count_all_results() - is it optimized?

Well, it requires discipline to maintain your codebase in a portable state, and to be honest it's not worth it just for a potential switch. The actual benefits come if you're developing an app that you would distribute for others to install (like a CMS, for example), and they then have the choice of which database platform to use.

That's something interesting to think about, being that I never seem to have a need for portability.

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