presto-main/src/main/java/io/prestosql/execution/TaskManagerConfig.java/TaskManagerConfig/setWriterCount
class TaskManagerConfig:    @Config("task.writer-count")
    @ConfigDescription("Number of writers per task")
    public TaskManagerConfig setWriterCount(int writerCount)
    {
        this.writerCount = writerCount;
        return this;
    }