JSON file with MCParticle tree cannot be opened

[tmadlener]

This is not the highest priority, but we have encountered an issue with opening some json files, e.g. the following one (which contains a rather large MCParticle tree from a calorimeter shower). I don't think the size of the file is a problem, but I suspect that potentially a slightly newer version of podio or EDM4hep could be one?

test_mc_shower.edm4hep.json

What we get is the following error:

If you know where the error is coming from, I can also try to have a look myself to see if I can fix this.

[brauliorivas]

So it turns out that the file only has Event 1, so when selecting an event, it automatically chooses 0, but it doesn't exist 😄. That's why it can't find any MC particle tree. However, in that case, we could improve the event input, and automatically select the first event it finds.
Also, on my PC it does not even run (can't show the particles on the Canvas because my PC is slow. i5 11gen with 8ram). So it means that we would have to improve performance sooner or later.

[tmadlener]

Ah right, I thought I had tried to go to 1 in the selection with the same issue, but it does indeed seem to work if I select the event number. Can the file be partially read to populate a dropdown menu to select the event?

Another issue that I observed with this JSON file is that at least chrome really struggles to display it (goes up to 3GB of RAM for me and I still don't see a graph 😅). Might just be that this file with approx. 18k MCParticles is too big to be displayed. I wouldn't too much emphasis on the performance part yet, but at least we would have an input file to use for performance testing and developments.