Adaptive executor: use 2PC when replication_factor > 1

src/backend/distributed/executor/adaptive_executor.c

@@ -938,35 +938,16 @@ DistributedExecutionRequiresRollback(DistributedExecution *execution)
 		return true;
 	}
 
-	/*
-	 * Checking the first task's placement list is not sufficient for all purposes since
-	 * for append/range distributed tables we might have unequal number of placements for
-	 * shards. However, it is safe to do here, because we're searching for a reference
-	 * table. All other cases return false for this purpose.
-	 */
-	task = (Task *) linitial(taskList);
 	if (list_length(task->taskPlacementList) > 1)
 	{
 		/*
-		 * Some tasks don't set replicationModel thus we only
+		 * Adaptive executor opts to error out on queries if a placement is unhealthy,
-		 * rely on the anchorShardId, not replicationModel.
+		 * not marking the placement itself unhealthy in the process.
-		 *
+		 * Use 2PC to rollback placements before the unhealthy shard failed.
-		 * TODO: Do we ever need replicationModel in the Task structure?
-		 * Can't we always rely on anchorShardId?
 		 */
-		uint64 anchorShardId = task->anchorShardId;
-		if (anchorShardId != INVALID_SHARD_ID && ReferenceTableShardId(anchorShardId))
-		{
 		return true;
 	}
 
-		/*
-		 * Single DML/DDL tasks with replicated tables (non-reference)
-		 * should not require BEGIN/COMMIT/ROLLBACK.
-		 */
-		return false;
-	}
-
 	return false;
 }