Use correct connection for cancellation in frontend's parallel slots

michaelpq · pull[bot] · commit 914d46bcad29 · 2023-02-12T13:53:02.000Z
While waiting for slots to become available in wait_on_slots() in parallel_slot.c, the cancellation always relied on the first connection in the set to do the job. This could cause problems when this slot's socket is gone as PQgetCancel() would return NULL in this case. Rather than always using the first connection, this changes the logic to use the first valid connection for the cancellation. Author: Ranier Vilela Reviewed-by: Justin Pryzby Discussion: https://postgr.es/m/CAEudQAokk1h_pUwGXsYS4oVOuf35s1O2o3TXGHpV8=AWikvgHA@mail.gmail.com Backpatch-through: 14
diff --git a/src/fe_utils/parallel_slot.c b/src/fe_utils/parallel_slot.c
@@ -235,7 +235,7 @@ wait_on_slots(ParallelSlotArray *sa)
 	if (cancelconn == NULL)
 		return false;
 
-	SetCancelConn(sa->slots->connection);
+	SetCancelConn(cancelconn);
 	i = select_loop(maxFd, &slotset);
 	ResetCancelConn();
 
