {
+                "mappings": {
+                    "dynamic": False,
+                    "fields": {"body": {"type": "string"}, "headline": {"type": "string"}},
+                }
+            },
+        )
+        self.article1 = Article.objects.create(
+            headline="Space exploration", number=1, body="Webb telescope"
+        )
+        self.article2 = Article.objects.create(
+            headline="The commodities fall",
+            number=2,
+            body="Commodities dropped sharply due to inflation concerns",
+        )
+        Article.objects.create(
+            headline="irrelevant",
+            number=3,
+            body="This is a completely unrelated article about cooking",
+        )
+        time.sleep(1)
+
+    def test_search_more_like_this(self):
+        like_docs = [
+            {"headline": self.article1.headline, "body": self.article1.body},
+            {"headline": self.article2.headline, "body": self.article2.body},
+        ]
+        like_docs = [{"body": "NASA launches new satellite to explore the galaxy"}]
+        qs = Article.objects.annotate(score=SearchMoreLikeThis(documents=like_docs)).order_by(
+            "score"
+        )
+        self.assertQuerySetEqual(
+            qs, ["space exploration", "The commodities fall"], lambda a: a.headline
+        )