Developers need control of their tools in the 0.1% case. When you are dealing with complex systems, you will start running into that 0.1%. Either due to a poo

Developers need control of their tools in the 0.1% case. When you are dealing with complex systems, you will start running into that 0.1%. Either due to a poorly designed scheme, legacy cruft, or unexpected growth. When things get hairy in other languages, sometimes it make sense to bypass the built in controls. Go around the system libraries, implement your own, or even drop into assembly. The same should be true of a query plan. Yes, your query planner (compiler) is going to get things right 99.9% of the time, but man when it gets it wrong, it's worth it to have tools to deal with the other 0.1%.