The optimizer has options.
Not every option is optimal.
Optimistic query tuners hope that the optimizer will make optimal choices.
Often, the optimizer will stick an optional operator in a plan that just doesn’t belong.
Sorts, Spools, Lookups, Tops, Aggregates, and Bitmaps can all end up where they don’t belong.
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Joe Obbish and Erik Darling will show you when the optimizer’s optics might require a trip to the optometrist.