optimize getting just the id as well

backend/onyx/db/document.py

@@ -104,28 +104,24 @@ def construct_document_select_for_connector_credential_pair_by_needs_sync(
 def construct_document_id_select_for_connector_credential_pair_by_needs_sync(
     connector_id: int, credential_id: int
 ) -> Select:
-    initial_doc_ids_stmt = select(DocumentByConnectorCredentialPair.id).where(
-        and_(
-            DocumentByConnectorCredentialPair.connector_id == connector_id,
-            DocumentByConnectorCredentialPair.credential_id == credential_id,
-        )
-    )
-
-    stmt = (
+    return (
         select(DbDocument.id)
+        .join(
+            DocumentByConnectorCredentialPair,
+            DbDocument.id == DocumentByConnectorCredentialPair.id,
+        )
         .where(
-            DbDocument.id.in_(initial_doc_ids_stmt),
-            or_(
-                DbDocument.last_modified
-                > DbDocument.last_synced,  # last_modified is newer than last_synced
-                DbDocument.last_synced.is_(None),  # never synced
-            ),
+            and_(
+                DocumentByConnectorCredentialPair.connector_id == connector_id,
+                DocumentByConnectorCredentialPair.credential_id == credential_id,
+                or_(
+                    DbDocument.last_modified > DbDocument.last_synced,
+                    DbDocument.last_synced.is_(None),
+                ),
+            )
         )
-        .distinct()
     )
 
-    return stmt
-
 
 def get_all_documents_needing_vespa_sync_for_cc_pair(
     db_session: Session, cc_pair_id: int