Reactivity on computed from query


I’ve made a table from a complexe mongo document.
Header & first collumn values are computed from a query result. Unfortunately my table is not reactive.

Name X1 X2

Here is a sample of code

Template.Table.onCreated(function () {
  this.header = new ReactiveVar([]);
  this.firstcolumn = new ReactiveVar([]);
  const instance = Template.instance();

  this.autorun(function() {
      const subscription = instance.subscribe('table');
      if(subscription.ready()) {

 function updateTable() {
    const instance = Template.instance();
    const samples = SampleData.find({})
    const header = new Set();
    const firstcolumn = new Set();
    // Do some stuff, filling Set
    //Avoid infinite loop
    Tracker.nonreactive(() => {

Could you tell me how could I re-run updateTable() when SampleData.find({}) changes please ?

Do you need to process the entire collection before rendering the table, or does each document correspond to an individual row?

I need to process the entire collection (I’ve done filtering in publicating already), because each cell could contains a nested document that I need to place in the table in the proper line and column

There are a couple of things I would change in your code, but I don’t think they’d affect the running of the recomputation. However, you haven’t shown how you’re rendering the table. Is the problem with the (re)rendering, or with the reactive updateTable()?

This is just a sample of code, I can’t publish the real code behind this because not my own.
The rendering seems to works well. Additionnaly, I listen events to move columns to the right/left in UI only, that’s why I use ReactiveVar and this part works.

But I agree there are some optimisations to do, because changing columns order will need re-rendering, that will need to query database. And I’m not sure these database calls are clientside only.

Well, other than some very general suggestions, I can’t do much more:

  1. Use a ReactiveVar for the table data as well as the headers, or …
  2. Use a local, client-only collection for the table and make use of standard helpers.