diff --git a/datacube/drivers/postgres/_api.py b/datacube/drivers/postgres/_api.py
index 0129c2e91..d32034646 100644
--- a/datacube/drivers/postgres/_api.py
+++ b/datacube/drivers/postgres/_api.py
@@ -608,7 +608,7 @@ def _ob_exprs(o):
         if not source_exprs:
             return (
                 select(
-                    *select_columns
+                    *select_columns  # type: ignore[arg-type]
                 ).select_from(
                     from_expression
                 ).where(
diff --git a/datacube/index/abstract.py b/datacube/index/abstract.py
index a48131a18..05f3cab1e 100644
--- a/datacube/index/abstract.py
+++ b/datacube/index/abstract.py
@@ -16,6 +16,7 @@
 from uuid import UUID
 from datetime import timedelta
 from deprecat import deprecat
+from sqlalchemy import Function
 
 from odc.geo import CRS, Geometry
 from datacube.cfg.api import ODCEnvironment, ODCOptionHandler
@@ -1763,7 +1764,7 @@ def search_returning(self,
                          custom_offsets: Mapping[str, Offset] | None = None,
                          limit: int | None = None,
                          archived: bool | None = False,
-                         order_by: Iterable[str | Field | None] = None,
+                         order_by: Iterable[str | Field | Function] | None = None,
                          **query: QueryField
                         ) -> Iterable[tuple]:
         """
@@ -1783,8 +1784,8 @@ def search_returning(self,
         :param archived: False (default): Return active datasets only.
                          None: Include archived and active datasets.
                          True: Return archived datasets only.
-        :param order_by: a field name or field by which to sort output.  None is unsorted and may allow faster return
-                         of first result depending on the index driver's implementation.
+        :param order_by: a field name, field, or function by which to sort output.  None is unsorted and may allow
+                         faster return of first result depending on the index driver's implementation.
         :param geopolygon: Spatial search polygon (only supported if index supports_spatial_indexes)
         :param query: search query parameters
         :return: Namedtuple of requested fields, for each matching dataset.
diff --git a/datacube/index/memory/_datasets.py b/datacube/index/memory/_datasets.py
index b9e4ae0e4..0a56cef0f 100755
--- a/datacube/index/memory/_datasets.py
+++ b/datacube/index/memory/_datasets.py
@@ -13,6 +13,7 @@
 from time import monotonic
 from typing import (Any, Callable, Iterable, Mapping, Sequence, cast)
 from uuid import UUID
+from sqlalchemy import Function
 
 from datacube.migration import ODC2DeprecationWarning
 from datacube.index import fields
@@ -607,7 +608,7 @@ def search_returning(self,
                          custom_offsets: Mapping[str, Offset] | None = None,
                          limit: int | None = None,
                          archived: bool | None = False,
-                         order_by: str | Field | None = None,
+                         order_by: Iterable[str | Field | Function] | None = None,
                          **query: QueryField) -> Iterable[tuple]:
         if "geopolygon" in query:
             raise NotImplementedError("Spatial search index API not supported by this index.")