4 ms·
Even if you have tons of RAM and the data IS there, performance is still disasterous if you have to perform seven, eight or nine digit logical reads. (millions
by jve 10y ago
Even if you have tons of RAM and the data IS there, performance is still disasterous if you have to perform seven, eight or nine digit logical reads. (millions or billions). Happens when SQL Server assumes it will use loop join because it thought there is only 1 row to join. Oops.
- protomyth 10y agoOh yeah, memory fails aren't the only cause, but they do tend to hit you very quickly. Nothing like doing production patches because you went from comfortably able to get done in the time period needed to "won't finish until next week". I can just see the developer face when seeing the loop join where it shouldn't be. Almost as bad as seeing FSM (full sort merge) on Ingress or full table scan on ASE or SQL Server. That's really why I recommend SQL writers really study the plan generated. Its the closest thing to studying assembly to teach what the optimizer is thinking. I still think the old Ingress plan viewer was pretty neat.