Plot 1 line per group term with a single query


I have some data in an elastic search DB like this:
timestamp: 1, mount_point: /home, usage: 80
timestamp: 1, mount_point: /var, usage: 60
timestamp: 2, mount_point: /home, usage: 83
timestamp: 2, mount_point: /var, usage: 50
timestamp: 3, mount_point: /home, usage: 84
timestamp: 3, mount_point: /var, usage: 52

How can I plot in a graph a line per mount_point representing the usage over time?

I used a query with metric=average:usage, group by=date histogram:timestamp and then by=terms:mount_point

I get as error “unable to graph data, switch to table view”. If I switch to table view, I see data grouped as expected, with 3 columns:
timestamp, mount_point, usage

How do I configure the graph to plot 1 line per mount point?

Thanks in advance.