There are lots of guides out there to the basics of execution plans, but a lot are quite scarce on the details - how to interpret particular values, what they really mean, and where the pitfalls are.

We’ve spent a lot of time over the last 18 months learning, clarifying, and downright misinterpreting how each of these fields work — and there’s still further for us to go on that.

But we have come a long way, and I’d like to share the guide that I wish had existed when we started out — a glossary of the most common fields you’ll see on the operations in a query plan, and a detailed description of what each one means.

source: L