Fix problems with the "role" GUC and parallel query.

Without this fix, dropping a role can sometimes result in parallel
query failures in sessions that have used "SET ROLE" to assume the
dropped role, even if that setting isn't active any more.

Report by Pavan Deolasee.  Patch by Amit Kapila, reviewed by me.

Discussion: http://postgr.es/m/CABOikdOomRcZsLsLK+Z+qENM1zxyaWnAvFh3MJZzZnnKiF+REg@mail.gmail.com

1 files changed, 11 insertions, 0 deletions

diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index d683050733..1f542ed8d8 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -75,9 +75,11 @@ typedef struct FixedParallelState
 	Oid			database_id;
 	Oid			authenticated_user_id;
 	Oid			current_user_id;
+	Oid			outer_user_id;
 	Oid			temp_namespace_id;
 	Oid			temp_toast_namespace_id;
 	int			sec_context;
+	bool		is_superuser;
 	PGPROC	   *parallel_master_pgproc;
 	pid_t		parallel_master_pid;
 	BackendId	parallel_master_backend_id;
@@ -296,6 +298,8 @@ InitializeParallelDSM(ParallelContext *pcxt)
 		shm_toc_allocate(pcxt->toc, sizeof(FixedParallelState));
 	fps->database_id = MyDatabaseId;
 	fps->authenticated_user_id = GetAuthenticatedUserId();
+	fps->outer_user_id = GetCurrentRoleId();
+	fps->is_superuser = session_auth_is_superuser;
 	GetUserIdAndSecContext(&fps->current_user_id, &fps->sec_context);
 	GetTempNamespaceState(&fps->temp_namespace_id,
 						  &fps->temp_toast_namespace_id);
@@ -1115,6 +1119,13 @@ ParallelWorkerMain(Datum main_arg)
 	 */
 	InvalidateSystemCaches();
 
+	/*
+	 * Restore current role id.  Skip verifying whether session user is
+	 * allowed to become this role and blindly restore the leader's state for
+	 * current role.
+	 */
+	SetCurrentRoleId(fps->outer_user_id, fps->is_superuser);
+
 	/* Restore user ID and security context. */
 	SetUserIdAndSecContext(fps->current_user_id, fps->sec_context);