Add scalars method to connection and session classes

Added new methods :meth:`_orm.Session.scalars`,
:meth:`_engine.Connection.scalars`, :meth:`_asyncio.AsyncSession.scalars`
and :meth:`_asyncio.AsyncSession.stream_scalars`, which provide a short cut
to the use case of receiving a row-oriented :class:`_result.Result` object
and converting it to a :class:`_result.ScalarResult` object via the
:meth:`_engine.Result.scalars` method, to return a list of values rather
than a list of rows. The new methods are analogous to the long existing
:meth:`_orm.Session.scalar` and :meth:`_engine.Connection.scalar` methods
used to return a single value from the first row only. Pull request
courtesy Miguel Grinberg.

Fixes: #6990
Closes: #6991
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/6991
Pull-request-sha: b3e0bb3042c55b0cc5af6a25cb3f31b929f88a47

Change-Id: Ia445775e24ca964b0162c2c8e5ca67dd1e39199f

1 files changed, 62 insertions, 0 deletions

diff --git a/lib/sqlalchemy/ext/asyncio/session.py b/lib/sqlalchemy/ext/asyncio/session.py
index e4372f448..6e3ac5a90 100644
--- a/lib/sqlalchemy/ext/asyncio/session.py
+++ b/lib/sqlalchemy/ext/asyncio/session.py
@@ -231,6 +231,37 @@ class AsyncSession(ReversibleProxy):
         )
         return result.scalar()
 
+    async def scalars(
+        self,
+        statement,
+        params=None,
+        execution_options=util.EMPTY_DICT,
+        bind_arguments=None,
+        **kw
+    ):
+        """Execute a statement and return scalar results.
+
+        :return: a :class:`_result.ScalarResult` object
+
+        .. versionadded:: 1.4.24
+
+        .. seealso::
+
+            :meth:`_orm.Session.scalars` - main documentation for scalars
+
+            :meth:`_asyncio.AsyncSession.stream_scalars` - streaming version
+
+        """
+
+        result = await self.execute(
+            statement,
+            params=params,
+            execution_options=execution_options,
+            bind_arguments=bind_arguments,
+            **kw
+        )
+        return result.scalars()
+
     async def get(
         self,
         entity,
@@ -287,6 +318,37 @@ class AsyncSession(ReversibleProxy):
         )
         return _result.AsyncResult(result)
 
+    async def stream_scalars(
+        self,
+        statement,
+        params=None,
+        execution_options=util.EMPTY_DICT,
+        bind_arguments=None,
+        **kw
+    ):
+        """Execute a statement and return a stream of scalar results.
+
+        :return: an :class:`_asyncio.AsyncScalarResult` object
+
+        .. versionadded:: 1.4.24
+
+        .. seealso::
+
+            :meth:`_orm.Session.scalars` - main documentation for scalars
+
+            :meth:`_asyncio.AsyncSession.scalars` - non streaming version
+
+        """
+
+        result = await self.stream(
+            statement,
+            params=params,
+            execution_options=execution_options,
+            bind_arguments=bind_arguments,
+            **kw
+        )
+        return result.scalars()
+
     async def delete(self, instance):
         """Mark an instance as deleted.