Where should I subscribe and fetch data in react?

I used to sub and fetch and return data in getMeteorData, but, it seems ineffective. For example, if I subscribe('items'), and let items = Items.find({}).fetch(), every time a new item is added, the find is rerun totally.

Here’s an example from my app:

getMeteorData() {
    const projectId = FlowRouter.getParam("_id")
    const taskId = FlowRouter.getParam("taskId")
    const taskLoaded = Meteor.subscribe("taskDetails", projectId, taskId)
    return {
      task: Tasks.findOne({_id: taskId})

Then you reference this.data.task in your render() function

this is the normal way to use ReactMeteorData, but I found it ineffective. it will auto rerun every time Tasks collection changed.