Expose Tantivy's DisjunctionMaxQuery (#244)

Co-authored-by: Caleb Hattingh <caleb.hattingh@gmail.com>

src/query.rs

@@ -1,6 +1,8 @@
 use crate::{make_term, Schema};
 use pyo3::{
-    exceptions, prelude::*, types::PyAny, types::PyString, types::PyTuple,
+    exceptions,
+    prelude::*,
+    types::{PyAny, PyFloat, PyString, PyTuple},
 };
 use tantivy as tv;
 
@@ -151,4 +153,29 @@ impl Query {
             inner: Box::new(inner),
         })
     }
+
+    /// Construct a Tantivy's DisjunctionMaxQuery
+    #[staticmethod]
+    pub(crate) fn disjunction_max_query(
+        subqueries: Vec<Query>,
+        tie_breaker: Option<&PyFloat>,
+    ) -> PyResult<Query> {
+        let inner_queries: Vec<Box<dyn tv::query::Query>> = subqueries
+            .iter()
+            .map(|query| query.inner.box_clone())
+            .collect();
+
+        let dismax_query = if let Some(tie_breaker) = tie_breaker {
+            tv::query::DisjunctionMaxQuery::with_tie_breaker(
+                inner_queries,
+                tie_breaker.extract::<f32>()?,
+            )
+        } else {
+            tv::query::DisjunctionMaxQuery::new(inner_queries)
+        };
+
+        Ok(Query {
+            inner: Box::new(dismax_query),
+        })
+    }
 }

tantivy/tantivy.pyi

@@ -209,6 +209,11 @@ class Query:
     def boolean_query(subqueries: Sequence[tuple[Occur, Query]]) -> Query:
         pass
 
+    @staticmethod
+    def disjunction_max_query(subqueries: Sequence[Query], tie_breaker: Optional[float] = None) -> Query:
+        pass
+
+
 class Order(Enum):
     Asc = 1
     Desc = 2

tests/tantivy_test.py

@@ -878,3 +878,24 @@ class TestQuery(object):
             Query.boolean_query([
                 (query1, Occur.Must),
             ])
+
+    def test_disjunction_max_query(self, ram_index):
+        index = ram_index
+
+        # query1 should match the doc: "The Old Man and the Sea"
+        query1 = Query.term_query(index.schema, "title", "sea")
+        # query2 should matches the doc: "Of Mice and Men"
+        query2 = Query.term_query(index.schema, "title", "mice")
+        # the disjunction max query should match both docs.
+        query = Query.disjunction_max_query([query1, query2])
+
+        result = index.searcher().search(query, 10)
+        assert len(result.hits) == 2
+
+        # the disjunction max query should also take a tie_breaker parameter
+        query = Query.disjunction_max_query([query1, query2], tie_breaker=0.5)
+        result = index.searcher().search(query, 10)
+        assert len(result.hits) == 2
+
+        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)