presto-main/src/main/java/io/prestosql/execution/TaskManagerConfig.java/TaskManagerConfig/setTaskConcurrency
class TaskManagerConfig:    @Config("task.concurrency")
    @ConfigDescription("Default number of local parallel jobs per worker")
    public TaskManagerConfig setTaskConcurrency(int taskConcurrency)
    {
        this.taskConcurrency = taskConcurrency;
        return this;
    }