NotFoundError performance

[ronag]

Creating an Error for "NotFound" instead of just returning null has a significant performance overhead. Creating Error objects are expensive.

Could we have a mode flag where we can avoid this?

[ralphtheninja]

Is this a real issue somewhere?

[vweevers]

Some time later I want to remove the (IMO usually unhelpful) error and return undefined instead. Per Level/community#76.

@ronag For the short term, I'd say pull requests to make this behavior opt-in are welcome, but it does depend on which modules you're using. You'll also have to touch any implementation of abstract-leveldown that you're using, because levelup merely wraps the errors. If this involves too many modules, I'm reluctant to accept PRs, because I want to wind down the maintenance of these, in favor of abstract-level.

[vweevers]

Quick and dirty benchmark of error (!undef) vs undefined:

[vweevers]

Level/abstract-level#49