[fwip]

Other user here: Confession - I don't actually know what, if anything, the colors mean in a flamegraph. They seem random to me.

The way I'd personally hone in on Record::hasVariable is that it's a relatively-simple sounding function (from the name) that is taking a large portion of the X-axis. Starting at the bottom, I'd go "main -> editInOrder -> relateEdits -> countPeopleMatching -> getSourceDataAsLong -> hasVariable." Then I'd be like "we really spend 47% of our time in this simple-sounding function? What's it doing?"

Basically, I look for the functions that have an outsized complexity/time ratio. A function with a simple task is usually easier to optimize, and a function that only runs for 2% of your program isn't worth spending the time to optimize.