Expose boost query (#250)

src/query.rs

@@ -178,4 +178,13 @@ impl Query {
             inner: Box::new(dismax_query),
         })
     }
+
+    #[staticmethod]
+    #[pyo3(signature = (query, boost))]
+    pub(crate) fn boost_query(query: Query, boost: f32) -> PyResult<Query> {
+        let inner = tv::query::BoostQuery::new(query.inner, boost);
+        Ok(Query {
+            inner: Box::new(inner),
+        })
+    }
 }

tantivy/tantivy.pyi

@@ -212,6 +212,10 @@ class Query:
     @staticmethod
     def disjunction_max_query(subqueries: Sequence[Query], tie_breaker: Optional[float] = None) -> Query:
         pass
+    
+    @staticmethod
+    def boost_query(query: Query, boost: float) -> Query:
+        pass
 
 
 class Order(Enum):

tests/tantivy_test.py

@@ -827,20 +827,20 @@ class TestQuery(object):
             (Occur.Must, query1), 
             (Occur.Must, query2)
         ])
-        
+
         # no document should match both queries
         result = index.searcher().search(query, 10)
         assert len(result.hits) == 0
-        
+
         query = Query.boolean_query([
             (Occur.Should, query1), 
             (Occur.Should, query2)
         ])
-        
+
         # two documents should match, one for each query
         result = index.searcher().search(query, 10)
         assert len(result.hits) == 2
-        
+
         titles = set()
         for _, doc_address in result.hits:
             titles.update(index.searcher().doc(doc_address)["title"])
@@ -848,31 +848,31 @@ class TestQuery(object):
             "The Old Man and the Sea" in titles and  
             "Of Mice and Men" in titles
         )
-        
+
         query = Query.boolean_query([
             (Occur.MustNot, query1), 
             (Occur.Must, query1)
         ])
-        
+
         # must not should take precedence over must
         result = index.searcher().search(query, 10)
         assert len(result.hits) == 0
-        
+
         query = Query.boolean_query((
             (Occur.Should, query1), 
             (Occur.Should, query2)
         ))
-        
+
         # the Vec signature should fit the tuple signature
         result = index.searcher().search(query, 10)
         assert len(result.hits) == 2
-        
+
         # test invalid queries
         with pytest.raises(ValueError, match = "expected tuple of length 2, but got tuple of length 3"):
             Query.boolean_query([
                 (Occur.Must, Occur.Must, query1),
             ])
-        
+
         # test swapping the order of the tuple
         with pytest.raises(TypeError, match = r"'Query' object cannot be converted to 'Occur'"):
             Query.boolean_query([
@@ -899,3 +899,99 @@ class TestQuery(object):
 
         with pytest.raises(TypeError, match = r"'str' object cannot be converted to 'Query'"):
             query = Query.disjunction_max_query([query1, "not a query"], tie_breaker=0.5)
+
+
+    def test_boost_query(self, ram_index):
+        index = ram_index
+        query1 = Query.term_query(index.schema, "title", "sea")
+        boosted_query = Query.boost_query(query1, 2.0)
+
+        # Normal boost query
+        assert (
+            repr(boosted_query)
+            == """Query(Boost(query=TermQuery(Term(field=0, type=Str, "sea")), boost=2))"""
+        )
+
+        query2 = Query.fuzzy_term_query(index.schema, "title", "ice")
+        combined_query = Query.boolean_query([
+            (Occur.Should, boosted_query), 
+            (Occur.Should, query2)
+        ])
+        boosted_query = Query.boost_query(combined_query, 2.0)
+
+        # Boosted boolean query
+        assert (
+            repr(boosted_query)
+            == """Query(Boost(query=BooleanQuery { subqueries: [(Should, Boost(query=TermQuery(Term(field=0, type=Str, "sea")), boost=2)), (Should, FuzzyTermQuery { term: Term(field=0, type=Str, "ice"), distance: 1, transposition_cost_one: true, prefix: false })] }, boost=2))"""
+        )
+
+        boosted_query = Query.boost_query(query1, 0.1)
+
+        # Check for decimal boost values
+        assert(
+            repr(boosted_query)
+            == """Query(Boost(query=TermQuery(Term(field=0, type=Str, "sea")), boost=0.1))"""
+        )
+
+        boosted_query = Query.boost_query(query1, 0.0)
+
+        # Check for zero boost values
+        assert(
+            repr(boosted_query)
+            == """Query(Boost(query=TermQuery(Term(field=0, type=Str, "sea")), boost=0))"""
+        )
+        result = index.searcher().search(boosted_query, 10)
+        for _score, _ in result.hits:
+            # the score should be 0.0
+            assert _score == pytest.approx(0.0)  
+
+        boosted_query = Query.boost_query(
+            Query.boost_query(
+                query1, 0.1
+            ), 0.1
+        )
+
+        # Check for nested boost queries
+        assert(
+            repr(boosted_query)
+            == """Query(Boost(query=Boost(query=TermQuery(Term(field=0, type=Str, "sea")), boost=0.1), boost=0.1))"""
+        )
+        result = index.searcher().search(boosted_query, 10)
+        for _score, _ in result.hits:
+            # the score should be very small, due to 
+            # the unknown score of BM25, we can only check for the relative difference
+            assert _score == pytest.approx(0.01, rel = 1)  
+
+
+        boosted_query = Query.boost_query(
+            query1, -0.1
+        )
+
+        # Check for negative boost values
+        assert(
+            repr(boosted_query)
+            == """Query(Boost(query=TermQuery(Term(field=0, type=Str, "sea")), boost=-0.1))"""
+        )
+
+        result = index.searcher().search(boosted_query, 10)
+        # Even with a negative boost, the query should still match the document
+        assert len(result.hits) == 1
+        titles = set()
+        for _score, doc_address in result.hits:
+
+            # the score should be negative
+            assert _score < 0
+            titles.update(index.searcher().doc(doc_address)["title"])
+        assert titles == {"The Old Man and the Sea"}
+
+        # wrong query type
+        with pytest.raises(TypeError, match = r"'int' object cannot be converted to 'Query'"):
+            Query.boost_query(1, 0.1)
+
+        # wrong boost type
+        with pytest.raises(TypeError, match = r"argument 'boost': must be real number, not str"):
+            Query.boost_query(query1, "0.1")
+        
+        # no boost type error
+        with pytest.raises(TypeError, match = r"Query.boost_query\(\) missing 1 required positional argument: 'boost'"):
+            Query.boost_query(query1)