Require Ord for ComparableDoc.

src/collector/sort_key/order.rs

@@ -12,7 +12,7 @@ pub trait Comparator<T>: Send + Sync + std::fmt::Debug + Default {
     fn compare(&self, lhs: &T, rhs: &T) -> Ordering;
     /// Return the order between two ComparableDoc values.
     #[inline(always)]
-    fn compare_doc<D: PartialOrd>(
+    fn compare_doc<D: Ord>(
         &self,
         lhs: &ComparableDoc<T, D>,
         rhs: &ComparableDoc<T, D>,
@@ -21,7 +21,7 @@ pub trait Comparator<T>: Send + Sync + std::fmt::Debug + Default {
             // In case of a tie on the feature, we always sort by descending `DocAddress` in order
             // to ensure a stable sorting of the documents. See the TopNComputer docs for more
             // information.
-            rhs.doc.partial_cmp(&lhs.doc).unwrap_or(Ordering::Equal)
+            rhs.doc.cmp(&lhs.doc)
         })
     }
 }

src/collector/top_collector.rs

@@ -6,17 +6,15 @@ use serde::{Deserialize, Serialize};
 #[derive(Clone, Default, Eq, PartialEq, Serialize, Deserialize)]
 pub struct ComparableDoc<T, D> {
     /// The feature of the document. In practice, this is
-    /// is any type that implements `PartialOrd`.
+    /// is a type which can be compared with a `Comparator<T>`.
     pub sort_key: T,
-    /// The document address. In practice, this is any
-    /// type that implements `PartialOrd`, and is guaranteed
-    /// to be unique for each document.
+    /// The document address. In practice, this is either a `DocId` or `DocAddress`.
     pub doc: D,
 }
 
 impl<T: std::fmt::Debug, D: std::fmt::Debug> std::fmt::Debug for ComparableDoc<T, D> {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
-        f.debug_struct(format!("ComparableDoc").as_str())
+        f.debug_struct("ComparableDoc")
             .field("feature", &self.sort_key)
             .field("doc", &self.doc)
             .finish()