Question

I use datatables on the client to allow speedy live sorting/filtering of around 10,000 rows of data. It is much faster to supply an array of rows to a DataTable during table creation than to add the rows individually. I can use the onReady function in subscribe to achieve this.
If I then call observe to pick up changes, I get the data already supplied in subscribe again.

While I can hack around this, I presume I am just not using meteor correctly and appreciate any advice.

Here is some sample code:

Meteor.subscribe("books", function(){
    // Runs when subscription is complete
    var mData = Books.find().fetch();

    MyTable = $('#testTable').dataTable( {
        'aoColumns': [
            { sTitle: 'title', sClass: 'alignRight', mDataProp: 'title'},
        ],
        'aaData' : mData
    });
    // Add any new books.
    Books.find().observe({added: function(item){
        // ERR: Adds the books already fetched into mData as well as any new books.
        MyTable.fnAddData([item]);
    }});
});

Answer 1

There’s a hidden option to observe ({_suppress_initial: true}) that avoids this behaviour. I’m not sure if it’s a good idea to use it, but it is there.

As for advice around how to structure your code; it’s not as easy as it should be, but I think you want to something like the following:

1. Wrap your table in a {{#constant}} helper so it never gets re-rendered.

2. Make sure the table doesn’t get rendered the one-and-only time until the data is ready (this could help: https://github.com/oortcloud/unofficial-meteor-faq#how-do-i-know-when-my-subscription-is-ready-and-not-still-loading)

3. Do your code above in the table’s Template.table.rendered callback.

That approach seems more modular.