Erik Darling continues a series with two more posts. First up is sorting lookups:
Most people see a lookup and think “add a covering index”, regardless of any further details. Then there they go, adding an index with 40 included columns to solve something that isn’t a problem.
You’ve got a bright future in government, kiddo.
In today’s post, we’re going to look at a few different things that might be going on with a lookup on the inside.
One sort of interesting point about prefetching is that it’s sensitive to parameter sniffing. Perhaps someday we’ll get Adaptive Prefetching.
Until then, let’s marvel at at this underappreciated feature.
Check out both posts and prepare to be illuminated.