Fix with_entities usage in db queries

In order to retrieve shares with filters
pertaining to separate tables (shares, instances, metadata,
etc), we need to perform joined loads of those
respective database tables as necessary. After the
join, the query cannot select entities due to
Github issue #6253 - The following is an error when
the pattern is used:

sqlalchemy.exc.ArgumentError: Query has only expression-based entities - can't find property named "share_metadata".

sqlalchemy 1.4 has a performance improvement that
delays query processing [2] and disallows this
pattern of usage; we can use a query.count() instead.

In another instance, we can perform joins selectively
only if asked for.

[1] https://github.com/sqlalchemy/sqlalchemy/issues/625
[2] https://docs.sqlalchemy.org/en/14/changelog/migration_14.html#many-core-and-orm-statement-objects-now-perform-much-of-their-construction-and-validation-in-the-compile-phase

Change-Id: I8aa196c171bbc224cec06f517ea22c4e91cbc06a
Closes-Bug: #1926399
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>
(cherry picked from commit 6ace54c260)

manila/db/sqlalchemy/api.py

@@ -46,7 +46,6 @@ from sqlalchemy import MetaData
 from sqlalchemy import or_
 from sqlalchemy.orm import joinedload
 from sqlalchemy.orm import subqueryload
-from sqlalchemy.sql import distinct
 from sqlalchemy.sql.expression import literal
 from sqlalchemy.sql.expression import true
 from sqlalchemy.sql import func
@@ -2163,8 +2162,7 @@ def _share_get_all_with_filters(context, project_id=None, share_server_id=None,
     # NOTE(carloss): Count must be calculated before limit and offset are
     # applied into the query.
     if show_count:
-        count = query.with_entities(
-            func.count(distinct(models.Share.id))).scalar()
+        count = query.count()
 
     if 'limit' in filters:
         offset = filters.get('offset', 0)
@@ -5266,11 +5264,7 @@ def _share_group_snapshot_get_all(
         sort_dir = 'desc'
 
     query = model_query(
-        context, models.ShareGroupSnapshot, session=session, read_deleted='no',
-    ).options(
-        joinedload('share_group'),
-        joinedload('share_group_snapshot_members'),
-    )
+        context, models.ShareGroupSnapshot, session=session, read_deleted='no')
 
     # Apply filters
     if not filters:
@@ -5295,7 +5289,10 @@ def _share_group_snapshot_get_all(
         raise exception.InvalidInput(reason=msg)
 
     if detailed:
-        return query.all()
+        return query.options(
+            joinedload('share_group'),
+            joinedload('share_group_snapshot_members')
+        ).all()
     else:
         query = query.with_entities(models.ShareGroupSnapshot.id,
                                     models.ShareGroupSnapshot.name)