Add values_tuple() accessor to DataCoordinate.

python/lsst/daf/butler/core/dimensions/_coordinate.py

@@ -527,6 +527,16 @@ def full(self) -> NamedKeyMapping[Dimension, DataIdValue]:
         assert self.hasFull(), "full may only be accessed if hasFull() returns True."
         return _DataCoordinateFullView(self)
 
+    @abstractmethod
+    def values_tuple(self) -> tuple[DataIdValue, ...]:
+        """Return the required values (only) of this data ID as a tuple.
+
+        In contexts where all data IDs have the same dimensions, comparing and
+        hashing these tuples can be *much* faster than comparing the original
+        `DataCoordinate` instances.
+        """
+        raise NotImplementedError()
+
     @abstractmethod
     def hasRecords(self) -> bool:
         """Whether this data ID contains records.
@@ -954,6 +964,10 @@ def hasRecords(self) -> bool:
         # Docstring inherited from DataCoordinate.
         return False
 
+    def values_tuple(self) -> tuple[DataIdValue, ...]:
+        # Docstring inherited from DataCoordinate.
+        return self._values[: len(self._graph.required)]
+
     def _record(self, name: str) -> DimensionRecord | None:
         # Docstring inherited from DataCoordinate.
         raise AssertionError()