perf(db): Avoid double querying

[ChristophWurst]

1. If you check for existence, then fetch a prop -> fetch the prop directly
2. If you check for existence, then delete -> delete directly

I have not tested these changes.

[blizzz]

Did not test yet, would like to throw working integration tests at it, needs #837

[blizzz]

now tested

[blizzz]

@ChristophWurst do you fance a backport to cover NC 27 (and actually down to 25)?