Expose const score query (#256)

src/query.rs

@@ -157,6 +157,7 @@ impl Query {
         })
     }
 
+    /// Construct a Tantivy's BooleanQuery
     #[staticmethod]
     #[pyo3(signature = (subqueries))]
     pub(crate) fn boolean_query(
@@ -199,6 +200,7 @@ impl Query {
         })
     }
 
+    /// Construct a Tantivy's BoostQuery
     #[staticmethod]
     #[pyo3(signature = (query, boost))]
     pub(crate) fn boost_query(query: Query, boost: f32) -> PyResult<Query> {
@@ -208,6 +210,7 @@ impl Query {
         })
     }
 
+    /// Construct a Tantivy's RegexQuery
     #[staticmethod]
     #[pyo3(signature = (schema, field_name, regex_pattern))]
     pub(crate) fn regex_query(
@@ -226,4 +229,17 @@ impl Query {
             Err(e) => Err(to_pyerr(e)),
         }
     }
+
+    /// Construct a Tantivy's ConstScoreQuery
+    #[staticmethod]
+    #[pyo3(signature = (query, score))]
+    pub(crate) fn const_score_query(
+        query: Query,
+        score: f32,
+    ) -> PyResult<Query> {
+        let inner = tv::query::ConstScoreQuery::new(query.inner, score);
+        Ok(Query {
+            inner: Box::new(inner),
+        })
+    }
 }

tantivy/tantivy.pyi

@@ -233,6 +233,10 @@ class Query:
     def regex_query(schema: Schema, field_name: str, regex_pattern: str) -> Query:
         pass
 
+    @staticmethod
+    def const_score_query(query: Query, score: float) -> Query:
+        pass
+    
 class Order(Enum):
     Asc = 1
     Desc = 2

tests/tantivy_test.py

@@ -1057,3 +1057,34 @@ class TestQuery(object):
             ValueError, match=r"An invalid argument was passed: 'fish\('"
         ):
             Query.regex_query(index.schema, "body", "fish(")
+
+    def test_const_score_query(self, ram_index):
+        index = ram_index
+
+        query = Query.regex_query(index.schema, "body", "fish")
+        const_score_query = Query.const_score_query(
+            query, score = 1.0
+        )
+        result = index.searcher().search(const_score_query, 10)
+        assert len(result.hits) == 1
+        score, _ = result.hits[0]
+        # the score should be 1.0
+        assert score == pytest.approx(1.0)
+        
+        const_score_query = Query.const_score_query(
+            Query.const_score_query(
+                query, score = 1.0
+            ), score = 0.5
+        )
+        
+        result = index.searcher().search(const_score_query, 10)
+        assert len(result.hits) == 1
+        score, _ = result.hits[0]
+        # nested const score queries should retain the 
+        # score of the outer query
+        assert score == pytest.approx(0.5)
+        
+        # wrong score type
+        with pytest.raises(TypeError, match = r"argument 'score': must be real number, not str"):
+            Query.const_score_query(query, "0.1")
+