I did a software upgrade, and with it came a new feature where when selecting a customer it queries for the sum of a few columns. This takes 7 seconds for the 'Cash Sale' customer - by far the most active customer. I'd like to see if it's possible to get it down a bit by changing settings.
To make things clear before we search for a solution. You wrote "by changing settings". Is it the only option? Can't you change the query in software? Can't you change database schema (add indexes etc)?
Query: explain analyse select sum(item_points),sum(disc_points) from invoice left join gltx on invoice.invoice_id = gltx.gltx_id where gltx.inactive_on is null and gltx.posted = 'Y' and gltx.customer_id = 'A0ZQ2gsACIsEKLI638ikyg'
Aside from other things, you know that LEFT join here is useless? - planner should collapse it to normal join but I'd check.